6 Nervous coordination and muscles

Question 1

What are the two main forms of coordination in animals?

Answer 1

The nervous system

The hormonal system

Question 2

Give an example of nervous coordination

Answer 2

Reflex action e.g withdrawal of hand from an unpleasant stimulus

Question 3

Give an example of hormonal coordination

Answer 3

The control of blood glucose concentration

Question 4

What are neurones?

Answer 4

Specialised cells adapted to rapidly carrying nerve impulses from one part of the body to another

Question 5

What is a mammalian motor neurone made up of?

Answer 5

Cell body, dendrons, Schwann cells, myelin sheath and nodes of Ranvier.

Question 6

What do Schwann cells do?

Answer 6

They surround the axon, protecting it and provide electrical insulation

Question 7

What are noses of Ranvier?

Answer 7

Constrictions between adjacent Schwann cellswhere there is no myelin sheath

Question 8

What are the different types of neurones?

Answer 8

Sensory neurones, motor neurones and relay neurones

Question 9

What is the function of the sensory neurone?

Answer 9

It transmits nerve impulses from a receptor to a motor or relay neurone

Question 10

What is the function of a motor neurone?

Answer 10

It transmits nerve impulses from a relay neurone to an effector

Question 11

What is the function of a relay neurone?

Answer 11

It transmits impulses between neurones

Question 12

What is a nerve impulse?

Answer 12

A wave of electrical activity that travels along the axon membrane

Question 13

What prevents the sodium and potassium ions from diffusing across the axon plasma membrane?

Answer 13

The phospholipid bilateral of the axon plasma membrane

Question 14

By what process do sodium and potassium ions pass through ion gates channels?

Answer 14

Facilitated diffusion

Question 15

What is the resting potential value in humans?

Answer 15

-65mV

Question 16

What is the role of the sodium potassium pump?

Answer 16

Actively transport sodium ions out of the axon.

Actively transport potassium ions into the axon.

Question 17

What is the threshold that needs to be reached in order to create an action potential?

Answer 17

+40mV

Question 18

What is resting potential?

Answer 18

The difference in electrical charge maintained across the membrane of the axon of a neurone when not stimulated

Question 19

What is repolarisation?

Answer 19

Return to the resting potential in the axon of a neurone after an action potential

Question 20

Does the size of an action potential ever change?

Answer 20

No, it remains the same from one end of the axon to the other

Question 21

Why does an action potential pass along a myelinated neurone faster than an unmyelinated neurone?

Answer 21

Because in an unmyelinated neurone, the events of depolarisation have to take place all the way along an axon and this takes more time.

Question 22

What factors affect the speed at which an action potential travels?

Answer 22

Myelin sheath, diameter of the axon and temperature.

Question 23

What is saltatory conduction?

Answer 23

When an action potential jumps from one node of Ranvier to another.

Question 24

How can an organism perceive the size of a stimulus?

Answer 24

By the number of impulses passing in a given time.

By having different neurones with different threshold values

Question 25

What is the refractory period?

Answer 25

The period during which the membrane of the axon of a neurone can’t be depolarised and no new action potential can be initiated.

Question 26

What are the three purposes of the refractory period?

Answer 26

It ensures that action potentials are propagated in one direction only. It produces discrete impulses. It limits the number of action potentials.

Question 27

What is a synapse?

Answer 27

A junction between neurones, in which they have a narrow gap, the synaptic cleft, which a neurotransmitter can pass.

Question 28

What is a presynaptic neurone?

Answer 28

The neurone that releases the neurotransmitter

Question 29

What organelles does the synaptic knob possess?

Answer 29

Many mitochondria and large amounts of endoplasmic reticulum

Question 30

What are these organelles required for?

Answer 30

They are required in the manufacture of the neurotransmitter which takes place in the axon.

Question 31

Where is the neurotransmitter stored?

Answer 31

In the synaptic vesicles

Question 32

What are the features of the synapse?

Answer 32

Undirectionality - synapses can only pass information in one direction, from the presynaptic neurone to the postsynaptic neurone. Summation - a rapid build up of neurotransmitter in the synapse.

Question 33

What are the two types of summation?

Answer 33

Spatial summation | Temporal summation

Question 34

What is spatial summation?

Answer 34

When a number of different presynaptic neurones together release enough neurotransmitter to exceed the threshold value of the post synaptic neurone.

Question 35

What is temporal summation?

Answer 35

When a single presynaptic neurone releases neurotransmitter many times over a short period of time in order to exceed the threshold value.

Question 36

What are inhibitory synapses?

Answer 36

Synapses that make it less likely that a new action potential will be created on the post synaptic neurone.

Question 37

What is a cholinergic synapse?

Answer 37

A synapse in which the neurotransmitter is a chemical called acetylcholine.

Question 38

Where do cholinergic synapses occur?

Answer 38

Central nervous system | Neuromuscular junctions

Question 39

What are the three types of muscle in the body?

Answer 39

Cardiac muscle Smooth muscle Skeletal muscle

Question 40

What are myofibrils?

Answer 40

Tiny muscle fibres that individual muscles are made of

Question 41

Which two types of protein filament are myofibrils made of?

Answer 41

Actin and Myosin

Question 42

What is a sarcomere?

Answer 42

The distance between adjacent Z-lines

Question 43

What is tropomyosin?

Answer 43

An important protein found in muscle, which forms a fibrous strand around the action filament.

Question 44

What types of muscle fibre are there?

Answer 44

Slow-twitch fibres | Fast-twitch fibres

Question 45

What is a neuromuscular junction?

Answer 45

The point where a motor neurone meets a skeletal muscle fibre

Question 46

What is the sliding filament mechanism?

Answer 46

The process where actin and myosin filament slide past one another.