Lecture 6 - Visceral Motor Control and the Autonomic Nervous System Flashcards
What are the two branches of the PNS and what are their subdivisions each?
-somatic (voluntary control) and autonomic (involuntary control)
-somatic is broken into sensory afferent neurons and motor efferent neuron
-autonomic is broken into sympathetic and parasympathetic
What is the sympathetic branch?
fight or flight and it active during periods of high stress and also typically in periods in which large amounts of cortisol and norepinephrine are being made and released
What is the parasympathetic branch?
rest and digest and active during periods of low stress
What are the two types of neurons in the sympathetic branch?
-preganglionic neurons - in lateral horn of the spinal cord, myelinated, and release acteylcholine
-postganglionic neurons - found in the sympathetic chain thoracic to lumbar spinal cord or splanchnic ganglia which is found in the lateral proximal sacral spinal cord; unmyelinated and release norepinephrine
What are the two types of neurons in the parasympathetic branch?
-preganglionic neurons - found in the lower brainstem or the upper cervical spinal cord and the sacral spinal cord; release acetylcholine via nicotinic receptors
-postganglionic neurons - found adjacent to target organs in the periphery and they release ACh signal via muscarinic receptors
What cranial nerves provide autonomic control for the eyes and face?
CN III-X
What does the CN X or the vagus nerve provide autonomic control for?
all the visceral organs except the bladder, distal bowels, and genitalia
What is the baroreflex?
modulates blood pressure
What do baroreceptors do?
they are in the aortic arch of the heart and send signal about blood pressure at any moment in time
What sends information about blood gas levels?
chemoreceptors
What do the baroreceptors do when blood pressure is high in the aortic arch?
-they send impulses to the brainstem which is specifically the Nucleus of the Solitary Tract (NTS)
Whats does the NTS stimnulate?
-preganglionic neurons from parasympathetic branch in the Nucleus Ambiguus in the brainstem
What does the nucleus ambiguus do?
project via the CN X or the vagus nerve to the postganglionic neurons in the cardiax plexus which is where acetylcholine is released
Where is the inhibitory signal sent during the baroreflex?
the preganglionic neurons in the sympathetic branch in the thoracic spinal cord which causes a reduction in the amount of norepinephrine released
What are the parasympathetic synapses for the baroreflex?
baroreceptors —-> NTS—–>nucleus ambiggus—–>vagus nerve CN X —-> cardiac plexus ACh release
What are the sympathetic reflexes for the baroreflex?
baroreceptors—–> sympathetic chain ganglion in the thoracic spinal cord —–> reduced norepinephrine release
What is micturition?
urination
What does the sympathetic branch do in micturition?
-relaxes the muscles of the bladder so that it can become full and closes the internal sphincter which is made of smooth muscle meaning it is under involuntary control
What does the parasympathetic branch do in micturition?
-it constricts the bladder to allow for urination and it relaxes both the internal smooth muscle sphincter and the external skeletal muscle sphincter
What does the somatic nervous system do in micturition?
provides sensory awareness of the fullness of the bladder via the dorsal root ganglion and allows for voluntary control over the external sphincter of the bladder since it is skeletal muscle
What is the enteric system and what is it responsible for?
-it is an offshoot of the sympathetic and parasympathetic branches and is responsible for more complex rhythmic motor movements observed in the digestive tract which is known as peristalsis
What is the role of the parasympathetic branch in the enteric system?
-CN X the vagus nerve and the intermediate gray zone in the sacral spinal cord receive input and directly innervate the lining of the digestive tract which make them postganglionic neurons
What is the role of the sympathetic branch on the enteric system?
-input comes from neurons in the prevertebral ganglia
What are the two plexuses that comprise the entire enteric system and what is a plexus?
-myenteric plexus
-submucosal plexus
-bundle of nerves and blood and lymphatic tissue
What is the role of the myenteric plexus?
controls the smooth muscle of the
What is the role of the submucosal plexus?
controls secretions of chemicals for digestion
