Flashcards in Autonomics -Martin Deck (15):
How do PNS fibers control micturition?
Parasympathetic preganglionic fibers (S2–S4) and travel in sacral roots and pelvic nerves (PEL) to ganglia in the pelvic plexus (PP) and in the bladder wall
PNS fibers release ACh onto M3 receptors causing the bladder to contract. They also release ATP caring excitation of the bladder smooth mm and nitrous oxide which causes a relaxation of the sphincter
How do sympathetic fibers control micturition?
Sympathetic postganglionic neurons (hypogastric N) release NE, which activates β3 adrenergic receptors to relax bladder smooth muscle and activates α1 adrenergic receptors to contract urethral smooth muscle
How do somatic axons control micturition?
Somatic axons in the pudendal nerve release ACH, which produces a contraction of the external sphincter striated muscle by activating nicotinic cholinergic receptors
Where does conscious control of micturition take place?
What happens in paraplegic patients that interferes with emptying the bladder?
Loss of the reciprocal relationship between the bladder and the sphincter
What is the emetic reflex?
chemoreceptors in the stomach and intestine send signals via the vagus and sympathetic nerves to the chemoreceptor trigger zone in the area postrema of the medulla--> reticular formation of the medulla --> visceral and somatic efferents
How do autonomic reflexes differ from visceral reflexes?
have autonomic motor fibers in the efferent arm and/or have afferent input from non-visceral tissues or organs.
autonomic synapses are also spread out along the smooth mm tissue (skeletal=localized)
What are some visceral reflexes? What are some autonomic reflexes?
Visceral: micturition and emesis
autonomic: deglutition, salivation, blood pressure
hypothalamic reflexes: body temp, thirst, milk ejection
What are the 3 phases of deglutition?
esophagial=parasympathetic, myenteric plexus, peristalsis
What would a lesion to the esophageal plexus cause?
achalasia (excess tension in LES)
– can be treated with botulinum toxin
What will happen to the deglutition in a person with a left-sided stroke?
A right sided stroke?
dysphagia in both= difficulty swallowing
Left sided stroke: interferes with oral phase--> initiating activity
right sided: pooling of food in pharynx and aspiration of food
What are involved in the salivation reflex?
afferent (mouth=glossopharyngeal, lower esophagus=vagus)
--> integration in salivary nuclei in the medulla--> PNS efferent to via CN 9 and 7
--> SNS to the submandibular gland (not the parotid)
What causes fevers?
changes in the response threshold of the hypothalamic neurons
Chill during fever produced due to activation of receptors monitoring peripheral vasoconstriction.
Interleukin 1 beta, and other endogenous pyrogens may induce changes in set-point via local release of prostaglandin E2.
What are the 2 types of thirst?
1. hypovolemia: Decreased blood flow to kidney → renin→AII →subfornical organ →Hypothalamic AVP↑
baroreceptors →NTS → sympathetic activation →constriction of arterioles
Hypertonicity sensed by OVLT (anterior hypothalamus)→ AVP(=vasopressin=ADH) ↑
AVP in very small amounts reduces loss of water in urine
both have the same behavioral response but 2 different afferent paths (converge on the hypothalamus) (vasoconstriction will occur with hypovolemia and not hypertonicity)