Autonomic Nervous System

Question 1

Autonomic Nervous System

Answer 1

The autonomic nervous system (ANS) is sometimes called the involuntary or visceral nervous system because it mostly functions with the person having little conscious awareness of its activity. Working closely with the endocrine system, the ANS helps regulate and integrate the body’s internal functions within a relatively narrow range of normal on a minute-to-minute basis. The ANS integrates parts of the central nervous system (CNS) and peripheral nervous system to automatically react to changes in the internal and external environments.

The main nerve centers are the hypothalamus, medulla, and spinal cord.

Branches into the…
1. Sympathetic/adrenergic nervous system= fight or flight, accelerate speed.

2. Parasympathetic/cholinergic nervous system= rest and digest.

It regulates...
Temperature
Tears
Pupil dilation
Blood vessel dilation
Heart rate
Blood pressure
Breathing rate
Digestion
Blood sugar

Question 2

Sympathetic Nervous System

Answer 2

Prepares the body to respond to stress (flight or fight)

Stress can be internal, such as cell injury or death, or external, such as a perceived or learned reaction to various external situations or stimuli. For the most part, the SNS acts much like an accelerator, speeding things up for action.

It “dries you out” per Magaletto. The body moves blood away from the periphery to the heart. Other effects are…

• Increased BP, heart rate, respiratory rate
• Bronchi dilation
• Increased contractility
• Mydriasis=pupil dilation. MY what big eyes you have.
• Sweating
• Piloerection (generates heat)
• Glyconeogenesis and Glycogenolysis for energy
• Release of corticosteroids
• Suppress immune and inflammatory responses

Question 3

Transmitters vs Receptors

Answer 3

Transmitters (chemicals)…

• ACh/Acetylcholine, parasympathetic nervous system (released by preganglionic nerves to communicate with postganglionic fibers)
• NE/Norepinephrine, sympathetic nervous system
• EPI/epinephrine, adrenal medulla

Receptors…

Cholinergic (parasympathetic):
Neurons that use ACh as their neurotransmitter are called Cholinergic neurons. Cholinergic/ACh receptors found on organs and muscles.
-Nicotinic: located in the CNS, the adrenal medulla, the autonomic ganglia, and the neuromuscular junction. Stimulation of nicotinic receptors causes skeletal muscle contractions, autonomic responses such as signs and symptoms of a stress reaction, and release of norepinephrine and epinephrine from the adrenal medulla. It increases B/P, HR and peripheral vasoconstriction.
-Muscarinic: found in visceral organs, such as the GI tract, bladder, and heart, in sweat glands, and in some vascular smooth muscle. Stimulation of muscarinic receptors causes pupil constriction, increased GI motility and secretions, increased urinary bladder contraction, decreased HR and B/P.

Question 4

Alpha Receptors

Answer 4

Alpha1-receptors are found in blood vessels (vasoconstriction= raise in B/P), iris dilation (mydriasis,) and in bladder (tightens urinary sphincter). PART OF FIGHT OR FLIGHT RESPONSE.

Alpha2-receptors helps prevent overstimulation of effector sites. These receptors are also found on the beta cells in the pancreas, where they help moderate the insulin release stimulated by SNS activation.

Overall, alpha response is vasoconstriction (cns stimulation?)

Question 5

Beta Receptors

Answer 5

Beta 1- (remember Beta ONE= ONE heart). In cardiac tissue, increases contractility, HR and B/P. The beta effects are smooth muscle relaxation and cardiac stimulation.

Beta 2- (remember Beta TWO= TWO lungs). Found in smooth muscle blood vessels. Causes vasodilation.

• Bronchi dilate
• Uterus relaxes
• Increased muscle/liver breakdown of glycogen
• Increase glucagon secretion from alpha cells in pancreas

Question 6

Adrenergic Drugs

Answer 6

An adrenergic agonist is also called a sympathomimetic drug because it mimics the effects of the sympathetic nervous system (SNS). The therapeutic and adverse effects associated with these drugs are related to their stimulation of adrenergic receptor sites. Stimulates alpha and beta receptors.

Medications:

• Epinephrine treats acute cardiac arrest, respiratory and allergic disorders, hypotension.
• CONTRAINDICATIONS are cardiac dysrhythmias, hypertension, glaucoma, pregnancy, lactating.

Question 7

Parasympathetic nervous system

Answer 7

“Wet stage” per Magaletto

SLUDGE
Salivation
Lacrimation (tears)
Urinary incontinence
Diarrhea
GI cramps
Emesis

Question 8

Anticholinergic drugs

Answer 8

Medication: Atropine Sulfate. Is an antidote for excessive dose of cholinergic drug.

Block parasympathetic nerve impulses by competing with ACh sites on muscarinic receptors.

Mechanism of action:
Occupy receptor site PNS
Stimulate CNS
Increase HR
Bronchodilation
Decreased respiratory tract secretions
Antispasmodic effect on GI
Mydriasis

Used pre-op to decrease secretions. I Also used to increase HR during bradycardia and used to dilate pupils during eye exams.

Adverse effects:
Dry mouth
Dry eyes
Difficult urination
Constipation
Tachycardia
Confusion

CONTRAINDICATIONS: 
Paralytic ileus
Asthma or COPD
BPH (benign prostate hyperplasia)
Glaucoma
MI/tachycardia
Impaired liver or kidney funciton

OVERDOSE:
Inability to sweat
Dry secretions
Difficulty voiding
Flushed skin
Mental confusion
Weakness

ANTAGONIST:
Physostigmine
CONTRAINDICATION:
Hypertension
Asthma
Glaucoma
BPH