Lecture Exam 2 - Chapter 15 Study Guide

Question 1

What are the three major branches of the peripheral nervous system?

Answer 1

a) Somatic nervous system
b) Autonomic nervous system
c) Enteric nervous system

Question 2

Know major features of somatic and autonomic nervous system (Table 15.1).
How do they differ with respect to sensory input?

Answer 2

Somatic Nervous System: Somatic senses and special senses.

Autonomic Nervous System: Maintly from interoceptors; some from somatic senses and special senses.

Question 3

Know major features of somatic and autonomic nervous system (Table 15.1).
How do they differ with respect to control of motor output?

Answer 3

Somatic Nervous System: Voluntary control from cerebral cortex, with contributions from basal ganglia, cerebellum, brain stem, and spinal cord.

Autonomic Nervous System: Involuntary control from hypothalamus, limbic system, brain stem, and spinal cord; limited control from cerebral cortex.

Question 4

Know major features of somatic and autonomic nervous system (Table 15.1).
How do they differ with respect to motor neuron pathway?

Answer 4

Somatic Nervous System: One-neuron pathway: Somatic motor neurons extending from CNS synapse directly with effector.

Autonomic Nervous System: Usually two-neuron pathway: Preganglionic neurons extending from CNS synapse with postganglionic neurons in an autonomic ganglion, and postganglionic neurons extending from ganglion synapse with a visceral effector. Alternately, preganglionic neurons may extend from CNS to synapse with chromafin cells of adrenal medullae.

Question 5

Know major features of somatic and autonomic nervous system (Table 15.1).
How do they differ with respect to neurotransmitters released?

Answer 5

Somatic Nervous System: All somatic motor neurons release ACh.

Autonomic Nervous System: All sympathetic and parasympathetic preganglionic neurons release ACh. Most sympathetic postganglionic neurons release norepinephrine; those to most sweat glands release ACh. All parasympathetic postganglionic neurons release ACh. Chromaffin cells of adrenal medullae release epinephrine and norepinephrine.

Question 6

Know major features of somatic and autonomic nervous system (Table 15.1).
How do they differ with respect to effector responses stimulated?

Answer 6

Somatic Nervous System: Effectors – Skeletal muscle. Responses – contraction of skeletal muscle.

Autonomic Nervous System: Effectors – Smooth muscle, cardiac muscle, and glands. Responses – Contraction or relaxation of smooth muscle; increased or decreased rate and force of contraction of cardiac muscle; increased or decreased secretion of glands.

Question 7

What is meant by the term preganglionic autonomic neuron?

Answer 7

Autonomic motor pahtways usually require two neurons to reach the target tissue. The first neuron is called the preganglionic neuron, and it always releases ACh.

The preganglionic neuron usually synapses with a postganglionic neuron in an autonomic ganglion.

Question 8

What is meant by the term postganglionic autonomic neuron?

Answer 8

The preganglionic neuron usually synapses with a
postganglionic neuron in an autonomic ganglion.

(Exception - in the adrenal medulla the preganglionic neuron terminates directly on medullary cells - i.e. only one neuron to reach
target cell)

The postganglionic neuron may release NE or ACh. From the adrenal medulla it is always NE.

Question 9

Where are the sympathetic preganglionic neuron cell bodies?

Answer 9

Preganglionic neurons have cell bodies in the lateral
horns of gray matter in T1-T12 and L1& L2-
sometimes also L3.

Question 10

Where do the axons exit the spinal cord (for the sympathetic ANS)?

Answer 10

Axons emerge through the anterior root of the spinal

cord.

Question 11

What are the names of the two groups of sympathetic ganglia? Name some of the specific ganglia as indicated in lecture.

Answer 11

Sympathetic ganglia are the sites of synapse
between sympathetic preganglionic neurons
and sympathetic postganglionic neurons.

Two groups of sympathetic ganglia:

Sympathetic Trunk Ganglia – These are near the spinal cord - therefore most of the preganglionic axons are short. Mostly innervate organs above the diaphragm. In the neck - superior, middle and
inferior cervical ganglia, the rest do not have specific names.

Prevertebral Ganglia – Lie close to large abdominal arteries. Generally innervate organs below diaphragm.

5 major prevertebral ganglia:
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
Aorticorenal ganglion
Renal ganglion

Question 12

What parts of the body do the sympathetic nerves that pass through each ganglia innervate?

Answer 12

Sympathetic trunk ganglion – mostly organs above the diaphragm.

Prevertebral ganglia - generally inervate organs below the diaphragm.

Question 13

What neurotransmitter is released by preganglionic sympathetic neurons?

Answer 13

Acetylcholine

Question 14

What neurotransmitter is released by postganglionic sympathetic neurons (note that the
sympathetic innervation of most sweat glands is an exception)?

Answer 14

Most sympathetic postganglionic neurons are adrenergic.

Norepinephrine is released as a neurotransmitter from postganglionic neurons and as a hormone from the adrenal medulla

Postganglionic neurons of sweat glands release acetylcholine for the activation of muscarinic receptors.

Question 15

What receptors are present on the dendrites of postganglionic sympathetic neurons in the
ganglia?

Answer 15

Cholinergic Receptors: Muscarinic and Nicotinic

Question 16

One endocrine gland is innervated directly by preganglionic sympathetic neurons. Which gland
is this? Which part of the gland?

Answer 16

Adrenal gland (Adrenal Medulla)

The preganglionic neuron usually synapses with a postganglionic neuron in an autonomic ganglion. Exception - in the adrenal medulla the preganglionic neuron terminates directly on medullary cells (i.e. only one neuron to reach target cell)

Question 17

One endocrine gland is innervated directly by preganglionic sympathetic neurons. Which gland
is this? Which part of the gland? What hormones are released by these endocrine cells? What is
the name of the endocrine cells?

Answer 17

Adrenal gland (Adrenal Medulla)

The preganglionic neuron usually synapses with a postganglionic neuron in an autonomic ganglion. Exception - in the adrenal medulla the preganglionic neuron terminates directly on medullary cells (i.e. only one neuron to reach target cell)

Norepinephine and epinephrine are relased by the adrenal gland.

Chromaffin cells of the adrenal medulla are analogous to post-ganglionic neurons; the adrenal medulla develops in tandem with the sympathetic nervous system and acts as a modified sympathetic ganglion. Within this endocrine gland, pre-ganglionic neurons synapse with chromaffin cells, stimulating the chromaffin to release norepinephrine and epinephrine directly into the blood.[6]

Question 18

Where are the preganglionic parasympathetic neuron cell bodies?

Answer 18

Preganglionic neurons have cell bodies in the nuclei

in the brain stem and in the lateral horns of S2-S4.

Question 19

Where do the axons exit the spinal cord (in the parasympathetic ANS)?

Answer 19

Axons emerge through the anterior root of the spinal

cord or as part of cranial nerves.

Question 20

What is the name for the one class of parasympathetic ganglia? Name the individual ganglia where specified.

Answer 20

Synapse with postganglionic neurons in terminal
ganglia.

Longer axons than sympathetic preganglionic
axons.

Those in head have specific names - learn names
from figure. Remaining terminal ganglia do not
have names.

Named ganglia:
Ciliary ganglion - eye
pterygopalatine ganglion - muscous membrane of nose and palate. lacrimal cland
Submandibular ganglion - sublingual and submandibular glands.
Otic ganglion - Parotid gland

Question 21

What neurotransmitter is released by preganglionic parasympathetic neurons?

Answer 21

All preganglionic neurons—both sympathetic and parasympathetic—release acetylcholine and stimulate nicotinic receptors on postganglionic neurons

Question 22

What neurotransmitter is released by postganglionic parasympathetic neurons?

Answer 22

ACh

Question 23

What receptors are present on the dendrites of postganglionic sympathetic neurons in the
ganglia?

Answer 23

Cholinergic - Muscarinic and Nicotinic

Question 24

What is meant by the term autonomic plexus?

Answer 24

Axons in ANS form tangled networks
called autonomic plexuses - lie alongside
major arteries.

Question 25

What neurotransmitter is released by cholinergic neurons?

Answer 25

Acetylcholine

Question 26

What classes of receptors bind ACh?

Answer 26

Cholinergic

Question 27

Where is each class of ACh receptor located?

Answer 27

Nicotinic Receptors: Named because nicotine (from tobacco) mimics the effect of ACh binding to nicotinic receptors. Present in membranes of dendrites and cell bodies of parasympathetic and sympathetic neurons. Also on motor end plates at neuromuscular junction.

Muscarinic Receptors: Named because a mushroom poison named muscarine mimics action of acetylcholine at muscarinic receptors. Present in smooth muscle, cardiac muscle and glands receiving parasympathetic innervation. Sweat glands receiving sympathetic innervation possess muscarinic receptors.

Question 28

Are the receptors for ACh located on the plasma membrane or inside the cell?

Answer 28

on the plasma membrane

If a ligand is lipid insoluble it cannot pass
through a membrane. The receptor must be an
integral membrane protein. Therefore lipid
soluble ligands such as steroids have receptors
inside the cell.
Acetylcholine and norepinephrine are not lipid
soluble. Therefore their receptors are integral
membrane proteins and the ligand binds on the
outer membrane cell surface.

Question 29

What neurotransmitter is released by Adrenergic neurons?

Answer 29

Adrenergic neurons release norepinephrine or epinephrine.

Question 30

What do Adrenergic receptors bind?

Answer 30

Adrenergic receptors bind both norepinephrine and epinephrine (adrenalin)

Question 31

What are the symbols for the different classes of adrenergic receptors?

Answer 31

Two main types of adrenergic receptors, α
and β.

Further sub-divided into α1, α2, β1, β2, β3.

Receptor sub-types have different affinities
(strength of binding) for NE and E and
initiate different signaling cascades.

Question 32

Are adrenergic receptors located on the plasma membrane or inside the cell?

Answer 32

on the plasma membrane

(If a ligand is lipid insoluble it cannot pass
through a membrane. The receptor must be an
integral membrane protein. Therefore lipid
soluble ligands such as steroids have receptors
inside the cell.
Acetylcholine and norepinephrine are not lipid
soluble. Therefore their receptors are integral
membrane proteins and the ligand binds on the
outer membrane cell surface.)

Question 33

How is acetylcholine activity terminated in the synaptic cleft?

Answer 33

broken down by the enzyme acetylcholinesterase

Question 34

How is norepinephrine activity terminated in the synaptic cleft?

Answer 34

Activity of NE at synapse terminated by:

1) Re-uptake into presynaptic neuron.
2) Enzyme degradation by the enzymes, catechol Omethyl transferase (COMT) and monoamine oxidase (MAO).

NE stays in synaptic cleft longer than ACh so
duration of action longer.

Question 35

Which neurotransmitter activity is terminated faster than the other, norepinephrine or acetylcholine?

Answer 35

ACh is terminated faster than NE

Question 36

What is a receptor agonist?

Answer 36

Agonist - binds to a receptor and mimics

the response of the natural ligand.

Question 37

What is a receptor antagonist?

Answer 37

Antagonists - binds to a receptor and

blocks the response of the natural ligand.

Question 38

For what type of receptor is phenylephrine an agonist? What is this agonist used for as a
medication?

Answer 38

Phenylephrine - adrenergic α1 agonist used in cold and sinus medications - constricts blood vessels in nasal sinuses.

Question 39

For what type of receptors is atropine an antagonist? How is this antagonist
used as medication?

Answer 39

Atropine- antagonist at muscarinic ACh receptors -
dilates pupils, reduces glandular secretions, relaxes
smooth muscle in GI. Used to dilate pupils in eye
examines.

Question 40

What is the difference between propranolol and more recent members of
this class of drugs?

Answer 40

Propranlol blocked was an antagonist for all beta-adrenergic receptors so it had unfortunate side effects (e.g. low blood pressure) from blocking β2 receptors as well.

Specific β1 blockers now available (e.g. metoprolol).

Question 41

What is meant by the term autonomic tone?

Answer 41

Most organs receive innervation from both sympathetic and parasympathetic branches of autonomic NS.

Balance between the two called “autonomic tone”. Regulated by hypothalamus.

Some organs receive only sympathetic innervation.

Question 42

What is the general profile of a sympathetic response?

Answer 42

Dominance by the sympathetic system is caused by physical or emotional stress – “E situations”
– emergency, embarrassment, excitement, exercise

• Alarm reaction = flight or fight response
– dilation of pupils
– increase of heart rate, force of contraction & BP
– decrease in blood flow to nonessential organs
– increase in blood flow to skeletal & cardiac muscle
– airways dilate & respiratory rate increases
– blood glucose level increase

Question 43

What is the general profile of a parasympathetic response?

Answer 43

Enhance “rest-and-digest” activities
• Mechanisms that help conserve and restore body
energy during times of rest
• Normally dominate over sympathetic impulses

SLUDD type responses = salivation, lacrimation,
urination, digestion & defecation and 3 “decreases”— decreased HR, diameter of airways and diameter of pupil
• Paradoxical fear when there is no escape route or no way to win
– causes massive activation of parasympathetic division
– loss of control over urination and defecation

Question 44

For what type of receptors is propranolol an antagonist? How is this antagonist used as medication?

Answer 44

Propranolol - nonselective beta-adrenergic antagonist (beta-blocker). Prescribed for hypertension to decrease force and rate of heart contraction (β1 response). Side effects due to blockade of β2 receptors e.g. low blood
, vasoconstriction) . Specific β1 blockers now available (e.g. metoprolol).