Nervous Coordination And Muscles

Question 1

What are the parts of a motor neurone?

Answer 1

Cell body, dendrons, axon, Schwann cells, myelin sheath and nodes of ranvier

Question 2

What are Schwann cells?

Answer 2

It protects the axon and carries out phagocytosis

Question 3

What’s a myelin sheath?

Answer 3

Covers the axon and is made up of the membranes of Schwann cells

Question 4

What are nodes of ranvier?

Answer 4

Constructions between adjacent Schwann cells where there is no myelin sheath

Question 5

What are sensory neurones?

Answer 5

Transmit nerve impulses from a receptor to an intermediate or motor neurone

Question 6

What are motor neurones?

Answer 6

Transmit nerve impulses from an intermediate relay neurone to an effector (gland/ muscle)

Question 7

What are intermediate/relay neurones?

Answer 7

Transmit impulses between neurones

Question 8

What happens at resting potential?

Answer 8

3 Na+ are actively transported out of the axon whilst 2 K+ are transported in by the sodium potassium pump. Na+ is more positive than K+ causing more Na+ to be in the tissue fluid than in the cytoplasm. Na+ naturally diffuse back in whilst K+ move out

Question 9

How do you reach action potential?

Answer 9

K+ channels open Na+ channel closed they then open causing Na+ to enter the axon more channels open so more Na+ enters. If this reaches +40mv an action potential has been met

Question 10

How do you depolarise an axon?

Answer 10

After action potential has been met Na+ ion channels close and K+ channels are open. This causes K* to leave the axon. This causes the axon to be more negative than usual (hyperpolarisation). K+ then leaves the axon causing it to reach resting potential -65mv and repolarise

Question 11

When can action potentials occur along myelinated axons?

Answer 11

Action potentials can only occur where there is no myelin insulin (nodes of ranvier)

Question 12

What factors affect the speed of action potentials?

Answer 12

How often there are gaps in the myelin sheath
The diameter of the axon
Temperature

Question 13

What’s the point in a refractory period?

Answer 13

Ensures action potentials are propagated in one direction only
Produces discrete impulses
Limits the number of action potentials

Question 14

What’s spatial summation?

Answer 14

A number of different presynaptic neurones together release enough neurotransmitter to exceed threshold of the post synaptic neurone

Question 15

What’s temporal summation?

Answer 15

A single presynaptic neurone releases neurotransmitter many times over a short period of time. If it exceeds threshold of the postsynaptic neurone an action potential will be triggered

Question 16

What is hyperpolarisation?

Answer 16

Presynaptic neurone releases a neurotransmitter that attaches to Cl- channels on postsynaptic to open them so Cl- moves in whilst K+ moves out. This makes the postsynaptic neurone negative becoming less likely to create an action potential

Question 17

What happens in a transmission across a synapse?

Answer 17

Ca2+ attach to receptors on outside is presynaptic neurone causing it to enter. This causes the vesicles to move and fuse with the membrane releasing acetylcholine. This diffuses along the synaptic cleft and bind with receptors of Na+ ion channels on the postsynaptic neurone. Na+ enters generating an action potential

Question 18

What’s the I band?

Answer 18

Only actin

Question 19

What’s the A band

Answer 19

Actin and myosin

Question 20

What’s the h zone?

Answer 20

Myosin only

Question 21

What are slow twitch fibres?

Answer 21

Less powerful contractions but over a long period of time best used for marathons. Aerobic respiration

Question 22

What are fast twitch fibres?

Answer 22

They contract more rapidly and produce more powerful contractions but only for a short period of time. Anaerobic respiration

Question 23

What changes when a muscle contracts?

Answer 23

The I band becomes narrower
The z lines are closer together
The h zone bee comes narrower

Question 24

What is myosin and actin made of?

Answer 24

Fibrous protein tail and globular protein head for myosin
Globular protein for actin

Question 25

How does a muscle contraction happen?

Answer 25

Tropomyosin prevents myosin head attaching to the binding site on actin. Ca2+ released from epr cause tropomyosin to unwind so myosin head can now attach and move the actin to the side releasing ADP. ATP then attaches to myosin causing it to deattach from actin. Hydrolysis of ATP means myosin moves back to normal