Autonomic Nervous System (L2)

Question 1

What is the central nervous system?

Answer 1

A central processing center for integration, processing, and reactions occur. The response is conveyed by the peripheral nervous system.

Question 2

What are sensory nerve fibers?

Answer 2

Afferent fibers; they bring information to the CNS.

Question 3

What are motor nerve fibers?

Answer 3

Efferent fibers; they bring information from the CNS to the periphery to affect target organs. This conveys the command from the control center (CNS)

Question 4

What are the 3 branches of the Autonomic Nervous System (ANS)?

Answer 4

Sympathetic

Parasympathetic

Enteric (gut brain; can further be modified by SNS and PSNS)

Question 5

5 autonomic centers in the brain (that she mentioned)

Answer 5

Medulla*, pons*, hypothalamus*, amygdala, cortex

Question 6

Medulla function within ANS

Answer 6

Respiratory and water control

Question 7

Pons function within ANS

Answer 7

Respiratory and urinary control

Question 8

**Hypothalamus function within ANS

Answer 8

Four F’s (fighting, fleeing, fucking, and feeding)

Known as the master gland

Question 9

Amygdala function within ANS

Answer 9

Emotional center; we can have learned responses of fear

Question 10

Does the ANS control skeletal, or smooth muscle?

Answer 10

Smooth muscle. Skeletal muscle is under somatic control (we can modulate it voluntarily).

Question 11

Sympathetic nervous system purpose and location in body (cervical, thorax, lumbar, sacral, coccygial, some kind of combination?)

Answer 11

Thoracolumbar location

Excitatotry/ flight or flight division

Question 12

Parasympathetic nervous system overarching role and location in body (ex. cervical, lumbar, thoracic, etc, some kind of combo?)

Answer 12

Craniosacral ; rest and digest;

Question 13

Enteric nervous system (structure/location, function)

Answer 13

Large network of billions of neurons in the gut, that function as a “gut brain” to coordinate digestion. It can be controlled further by parasympathetic and sympathetic stimulation but is largely autonomous.

Question 14

What is the overall goal of the autonomic nervous system, with regard to the body’s “balance” state?

Answer 14

The ANS’s goal is to maintain homeostasis, so changes made are meant to drive the body back toward that. Receptors receive a signal (ex. light, pain), and transmit it to the CNS for processing, and then a response is sent back out to modulate what cells are doing to compensate/respond.

Question 15

Describe the two-neuron system

Answer 15

The two-neuron system is how our body acts as a relay, with regard to passing information from the CNS to the visceral organ systems. A pre-ganglionic neuron, whose dendritic end is in the CNS, will pass a signal through its white communicating ramus to synapse in a ganglion. It synapses with a post-ganglionic neuron (dendrite is in ganglion) that then reaches out through its gray communicating ramus to synapse with an organ elsewhere in the body.

Question 16

Are neuronal synapses at visceral organs and smooth muscle clear defined synapses or are they more flimsy

Answer 16

They’re more flimsy and called en passant meaning in passing. The axon is filled with varicosities that deposit neurotransmitter. This is in contrast to neuronal or skeletal muscle junctions that are very defined.

Question 17

Neurotransmitters released from ANS efferent fibers, pre-and-post ganglionic

Answer 17

NT released from ALL ANS efferent PRE-GANGLIONIC: Acetylcholine onto nicotinic receptors

NT released from SNS post-ganglionic: Epinephrine

NT released from PSNS post-ganglionic: Acetylcholine onto muscarinic receptors

Question 18

Adrergic Neurotransmission

Answer 18

Norepinephrine is released from varicosities onto the target visceral organ where it can bind to adrenergic receptors. It is then going to be degraded by COMT (catechol-o-methyl-transferase) / MAO in mitochondria for NE that is just reuptaken. NE that is not degraded when taken up by presynaptic cell can then be re-packaged into vesicles of future signaling.

Fresh norepinephrine is derived from tyrosine

Question 19

Cholinergic neurotransmission, and how can this be modulated by drugs?

Answer 19

Acetylcholine is released from the presynaptic cell, where it then binds to muscarinic acetylcholine receptors. Excess acetylcholine will be degraded by acetylcholine esterases. Choline will be taken up into the cell and used to generate new acetylcholine for future cycles.

This process can be blocked by atropine (muscarinic blocker). The process can be forced to continue by sarin gas (blocks acetylcholine esterases).

Question 20

If you are trying to stimulate vasoconstriction (symapthetic) through SNS nerve activity, but you are also trying to vasodilate that same region (via vascular endothelial cells generating nitric oxide (NO)), what signal will win?

Answer 20

The local signal

Question 21

How are SNS and PSNS distinct, with regard to ganglionic length?

Answer 21

In the SNS the ganglia is relatively close to the spinal cord, but in PSNS the ganglia are distant from the spinal cord, meaning there is a very short path from the post-ganglionic neuron to the target organ .

Question 22

Do ALL SNS nerve fibers release norepinephrine?

Answer 22

No. Sweat glands are hit by acetylcholine to stimulate them.

Question 23

Describe the SNS pathway to the adrenal gland

Answer 23

There is a pre-ganglionic neuron that synapses right on the adrenal gland. The cells in the adrenal gland will dump epinephrine / NE into the bloodstream directly, so there is no true post-ganglionic neuron in this system. This is good, because we want a fight/flight response to occur as quickly as possible and dumping epinephrine into the blood stream gets it through the systemic circulation quickly.

Question 24

Baroreceptor reflex

Answer 24

Aortic arch senses blood pressure drop and sends signal though vagus nerve (Cranial nerve X); carotid sinus senses blood pressure spike and sends signal through glossopharangyeal nerve (Cranial nerve IX) via mechanoreceptor channels whose open status is altered by the change in pressure. This signal, when sent to the CNS (medulla oblongata) sends a signal back to parasympathetically to say “hey, maybe stop”. This involves M2 receptors on the heart. This then leads to decreased SNS activity on heart (b1) and vasculature (a1).

Question 25

Intrinsic innervation of the gut

Answer 25

Myenteric and submucosal Plexi (locations are in the name)

Question 26

Extrinsic innervation of the gut

Answer 26

PSNS and SNS (pelvic and vagal nerve; Celiac, superior and inferior mesenteric vertebral ganglion respectively)

Question 27

Description of the intrinsic innervation of the gut

Answer 27

past the mucosal layer of the gut there is a layer of nerves (submucosal; meissner’s). This is between the mucosal and inner smooth muscle layer.

The two extrinsic most layers of muscle are a longitudinal layer (outermost) and a circular smooth muscle layer (second-outermost). between those is the myenteric (auerbach’s) plexus.

Question 28

Peristaltic reflex

Answer 28

The bolus of food takes up space, so as it moves through the small intestine it causes distentions where it is. This leads to stretch receptors in the area being activated. Seritonin is going to be released to aid in the process. Behind the bolus (we call this upstream) there is going to be a release of Ach and substance P from these neurons to cause contraction of the circular smooth muscle layer, and also an inhibitory neuron will release VIP and NO to the longitudinal layer of smooth muscle. This will lead to overall contraction.

Downstream of the food bolus we have the opposite occuring. We have NO and VIP being released from a descending inhibitory neuron to relax the circular smooth muscle, and Ach and substance P will be released from a descending excitatory neuron to contract the longitudinal layer. This will overall increase the cavity and allow food to be pushed in that direction. The cycle will then repeat.