Autonomic Nervous System

Question 1

Describe general characteristics of the autonomic nervous system, and describe and compare the general functions of the sympathetic and parasympathetic systems.

Answer 1

The ANS can change visceral function rapidly and intensely:
•Heart rate can be increased to twice normal within 3-5 seconds.
•Arterial pressure can be doubled within 10 to 15 seconds.
•Sweating can begin within seconds.

Generalizations Regarding ANS:
•Terminal ends of these fibers usually have enlarged varicosities where neurotransmitter and large numbers of mitochondria are stored.
•The efferent activity of the ANS is largely regulated by reflexes (not spinal reflexes).
•ANS pathways consist of two neurons in sequence: Preganglionic neuron and Postganglionic neuron

Question 2

Compare the basic morphological pattern of the sympathetic and parasympathetic systems.

Answer 2

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Question 3

Describe the thoracic sympathetic chain and the ganglia and splanchnic nerves associated with it.

Answer 3

Lies against neck of ribs and costovertebral junctions

12 thoracic ganglia pairs: •
First one often fused with inferior cervical ganglion going to head: •Referred to as stellate ganglion collectively 
•T2 to neck 
•T3-6 to thorax 
•T7-11 to abdomen 
•T12-L2 to LE

Splanchnic Nerves
-greater, lesser, least, lumbar
•Composed of preganglionic fibers and visceral sensory fibers.
•Supply abdominal viscera.
•Synapse in prevertebral ganglia.
•All preganglionic neurons are cholinergic.

Question 4

Describe the input and outputs of the adrenal medullae; explain why circulating norepinephrine has a greater effect on raising arterial pressure.

Answer 4

stimulated by sympathetic system
secrete epi and norepi hormone

Circulating norepinephrine:
•Constricts most of blood vessels of body:
•Has greater effect on blood vessels in skeletal muscles so has greater effect on raising arterial pressure
•Increases heart activity
•Inhibits GI tract
•Dilates pupil

Question 5

Identify structures innervated by the vagus nerve; identify the branches of the vagus nerve.

Answer 5

esophagus and thoracic viscera

• Cardiac branches to cardiac plexus
• Pulmonary branches to pulmonary plexus
• Esophageal branches to esophageal plexus
• Left recurrent laryngeal nerve from left vagus
• Right recurrent laryngeal nerve from right vagus

Question 6

Identify the four cranial nerves that carry parasympathetic fibers and what they innervate.

Answer 6

Oculomotor Nerve (CN III)
Facial Nerve (CN VII)
Glossopharyngeal Nerve (CN IX)
Vagus Nerve (CN X)

Question 7

Identify the four cranial nerves that carry parasympathetic fibers and what they innervate.

Answer 7

Oculomotor Nerve (CN III)
-skeletal muscles of eyes, constricts pupil and ciliary muscles
Facial Nerve (CN VII)
-primary nerve to muscles of expression, inner ear, sensation of taste anterior 2/3 tongue, stimulates submandibular glands to increase salvia, stimulates nasal mucosa
Glossopharyngeal Nerve (CN IX)
-sensation and taste from rear tongue, skeletal muscle stylopharyngeus, injury impairs swallowing
Vagus Nerve (CN X)

Question 8

Preganglionic neuron:

Answer 8

• Cell bodies are located within CNS
• Axons are myelinated
• Neurotransmitter is ACh

Question 9

Postganglionic neuron

Answer 9

• Cell bodies are located in peripheral ganglia
• Axons are not myelinated

Neurotransmitter is:
•ACH in parasympathetic system
•Norepinephrine (usually) in sympathetic system

Question 10

Vagus Nerve Dysfunction

Answer 10

• Irritable bowel syndrome
• Anxiety
• Depression
• High or low heart rate
• Difficulty swallowing
• Esophageal reflux
• Migraines (association)
• Anxiety disorders

Question 11

List the adrenergic receptors and list what they are associated with.

Answer 11

Alpha (alpha1and alpha2):
•Norepinephrine excites mainly alpha receptors but also beta receptors to a lesser extent.
•Epinephrine excites both alpha and beta almost equally.
•Certain alpha receptors are excitatory; others are inhibitory
•Alpha receptors are associated with the following:
•Vasoconstriction •Iris dilation
•Intestinal relaxation
•Intestinal sphincter contraction
•Pilomotor contraction
•Bladder sphincter contraction
•Inhibition of neurotransmitter release (alpha2
Beta receptors
beta1
•Cardioacceleration
•Increased myocardial strength
•lipolysis

beta2 •Vasodilation 
•Intestinal relaxation 
•Uterus relaxation 
•Bronchodilation 
•Calorigenesis 
•Glycogenolysis 
•Bladder wall relaxation 

beta3 •Thermogenesis

Question 12

Describe the synthetic pathways for acetylcholine and norepinephrine.

Answer 12

Acetyl-CoA + Choline → Acetylcholine → choline + acetate ion

part 1 enzyme is choline acetyl-transferase
part 2 enzyme is acetylcholinesterase

Question 13

Describe the inactivation/removal of acetylcholine and norepinephrine.

Answer 13

broken down into choline and acetate

norepinephrine/epinephrine is active for only a few seconds when secreted by neurons, but when secreted into the blood (via the adrenal medulla) it remains active until destroyed by COMT in surrounding tissues, especially the liver

Question 14

Beta Blockers –Side Effects

Answer 14

• Fatigue
• Hypotension
• Bradycardia
• Associated with negative changes in blood lipid profiles
• Associated with higher glucose and insulin levels

Question 15

Indirect cholinergic drugs:

Answer 15

Inhibit cholinesterase (thus promoting acetylcholine to linger longer

sarin

Question 16

Parasympathomimetic drugs

Answer 16

•Not rapidly destroyed by cholinesterase
•Include pilocarpine
and methacholine
•Act directly on muscarinic receptors

Question 17

Drugs that block cholinergic activity

Answer 17

• Atropine
• Homatropine
• Scopolamine