Neurotransmission Flashcards

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1
Q

what is the function of dendrites in relation to membrane potential.

A

aka cell body
receive in-put signals
lead to depolarisation
hyperpolarisation of plasma membrane

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2
Q

what are axons responsible for in relation to membrane potential

A

responsible for out-put signal

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3
Q

ways to classify neurons

A

morphology/shape
afferent/efferent nerves
neurotransmitter

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4
Q

how are neurons classified by shape

A

Bi-polar neurons vs multi-polar neurones

number of projections from cell body

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5
Q

how are neurons classified by afferent/efferent

A

Neurones that transmit information towards the CNS are afferent (arriving)
Neurones that transmit information from the CNS are efferent (exiting, effector organ)

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6
Q

how are neurons classified by neurotransmitter

A

Substance / chemical they release (e.g. dopamine, acetylcholine)

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7
Q

name the function ways to classify nerves

A

sensory and motor nerves

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8
Q

function of sensory nerves

A

send information to the central nervous system about the internal and external environment

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9
Q

function of motor nerves

A

control the activity of the body by controlling muscle and gland functions (contraction, relaxation, secretion

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10
Q

synapse

A

Synapse is the junction between one neurone & the next cell

converts electrical impulse -> chemical signal for communication between cells (electro-chemical coupling)

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11
Q

type of communication of the synapse

A

Nerve-Nerve
Nerve-Organ / Organ-Nerve
Nerve-Muscle
Nerve-Gland

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12
Q

Synapses between nerve and muscle cells are also called …

A

neuromuscular junctions or motor end plates

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13
Q

the process of the chemical synapse

A

neurotransmitter is released from presynaptic neuron
neurotransmitter crosses synaptic cleft
neurotransmitter binds to receptor of specific plasma membrane protein changing the membrane potential

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14
Q

how are synapses categorised

A

either excitatory or inhibitory

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15
Q

what do neurotransmitters at excitatory synapses do and name example

A

depolarises the postsynaptic membrane.
e.g. acetylcholine binds to receptors of post synaptic cell and opens ligand-gated sodium channels - depolarises - reduce membrane potential and increase Na+ ions

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16
Q

types of potential

A

graded potentials

action potential

17
Q

difference between graded and action potential

A

gp - local changes in membrane potential but do NOT threshold of -50
die out over short distances

18
Q

how does the magnitude of the graded potential vary

A

Magnitude of graded potential varies directly with the magnitude of the triggering event

19
Q

action potentials of VGSC (Voltage Gated Sodium Channels)

A

If depolarisation at a certain spot on the neurone reaches a threshold voltage of approx. – 50 mV, the reduced voltage opens up several voltage-gated Na+ channels in that portion of the plasma membrane as well as adjacent portions of the membrane causing a wave of depolarisation along the cell. Strength does not decrease as it travels

20
Q

process of membrane potentials

A

action potential reaches -50 - depolarisation and VGSC open influx of Na+ ions ( Na+ ions move to cell)
reach membrane potential of +50 - closing of VGSC and opening of VGPC (Voltage Gated Potassium Channels)
hyperpolarisation - efflux of K- ions (K+ ions leave cell)
Opening of VGSC let some Na+ ions but not as intense
returns to resting membrane potential

21
Q

refractory period

A

the period when a further stimulus applied to the neurone (or muscle fiber) will not trigger another action potential

22
Q

what causes refractory period

A

Due to inactivation of sodium channels (absolute refractory period) and repolarisation brought about by opening of potassium channels and potassium ions (K+) movement out of cell (relative refractory period).

23
Q

what happens when a neurotransmitter reaches an inhibitory synapse and name example

A

hyperpolarises the postsynaptic membrane.
GABA binds to receptor of post synaptic neuron and opens ligand gated chloride (Cl-) channel
from -70 to -90
counteracts excitatory signals that may arrive at that neuron

24
Q

myelin sheath

A

a fatty sheath many neurons are encased in

25
Q

what is the function of the myelin sheath and what cells produce it

A

Myelin functions as an “electrical insulator” - restricts current flow
It is the expanded plasma membrane of a neighboring cell called the Schwann cell (or oligodendrocyte in the CNS
action potential moves to next ligand gated or voltage gated channel without having to start another action potential across myelin

26
Q

conditions that interfere with nerve conduction

A
Cold, ischaemia (reduction in blood flow)
Demyelinating diseases (Multiple sclerosi
27
Q

how does local anaesthetics inhibit voltage gated action Na+

A

Local anaesthetics inhibit voltage-gated Na+ channels.
This leads to an inhibition of the formation and propagation of action potentials along nerve fibres. Examples: “benzocaine”, “lidocaine