Nerves

Question 1

What is the CNS?

Answer 1

The Central Nervous System- the nerves running along your spine and through your brain

Question 2

What is the PNS?

Answer 2

The Peripheral Nervous System- the nerves that connect to all other parts of the body (not spine/brain)

Question 3

What is a nerve?

Answer 3

A bundle of neurons (nerve cells)

Question 4

What does a transducer do?

NB: Verb = to transduce

Answer 4

It converts energy from one form to another

Question 5

Example of a transducer?

Answer 5

A sensory receptor

Question 6

What is the pathway of impulses in the nervous system?

Answer 6

Stimulus (e.g. a change in light intensity)
Receptor (e.g. rod and cone cells in retina)
Sensory Neurone
CNS
Motor neurone
Effector (e.g. muscles in iris)
Response (e.g. size of pupil changes)

Question 7

Label a sensory neurone

DRAW/REVISE a diagram!!!

Answer 7

Dendrite 
Dendron
Cell body
Nucleus 
Axon
Direction of impulse from dendrite → axon

Question 8

Label a motor neurone

DRAW/REVISE a diagram!!!

Answer 8

Dendrites
Cell body
Nodes of Ranvier
Myelin Sheath
Axon
Synaptic knobs

Question 9

Details about the dendron of a sensory and motor neurone?

Answer 9

A sensory neurone has a long dendron

A motor neurone doesn’t have a dendron

Question 10

What is a an electrical impulse?

Answer 10

A rapid and fleeting change in charge across the membrane

Question 11

What does the myelin sheath do to a neurone?

Answer 11

It insulates the axon and prevents short circuits with other axons - increases speed of impulse

Question 12

A weak stimulus means

Answer 12

A low frequency of impulses

Question 13

A strong stimulus means

Answer 13

A high frequency of impulses + more than one neurone fires at the same time

Question 14

What is a synapse?

Answer 14

A connection between neurones

Question 15

What is the gap between neurones called and what is the size of it?

Answer 15

Synaptic cleft

Size: approx. 20nm

Question 16

How does information cross the gap between neurones?

Answer 16

The info crosses as a chemical signal because electrical impulses cannot cross the synaptic cleft

Question 17

What is a synaptic knob?

Answer 17

The swollen end of the axon

Question 18

What does a synaptic know contain?

Answer 18

Many vesicles that contain neurotransmitter chemicals

Many mitochondria

Question 19

What do the mitochondria do in a synaptic knob?

Answer 19

Release energy via aerobic respiration to make neurotransmitter chemicals

Question 20

How does info transmit across synapses?

Answer 20

1. There are many vesicles in the first neurone, which are full of the neurotransmitter chemical
2. When an impulses sweeps down the cell membrane of the presynaptic neurone, the change in charge causes the release of the neurotransmitter
3. The neurotransmitter molecules DIFFUSE across the cleft and bind to the membrane of the postsynaptic neurone
4. This causes an electrical impulses to start in the 2nd neurone

Question 21

What is a presynaptic and postsynaptic neurone?

Answer 21

Presynaptic neurone = first neurone in a synapse transmission
Postsynaptic neurone = second neurone in a synapse transmission