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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?

Prefrontal cortex


What happens in paraplegic patients that interferes with emptying the bladder?

Loss of the reciprocal relationship between the bladder and the sphincter

detrussor-sphincter dyssynergia


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

2. hypertonicity:
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)


What is the process of milk ejection reflex?

suckling==> hypothalamus

--> posterior pituitary --> oxytocin==> eject milk

--> anterior pituitary --> prolactin--> milk production