Flashcards in Autonomic Nervous System II Deck (14)
What effect does the PNS have on the pupil?
Constriction/miosis. The pupillary light reflex. CN III
What effect does the PNS have on glands?
Copious secretrion of the nasal, lacrimal, submandibular (CN VII), parotid (CN IX), gastric and pancrease (CN X)
What effect does the PNS have on the GI and heartrate?
It causes peristalsis/ increased motility and sphincter relaxation. Bronchial constriction; decreased heart rate (CN X)
What do sacral nerve S2-S4 do?
They innervate pelvic structures to regulate the lower portion of the GI tract, urinary bladder, and reproductive organs
Where do preganglionic neuronds of the PNS originate?
In the nuclei of the midbrain, pons, and medulla. Also in scral segments S2-S4.
Which cranial nerves house parasympathetic preganglionic fibers?
III - occulomotor; VII - facial; IX - glossopharyngeal; X - vagus
75% of the PNS is controlled by ____
The two vagal nerves
What effect does the PNS have on GI motility?
It exerts a tonic effect. Cutting the PNS would decrease GI wall muscle and sphincter tone.
The myenteric and submucosal plexuses function to do what? How are they stimulated?
The myenteric is responsible for GI motility and the submucosal does secretions. PNS enhances motility and secretion through the Enteric Nervous System while the SNS reduces them
Describe what happens during filling of the bladder in terms of ANS control
Sympathetic control predominates. It causes relaxation of the detrusor muscle (beta 2) and contraction of the internal sphincter (alpha1)
Describe emptying of the bladder in terms of ANS control
During micturition parasympathetic control predominates. The detrusor muscle is contracted (M) and the internal sphincter ins relaxed (M)
What is Vasovagal syncope
(emotional fainting) It begins with disturbing thoughts in the cortex (under cortical control of autonomic input). Activation of vasodilator centers in the hypothalamus and vagal stimulation leading to rapid slowing of the heart. SNS stimulates blood flow to muscles. MAP drops and blood flow to the brain is interupted
What are examples in which visceral afferents overwhelm cortical function (ie. Nothing else matters)
Hunger, nausea, dyspnea, visceral pain, bladder and bowel distention, hypothermia, hyperthermia