Autonomic Nervous System 1

Question 1

T/F The Autonomic nervous system is an afferent system.

Answer 1

F. The ANS is an efferent system.

Question 2

Draw the organization of the nervous system.

Answer 2

pp. 33 of the week 3 notes.

Question 3

The ANS innervates every organ of the body. Give examples of some of the functions it helps to accomplish.

Answer 3

• control arterial pressure
• GI motility and secretions
• urinary bladder emptying
• sweating
• body temperature

Question 4

What are the functions of the hypothalamus, spinal cord and brain stem in activating the ANS?

Answer 4

Hypothalamus-highest level of integration

Brain stem-regulate the hypothalamus

Question 5

What are the 2 main functions of ANS?

Answer 5

1) Basic metabolic or vegetative functions
- energy storage and release
- control of endocrine and neuroendocrine release
- control of exocrine secretion
2) Role in behavior

Question 6

T/F The SNS is largely subject to voluntary control while ANs is subject to involuntary control.

Answer 6

T. SNS unless for some reflexes it is mostly under conscious control while ANS functions via reflexes.

Question 7

Understand Figure 2 and Figure 3.

Answer 7

pp. 34 and 35 of Week 3 notes

Question 8

T/F In general, reflex arcs are not restorative.

Answer 8

F. They are restorative and they try to keep things constant. Ex: when our hand touches something hot we withdraw our hands in trying to restore temperature. This is an example of SNS reflex arc.

Question 9

In ANS, what are the 2 neurons b/n the CNS and innervated effector? Where are the cell bodies of these neurons located?

Answer 9

Preganglionic neuron: cell body within the CNS (either in the spinal cord or the cranial nerve nuclei
Postganglionic neuron: cell body within autonomic ganglia

Question 10

What are the 2 divisions of ANS and what 3 criteria is used to divide them?

Answer 10

Sympathetic and Parasympathetic Divisions

1) The origin of the preganglionic neuron is the overriding criteria
2) Length of preganglionic and postganglionic fiber
3) Pharmacology

Question 11

Describe the origins of preganglionic neurons in sympathetic and parasympathetic divisions.

Answer 11

Smpathetic: preganglionic cell bodies located in the thoracic and upper lumbar regions of spinal cord
Parasympathetic: preganglionic cell bodies located in the sacral spinal cord and brain stem. FIGURE 4 pp. 37
NOTE: the afferent limbs of an autonomic reflex arc may lie in any d/f nerve.

Question 12

Compare and contrast the preganglionic and postganglionic fiber length in sympathetic and parasympathetic divisions.

Answer 12

S: preganglionic fibers short and postganglionic fibers long
PS: preganglionic fibers long and postganglionic fibers short.

Question 13

What is the pharmacological difference b/n S and PS divisions?

Answer 13

S: NE secreted from postganglionic fibers stimulating effector organs. E (predominantly secreted by adrenal medula) and ACh (secreted by nerves) in sweat glands and some blood vessels to stimulate effector organs.
NOTE: E/NE are secreted by the adrenal medulla into blood so they are hormones not neurotransmitters.
PS: ACh secreted by postganglionic neurons to activate effector organs.

Question 14

Understand figure 5 and label it.

Answer 14

pp. 38 of week 3 notes.

Question 15

What is the sympathetic ganglionic chain?

Answer 15

In the S division: Short preganglionic fibers terminate and synapse with postganglionic fibers in ganglia close to the spinal cord or within outlying ganglia. In the former case, the ganglia are interconnected forming sympathetic ganglionic chain that runs parallel on each side of the spinal cord from the base of the skull to the sacrum.

Question 16

Much convergence and divergence occur within the sympathetic chains. Define these two terms.

Answer 16

Divergence: relatively small number of preganglionic fibers connects to a large number of postganglionic fibers.
Convergence: postganglionic fiber receives synaptic input from many preganglionic neurons.

Question 17

Convergence and divergence lead to:

Answer 17

Neuronal Integration: which results in global action, safety factor,..

Question 18

Study FIGURE 6

Answer 18

pp. 40 of week 3 notes.

Question 19

Study FIGURE 7.

Answer 19

pp 41

Question 20

In the parasympathetic system, what is the neurotransmitter that is released from preganglionic fibers and acts on the postganglionic neuron?

Answer 20

Acetylcholine

Question 21

T/F The sympathetic preganglionic fibers are short and myelinated while the sympathetic postganglionic fibers are long and unmyelinated.

Answer 21

T. Thus the propagation is 20m/sec compared to 1m/sec.

Question 22

Explain what is meant by the sympathetic division works in a segmental fashion.

Answer 22

• The postganglionic fibers receiving synaptic inputs from the preganglionic fibers originating from thoracic region of the spinal cord innervate the head, thorax, abdomen and upper extremities.
• And those that receive synaptic inputs from the preganglionic fibers originating from the lumbar region innervate pelvis and lower extremities.

Question 23

What do the sympathetic postganglionic fibers secrete onto the effectors?

Answer 23

They usually secrete NE that acts on the effector organ. However, sweat glands and some vessels secrete ACh.

Question 24

About 3/4 of the parasympathetic preganglion nerves are in:______

Answer 24

Vagus nerve (CN X)- the vagus nerve runs to organs of the thorax and abdomen.

Question 25

Fibers that leave from the sacral cord run in______

Answer 25

Pelvic nerve

Question 26

Where do the parasympathetic preganglionic fibers originate?

Answer 26

Cranial and sacral regions of the spinal cord.

Question 27

T/F. The parasympathetic preganglionic fibers are myelinate, long, and terminate in a synaptic connection.

Answer 27

T. They are myelinated like the sympathetic preganglionic fibers. Since they are long unlike the sympathetic preganglionic fibers they synapse close to the effector organ or even within the wall of the target organ.

Question 28

In the parasympathetic division, what is the neurotransmitter secreted by preganglionic fibers onto postganglionic fibers? And by the postganglionic fibers onto the organ?

Answer 28

ACh in both cases.

Question 29

Where are the parasympathetic ganglia distributed?

Answer 29

They are distributed near or in the walls of the effectors and they are short.

Question 30

Learn the comparative summary in FIGURE 9.

Answer 30

pp. 44

Question 31

What is Long QT syndrome?

Answer 31

characterized by long QT interval (start of QRS complex to the end of T wave in an ECG) resulting in prolonged cardiac action potential.

Question 32

What are the 7 genotypes responsible for LQTS? How do these mutations cause longer plateau in the ventricular AP?

Answer 32

• mutation in voltage dependent Na channel (LQT3)
• mutation in rapidly activating delayed rectifier channel (IKr, LQT2 and LQT6)
• mutation in slowly activating delayed rectifier channel (IKs, LQT1 and LQT5)
• mutation in the inward rectifier channel (IK1, LQT7)
• note is missing LQT4

Question 33

What are the manifestations (symptoms) associated with LQTS?

Answer 33

• torsade de pointes (ventricular tachycardia)
• arrhythmia
• cardiac events during increased sympathetic activity (drugs, stress, and physical activity)

Question 34

Draw how the ECG will look for normal as compared to LQTS?

Answer 34

PP 45.

Question 35

A receptor is a transducer and translator. Explain this statement.

Answer 35

In ANS, receptor changes stimulus into electrical potential (transducer or generator potential) which will generate AP.

Question 36

Describe the receptor potentials generated by receptors.

Answer 36

are local potential that are graded, not all or none, don’t have a threshold, are non-propagates, electronic, and are summing. These are similar to EPSPs.

Question 37

Describe the APs as compared to the receptor potentials.

Answer 37

AP: same amplitiude, shape, all or none,…

Question 38

Compare and contrast autonomic and somatic reflex arcs.

Answer 38

Both are simple in morphology and the principles governing their action are similar: stimulus lead to receptor potential-AP- propagates-motor neuron-response

Question 39

List 4 types of receptors.

Answer 39

1) Mechanoreceptors (baroreceptors)
2) Chemoreceptors (pH, glucoreceptors, aa receptors, PO2 and PCO2)
3) Thermoreceptors
4) Osmoreceptors (in hypothalamus monitor blood osmotic pressure)

Question 40

Define autonomic reflex arc

Answer 40

simplest connection b/n afferent and autonomic efferent at the segmental level of the spinal cord.

Question 41

What connects the afferent fiber and pre-ganglionic in autonomic reflex arcs?

Answer 41

Interneuron. Interneuron is not present for the simplest reflex arc of the somatic nervous system.

Question 42

Explain the sequence of events for the carotid baroreceptor reflex.

Answer 42

1) Stimulus:stretch induced by increased carotid sinus blood pressure
2) Stretch increases frequency of AP in the sinus nerve
3) Neurons in the medulla are excited sending signals to the CV centers of the brain stem (CV center has excitatory and inhibitor which exert their effects via sympathetic and parasympathetic pathways). Increased BP-stimulate inhibitory center-parasympathetic activation-vagus nerve firing increased-decrease HR, contractitlity, peripheral resistance (vasodilation).

Question 43

The baroreceptor ouput depends on both the rate of change and magnitude of change of BP. What are the terms describing these changes?

Answer 43

Phasic and Tonic component respectively

Question 44

T/F The phasic component of the baroreceptors responds to both increase and decrease in pressure.

Answer 44

F. It just responds to an increase. The tonic component is more prominent as the mean arterial pressure increases.