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Anatomy And Physiology > Lecture 3 - Action Potentials/Synapses/Neurotransmitters > Flashcards

Lecture 3 - Action Potentials/Synapses/Neurotransmitters Flashcards

1
Q

Definition of Potential Difference

A

An uneven distribution of +ve and -ve charges.

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2
Q

Definition of Membrane Difference

A

Potential difference across a membrane.

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3
Q

Membrane Potential of undisturbed cell

A

+ve charge on the outside, -ve charge on the inside

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4
Q

Cell membrane resting potential of a neuron

A

-70mV

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5
Q

Ion content of Extracellular Fluid

A

High Concentration of Na+ and Cl-

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6
Q

Ion content of Intracellular Fluid

A

High Concentration of K+ and Pr- (Proteins)

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7
Q

Function of Selective Permeability of Membrane

A

Maintains differences in Extra/Intracellular Fluid

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8
Q

2 types of Channels in Membrane

A

Leak - always open
Gated - open/closed

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9
Q

Chemical Concentration gradient across membrane in Passive Movement

A

K+ moves out faster than Na+ moves in

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10
Q

Electrical Gradient across membrane in Passive Movement

A

+ve outer membrane repels K+ ions
-ve inner membrane attracts Na+ ions

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11
Q

Stronger Gradient in Passive Movement

A

Chemical Conc Gradient Stronger
Therefore K+ still moves out
Therefore net loss of +ve ions

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12
Q

Sodium/Potassium ion exchange pump

A

3 intracellular Na+ for 2 Extracellular K+

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13
Q

2 conditions for disturbing resting potential

A

Altering of Membrane permeability to Na+/K+
Altering of Na+/K+ exchange pump

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14
Q

Chemically gated channel mechanism (Na+)

A

At resting state, channel remains closed
In the presence of Acetylcholine at a binding site, conformational change occurs
Channel opens, allowing Na+ into the cell

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15
Q

Depolarisation Definition

A

Shift of membrane potential towards 0mV

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16
Q

Repolarisation Definition

A

Restoring of resting membrane potential

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17
Q

Hyperpolarisation Definition

A

Shift of Membrane potential away from 0mV

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18
Q

3 types of gated channels

A

Chemically Gated
Voltage Gated
Mechanically Gated

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19
Q

Voltage Gated Channel mechanism (Na+)

A

Gate closed at -70mV
During Depolarisation, activation (outer) gate opens
Na+ enters cell
At +30mV, inactivation (inner) gate closes

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20
Q

Mechanically Gated Channel mechanism (Na+)

A

Gate closed at resting state
When membrane is distorted, channel opens
Na+ enters cell
Once distortion ends, gate closes

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21
Q

Graded potential definition (2 points)

A

Potential produced when gated channel opens
Local to limited portion of cell membrane

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22
Q

6 Steps of Graded Potential Mechanism

A

Stimuli exposed to membrane
Sodium channel opens
Depolarisation occurs
Movement of Na+ produces local current
Depolarises local membrane
Once stimuli is removed, repolarisation occurs

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23
Q

Action Potential Definition

A

Electrical Signal that affects entire membrane surface
Change in permeability of cell membrane

24
Q

Excitable Membranes Definition

A

Membranes in Skeletal Muscle fibres/axons that can conduct action potentials

25
Q

Start point of Action Potential in neuron

A

Axon Hillock

26
Q

Direction of Action Potentials

A

Along axon length towards synaptic terminals

27
Q

All or None Principle

A

Every stimulus, no matter the size, generates identical action potential

28
Q

Action Potential Threshold

A

-60mV

29
Q

6 Steps in Action Potential Generation

A

Graded depolarisation brings excitable membrane to threshold (-60mV)
Voltage Gated Na+ channels open
Na+ enters cell
At +30mV, Na+ channels close, Voltage Gated K+ channels open
Repolarisation occurs
Once at resting potential, Voltage Gated K+ channels close

30
Q

Propagation of Action Potential Definition

A

Movement of Action Potential across Axon

31
Q

2 types of Propagation

A

Continuous
Saltatory

32
Q

4 Steps of Continuous Propagation

A

Action Potential develops in initial segment, depolarised to +30mV
Na+ ions spread away from open voltage gated channel in initial segment, causes graded depolarisation in next segment
Action Potential develops in new segment whilst initial segment repolarises
Cycle repeats

33
Q

Continuous Propagation Speed

A

1m/sec

34
Q

Schwann Cell Definition

A

Cell wrapped around neuron to provide protection and insulation

35
Q

Condition of Continuous Propagation

A

Occurs in unmyelinated axons

36
Q

Condition of Saltatory Propagation

A

When Continuous Propagation can’t occur
Occurs in Myelinated Axons

37
Q

Saltatory Propagation Speed

A

18-140m/sec

38
Q

4 Steps of Saltatory Propagation

A

Action Potential developed at initial segment, depolarised to +30mV
Local current produces graded depolarisation that brings neighboring axolemma to threshold (-60mV)
Action Potential develops at next node
Cycle repeats

39
Q

Synapse Definition

A

Site of communication between nerve cell and some other cell

40
Q

Most common type of Synapse

A

Chemical Synapse

41
Q

3 Locations of Synapses

A

Dendrite
On a cell body
Along length of Axon

42
Q

Direction of communication across Synapses

A

1 direction
Presynaptic Neuron to Postsynaptic Neuron/other cell

43
Q

6 Parts of a Synapse

A

Axon Terminal
Mitochondrion
Synaptic Vesicles
Presynaptic Membrane
Postsynaptic Membrane
Synaptic Cleft

44
Q

Function of Synaptic Vesicles

A

Contain Neurotransmitters

45
Q

Synaptic Cleft Definition

A

Narrow space between Pre/Postsynaptic Membranes

46
Q

2 types of Neurotransmitters

A

Excitatory
Inhibitory

47
Q

Excitatory Neurotransmitters Features

A

Causes depolarisation of postsynaptic membranes
Promotes action potentials

48
Q

Inhibitory Neurotransmitters Features

A

Causes hyperpolarisation of postsynaptic membranes
Suppresses action potentials

49
Q

2 Acetylcholine (ACh) Features

A

Most common neurotransmitter
Released at Cholinergic Synapses

50
Q

Locations of Cholinergic Synapses

A

Common in CNS
All Neuron-Neuron synapses in PNS
All Neuromuscular/Neuroglandular junctions in Parasympathetic division of ANS

51
Q

8 Events at Cholinergic Synapse

A

Action potential depolarises axon terminal of presynaptic neuron
Calcium ions enter axon terminal
ACh release via exocytosis
ACh diffuses across synaptic cleft
ACh binds to postsynaptic membrane Chemically gated Na+ channels
Depolarisation ends
ACh broken down by AChE and reabsorbed into axon terminal as choline
ACh resynthesized

52
Q

5 Important Neurotransmitters

A

Acetylcholine
Norepinephrine (or noradrenaline)
Dopamine
Serotonin
Gamma aminobutyric acid (GABA)

53
Q

Enzyme that breaks down Acetylcholine

A

Acetylcholinesterase (AChE)

54
Q

4 Features of Norepinephrine

A

Excitatory Neurotransmitter
Used in brain/ANS
Released at adrenergic synapses
Broken down by Monoanime oxidase

55
Q

4 Features of Dopamine

A

CNS Neurotransmitter
Both excitatory/inhibitory
Released by Dopaminergic Synapses
Dopamine deficiency linked to muscle stiffness

56
Q

4 Features of Serotonin

A

CNS Neurotransmitter
Involved in Sleep/Wake cycles
Serotonin deficiency important in context for depression
Released by Serotonergic Synapses

57
Q

2 Features of GABA

A

Inhibitory Neurotransmitter
Involved in anxiety reduction in CNS

Anatomy And Physiology (10 decks)

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