Nervous System

Question 1

What are the two different types/divisions of the nervous system?

Answer 1

• Central nervous system (CNS)

• Peripheral nervous system (PNS)

Question 2

What makes up the CNS?

Answer 2

• Brain

• Spinal cord

Question 3

What does the somatic nervous system control?

Answer 3

Conscious activities (e.g. running)

Question 4

What does the autonomic nervous system control?

Answer 4

Unconscious actions (e.g. digestion)

Question 5

What does the sympathetic nervous system control?

Answer 5

‘Fight or flight’ actions (releases the neurotransmitter ‘noradrenaline’)

Question 6

What does the parasympathetic nervous system do?

Answer 6

Calms the body down - rest and digest (releases the neurotransmitter ‘acetylcholine’)

Question 7

What is a nerve?

Answer 7

A bundle of many nerve fibres enclosed within a protective sheath.

Question 8

What are nerve fibres?

Answer 8

The long axons of neurones together with any associated tissues.

Question 9

How does the sympathetic nervous system prepare the body to ‘fight-or-flight’?

Answer 9

• Causes the release of adrenaline from the adrenal glands

• Adrenaline causes the heart rate to increase - allowing for a rapid increase in blood supply to respiring muscles, allowing the muscles to have more oxygen and glucose for respiration

• Enables high-intensity activities like running away from a predator to be an immediate response

Question 10

Outline the pathway of a nervous system reaction

Answer 10

• Stimulus

• Receptor (in sense organ)

• Sensory neuron

• CNS

• Relay neuron

• Effector (muscle or gland)

• Response

Question 11

What are the three types of neurons?

Answer 11

• Sensory neurons

• Relay neurons

• Motor neurons

Question 12

Which type of neuron has the cell body in the middle/sticking upwards?

Answer 12

Sensory neurons

Question 13

What are the branches at the start of a neuron called?

Answer 13

Dendrites

Question 14

What are the insulating cells around an axon called?

Answer 14

Schwann cells

Question 15

What do Schwann cells make up?

Answer 15

Myelin sheath

Question 16

What does the myelin sheath do?

Answer 16

Insulates the axon to increase speed of action potential

Question 17

What is the section between the dendrite and a cell body called?

Answer 17

Dendron

Question 18

What are the unmyelinated areas of a motor neuron called?

Answer 18

Node of Ranvier

Question 19

What are the branches at the end of a neuron called?

Answer 19

Axon terminals

Question 20

Describe and explain the adaptations of neurons

Answer 20

• Highly branched endings (from dendrites), allows electrical impulses to pass from one to the other

• Myelin sheath, insulates most neurons, ensuring impulses travel rapidly along the axon

Question 21

What is the receptor that you need to know?

Answer 21

Pacinian corpuscles

Question 22

What are pacinian corpuscles?

Answer 22

• Mechanoreceptors that detect pressure and touch in the skin

• Composed of a sensory neuron which is wrapped in layers of lamellae

Question 23

How do pacinian corpuscles transmit action potential?

Answer 23

• When it’s stimulated, the lamellae deform and press on the sensory nerve ending

• This causes sodium ion channels to open and sodium ions diffuse into the cell, creating a generator potential

• If the generator potential reaches the threshold, it triggers an action potential along the sensory neuron

Question 24

What is the word that means to change energy from one form to another (e.g. from light energy to electrical energy)?

Answer 24

Transduction - sensory neurons are transducers

Question 25

Where are myelinated neurons found?

Answer 25

• Most neurons in the CNS and PNS are myelinated (require fast conduction)

Question 26

Where are unmyelinated neurons found?

Answer 26

• Mostly in the brain as grey matter

Question 27

What happens in the cell during an action potential?

Answer 27

• Stimulus - stimulus excites the cell membrane, opening sodium ion channels (making the inside less negative as sodium diffuses in) • Depolarised - if reaches voltage of -55mV, more sodium ion channels open • Repolarised - when a voltage of 30mV is reached, sodium ion channels close and potassium ion channels open (potassium diffuses out) • Hyperpolarised - potassium ions are slow to close so there’s an overshoot (less than -70mV voltage), allowing for a time delay between action potentials • Resting potential - ion channels are result, sodium-potassium pump returns the membrane to its resting potential

Question 28

What is the refractory period?

Answer 28

The time between when resting potential is reached after depolarisation and when it returns to resting potential after hyperpolarisation

Question 29

How does the wave of depolarisation move along the neurone?

Answer 29

• When an action potential happens, some of the sodium ions that enter the neurone diffuse sideways • This causes sodium ion channels in the next region of the neurone to open and sodium ions to diffuse into that part

Question 30

What are the purposes of synapses?

Answer 30

• Allows neurones to communicate • Ensure transmission between neurones is unidirectional • Allows convergence • Allows divergence • Filters out low level stimuli • Prevents fatigue/over-stimulation

Question 31

Describe the stages of how neurones transmit action potentials between neurones.

Answer 31

• Action potential arrives at synaptic knob of presynaptic neurone, stimulating calcium ion channels to open, causing calcium ions to diffuse into synaptic knob • Influx of calcium ions into synaptic knob causes synaptic vesicles to move to the presynaptic membrane (and fuse with it, causing exocytosis of neurotransmitters) • Neurotransmitter diffuses across synaptic cleft and binds to specific receptors on postsynaptic membrane, causing sodium ion channels in postsynaptic neurone to open, causing depolarisation of postsynaptic neurone if generator threshold reached (neurotransmitter then removed from synaptic cleft)

Question 32

What is the name of the type of synapse you need to know?

Answer 32

Cholinergic synapse

Question 33

What is the name of the neurotransmitter you need to know, and which enzyme is it broken down by?

Answer 33

• Acetylcholine • Acetylcholinesterase

Question 34

What is the name of many neurones connecting to one neurone?

Answer 34

Synaptic convergence

Question 35

What is the name of one neurone connecting to many neurones?

Answer 35

Synaptic divergence

Question 36

What is spatial summation?

Answer 36

Multiple impulses arrive at the same time from different synaptic knobs, releasing large amounts of neurotransmitter into the same synaptic cleft

Question 37

What is temporal summation?

Answer 37

When two or more nerve impulses arrive in quick succession from the same presynaptic neurone into the same synaptic cleft (the effect of the impulses are added together to generate an action potential)