Name the two main division of the Autonomic nervous system (ANS)
The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously.
- Parasympathetic
2. Sympathetic
Parasympathetic
To be specific, the parasympathetic system is responsible for stimulation of “rest-and-digest”
Sympathetic
Fight-or-flight:Sympathetic activitydominates.
Sympathetic vs. Parasympathetic Divisions
Two different anatomical sections of PNS.
Usually have opposing actions.
Fight-or-Flight is an extreme situation.
Under normal conditions both branches cooperate to fine-tune activity and blood flow to various organs.
Organization of Autonomic Control
Some processes are controlled via autonomic reflexes; rapid automatic responses, similar to arc reflexes in somatic control; negative feed-back!
Autonomic reflexes may involve only the PNS, or the spinal cord, medulla, hypothalamus and the pons.
ANS also participates in complex behavioral responses that involve motor output from the hypothalamus and brain stem, such as drinking.
Even more complex and emotional responses can involve the limbic system and cerebral cortex.
Draw an autonomic reflex response
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Ganglionic
A group of nerve cells forming a nerve center, especially one located outside the brain or spinal cord.
Autonomic Reflexes
Short reflexes bypass the CNS; common in digestive tract
Long reflexes involve CNS; most organs. e.g., micturition; receptors in urinary bladder, effectors in sphincters
Simple reflexes
are rapid automatic responses that involve the spinal cord
Complex reflexes
involve the medulla oblongata and pons, but are also regulated by the hypothalamus
Where is the soma of a preganglionic neuron from the ANS located?
Lateral gray horn
Flight or fight responses are______
Long complex reflexes or responses originating at the cerebral cortex
Pathways of the ANS
All ANS pathways consist of two efferent neurons; a preganglionic neuron, a ganglion and a postganglionic neuron
Sympathetic synapses use acetylcholine and Norepinephrine (NE, actin on α- and β1- receptors)
Adrenal medulla (sympathetic) secretes Epinephrine (E, acting on β1- or β2-receptors)
Parasympathetic synapses use only acetylcholine
How many motor neurons does the ASN require in order to conduct an action potential to the eye?
2 motor neuron
The vagus nerve contains ______
Preganglionic fibers of the parasympathetic division
The adrenal medulla…
contains neurons that secrete adrenaline, therefore playing a neuroendocrine role.
Autonomic Synapses
Postganglionic neurons of the ANS have varicosities (like an string of pearls) at their synapses.
Most varicosities of the sympathetic division secrete NE as neurotransmitter, which is quickly degraded at the synapse.
NE at the bloodstream degrades slowly.
The Adrenal Medulla
Contains Neuroendocrine cells that secrete Epinephrine (= adrenaline)
Preganglionic fibers directly innervate the adrenal gland (medulla) which is a modified sympathetic ganglion.
Neuroendocrine cells are modified neurons that secrete neurotransmitters into the bloodstream, thus affecting every cell in the organism.
Sympathetic Neurotransmitters and Activation of Receptors
Sympathetic activation results in:
Secretion of Norepinephrine (NE) at the peripheral synapses.
Secretion of Epinephrine (E) into the bloodstream.