LECTURE 21 FLASHCARDS AUTONOMIC NERVOUS SYSTEM

The visceral motor division

The visceral motor division

Exactly, which division of the PNS corresponds to the autonomic NS?

Glands, cardiac muscle, and smooth muscle

Which organs/structures/muscles does the ANS control?

Its name means “self-governed” since it is almost fully independent of our will

Why is it called “autonomic” NS?

Involuntary (out of our control)

Does the ANS control voluntary or involuntary body processes??

- Parasympathetic NS: Relaxation-and-Digest response and homeostasis. Sympathetic NS: fight-or-flight response and stress response

What are the two branches of the autonomic nervous system (ANS), and what physiological responses does each of them regulate?

- Both are unconscious, automatic and stereotyped responses to stimulation but in case of visceral reflexes they are initiated by stimulus in the viscera

What constitutes the primary distinction in the definitions of visceral and somatic reflexes?

- Receptors (located in viscera), afferent neuron (sensory), integrating center (interneurons), efferent neurons (motor) and, effector (is a viscera)

What are the 4 components of a visceral reflex arc?

stretch, tissue damage, blood chemistry, body temperature, and other internal stimuli

What types of stimuli are detected by the receptors within the viscera?

Plural: Autonomic ganglia- where information in the form of action potentials, originating from CNS, is transmitted to the PNS. Where the preganglionic neuron establishes a synaptic connection with the postganglionic neuron

What is an autonomic ganglion? What does it connect?

from a lateral horn neuron in the spinal cord, or a cranial nucleus neuron in the brainstem

From which specific site within the central nervous system (CNS) does the preganglionic fiber originate?

- Yes, opposite effects. Balance between both systems keeping a background rate of activity called autonomic tone.

Do the parasympathetic and sympathetic nervous systems typically innervate the same visceral organs, and what are their respective roles in maintaining autonomic tone?

PSNS for energy conservation, SNS for the stress response.

Which division of the autonomic nervous system (ANS) is responsible for regulating body energy, and which one becomes active during exertion, stress, or emergency responses?

Sympathetic division

Do the paravertebral ganglia belong to the sympathetic or parasympathetic division of the autonomic nervous system?

Adjacent to both sides of the vertebral column from the cervical to the coccygeal level

Where is the paravertebral ganglia?

postganglionic neurons

To clarify, what types of neural cell bodies are usually situated within the paravertebral ganglia, with "ganglia" referring to collections of neural cell bodies located outside the central nervous system (CNS)?

thoracic and lumbar regions

When considering the sympathetic nervous system, from which segments of the spinal cord do preganglionic neurons originate?

Sympathetic fibers are found exclusively in spinal nerves originating from the thoracic and lumbar regions, while parasympathetic fibers are exclusively present in the sacral region, specifically in sacral spinal nerves.

As you may recall, spinal nerves are composed of both motor and sensory fibers. Do they also include sympathetic and parasympathetic nerve fibers?

The thoracolumbar division is associated with the sympathetic nervous system (SNS), and the craniosacral division is associated with the parasympathetic nervous system (PSNS), depending on the region from which the preganglionic fiber emerges.

Which division of the autonomic nervous system is referred to as the "thoracolumbar division," and which one is known as the "craniosacral division"?

The parasympathetic division primarily controls these reflexes. In this reflex arc, the preganglionic neuronal cell body is located in cranial nuclei within the brainstem, rather than the spinal cord.

When considering cranial reflexes involving the cranial nerves III, VII, IX, and X, which division of the autonomic nervous system, sympathetic or parasympathetic, primarily controls these reflexes?

Pre- shorter in the SNS. Post- shorter in the PSNS

Which of the two divisions of the ANS possesses shorter preganglionic axons? Additionally, which one has shorter postganglionic axons?

SNS. PSNS ganglia is in or close to the visceral organ served

Which of the two divisions of the ANS has the ganglia (or ganglion) located closer to the CNS?

This is also true for the PSNS, but not for the SNS where the neurotransmitters releases are mostly norepinephrine.

In both divisions of the autonomic nervous system (ANS), preganglionic fibers consistently release the neurotransmitter acetylcholine. What about the postganglionic fibers?

Neural divergence is a phenomenon in the nervous system where a single neuron sends signals to multiple target neurons or effector cells.

What does the term "neural divergence" refer to?

The SNS. When one preganglionic neuron becomes active, it can stimulate multiple postganglionic fibers that ultimately affect different target organs, resulting in widespread effects. Conversely, the parasympathetic nervous system (PSNS) is more discerning in its activation of target organs, exhibiting greater selectivity.

Which division of the ANS demonstrates greater neural divergence? And what is the overall consequence or significance of having increased neural divergence in this context?

(1) Somatic NS: 1 motor neuron. ANS: 2 efferent neurons (pre- and post-ganglionic). (2) ANS includes ganglia connecting pre- and postganglionic neurons, unlike the somatic NS.(3) Somatic NS targets specific cells; ANS releases neurotransmitters diffusely, affecting multiple cells simultaneously.

What are the three primary distinctions between the autonomic and somatic nervous systems concerning the output pathway (efferent)?

Spinal nerve route, sympathetic nerve route, and Splanchnic Nerve Route

What are the three pathways that sympathetic fibers can take after entering the sympathetic chain ganglia?

The ganglion where the preganglionic fiber forms a synapse with the postganglionic neuron is situated at the same level in the spinal nerve route; while in the sympathetic nerve route, it's above or below, requiring the preganglionic axon to travel up or down the sympathetic trunk.

What is the main difference between the sympathetic and the spinal nerve routes?

White ramus communicans contains the pre-ganglionic axons (mostly myelinated) and gray ramus communicans the post ganglionic axons (unmyelinated).

What are the contents of the two rami communicates in the spinal nerve route?

It is situated in a collateral ganglion

Within the splanchnic nerve pathway, where is the neurosoma of the postganglionic neuron typically located?

These fibers are referred to as the splanchnic nerve

What term is assigned to the preganglionic fibers in the splanchnic nerve pathway after they extend past the paravertebral ganglia (sympathetic trunk ganglia)?

While both house the neurosoma of postganglionic ganglia, paravertebral ganglia pertain to the sympathetic trunk ganglia, whereas prevertebral ganglia are exclusive to the splanchnic nerve pathway.

Are paravertebral ganglia and prevertebral ganglia synonymous?

The major collateral ganglia include the celiac ganglia, superior mesenteric ganglion, and inferior mesenteric ganglion.

What are the three primary collateral ganglia?

Organs situated within the abdominal cavity are associated with the collateral ganglia.

Which organs are connected to the collateral ganglia?

The SNS, often known as the "sympathoadrenal system," innervates the adrenal gland.

Does the sympathetic nervous system (SNS) or parasympathetic nervous system (PSNS) innervate the adrenal gland?

The adrenal medulla itself serves as a sympathetic ganglion, comprising postganglionic neurons devoid of dendrites or axons.

Where are the postganglionic neurons found in the sympathetic pathway that innervates the adrenal gland?

The two types are alpha and beta receptors, and they bind norepinephrine and epinephrine.

What are the two types of sympathetic or adrenergic receptors, and which neurotransmitter do they bind?

The two types are nicotinic and muscarinic receptors, and they bind acetylcholine (ACh).

What are the two types of cholinergic receptors, and which neurotransmitter do they bind?

Nicotinic receptors exist as Nm at neuromuscular junctions, responsible for skeletal muscle contraction, and Nn in all peripheral autonomic nervous system ganglia, where the preganglionic neuron secretes ACh.

What are the two types of nicotinic receptors, and where are they located in the body?

M2 receptors (located in the heart) and M3 receptors (found in the rest of the organs innervated by the parasympathetic nervous system) are primarily responsible for the parasympathetic response.

Which two muscarinic receptors are primarily responsible for the parasympathetic response, and where are they mainly found?

Vasoconstriction, mydriasis (pupil dilation), urinary sphincter contraction (leading to urinary retention), glycogenolysis, and the inhibition of renin release

What are five effects associated with the activation of alpha type 1 receptors?

Alpha 1 receptor activation typically leads to smooth muscle contraction.

In general, does the activation of alpha 1 receptors result in the contraction or relaxation of smooth muscle in different organs?

Beta 1 receptors are primarily located in the heart, where they mediate the sympathetic response by increasing heart rate, cardiac muscle contraction, and atrioventricular conduction.

Where are beta type 1 receptors predominantly found, and what are their overall effects?

Beta 1 receptors stimulate the release of renin, which subsequently increases blood pressure.

Do beta 1 receptors stimulate or inhibit the release of renin, and how does this affect blood pressure?

Beta 2 receptors generally lead to the relaxation of smooth muscle.

As a general rule, do beta 2 receptors contract or relax the smooth muscle in different organs?

Beta 2 receptor stimulation results in bronchodilation, vasodilation, and a decrease in GI motility by relaxing the smooth muscle in these organs.

What are the effects of beta 2 receptor stimulation on the bronchioles, vascular system, and GI tract?

Beta 3 receptors are primarily found in adipose tissue (where they increase lipolysis) and in the detrusor muscle of the bladder (leading to muscle relaxation, preventing urination).

Where are the two main locations of beta 3 receptors, and what are the consequences of their stimulation in these organs?

Yes, it's possible for one organ to have multiple subtypes of adrenergic receptors, although one subtype from each system typically dominates in a given tissue.

Can one organ have multiple types of adrenergic receptors?

Cardiac myocytes predominantly have beta 1 receptors, airway smooth muscle contains beta 2 receptors, and the smooth muscle lining blood vessels typically has alpha 1 receptors.

Which are the main types of adrenergic receptors found in cardiac myocytes, airway smooth muscle, and the smooth muscle lining blood vessels?

The arrector pili, sweat glands, and the smooth muscle of blood vessels are not dually innervated by both systems.

Name three organs or structures that do not have dual innervation by both the sympathetic and parasympathetic nervous systems.

Thermoregulatory sweating, controlled by the sympathetic division, involves the release of acetylcholine (ACh) at the postganglionic neurons, which binds to muscarinic receptors.

In thermoregulatory sweating, what neurotransmitter is released by postganglionic sympathetic neurons, and which type of receptors does it bind to?

The sympathetic division is responsible for vasomotor tone, and alpha 1 receptors play a role in this process.

Which division of the autonomic nervous system is responsible for vasomotor tone, and which receptors are involved?

Under physiological conditions, the smooth muscles of arterioles remain partially contracted (vasoconstricted) to maintain tone.

Under physiological conditions, are the smooth muscles of blood vessel walls partially constricted or relaxed?