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🏠5. Peripheral nervous system: Neurotransmitters

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Question Bank

1
What are the stages of pain physiology
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transduction transmission perception modulation

2
What is transduction
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Painful stimuli will generate action potential at the nerve ending

3
What is the process of transmission in pain physiology?
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Transfer of the sensory signal from PNS to CNS

4
What is the final stage of pain physiology called and what does it involve?
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Modulation - decreasing or suppressing the painful sensation

5
Activation of nociceptors
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releases mediators like bradykinin, substance P, and histamine → activate ion-gated transient receptor potential channels on axon terminals → increases membrane permeability to sodium and calcium ions → action potential of the spinothalamic pathway

6
What neurotransmitter do Aδ fibers release
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glutamate

7
What transmitters does C-fibers release
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glutamate and substance P

8
Pathway for pain signal from dorsal horn to somatosensory cortex?
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Afferent fibers → second order neurons → thalamus → somatosensory cortex

9
What is neural conduction?
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neurons transmit signals through changes in ion conduction across the cell membrane

10
What is membrane potential?
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The difference of ion concentration across the cell membrane

11
What is the resting membrane potential for neurons?
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-70 mV

12
resting membrane potential for K/Na in neurons
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K+ is higher inside the cell Na+ is higher outside cell

13
What is the Na, K ATPase pump responsible for?
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Establishing the concentration difference of K+ and Na+ across the cell membrane.

14
What is the Resting Stage in the context of an action potential?
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• resting membrane potential before the action potential begins • freely permeable to potassium ions • membrane is polarized at -70 mV

15
What happens during the Depolarization Stage of an action potential?
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• sodium channels open • influx of sodium ions • increases the membrane potential to the positive direction

16
What is the Repolarization Stage?
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• threshold of +40 mV • sodium channels close • potassium channels are activity open • Rapid outflux of potassium ions

17
What is the Refractory Period?
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• depolarization till resting membrane potential • ion channels will not respond to any new stimuli

18
What factors influence conduction velocity in nerve fibers?
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Fiber diameter and myelination.

19
Fiber diameter and velocity
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larger diameter = lower resistance = faster

20
Myelination and velocity
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myelin = insulation = faster

21
Process where action potentials move via jumps from node-to-node in myelinated axons?
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Saltatory conduction

22
What are the voltage-gated Na+ channels only expressed at in myelinated axons?
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Nodes of Ranvier

23
What are the advantages of saltatory conduction in myelinated axons?
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• Saves energy by decreasing the use of sodium/potassium pump • increases speed for faster neural communication

24
What is the effect of an excitatory postsynaptic potential (EPSP)?
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Membrane depolarization of the postsynaptic neurons opening the sodium channels

25
What is the effect of an inhibitory postsynaptic potential (IPSP)?
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Membrane hyperpolarization inhibiting an action potential by activating chloride channels

26
What is synaptic transmission?
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Axon terminal of 1 neuron propagates signal to dendrites of another neuron

27
What is an electrical synapse and how does it function?
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transfers action potentials across gap junctions allowing free movement of ions from one cell to the next extremely rapid neural communication.

28
What are the three main divisions of the peripheral nervous system?
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Somatic nervous system, Autonomic nervous system

29
What are the main branches of the Autonomic nervous system?
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Sympathetic and Parasympathetic

30
What are the two main subdivisions of the PNS?
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Afferent (sensory) nerves and Efferent (motor) nerves

31
T/F: Afferent nerves are pseudounipolar
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True

32
TF: Efferent nerves are multipolar
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True

33
What neurotransmitter is released at the neuromuscular junction in somatic nervous system?
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Acetylcholine

34
What is the function of the Somatic nervous system?
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Responsible for voluntary control

35
What is the main purpose of the Autonomic Nervous System?
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homeostasis and integrate the stress response.

36
What functions does the Autonomic Nervous System control?
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controls involuntary functions • regulates blood pressure • GI responses to food • bladder contraction of the urinary bladder

37
What is the function of the Enteric nervous system?
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function independently of the remainder of the nervous system • regulating digestive processes

38
What are the functions of the Sympathetic and Parasympathetic nervous systems?
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Sympathetic: Fight or Flight reactions and exercise Parasympathetic: Rest and Digest reactions

39
Function of hypothalamus in central control of the autonomic nervous system?
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• integrates info and sends output down spinal cord via hypothalamospinal tract • engages preganglionic fibers of sympathetic/parasympathetic nervous systems

40
Medulla role in central control of ANS
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vasomotor and vasodilator centers respiratory center

41
Role of the pons in central control of ANS
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respiratory center

42
Where is the parasympathetic nervous system controlled from
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hypothalamus

43
What do preganglionic efferent fibers release?
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acetylcholine to activate nicotinic receptors of postganglionic fibers

44
What do Post-ganglionic fibers release?
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acetylcholine to activate muscarinic receptors of the effector organs

45
What controls the sympathetic nervous system
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Hypothalamus control

46
What do preganglionic of SNS fibers release?
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releasing acetylcholine

47
What do postganglionic fibers of SNS release?
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noradrenaline

48
Describe length of fibers in SNS vs PSNS
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SNS • pre: short • post: long PSNS • pre: long • post: short

49
What are the three main classes of neurotransmitters?
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Excitatory, Inhibitory, Modulatory

50
List the excitatory neurotransmitters.
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Glutamate Acetylcholine Norepinephrine

51
What are the inhibitory neurotransmitters?
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GABA Glycine

52
What are the modulatory neurotransmitters?
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Dopamine Serotonin

53
What are the types of small molecules, rapid-acting neurotransmitters?
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Amino acids monoamines gaseous purines acetylcholine

54
What is the role of acetylcholine in the nervous system?
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neurotransmitter of sympathetic preganglionic neurons + PSNS

55
How is acetylcholine synthesized and degraded?
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Synthesized: by choline acetyltransferase from Acetyl-CoA and Choline Degraded: by acetylcholinesterase

56
Which types of fibers are cholinergic?
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Nicotinic Muscarinic

57
Where are nicotinic receptors located
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N1 + N2 • Neuromuscular junction in skeletal muscles • CNS • adrenal medulla • autonomic ganglia

58
What are Muscarinic receptors subdivided into?
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M1, M2, M3, M4, and M5

59
Where are Muscarinic receptors located?
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On the effector organs

60
Where are M1 receptors located
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brain

61
Where are M2 receptors located
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heart

62
Where are M3 receptors located
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bladder, exocrine glands, and smooth muscle

63
What are catecholamines?
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hormones and neurotransmitters produced by the adrenal glands and nervous system

64
Which two catecholamines stimulate adrenergic receptors of the SNS?
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Adrenaline and noradrenaline

65
What is the common amino acid from which catecholamines are synthesized?
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Tyrosine

66
catecholamine production pathway
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tyrosine → DOPA → dopamine → norepi → epi

67
What is the primary function of noradrenaline (norepinephrine) in the sympathetic nervous system (SNS)?
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mediates SNS by interacting w/ adrenergic receptors activates α1, α 2, β1 receptors

68
Which receptors does noradrenaline activate?
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activates α1, α 2, β1 receptors

69
How is noradrenaline inactivated in the body?
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via oxidation via monoamine oxidase (MAO) or methylation with catechol-0-methyltransferase (COMT)

70
Which receptors does adrenaline (epi) bind to?
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bind/activate all five alpha and beta receptors.

71
α1 receptor location and function
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L: Blood vessels, eye, bladder F: Vasoconstriction, mydriasis, closure of bladder sphincter

72
α2 receptor location and function
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L: Synaptic nerve ending F: prevents norepi and Ach release

73
β1 receptor location and function
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L: heart F: increase HR and contraction force

74
β2 receptor location and function
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L: Arteries, bronchi, uterus F: VD, bronchodilation, ↑ blood glucose

75
β3 location and function
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L: Adipose tissue F: lipolysis

76
How is dopamine synthesized?
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directly synthesized from L-Dopa

77
What is serotonin (5-HT) and what functions does it perform in the body?
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monoamine neurotransmitter sleep, eating, arousal, dreaming, mood regulation, and temperature/pain transmission

78
How is serotonin synthesized in serotonergic neurons?
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synthesized from the amino acid tryptophan

79
Where is serotonin found in high concentrations in the body?
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in enterochromaffin cells throughout the GI tract storage granules in platelets and CNS

80
GABA function
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inhibitory neurotransmitter reduces the excitability of neurons by hyperpolarization

81
How is GABA synthesized
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from glutamate via glutamate decarboxylase

82
Glycine function
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inhibitory neurotransmitter in the CNS

83
What is glycine synthesized from?
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from serine by serine hydroxy-methyltransferase

84
What is the role of glutamate in the central nervous system (CNS)?
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excitatory neurotransmitter in the CNS uses N-methyl-D-aspartate (NMDA) receptors

85
What mnemonic can be used to remember the vascular causes of seizures?
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VITAMINS ➢ Vascular (stroke, intracranial hemorrhage) ➢ Infection ➢ Trauma ➢ Autoimmune ➢ Metabolic ➢ Idiopathic ➢ Neoplasm ➢ pSychiatric, genetic factor

86
Epilepsy in relation to neurotransmitter dysfunction
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Too much glutamate - excitation Too little GABA - inhibition

87
What does a neurological exam include?
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Behavior, movements, and mental function tests.

88
What do blood tests detect in the context of seizures?
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Infections, genetic or metabolic conditions.

89
What do imaging and electroencephalogram (EEG) do?
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detects structural abnormalities EEG detects electrical activity in the brain

90
Symptoms/Phases of a seizure
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Prodromal • nonspecific emotional changes • hours-days before Aura • changes in emotions, hearing, smell, taste or vision • Minutes before seizure Ictal • seizure type specific Post-ictal • fatigue, confusion, soreness, amnesia, thirst

91
What is the difference between focal and generalized seizures?
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Focal: originate from a specific area of the brain Generalized: affect the entire brain

92
Ttypes of focal seizures
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Simple partial Focal impaired awareness seizure

93
Types of generalized seizures?
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Tonic seizure Clonic seizure Tonic-clonic seizure Absence seizure

94
What is the definition of a simple partial seizure?
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preserved consciousness preceded by an aura, followed by motor signs

95
What is a focal impaired awareness seizure
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accompanied by a loss of consciousness preceded by an aura between 30 second-2 minutes

96
What is a tonic seizure?
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Stiff/flexed • continuous muscle contraction • rigid and flexed • accompanied by patient falling backward

97
What is an atonic seizure
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muscle relaxtion patient falls forward

98
What is a clonic seizure
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convulsions • rhythmic, violent jerking • without initial tonic phase

99
What is a myoclonic seizure
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short muscle twitches • loss of consciousness

100
What is a tonic-clonic seizure
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both tonic an clonic phase • initial stiffening • followed by jerking • most common gen seizure

101
What is an absence seizure
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loss and gain of consciousness • start abruptly • brief lapse in consciousness • lasts 10 seconds

102
What is status epilepticus
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is seizure lasts more that 5 minutes usually tonic clonic

103
What are anticonvulsants and how do they work?
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reduce seizures by enhancing GABA activity or modulating glutamate activity

104
What is the surgical approach for managing drug-resistant focal epilepsy?
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resection of the epileptogenic cortex

105
How does the ketogenic diet influence neuronal excitability?
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state of ketosis → enhanced GABA levels + reduced neuronal excitability

106
What is Parkinson's disease?
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progressive neurodegenerative disease

107
Pathophysiology of PD
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• degeneration of dopaminergic neurons in substantia nigra pars compacta • depletion of dopamine • Clinical symptoms = >60% of Dop neurons depleted • Lewy bodies present

108
Clinical manifestations of PD
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1. tremors 2. rigidity 4. bradykinesia 4. postural instability