3 - Autonomic Nervous System (copy)

What is the autonomic nervous system (ANS)?

• Controls blood vessels and internal organs

• Divided into 2 system: sympathetic and parasympathetic nervous systems

Sympathetic nervous system

Prepares the body to deal with emergency situations

Parasympathetic nervous system

Maintains homeostasis

What are the key functions to the sympathetic nervous system?

• Regulation of blood flow sent to organs and tissues during an emergency

• Via vasoconstriction to skin, skeletal mms (such as the masseter or something not essential in an emergency and GI tract)

• Via vasodilation to skeletal muscles (legs, arms, etc.)

Sympathetic nervous system can shunt blood around the body as needed

True

Sympathetic neurons

• Have cell bodies in the spinal cord at T1-L2

• Sympathetic axons

• Exit spinal column → Enter sympathetic trunk (one on each side of the vertebral column

Specific function of the sympathtic nervous system (thoracic)

• Regulates flow of blood to the skin and skeletal muscle; Ex: Turn pale if afraid due to vasoconstriction in the skin

• Shunts blood to organs most in need of blood during an emergency; Ex: Increased availability of blood to the heart for increased cardiac output

• Innervate smooth muscles of the eye (causes pupil dilation)

• Innervate salivary glands - Causes production of thick mucus

• Dilation of trachea and bronchi - Allows more air to enter the lungs

• Innervate the heart - Causes increased strength of contraction and increased heart ratee

Specific Functions for the Sympathetic Nervous System (Abdomen and Pelvis)

• Axons form 3 splanchnic nerves

• Innervate walls of the digestive tract , pelvic organs and blood vessels that supply these organs

• Decrease function of digestive and urinary systems

• Cause vasoconstriction to raise BP

• Innervates the adrenal gland

• Causes an “adrenaline rush”

What are the 2 neurotransmitters of the sympathetic nervous system?

• Acetylcholine (Ach)

• Norepinephrine (NE)

Acetylcholine (Ach)

Cholinergic synapses that are found on sweat glands and arterioles that supply skeletal muscles

• Vasodilation and increased blood flow to skeletal muscles

• Sweating and cooling of the body

Norepinephrine (NE)

Adrenergic receptors in multiple locations in the body

• General vasoconstriction and increased systemic blood pressure

• Increased heart rate and contraction strength

• Relaxation of airways

• Decreased digestion and urinary function

Parasympathetic neurons

• Travel with cranial or spinal nerves to innervate cardiac or smooth muscle cells

• Cell bodies are in the brainstem or sacral plexus

• DO innervate internal organs - DO NOT innervate skin, muscles or blood vessels

• All neurons release Acetylcholine (Ach)

Specific Functions of the Parasympathetic Nervous System

• Innervate the pupillary constrictor muscle of the eye and allow the shape of the lens to change • Results in constriction of the pupil • Allows the lens to focus on close objects • Innervate the lacrimal glands • Produce tears • Innervate the salivary glands • Produce salivation

• Contains the Vagus nerve (CN X) which contains parasympathetic neurons

• Parasympathetics from the sacral region form pelvic splanchnic nerves

Functions of the the vagus nerve (associated with the parasympathetic nervous system)

• Slows heart rate

• Decrease heart contraction strength

• Constrict the trachea and bronchi

• Stimulate activity of the liver, gall bladder and pancreas

Functions of the pelvic splanchnic nerves (in association with the parasympathetic nervous system)

• Stimulate bladder emptying

• Stimulate vasodilation of erectile tissue

• Increase motility of the lower GI tract and control defecation

Autonomic nervous system is controlled by the hypothalamus

True

Central autonomic fibers

Neurons from the hypothalamus run through brainstem (travelling within the reticulospinal tracts) to synapse on autonomic neurons

How does the hypothalamus control the autonomic nervous system?

1.) “Thermostat” in the hypothalamus registers that the body is too hot 

2.) Hypothalamus sends a signals through the central autonomic fibers to the sympathetic nervous system to cause sweating 

3.) Sweating cools the body off

How is the limbic system related to the hypothalamus?

The connection between the two account for the physiological changes as a result of emotions

Autonomic Dysreflexia

• A risk for patients with a spinal cord injury above T6

• Most of the autonomic nervous system is disconnected from the hypothalamic control center

• Patient cannot feel painful stimulus such as a pressure sore, tight clothing or shoes, blocked/kinked catheter

• Body has a large sympathetic response (Continually increasing blood pressure) even though stimulus isn’t felt

• Due to lesion, parasympathetic signals at level of lesion are blocked and can’t mediate sympathetic response

• Parasympathetic response above level of lesion causes bradycardia and vasodilation

• Patients experience a pounding headache, flushing of the skin and sweating above the level of the lesion

How should you react to an episode of autonomic dysreflexia?

• Fixing the problem but alerting other healthcare professionals to the emergency 

• Look for and fix kinked lines (or empty a catheter bag)

• Sit patient upright on EOB

Complex Region Pain Syndrome

• Abnormal response of the sympathetic nervous system to injury

• Used to be called RSD

• Symptoms include intense, burning pain in the affected area, swelling, edema and red, shiny skin

• Patients are typically hesitant to have the area touched or to move it

*Important in relation to contrast bath (keeping the temps milder)

Symptoms of Dysautonomia

• Bradycardia or tachycardia

• Syncope

• Chronic fatigue

• Large fluctuations in HR and BP

• Frequent nausea and GI dysmotility

• Migraines

• Temperature dysregulation

• Dysphagia

• Balance disturbances