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Foundations To Medicine 2 > Autonomic Nervous System 1 > Flashcards

Autonomic Nervous System 1 Flashcards

1
Q

What are the functions of the sympathetic nervous system?

A

Fight or flight

Stressful situations

Increase in blood flow to the skeletal muscle

Increase in heart rate

Increase in blood pressure

Increase in blood sugar level

Pupillary dilation (myadriasis)

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2
Q

What are the functions of the sympathetic nervous system?

A

Conservation and restoration / rest and digest

Decrease in heart rate

Increase in activity of gastrointestinal tract

Pupillary constriction (myosis)

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3
Q

What is vagitomy?

A

A surgical operation in which one or more branches of the vagus nerve are cut, typically to reduce the rate of gastric secretion (e.g. in treating peptic ulcers)

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4
Q

What’s the vagus nerve?

A

Parasympathetic fibers innervation of the thoracic and abdominal viscera

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5
Q

Describe the disynaptic pathway

A

Preganglionic neuron is myelinated (faster transmission)

Origin of preganglionic neuron is in the CNS

Origin of the postganglionic neuron is on the autonomic ganglia, in the peripheral NS

Preganglionic neuron releases Acetylcholine as neurotransmitter, which binds to cholinergic nicotinic receptors (nicotinic neuronal subtype Nn)

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6
Q

Describe sympathetic nervous structure

A

Origin: T1-L2 medullary segments

Sympathetic- short preganglionic neurons

Long postganglionic neurons

Sympathetic ganglia located near CNS

Ratio of preganglionic to postganglionic is 1:20

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7
Q

Describe the parasympathetic nervous system

A

Origin: brain stem & S2 -S4

Long preganglionic neurons

Short postganglionic neurons

Parasympathetic ganglia located far from CNS

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8
Q

Distinguish the origin between the sympathetic and parasympathetic nervous system

A

Sympathetic Origin: T1- L2 spinal cord segments (lateral horn)

Parasympathetic origin:brain stem (autonomic motor nuclei of III, IX, and X cranial nerves) and sacral spinal cord segments S2-S4

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9
Q

Contrast ganglia location of sympathetics and parasympathetic nervous system

A

Sympathetic: -paravertebral sympathetic ganglion chain

-Collateral ganglia (prevertebral)

Parasympathetic: ganglia located near or embedded within the target tissue

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10
Q

Contrast the dysynaptic cleft of sympathetic and parasympathetic nervous system

A

Sympathetic:

Short cholinergic preganglionic fiber

Long post ganglionic fiber

Parasympathetic:

  • long preganglionic fiber
  • short postganglionicfiber
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11
Q

Constraint the ratio of preganglionic fibers yo postganglionic fibers in the autonomic nervous system

A

Sympathetic- ratio of preganglionic fibers to postganglionic fibers is 1:20

Parasympathetic- ratio of preganglionic fibers to postganglionic fibers is 1:3

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12
Q

Contrast activity of sympathetic and parasympathetic division

A

Sympathetic: activity often involves massive discharge of the entire system

Parasympathetic: activity normally to discrete organs

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13
Q

Contrast sympathetic and parasympathetic postganglionic neurotransmitters

A

Sympathetic: primary neurotransmitter of postganglionic neuron is norepinephrine.

Parasympathetic: primary neurotransmitter of the postganglionic neurons is acetylcholine

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14
Q

What are the exceptions to the common rule in the nervous system?

A

Adrenal medulla: directly innervated by preganglionic sympathetic fibers

Sweat glands: innervated by cholinergic sympathetic postganglionic neurons

Receptors on the sweat. Glands are cholinergic muscuranic: M3

Renal vasculature smooth muscle:
-Innervated by dopaminergic sympathetic postganglionic neurons

Receptors on the renal vasculature are dopaminergic: D1

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15
Q

Describe the adrenal gland

A

Preganglionic sympathetic axons synapse on chromaffin cells may ACh binds to Nn receptors

Chromaffin cells releases Catecholamines into the circulation: 80% epinephrine (E), 20% norepinephrine (NE)

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16
Q

What causes phaeochromocytoma?

A

Most common tumor of the adrenal medulla in adults

Derived from chromaffin cells

Secrete epinephrine, norepinephrine, and dopamine

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17
Q

What are the symptoms of phaeochromocytoma?

A

Occurs in “spells” -relapse and remit

  • Elevated blood pressure
  • headache
  • excessive sweating
  • palpitations(tachycardia)
  • pallor

Lab: elevated Catecholamines and their metabolites

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18
Q

How is phaeochromocytoma treated?

A

Surgery

Pre-op: phenoxybenzamine + beta-blocker

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19
Q

Explain cholinergic transmission within the presynaotic nerve (acetylcholine synthesis)

A
  1. Acetyl CoA synthesized in mitochondria
  2. Choline transported into the neuron via a sodium dependent carrier (CHT1)
  3. ACh synthesized in the cytoplasm from Acetyl CoA and choline, a reaction catalyzed by choline Acetyl transferase(ChAT)
  4. ACh transport into vesicles by the vesicular ACh transporter (VAChT)
  5. ACh released occurs when an action potential reaches the terminal and triggers calcium influx through voltage gated calcium channels

The uptake of choline is the rate limiting step in ACh synthesis

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20
Q

Explain cholinergic transmission across the synaptic cleft

A

Released ACh:

  • ACh binds to cholinergic receptors: nicotinic or muscuranic in the postsynaptic membrane
  • ACh binds to presynaptic M2 ACh receptors, which inhibit ACh release
  • Acetylcholine (AChEj splits ACh into choline and acetate
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21
Q

What are orangophosphates?

A

These are usually used as insecticides by farmers: chlorothion, CoRal, Diazinion, Malathion, Paraoxon, Parathion, Phosdrin, TEPP, Thio-TEPP

Orangophosphates inhibit irreversibly the enzyme Anticholinesterase

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22
Q

What are the symptoms of orangophosphates?

A

Muscuranic : diarrhea, urination, miosis, bronchospasm, bradycardia, emesis, lacrimation, sweating, salivation

Nicotinic: neuromuscular junction

CNS effects: respiratory depression, lethargy, seizures, coma

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23
Q

How is orangophosphate poisoning. Treated?

A

Atropine+ pralidoxime

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24
Q

Explain adrenergic transmission in the presynaotic nerve

A
  1. Tyrosine is transported into the adrenergic neuron by system L
  2. Tyrosine is then converted to L-DOPA by the enzyme tyrosine hydroxylase
  3. DOPA is then converted to dopamine by DOPA decarboxylase
  4. Vesicular monoamine receptor (VMAT) translocate dopamine into synaptic vesicles
  5. Intravesicular dopamine-B-hydroxylase converts dopamine to NE

Tyrosine conversion to DOPA by tyrosine hydroxylase is the rate limiting step in the formation of NE

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25
Q

Explain adrenergic transmission in the synaptic cleft

A

Norepinephrine (NE):
-Released NE binds adrenergic receptors: alpha or beta on the postsynaptic membrane

  • Released NE binds to presynaptic a2 autoreceptors which inhibits NE release
  • Termination of the action of NE results from diffusion away from the receptor site and reuptake into the nerve terminal, mediated by the Na+ dependent NE transporter (NET)
26
Q

What are the types of cholinergic receptors?

A

Nicotinic receptors (ionic channel linked)

Muscle type- Nm

Neuronal type-Nn

Both of these are ligand-gated sodium/potassium channels

Muscuranic receptirs(g-protein linked)

M1, M3, M5- are Gq linked(increases IP3, DAG & Ca2+)

M2,M4-Gi protein linked: decreased cAMP

27
Q

What is the mechanism of function of M1?

A

Location: nerve endings

Mechanism: Gq linked protein

Major functions- increased IP3, DAG cascade

28
Q

What is the mechanism of function of M2?

A

Heart, some nerve endings-location

Mechanism: Gi-coupled

Function: decreased cAMP, activates K+ channels

29
Q

What is the mechanism of function of M3?

A

Location: effector cells: smooth muscle, glands, endothelium

Mechanism: Gq-linked

Major function: increased IP3, DAG cascade

30
Q

What is the mechanism of function of Nn?

A

Location: ANS ganglia

Mechanism: Na+-K+ ion channel

Major functions: depolarizes, evokes action potential

31
Q

What is the function of Nm?

A

Location: neuromuscular endplate

Mechanism: Na+-K+ ion channel

Major functions: depolarizes, evokes action potential, causing a muscular contraction

32
Q

What are the main functions of Nn

A

Autonomic ganglia- postganglionic neuron activation

Adrenal medulla- chromaffin cells releases Catecholamines to bloodstream

Brain- neuronal development learning and memory

33
Q

What are the functions of the M1 receptor?

A

Location:Brains(neurons)

Function: higher cognitive functions

Location: autonomic ganglia (neurons )

Function: stimulates enteric nervous system

Signal mechanism: Gq, increased IP3, DAG, Ca2+

34
Q

What is the function of M2?

A

Location: presynaptic nerve terminal(neurons)

Function: inhibition of ACh release

Location: heart(mainly in the atria)

Function: decreased heart rate, decreased contractility of the atria

Mechanism of action: Gi protein, decreased cAMP

35
Q

What are the functions of the M3 receptors?

A

Location: exocrine glands

Function: exocrine gland secretions(lacrimal, sweat, salivary, gastric acid)

Location: pancreatic B cells

Function: increased insulin

Location: smooth muscles
Gastrointestinal smooth muscle
Function: increased gut peristalsis

Location: detrusor muscle

Function: increase bladder contraction

Location: eye: pupillary sphincter muscle, ciliary muscle

Function: pupillary constriction and accommodation

Location: bronchial smooth muscle

Function: bronchial constriction

Location: endothelial cells

Function: endothelial NO-mediated vasodilation

Mechanism: Gq-protein

36
Q

What are the adrenergic receptors?

A

B-receptors G protein linked

A-receptors-G protein linked

qis-a1,a2,b

37
Q

What are the types of B receptors?

A

B1, B2, B3- Gs- protein linked increased cAMP

38
Q

What are types of alpha receptors?

A

A1(a1A, a1B, a1D)-Gq-protein-linked

-Increased IP3, DAG, Ca2+

A2(a2a, a2B, a2C)

Gi- protein linked:
-decreased cAMP

39
Q

What is the mechanism of function of a1 receptors?

A

Location: eff3ctor tissues: smooth muscle, glands

G protein: Gq

Second messenger: increased IP3, DAG

Major functions: increased Ca2+, causes contraction, secretion

40
Q

What is the mechanism of action of Alpha 2 receptors?

A

Location: nerve endings, some smooth muscle

Second messengers: decreased cAMP

Major functions: decreased transmitter release (nerves), causes contraction(muscle)

41
Q

What is the mechanism of action of beta 1 receptors?

A

Location: cardiac muscle, juxtaglomerular apparatus

G protein: Gs

Second messengers: increased cAMP

Increases heart rate, 8ncreased force, increased renin release

42
Q

What is the mechanism of action of beta 2 receptors?

A

Smooth muscle of heart, liver, heart-location

G-protein- Gs

Increased cAMP

Major functions- relax smooth muscle; increased glycogenolysis; increased heart rate, force

43
Q

What are the mechanism of action of the beta 3(B3) receptors?

A

Location: adipose cells

G protein: Gs

Second messengers: increased cAMP

Major function: lypolysis

44
Q

What is the mechanism of action of dopamine (D1) receptors?

A

Location: smooth muscle

G-protein: Gs

Second messengers: increased cAMP

Major function: relax renal vasculature smooth muscle

45
Q

What are the functions of a1 receptors?

A

Location: vascular smooth muscle

Function: vascular smooth muscle contraction

Location: eye dilator pupillae muscle

Function: pupillary dilation

Location: intestinal and bladder sphincter smooth muscle

Function: intestinal and bladder sphincter contraction

Signal mechanism: Gq protein

46
Q

What are the functions of a2 receptors ?

A

Location:Presynaptic nerve terminal (neurons)

Function: decreased norepinephrine release

Location: pancreatic B cells

Function: decreased insulin release

Signal mechanism: Gi protein linked

47
Q

What are the functions of B1 receptors?

A

Location: heart
Function: increase heart rate and contractility

Location: kidney(juxtaglomerular cells)
Function: increased renin release

Location: adipocytes
Function: increased lypolysis

G protein: Gs- protein

48
Q

What is the function of B2 receptors?

A

Location: bronchial smooth muscle
Function: bronchial dilation

Location: blood vessels”s of skeletal muscle
Function: vasodilation

Location: uterine smooth muscle (myometrium)
Function: decreased uterine tone

49
Q

What is the function of B3?

A

Location: brown adipose tissue

Function: thermogenesis
-increased lipolysis

Signal m3chanksm : Gs, increased cAMP

50
Q

What is the dally innervated rule?

A

Most internal organs are innervated by both branches of the automonomic nervous system which exhibit antagonistic cells

Heart: sympathetic- norepinephrine B1 receptors, increased heart rate. Acetylcholine M2 receptors, decreased heart rate

Pupil: sympathetic- norepinephrine a1 receptors (increase in pupillary size)
Parasympathetic- acetylcholine M3 receptors (decreased pupillary size)

51
Q

What is the main tone of arterioles?

A

Mainly sympathetic- a1

Loss of predominant tone leads to hypotension

52
Q

What is the predominant tone of neuvs?

A

Sympathetic-a1

Loss of predominant tine results in venodilation

53
Q

What is the predominant tone of Heart SA node?

A

Parasympathetic

Receptor type: M2

Loss of predominant tone leads to increased heart rate

54
Q

What is the predominant tone of heart ventricle ?

A

Sympathetic- B1

Loss of predominant tone- loss of contractility

55
Q

What is the predominant of the iris ?

A

Predominant tone- parasympathetic tone

Receptor type- M3

56
Q

What is the predominant tone of ciliary muscle?

A

Parasympathetic

M3

57
Q

What is the predominant tone of GI tract?

A

Parasympathetic-M3

58
Q

What is the predominant tone of the urinary bladder ?

A

Parasympathetic-M3

59
Q

What is the predominant tone of salivary bladder?

A

Parasympathetic -M3

60
Q

What is the predominant tone of sweat glands?

A

Sympathetic

Foundations To Medicine 2 (37 decks)

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