Chapter 14 ANS

Fibers originate in the thoracic and lumbar spinal cord, T1-L2

Fibers originate in the brain stem through cranial fibers or in the inferior sacral spinal cord

Constricts visceral and sometimes cutaneous blood vessels, this shunts blood to active skeletal muscles and the heart

dilates the bronchioles in the lungs, increasing airflow and increasing oxygen delivery to blood cells

stimulates the liver to release more glucose into the blood to accommodate the increased energy needs of body cells

blood pressure and heart rate are regulated at low normal levels

active digestion of food in gastrointestinal tract

eliminating feces and urine

Cervical plexus nerve that contains fibers from both the parasympathetic and sympathetic divisions

supplies virtually every organ in the thoracic and abdominal cavities

Preganglionic axons of the Vagus nerve originate from the dorsal motor nuclei of the medulla

synapse in the terminal ganglia usually located in the walls of the target organ

Cardiac plexus which supplies fibers to the heart that slow the heart rate

Pulmonary plexus that serves the airways of the lungs

Esophageal plexus which serves the esophagus and part of the stomach

Visceral pain afferent fibers travel in the same paths as somatic pain fibers and arrive at the same spinal cord segment

This is why pain stimuli from the viscera are perceived as somatic pains

The body maintains internal conditions at a relatively narrow range to maintain homeostasis amidst constantly changing internal and external conditions 

Both autonomic divisions serve the same visceral organs but cause opposite effects

While one stimulates certain smooth muscles to contract or a gland to secrete, the other inhibits action

parasympathetic - no effect

sympathetic - secretes epinephrine and norepinephrine

Thermoregulatory responses to heat

Release of renin from the Kidneys

Metabolic effects

When systemic body temperature rises, sympathetic nerves

  —> dilate the skin’s blood vessels allowing heat to escape 

  —> active the sweat glands to help cool the body

When systemic body temperature falls, sympathetic nerves

  —> skin blood vessels constrict preventing heat loss from the skin

Sympathetic impulses stimulate the kidneys to release renin, an enzyme that causes the formation of potent blood-pressure increasing hormones 

Through both direct neural stimulation and the release of adrenal medullary hormones, the sympathetic division promotes metabolic effects not reversed by parasympathetic activity

-Increases the metabolic rate of body cells

-Raises blood glucose levels

-Mobilizes fats for use as fuels

sympathetic nervous system

shorter nerve pathways

faster-acting neurotransmitter

role in fight or flight response

emotional responses of the limbic system to danger and stress signal the hypothalamus to activate the sympathetic system

most direct influence over autonomic functions

cardiac and vasomotor centers

medullary regions oversee gastrointestinal activities

vagus nerve sends afferents to brain

oculomotor nuclei controls muscles concerned with pupil diameter and lens focus

reflexes for urination, defecation, erection, and ejaculation

Alpha-blocker drugs prevent Epinephrine secreted from adrenal glands from the Sympathetic Division origin from binding to their target receptors on the post-ganglionic neuron

This reduces the amount of vasoconstriction on blood vessels decreasing hypertension in the body

Vascular system almost entirely innervated by sympathetic division

Keeps blood vessels in constant partial constriction

Slows heart rate and Dictates normal activity of digestive and urinary tracts

Visceral sensory neurons send information about chemical changes, stretch and irritation of viscera

adrenal gland

sweat gland