PT 759 - Autonomic Nervous System

How many divisions are there in the autonomic nervous system?

3: sympathetic, parasympathetic, enteric

What is the primary function of the ANS?

Maintain homeostasis and optimal internal environment

Does the ANS need to be consciously controlled?

No operates via subconscious involuntary control

Visceral afferents enter the spinal cord and do what once there?

Synapse with visceral efferents and with neurons that go to the brainstem, hypothalamus and thalamus

Which cranial nerves convey autonomic afferent information?

Glossopharyngeal (CN IX)

Vagus (X)

Sensory neurons of the ANS are embedded in the visceral organs and vasculature and use which types of receptors?

- Mechanoreceptors

- Chemoreceptors

- Nociceptors

- Thermoreceptors

The medulla plays a role in regulating which bodily processes?

HR

Breathing

Vasoconstriction

Vasodilation

The pons plays a role in regulating which bodily processes?

Respiration

What is the role of the hypothalamus in the ANS? And through which bodily processes?

Maintains equilibrium in interior by influencing:

Eating

Drinking

Sleep

Body temp

Sexual function

Hormones

What is the role of the emotion/motivation system in autonomic regulation?

Emotions are translated in bodily responses (anxiety increases HR)

What are the two main divisions of the ANS? And what is the third?

Two main are sympathetic and parasympathetic

Third is enteric

How do the sympathetic and parasympathetic systems work together to maintain homeostasis?

They counterbalance each other

When would the sympathetic division of the ANS be stimulated?

When performing activities that require energy (ex. freeze, flight or fight)

What effects does sympathetic stimulation of the ANS produce?

Increases in HR, BP, blood flow to somatic muscle

Decrease in blood flow to gut

When would the parasympathetic division of the ANS be stimulated?

When trying to conserve energy and replenish bodily resources

What effects does parasympathetic stimulation of the ANS produce?

Decreases in HR and BP

Increased gut motility

The sympathetic and parasympathetic nervous systems share similarities in that they both?

Activate visceral and arterial smooth muscle

Cause secretion by wide array of glands

Sympathetic and parasympathetic control of the viscera regulates which systems?

Regulates:

- cardiovascular system

- respiratory system

- digestive system

- urinary system

- glandular secretions

- sexual and reproductive systems

- osmosis and temp

Be able to explain this picture and all the pathways.

Where do sympathetic nerves of the efferent pathways of the ANS originate and where do they synapse?

Originate at T1-L2 spinal cord segments

Synapse in paravertebral ganglia (located in sympathetic trunk) or in outlying ganglia

What are the outlying ganglia that sympathetic nerves of the efferent pathways of the ANS synapse with?

Cervical ganglia

Celiac ganglia

Mesenteric ganglia

Where do parasympathetic nerves of the efferent pathways of the ANS originate?

Originate from cranial nerve nuclei in brainstem and sacral spinal cord segments

The 2-neuron pathway present in the efferent pathways of the ANS includes neurons synapsing where? And what are the 2 neurons?

2 neurons synapsing in a peripheral region:

Pre-ganglionic neurons

Post-ganglionic

Where is the pre-ganglionic neuron in the efferent pathway of the ANS located? And where do its fibers extend to?

Located in brainstem or spinal cord

Fibers extend to autonomic ganglion

Post ganglionic neurons of the efferent pathway are also called what?

Where are they located?

And where do their fibers extend to?

Called lower motor neurons

Located in the autonomic ganglion

Fibers extend to effector organ or glands

Are the autonomic ganglia of the efferent pathways of the ANS located outside the spinal cord?

Yes, external to spinal cord

Identify the pre-ganglionic neuron that synapses in the sympathetic chain ganglion, the lower motor neuron, and post-ganglionic fibers in this photo.

The sympathetic chain is located where in relation to the spinal cord?

Lateral to and near the vertebral column

Postganglionic ganglia of the parasympathetic NS are located where?

At or within visceral effector organs

The sympathetic nervous system has cell bodies going from T1-L2 giving it the other name of?

Thoracolumbar outflow

The neurotransmitters used in the ANS are?

Acetylcholine

Norepinephrine

Epinephrine

Preganglionic neurons of both the sympathetic and parasympathetic systems secrete which NT onto lower motor neurons?

Acetylcholine (ACh)

The lower motor neurons (postganglionic neurons) for the sympathetic and parasympathetic systems use which NT?

ACh

NE

Epi

In the sympathetic NS preganglionic neurons secrete which NT? And postganglionic LMN secrete which NT?

Pre secretes ACh

Post secretes NE

In the parasympathetic NS both pre and postganglionic neurons secrete which NT?

ACh

What is the major function of sympathetic NS and what is it known as?

Major function: maintain optimal blood supply to organs

Known as "fight-or-flight"

A person who has threatened/fearful response would cause sympathetic activation creating what changes?

HR increase

Breathing rapid and deep

Skin cold and sweaty

Pupils dilate

Gut motility reduced

Major effects of the sympathetic NS are?

Optimized blood flow to organs

Regulation of body temp and metabolic rate

Regulation of activity of viscera

Spinal segments from the sympathetic nervous system innervates viscera in which areas of the trunk and thorax?

Upper thoracic

Various thoracic

Lower thoracic

Upper lumbar

The upper thoracic spinal segments of the sympathetic neurons innervate which regions?

Head

Neck

UE

Heart

Thoracic cavity

Various thoracic spinal segments of the sympathetic NS innervate which viscera?

Stomach

Intestines

Parts of colon

Adrenal medulla

Abdomen

Lower thoracic and upper lumbar spinal segments of the sympathetic NS innervate which viscera?

Parts of colon

Rectum

Pelvis

Lower trunk

LE

In addition to innervating the viscera, the sympathetic NS also sends axons out (efferent) with each segment that do what?

Constrict blood vessels

Open sweat glands

Excite hair follicles

The sympathetic nervous system is composed of what?

Sympathetic chain

Superior cervical ganglion

Celiac ganglion

Superior mesenteric ganglion

Inferior mesenteric ganglion

The adrenal medulla secretes which NT used in the sympathetic NS? And in response to what?

Secretes EPI and NE into the blood stream in response to stress

EPI and NE ramp up what response in the body?

Fight or flight

Pre ganglionic cells in the sympathetic NS secrete which NT? And LMN in the ganglia secrete which NT?

Pre secrete ACh

LMN secrete NE

How quickly do target organs respond to norepinephrine, and how long does the effect last?

Immediate and time limited

What is the principal function of the parasympathetic NS?

Energy conservation and storage

After someone finishes a meal, what PNS effects would you see in a person?

Low BP, HR, respiratory rate

GI tract activity high

Warm skin

Constricted pupils

Is the PNS more or less restricted in its distribution (craniosacral outflow)?

More restricted

Cell bodies of preganglionic neurons are located where in the PNS?

Brainstem nuclei of cranial nerves:

CN III, VII, IX, X

Sacral segments S2-S4

Cell bodies of postganglionic neurons are found where in the PNS?

At or within visceral effector organs

Effector organs of the PNS are?

Pupils

Salivary, nasal, and lacrimal glands

Heart and lungs

Most visceral organs

What NT does the PNS only use?

ACh

What are the various receptor types in the PNS? And what type of signal do they send?

Nicotinic always send excitatory

Muscarinic can send inhibitory or excitatory

What is the function of the enteric system?

Influence activity of the GI tract

The enteric system is composed of which two systems?

Intrinsic and extrinsic systems

The intrinsic system of the enteric system does what?

Modulate secretion and motility

The extrinsic system of the enteric system does what?

Override intrinsic system through sympathetic or parasympathetic systems to increase or decrease motility

Give an example of differential activation of the SNS or PNS creating a specific effect at a target organ.

Pupils dilate or constrict in response to light intensity

Initiation of gag reflex or swallowing in response to stimuli in the larynx and esophagus

Effects of the SNS and PNS are synergistic creating what effect at the target organ?

Opposing actions are balanced to create optimal organ function

Dysfunction of the ANS include what? (Might not be on quiz/midterm)

Horner's syndrome

Orthostatic hypertension

Postural orthostatic tachycardia syndrome (POTS)

Reflex syncope