HS2-1 ANS in the Neck

Question 1

What are the target tissues of the autonomic nervous system? (3)

Answer 1

cardiac muscle

smooth muscle

glandular epithelium (glands)

Question 2

(T/F) The nerves of the autonomic nervous system are the only source of innervation for smooth muscle, cardiac muscle, and glandular epithelium.

Answer 2

True. The ANS is the only source of innervation for these tissues.

Question 3

What are general visceral afferent nerves?

Answer 3

afferent (as opposed to efferent) nerves that travel with the peripheral components of the ANS

Question 4

What are the three divisions of the ANS?

Answer 4

sympathetic

parasympathetic

enteric

Question 5

Draw a diagram showing the synaptic organization of the ANS. Label the sympathetic and parasympathetic divisions, along with their associated neurotransmitters.

Answer 5

Question 6

The terms “presynaptic” and “synaptic” are commonly used to describe the organization of the ANS in an anatomical context. What is the preferred terminology for clinicians?

Answer 6

preganglionic (presynaptic) = neurons from CNS to peripheral ganglia

postganglionic (postsynaptic) = neurons from peripheral ganglia to target organs

Question 7

Define ganglia.

Answer 7

collections of neuronal cell bodies outside CNS

Question 8

Describe the length of the fibers in the sympathetic division.

Answer 8

preganglionic = short

postganglionic = long

Question 9

Describe the length of the fibers in the parasympathetic division.

Answer 9

preganglionic = long

postganglionic = short

Question 10

Differentiate between the sympathetic and parasympathetic divisions in terms of neurotransmitter usage.

Answer 10

sympathetic = acetylcholine at ganglion, then norepinephrine at target organ

parasympathetic = acetylcholine at both ganglion and target organ

Question 11

Where are the preganglionic neurons for the sympathetic division located?

Answer 11

thoracolumbar spinal cord (T1-L2)

Question 12

Where are the preganglionic neurons for the parasympathetic division located? (2)

Answer 12

brainstem (carried through CN III, VII, IX, X)

sacral spinal cord (S2-S4)

Question 13

What are paravertebral ganglia?

Answer 13

paired sympathetic ganglia extending from cranial cervical ganglion to coccyx

Question 14

How are paravertebral ganglia connected to each other?

Answer 14

connected superiorly and inferiorly by sympathetic trunk

Question 15

The sympathetic trunk primarily consists of

Answer 15

axons of preganglionic neurons

Question 16

The sympathetic trunk acts as the distribution system for which nerve fibers?

Answer 16

acts as distribution system for preganglionic fibers from thoracolumbar spinal cord to sympathetic ganglia

Question 17

Why is the number of ganglia lower than the number of spinal nerves supplying the sympathetic trunk?

Answer 17

Because the ganglia fuse at various levels — e.g. 3 cervical ganglia, though all cervical spinal nerves carry sympathetic fibers

Question 18

What are the white rami communicantes?

Answer 18

structures through which preganglionic fibers from the thoracolumbar spinal cord pass

Question 19

Preganglionic fibers from the thoracolumbar spinal cord are carried through what structure(s)?

Answer 19

carried through white rami communicantes

Question 20

Why are white rami only found in the thoracic and upper lumbar regions?

Answer 20

because the other regions (cervical, lower lumbar, sacral, coccygeal) do not give rise to preganglionic fibers

Question 21

What is the function of gray rami communicantes?

Answer 21

carry postganglionic outflow from paravertebral ganglia to spinal nerves

Question 22

Where are the cell bodies of motor neurons located?

Answer 22

anterior horn of spinal cord

Question 23

List the pathway taken by sympathetic motor fibers.

Answer 23

axon leaves spinal cord through ventral root → spinal nerve → reaches skeletal muscle via ventral or dorsal primary ramus

Question 24

Where are the cell bodies of sensory neurons located?

Answer 24

dorsal root ganglion

Question 25

Describe how sensory afferent fibers transmit signals to the spinal nerve.

Answer 25

reach spinal nerve via ventral or dorsal primary ramus → cell bodies in dorsal root ganglion → fibers enter dorsal horn of spinal cord through dorsal root w/ out being synapsed in dorsal root ganglion

Question 26

Where is the first preganglionic neuron of the sympathetic pathway located?

Answer 26

lateral horn of spinal cord at T1-T2 to L1-L3 level

Question 27

What is another name for the lateral horn of the spinal cord?

Answer 27

intermediolateral cell column (IML)

Question 28

Describe the pathway of the first preganglionic neuron of the sympathetic pathway. (7)

Answer 28

axon exits spinal cord through ventral root → enters spinal nerve → leaves through white rami communicans → enters paravertebral ganglion → synapses with postganglionic neuron → leaves through gray rami communicans → reaches effector

Question 29

After exiting the gray rami communicans, how does the postganglionic sympathetic fiber reach its effectors? (2)

Answer 29

(1) for smooth muscle of blood vessels/hair follicles/sweat glands → through ventral/dorsal primary rami
(2) for cardiac muscle/smooth muscle of viscera/other glands → directly

Question 30

List the targets of sympathetic fibers in neck, body wall, and limbs. (3)

Answer 30

(1) vasomotor smooth muscle = regulation of vessel diameter and therefore blood supply
(2) pilomotor smooth muscle = associated with hair follicles
(3) sudomotor = associated with sweat glands of skin

Question 31

Define piloerection.

Answer 31

goose bumps

Question 32

When paravertebral ganglia are connected, what structure do they form?

Answer 32

sympathetic trunk

Question 33

(T/F) In the thoracolumbar region, sympathetic ganglia are fused, meaning that each spinal nerve is not associated with its own sympathetic ganglion.

Answer 33

False. In the thoracolumbar region, each spinal nerve is associated with one sympathetic ganglion. The scenario described applies to the cervical region.

Question 34

Describe the organization of cervical sympathetic ganglia.

Answer 34

ganglia from various spinal levels are merged, resulting in fewer sympathetic ganglia and less regular distribution of ganglia

Question 35

Where does the preganglionic output for cervical sympathetic ganglia come from?

Answer 35

preganglionic neurons at superior thoracic level of spinal cord

Question 36

Describe the pathway of neurons to the cervical sympathetic ganglia.

Answer 36

preganglionic fibers enter sympathetic trunk via white rami communicans

travel superiorly in sympathetic trunk

synapse with cervical sympathetic ganglia

Question 37

After synapsing with the cervical sympathetic ganglia, how do postganglionic fibers from the cervical sympathetic ganglia exit? (2)

Answer 37

exit ganglia either:

(1) directly to form cardiac/pulmonary plexus
(2) by entering gray ramus communicans to join a spinal nerve

Question 38

What are the three cervical sympathetic ganglia?

Answer 38

superior

middle

inferior

Question 39

Describe the location of the superior cervical sympathetic ganglia.

Answer 39

fused ganglia from levels C1-C4

Question 40

What is the function of the superior cervical sympathetic ganglia? (3)

Answer 40

(1) postganglionic fibers provide sympathetic innervation of structures in head by following common carotid artery
(2) postganglionic fibers distributed via spinal nerves C1-C4 to supply smooth muscle + sweat glands in neck
(3) postganglionic fibers form cardiac nerves for sympathetic contribution to cardiac/pulmonary plexus

[tip: HNC = head, neck, cardiac]

Question 42

Describe the location of the middle cervical sympathetic ganglia.

Answer 42

fused ganglia from levels C5-C6

Question 43

What is the function of the middle cervical sympathetic ganglia? (2)

Answer 43

(1) postganglionic fibers distributed via spinal nerves C5/C6 to supply smooth muscles + sweat glands in neck and UEs
(2) postganglionic fibers form cardiac nerves to contribute to cardiac/pulmonary plexus

Question 44

Describe the location of the inferior cervical sympathetic ganglia. (2)

Answer 44

fused ganglia from levels C7 and C8

ganglion often fused with first thoracic sympathetic ganglion = cervicothoracic (stellate) ganglion

Question 45

What is the function of the inferior cervical sympathetic ganglia? (3)

Answer 45

(1) postganglionic fibers distributed via spinal nerves C7/C8 to supply smooth muscles + sweat glands in neck and UEs
(2) cervicothoracic ganglion supplies T1 of brachial plexus + intercostal space
(3) postganglionic fibers form cardiac nerves to contribute to cardiac/pulmonary plexus

Question 46

(T/F) The somatic structures of the neck, body wall, and limbs do not receive parasympathetic innervation.

Answer 46

True.

Question 47

What is the only parasympathetic structure visible in the neck?

Answer 47

vagus nerve (CN X)

Question 48

How does the vagus nerve travel through the neck?

Answer 48

within the carotid sheath

Question 49

The vagus nerve provides innervation to

Answer 49

viscera in thorax and abdomen

[note: does not provide parasympathetic innervation to neck/body wall/limb structures]