Autonomic nervous system

parasympathetic nervous system

-it is an energy conservation-restorative system. It regulates those activities that conserve and restore body energy during times of rest and recovery -it dominates over sympathetic activity in the glands and smooth muscle of the gut, stimulating glandular secretion and the gut movements necessary for food to be digested and absorbed -The acronym SLUD stands for salivation, lacrimation, urination,and defecation, all controlled by the parasympathetic nervous system

sympathetic nervous system

-it prepares the body to meet emergency demands and is primarily involved with processes that expend energy. During physical or emotional stress, the sympathetic division dominates the parasympathetic system, initiating a series of activities known as the flight-or-fight response -this includes increased heart rate, force of contraction, and blood pressure; increased blood flow to essential structures (brain, lungs, heart, skeletal muscles) and decreased activity in nonessential ones; increased rate and depth of respiration -In addition, there is activation of the adrenal medulla, causing secretion of norepinephrine and epinephrine as hormones to greatly heighten the response

ANS consists of two types of neurons..

1. visceral afferent (sensory) neurons- provide a continual flow of info to the CNS from the viscera and blood vessels 2. visceral efferent (motor) neurons- provide motor innervation to the various effectors (cardiac muscle, smooth muscle, and glands)

Relative length of fibers

Because of the closeness of the spinal cord to the sympathetic chain ganglia and the collateral ganglia, sympathetic preganglionic neurons are fairly short. Because of the distance between the brain or spinal cord and the innervated organs, parasympathetic preganglionic fibers are relatively long

postganglionic neurons of the two systems

Because of the locations of ganglia, sympathetic postganglionic fibers are relatively long while parasympathetic postganglionic fibers are relatively short. Regardless, all postganglionic neurons of either system have their axons pass from their respective ganglia to the effector for innervation

ANS neurotransmitters

Cholinergic or adrenergic Neurotransmitter: c- acetylcholine a- norepinephrine which neurons use this neurotransmitter?: c- all preganglionic neurons, all postganglionic parasympathetic neurons, and a very few postganglionic sympathetic neurons. a- most postganglionic sympathetic neurons enzymes used to destroy neurotransmitter?: c-acetylcholinesterase. a- catechol-O-methyltransferase or monoamine oxidase

dual innervation

In general, if one division starts or increases the activity of an organ, the other division will stop or decrease the activity

what ANS division controls autonomic tone?

In general, we are in parasympathetic tone, except during states of emergency when we immediately switch to sympathetic tone

what is the origin of the sympathetic division

Sympathetic preganglionic neurons originate from the lateral gray horns of spinal cord segments T1-L2. Their axons travel in the spinal nerves of these segments. Therefore, the sympathetic division is called the thoracolumbar division and the preganglionic axons are called the thoracolumbar outflow

where is the cell body of the postganglionic neuron

THe cell body is located in a specific ganglion. The location of the ganglion is dependent upon the division of the ANS to which the neuron belongs and which organ it will innervate

Terminal ganglia

The parasympathetic division uses these and they are located very close to or within the walls of the organ to be innervated

axon of preganglionic pass from the CNS

The preganglionic axon passes from the CNS in a spinal or cranial nerve

innervation causing excitation and inhibition at the same time

This is possible because the postganglionic neurons use different neurotransmitters and the effectors bear different receptors

what is a ganglion

a collection of nerve cell bodies located in specific site within the body, but outside the CNS

sympathetic chain ganglia

are located in a series that lies in a vertical row on either side of the vertebral column, extending from the base of the skull to the coccyx

how does the ANS opperate

it operates without conscious control, relying on reflex arcs that are dependent upon the hypothalamus and medulla for overriding control

where does the axon of the postganglionic neuron terminate

it passes from the ganglion to the effector

where does the preganglionic axon terminate?

it terminates in the ganglion

Prevertebral Ganglia

les as three clusters associated with the three unpaired arteries arising from the abdominal aorta (celiac, superior mesenteric, and inferior mesenteric). These ganglia are used by the sympathetic division

what is the origin of the parasympathetic system

parasympathetic preganglionic neurons arise from the nuclei of cranial nerves III, VII, and X, and the lateral gray horns of spinal cord segments S2-4 . For this reason, the parasympathetic division is also called the craniosacral division and the preganglionic axons are the craniosacral ourflow

two types of visceral motor neurons

preganglionic and postganglionic

comparison of somatic and autonomic nervous systems

receptor type: S- cutaneous, proprioceptors, special sense. A- chemoreceptors, baroreceptors, mechanoreceptors Conscious: S- may become conscious. A- unconscious Excitatory or inhibitory: S- excitatory of skeletal muscles only. A- excitatory or inhibitory for cardiac, and smooth muscles and glands number of motor neurons: S- single motor neuron. A- two motor neurons

general functions of the autonomic nervous system

regulates the activities of cardiac muscle, smooth muscle, and glands

two separate divisions of the ANS

sympathetic and parasympathetic nervous systems

cell body of the preganglionic neuron

the cell body is located in gray matter of the spinal cord or brain

controller of autonomic tone

the hypothalamus regulates the balance of sympathetic versus parasympathetic activity or tone

parasympathetic response

the parasympathetic system has very little divergence in the connections between preganglionic and postganglionic fibers, so that only very small areas of effectors are stimulated at any given time. Also, acetylcholine is rapidly destroyed in the synaptic clefts, so that the response to neurotransmitter is very short-lived

what effect does the postganglionic neuron have on the effector

the peripheral effector (cardiac muscle, smooth muscle, or gland) is either stimulated or inhibited, depending upon which division of the ANS is being discussed

sympathetic response

the sympathetic system has a good deal of divergence between preganglionic and postganglionic fibers (1:5-500), so that the sympathetic message is sent body-wide. Secondly, norepinephrine is poorly removed from the synapse, so that it diffuses into the bloodstream for delivery throughout the body. Lastly, activation of the sympathetic nervous system results in secretion of norepinephrine and epinephrine, hormones that have stronger and body wide effects