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Neural Health And Functions > Neurotransmission > Flashcards

Neurotransmission Flashcards

(51 cards)

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1
Q

Excitable cells communicate via

A

Chemical neurotransmission

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2
Q

Synapses

A

Specialised structures where neurones contact each other

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3
Q

At synapses

A

Electrical signal is converted into a chemical message and then back to an electrical message

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4
Q

Action potential dependent neurotransmitter release

A
  1. Action potential invades the presynaptic terminal
  2. Membrane depolarisation occurs
  3. Voltage gated calcium channels open allowing calcium into the presynaptic terminal
  4. Increase in calcium promotes vesicle fusion to the presynaptic terminal
  5. Vesicles release transmitters into the synaptic cleft
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5
Q

Synthesis and storage of neurotransmitters

A

precursors molecules and/or synthesis enzymes located in the presynaptic terminal -> enzymes travel along the axons slowly -> and are used to synthesise neurotransmitters and package them into vesicles

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6
Q

Vesicles allow

A

Trains of action potentials

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7
Q

Exocytosis

A

Release of neurotransmitter into the presynaptic terminal

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8
Q

Endocytosis

A

The replenishing of vesicles

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9
Q

Docking

A

Vesicles binding the the presynaptic membrane -> before an action potential invades the terminal

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10
Q

Ca2+ sensing

A

Calcium ion entry triggers fusion of the vesicle

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11
Q

Endocytosis mechanisms

A

New vesicle membrane ‘pinched off’ generating a new vesicle

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12
Q

Loading

A

New vesicle is filled with neurotransmitter

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13
Q

Exocytosis/endocytosis cycle

A

Docking -> Ca^2+ sensing -> endocytosis -> Loading

Allows exocytosis to occur at any given rate

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14
Q

Metabolic receptors

A

Slow response

Requires ATP to activate a second messenger - like a signalling cascade

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15
Q

Ionotropic receptors

A

Fast response

Ion channels open when neurotransmitter binds allowing ions to move into postsynaptic membrane

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16
Q

Excitatory neurotransmitters

A

Increase the excitability of the postsynaptic neuron

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17
Q

Inhibitory neurotransmitters

A

Decrease the excitability of the post synaptic neuron

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18
Q

Excitatory postsynaptic potential - EPSP

A

Resting potential -> action potential invades presynaptic terminal triggering release of neurotransmitter binds to post-synaptic receptors opening ion channels -> ions move into cell depolarising it -> after release event membrane potential returns to resting

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19
Q

Inhibitory postsynaptic potential - IPSP

A

Inhibitory molecules like GABA
Ligand binds causing conformational change opening a channel pore allowing inhibitory ions through -> Cl- therefore moves into the cell -> causes hyperpolarisation -> requires Strom her stimulus to trigger an action potential so therefore inhibitory

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20
Q

Spatial summation

A

Summation not EPSPs generated at different synapses

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21
Q

Temporal summation

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A

Summation of EPSPs generated at the same synapse

22
Q

Effects of inhibitory inputs

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A

Excitatory input depolarises the dendrite of the neuron -> depolarisation passively propagates towards the soma -> inhibitory input suppresses the excitation, reducing the membrane depolarisation and preventing the generation of an action potential

23
Q

Agonist

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A

Mimics the effect of the endogenous neurotransmitter

24
Q

Antagonist

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A

Blocks the effects of the endogenous neurotransmitter

25
Preganglionic neurons
Release acetylcholine choline
26
Post ganglionic neurones
Release noradrenaline
27
Sympathetic nervous system
Participates in fight or flight response Ganglions are close together Sympathetic neurons located next to targets bind to different post-synaptic adrenoreceptors - relaxes airways in the lung - inhibits digestion - accelerates heart rate
28
Parasympathetic nervous system
Controls actions that do not require immediate a action - digestion - metabolic function - regulating kidneys, liver etc Ganglionic neurones release acetylcholine choline
29
Parasympathetic neurons
Travel large distances Bind to post-synaptic acetylcholine receptors resulting in - constriction of airways - stimulates digestion - slows heart rate
30
Somatic motor function
Under voluntary control Inner ages and commands all skeletal muscles in the body -moving eyes, motor movements, facial expression, speaking
31
Lower motor neurons
Directly command muscle contraction Activated by local spinal cord circuits Each motor neuron innervates a single muscle
32
Lower motor neurones found medial in the ventral horn
Will contract axial muscles when stimulated
33
Lower motor neurones found lateral in the ventral horn
Will contract distal muscles when stimulated
34
Alpha motor neurones
Directly trigger the generation of force by action potentials
35
Small motor neurones
Innervate small muscles
36
Large motor neurones
Innervate large muscles
37
The motor unit
The alpha motor neurone and all the muscle fibres it innervates is classed as the motor unit
38
Upper motor neurones
Found in spinal cord Found in brain and spinal cord
39
Muscle contraction
Result of the individual and combined action of motor units
40
Motor neuron pool
Collection of alpha motor neurons that innervate a single muscle Arrangements allows normal muscle activity to be maintained when damage occurs to a single motor neuron
41
Muscle contraction is initiated by
Ach release and binding to postsynaptic Ach receptors
42
Sarcolemma
Excitable cell membrane covering muscle fibres
43
Myofibrils
Contract in response to an action potential sweeping down the sarcolemma
44
Sarcoplasmic reticulum
Extensive intracellular sac that stores Ca^2+ in muscles
45
Contraction coupling
- Ca^2+ binds to troponin (on actin), exposing myosin binding sites on actin - Myosin binds to actin, myosin head pivots, sliding actin down - Myosin disengages at the expense of ATP
46
Excitation contraction coupling
1. Action potential in the alpha motor neuron propagates to the presynaptic terminal triggering 2. Exocytosis of ACh 3. Post synaptic depolarisation once ACh binds 4. Ca^2+ release from sarcoplasmic reticulum 5. Sliding actin/myosin filaments 6. Muscle contraction Relaxation occurs when Ca^2+ or ATP levels reduce
47
Reflex
An involuntary, nearly instantaneous movement in response to a stimulus -> does not require th brain
48
Myotatic or stretch reflex
Reciprocal innervate on of flexors and extensors Excitatory motor neurons contract agonist muscle while simultaneously an inhibitory inter neuron suppresses neurons going to the antagonist muscle
49
Crossed-extensor reflex
Painful stimulius -> activation of afferent axons -> activates excitatory interneurons -> motor neurons efferent induce contraction
50
Coordinated muscle activity
ensure stability -> opposite effect on one muscle compared to the other
51
Vestibulo -ocular reflex
Detection of head rotation -> inhibition of extraocular muscles on one side -> excitation of extraocular muscles on the opposing side -> eyes fixed Allows eyes to focus on the same thing preventing double vision

Neural Health And Functions (4 decks)

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