ANS 2 Flashcards
Describe the functional effects of normal and abnormal parasympathetic nervous system activation
pupillary constriction/miosis (miosis = constriction) (CN III) - the pupillary light reflex
secretion of glands including the nasal, lacrimal, submandibular (CN VII), parotid (CN IX), gastric, and pancreatic (CN X)
GI peristalsis/increased motility and sphincter relaxation, bronchial constriction; decreased heart rate (CN X)
Note: PNS (splanchnic) fibers emanating from sacral segments S2-S4 innervate pelvic structures to regulate the lower portion of the GI tract, urinary bladder, and reproductive organs
List the major CNS control centers that regulate ANS function
Several autonomic functions are controlled by nuclei in higher areas such as the hypothalamus (aka “the major ganglion of the ANS”), and by nuclei in the midbrain, pons, medulla, and brain stem (e.g., cardiovascular function, respiration, temperature regulation, micturition, thirst, GI motility, and hunger)
Nuclei in the brainstem, pons, & medulla regulate activation of the PNS. In the PNS, preganglionic neurons originate in nuclei of the brainstem (midbrain, pons, medulla) and in sacral segments (S2-S4) of the spinal cord
Describe the effects of visceral afferent activity on ANS function–Digestion
Distention of the gut by ingestion of food activate mechanoreceptors and chemoreceptors in the epithelial lumen that innervate central control centers to activate the PNS (and inhibit the SNS) to promote digestion via enhanced motility and secretions. The PNS through the vagus & pelvic nerves act on the independent enteric nervous system to enhance motility & secretions by acting on the myenteric and submucosal plexuses.
The sympathetic nervous system influences the vasculature of the gut by vasoconstriction & reduces motility and secretions.
Explain the roles of the SNS and PNS in maintaining homeostasis in different contexts (e.g., stress, digestion, exercise)
To solve problems for this think:
PNS = rest & digest
SNS = fight or flight
Both the sympathetic & parasympathetic nervous systems act on which type of nicotinic receptor?
N2
Note, Hexamethonium blocks N2 receptor
Secretions are under PNS or SNS
PNS exclusively
The dorsal motor nucleus of the vagal nerve lies in the?
Medulla (of the brain)
The nucleus ambiguous belongs to what CN?
Vagus
The nucleus tractus solitarius or NTS regulates what?
Mean arterial pressure
Note: NTS is not part of the autonomic nervous system
Describe the effects of visceral afferent activity on ANS function–Urination or micturition
During filling of the bladder, sympathetic control predominates, causing relaxation of the detrusor muscle and contraction of the internal sphincter.
During micturition (urinatin), parasympathetic control predominates, causing contraction of the detrusor muscle and relaxation of the internal sphincter. The relaxation of the external sphincter which initiates urination is voluntary.
a1, Adrenoreceptor in internal sphincter; B2, adrenoreceptor in detrusor muscle
Describe the effects of descending cortical control on ANS function
Descending cortical pathways regulating fear, panic, stress, etc responses through the ANS may be via direct connections in the spinal cord or indirect through the hypothalamus
Blood flow to which organ is controlled primarily by the sympathetic nervous system rather than by local metabolites?
Skin
The sympathetic nervous system is further characterized by short preganglionic neurons that synapse in ganglia located in the paravertebral chain or prevertebral ganglia (not in the effector organs) and postganglionic neurons that release _____ not _______.
The sympathetic nervous system is further characterized by short preganglionic neurons that synapse in ganglia located in the paravertebral chain or prevertebral ganglia (not in the effector organs) and postganglionic neurons that release norepinephrine (not epinephrine).
