Ch15 Nervous coordination Flashcards
1
Q
Nervous system
A
- nerve cells pass electrical impulses
- secrete neurotransmitters
- short-lived
- fast
- localised
2
Q
Hormonal system
A
- produces chemicals transported by blood plasma
- change in hormone concentration stimulate target cell receptors
- long-lasting
- wide-spread
- slower
3
Q
Resting potential of axon
A
- three Na+ actively transported out of axon
- two K+ ions actively transported into axon
- by sodium potassium pump
- Na+ channels are closed - axon is less permeable
- K+ ions diffuse out of axon through open channels
- more negative inside axon
4
Q
Depolarisation
A
- Stimulus reaches threshold value
- Na+ channels open
- Na+ diffuse into axon down electrochemical gradient
- membrane becomes more permeable to Na+ ions
- depolarisation occurs
- inside axon becomes more positive (+40mv)
5
Q
Repolarisation
A
- Potassium channels open
- Potassium ions diffuse out
- down electrochemical gradient
- Sodium channels occur
- repolarisation occurs
6
Q
Hyperpolarisation
A
- Outward movement of K+ ions
- Sodium channels close
- Axon becomes more negative than usual
7
Q
All or nothing principle
A
Once stimulus reaches threshold value, all action potentials reach same charge
8
Q
Different protein channels
A
- each protein has specific tertiary shape complementary to ions
- ions have different shapes and charges
9
Q
Saltatory conduction
A
- Myelin sheath is electrical insulator
- Action potential jump from node to node (of Ranvier)
- increases speed of conductance
10
Q
3 Factors affecting action potential speed
A
- myelin sheath
- diameter of axon
- temperature
11
Q
Diameter of axon
A
- greater diameter, faster speed of conductance
- less ion leakage
- membrane potential easier to maintain
12
Q
Temperature
A
- higher temperature, faster speed of conductance
- diffusion rate increases
- proteins and enzymes involved(active transport and channels) can denature
13
Q
Refractory period
A
- no NA+ ions can diffuse in because channels are closed
- no new action potential can be produced
14
Q
Function of refractory period
A
- Action potentials propagated in one direction only
- discrete impulses
- limits number of action potentials
15
Q
Transmission across cholinergenic synapse
A
- depolarisation of presynaptic membrane
- Calcium channels open and calcium ions enter synaptic knob
- Synaptic vesicles fuse with presynaptic membrane
- neurotransmitter(acetylcholine) released - exocytosis
- diffuses across synaptic cleft
- binds to receptors on postsynaptic membrane
- sodium channels open, sodium ions enter
- postsynaptic neurone is depolarised
16
Q
Recycling acetylcholine
A
- acetylcholinterase hydrolyses acetylcholine
- ethanoic acid and choline diffuse across synaptic cleft to presynaptic neurone
- Sodium channels close in postsynaptic knob- no new action potentials
- ATP reforms acetylcholine
17
Q
Spatial summation
A
- different presynaptic neurones converging on one synapse
- release enough neurotransmitter at same time to exceed threshold value
- Action potential produced
18
Q
Temporal summation
A
- One neurone release neurotransmitter many times over short period
- Neurotransmitter accumulate to exceed threshold value
- Action potential produced
19
Q
Mitochondria use
A
- Maintain active transport ions in sodium potassium pump
- Synthesis of neurotransmitter
- Movement of vesicles
- Synthesis of enzyme acetylcholinterase
20
Q
Unidirectionality
A
- Synaptic vesicles with neurotransmitter only synthesised in presynaptic neurone
- Neurotransmitter receptor only located at postsynaptic neurone
- Neurotransmitter diffused down concentration gradient
21
Q
Inhibition
A
- Neurotransmitter binds to receptor
- K+ and Cl- channels open
- K+ passes out and Cl- passes in
- Membrane potential hyperpolarised
- increased stimulation needed to reach threshold value
- more Na+ required
