Nerves

Question 1

What is a reflex?

Answer 1

An automatic and involuntary action which prevents injury

Question 2

What are the steps in a reflex arc?

Answer 2

stimulus >receptor> sensory neurone >relay neurone (in CNS) > motor neurone >effector> response.

Question 3

What are the two parts of the central nervous system?

Answer 3

Brain and spinal cord

Question 4

Describe the nervous system of Hydra

Answer 4

A radially symmetrical nerve net, consisting of one type of unmyelinated neurone. Can only respond to a limited number of stimuli

Question 5

Which part of a motor neurone carries impulses towards the cell body?

Answer 5

Dendrite

Question 6

Which part of a motor neurone carries impulses away from the cell body?

Answer 6

Axon

Question 7

Which part of a neurone contains the nucleus and organelles?

Answer 7

The cell body

Question 8

Name area A on the spinal cord

Answer 8

White matter

Question 9

Name area B on the spinal cord

Answer 9

Grey matter

Question 10

Name area C on the spinal cord

Answer 10

Central canal

Question 11

Name neurone D on the spinal cord

Answer 11

Sensory neurone

Question 12

Name area E on the spinal cord

Answer 12

Dorsal Root

Question 13

Name F and the area it is within on the spinal cord

Answer 13

Cell body of the sensory neurone in the dorsal root ganglion

Question 14

Name neurone G on the spinal cord

Answer 14

Relay neurone

Question 15

Name structure H on the spinal cord

Answer 15

Cell body of motor neurone

Question 16

Name area I on the spinal cord

Answer 16

Ventral root

Question 17

Name neruone J on the spinal cord

Answer 17

Motor neurone

Question 18

Which organism was used to study axons?

Answer 18

Squid, due to wider axon diameter that electrodes could be attached to

Question 19

Give three methods that maintain resting potential at -70mV in a neurone

Answer 19

1. Sodium-potassium pump
2. Some open K+ channels allow K+ to leak out.
3. There are large protein anions in the cytoplasm

Question 20

What does the sodium potassium pump do?

Answer 20

Actively transports 3 Na+ out of the neurone and 2 K+ into the neurone per ATP hydrolysed.

Question 21

What happens during depolarisation?

Answer 21

Voltage gated Na+ channels open
Sodium rapidly diffuses into the axon, down an electrochemical gradient.
Potential difference increases to +40mV

Question 22

What happens during repolarisation?

Answer 22

Voltage gated K+ channels open
Potassium rapidly diffuses out of the axon, down an electrochemical gradient.
Potential difference decreases to -90mV

Question 23

What is it called when potential difference drops to -90mV?

Answer 23

Hyperpolarisation

Question 24

Which ion is moving at A and B, and in which direction?

Answer 24

Na+ into the axon

Question 25

Which ion is moving at D, and in which direction?

Answer 25

K+ out of the axon

Question 26

Why can't an action potential travel backwards?

Answer 26

The refractory period means that Na+ channels behind the action potential are inactivated

Question 27

What is the all or nothing law?

Answer 27

All action potentials are the same size and strength. They will only happen if the threshold is exceeded

Question 28

Which three factors affect the speed at which a nerve impulse can propagate?

Answer 28

Myelination, temperature, axon diameter

Question 29

Why does axon diameter affect speed of nerve impulse propagation?

Answer 29

Larger diameter decreases electrical resistance to flow of ions

Question 30

Why does temperature affect speed of nerve impulse propagation?

Answer 30

Higher temperature increases the kinetic energy, increasing the speed at which ions diffuse

Question 31

How does propagation of a nerve impulse happen when there is no myelin?

Answer 31

Short local circuits causing voltage gated sodium channels to open along the entire axon membrane

Question 32

How does propagation of a nerve impulse happen when the axon is myelinated?

Answer 32

Saltatory conduction means the impulse will jump between Nodes of Ranvier due to electrical insulation. Longer local circuits.

Question 33

How does neurotransmitter cause an action potential in a post synaptic membrane?

Answer 33

Released by exocytosis, diffuses across cleft, binds to receptors, opens ligand gated Na+ channels, causes depolarisation

Question 34

How do organophosphorus insecticides affect a synapse?

Answer 34

They inhibit acetylcholinesterase, meaning acetylcholine is not broken down and remains in the cleft, continuing to bind to receptors and open Na+ channels- excitatory

Question 35

What causes neurotransmitter to be released from a presynaptic neurone?

Answer 35

An action potential depolarises the pre synaptic bulb, causing voltage gated calcium channels to open. Ca2+ rapidly diffuses into the presynaptic bulb, down a concentration gradient. This causes vesicles of neurotransmitter to move to and fuse with the membrane.

Question 36

What is 1 on the motor neurone?

Answer 36

A dendrite

Question 37

What is 2 on the motor neurone?

Answer 37

The cell body

Question 38

What is 3 on the motor neurone?

Answer 38

The nucleus

Question 39

What is 4 on the motor neurone? Hint- it is carrying the impulse away from the cell body

Answer 39

The axon

Question 40

Name cell 5 on the motor neurone?

Answer 40

A schwann cell

Question 41

What is 7 on the motor neurone?

Answer 41

A node of Ranvier

Question 42

What is 8 on the motor neurone?

Answer 42

An axon terminal/presynaptic knob

Question 43

What does an agonist do?

Answer 43

Bind to and activate receptors on channel proteins, causing them to open and stimulating an action potential

Question 44

What does an antagonist do?

Answer 44

Bind to and block receptors on channel proteins, stopping neurotransmitter from binding and generally preventing an action potential being generated

Question 45

What is the result of an inhibitory drug?

Answer 45

Less action potentials stimulated in the post synaptic neurone

Question 46

What is the result of an excitatory drug?

Answer 46

More action potentials stimulated in the post synaptic neurone