Nervous System

Question 1

What are the 2 main branches of the nervous system and what do they contain

Answer 1

• central nervous system: brain and spinal cord
• peripheral nervous system: sensory and motor neurones

Question 2

What is the role of the nervous system

Answer 2

detects and responds to stimuli (changes) within the body and in the outside enviroment

Question 3

what are the two types of motor neurone

Answer 3

• somatic (voluntary)
• automomic (involuntary)

Question 4

what are neurones

Answer 4

specialised cells that rapidly transmit nerve impulses through the body

Question 5

what are 3 types of neurones and their role

Answer 5

• sensory neurones: transmitt impulses from the receptor to the intermediate/motor neurone
• motor neurones: transmit impulses from the relay neurone to the effector
• relay neurone: form the CNS and spinal cord, transmit impulses between neurones

Question 6

what are the 2 states of a neurone

Answer 6

• resting potential: when neurones are at rest and not being stimulated
• action potential: when neurones are being stimulated and sending an electrical impulse

Question 7

How is the resting potential established

Answer 7

• the sodium/potassium pump actively transports 3 sodium ions out of the axon and 2 potassium ions into the axon
• the membrane is more permeable to potassium as they’re are more potassium ion channels open in the membrane, the potassium ions diffuse out by facilitated diffusion
• this creates a more negative charge inside the axon so the membrane is polarised

Question 8

what happens during action potential

Answer 8

the neurone is stimulated by the receptor or neurotransmitter, sodium channels open, sodium ions diffuse into the axon depolarsing the membrane

Question 9

how does the action potential travel along the length of an unmyelinated neurone

Answer 9

the depolariasation in one area of the neurones axon causes depolarisation in the next region and so on until the wave of depolarisation moves all down the axon

Question 10

how does the action potential travel long the length of a myelinated neurones

Answer 10

transmission of the action potential is faster as depolarisation only occured at the nodes of ranvier, the action potential jumps from one node of ranvier to another one. This is called saltatory conduction

Question 11

how does the cell return to the resting potential

Answer 11

• when the potential difference is +40mV, sodium channels close and potassium channels open so potassium ions diffuse out of the axon which repolarises the membrane so the inside of the cell becomes more negative: REPOLARISATION
• HYPERPOLARISATION: when too many potassium ions diffuse out of the axon

Question 12

what happens at a synapse

Answer 12

1. electrical impulse arrives at axon terminal and triggers and influx of calcium ions
2. this causes the vesicles containing neurotransmitters to fuse with the membrane and release neurotransmitters
3. the neurotransmitters diffuse across the synaptic cleft due to a concentration gradients
4. neurotransmitters bind to the receptors on post synaptic membrane
5. this causes sodium ions channels to open and an influx of sodium ions causes action potential in post synaptic neurone

Question 13

what are reflexes and why are they important

Answer 13

they’re a rapid automatic response to a stimulus which is not under conscious control, they are protective and avoid damage.