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

---

OCR A LEVEL BIOLOGY NEURONAL
COMMUNICATION TEST AND LATEST
RELEASED
...
- CorreCt Answers -Myelin-secreting
membrane surrounds the axon multiple times, simultaneously blocking
Na+/K+ channels - forcing AP to 'jump'
...
- CorreCt Answers -2/3rds of
peripheral neurons, each cell houses several axons, providing protection
...
They
are transducers

Transducer - CorreCt Answers -Something which converts 1 form of energy
into another
...
(E
...
rods and cones)

Thermoreceptors - CorreCt Answers -Detect heat energy and convert it to
electrical energy
...
g
...


Chemoreceptors - CorreCt Answers -Convert chemical energy to electrical
energy (e
...
olfactory sensors in the nose)

Mechanoreceptors - CorreCt Answers -Convert energy from
movement/stretch/pressure and transfer it to electrical energy
...
g
...
Some
non-gated K+ channels are always open in the membrane, so some K+
leaves via facilitated diffusion, so is even more + on outside and - on inside
...
It is polarised
...


Resting potential (for parcinian corpuscle) - CorreCt Answers --70mV

Parcinian corpuscle when stimulated - CorreCt Answers -When pressure is
applied it causes the connective tissue to stretch/deform, which causes
stretch-mediated Na+ channels to open so Na+ enters through facilitated
diffusion into the nerve ending, so it becomes less negative on inside
...


What happens when the parcinian corpuscle is stimulated with more
pressure? - CorreCt Answers -More stretch-mediated Na+ channels open,
even more Na+ enters
...
When stimulus happens, voltage gated Na+ channels open & Na+
enters neuron
...
Then voltage-gated
Na+ close & K+ channels open, K+ leaves so more + on outside & - on
inside, K+ take long time to close, so enough leaves that membrane is
hyperpolarised to less than -70mV, Na+/K+ pump then begins again to
return it back to resting potential (another AP cannot be fired during this,
known as "refractory period
...
If enough
Na+ diffuses, it reaches -55mV causing Na+ channels to open, causing that
section of the neuron to be depolarised/transmitting an AP
...
Causing waves of excitation across it, taking
a lot of time
...
If enough Na+ diffuses to the next node, it reaches 55mV, causing voltage-gated channels to open, causing depolarisation and
the action potential to 'jump' to the next node
...


What factors other than myelin affect AP speed? - CorreCt Answers -Axon
diameter (less resistance) and temperature (ions move faster, up to a point
until proteins denature)

What type of feedback to APs use? - CorreCt Answers -Positive feedback

Can Na+ diffuse backward? - CorreCt Answers -No, as the concentration
behind the ions is higher than in front - only 1 way AP
...
1st
discovered
...
Ca2+ enters presynaptic bulb via facilitated
diffusion
...
Ach diffuses across
and binds to nicotine Ach receptors, if 2 bind, Na+ channels in receptor
neuron open, if enough Na+ enters, it reaches the threshold potential and
an AP is generated
...
This requires ATP
...


How do synapses ensure one-way communication? - CorreCt Answers -Vesicles/Ach/voltage-gated Ca2+ channels are only on the presynaptic
neuron

AchE/nicotinic Ach receptors are only on the postsynaptic neuron

Neurotransmitters are either - CorreCt Answers -Excitatory or inhibitory

Excitatory neurotransmitters - CorreCt Answers -(E
...
ACh), cause Na+
channels to open and Na+ to enter the postsynaptic neuron by facilitated
diffusion, causing it to be more positive and increasing the chance of an AP

Inhibitory neurotransmitters - CorreCt Answers -(e
...
GABA), cause Clchannels to open, causing Cl- to enter the postsynaptic neuron via
facilitated diffusion, causing it to be more negative and decreasing the
chance of an AP

Temporal summation - CorreCt Answers -When 1 AP isn't enough to cause
an AP in postsynapse, so neurotransmitters are rapidly fired into the
synapse to increase the chances of an AP
...
Each releases neurotransmitters
which, when built up to a high enough level, trigger an AP in the next
neuron
...

The sum of excitatory-inhibitory = whether AP happens
...
They are meant to protect
the organism, ensure survival and prevent injury
...
g
...


Reflex arc - CorreCt Answers -Pathway of neurons in a reflex; a receptor
detects a stimulus, passes the AP onto a sensory neuron, which passes the
AP onto a relay neuron in the spinal cord, which passes the AP to a motor
neuron, which passes the AP onto an effector
...


Description on knee-jerk reflex - CorreCt Answers -Stimulus causes sudden
stretch, stretch is detected by muscle spindles/stretch receptors, triggering
an AP in the sensory neuron which connects through a synapse to a motor
neuron, which connects to quadriceps and causes the to contract, making
the leg straighten
...


Spinal cord made up of - CorreCt Answers -Outer region - Long, myelinated
neurons which carry APs up and down the body

Inner region - Mostly relay neurons

PNS made up of - CorreCt Answers -Sensory neurons and motor neurons,
constructing the somatic nervous system and the autonomic nervous
system

Somatic Nervous System - CorreCt Answers -Used in voluntary actions,
effectors are usually skeletal muscle, usually myelinated as they're also used

in reflexes which are quick, usually there's only 1 neuron between the CNS
and the effector
...

Normally unmyelinated (no need to be quick)
...


Cerebellum - CorreCt Answers -Control and coordination of movement;
fine motor control, posture and balance
...
g
...
g
...
Main controller of
autonomic NS and also works with pituitary gland in the endocrine system
...


What does TSH do - CorreCt Answers -Stimulates the thyroid to release
thyroxine, which increases BMR and sensitivity of cells to adrenaline

What does ACTH do? - CorreCt Answers -Triggers the adrenal cortex to
release corticoid hormones, e
...
cortisol, which triggers glycogenolysis in
liver and muscles and gluconeogenesis in liker and kidneys
...

- Stimulates smooth muscles to constrict in blood vessels in skin and gut, as
well as in erector pilli muscles
...

- Stimulates glycogenolysis in skeletal muscle
...


Why doesn't adrenaline diffuse across the membrane - CorreCt Answers It's a non-steroid hormone

CRH - CorreCt Answers -Corticotropin-releasing hormone

TRH - CorreCt Answers -Thyrotropin-releasing hormone

ACTH - CorreCt Answers -Adrenocorticotrophic hormone

TSH - CorreCt Answers -Thyroid stimulating hormone

Pros of studying the brain - CorreCt Answers -Increases understanding of
the brain, helping us treat disorders involving it
...


Types of muscle - CorreCt Answers -Skeletal, cardiac, smooth

Skeletal muscle - CorreCt Answers -- Striated and voluntary
- Only contract in one way
- Contract rapidly
- Usually in antagonistic pairs
- Made of muscle fibres
- Short contraction time

Cardiac muscle - CorreCt Answers -- Found in heart
- Myogenic
- Specialised
- Striated and involuntary
- Cells are branched and can interconnect
- Intermediate speed and length
- Made of cardiomyocytes

Smooth muscle - CorreCt Answers -- non-striated and involuntary
- no arrangement
- slow and long contraction time

Skeletal muscle appearance - CorreCt Answers -tubular, multi-nucleated
and striated

Smooth muscle appearance - CorreCt Answers -No cross striations, spindle
shaped, and uni-nucleated cells

Cardiac muscle appearance - CorreCt Answers -fainter striations, branched,
one nucleus,

Where is smooth muscle found? - CorreCt Answers -- Arterioles
(vasodialation)
- Trachea/bronchi (relaxes during exercise)
- In digestive tract (peristalsis)
- In eye (controls pupil dilation)

Muscle fibre structure - CorreCt Answers -- Enclosed by a plasma
membrane called sarcolemma
- Contains many nuclei
- Longer than most cells
- Cytoplasm known as sarcoplasm

Adaptations of muscle fibres - CorreCt Answers -- Parts of sarcolemma fold
inwards (known as t-tubules) to spread electronic impulses throughout it
...


Myosin in muscles - CorreCt Answers -Thicker filament, long rod-shaped
fibres with bulbous heads projecting to one side

Parts of myofibrils - CorreCt Answers -I-bands, A-bands, Z-line, M-line, Hzone
...
It is especially dark as myosin overlaps with actin (ALL
MYOSIN AND OVERLAPPING ACTIN)

Z-line - CorreCt Answers -Line found at the centre of each light band,
contains proteins holding 2 actin filaments together
...


Neuromuscular junction - CorreCt Answers -(MOTOR-END PLATES)
Connection between a motor neuron and a muscle fibre

What neurotransmitter do neuromuscular junctions use? - CorreCt
Answers -ACh, which is always excitatory and causes muscle contraction

Motor unit - CorreCt Answers -A motor neuron + all the muscle fibres it
connects to

All or none law in muscles - CorreCt Answers -Either all muscle fibres
contract or none contract

The number of motor neuron connections to muscle fibres can be - CorreCt
Answers -Only one (e
...
as in eye) or multiple (e
...
in quadriceps) allowing
for big, powerful movements
...
ACh diffuses across cleft + 2 binds to nicotinic
ACh receptors, causing Na+ to enter the muscle fibre, if reaches threshold
potential, Na+ channels open and Na+ enters, causing depolarisation and
voltage-gated channels to open
...
Ca2+ binds
to the Ca2+ binding site on troponin, changing its tertiary structure,
causing the tropomyosin tertiary structure to change, moving it aside and
revealing the actin-myosin binding sites
...
The
power stroke then happens (heads move), causing actin to slide over the
myosin
...
This energy is then used to break the actin-myosin cross bridge
...
This is repeated many times like a rowing
action, causing the muscle to shorten/contract
...


Myosin - CorreCt Answers -A long fibrous protein in muscle fibres

Myosin is made of
...
Has actin-myosin binding sites with troponin and
tropomyosin

Troponin - CorreCt Answers -Protein with 3 subunits:
1 - One binds to actin
2 - One binds to tropomyosin
3 - One binds to Ca2+

Tropomyosin - CorreCt Answers -When actin in muscles is at rest,
tropomyosin blocks the actin-myosin binding sites

What are the sources for the ATP for muscle contraction come from? CorreCt Answers -1 - A small amount is stored in muscle fibres which is
used for the first 1-2 seconds
...


CP + ADP --> ATP + CP

What happens to the creatine produced as a waste product during the
creation of ATP after ATP made - CorreCt Answers -Broken down into
creatinine, moved into blood, moved to kidneys, moved to urine
...

Why is coordination needed? - CorreCt Answers -Organisms need to
coordinate the function of different cells and systems to operate effectively

What can cells do through cell signalling? - CorreCt Answers -Transfer
signals locally between neurons and transfer signals over large distances

Differences between neuron and muscle fibre - CorreCt Answers -Neurons
involve cell signalling/cell communication whereas muscle fibres contract
to create movement

Neurons are stimulated through action potentials, while muscle fibres are
stimulated through depolarisation

Differences between a synapse and neuromuscular junction - CorreCt
Answers -- Synapses use any neurotransmitter, while neuromuscular
junctions (NJ) only use ACh
...
A NJ
occurs from a motor neuron to a muscle fibre
- Synapses are narrower, while NJs are wider
- Synapses don't have a wavy membrane, while NJs have a wavy membrane
(increases the surface area)
...

- In synapses Enzymes which break down excess neurotransmitters vary,
while in NJs its always AChE
- In synapses the enzymes aren't in clefts, while in NJs they are in clefts
...


Stimulus - CorreCt Answers -A change in an organism's external
environment that causes the organism to react

Response - CorreCt Answers -An action or change in behaviour that occurs
as a result of a stimulus
...

Example of cell signalling and communication
...

- Are long, so AP can travel long distances quickly
- Na+/K+ pumps & ion channels are present
- Many mitochondria and ERs to make neurotransmitters
...
Cell body is outside CNS in the middle of the neuron
...
Usually myerlinated
...
They
have many short and usually unmyerlinated axons and dendrons

Motor neurons - CorreCt Answers -Transmit impulses from relay or
sensory neurons to effectors
...
Usually myerlinated
...

Why is creatine phosphate system 'alactic'? - CorreCt Answers -No lactic
acid produced and no oxygen needed



---