Peripheral Nervous System Anatomy and Physiology [5]

Question 1

Describe the anatomical projections of the sympathetic and parasympathetic autonomic nervous system and the central control of the autonomic nervous system

Answer 1

x

Question 2

Discuss the concept of “tone” and explain the consequences of the fact that parasympathetic tone predominates at most organs and tissues (exception: sympathetic control of blood vessels)

Answer 2

“Tone” refers to which action predominates based on which component of the nervous system exerts a greater affect at a particular organ. Parasympathetic tone is associated with a state of “rest and digest.” (reduced HR, bronchial smooth muscle constriction, increased GI activity, increased motility of GU system, increased salivation)

Question 3

Somatic neurotransmitters and receptors

Answer 3

NT: Acetylcholine

Recptors: Muscle-type nicotinic cholinergic receptors (nAChRs)–ionotropic receptors

Question 4

Parasympathetic neurotransmitters and receptors

Answer 4

NT: Preganglionic: acetylcholine

Postganglionic: acetylcholine

Receptors: Postganglionic: neuronal-type nicotinic cholinergic receptors (nAChRs)–ionotropic receptors

End organ: muscarinic cholinergic receptors (MRs)–GPCRs

Question 5

Sympathetic neurotransmitters and receptors

Answer 5

NT: Preganglionic: acetylcholine

Postganglionic: norepinephrine

Receptors: Postganglionic: neuronal-type nicotinic cholinergic receptors (nAChRs)–ionotropic receptors

End organ: alpha- or beta-adrenergic receptors—GPCRs

Question 6

From which neurons is Acetylcholine released from?

Answer 6

Cholinergic neurons

Question 7

From which neurons is Norepinephrine released from?

Answer 7

Adrenergic neurons

Question 8

What receptors does acetylcholine interact with?

Answer 8

Cholinergic receptors (nicotinic [N] and muscarinic [M] subtypes)

Question 9

What receptors does norepinephrine interact with?

Answer 9

Adrenergic receptors (alpha [α] and beta [β] subtypes)

Question 10

Describe the preganglionic neurons of the Parasympathetic nervous system

Answer 10

Preganglionic neurons release ACh
At the GANGLIA, acetylcholine interacts with the NICOTINIC CHOLINERGIC receptors

(this the same as SNS)

Question 11

Describe the postganglionic neurons of the Parasympathetic system

Answer 11

Postganglionic neurons release ACh

A the END ORGANS acetylcholine interacts with MUSCARINIC CHOLINERGIC receptors (heart, lungs, GI/GU tract, eye)

Question 12

Describe the preganglionic neurons of the Sympathetic nervous system

Answer 12

Preganglionic neurons release ACh
At the GANGLIA, acetylcholine interacts with the NICOTINIC CHOLINERGIC receptors

(thi sis the same as PNS)

Question 13

Describe the postganglionic neurons of the Sympathetic nervous system

Answer 13

Postganglionic neurons release….

1. NOREPINEPHRINE at the EFFECTOR organs, which interaction with Alpha1-adrenergic (blood vessels, eye, GI tract) and Beta-adrenergic (B1 on heart, B2 on smooth muscle)
2. ACETYLCHOLINE at SWEAT GLANDS which interacts with muscarinic cholinergic receptors
3. DOPAMINE at the KIDNEY vascular smooth muscle with interacts with dopamine receptors

Question 14

On what organs would you find Nicotinic cholinergic receptors?

Answer 14

Voluntary skeletal muscle at the neuromuscular junction

Question 15

On what organs would you find Muscarinic cholinergic receptors?

Answer 15

Heart, lungs, GI/GU tract, eye

Question 16

On what organs would you find Alpha1 adrenergic receptors?

Answer 16

Blood vessels, eye, GI tract

Question 17

On what organs would you expect to find Beta adrenergic receptors?

Answer 17

B1- heart

B2- smooth muscle

Question 18

Do most organs have single or dual innervation? What is the exception?

Answer 18

Most organs are DUALLY innervated

However, blood vessels receive sympathetic innervation only

Question 19

Which branch of the autonomic nervous systems exerts predominant control over organs? What is the exception?

Answer 19

Predominant control is almost always exerted by the PARASYMPATHETIC branch

However, control of the vascular tone is done by the sympathetic branch

Question 20

What are the physiologic actions of the Parasympathetic nervous system?

Answer 20

“Rest and Digest”

• Slowing of HR&raquo_space; lowered BP
• GI motility and secretions, increased nutrient absorption
• Emptying of bladder and rectum (bladder muscle contract)
• Miosis (pupil constriction), focus for near vision

Question 21

What are the physiologic actions of the Sympathetic nervous system?

Answer 21

“Fight or Flight”

• Accelerated heart rate&raquo_space; rise in blood pressure
• Shift in blood flow from skin and splanchnic regions to skeletal muscles
• Rise in blood glucose
• Dilation of bronchioles and pupils
• Decrease in activity of GI and GU systems

Question 22

Effects mediated by muscarinic receptors [M] at postganglionc effector organs

Answer 22

1. Cardiovascular: decrease HR and AV conduction rate (vasodilation is an indirect effect and not a result of the PNS)
2. Respiratory: bronchial muscle contraction
3. GI: increase in secretory and motor activity, sphincters relaxed
4. GU: relax sphincters, contract detrusor muscle
5. Eye: miosis, focus for near vision, outflow of aqueous humor

Question 23

Effects mediated by nicotinic neuronal receptors [Nn] at autonomic ganglia

Answer 23

1. Cardiovascular: chiefly SYMPATHETIC effects; vasoconstriction, tachycardia, elevated BP)
2. GI/GU tract: PARASYMPATHETIC effects (nausea, vomiting, diarrhea, vomiting)

Question 24

Where are the Adrenergic receptor subtypes located?

Answer 24

At the sympathetic postganglionic synapses on effector organs or nerve terminals

Question 25

Physiologic effects of adrenergic receptors on vasculature

Answer 25

• Effects mediated by Alpha1 (vasoconstriction) and B2 (vasodilation)
• Vasoconstriction of cutaneous, mucus membranes, and splanchnic vasculature
• Decrease in total peripheral resistance in skeletal muscle
• Renal vasculature: Relaxation of D1 dopamine receptors balanced by constriction via Alpha1
• Increased blood flow in coronary vasculature

Question 26

Physiologic effects of adrenergic receptors on the heart

Answer 26

• Effects mediated by Beta1 receptors (some A1 and B2 also)
• SA node: increased HR (positive chronotropy)
• AV node: increase in conduction velocity
• Atrial and ventricular cardiac muscle have increase in force of contraction (positive iontropy)