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ANSC3104 Nervous system > Neurophysiology > Flashcards

Flashcards in Neurophysiology Deck (85)
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1

Are solutes equally distributed between interior and exterior of cells?

No - there is unequal distribution

This creates concentration gradient as cell membrane is almost impermeable

2

What ions dominate ECF?

Na+ & Cl-

3

What ions dominate ICF)

K+ & A- (anions)

4

Define membrane potential

Separation of ions across a membrane (basis for excitable cell function)

Size of potential depends on amount of separation of opposite charges

Opposite charges are attracted to each other

5

Define resting membrane potential

Neurons at resting membrane potential have constant number of charges separated
Usually ~-70mV

6

Approximation of resting membrane potential

-70mV

7

Define polarization

Having a membrane potential - separation of ions across a membrane

8

Define depolarisation

Decrease in potential
Membrane less negative

9

Define repolarisation

Return to resting potential after depolarisation

10

Define hyperpolarisation

Increase in potential
Membrane more negative

11

Graded potential

Small stimulus --> small number of Na+ channels open --> small influx of Na+

12

What occurs when Na+ enters cell?

depolarisation

13

Action potential

A large stimulus causes membrane to reach threshold
Lots of Na+ channels open
Initially overcorrection: hyperpolarisation

Action potential complete after hyperpolarisation begins

14

After action potential

Na+ - K- pumps restores ions to original concentrations
Pump doesn't activate after every single AP

- Huge amounts of each ion in each compartment and only relative few involved in AP

15

All or nothing rule

If the membrane of an excitable tissue is stimulated, it will either respond with a maximal action potential that spreads along the membrane in an undiminished fashion or does not respond at all

All action potentials last for the same amount of time

16

What determines the strength of AP?

The frequency and area (number of nerves) of APs indicates the strength of signal

17

What is the 'trigger zone' of AP?

Axon hillock (AP is initiated here)

18

Can AP only move one way?

Yes

19

Absolute refractory period

Membrane area is already undergoing AP
Na+ channels are open & cannot be triggered to re-open until membrane has returned to res23qting potential (inactivation gates)

20

Relative refractory period

New AP can be triggered, by stronger than normal stimulus
When original site has recovered, AP moved too far away to trigger another

21

How is AP conducted?

AP conducted down axon to terminals
AP depolarises adjacent region to threshold, sets off new AP
AP appears to move down the axon (actually triggers identical events down the axon)
Spreads in an undiminished fashion
Signal replicated over long distances

22

Continguos conduction


Occurs on unmyelinated fibres

AP spreads down axon, along every patch of membrane --> requires a lot of energy to return membrane to resting potential

23

Saltatory conduction

Occurs in myelinated fibres
Occurs in long distance signals
Myelin = lipid - stops ions passing through (insulator)

Not continuous - 'Nodes of Ranvier'
AP travels down axon by jumping from node to node

Quicker and requires less energy than continuous conduction
- Small sections of axon stimulated, instead of entire axon
- ~50x faster

- Larger fibre diamter --> faster signal

24

What could happen if myelin sheath degrades?

MS
Signals jump between different pathways
Only affects motor neurons
Less controlled movements
e.g. move arm instead of foot

25

Classic NTRs

Small rapid acting
E.g. Acetylcholine, Noradrenalin, dopamine, serotonin, glutamate

26

Neuropeptides (type of NTR)

Larger, slower acting
E.g. insulin, bradykinin, oxytocin

Hormones are a type of neurotransmitter (slow acting)

27

Synaptic cleft

Gap between neurons

28

Synaptic knob

Axon terminals end with a slight swelling

29

Subsynaptic membrane

Membrane of postsynaptic neuron under synaptic knob

30

Conduction of impulse neuron to neuron junctions

Action potential reaches axon terminal of presynaptic neuron

Stimulates opening of voltage Ca+ channels

Calcium enters synaptic knob

Triggers the movement of NTR to the synaptic cleft via exocytosis of vesicles

NTR binds to specific receptors that are part of the chemically gated channels on synaptic membrane of post synaptic neuron

Specific channel opens