8.) Autonomic Nervous System
What are the anatomical differences between the Sympathetic nervous system and the Parasympathetic nervous system?
*Sympathetic nervous system:* 1.) Short preganglionic and long postganglionic fibers. 2.) Post-ganglionic neurons epinephrine and norepinephrine. 3.) Sympathetic trunk and pre vertebral ganglia. 4.) Innervation/fibers are divergent, produces global response. 5.) More complex and innervates more organs. 6.) Innervates visceral organs + visceral structures in the superficial region of the body. *Parasympathetic nervous system:* 1.) Long pre-ganglionic and short post-ganglionic fibers. 2.) Pre and post Release acetylcholine. 3.) Ganglia are far from CNS, and are nearby or within their target organs. 4.) Innervation/fibers are more discrete, specific, and localized. No extensive divergence. 5.) Less complex than the sympathetic
Where do sympathetic fibers exit the spinal cord? parasympathetic?
*Sympathetic:* Thoracolumbar region. Preganglionic (or first order) neurons are located in the lateral gray horns of spinal segmentsT1-L2. *Parasympathetic:* Craniosacral region. Preganglionic (or first order) neurons are located in the brain stem and lateral gray horns of sacral spinal segments S2-S4.
Give the characteristics of the neurotransmitters of the autonomic nervous system.
1.) All preganglionic autonomic fibers release Ach at their terminals and their effects are always excitatory. 2.) Postganglionic parasympathetic fibers also release Ach but the effects can be excitatory or inhibitory depending on the post synaptic receptor. 3.) Postganglionic sympathetic fibers mostly release NE and the effects are typically excitatory.
Where are the levels of control of the ANS?
1.) Brain stem and spinal cord 2.) Hypothalamus and amygdala 3.) Cerebral cortex* *This is important because although the ANS is not considered to be under voluntary control, many of its activities are regulated by the CNS.
What are the major effects produced by the preganglionic fibers of the sympathetic nervous system that innervate collateral ganglia?
1.) Constrict arteries and restrict flow to visceral organs 2.) Decrease activity of digestive glands and organs. 3.) Stimulate the release of glucose from glycogen reserves in the liver. 4.) Stimulate the release of lipids from adipose tissue 5.) Relax the smooth muscle in the wall of the urinary bladder to prevent urination. 6.) Reduce the rate of urine formation at the kidneys 7.) Controls ejaculation in the male.
What are the major effects produced by the parasympathetic nervous system?
1.) Constriction of the pupils to restrict the amount of light that can enter, will also focus on nearby objects 2.) Secretion by the digestive glands (e.g. salivary glands, gastric glands, pancreatic glands, etc...) 3.) Secretion of hormones that promote nutrient absorption by peripheral cells 4.) Increased smooth muscle activity along the digestive tract. 5.) Stimulation and coordination of defecation. 6.) Constriction of the bladder 7.) Constriction of respiratory pathways 8.) Reduction in heart rate and force of contraction 9.) Sexual arousal and stimulation of sexual glands in both sexes *10.) There is no parasympathetic output to the limbs.*
What are the important origins of the parasympathetic nervous system? Where do these nerves innervate?
1.) Cranial outflow - innervates the organs of the head, neck, thorax, and most of the abdomen. (Vagus nerve (X), Oculomotor nerve (III), Facial nerve (VII), and the glossopharyngeal nerve (IX)). 2.) Sacral outflow supplies the rest of the abdomen and pelvic organs. (Pelvic splachnics).
Compare and contrast the somatic motor nervous system to the autonomic nervous system.
1.) Lower motor neurons of the SNS exert direct control over skeletal muscle. In ANS there is always a synapse between the CNS motor neuron and the peripheral effector. I.e. *the ANS consists of pre and post ganglionic fibers.* 2.) In the ANS, there is *considerable divergence,* that is a single preganglionic neuron can activate over two dozen ganglionic neurons. the SNS is more specific. 3.) Preganglionic fibers are lightly myelinated. Axons leaving the autonomic ganglia (postganglionic fibers) are smaller and unmyelinated. *Conduction in the ANS is slower.* The SNS motor neurons (GSE, or general somatic efferents) are heavily myelinated, conduction is rapid.
Give some of the characteristics of pre-vertebral ganglia.
1.) Not paired 2.) Occur only in the pelvis and abdomen 3.) All lie anterior to the vertebral column.
The sympathetic preganglionic fibers will synapse at what locations?
1.) Paired ganglia in the sympathetic trunk 2.) Collateral ganglia that are unpaired (prevertebral?) 3.) Adrenal medulla
List the functions of the autonomic nervous system.
1.) Regulates body temperature 2.) Regulates cardiovascular function 3.) Regulates respiration 4.) Coordinates digestion 5.) Coordinates excretory function 6.) Regulates reproductive functions 7.) Adjusts internal water 8.) Adjusts fluid electrolytes 9.) Adjusts nutrients in tissue fluids 10.) Adjusts dissolved gas concentrations in body fluids
The enteric nervous system reflex is...
A complete three-neuron reflex arc that exists entirely within the wall of the digestive tube.
What is Horner's syndrome?
A condition that arises due to damage of the sympathetic trunk. Common symptoms include ptosis, miosis (constricted pupil), and anhidrosis (decrease/loss of sweating).
How does the anatomy of parasympathetic outflow indicate that its effects are more specific than the sympathetic nervous system?
A typical preganglionic fiber of the parasympathetic nervous system will synapse on 6-8 ganglionic neurons that are all located in the same ganglia. This differs from the sympathetic nervous system in which a preganglionic fiber will synapse with multiple neurons in different ganglia.
Give the sympathetic effect on skeletal muscle.
Accelerates blood flow to the skeletal muscles. Stimulates energy production and use by the skeletal muscles.
Since the sympathetic nervous system is able to release NE from its postganglionic nervous system, what function does the adrenal medulla play?
Acts as a postganglionic neuron that releases the neurotransmitter into the blood stream as a neurohormone. This way residual NE remains in your body for an extended period of time after the stress stimulus goes away in case you need it again.
Give the sympathetic effect on hair.
Affects arrector pili muscle contraction.
What is Hirschsprung's disease?
Also known as congenital megacolon. This is a birth defect where parasympathetic innervation of the distal colon fails to develop. Neural crest cells fail to migrate. Feces and gas accumulate proximal to the affected bowel segment. Results in tremendous distention and hypertrophy of the sigmoid and descending colon. Can be corrected with surgery.
What are the parasympathetic plexuses?
Cardiac, pulmonary, esophageal, Celiac, hypogastric, and the superior mesenteric plexus.
Give the sympathetic effect on sweat glands.
Causes sweat.
Give the sympathetic effect on lungs.
Dilate respiratory air tubes.
In the male reproductive system, the parasympathetic nervous system is responsible for ________ and the sympathetic nervous system is responsible for _______.
Erections. Ejaculations.
What is hyperhidrosis?
Excessive sweating. Can be treated with botox. Used to
What organs are affected by the parasympathetic nervous system?
Eye Salivary glands Heart Lungs Stomach Pancreas Liver and gall-bladder Bladder Genitals Only difference from the sympathetic is no skin or adrenal gland innervation. But also note the vast difference in vascular innervation.
What organs are affected by the sympathetic nervous system?
Eyes Skin Salivary Glands Lungs Heart Stomach Pancreas Liver and gall-bladder Adrenal gland Bladder Genitals
What is hyperpyrexia?
Facial blushing (extensive, can be treated). Too much parasympathetic response.
What is Achalasia?
Failure to relax. Autonomic innervation of the esophagus is impaired. Results in the inability to propel swallowed food. Smooth muscle cells inferior to the esophagus are also affected since food cannot enter the stomach. Treatment is either longitudinal incision through the muscle on the inferior end or dilation with a balloon.
True or False: Without consciousness, our vital physiological functions would cease to continue.
False: Even without consciousness, our bodies can continue to carry out vital functions such as our heart beating. This is carried out by the ANS.
True or False: The sympathetic trunk is present in the dorsal and ventral rami.
False: Only the ventral rami.
How might the ANS contribute to HTN?
High amount of stress leads to frequent vasoconstriction. This may increase the size of the smooth muscle and narrow the lumen of the arteries.
What is the general pathway for visceral afferents of the sympathetic nervous system ?
In general, they will follow the course of sympathetic fibers entering the spinal cord at similar spinal cord levels.
Give the sympathetic effect on visceral glands.
Inhibits the activity of muscles and glands of visceral organs.
Give the sympathetic effect on muscles and glands of the esophagus.
Inhibits the muscles and glands in the esophagus.
Give the sympathetic effect on lacrimal, nasal, and salivary glands.
Inhibits their function. I.e. dry mouth.
Give the sympathetic effect on urination and defecation.
Inhibits urination and defecation.
What is the purpose of divergence in the ANS?
It allows for a global response, such as with the sympathetic nervous system and the fight or flight response.
Describe the sympathetic splanchnic pathway.
Preganglionic fibers travel to the sympathetic trunk but will not synapse. They then piggy back onto arteries and travel to target organs. They will then synapse on pre-vertebral ganglia that are close to the target organ. In the abdomen and pelvis the ganglia are on the aorta.
Give the sympathetic effect on adipose tissue.
Releases stored lipids from subcutaneous adipose tissue.
What is one of the big differences between somatic sensation and visceral sensation?
Somatic sensation is very localized and specific. Visceral sensation is more general.
Give the sympathetic effect on the heart.
Speeds up heart rate. Metabolic responses dilates vessels that supplies the heart wall.
Give the sympathetic effect on eyelids.
Stimulates eyelid muscles to keep them open.
Give the sympathetic effect on the eye.
Stimulates iris muscle contraction, dilation of pupil. Also helps to focus the eye for seeing distant objects.
What division of the ANS would be easier to modulate pharmacologically?
The sympathetic nervous system because it releases a different neurotransmitter from the post-ganglionic fibers.
What are the different pathways for a preganglionic sympathetic fibers?
They can travel through the sympathetic trunk. 1.) They can ascend and then synapse. 2.) Synapse at the level of the entry. 3.) They can descend and then synapse. 4.) They can pass through the sympathetic trunk without synapsing to enter an abdominopelvic splanchnic nerve.
What is Reynaud's disease?
This is a condition that is thought to be an exaggerated response of sympathetic vasoconstriction. It is provoked by cold. Characterized by intermittent attacks during which the fingers and toes become pale, blue, and then painful. Extreme cases may lead to gangrene.
Define referred pain
This is pain that is not localized to the specific region that is being stimulated. E.g. heart patients with chest pain that radiates to their left arm.
True or False: All visceral reflexes are polysynpatic.
True
True or False: A sympathetic response in one part of the thoracolumbar region creates a response in all of the thoracolumbar region.
True.
True or False: when visceral organs are cut or scraped, the patient feels no pain.
True.
True or False: There is approximately one sympathetic trunk ganglia for each spinal nerve.
True: however some of the ganglia fuse.
Give the sympathetic effect on blood vessels.
Vasoconstriction, especially cutaneous vessels and vessels that supply blood to body wall organs. Makes skin cold. Accelerates blood flow to skeletal muscles during exercise (because they will dilate).
Sympathetic nerves that innervate the heart exit from the...
cervical ganglia.
Preganglionic fibers of the parasympathetic nervous system innervate the _________ ganglia
peripheral
The general sensory neurons in the visceral system will detect...
stretching, temperature, chemical changes, and irritation within the visceral organs.
