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Neural Health And Functions > Neurotransmission > Flashcards

Neurotransmission Flashcards

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

A

Summation of EPSPs generated at the same synapse

22
Q

Effects of inhibitory inputs

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

A

Mimics the effect of the endogenous neurotransmitter

24
Q

Antagonist

A

Blocks the effects of the endogenous neurotransmitter

25
Q

Preganglionic neurons

A

Release acetylcholine choline

26
Q

Post ganglionic neurones

A

Release noradrenaline

27
Q

Sympathetic nervous system

A

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
Q

Parasympathetic nervous system

A

Controls actions that do not require immediate a action

  • digestion
  • metabolic function
  • regulating kidneys, liver etc

Ganglionic neurones release acetylcholine choline

29
Q

Parasympathetic neurons

A

Travel large distances

Bind to post-synaptic acetylcholine receptors resulting in

  • constriction of airways
  • stimulates digestion
  • slows heart rate
30
Q

Somatic motor function

A

Under voluntary control

Inner ages and commands all skeletal muscles in the body
-moving eyes, motor movements, facial expression, speaking

31
Q

Lower motor neurons

A

Directly command muscle contraction

Activated by local spinal cord circuits

Each motor neuron innervates a single muscle

32
Q

Lower motor neurones found medial in the ventral horn

A

Will contract axial muscles when stimulated

33
Q

Lower motor neurones found lateral in the ventral horn

A

Will contract distal muscles when stimulated

34
Q

Alpha motor neurones

A

Directly trigger the generation of force by action potentials

35
Q

Small motor neurones

A

Innervate small muscles

36
Q

Large motor neurones

A

Innervate large muscles

37
Q

The motor unit

A

The alpha motor neurone and all the muscle fibres it innervates is classed as the motor unit

38
Q

Upper motor neurones

A

Found in spinal cord

Found in brain and spinal cord

39
Q

Muscle contraction

A

Result of the individual and combined action of motor units

40
Q

Motor neuron pool

A

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
Q

Muscle contraction is initiated by

A

Ach release and binding to postsynaptic Ach receptors

42
Q

Sarcolemma

A

Excitable cell membrane covering muscle fibres

43
Q

Myofibrils

A

Contract in response to an action potential sweeping down the sarcolemma

44
Q

Sarcoplasmic reticulum

A

Extensive intracellular sac that stores Ca^2+ in muscles

45
Q

Contraction coupling

A
  • 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
Q

Excitation contraction coupling

A
  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
Q

Reflex

A

An involuntary, nearly instantaneous movement in response to a stimulus -> does not require th brain

48
Q

Myotatic or stretch reflex

A

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
Q

Crossed-extensor reflex

A

Painful stimulius -> activation of afferent axons -> activates excitatory interneurons -> motor neurons efferent induce contraction

50
Q

Coordinated muscle activity

A

ensure stability -> opposite effect on one muscle compared to the other

51
Q

Vestibulo -ocular reflex

A

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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