Nervous System

Question 1

Functions of myelin sheath

Answer 1

1. Acts as an insulator
2. Protects axon from damage
3. Speeds up movement of nerve impulse along the axon

Question 2

Describe action potential

Answer 2

Potassium is inside the cell and is negative

Once nerve is stimulated, sodium leaks out

For a nerve impulse to travel down axon, enough sodium ions must be released to reach the threshold potential of -55mv, from the resting rate of -70mv, which causes action potentials to occur,

If -55mv is not reached, action potential does not occur, called All or Nothing Response

Once it has reached -55mv, sodium gates open and sodium ions rush into the cell and shoots up to +40mv.

This depolarizes the cell and causes the inside to become positive.

This polarity change opens the potassium channels causing potassium ions to rush out of the cell

The sodium channels then close and rapidly repolarizes the cell back to a negative charge.

Too many potassium ions might rush out which causes the mv to become more negative than -70mv which is called hyperpolarization

The sodium-potassium pumps work to restore it to resting levels so the nerve can be stimulated again, this period is called the refractory period

Question 3

Describe how a nerve impulse travels across a synapse

Answer 3

Nerve impulses reaches cell at bottom of axon terminal, which activates voltage-gated calcium ion channels

Calcium ion floods into the cell, which causes the synaptic vesicle, which contains the neurotransmitter, to migrate across to the end of the presynaptic neuron

The neurotransmitter then diffuses across and combines with receptors at the postsynaptic neuron

This stimulates ligand-gated protein channels to open, allowing an increase in sodium and action potential to continue on postsynaptic neuron

The arrival of the neurotransmitters generate the nerve impulse in the next neuron

One way transmission, can’t go back

Question 4

5 types of receptors

Answer 4

Thermoreceptors

osmoreceptors

chemoreceptors (odours + taste)

pain receptors

touch receptors

Question 5

4 properties of reflexes

Answer 5

Rapid
Involuntary
Stimulus required to trigger reflex
Stereotypes

Question 6

What is a spinal reflex

Answer 6

Reflex carried out by spinal cord alone

Question 7

what are the a spinal reflex arc components

Answer 7

Stimulus –> sensory neuron –> interneuron –> CNS –> motor neuron –> muscles

Question 8

3 structures that protect the central nervous system

Answer 8

1. Cerebrospinal fluid
2. meninges
3. Bones

Question 9

3 functions of cerebrospinal fluid

Answer 9

1. Protection
2. Support
3. Transport

Question 10

3 layers of meninges

Answer 10

1. Dura mater (outer)
2. Arachnoid mater (middle)
3. Pia mater (inner)

Question 11

What are the 5 lobes of the cerebrum and what do they do

FIT PO
(LIKE FROM KUNG FU PANDA)

Answer 11

Frontal (emotions, thoughts, movement, problem solving, languages)

Insula (senses, addictions, disorders, emotions)

Temporal (memories, auditory information)

Parietal (temperature, touch, taste, pain)

Occipital (vision)

Question 12

What is the function of the corpus callosum

Answer 12

Joins the left and right hemispheres of the brain

Question 13

What is the function of the cerebellum

Answer 13

Cerebellum exercises control over posture, balance and coordination