Module 10.1-10.2 AUTONOMIC NERVOUS SYSTEM

Organization of the Nervous System: -The human body is composed of one nervous system that can be subdivided into a central nervous system (CNS) and a peripheral nervous system (PNS). -The brain and spinal cord make up the CNS, while the PNS is made up of any nervous tissue outside the brain and spinal cord, including 12 pairs of cranial nerves, 31 pairs of spinal nerves, and peripheral sensory receptors. -The PNS can be further subdivided into the ANS (Autonomic Nervous System) and the somatic nervous system depending on which type of muscle it innervates and whether or not it is voluntarily controlled. -The ANS (Autonomic Nervous System) can be subdivided into sympathetic and parasympathetic nervous systems. -It is the sympathetic branch of the ANS that is responsible for the "fright, flight, or fight" response elicited by the encounter with the bear.

-Another example of a sympathetic response that might be a little closer to home would be your body's reaction after being jilted by your fiancé at the alter. - A sympathetic response can also occur during illness or physical trauma, from anxiety, or pretty much any stressful situation. -Such a response is characterized by increased heart rate and blood pressure; goosebumps; pupil(pupil dilation = mydriasis) and bronchiole dilation; and increased blood flow to cardiac and skeletal muscles. -on the other hand, is responsible for energy conserving ("rest and digest") activities, including decreased heart rate, blood pressure, and respiration; constriction of the pupil (miosis); increased secretions and peristalsis of the digestive tract; and increased urination.

ORGANIZATION OF THE NERVOUS SYSTEM: -Introduction : - Your body's reactions to the bear can be summed up as a "fright, flight, or fight" reaction elicited by your central nervous system in response to incoming sensory information from the environment (i.e. seeing the bear, hearing the bear, and maybe even smelling the bear). -During this response, your nervous system also slows down organs of digestion, urination, and defecation, so that all available energy may be used for running away.

-The actions on your heart, lungs, pupils, digestive system, and urinary system have occurred without your conscious awareness and are controlled involuntarily by the autonomic nervous system (ANS).

-Increasing parasympathetic stimulation to the heart will cause decreased heart rate.

-while increasing sympathetic activity will increase heart rate and force of contraction.

The brain and spinal cord make up the

CNS, central nervous system .

Somatic Nervous System

Has 2 parts a SENSORY and MOTOR.

Autonomic ganglia for the sympathetic division include -

SYMPATHETIC CHAIN GANGLIA which are located near the spinal column and COLLATERAL GANGLIA which are located near the organ or effector that they innervate.

Interestingly, if a visceral organ is removed from the body and placed in an oxygenated Ringer's solution, it will continue to undergo peristalsis (wave-like smooth muscle contractions of the gastrointestinal tract) or beat without even being connected to the ANS.

This is called autorhythmicity. -Why then, do you ask, is the ANS even necessary for these organs to function? The answer is - it is not. But the ANS is necessary to regulate the activity of these organs, essentially causing them to speed up or slow down in order to maintain homeostatic conditions in the body.

Usually, each visceral organ is innervated by nerves from both sympathetic and parasympathetic divisions, and effects of these divisions are most often in opposition to one another.

This type of "wiring" is called dual autonomic innervation. -The heart is a good example of this. It is innervated by fibers from both parasympathetic and sympathetic divisions that oppose one another. -Increasing parasympathetic stimulation to the heart will cause decreased heart rate, while increasing sympathetic activity will increase heart rate and force of contraction.

The human body is composed of one nervous system that can be subdivided into

a central nervous system (CNS) and a peripheral nervous system (PNS) (see figure below)

The synapse between the postganglionic neuron and the effector is known as

a neuroeffector synapse or neuroeffector junction. -

COLLATERAL GANGLIA

are located near the organ or effector that they innervate.

SYMPATHETIC CHAIN GANGLIA

are located near the spinal column

The actions on your heart, lungs, pupils, digestive system, and urinary system have occurred without your conscious awareness and are controlled involuntarily

by the autonomic nervous system (ANS).

CENTRAL NERVOUS SYSTEM

has 2 parts a Brain and a Spinal Cord.

a ganglion

is a collection of cell bodies located outside the CNS). -These neurons get their names from their anatomical location in relation to autonomic ganglia, or relay centers.

while the PNS, peripheral nervous system

is made up of any nervous tissue outside the brain and spinal cord, including 12 pairs of cranial nerves, 31 pairs of spinal nerves, and peripheral sensory receptors.

The acronym SLUD (Salivation, Lacrimation Urination, and Defecation)

may be useful to remember some of the responses caused by the parasympathetic division in certain organs. -Other than some sweat and salivary glands, most secretions of the body increase when the parasympathetic nervous system is activated.

The parasympathetic division

on the other hand, is responsible for energy conserving ("rest and digest") activities, including decreased heart rate, blood pressure, and respiration; constriction of the pupil (miosis); increased secretions and peristalsis of the digestive tract; and increased urination.

The ANS innervates visceral organs (the internal organs of the body)

organs which are unconsciously controlled by the brain. -Visceral organs contain either smooth or cardiac muscle; respective examples include the intestines and the heart.

Parasympathetic and sympathetic divisions are "wired" similarly in that they both have a

preganglionic neuron and postganglionic neuron.

The ANS can be subdivided into

sympathetic and parasympathetic nervous systems.

Parasympathetic fibers

tend to have long preganglionic axons and short postganglionic axons.

the sympathetic division

tends to have short preganglionic axons and long postganglionic axons (table 1).

Autonomic ganglia for the parasympathetic division are called

terminal ganglia and these are located very near the effector they innervate.

terminal ganglia

terminal ganglia and these are located very near the effector they innervate.

The cell bodies for preganglionic neurons are located in either

the brainstem or spinal cord, and their axon terminals are located in autonomic ganglia. -In the ganglia, a neuron-to-neuron synapse relays information to the cell body of a postganglionic neuron. - Postganglionic neurons, also located in the autonomic ganglia, then transmit the signal to effectors. -A main difference between parasympathetic and sympathetic divisions is their relative length of preganglionic and postganglionic neurons (see figure 1). -Parasympathetic fibers tend to have long preganglionic axons and short postganglionic axons. -the sympathetic division which tends to have short preganglionic axons and long postganglionic axons (table 1). -The relative location of the ganglia also differs between the two divisions. Ganglia of the sympathetic division are most often located near the spinal cord while those of the parasympathetic are usually near the effectors they innervate (see figure 1).

he parasympathetic division

uses long preganglionic neurons and short postganglionic neurons.

In general, the sympathetic division

uses short preganglionic neurons and long postganglionic neurons