ch 15: autonomic nervous system

Question 1

how does the autonomic nervous system operate? give some examples

Answer 1

Operates via reflex arcs to regulate activity of smooth muscle, cardiac muscle &
certain glands, often unconsciously
◦ E.g., Changes in blood pressure, digestive functions, urination, hormone
secretion, etc.

Question 2

what are the components of the reflex arc. explain each

Answer 2

◦ Sensory receptors (mostly interoceptors)
◦ Sensory neurons (from receptor to CNS)
◦ Integrating centers in the CNS (brain stem and hypothalamus)
◦ Motor neurons (2 in series; pre and postganglionic motor neurons)
◦ Visceral effectors (smooth and cardiac muscles, and glands)

Question 3

how is the somatic nervous system different than the autonomic nervous system

Answer 3

in the autonomic nervous system, sensory input isn’t perceived. Different from somatic nervous system, where sensory input is consciously
perceived

Question 4

A reflex arc includes
a) a sensory neuron
b) a motor neuron
c) a sensory receptor
d) an effector
e) all the above

Answer 4

E

Question 5

how is input from the ANS perceived? What senses changes in organs?

Answer 5

The input (afferent) information of the ANS is mostly unconsciously perceived
visceral sensations
◦ Interoceptors
◦ Chemoreceptors (e.g., monitor blood CO2)
◦ Mechanoreceptors (e.g., monitor stretch of blood vessels)
◦ Some from somatic or special senses (e.g., smell, taste, emotions)

Question 6

how are somatic motor pathways and autonomic motor pathways different in terms of motor neurons

Answer 6

Somatic motor pathways = single motor neuron
Autonomic motor pathways consist of two
motor neurons in series

Question 7

pre-ganglionic neuron bs post-ganglionic neuron in the ANS

Answer 7

◦Pre-ganglionic neuron has its cell body in the CNS and its myelinated axon extends to an autonomic ganglion
◦Post-ganglionic neuron has its cell body in the autonomic ganglion and its nonmyelinated
axon extends to an effector

Question 8

structure of parasympathetic branch vs parasympathetic branch in the ANS

Answer 8

Question 9

In the somatic nervous system, lower motor
neurons
a) go directly from the brain to skeletal muscles
b) go directly from the spinal cord to skeletal muscles
c) go directly from skeletal muscles to the spinal cord

Answer 9

b)

Question 10

When a motor neuron synapses onto another
motor neuron, where is the synapse taking place?
a) In white matter
b) In gray matter
c) In nerves in the PNS
d) In ganglia in the PNS
e) B and D

Answer 10

E

Question 11

Which of the following describes BEST what a
ganglion is composed of?
a) bundle of axons in the PNS
b) cell bodies in the PNS
c) cell bodies of sensory neurons in the PNS
d) cell bodies of sensory neurons in the CNS

Answer 11

b)

Question 12

what is dual innervation in the ANS

Answer 12

the sympathetic division and the parasympathetic division generally send
opposite signals
◦ sympathetic input increases heart rate; parasympathetic input decreases
heart rate
◦ Sympathetic input decreases urine production; parasympathetic input
increases urine production
◦ etc.
most organs receive impulses from both sympathetic and parasympathetic
fibers; this is called dual innervation

Question 13

why are we not aware of autonomic responses

Answer 13

Not aware of autonomic responses because control center is in lower regions of
the brain (not in cerebral cortex)

Question 14

how is the hypothalamus a major control center in the ANS
]
what is the input and output and how do signals travel

Answer 14

Hypothalamus is major control center
◦ Input: Emotions and visceral sensory information
◦ Output: To nuclei in brainstem and spinal cord
◦ From there, preganglionic neurons emerge
* Different nuclei in hypothalamus control different
functions (some sympathetic, some parasympathetic)
* Hypothalamus regulates balance between sympathetic
and parasympathetic activity levels = autonomic tone

Question 15

what is autonomic tone

Answer 15

when the hypothalamus regulates balance between sympathetic and parasympathetic activity levels

Question 16

in what situation is the sympathetic nervous system activated

Answer 16

emergency, embarrassment, excitement

Question 17

what are the different ways the sympathetic nervous system acts in a fight or flight repsonse

Answer 17

Dilation of pupils
◦ Increase of heart rate, force of contraction, and blood pressure
◦ Decrease in blood flow to non-essential organs (kidney, GI)
◦ Increase in blood flow to skeletal and cardiac muscle
◦ Airways dilate and respiratory rate increases
◦ Blood glucose level increases

Question 18

why is the sympathetic nervous system response long-lasting and widespread?

Answer 18

Long-lasting and widespread due to
◦ Divergence of postganglionic axons
◦ Lingering of norepinephrine in synaptic cleft
◦ Release of norepinephrine by the adrenal gland
main reason is hormones are making it last longer

Question 19

when is the parasympathetic system more dominant? what activities/responses does it enhance?

Answer 19

Enhance “rest-and-digest” activities
Mechanisms that help conserve and restore body energy

Enhance “SLUDD” type responses
◦ Salivation, Lacrimation, Urination, Digestion & Defecation
3 “decreases”→ decreased HR, diameter of airways and diameter of pupi

Question 20

The definition of autonomic tone is:
a) The communication between the
autonomic nervous system and the
somatic nervous system
b) The balance between sympathetic
and parasympathetic activity
c) The constant slight contraction seen
in skeletal muscles
d) That most organs are innervated by
both sympathetic and
parasympathetic nerve fibres

Answer 20

B

Question 21

Which of the following effects does not occur
during the fight-or-flight response?
a) The pupils constrict
b) The airways increase in diameter
c) Blood vessels to skeletal muscles dilate
d) Blood pressure increases

Answer 21

a) the pupils constrict (because part of sympathetic nervous system)

Question 22

where are the cell bodies of pre and post-ganglionic motor neurons?

Answer 22

The cell bodies of the pre-ganglionic
neurons are in the lateral gray horns of the
spinal cord
◦ T1-L2
◦ 12 thoracic; 2 lumbar
◦ Thoracolumbar division

Question 23

where are the ganglia found in the ANS. also what do they do?

Answer 23

Ganglia are the site of synapse between
preganglionic and postganglionic neurons
Trunk (chain) ganglia lie on either side of the spinal cord
◦ Postganglionic neurons innervate organs above
diaphragm
Pre-vertebral ganglia lie anterior to spinal cord
◦ Postganglionic neurons innervate organs below
diaphragm
Postganglionic neurons have many axon collaterals
(20+!)
◦ One axon affects many organs

Question 24

describe trunk ganglia

Answer 24

Trunk (chain) ganglia lie on either side of spinal cord
◦ Postganglionic neurons innervate organs above
diaphragm

Question 25

describe pre-vertebral ganglia

what organs do they innervate?

Answer 25

Pre-vertebral ganglia lie anterior to spinal cord
◦ Postganglionic neurons innervate organs below
diaphragm

Question 26

true or false one axon affects many organs

Answer 26

true

Question 27

what are the 4 different options that sympathetic pre-ganglionic neurons can do?

Answer 27

1. May synapse with postganglionic neurons in
   the chain ganglia at the same level
2. May synapse with postganglionic neurons in
   a ganglion higher up or lower down the
   chain
3. May pass through the chain and synapse
   with a postganglionic neuron in a pre
   vertebral ganglion
4. May go to adrenal medulla

Question 28

In the sympathetic ANS
a) preganglionic neurons end in sympathetic ganglia
b) preganglionic neurons synapse with postganglionic neurons in
ganglia
c) postganglionic neurons have their cell bodies in sympathetic
ganglia
d) a and b
e) a, b and c

Answer 28

E

Question 29

Postganglionic neurons from the trunk ganglia
a) innervate sympathetic ganglia
b) innervate sympathetic organs
c) innervate organs above the diaphragm
d) innervate organs below the diaphragm

Answer 29

C

Question 30

what do postganglionic neurons from the cervical ganglia innervate?

Answer 30

Postganglionic neurons from the cervical
ganglia innervate the head (sweat, lacrimal,
nasal, salivary glands, pupil and lens, face)
and the heart

Question 31

what do postganglionic neruons of the thoracic ganglia innervate?

Answer 31

Postganglionic neurons of the thoracic
ganglia innervate the heart, lungs,
bronchi, skin (glands, arrector pili)

Question 32

what do postganglionic neurons from the celiac ganglion innervate?

Answer 32

stomach, spleen, liver kidney and small intestine

Question 33

what do postganglionic neurons from the renal ganglion innervate?

Answer 33

the kidneys and ureters

Question 34

what do postganglionic neurons from the superior mesenteric ganglion innervate?

Answer 34

the small intestine and the colon

Question 35

what do postganglionic neurons from the inferior mesenteric ganglion innervate?

Answer 35

colon, rectum, bladder and genital organs

Question 36

what is the benefit of haveing sympathetic preganglionic neurons also extend to the adrenal medulla

Answer 36

instead of having postganglionic neurons, the adrenal medulla releases hormones (epinephrine and norepinephrine)

Question 37

In the sympathetic ANS
a) preganglionic neurons end in sympathetic ganglia
b) preganglionic neurons synapse with postganglionic neurons in
ganglia
c) postganglionic neurons have their cell bodies in sympathetic
ganglia
d) a and b
e) a, b and c

Answer 37

E

Question 38

where are the preganglionic cell bodies of the parasympathetic nervous system found?

Answer 38

Preganglionic cell bodies found in
◦ 4 cranial nerve nuclei in
brainstem (CN III, VII, IX, X)
◦ S2 to S4 spinal cord
Axons emerge as part of a cranial
nerve or as part of the anterior root
of a spinal nerve

Question 39

pre-ganglionic axons extend from brains stem in 4 CNs. What are those cranial nerves?

Answer 39

Pre-ganglionic axons extend from brain stem in 4 CNs
◦ Oculomotor nerve (CN III)
◦ Ciliary muscle (lens) and pupillary constrictor muscle of iris
◦ Facial nerve (CN VII)
◦ Tears, salivary (submandibular and sublingual glands), nasal secretions
◦ Glossopharyngeal (CN IX)
◦ Parotid salivary glands
◦ Vagus nerve (CN X)
◦ Heart, airways, liver, gallbladder, stomach, pancreas, small intestine, colon

Question 40

describe the pre-ganglionic cell bodies and pre-ganglionic axons

Where the they found and what do they do?

Answer 40

Pre-ganglion cell bodies in S2-S4 segments of SC
Pre-ganglionic axons in anterior roots of S2-S4
◦ Form pelvic splanchnic nerves

Question 41

what are terminal ganglia

Answer 41

ALL (cranial and sacral) preganglionic neurons end
in terminal ganglia
◦ Located in walls of target organs
◦ Colon, ureters, bladder & reproductive organs

Question 42

where are the parasympathetic ganglia located and what are they called. What do those ganglia contain?

Answer 42

The parasympathetic ganglia are
located very near or in the wall of
the target organs. The are called
terminal ganglia.

Those ganglia contain the cell
bodies of parasympathetic
postganglionic neurons. Axons of
postganglionic neurons are short,
and unmyelinated.

Question 43

describe the preganglionic neurons in S2-S4

What do they form and what do they synapse with

Answer 43

Preganglionic neurons in S2-S4 spinal nerves branch off to
form the pelvic splanchnic nerves. They synapse with
postganglionic neurons in terminal ganglia which are in
walls of target organs (colon, ureters, bladder &
reproductive organs)

Question 44

describe cholinergic neurons?

Which ones are the cholineric neurons

Answer 44

Cholinergic neurons release acetylcholine (ACh):
◦all preganglionic neurons are cholinergic
neurons
◦all parasympathetic postganglionic neurons
◦a few sympathetic postganglionic neurons (to
most sweat glands)

Question 45

what does acetylcholine cause (ACh)

Answer 45

ACh can cause excitation or
inhibition of the postsynaptic cell,
depending upon the cell type and
receptor subtype

Question 46

what are cholinergic receptors and what are the 2 types

Answer 46

Cholinergic receptors are integral membrane proteins in the postsynaptic
plasma membrane.
The two types of cholinergic receptors are nicotinic and muscarinic:

Question 47

what does the activation of nicotinic receptors cause? where are they found?

Answer 47

Activation of nicotinic receptors causes excitation of the postsynaptic cell.
◦ Nicotinic receptors are found on dendrites & cell bodies of autonomic NS
cells (and at NMJ)

Question 48

what does the activation of muscarinic receptors cause? Where are they found?

Answer 48

Activation of muscarinic receptors can cause either excitation or inhibition
depending on the cell that bears the receptors.
◦ Muscarinic receptors are found on plasma membranes of all
parasympathetic effectors

Question 49

adrenergic neurons release what? which ones are adrenergic neurons

Answer 49

Adrenergic neurons release
norepinephrine (NE):
Only sympathetic postganglionic
neurons are adrenergic neurons

Note: NE can cause excitation or
inhibition of the postsynaptic cell,
depending upon the receptor subtype

Question 50

describe the different adrenergic neurons and receptors

Answer 50

Norepinephrine is released as a neurotransmitter and as a hormone;
epinephrine is released as a hormone
◦ Both bind to adrenergic receptors
The main types of adrenergic receptors are alpha and beta receptors.
These receptors are further classified into subtypes.
◦ A1 and B1 receptors generally produce excitation
◦ A2 and B2 receptors generally cause inhibition
◦ B3 receptors (brown fat) increase thermogenesis

Question 51

true or false the effects triggered by adrenergic neurons typically are shorter lasting than those triggered by cholinergic receptors

Answer 51

false

Effects triggered by
adrenergic neurons typically
are longer lasting than those
triggered by cholinergic
neurons

Question 52

Which statement is false in reference to the
autonomic ganglia?
a) The sympathetic chain ganglia lie close to the vertebrae on each
side
b) The terminal ganglia lie near the bellies of skeletal muscles
c) The sympathetic preganglionic fibers of the sympathetic chain
are very short
d) The terminal ganglia are parasympathetic ganglia

Answer 52

B