Nerve Coordination

Question 1

what is a synpase?

Answer 1

junction between neurones

Question 2

cholinergic synpase process?

Answer 2

• AP arrives at pre-sn knob
• voltage gated calcium ion channels open - Ca2+ diffuse in
• vesicles full of neurotransmitter ACh fuse with pre-sn memb
• ACh diffuses across synaptic cleft
• ACh binds with receptors on post-sn memb
• some Na+ channels open - Na+ diffuse in
• if threshold reached, voltage gated Na+ channels open
• AP triggered in post-sn
• AChE breaks down ACh and stops response
• products reabsorbed into pre-sn knob and recycled

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Question 3

how temp affects speed of conduction?

Answer 3

• high temp (up to 40 degrees)
• faster speed of AP
• mol have more kinetic energy
• diffuse faster

Question 4

how diameter of axon affects speed of conduction?

Answer 4

• greater diameter - faster speed of AP
• less resistance
• more surface area for ion movement

Question 5

what are nodes of ranvier?

Answer 5

tiny patches of bare membrane

(gaps in myelin sheath)

Question 6

what is saltatory conduction?

Answer 6

• when AP jumps between nodes of ranvier
• speeds up transmission of nerve impulses
• cytoplasm conducts enough electrical charge to depolarise next node

Question 7

myelin sheath

Answer 7

• made of schwann cells
• electrical insulator - prevents depolarisation
• prevents movement of ions in/out of neurone

Question 8

what happens at nodes of ranvier?

Answer 8

• lots of K+ and Na+ ion channels
• depolarisation only happens at nodes
• AP jumps between nodes (saltatory conduction)

Question 9

what is synaptic divergence?

Answer 9

• when one neurone joins many neurones
• spreads AP to other parts of body

Question 10

what is synaptic convergence?

Answer 10

• when many neurones join single neurone
• amplifies signal

Question 11

temporal summation

Answer 11

• single AP wont always trigger AP in post-sn memb
• strong AP will cause more frequent APs
• release more neurotransmitter
• add up to trigger AP in post-sn memb

Question 12

spatial summation

Answer 12

• weak stimulus may only create few AP
• doesnt always trigger AP in post-s neurone
• when neurotransmitter from multiple neurones combine to trigger AP in post-sn

Question 13

maintenance of resting potential

Answer 13

• sodium-potassium ion carrier protein (using ATP)
• actively transports 3 Na+ OUT and 2 K+ IN
• voltage gated sodium ion channel closes
• membrane not permeable to sodium ions
• potassium ion channel opens
• some K+ diffuse out down electro chem gradient
• doesnt reach equilib because of pos charge outside

Question 14

sensory neurone?

Answer 14

• single long dendron
• single short axon

Question 15

relay neurone?

Answer 15

• in CNS
• many short dendrites
• many short axons

Question 16

motor neurone?

Answer 16

• many short dendrites
• single long axon
• ends with neuromuscular junction

Question 17

receptor?

Answer 17

• specific - will only detect one type of stimulus
• cell OR protein
• transforms stimulus into electrical imp

Question 18

describe nervous communication?

Answer 18

• fast
• short lived
• localised

Question 19

what does nervous system split into?

Answer 19

CENTRAL NERVOUS SYSTEM

• brain
• spinal cord

PERIPHERAL NERVOUS SYSTEM

• all other neurones

Question 20

what does the peripheral nervous system split into?

Answer 20

SOMATIC nervous system

• conscious control

AUTONOMIC nervous system

• unconscious body activity

Question 21

what does the autonomic nervous system split into?

Answer 21

PARASYMPATHETIC nervous system

• slows things down
• neurotransmitter = ACh

SYMPATHETIC nervous system

• speeds things up
• neurotransmitter = noradrenaline

Question 22

what does it mean by synapses are unidrectional?

Answer 22

• only receptors on post-sm
• neurotransmitters rel from pre-synpatic knob
• diffuse from high to low conc across synaptic cleft

Question 23

PASSAGE OF AP

step 1 - RESTING POTENTIAL

Answer 23

• sodium potassium ion carrier protein
• actively transports (using ATP)
• Na+ out
• K+ in
• some K+ diffuses out via K+ channel

Question 24

PASSAGE OF AP

step 2 - GENERATOR POTENTIAL

Answer 24

• weak stimulus
• some Na+ channels open
• some Na+ ions diffuse in
• doesnt reach threshold
• Na+ K+ restores resting potential

Question 25

PASSAGE OF AP - step 3 - THRESHOLD

Answer 25

- GP reaches threshold - many voltage gated Na+ channels open - Na+ diffuse into axon - positive feedback

Question 26

PASSAGE OF AP step 4 - depolarisation

Answer 26

- Na+ channels open - Na+ diffuse rapidly in

Question 27

PASSAGE OF AP step 5 - repolarisation

Answer 27

- K+ channels open - K+ diffuses out - voltage gated Na+ close

Question 28

PASSAGE OF AP step 6 - hyperpolarisation

Answer 28

- when memb potential more negative than resting potential - K+ channels slow to close

Question 29

refactory period

Answer 29

- another AP cant be started - make AP - DISCRETE (non overlap) , UNIDRECTIONAL (one way)

Question 30

what is a neuromuscular junction?

Answer 30

synapse between motor neurone and muscle fibre

Question 31

differences compared to a cholinergic synapse?

Answer 31

- more receptors on post-sn memb - AP always generated - AChE found in pits on post-sn memb - receptors = nicotinic cholinergic receptors

Question 32

what is the all or nothing law?

Answer 32

- if GP reaches threshold - triggers AP - all AP = same size - strong stimulus generates more frequent AP

Question 33

wave of depolarisation?

Answer 33

- Na+ diffuse along neurone - ahead of AP, neurone in resting potential - Na+ triggers threshold - AP moves along as wave of depolarisation