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

---

Nervous System

Nervous System
Co-ordinates all body activities
...

Divided into 2 sections:
CNS (Central Nervous System): Brain and spinal cord
...


Transmission:
Messages travel along sensory and motor neurons
...


Response:
Muscles and glands carry out some response
...

3 types:
Sensory:
• Carries impulses from sense organs to CNS
...


Interneurons:
• Carry information between sensory and motor neurons (in CNS
only)
...

Dendrites: Fibres which carry impulses towards cell
body
...

Schwann Cells: Make myelin sheath
...


Structure of Neuron
Cell Body: Contains nucleus and cell organelles
...

Cell bodies in sensory neurons: Outside CNS
...

Axon Terminals: Branches at end of axon which end in
neurotransmitter swelling containing neurotransmitter
chemicals
...


Fat
Bundles of
neurons

Fat
Bundles of
Neurons

Axon

Interneurons
Short neurons found only in CNS
...

Connect motor and sensory nerves
...

Causes inside of axon to be negative and outside to be positive
...

Stimulus below threshold has no effect
...

Threshold level varies from person to person e
...
for pain or
temperature
...

Hence impulse is carried or not
...

Inside of axon becomes positive, outside becomes
negative
...

Chain reaction set up
...

ATP needed for this
...
e
...


Nerve Impulse Transmission
Refractory Period:
Refractory Period: The short time span after a neuron has
carried an impulse during which a stimulus fails to cause a
response
...

Prevents overstimulation of neurons
...

Myelin absent:
• Changes in positive and negative charges occur all along dendrite
or axon
...


Myelin present:
• Charges move in and out only at the Nodes of Ranvier
...

• Speed of impulse increases
...

Found between axon terminals of one neuron and
dendrites of another neuron
...


Synapse
Neurotransmitters are made either in cell body of neuron
or in neurotransmitter swelling
...

Common neurotransmitters: Acetylcholine (ACh) and
noradrenaline
...

Ions cause neurotransmitter swellings in presynaptic
neuron to release neurotransmitter chemical
...

Neurotransmitter combines with receptors on
postsynaptic neuron
...


Synapse
Neurotransmitter broken down by enzymes
...

Can be recycled
...

Control direction of impulse (allow it to travel in one direction
only)
...
(Neurotransmitter ceases
to be produced due to constant stimulation and impulse is
inhibited)
...
g we get used to pain and noise
...
g
...


Central Nervous System (CNS)
2 parts:
Brain
Spinal Cord

Brain
Interpreting centre to sort and process impulses from
sensory neurons
...

Grey Matter: Cells bodies and synapses
...

Brain and spinal cord protected by bone
...

Spaces between meninges filled with cerebrospinal fluid
(CSF)
...

Acts as shock absorber and as exchange medium
between blood and brain
...


Structure of Brain

Cerebrum
Largest part of brain
...

Functions: Controlling voluntary movements, receiving
and interpreting impulses from sense organs, thinking,
memory, intelligence, language, emotions, personality
...

Left hemisphere: controls RHS of body
...

Right side: art, music, 3-D, emotional responses
...

Inner part of cerebrum = white matter
...


Cerebellum
Heavily folded
...

Allows smooth, refined muscular action
...


Responses of cerebellum are involuntary, once process
initially learned
...

Control involuntary actions e
...
breathing, blood
pressure, swallowing, coughing
...

Acts as a sorting centre for brain by relaying all
incoming messages to relevant part of brain
...

Regulates homeostasis control by monitoring body
temp, osmoregulation, blood pressure, thirst
...


Pituitary Gland
Located below hypothalamus
...

Called the master gland of the body
...

Caused by failure to produce dopamine – a
neurotransmitter
...

Symptoms:
Trembling in hands and legs
...

Shuffling unbalanced gait
...

Daily activities e
...
dressing, washing and eating become
difficult
...


Parkinson’s Disease
Usually occurs in elderly
...

No known prevention
...

Drugs to mimic dopamine reduce symptoms
...


Spinal Cord
Composed of nerve tissue
...

Transmits impulses to and from brain
...


Spinal Cord
Located in neural canal of vertebrae
...

White matter (axons) on outside
...

Central canal in centre of grey matter
...


Spinal Cord
Dorsal root: Carries sensory neurons into spinal cord
...

Both neurons linked by interneurons in grey matter
...


Outside spinal cord, dorsal and ventral roots combine to
form pairs of spinal nerves
...

Carry impulses to and from CNS
...

Cell bodies of motor neurons in grey matter of CNS
...

Examples:
Grasp reflex in children, blinking eyes (protective), breathing,
blood pressure control
...

Advantage of Reflex Action:
Fast responses
...


Withdrawal Reflex
E
...
pulling your hand back from hot flame
...

Sensory neurons carry impulse to spinal cord
...

Neuron takes impulse to brain
...

Hand is pulled back from hot flame
...

Hence brain becomes aware of event after it has
occurred
...

(In most other responses, the brain decides the response
and not the spinal cord)

---