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Nervous System: Unit I > PNS Anatomy & Physiology > Flashcards

PNS Anatomy & Physiology Flashcards

1
Q

Somatic Nervous System vs. Autonomic Nervous System

A
  • somatic = regulates voluntary skeletal muscle
    • single neuron connects CNS w/ peripheral tissues
  • autonomic = regulates involuntary visceral smooth muscle, cardiac muscle, glands
    • pre- and post-ganglionic nerves connect at ganglion (to transmit signal from CNS to peripheral tissues)
    • sympathetic & parasympathetic
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2
Q

CNS origin of parasympathetic neurons

A
  • cranial nerve nuclei (@ brain stem)
  • sacral segments of spinal cord (S2-S4)
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3
Q

CNS origin of sympathetic neurons

A
  • Thoracic segment of spinal cord (T1-T12)
  • Lumbar segment of spinal cord (L1-L5)
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4
Q

Location of parasympathetic & sympathetic ganglia

A
  • parasympathetic = @ innervated organs
  • sympathetic
    • two paravertebral chains along spinal cord
    • prevertebral ganglia in abdomen
    • adrenal medulla = ~sympathetic ganglion
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5
Q

Length of pre- and post-ganglionic neurons: PNS vs. SNS

A
  • sympathetic:
    • pre-gang = short
    • post-gang = long
  • parasympathetic:
    • pre-gang = long
    • post-gang = short
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6
Q

Ratio of pre-ganglionic to post-ganglionic neurons: PNS vs. SNS

A
  • parasympathetic:
    • =1:1
    • fxns in a discrete, localized fashion
  • sympathetic:
    • =1:20
    • can fxn in diffuse or widespread manner
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7
Q
  • Cholinergic neuron NT release =
  • Adrenergic neuron NT release =
A
  • = acetylcholine (ACh)
  • = norepinephrine (NE)
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8
Q
  • acetylcholine receptors =
  • norepinephrine/epinephrine receptors =
A
  • = “cholinergenic receptors”
    • subtypes = nicotinic [N] & muscarinic [M]
  • = “adrenergic receptors”
    • subtypes = alpha & beta
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9
Q

Somatic nervous system NTs

A
  • ACh released by efferent neurons ==>
  • muscular nicotinic cholinergic (NM) receptors @ voluntary skeletal muscle @ NMJ
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10
Q

Parasympathetic nervous system NTs

A
  • Pregang ==> ACh @ ganglia ==>
  • Neuronal nictonic cholinergic (NN) receptors
  • Postgang ==> ACh @ end organs ==>
  • Muscarinic cholinergic (M1-5) receptors
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11
Q

Sympathetic nervous system NTs (preganglionic neurons)

A
  • Pregang ==> ACh @ ganglia and adrenal medulla ==>
  • neuronal nicotinic cholinergic (NN) receptors
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12
Q

Sympathetic nervous system NTs (postganglionic neurons)

A
  • Postgang ==> Norepinephrine @ effector organs ==>
    • a1-adrenergic & b-adrenergic receptors
  • Postgang ==> ACh @ sweat glands ==>
    • muscarnic cholinergic (M) receptors
  • Postgang ==> dopamine (DA) @ renal vascular smooth muscle ==>
    • dopamine (D1) receptors
  • Adrenal medulla ==> epinephrine (EPI) & some NE @ blood ==>
    • a1-adrenergic & b-adrenergic receptors
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13
Q

Typical innervation of organs + exception

A
  • most organs = dual innervation = both SNS & PNS
  • blood vessels = SNS only
    • posses non-innervated muscarin cholinergic recptors on resistance vessels (activated by muscarinic agonists, but not by activation of PNS)
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14
Q

“Tone” definition/characteristics

A
  • “tone” = intrinsic level of activity of an organ = integration of input from SNS & PNS
  • predominant control = mostly PNS (except vasculature = SNS)
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15
Q

Functions of PNS

A
  • overall fxn = conservation + restoration of NRG & maintain organ fxn during min activity
  • PNS ==> single organ system ==> discrete, local changes
  • “Rest & Digest”
    • slowed HR ==> lower BP
    • stimulate GI motility/secrete
    • empty bladder/rectum
    • pupil constriction
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16
Q

SNS fxns

A
  • activity adjusted to environment
  • widespread physiologic responses
  • “Fight or Flight” = response to stress/threat
    • increase HR + contract ==> increase BP
    • blood flow ==> skeletal muscles
    • rise in blood glucose
    • dilation of bronchioles & pupils
17
Q

Effects mediated by peripheral muscarinic cholinergic [M] receptors

A
  • cardio: decrease HR and AV conduction rate + vasodilation (indirect) ==> decreased BP
  • respiratory: bronchial mscle contraction
  • GI: increase in secretory & motor activity
  • Genitourinary: promote voiding
  • Eye: miosis (pupil constriction), accommodation (focus lens for near), outflow of aqueous humor
18
Q

Effects mediated by nicotinic neuronal cholinergic [NN] receptors

A
  • located @ autonomic ganglia
  • cardio: sympathetic effects = vasoconstriction, tachycardia, elevated BP
  • GI/urinary: parasympathetic effects = nauseau, vomiting, diarrhea, urination
19
Q

Effects mediated by nicotinic cholinergic [NM] receptors @ NMJ

A
  • muscle contraction
20
Q

Effects mediated by peripheral adrenergic receptors @ vasculature

A
  • a1 (vasoconstriction) & b2 (vasodilation) recetors
  • @ cutaneous, mucous membranes, splanchnic vasculature [a1 receptors] ==>
    • vasocontriction ==> increase in TPR
  • @ skeletal muscle [a1 & b2 receptors] ==>
    • vasocontriction or vasodilation
    • b2 activation (e.g. rx: Epi) ==> increased blood flow ==> decrease TPR
  • @ renal vasculature:
    • relaxation via D1 receptors
    • constriction via a1 receptors
21
Q

Effects mediated by peripheral adrenergic receptors @ heart

A
  • Primarily mediated by b1 receptors
  • SA node: Increase in heart rate (positive chronotropy)
  • AV node: Increase in conduction velocity; refractory period decreased
  • Atrial and ventricular cardiac muscle: Increase in force of contraction (positive inotropy)
22
Q

Summary: a1 vs. b1 vs. b2 vs. a2 (effects + BP effects)

A
  • α1: Vasoconstriction increases TPR and BP (reflex bradycardia occurs)
  • β1: Increased heart rate and increased force of contraction increases CO and BP
  • β2: Vasodilation decreases TPR and BP (reflex tachycardia occurs)
  • α2: Decrease in SNS outflow (via action in CNS) decreases BP
23
Q

Effects mediated by peripheral adrenergic receptors @ kidney

A
  • NE ==> increased renin release ==> vasoconstriction + fluid retention + increased BP
24
Q

Effects mediated by peripheral adrenergic receptors @ respiratory tract

A
  • Bronchial smooth muscle: bronchodilation via b2 receptors
25
Q

Effects mediated by peripheral adrenergic receptors @ eye

A
  • Mydriasis (pupil dilation): via a1 receptors
  • increased aqueous humor production: via B2 receptors (==> increased IOP)
      • minor increase in outflow via a1 receptors (==> decreased IOP)
26
Q

Effects mediated by peripheral adrenergic receptors @ GI tract

A
  • indirect smooth muscle relaxation: via a2 receptors
  • direct relaxation: via b2 receptors
27
Q

Effects mediated by peripheral adrenergic receptors @ skeletal muscle

A
  • marked tremor/shakiness: via b2 receptors
28
Q

Metabolic effects mediated by peripheral adrenergic receptor

A
  • liver: increased glycogenolysis via b2 receptors ==> increased blood glucose
  • fat: increased lipolysis via b3 receptors

Nervous System: Unit I (16 decks)

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