1. Autonomic Nervous System
Chapter 12 1

2. So much of what happens within us, is automatic!!
When we are eating – we do not make an effort to increase flow of our digestive enzymes or increase the rate of contraction of intestinal muscle to enhance the digestive process…

3. Autonomic (visceral) Reflexes
Similarly to the knee-jerk (patellar) reflex….there are also visceral reflexes…
They are mediated by the Autonomic nervous system
Visceral reflexes regulate organ function
Such as… heart rate, BP, body temperature, digestion, airflow through respiratory passages, elimination and pupillary responses

4. Pathways.. Activation of a receptor
Transmission of sensory information to the CNS
Processing of the information of the CNS
Motor response sent to receptor organ
Example…
A sudden decrease in BP activates pressure receptors (baroreceptors)
the info about low BP is carried to the medulla oblongata in the brain stem by sensory nerves -
the medulla oblongata determines that the BP is low and sends motor signals to the visceral effector organs (heart and blood vessels)
motor responses results in changes in the heart and blood vessels that elevate the blood pressure

5. Division of the Autonomic Nervous System
The ANS is part of the peripheral nervous system that supplies motor activity to the visceral effector organs: glands, smooth muscles w/in organs, and heart.
Two divisions:
Sympathetic – causes the body to become more active
Fight or Flight
Parasympathetic – mostly involved w/ relaxation

6. A single organ often receives fibers from both divisions of the ANS = dual innervation – typically opposing effects on organ when stimulated. One Exception…
Example… the cell of the heart that determine rate – receive both sympathetic and parasympathetic fibers.
Stimulation of the sympathetic fibers increases heart rate
Stimulation of the parasympathetic fibers decreases heart rate

7. Sympathetic Parasympathetic
Heart
Increases rate, strength of contraction
Decreases rate, no direct effect on strength
Bronchial tubes
Dilates (incr airflow)
Constricts
Iris of Eye
Dilates (pupils enlarge)
Blood vessels
No innervation
Sweat glands
Stimulates
Intestines
Inhibits motility
Stimulates motility/secretion
Adrenal medulla
Stimulates secretion of epinephrine/norepinephrine
No effect
Salivary glands
Stimulates thick secretion
Stimulates watery secretions

8. Sympathetic Nervous System Fight or Flight
Activated during periods of stress/feelings of threat
Causes you to prepare to either confront (fight) or remove yourself from the situation (flight)
Periods are usually short-lived
Prolong periods of high alert/stress…takes it’s toll on the body – stress-induced illnesses!
Laughter, play, rest, relaxation diminish sympathetic outflow

9. Parasympathetic Nervous System Feed and Breed
Most active during quiet, no-stressful conditions
Plays important role in regulation of digestion and reproductive function “resting and digesting”
Paradoxical fear… although sympathetic system is associated w/ fear – the parasympathetic system can be stimulated when the situation seems hopeless – fight or flight seems futile.
Massive parasympathetic discharge can result in severe low heart rate – fainting/possible death
Uncontrolled urination/defecation

10. Autonomic Terminology Pharmacology
Sympathomimetic – a drug that mimicks the effects of the sympathetic nervous system
Increases heart rate, force of cardiac contratcion and blood pressure
Sympatholytic – a drug that inhibits the effects of the sympathetic system
Prevents an increase in cardiac activity when the sympathetic nerves are fired
Parasympathomimetic – mimicks the effects of the parasympathetic nervous system
Decreases heart rate, increases digestive activity
Parasympatholytic – drug that prevents activation of the parasympathetic nervous system
If the heart is suffering the effects of a parasympathetic system…these drugs can reverse the effects - Atropine