peripheral NS anatomy and phys

Question 1

1. List the neurotransmitters and receptors that mediate neurotransmission at the ganglia and/or end organs in the parasympathetic nervous system

Answer 1

Parasympathetic: Ach released from pre-ganglionic neuron (cell body in brainstem) > binds to nicotinic cholinergic receptor on post ganglionic neuron in the ganglia > Ach released from post ganglionic terminal and binds to muscarinic receptor to act on cardiac/smooth muscle, gland cells or nerve terminals

Question 2

1. List the neurotransmitters and receptors that mediate neurotransmission at the ganglia and/or end organs in the sympathetic nervous system

Answer 2

Sympathetic: Ach released from pre-ganglionic neuron (cell body in spinal cord) > Binds to nicotinic cholinergic receptor at ganglia > post ganglionic terminal releases Ach (muscarinic receptors on sweat glands), NE (adrenergic receptors on cardiac muscle, smooth muscle, gland cells or nerve terminals), or dopamine (dopamine receptors on renal vascular smooth muscl)

Question 3

1. List the neurotransmitters and receptors that mediate neurotransmission in the somatic nervous system

Answer 3

Ach released from motor nerve (cell body in spinal cord)> binds to nicotinic receptor on skeletal muscle

Question 4

1. List the neurotransmitters and receptors that mediate neurotransmissionfrom the adrenal medulla

Answer 4

Ach released from pre-ganglionic neuron > EPI and some NE released from adrenal medulla (acts as sympathetic ganglion) into general circulation > binds adrenergic receptors

Question 5

Where do PSNS and SNS neurons originate in CNS?

Answer 5

PSNS: neurons originate in cranial nerve nuclei (tectal region of brain stem) and sacral segments (S2-S4) of spinal cord. SNS: neurons originate in the thoracic (T1-T12) and lumbar (L1-L5)
segments of spinal cord

Question 6

Location of PSNS and SNS ganglia

Answer 6

Parasympathetic ganglia (most) are located in the innervated organs. Sympathetic ganglia are located in two paravertebral chains along spinal cord (most) or in prevertebral ganglia in the abdomen (some).

Question 7

Length of pre- and post-ganglionic neurons

Answer 7

PSNS: preganglionic are long, postganglionic are short. SNS: preganglionic are short, postganglionic are long

Question 8

Ratio of pre- to post-ganglionic neurons

Answer 8

PSNS: 1:1 (localized). SNS: 1:20-50 (diffuse)

Question 9

Which organs are innervated by PSNS and which by SNS?

Answer 9

Most organs are dually innervated except blood vessels receive sympathetic innervation only. Resistance Vessels have non-innervated muscarinic cholinergic receptors (activated by muscarinic agonists but NOT by activation of the parasympathetic nervous system)

Question 10

Which receptors are ionotropic and which are metabotropic

Answer 10

nicotinic are ionotropic. Muscarinic and adrenergic are metabotropic

Question 11

2. Discuss the concept of “tone” and the exception

Answer 11

An organs intrinsic level of activity determined by which branch of the autonomic nervous system is dominant. Parasympathetic branch is almost always predominant, except in control of vasculature tone where SNS is dominant.

Question 12

4. Describe homeostasis, flight-or-fight, and rest-and-digest with regard to sympathetic and parasympathetic activity.

Answer 12

PSNS: essential for life, rest and digest, produces discrete/localized discharges. SNS: not essetial for life, flight or fight, widespread discharges

Question 13

5. Describe the responses of end organs to physiologic activation of the sympathetic and parasympathetic nervous systems. (HR, BP, blood flow, pupils, saliva)

Answer 13

PSNS: slows HR, lowers BP, stimulate GI motility and secretions, increase nutrient absorption, empty bladder and rectum, pupil constriction (near focus), stimulate profuse and watery saliva. SNS: stimulates scant and viscous saliva, increase HR, increase contractility and BP, shift blood from skin/organs to muscles, rise in glucose, dilate bronchioles and pupils

Question 14

What effects are mediated by muscarinic receptors in cardiovascular, respiratory, GI, genitourinary and eye

Answer 14

CV: decreased HR and AV conduction, vasodilation (indirect effect mediated by NO and cGMP, no innervation by PNS). Respiratory: bronchial muscle contraction. GI: Increase in secretory and motor activity. Genitourinary: promote voiding. Eye: miosis (constriction of pupil), accommodation (lens focusing), outflow of aqueous humor.

Question 15

What effects are mediated by nicotinic receptors at autonomic ganglia (cardiovascular, GI/urinary) and at neuromuscular junction

Answer 15

Autonomic ganglia: sympathetic effects at cardiovascular organs (vasoconstriction, tachycardia, elevated BP) and parasympathetic effects at GI/urinary (nauseau, vomiting, diarrhea, urination). NMJ: contraction of muscles

Question 16

What effect do adrenergic receptors have on vasculature (cutaneous, mucus membranes, splanchnic, skeletal muscle, renal vasculature)

Answer 16

1. Cutaneous, mucous membranes, splanchnic vasculature : Vasoconstriction mediated via a1 receptors, increase in total peripheral
   resistance. 2. Skeletal muscle vasculature: vasoconstriction (a1) or vasodilation (B2). B2 activation results in increased blood flow to muscle and an overall decrease in total peripheral resistance.
2. Renal vasculature: Relaxation via D1 dopamine receptors balanced by constriction via a1 receptors.
3. Coronary vasculature: increase blood flow.

Question 17

What effect do adrenergic receptors have on the heart

Answer 17

largely mediated by B1 receptors. 1. SA node: Increase in heart rate (positive chronotropy). 2. AV node: Increase in conduction velocity; refractory period decreased. 3. Atrial and ventricular cardiac muscle: Increase in force of contraction (positive inotropy)

Question 18

What effect do adrenergic receptors have on the blood pressure

Answer 18

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)
a2: Decrease in SNS outflow (via action in CNS) decreases BP

Question 19

Describe activation of baroreceptor reflex arc

Answer 19

Vessels is stretched by increased arterial pressure - inhibits sympathetic discharge from medulla resulting in vasodilation and decreased heart
rate (reflex bradycardia)> decreased arterial pressure - vagus nerve activity also increasedVessels is stretched by increased arterial pressure - inhibits sympathetic discharge from medulla resulting in vasodilation and decreased heart
rate (reflex bradycardia)> decreased arterial pressure - vagus nerve activity also increased

Question 20

Describe relaxation of baroreceptor reflex arc

Answer 20

decrease in arterial pressure “disinhibits” tonic sympathetic discharge and results in SNS-mediated release of norepinephrine at the heart (1 receptors > reflex tachycardia) and blood vessels (1 receptors > vasoconstriction) that produces an increase in arterial blood pressure

Question 21

Describe the renin angiotensin aldosterone system

Answer 21

decrease in renal blood flow > release of renin from the kidney > formation of angiotensin II > release
of aldosterone from adrenal cortex > retention of Na+ and water > increase in vascular volume and
blood pressuredecrease in renal blood flow > release of renin from the kidney > formation of angiotensin II > release
of aldosterone from adrenal cortex > retention of Na+ and water > increase in vascular volume and
blood pressure

Question 22

What effect do adrenergic receptors have on the kidney

Answer 22

Increased release of renin via NE acting on B1 receptors on juxtoglomerular cells, ultimately
resulting in vasoconstriction, fluid retention (via aldosterone) and increased BP.

Question 23

What effect do adrenergic receptors have on the respiratory tract

Answer 23

Bronchial smooth muscle: Relaxation and bronchodilation via B2 receptors

Question 24

What effect do adrenergic receptors have on the eye

Answer 24

Pupil dilation (mydriasis) by a1 receptors, Increased production of aqueous humor via B2 receptors, increased outflow of humor by A1

Question 25

What effect do adrenergic receptors have on the GI tract

Answer 25

Indirect relaxtion via a2, direct relaxation by B2

Question 26

What effect do adrenergic receptors have on genitourinary tract

Answer 26

Uterine smooth muscle: Relaxation via B2 receptors. Uretal sphincter, bladder base, prostate: Contraction via a1 receptors to promote continence. Bladder wall musculature: Relaxation via B3 receptors promoting urinary continence. Ejaculation: Via a1 receptor activation in vas deferens, seminal vesicles, and prostate

Question 27

What effect do adrenergic receptors have on skeletal muscle

Answer 27

Action on contractile proteins via B2 receptors > marked tremor

Question 28

What effect do adrenergic receptors have on skeletal metabolic effects

Answer 28

Liver: increased blood glucose via B2 receptors (glycogenolysis). Fat cells: Increased lipolysis (fat breakdown) via B3 receptors. Pancreas Beta cells: Decreased insulin secretion via a2 receptor (major effect) or increased insulin
release via B2 receptors