Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

ANIMAL RENAL SYSTEMS


Metabolism generated waste that are actually toxic to the cell and must be excreted
...
1




















The difference in concentration of solutes on the two sides of the membrane creates osmotic
pressure that drives the movement of water
...
The higher the solute concentration, the
higher the osmotic pressure, and the greater tendency of water to move into the solution
...

To regulate water and solute levels, the cell controls the solute concentration of the inside of
the cell relative to the outside of the cell b/c water follows solutes across semipermeable cell
membranes
...
electrolytes
...
In contrast, freshwater animals lose electrolytes through diffusion across
their gills and skin into the hypotonic environment
...
Requires animals to avoid excess water uptake into their tissues and
control the loss of electrolytes from their body
...
, animals must avoid excessive
uptake of electrolytes and loss of water
...
Often
though, expend energy to regulate the concentrations of particular ions and other solutes that
are imp
...
Some marine vertebrates like sharks that are osmoconformers
match seawater’s solute concentration by maintaining a high internal concentration of a
compound called urea(waste product of protein metabolism that most animals secrete)
*isotonic; not net water movement
...
Expend energy pumping ions across membrane in order to regulate water
movement
...

Bony fish (marine vertebrates) and all freshwater/terrestrial organisms = osmoregulators
...
In marine bony
fishes, specialized cells called chloride cells counter the ingestion of excess electrolytes by
pumping chloride ions (na ions follow this gradient) out into the seawater
...

Freshwater fish do not drink water; they take up water at gills
...

Saltwater fish drinks water but produces small volumes of concentrated urine
...
They have high tissue osmolarity because of urea retention
...


41
...
Most multicellular animals have evolved specialized organs, such as the kidney, to
isolate, store, and eliminate toxic wastes
...

When proteins and nucleic acids are broken down by metabolism, one of the byproducts is
ammonia (nitrogenous waste) = very toxic
...
If on land  converted to less toxic urea (produced in the liver and then
transported to kidney by the blood where it is eliminated
...
Birds , reptiles, etc have an even less toxic form = uric acid
(insoluble so does not exert osmotic pressure and is eliminated with minimal water loss)
Animals filter or secrete wastes out of the blood along with water, electrolytes, and even
essential nutrients, but then reabsorb the nutrients they need, excreting the waster and enough
water to maintain balance
...
The filtered
fluid(filtrate) contains waste products along with water, electrolytes, and other solutes which
drain into excretory tubules that connect to the outside
...
(can be active/passive)
3rd step= secretion of additional toxic compounds and excess ion- involves eliminating
substances that were not filtered from the blood earlier
...
Paired
vertebrate kidneys receive blood supply from the heart by renal arteries that branch from the
aorta
...

Driven by circulatory pressure wastes, water, electrolytes, small solutes move out of the
capillaries into extracellular space surrounded by a capsule
...
The collecting ducts converge on a larger tube =
ureter which brings urine from kidneys to bladder
...


41
...
As the filtrate passes through the collecting
ducts, water moves out into interstitial fluid by osmosis, leaving concentrated urine
...
The glomerulus is located
in cortex and feeds into renal tube that starts in the cortex, dips into medulla, then loops back










up to cortex
...

The glomerulus = tuft of capillaries with blood entering by afferent arteriole and leaving by
efferent arteriole
...
The cells that line capillaries have pores
called fenestrae
...

Renal tubule  proximal convoluted tubule, loop of Henle, distal convoluted tubule
...

LOOP OF HENLE  produces concentration gradient (higher solute concentration in medulla
than in cortex) the ascending portion is impermeable to water but actively transports
electrolytes out of filtrate
...
The filtrate has the same concentration leaving
as going in but produces gradient in outside fluid
...

DISTAL CONVULUTED TUBULE(cortex)  filtrate is hypotonic(less solutes) having lost
electrolytes with urea as main solute; other wastes enter (dilute)  collecting ducts which
allows water to be reabsorbed because of gradient
ADH hormone controls water permeability of collecting ducts
...
Absence = impermeable making urine dilute
...
1 The Evolutionary History of Reproduction
A
...
the production of genetically identical cells or individuals called clones -->
asexual reproduction
...
Prokaryotes
can increase genetic variation, however
...

- Eukaryotes : mitosis
- budding (fungi, plants, and some animals) : a bud, or protrusion, forms on an
organism and eventually breaks off to form a new organism that is smaller than
the parent
...

- parthenogenesis - "virgin birth" Females produce eggs that aren't fertilized by
males but divide by mitosis and develop into new individuals
...
combining a complete set of genetic information from two individuals to make a
new genetically unique individual --> sexual reproduction

- two basic biological processes - meiosis and fertilization
...

- Many species produce two types of gametes that differ in shape and size
...

- Fertilization = fusion of gametes resulting in a zygote
...
Most organisms that reproduce asexually are also capable of reproducing sexually
...

C
...
)
D
...
Many organisms reproduce asexually but most of these organisms reproduce sexually at least
some of the time
...
2 Movement onto Land and Reproductive Adaptations
A
...
Aquatic organisms like amphibians and fish release egg and
sperm directly into the water => external fertilization
B
...
--> strategies to increase the probability of fertilization : release large numbers of
gametes, male and female physically meet
...
Internal fertilization - fertilization takes place inside the body of the female, an adaptation for
living on land
...

D
...
For internal fertilization, there is much more
control and therefore far few offspring are produces and time and energy is invested in caring
for the offspring
...
Organisms that produce large numbers of offspring w/o a lot of parental care= r strategists and
those that produce few offspring but put in a lot of parental investment are K-strategists
...
more crowding means more competition to survive which requires parental guidance
then
...
The eggs of animals with external fertilization -> yolk- provides all the nutrients that the
developing embryo needs until it hatches
...

G
...
For oviparous animals there is little embryonic dev
...
The movement onto land caused for changes --> amnion - a membrane surrounding a
fluid filled cavity that allows the embryo to develop in a watery environment
...
A 3rd membrane, a chorion, surrounds the
entire embryo along with its yolk and allantoic sac
...
These are all extraembryonic membranes - sheets of cells that extend out of the
embryo
...
In viviparous animals, the embryo develops inside the mother
...

42
...

Male
A
...
Males produce a lot of sperm b/c of
(1) sperm competition (2) female reproductive tract is hostile to sperm so many sperm are need
to ensure that at least one makes it to the egg
...
Sperm are haploid cells
...
The head is surrounded by a specialized organelle, the acrosome, that
contains enzymes that are used by sperm to transverse the outer coating of the egg
...

C
...
This location is
critical for the production of sperm, which require cooler temperatures
...
This is where diploid cells
undergo meiosis to produce haploid sperm
...

D
...
This
is where the sperm are stored prior to ejaculation
...
The two ejaculatory
ducts merge at the urethra, just below the bladder
...
Along this path, there are several exocrine glands that produce components of semen, the fluid
that nourishes and sustains sperm as they travel in the male and then female reproductive
tracts
...
Two seminal
vesicles--> located at the junction of the vas deferens and the prostate gland, secrete a protein
and sugar rich fluid that provides energy for sperm motility
...

F
...
Consists of a shaft and a head
called the glans penis
...
Figure 42
...
12,42
...

Female
A
...
The oocyte is the largest cell in human body
...
There
are two fallopian tubes, one on each side
...
The uterus is a hollow organ with thick muscular walls that is
adapted to support the developing embryo if fertilization occurs and to deliver the baby
during birth
...
Under the
influence of hormones, the cervix produces different kinds of mucus capable of either
blocking or guiding sperm through cervix
...
The external genitalia of the female are collectively called the vulva
...
The labia
minora meets the clitoris, the female homolog of the glans penis
...
the male testes and female ovaries are part of endocrine system and therefore responds
to and secrete hormones
...
the hypothalamus releases gondotropin - releasing hormone
(GnRH), which stimulates the anterior pituitary gland to secrete luteinizing
hormone(LH) and follicle-stimulating hormone(FSH)
...
In response, the testes secrete the hormone testosterone and
the ovaries secrete the hormones estrogen and progesterone
...
In males, LH acts on cells in the testes called Leydig cells, which secrete testosterone
...
, and dev
...
of male secondary sexual
characteristics
...

D
...
At puberty, females begin a menstrual cycle, in which
oocytes mature and are released from the ovary under the influence of hormones
...
The menstrual cycle has 2 phases: follicular phase and luteal phase
...
As a result, several
oocytes begin to mature, but usually only one of these becomes completely mature and
the others die off
...

Estradiol in turn acts on the lining of the uterus, causing it to thicken
...
As a result in part of rising estradiol levels, there is a rapid increase followed by a sharp
decrease in the level of LH produced by the anterior pituitary gland
...
Ovulation marks the beginning of
the luteal phase
...
The corpus luteum is a temporary endocrine structure that secretes the
hormone progesterone, which maintains the thickened and vascularized uterine lining
...
The oocyte, meanwhile, is swept into the fallopian tube and travels to the uterus
...
The corpus luteum
continues to secrete progesterone, and is first maintained by LH and then by the
hormone human chorionic gonadotropin (hCG), which is released by the developing
embryo
...
High levels of estrogen
and progesterone during pregnancy also block ovulation because they suppress the
release of GnRH, FSH, and LH
...
If the oocyte is not fertilized, the corpus luteum degenerates, estrogen and
progesterone levels drop, and the uterine lining is shed
...
Menstrual cycles usually start occurring around
age 12 in the United States and continue until approximately age 45 to 55
...

I
...

Chapter 43 Animal Immune Systems

I
...
1 Innate Immunity
 The immune system consists of two parts : Table 43
...
Innate or natural immunity provides protection in a nonspecific manner against all kinds of
infection; it is an evolutionarily early form of immunity and does not depend on exposure to a
pathogen
...
Adaptive or acquired immunity is specific to a given pathogen; it “remembers” past infections and
subsequent encounters with the same pathogen generate a stronger response from the host;
unique to vertebrates
A
...
It has two layers, the outer epidermis and the inner dermis
...
The dermis consists of
connective tissue, hair follicles, blood and lymphatic vessels, and glands
...
Fig 43
...
Saliva and tears have enzymes that help protect and
the low pH as well as enzymes of the stomach protect as well
...

B
...
Fig 43
...
The engulfing of a
cell or particle by another cell = phagocytosis
...
It then extends its plasma membrane around it until it forms a
compartment
...
OR can
also trigger a respiratory burst, a process that generates reactive oxygen species and reactive
nitrogen species that have antimicrobial properties that damage pathogens
...
4
 Three types of phagocytic cell: macrophages, dendritic cells, and neutrophils
...
Dendritic cells have lond cellular projections and are part of the
natural defenses found in the skin or mucous membranes
...
Neutrophils are
abundant and often the first cells to respond to infection
...
Mast cells release histamine, an important contributor to allergic reactions
and inflammation
...

C
...
All cells have an
array of proteins and other molecules on their surfaces
...


 Toll Like Receptors (TLRs) are a family of transmembrane receptors present on phagocytes that
recognize and bind to molecules on the surface of microorganisms
...

Phagocytes also contribute to the immune response by sending a message to the rest of the
immune system by releasing chemical messengers called cytokines that recruit other immune cells
to the site of injury or infection
...
Inflammation
 That recruitment happens as part of a process called inflammation- physiological response of the
body to injury that removes the inciting agent and begins the healing process
...
It is characterized by four signs: redness, heat, swelling, pain
...
5 certain cells in the tissue, such as dendritic and mast cells, are activated and release
cytokines and other chemical messengers
...

 For example, histamine, released by mast cells and basophils, acts on blood vessels to cause
vasodilation which increases blood flow to the site of infection or injury(redness&heat)
...
Fluid leaks out of the blood vessel, carrying
white blood cells into the damaged tissue(swelling)
...
(Fig43
...
As it nears the site of infection, the phagocyte, encounters and
binds to cytokines it then changes shape and moves in b/w cells lining the blood vessel and into
the surrounding tissue
...
One of these proteins, C-reactive proteins or CRP, recognizes
and binds to molecules on the surface of some bacteria
...
The binding of molecule like CRP to a pathogen to facilitate uptake by a
phagocyte = opsonization
E
...
43
...
The system is activated when these proteins bind to molecules specific to
microorganisms or to antibodies
 Activation of the complement system has three effects
...
Lysis results when complement proteins form a membrane attack complex (MAC) that
makes holes in bacterial cells
...
Finally, activation of
the complement system leads to the production of activated proteins that attract other
components of the immune system
...

II
...
2 Adaptive Immunity: B Cells, Antibodies, and Humoral Immunity
 has two additional features not present in the innate immune system

1) the first is specificity: the adaptive immune system targets responses to a specific pathogens
2) The second is memory: the adaptive immune system remembers past infections and mounts a
stronger response on re-exposure
 Two types of cells are particularly important: B lymphocytes, or B cells and T lymphocytes or T cells
...
Tcells matures in the thymus
...

A
...
An antibody is a large protein that carries sugar molecules attached to some amino
acids(glycoprotein)
...
Such a molecule is an antigen, which
is a molecule that binds to and leads to the production of antibodies
...

 Antibodies can be found on the surface of B cells or free in the blood or tissues
...

 STRUCTURE the simplest antibody molecule is a Y-shaped protein made up of four polypeptide
chains—two identical light (L) chains and two identical heavy (H) chains
...
The light and heavy chains are further subdivided into variable (V)
and Constant (C) regions
...
Each of the diff
...

 Binding of antibodies to antigens is the first step in recognition and removal of microorganisms
...
These latter functions are handled by a different part
of the antibody from recognition
...
The letters “ab” stand for antigen binding and
“c” stands for crystallizing
...

B
...
As a group they
are called immunoglobulins (Ig)
...
There are also two types of light chains which occur in all 5 classes, but any given
antibody contains only one type of light chain
...
It is the Y shaped antibody
...
It is the only class that can cross the placenta
...
It also exists as a monomer on the surface of B
cells
...
IgD is found on the surface of B cells and helps initiate
inflammation
...






D
...



antigens
...

The five classes of antibody are called isotypes
...
Collectively, these antibodies recognize a great diversity of antigens, but each
individual antibody can recognize only one antigen or a few
...
Plasma or
effector cells secrete antibodies
...
Antibody specificity is achieved before any
exposure to the antigen
...
On re-exposure to the same antigen, secondary response – which is
quicker, stronger, and longer than the primary response; during this response the antibodies are
released by memory B cells
...
In addition the pool of memory B
cells is larger than the pool of naïve B cells for a given antigen
...

Vaccination
Genomic Rearrangement
Clonal selection requires a mechanism for producing a great diversity of antibodies
...

Many copies of each gene segment are present, each slightly different from the others
...
As a B cell
differentiate, different gene segments are joined in a process called genomic rearrangement that
produces a specific antibody
...
The DNA in this region undergoes recombination so that just one of each of these
segments makes part of a functional H chain gene and the intervening DNA is deleted
...

L chain genes also contain multiple copies of gene segments, except they do not have a D segment
so the VJ segment encodes the variable region and the C segment, the constant region
...
We generally think of DNA as a stable blueprint present in identical copies in all
of the cells in our bodies but B cells are an exception
...
A B
cell able to use both homologs would make two different antibodies but they can only make one
 so, once one allele undergoes genomic rearrangement the other allele is prevented from doing
so – B cells act as if they have a single allele for each antibody gene
...

43
...
They are sometimes also ineffective against
pathogens that take up residence inside a cell

 T cells do not secrete antibodies, they participate in cell mediated immunity, so named b/c cells,
not antibodies, recognize and act against pathogens
...
T cells
...
A mature T cell is characterized by
the presence of a T cell receptor(TCR) on the plasma membrane
...
They are always found on the surface of T cells
...
Helper T cells help other
cells of the immune system by secreting cytokines
...
Helper T cells also activate macrophages, cytotoxic T cells, and others
...

 These two types of T cells are distinguished by the presence of different glycoproteins on their
surface : CD4 on helper T cells and CD8 on cytotoxic T cells
...
TCRs
 Binding of TCR to an antigen triggers the T cell to divide into clones, resulting in a pool of T cells
that are each specific for a given antigen
...
TCRs are composed of two polypeptide
chains, not 4
...
The TCR does not recognize
free antigens like antibodies do
...

 Once activated, T cells divide and form helper and cytotoxic T cells
...
Like B cells, T cells can sometimes be activated too strongly – delayed
hypersensitivity reaction : poison ivy : initiated by helper T cells which release cytokines that attract
macrophages to the site of exposure
C
...
One of these signals is
an antigen
...
T cells interact only with antigens that are bound to
molecules of the MHC on the surface of host cells
...

It is composed of many genes with a high rate of polymorphism, meaning there is a lot of
variability
...
Class II genes are
expressed on the surface of macrophages, dendritic cells, and B cells
...

 Helper T cell activation: antigen enters immune system it may be recognized by an antibody
directly or be taken up by antigen presenting cells(macrophages, dendritic cells, and B cells) – take
up the antigen and return portions of it to the cell surface bound to MHC class II proteins
...

release cytokines that activate other parts of the immune system
...

D
...
Those that
recognize MHC molecules on epithelium cells are positively selected and cont
...
Those
that react too strongly to self antigens in association with MHC are negatively selected and
eliminated
...
Result is two-fold : First, T cells become
MHC restricted and second, they exhibit tolerance : they don’t respond to self antigens
 B cells are not MHC restricted but they do exhibit tolerance because they go through negative
selection
...

IV
...





Flu virus
Caused by RNA virus
The success of virus lies in its ability to spread easily; airborne
Also in its ability to evade the immune system; there are three major types of flu virus : A, B, C and
many different strains
...
It can bind only to cells that display a
complementary cell surface protein
...
If a single cell is infected by two different strains, the RNA strands can reassert
to generate a new strain
...
Tuberculosis
 Bacterium
 Affects lungs
...
Malaria
D
...
The parasite expresses just one of
these genes at a time and can change which one is expressed
Chapter 35 Animal Nervous System Notes
I
...
1 Nervous System Function and Evolution
 nervous system – a network of many interconnected nerve cells
...

A
...

- Sensory neurons receive and transmit information about an animal;s environment or its internal
physiological state
...

- Nervous system  homeostasis
- The ability to process information first evolved with the formation of ganglia  groups of nerve
cell bodies that process sensory information received from a local, nearby region, resulting in a
signal to motor neurons that control some physiological function = relay station/processing
points in nerve cell circuits
...
Nervous Systems range from simple to complex
- Fig
...
2
- The sponges are the only multicellular organisms that lack a nervous system
...
In these animals, the nerve cells are arranged like a net
...

A
...

-

C
...
Sense organs also developed in the head region
...
Paired ganglia and eyespot of the flatworm are located
at one end of its body, as are the brain and sense organs of the earthworm, squid, and insect
...
= adaptation for forward locomotion and predation
...
2 Neuron Structure
Neurons share a common organization
Fig 35
...

Dendrites receive signals from other nerve cells or in the case of sensory nerves, from
specialized sensory endings
...

At the junction of the cell body and its axon, the axon hillock, the signals are summed
...
An action potential is a brief electrical signal transmitted from the
cell body along one or more axon branches
...
The end of each axon forms a
swelling called the axon terminal which communicates with a neighboring cell through a
junction called a synapse
...
Molecules called neurotransmitters
convey the signal from the end of the axon to the post synaptic cell
...
The vesicles fuse with the axon’s membrane, releasing neurotransmitter molecules
into the synaptic cleft
...
The binding to these receptors causes a change in the
electrical charge across the membrane of the receiving postsynaptic cell, continuing the signal
...

Neurons differ in size and shape
Diversity in size and shape
...
The position of the cell body can also vary in different neurons
...

Information arriving from many sources often converges on a smaller subset of neurons
...

Neurons are supported by other types of cell
Neurons in many body regions are supported by other types of cell that do not themselves
transmit electrical signals
...
The human brain has
more glial cells than neurons
...

Star shaped glial cells called astrocytes contribute to blood-brain barrier, a set of structural
adaptations of the blood vessels supplying the brain that prevent pathogens and toxic
compounds from entering it
...
Glial cells form multiple lipid rich
layers or sheaths, called myelin that wrap around axons
...


A
...











sensory and motor neurons and glial cells called oligodendrocytes insulate cells in the brain and
spinal cord
...
(Fig 35 8
...
3 Neuron Function
Neurons encode information by changes in their membrane voltage and transmit information in
the form of electrical signals
...
The resting membrane potential is said to be polarized(buildup of
negatively charged ions on the inside surface of the cell’s plasma membrane and positively
charged ions on the outside surface
...
35
...
The sodium potassium pump uses the energy of ATP to
move three Na+ ions outside the cell for every to K+ moved inside the cell  cell becomes less
positive
...
When a nerve cell is at rest, more K+ ion channels open, giving K+ greater
permeability compared with all other ions
...

It is the movement of potassium ions relative to other ions, particularly Na ions, that largely
determines the resting potential
Action potentials
When a nerve cell is excited, the inside becomes more positive – the increase in membrane
potential = depolarization
At the axon hillock, depolarization causes voltage gated sodium channels to open, allowing Na+
ions to enter the cell
...
Voltage gated sodium channels are closed at the resting membrane
potential but open in response to depolarization
...
9
If the excitatory signal is strong enough to depolarize the membrane to a voltage of 15mV above
the resting potential(-50mV) the nerve fires an action potential(rapid, short rise and fall in
membrane potential) at the axon hillock
...
When the threshold potential is exceeded, the nerve fires an action
potential in an all or nothing fashion(the magnitude of the action potential is always the same
and is independent of the strength of the stimulating input  spike to +40mV)
As the cell membrane crosses its threshold potential, voltage-gated Na+ channels suddenly open
, allowing Na+ ions to rush inside the cell
...


 Falling phase – voltage gated sodium channels close automatically after a brief period of time
...

 The voltage briefly falls below resting potential in hyperpolarization and then returns to the
resting potential as K channels close to restore the resting concentration of K and Na
...

 The period during which the inner membrane voltage falls below and then returns to resting
potential= refractory period – period where neuron cannot fire a 2nd action potential- results in
part because it takes time for Na channels to open again after they close
...

C
...

Fig 35
...
The inward sodium current depolarizes the membrane above threshold, triggering the
opening of nearby voltage gated Na+ channels still farther along the axon The depolarization
spreads down the axon
...

 Action potentials are self-propagating only in one direction
...

 The myelin sheath spreads the charge from a local action potential over a much greater distance
along the axon’s length
...
Votage gated Na and K channels are concentrated at these nodes action
potentials in myelinated axons “jump” from node to node = saltatory propagation- increases
the speed of signal transmission
...
Neurons communicate at synapses
 There are two types : electrical and chemical
 Chemical synapses: signals conveyed are neurotransmitters which are contained in small
vesicles in axon terminal
...
Because of higher concentration outside the cell, calcium ions diffuse into the axon
terminal causing the vesicle to fuse with the presynaptic membrane and release the
neurotransmitters into synaptic cleft by exocytosis
 Fig 35
...
This is short
lasting as neurotransmitters become unbound shortly after binding
E
...

 A neurotransmitter binds to receptors that trigger the opening or closing of ligand gated ion
channels in the postsynaptic membrane
...
Clions then diffuse into the cell as K+ ions flow out causing the membrane potential to become
hyperpolarized

 Each type of nerve cell can release only one type of neurotransmitter but postsynaptic
membranes have multiple receptors for different kinds of neurotransmitters
 The postsynaptic cell sums the EPSPs and IPSPs at axon hillock  when summed over time, the
frequency of synaptic stimuli determines whether the postsynaptic cell fires and action potential
–temporal summation
...
Sometimes, excitatory and inhibitory signals may cancel each other out
...
15
IV
...
Peripheral and Central components
 Fig 35
...
In general, neuron cell
bodies are grouped compactly together in sensory organs, ganglia, and a main nerve cord that
extends from the brain
...

 Sensory and motor nerves make up the peripheral nervous system
...
The brain, spinal cord and centralized ganglia make up the
central nervous system
 Specialized sensory organs transmit information from the animal’s periphery by afferent
neurons, which send information to the CNS
...
The peripheral nervous system also
includes interneurons
...

 In humans, the peripheral nervous system into left and right sets of cranial nerves located
within the head and spinal nerves running from the spinal cord to the periphery
...
Spinal nerves exit from the spinal cord to the body;
these nerves receive sensory information from receptors in nearby body regions and carry
motor signals from the spinal cord back to those regions
...
Voluntary v Involuntary
 Conscious reactions are under control of the voluntary component of the nervous system, and
unconscious ones are under the control of the involuntary component
...
The somatic nervous system is made up of sensory
neurons that respond to external stimuli and motor neurons that synapse with voluntary
muscles
...

 The autonomic nervous system is divided into two parts : sympathetic division(fight or flight)
and parasympathetic division(rest and digest)
...

C
...

Ex
...
A drop in temperature
signals the hypothalamus(sensor) to activate the somatic nervous system(effector) to induce
shivering or the peripheral nervous system to constrict blood vessels to produce heat or prevent
heat loss (response) Fig 35
...
Reflex Circuits
 Fast responses are made possible by simple reflex circuits that bypass the brain by directly
connecting sensory neurons with motor neurons and are common in both somatic and
autonomic nervous systems
 Knee jerk reflex- includes only a single synapse b/w two neurons- a sensory and a motor
 Fig 35
...
The receptors are part of a sensory
nerve with dendrites that extend from the stretch receptors to cell bodies in ganglia beside the
spinal cord
...
In response to a stretch, a signal is
sent from the stretch receptor through the dendrite and cell body, to the axon
...
This reflex arc does not include an interneuron; only two
neurons and one synapse
...
Reciprocal inhibition of opposing sets of muscles occurs in the spinal cord
...
This inhibitory reflex pathway = two synapses
Circulatory System
 Closed Circulatory System of animals are made up of a set of internal vessels and a pump – the
heart – to transport the blood to different regions of the body
...
If blood flows to quickly then there
would not be enough time to exchange gases
...

o Muscles assist circulation and some invertebrates have simple hearts
 A closed circulatory system delivers O2 at high rates to exercising tissues while open circulatory
systems operate under low pressure and have limited transport capacity(less active)
...

of circulatory system
...

 In order to pump blood through set of closed interconnected vessels, a muscular heart is
needed to produce sufficient pressure to overcome the flow resistance of the vessels
...
The pressure developed by heart when
it contracts establishes a rate of blood flow that is governed by P/R
...
























The resistance to flow is determined in part by fluid’s viscosity and the vessel’s length
...
The vessel’s radius  Resistance is proportional to 1/r^4,
which means if a vessel’s radius is halved, its resistance increases 16 times
...

Veins are the large, low pressure vessels that return blood to the heart
...
The reverse organization is found on the return side 
capillaries drain into vessels of progressively larger diameter called venules and the venules
drain into larger veins that return blood to the heart
...

enables the blood to flow more slowly in smaller vessels so gases can diffuse
...
The reduction in diameter increases the
resistance to flow and thereby reduces the rate of blood flow
...
When active, as the rate of cellular
respiration in these cells increases, they begin releasing more CO2
...

A strong pulse of flow pushes against arterial walls every second as the heart beats to pump
blood which causes momentary expansion of the arteries
...

Collagen fibers=strong and resist expansion of arterial wall during pulses
...

Blood collected from local capillary networks returns to the heart through progressively larger
veins that ultimately drain into the two largest veins : venae cavae  drain blood from the head
and body into the heart
...
Consequently, veins are thin walled
and have little smooth muscle of elastic tissue
...

Veins have one way valves that help prevent blood from pooling
...

Water, certain ions, and other small molecules, but not proteins, move from capillaries into the
surrounding interstitial fluid (the extracellular fluid surrounding vessels) by filtration, forced by
blood pressure
...
At the same











time, blood pressure decreases b/c the flow resistance imposed by capillaries
...

(fig 39
...
The fluid that enters the lymphatic system is called the
lymph
...

lymphatic vessels have one way valves that assist the return of lymph to the circulatory system
...

Dehydrated or lost blood  drop in blood pressure  the posterior pituitary gland releases
ADH(vasopressin/antidiuretic hormone)  ADH causes arteries to contract, increasing their
resistance to blood flow  higher resistance elevated blood pressure
Less stressful conditions  blood is continually being adjusted (The autonomic nervous system)
 in blood pressure drops, animals reduce the supply of blood to limbs by constricting arteries
that supply them  this helps maintain blood pressure to the heart, brain, and kidneys
...
When blood pressure is high, these sympathetic neurons are inhibited and
smooth muscles relax
...


THE HEART









Complex hearts have chambers that expand and fill with deoxygenated blood returning from the
animal’s tissues
...

Vertebrates have a single heart with at least two chambers, one for receiving blood and the
other for pumping blood to the body during each cycle
...

Fish – deoxygenated blood is pumped to gills to gain oxygen before flowing to body and then
returning to the heart  limits rate of blood flow to tissues due to resistance in gills
Bird and mammals evolved a separate pulmonary circulation to the lungs and systemic
circulation to the rest of the body – made possible by 4 chambered heart  increases supply of
oxygenated blood to tissues and increases uptake of o2 at the gas exchange surface
...
Deoxygenated blood returning
from tissues enters the atrium, which fills and then contracts to move the blood into a thicker
walled ventricle
...
Oxygenated blood travels to tissues through a large artery
called the aorta
...
This loss
limits flow of oxygenated blood to body tissues












AMPHIBIANS AND REPTILES  land vertebrates evolved hearts that separated the circulation of
deoxygenated blood pumped to their gas exchange organs from circulation of oxygenated blood
delivers to tissues efficient and greater activity
...
This arrangement
partially separates the pulmonary and systemic circulations, so freshly oxygenated blood can be
pumped under higher pressure to the body than fishes
...

REPTILES have three chambers but their single ventricle has internal ridges to improve
separation of deoxy and oxy blood
...

Following the pattern established in amphibians and reptiles, deoxygenated blood enters the
right atrium from the venae cavae and, when the atrium contracts, moves through an
atrioventricular (AV) valve into the right ventricle (Fig
...
21)
...
The
walls of the right ventricle are thinner than those of the left ventricle, and its weaker
contractions eject blood at a lower pressure
...
The
oxygenated blood returns from the lungs through the pulmonary veins and enters the left
atrium of the heart
...
The thick muscular walls of the left ventricle eject
the blood under high pressure to the body
...
The contraction of the two atria followed by contraction of the two
ventricles makes up the cardiac cycle (Fig
...
22)
...
Systole is the contraction of the ventricles, and diastole is the relaxation of the
ventricles
...

the cardiac muscle cells that make up the walls of the atria and ventricles must contract in a
coordinated fashion
...

First, specialized cardiac muscle cells can generate action potentials on their own, independently
of the nervous system
...
The specialized cardiac muscle cells capable of









generating action potentials independently function as a pacemaker that causes the heart to
beat with a basic rhythm
...
39
...

feature of pacemaker cells is that their resting membrane potential gradually becomes less
negative on its own until it reaches threshold and the cell fires an action potential
...
When
the cell reaches threshold, voltage-gated calcium ions open, causing more rapid depolarization
...

The heartbeat is initiated at the sinoatrial node, located at the junction of the vena cava and
right atrium (Fig
...
23) fire an action potential, their depolarization spreads electrically
throughout the right and left atria, causing them to contract in unison not ventricles
...
Activation of the AV node transmits the action potential to the
ventricles
...
1 Delivery of Oxygen and Elimination of Carbon Dioxide
 the transport of O2 and CO2 b/w an animal and its environment is referred to as gas exchange
and is fundamental to all eukaryotic animals, as well as photosynthetic plants
...
Diffusion
 Single celled organisms and simple animals and plants exchange gases by diffusion
...

 the rate of diffusion is directly proportional to the surface area over which exchange occurs and
to the concentration difference and inversely proportional to the distance over which the
molecules move
 diffusion is ineffective over distances exceeding
...
Pressure is measured in mmHg
...
3%)
...
For O2 to
diffuse from the air into cells, the partial pressure of O2 inside the cells must be lower that in
the atmosphere
...
Bulk Flow
 Larger, more complex animals transport O2 and CO2 longer distances to cells within their body
...

 bulk flow = the physical movement of fluid, and the gases and compounds carried by the fluid
...
It
occurs in two steps
...
The 2nd step = circulation --> the
movement of a specialized body fluid that carries oxygen of carbon dioxide
...
This fluid delivers oxygen to cells
within diff
...




Ventilation and circulation each require a pump to produce a pressure(P) that drives flow (Q)
against the resistance (R) to flow
...
The longer the network of vessels and
the narrower the vessels themselves, the greater the vessels' resistance to the fluid moving
through them
...
3 --> (1) to deliver O2 to the mitochondria within their cells, animals move
fresh air or water past their respiratory exchange surface in the process of ventilation
...
(3)
Following diffusion into the blood, O2 is transported by the circulation (bulk flow) to the tissues
maximizing the concentration of O2 outside of cells
...

 to remove CO2, same process but in reverse
...

39
...
39
...
In contrast, many terrestrial animals, such
as reptiles, birds, and mammals, have internal lungs for gas exchange (Fig
...
4b)
...

 Recall that diffusion is much slower than the bulk flow of ventilation --> So, the gas exchange
surface must have a large surface area and be extremely thin
...

A
...

 consist of a series of gill arches located on either side of the animal behind the mouth cavity
and, in bony fishes, beneath the operculum
...
Numerous lamellae, thin sheetlike structures, are
evenly but tightly spaced along the length of each gill filament and extend upward from the
filament’s surface
...
The lamellae are composed of flattened epithelial cells and are extremely thin, so short
distance b/w water and blood
...
5)
 lamellae are oriented so blood flowing through them in a capillary network moves in a direction
opposite to the flow of water --> countercurrent exchange : the two essentially exchange
properties (fig 39
...
Insects
 evolution to life on land --> 1
...
2
...
3
...
Two step process --> First, air enters an insect through
openings, called spiracles, along either side of its abdomen
...
Second, diffusion occurs at the cell: O2 supplied by the fine airways diffuses into the cells,
and CO2 diffuses out and is eliminated through the insect’s tracheae
...
Terrestrial Vertebrates



the lungs of most land vertebrates inflate and deflate to move fresh air with O2 into the lungs
and expire stale air with CO2 out of the lungs
...
In tidal respiration, air is drawn into the lungs during
inhalation and then moved out during exhalation (Fig
...
7a)
...

The expansion of the lungs causes the air pressure inside lungs to become lower than the air
pressure outside the lungs
...

 exhalation is passively driven by elastic recoil of tissues that were previously stretched during
inhalation
...
The resulting positive pressure forces air out of
the lungs
...
39
...
Exhalation occurs passively by elastic recoil of the
lungs and chest wall
...
helps to produce larger changes in the volume of the thoracic cavity,
increasing the negative pressure that draws air into the lungs during inhalation and assisting
elastic recoil of the lungs and chest wall to pump air out of the lungs during exhalation
...
5 liter of air every cycle (Fig
...
7b)
...
With a breathing frequency of 12 breaths per minute,
the ventilation rate (breathing frequency × tidal volume) is 6 liters per minute
...

 The fresh air inhaled during tidal breathing mixes with O2-depleted stale air that remains in the
airways after exhalation
...
Consequently,
the fraction of O2 that can be extracted is lower than the fraction that can be extracted by the
countercurrent flow of fish gills
...

D
...
Air
is taken in through the mouth and nasal passages, and then passes through the larynx, within
which the vocal cords are located
...
39
...
The trachea divides into two airways, called primary bronchi, one of which
supplies each lung
...
This
branching continues until the terminal bronchioles have a diameter of less than 1 mm
...
(human lungs consist of300 to 500 million alveoli with a combined surface area as large as
a tennis court—about 100 m2)
 Small blood vessels, called pulmonary capillaries, supply the alveolar wall
...
39
...
As a result, the diffusion distance from the alveolus into the capillary is extremely
short
 moisture helps move O2 molecules from the air into solution and thus diffuse across the alveolar
wall
...
Other alveolar epithelial cells produce a compound called surfactant, which acts like
soap to reduce the surface tension of the fluid film-allows the lungs to be inflated easily
 Mucus-secreting cells line all the airways of the lung not only to keep them moist but also to
trap and remove foreign particles and microorganisms that an animal may breathe in with air
...
Bird Lungs
 The lungs of birds are unique in that they are rigid and do not inflate and deflate
...
Instead, they benefit from unidirectional airflow
that enhances gas exchange by maintaining larger concentration gradients for diffusion
...
Air is pumped through
these air sacs in a bellows-like action (Fig
...
9)
...
As the sacs are then compressed by surrounding
muscles acting on the skeleton, air is pumped through the bird’s rigid lungs
...
The air capillaries direct the air so that it moves crosscurrent (at 90°) to the
path of blood flow through the walls of the air capillaries
...

After fresh air is inhaled into the posterior air sacs, the stale air in the anterior air sacs is exhaled
out of the bird’s trachea and mouth
...
Voluntary and Involuntary Mechanisms control breathing
 homeostasis often depends on sensors that monitor the levels of the chemical being regulated
...
39
...
The carotid bodies sense O2
and proton (H+) concentrations of the blood going to the brain, and the aortic bodies monitor
their levels in blood moving to the body
...
The most important factor in the control of breathing is the amount
of CO2 in the blood
...

 Breathing control allows for - Sound --> produced by voluntarily adjusting the magnitude and
rate of airflow over the vocal cords of mammals
39
...

 Blood plasma is the fluid portion of blood without the cells
...
How much O2 goes into solution at a given partial pressure is a
measure of its solubility
...
2 ml
of O2 can be carried in 100 ml of blood
...
By binding O2 and removing it from solution, hemoglobin
increases the amount of O2 in the blood a hundredfold
...
Most of the CO2
(about 95%) is converted to carbonic acid, which dissociates to form bicarbonate ions (HCO3−)
and protons (Chapter 6)
...

A
...
It is a globular protein that
consists of four polypeptide units (Fig
...
11)
...
After O2 diffuses into the blood, it
diffuses into the red blood cells and binds to the heme groups in hemoglobin
...
The removal of O2 from the plasma, in
turn, keeps the pO2 of the plasma below that of the lung alveolus, so O2 continues to diffuse
from the lungs into the blood
...
39
...
As blood pO2 increases,
hemoglobin saturation rises slowly at first, then more steeply, and then more slowly again until
it levels out
...
”
 explained as a result of changes in the ability of hemoglobin to bind O2 (a property called its
binding affinity) at different O2 partial pressures
...
The increase in binding affinity with additional
binding of O2 is called cooperative binding, and it gives the O2 dissociation curve for hemoglobin
its sigmoidal shape
...
As active cells consume O2, they reduce
the local pO2 of the cell and surrounding tissues to 40 mmHg or less
...
39
...
The steepness of the
slope indicates that for a relatively small decrease in pO2, large amounts of O2 can be released
from hemoglobin to diffuse into the cell
...
Myoglobin
 Myoglobin is a specialized O2 carrier within the cells of vertebrate muscle
...

 the O2 dissociation curve for myoglobin has a different shape from that of hemoglobin (Fig
...
12b)
...
As a result, hemoglobin releases O2 to exercising
muscles
...

 Red muscle cells store large amounts of myoglobin
...

C
...
Rather, they exchange gases across the placenta
...

When a decrease in pH occurs during exercise, the affinity of hemoglobin for O2 decreases,
resulting in a rightward shift in the O2 dissociation curve (Fig
...
14b) --> called the Bohr effect
...
Because hemoglobin’s affinity for
O2 is reduced, more O2 is released and supplied to the cells for aerobic ATP synthesis
...
Thus, when released from respiring tissues, CO2 promotes increased O2 delivery
both through its direct effect on hemoglobin and its contribution to a decrease in blood pH by
the Bohr effect

---