nervous system

Question 1

where are impulses from nerves processed and co-ordinated?

Answer 1

the brain

Question 2

what does the CNS consist of?

Answer 2

the brain and spinal cord

Question 3

neuron structure

Answer 3

• axon: the long section of the neurone through which an electrical impulse can travel
• myelin sheath: protects the axon and makes the impulse travel faster
• cell body: contains the neurone’s nucleus
• dendrites: at the ends of the neurone, allowing it to make connections to other neurones

Question 4

neuron types

Answer 4

• sensory neurones connect receptors with the CNS
• relay neurones are found within the CNS, allowing communication to and from the brain (they have no myelin sheaths)
• motor neurones connect the CNS to effectors

Question 5

usual width of a synapse

Answer 5

1 micrometre

Question 6

synapse function

Answer 6

• allow neurones to transmit electrical impulses to each other
• allow multiple neurones to connect with each other at once (connections are made between the dendrites of different neurones)
• synapses are the slowest part of the neuronal pathway

Question 7

How do impulses cross a synapse?

Answer 7

• an electrical impulse travels along the axon of a neurone until it reaches the end of the neurone
• the impulse causes a neurotransmitter chemical to diffuse from the axon across the synapse to the neurone on the other side
• when it reaches the surface of the dendrite, it binds to a receptor which allows the electrical impulse to be regenerated
• this new impulse then travels down the axon of the other neurone
• this process happens very quickly

Question 8

autonomic nervous system

Answer 8

• regulates the body’s unconscious actions e.g. heart rate

- consists of sympathetic nervous system (SNS) and parasympathetic nervous system (PNS)

Question 9

sympathetic nervous system

Answer 9

• fight or flight response
• helps body prepare for perceived threat
• inhibition of the digestive and immune systems, increased pupil size and heart rate, expansion of lungs
• these processes are meant to optimise functions in the body when it’s under attack (e.g. prioritising oxygen consumption instead of digesting food)

Question 10

parasympathetic nervous system

Answer 10

• rest and digest response
• helps the body recover and focus on maintenance
• stimulation of the digestive and immune systems, decreased in pupil size and heart rate, contraction of lungs

Question 11

monosynaptic reflex

Answer 11

• an involuntary, unlearned, automatic reaction to a specific stimulus which does not require input from the brain
• involves only one synapse between the sensory and motor neurone
• e.g. pulling hand away from hot stove