Chapter 16-17: Nerve tracts and the Autonomic Nervous System Flashcards Preview

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Flashcards in Chapter 16-17: Nerve tracts and the Autonomic Nervous System Deck (48)
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collateral ganglia: major collateral ganglia

-superior mesenteric
-inferior mesenteric
-deal for the most part with the digestive processes


adrenal (suprarenal) medullae

-presynaptic fibers go through both the chain and collateral ganglia
-straight to the medulla of the adrenal gland
-stimulate the production of the hormones epinephrine and norepinephrine (adrenaline)
-no postganglionic fibers
-pumps E and NE into blood stream. Unlocalized


effects of sympathetic division

-increase alertness
-energy and euphoria
-excites cardiovascular and respiratory centers
-increased muscle tone
-mobilization of energy


sympathetic activation

-CNS stimulates preganglionic neurons
-preganglionic neurons:
--always release Ach (acetylcholine)
--known as a cholinergic synapse
--stimulates postganglionic neurons
-postganglionic neurons
--usually release NE to an effector
--known as an adrenergic synapse


adrenergic receptors: alpha

-respond to both E and NE
-target smooth muscle
-constrict sphincters and BV's


adrenergic receptors: Beta

-respond to E only
-target skeletal and smooth muscle of respiratory tract
-increase metabolic rate
-usually excitatory


symmary of sympathetic

1. preganglionic fiber is short; postganglionic is long
2. synapsing occurs in sympathetic chain or collateral ganglia
3. preganglionic fiber releases Ach
4. postganglionic fiber releases NE
5. prepares body for emergencies
6. effects widespread and persistent


parasympathetic system

-originates from neurons in midbrain, pons, medulla and sacral region of spinal cord
-exit CNS via
--cranial nerves, 3, 7, 9 and 10
--sacral nerves 2-4


preganglionic fibers

-cranial nerves III, VII, and IX go to ganglia near target organs
--eyes and facial glands
-cranial nerve X and S2-4
--converge in a large autonomic plexus
--exit plexus and then to target organs
--heart, lungs, GI tract, urinary tract, sexual organs


Dual innervation

parasympathetic organs innervate same ones as sympathetic


postganglionic fibers

-usually very short
-close to, or even within, target organs
-effects or parasympathetic system is more focused and localized



-constrict pupils
-stimulate secretion of digestive glands
-secretion of hormones promoting nutrient absorption
-increase motility of digestive tract
-stimulate defecation
-contraction of urinary bladder
-constriction of respiratory passages
-reduce HR and force of contraction
-sexual arousal


parasympathetic activation

-all neurons (pre- and postganglionic) release Ach
-quickly cleaned up after release by Acetylcholinesterase
-short lived effects that are localized
-much more local, can be shut down quickly


summary of parasympathetic

-presynaptic neurons are long and secrete Ach
-postsynaptic neurons are short, produce Ach; either excitatory or inhibitory
-innervate organs in head and abdominal pelvic region
-all ganglia in or near targets


dual innervation

-most organs receive innervation from both divisions
-cranial area
--sympathetic reaches via chain ganglia
--parasympathetic reaches via cranial region
-thoracic and abdominal area
--sympathetic and parasympathetic mingle at plexuses
--examples: cardiac plexus; esophageal plexus


visceral reflexes

-simple functional units of the ANS
-provide an autonomic motor response
-common for digestive system


2 types of visceral reflexes

-long reflexes: go to the CNS for processing
-short reflexes: are processed in the autonomic ganglion
--only behavioral loop that does not involve CNS
--goes sensory-ganglia-effector


control of autonomic activity

-many control centers in medulla
-hypothalamus regulate body temperature
-limbic system and cerebral cortex control ANS when person is stressed out