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Flashcards in Autonomic nervous sytem Deck (24):

the different kinds of PNS

Somatic nervous system - consciously controlled, voluntary, sensory receptors and motor neurons to skeletal mm

Autonomic nervous system -involuntary, sensory from visceral organ, motor to smooth mm, cardiac mm and glands

Enteric nervous system - involuntary, sensory from chemical changes in GI tract and stretching it, motor to GI smooth muscle


Different kind of ANS

Sympathetic - fight or flight, increased alertness and metabolic activities in order to prepare the body for an emergency situation

parasympathetic - rest and digest, activities conserve and restore body energy, most output is to smooth muscle and glands of GI tract and respiratory tract


what is autonomic tone

most organs receive innervation from both divisions of ANS, which typically work in opposition to one another
autonomic tone is the balance between Sympathetic and parasympathetic activity


what regulates Autonomic tone

by hypothalamus


which structures only receive sympathetic innervation?

Sweat glands
Arrector pili mm
most blood vessels
adrenal medulla
They exhibit responses by decreasing and increasing sympathetic tone


Sympathetic responses

during physical or emotional stress, Sympathetic division dominates the parasympathetic system

high sympathetic tone favors body functions that can support vigorous physical activity and rapid production of ATP

reduction in body functions that favor storage of energy

emotions can stimulate sympathetic division (fear, embarrassement, rage)


what is the body's response to Sympathetic response?

fight or flight
pupils dilate
heart rate , force of heart contraction and BP increases
airways dilate (faster movement of air into and out of lungs)
BV to skeletal mm dilate
BV to cardiac mm dilate
BV to GI tract constrict
BV to kidneys constrict
BV to liver dilate (glucogenesis)
BV to adipose tissue dilate


Parasympathetic responses

rest and digest
body functions that conserve and restore body energy during times of rest and recovery


What is the body response to parasympathetic response


decreased heart rate
decreased diameter of airways
decreased diameter of pupils


classification of nerve fibers

A fibers: largest diameter, myelinated, brief absolute refectory period, fast, sensory neurons, motor neurons to skeletal mm

B fibers: medium diameter, myelinated, medium absolute refractory period, conduct nerve impulses from visceral to CNS

C fibers: smallest diameter, Unmyelinated, longest absolute refractory period, pain from viscera, all postganglionic neurons


Sensory input for somatic nervous system

From receptors for somatic senses (tactile, thermal, pain, proprioceptive sensations) and from receptors for special senses (sight, hearing, taste, smell, equilibrium). consciously received


Autonomic nervous system sensory input

from interoreceptors (sensory receptors located in BVs, visceral organs, mm and nn that monitor conditions in the internal environment)
not usually consciously perceived.)
Chemo, baro, mechano (bv) receptors


Somatic Nervous system control of motor output

Primary motor area of cerebral cortex
voluntary (with contributions from basal nuclei, cerebellum, brain stem and SC)


Autonomic nervous system control of motor output

involuntary control from hypothalamus


Somatic nervous system motor neuron pathway

one neuron path way
somatic motor neuron goes from CNS to skeletal mm
from anterior horn
release Ach


Autonomic Nervous system Motor neuron pathway

Preganglionic neuron is myelinated but postganglionic neuron is not
two neuron pathway
Either release Ach or Norepinephrine (or NE or Einephrine in Chromaffin cell in adrenal gland)


autonomic motor pathways 3 may parts

1. preganglionic neuron (Thorocolumbar division/sympathetic division)
2. Postganglionic neuron
3. Autonomic ganglia (Sympathetic division and parasympathetic division)


Types of sympathetic division

1. sympathetic trunk ganglia/vertebral chain ganglia/paravertebral ganglia (superior, middle, inferior cervical ganglia) for organs above diaphragm T1-L2 or 3

2. Prevertebral (collateral) ganglia (Celiac, superior mesentric, inferior mesentric, Aorticorenal, Renal ganglia) for organs below diaphragm


Parasympathetic division

Terminal (intramural) ganglia
most of these are located close to or within the wall of a visceral organ
Ciliary ganglion
Otic ganglion
Pterygopalatine ganglion
Submandibular ganglion


4 ways Sympathetic preganglionic neurons connect with postganglionic neurons

1. In the first ganglion it reaches
2. the axon may ascend or decend to a higher or lower ganglion nd synapse there
3. The axon may go through the sypathetic trunk ganglion to synapse in a prevertebral ganglion
4. The axon may pass through the sympathetic trunk ganglion and prevertebral ganglion to synapse with chromaffin cells of the adrenal medulla


What is divergence

a single sympathetic preganglionic fiber has many axon collaterals and may synapse with 20 + post ganglionic neurons. that's how sympathetic responses affect almost the entire body simultaneously


Where does parasympathetic preganglionic neurons pass?

To terminal ganglia near or within a visceral effector


why are parasympathetic response localised to a single effector

because it only synapses with 4 or 5 postsynaptic neurons and all of them supply a single effector


what is autonomic plexuses

Tangled neworks of axons of sympathetic and parasympathetic neurons in thorax, abdomen and pelvis
also contain sympathetic ganglia and axons of autonomic sensory neurons