ANS-SoNS anatomy and physiology

Question 1

Origin of parasympathetic neurons

Answer 1

cranial nerve nuclei and sacral segments of spinal cord (S2-S4)

Question 2

Origin of sympathetic neurons

Answer 2

Thoracic (T1-T12) and lumbar (L1-L5) segments of spinal cord

Question 3

Location of parasympathetic ganglia

Answer 3

innervated organs

Question 4

Location of sympathetic ganglia

Answer 4

2 paravertebral chains along spinal cord (most) or in prevertebral ganglia in the abdomen (some)

Question 5

cholinergic receptor subtypes

Answer 5

nicotinic (N) and muscarinic (M)

Question 6

somatic nervous system neurotransmitter and receptor

Answer 6

acetylcholine (ACh), nicotinic cholinergic receptors

Question 7

PNS neurotransmitters, pre and postganglionic

Answer 7

preganglionic neurons release ACh, which interacts with nicotinic cholinergic receptors. Postganglionic neurons release ACh, which interacts with muscarinic cholinergic receptors.

Question 8

SNS neurotransmitters, pre and postganglionic

Answer 8

pre release ACh, which interacts nicotinic cholinergic receptors. Postganglionic neurons release: norepinephrine at effect organs (alpha adrenergic in blood vessels, eye, GI tract) and beta-adrenergic (beta 1 in heart and smooth muscle but low affinity). acetylcholine at sweat glands (muscarinic cholinergic receptors) and dopamine (at the renal vascular smooth muscle, dopamine receptors).

Question 9

Neurotransmitter(s) released by adrenal medulla

Answer 9

epinephrine (EPI) and some NE that interact with adrenergic synapses with alpha1, beta1, beta2 receptors.

Question 10

ratio of pre- to post-ganglionic neurons in the PNS versus SNS

Answer 10

PNS = ratio is 1:1, which functions in a discrete/localized fashion. SNS = ratio is 1:20-50, which allows SNS to function in a diffuse or widespread manner.

Question 11

Action and regulation of the adrenal medulla

Answer 11

The adrenal medulla is basically a modified sympathetic ganglion. It secretes epinephrine into the circulation.

Question 12

Effects mediated by nicotinic neuronal receptors at autonomic ganglia

Answer 12

cardiovascular: chiefly sympathetic effects (vasoconstriction, tachycardia, elevated Bp). GI/urinary tract: parasympathetic effects (nausea, vomiting, diarrhea, urination).

Question 13

Effect of B1 receptors on heart

Answer 13

chronotropy, positive inotropy, increase in conduction velocity.

Question 14

How is renin released from the kidney?

Answer 14

NE acts on beta1 receptors on juxtoglomerular cells.

Question 15

mechanism for pupillary constriction

Answer 15

alpha1 agonism causes constriction of radial pupillary dilator muscle, causing mydriasis/dilation.

Question 16

aqueous humor mechanism

Answer 16

beta2 receptor agonism causes increased production, which increases IOP. alpha1 receptor agonism causes vasoconstriction, leading to decreased IOP.

Question 17

GI tract regulation

Answer 17

smooth muscle is relaxed via presynaptic alpha2 receptor agonism, which inhibits release of ACh and ACh-mediated muscle contraction. Direct relaxiation is mediated by beta2 receptors on smooth muscle.

Question 18

Uterine smooth muscle control

Answer 18

relaxation via B2 receptors

Question 19

uretal sphincter, bladder base, prostate control

Answer 19

contraction via alpha1 receptors promotes continence

Question 20

bladder wall musculature regulation

Answer 20

relaxation via beta3 receptors promotes continence

Question 21

ejaculation control

Answer 21

alpha1 receptor activation in vas deferens, seminal vesicles, and prostate.

Question 22

tremor, shakiness mechanism

Answer 22

b2 receptor action on contractile proteins

Question 23

glycogenolysis mechanism

Answer 23

beta2 receptor agonism

Question 24

lipolysis in adipose cells mechanism

Answer 24

beta3 receptor agonism

Question 25

insulin control

Answer 25

alpha2 receptor agonism decreases insulin secretion (major effect). beta2 receptor agonism increases insulin release.

Question 26

Effect of different receptor subtypes on blood pressure

Answer 26

alpha1: vasoconstriction (by increasing TPR and BP). beta1: chronotrpy and inotropy increase CO and BP. beta2: vasodilation (decreases TPR and BP). **alpha2: decrease in SNS outflow decreases BP.

Question 27

Outline the baroreceptor reflex arc

Answer 27

stretch receptors in the carotid sinus or aortic sense increased arterial pressure –> synapse with baroreceptor neurons in the spinal cord –> inhibit sympathetic discharge from the medulla resulting in vasodilation and decreased HR (reflex bradycardia) –> decreased arterial pressure. *This reflex also increases vagus (PNS) nerve activity.

Question 28

relaxation of baroreceptor

Answer 28

decrease in arterial pressure disinhibits tonic sympathetic discharge –> NE released in heart -> NE agonism at beta1 receptors causes reflex tachycardia + NE alpha1 agonism at blood vessels causes vasoconstriction –> increaase in arterial BP. *Also decreases vagus nerve action.

Question 29

respiratory tract control

Answer 29

bronchial smooth muscles are relaxed and bronchodilation occurs via beta2 receptors. Upper respiratory tract mucosal blood vessels are constricted via alpha1 receptors.

Question 30

Location of muscarinic receptors

Answer 30

heart, lungs, GI/GU tract, eye

Question 31

what is cycloplegia?

Answer 31

block of accomodation.