5. DSA Autonomics

Question 1

What is the general flow of stretch reflexes from the leg to the spinal cord and back?

Answer 1

Sensory afferent nerve from stretch throuhg dorsal root into spinal cord. Synapses on alpha motor neurons and motor nerve efferent via ventral root goes and releases Ach at NMJ where stretch was occuring, causing contraction/shortening of stretched muscle

Question 2

Which stimuli is likely to elicity a somatic reflex?

Answer 2

a pain that tells you that you have stepped on a rock- something you will be consciously aware of

Question 3

What are the sensory stimuli that modify the ANS?

Answer 3

BP, PaO2 and pHa

Question 4

What levels are included in production of somatic reflexes?

Answer 4

Any level of the CNS! from medulla, to cortex, to pons to spinal cord

Question 5

What is difference between somatic and ANS regarding synapsing?

Answer 5

Somatic is a single axon system which does not synapse. ANS has 2 body synapsing and a cell that doesn’t end in the specialized NMJ

Question 6

What is the general difference between parasympathetic and sympathetic nervous system?

Answer 6

para: rest and digest
Symp: Fight or flight

Question 7

In the parasympathetic nervous system (AND SYMPATHETIC), the NT released by the pre-ganglionic fiber is?

Answer 7

Achetylcholine

Question 8

What does the Ach bind with across the cleft once released?

Answer 8

binds a nicotinic cholinergic receptor (nAchR) on post ganglionic dendrite, allowing influx of sodium and depolarization

Question 9

The axon in para/sympathetic divisions do not terminate in presynaptic terminals. instead the axon has swellings (varicosities) along the length of the axon. Containing all the machinery needed to release NT. What does this mean for synapse site and interstitial fluid?

Answer 9

Synaptic cleft is larger and more open to interstitial fluid than standard synapse, also see NTs spread over much broader area

Question 10

What are the resulting effects from the differences in axon terminals for sympathtic compared to somatic? (2)

Answer 10

NT can diffuse far away from release point and amounts can be detected in blood
2. receptors can be activated by NTs that diffused away from original point of release

Question 11

In parasympathetic NS, postganglion releases acetylcholine which binds to?

Answer 11

muscarinic cholinergic receptor instead of nicotinic… leading to a secondary messenger system

Question 12

In sympathetic, postganglion releases norepinephrine which can bind to? (2)

Answer 12

1. alpha adrenergic
2. beta adrenergic
   receptors
   (activate secondary messengers)

Question 13

Sympathetic pre synaptic fibers travel to sympathetic trunk and to adrenal medulla and to chromafin cells where they synapse. What do they release?

Answer 13

Releasing epinephrine into blood which acts on adrenergic receptors

Question 14

The synapse between a neuron that left the spinal cord at the thoracic level, entered the sympathetic chain and synapses on a neuron within the ganglion:

Answer 14

This description is consistent with the synapse between a pre-ganglionic (-synaptic) neuron of the sympathetic division and it’s post-ganglionic (-synaptic) cell within the sympathetic chain. The neurotransmitter released at any of these first synapses (regardless of division) is acetylcholine and it will bind to a nicotinic cholinergic receptor.

Question 15

The synapse between a neuron that left the CNS via a cranial nerve and a neuron within a ganglion close to the target organ:

Answer 15

The neuron that leaves the CNS is the pre-ganglionic (-synaptic) neuron. Once you know it is the pre-ganglionic (-synaptic), you know that the neurotransmitter it releases is acetylcholine. In addition, this is a part of the parasympathetic division as indicated by the fact that it leaves via a cranial nerve to travel to a ganglion that is close to the target organ. The target organs receiving parasympathetic innervation all express muscarinic cholinergic receptors.

Question 16

The synapse between a neuron that arose from the sympathetic chain and the heart (it’s target organ):

Answer 16

The fact that the first neuron described arose from the sympathetic chain indicates that this is part of the sympathetic division of the ANS. The next step is to decide whether it is the pre-ganglionic or post-ganglionic (-synaptic) neuron in the chain. The fact that it terminate on a target organ and originate in the sympathetic chain both identify this as the post-ganglionic (-synaptic) component. Once you know have identified both of these facts, you know that the neurotransmitter released is norepinephrine. Norepinephrine binds the adrenergic receptors, either of the alpha subtype (alpha-adrenergic) or beta subtype (beta adrenergic). We haven’t discussed where the specific subtypes are found yet, but you should be able to recognize the adrenergic receptor as binding Norepinephrine.

Question 17

The synapse between a neuron that left the CNS via a cranial nerve and a neuron within a ganglion close to the target organ:

Answer 17

The neuron that leaves the CNS is the pre-ganglionic (-synaptic) neuron. Once you know it is the pre-ganglionic (-synaptic), you know that the neurotransmitter it releases is acetylcholine and it will bind to a nicotinic cholinergic receptor.

Question 18

The synapse between a neuron that traveled through the sympathetic chain and synapsed on a chromaffin cell in the adrenal medulla:

Answer 18

The description of this neuron indicates that it is the equivalent of the pre-ganglionic (-synaptic) neuron and part of the sympathetic division (the adrenal medulla should scream “sympathetic” at you). Since it is the equivalent of the pre-ganglionic (-synaptic) cell, it releases acetylcholine at the chromaffin cell. The chromaffin cells, like the post-ganglionic (-synaptic) neurons in the sympathetic chain, express nicotinic cholinergic receptors.

Question 19

The synapse between a neuron with its cell body in the Stellate ganglion (close to heart) and the nodal cells of the heart:

Answer 19

The stellate ganglion is located close to the heart (as noted) and is part of the parasympathetic division. The neuron in question synapses on the nodal cells of the heart rather than another neuron, indicating that this is the post-ganglionic (-synaptic) cell in the chain. As part of the parasympathetic division, it will release acetylcholine from its vesicles. However, this is the synapse at the target organ, so this time the receptor activated is a muscarinic cholinergic receptor.