Chapter 15 Flashcards
What are some functions the ANS regulates?
Heart rate, blood pressure, body temperature, respiratory airflow, pupillary diameter, digestion, energy metabolism, defecation, urination, sexual function
What does the ANS control?
Glands, smooth muscle, and cardiac muscle
Primary target organs of ANS?
Thoracic and abdominopelvic cavity viscera, cutaneous blood vessels, sweat glands, piloerector muscles
What would happen if the nerve was severed from an autonomic organ?
It would continue working, but w/ exaggerated responses - denervation hypersensitivity
What would happen if the nerve was severed from a somatic organ?
It would exhibit flaccid paralysis and be unable to function
What are visceral reflexes?
Unconscious, automatic, stereotyped responses to stimulation. A bit slower than somatic reflexes
Components of a visceral reflex arc?
Receptors (detect stretch, tissue damage, chemicals, body temp, etc) -> afferent neurons to CNS -> integrating center (interneurons) -> efferent neurons -> effector (gland or viscera)
How would a baroreflex work?
Baroreceptors sense increased BP, glossopharyngeal nerve transmits signals to medulla, vagus nerve transmits inhibitory signals to cardiac pacemaker, heart rate decreases
Divisions of ANS?
Sympathetic (fight or flight) and parasympathetic (rest and digest)
How long are pre and postganglionic fibers in sympathetic nervous system?
Short pre, long post
How long are pre and postganglionic fibers in parasympathetic nervous system?
Long pre, short post
What does the sympathetic nervous system do?
Increase heart rate, blood pressure, airflow, blood glucose levels, and pupillary dilation. Releases blood flow to skin, GI tract, and urinary output
What does the parasympathetic nervous system do?
Reduce energy expenditure, stimulate digestion, urination, defecation, glycogen synthesis. And bronchoconstriction and decreases cardiac contractions
What is autonomic tone?
Normal background rate of activity that represents the balance of the 2 systems according to the body’s needs
What is sympathetic tone?
Keeps blood vessels partially constricted and maintains blood pressure
Difference between pathways in somatic and autonomic reflex arcs?
Somatic is CNS to skeletal muscle directly, autonomic is CNS to preganglionic fiber to postganglionic fiber to target cell
What is parasympathetic tone?
Maintains smooth muscle tone in intestines
Where do sympathetic division nerve fibers arise from?
Thoracic and lumbar regions of the spinal cord
Another name for sympathetic division?
Thoracolumbar division
How do sympathetic nerves exit the spinal cord and what do they lead to?
Exit via spinal nerves T1-L2 and lead to paravertebral ganglia
What ramus is preganglionic fibers?
White
What ramus is postganglionic fibers?
Gray
How do nerve fibers leave chain?
Spinal, sympathetic, or splanchnic
How do nerve fibers exit via spinal?
Exit by way of gray ramus, return to spinal cord, travel rest of way to target organ
What are muscles and body wall effectors innervated by?
Spinal fibers
How do nerve fibers exit via sympathetic?
Via sympathetic nerves extending to heart/lungs/esophagus/thoracic blood vessels, forming carotid plexus around arteries, issuing fibers from there to effectors in the head
What are effectors in the head and thoracic cavity innervated by?
Sympathetic nerves
How do nerve fibers exit via splanchnic?
Pass through sympathetic ganglia without synapsing, continue beyond ganglia, lead to collateral ganglia, and synapse w/ postganglionics
What are effectors in the abdominopelvic cavity innervated by?
Splanchnic nerves
What is the abdominal aortic plexus?
A network of collateral ganglia wrapped around the aorta
Major collateral ganglia?
Celiac, superior mesenteric, and inferior mesenteric
What is the solar plexus?
Collective name for celiac and superior mesenteric ganglia
What is neural divergence?
When a preganglionic cell branches and synapses into multiple postganglionic cells
How many postganglionic fibers are innervated by 1 preganglionic neuron in the sympathetic division?
10-20
How many postganglionic fibers are innervated by 1 preganglionic neuron in the parasympathetic division?
5 or less
What does the adrenal cortex do?
Secrete steroid hormones
What does the adrenal medulla do?
Essentially functions as a sympathetic ganglion
What are adrenal medullas made of?
Modified postganglionic neurons without dendrites or axons
What is the sympathoadrenal system?
The sympathetic nervous system and adrenal medulla, they’re paired because they’re close in development and function
What are catecholamines?
85% epinephrine and 15% norepinephrine, w/ a trace of dopamine, secreted by the adrenal medulla. Can function as neurotransmitters
What is an intramural ganglion?
In the parasympathetic nervous system, preganglionic fibers that end in the wall of the target organ
Where are somas/origins of preganglionic neurons located?
Midbrain, pons, medulla oblongata, and S2-S4 of spinal cord
How do fibers reaching target organs differ for sympathetic and parasympathetic divisons?
In sympathetic - postganglionic fiber reaches target organ. In parasympathetic - preganglionic fiber reaches target organ before there’s a divergence
From what nerves do fibers leave the brainstem?
Oculomotor, facial, glossopharyngeal, and vagus
What does the oculomotor nerve do?
Narrow pupils and focus lenses
What does the facial nerve do?
Control tear, nasal, and salivary glands
What does the glossopharyngeal nerve do?
Parotid salivary gland
What does the vagus nerve do?
Carry 90% of parasympathetic preganglionic fibers; and control viscera as far as the proximal half of the colon
What do the remaining fibers from S2 to S4 do?
Travel by pelvic nerves to terminal ganglia in distal half of colon, rectum, urinary bladder, and reproductive organs
What is the enternic nervous system?
The digestive tract; it doesn’t arise from brainstem or spinal cord but it does innervate smooth muscle and glands so it’s debatably part of the ANS
What is the enternic nervous system made of?
100 million neurons in the walls of the digestive tract
Does the enteric nervous system have reflex arcs?
Yes, but they’re not associated w/ the spinal cord
What does the enteric nervous system do?
Regulate the motility of the esophagus, stomach, and intestines, and regulate secretion of digestive enzymes and acid
Where are paired adrenal glands?
Resting on the superior poles of the kidneys
What are the glands of 1 adrenal gland?
Outer rind, or adrenal cortex, and inner core, or adrenal medulla
How is digestion carried out?
By the enteric nervous system, but also the sympathetic and parasympathetic nervous systems
What do sympathetic preganglionic fibers secrete?
ACh
What do sympathetic postganglionic fibers secrete?
Norepinephrine mostly, sometimes ACh
What do parasympathetic preganglionic fibers secrete?
ACh
What do parasympathetic postganglionic fibers secrete?
ACh
What does cholinergic mean?
Secretes ACh
What does adrenergic mean?
Secretes norepinephrine
Can divisions of the ANS have contrasting effects on organs?
Yeah
Why do autonomic neurons have different effects?
Symp. and parasymp. fibers secrete diff neurotransmitters + target cells respond in diff ways even to the same neurotransmitter just depending on what receptors they have for it
What do autonomic nerve fibers secrete?
Acetylcholine or norepinephrine
What sympathetic postganglionics secrete ACh?
Ones innervating sweat glands and some blood vessels
What are cholinergic fibers?
Any nerve fiber that secretes ACh
What are cholinergic receptors?
Any receptor that binds ACh
Categories of cholinergic receptors?
Muscarinic and nicotinic
What are muscarinic receptors?
Type of ACh receptor; found in cardiac and smooth muscle and gland cells. Excitatory or inhibitory
What are nicotinic receptors?
Type of ACh receptor; in all ANS postganglionic neurons + adrenal medulla + neuromuscular junctions of skeletal muscle. Always excitatory
What are adrenergic fibers?
Fibers that secrete norepinephrine
What are adrenergic receptors?
Receptors that bind norepinephrine
What are alpha-adrenergic receptors?
NE receptor; usually excitatory and promoted labor contractions, stimulates piloerection, constricts dermal blood vessels, and inhibits intestinal motility
Types of norepinephrine receptors?
Alpha-adrenergic and beta-adrenergic
What are beta-adrenergic receptors?
NE receptor; usually inhibitory, relaxes and dilates bronchioles while exciting cardiac muscle - useful for exercise
What effects last longer, sympathetic or parasympathetic?
Sympathetic
How is secretion affected by blood flow?
Secretions begin as a filtrate of blood, so increasing blood flow through a gland increases secretion, and vice versa
What happens to ACh after it’s secreted?
It quickly is broken down by AChE
What happens to NE after it’s secreted?
It gets broken down by MAO or COMT, or it circulates in the bloodstream for a bit before the liver degrades it
What can sympathetic fibers secrete?
Enkephalin, substance P, neuropeptide Y, somatostatin, neurotensin, or gonadotropin-releasing hormone
What can parasympathetic fibers secrete?
Nitric oxide
What is nitric oxide necessary for?
Penile erection
What is dual innervation?
When viscera receive nerve fibers from both parasympathetic and sympathetic divisions
What is an antagonist effect?
When 2 effects oppose each other
What is a cooperative effect?
When 2 divisions act on different effectors for an overall unified effect
What is sympathetic vasomotor tone?
A state of partial constriction in blood vessels
How is blood pressure regulated?
Without dual innervation - the sympathetic fibers maintain a partial contraction so increasing firing rate constricts the vessel and vice versa
How are antagonistic effects exerted?
Dual innervation of the same effector cells, or each division innervating different effector which have opposite effects
What can influence the ANS?
Cerebral cortex, hypothalamus, midbrain, pons, and medulla oblongata
How does the cerebral cortex influence the ANS?
Powerful emotions influence the ANS because of connections between our limbic system and the hypothalamus. Like anger raises blood pressure, fear makes heart race, etc
How does the hypothalamus impact the ANS?
It’s a major visceral control center containing nuclei that control primitive functions such as hunger, thirst, and sex
How do the midbrain, pons, and medulla oblongata influence the ANS?
They contain nuclei for cardiac and vasomotor control, salivation, swallowing, sweating, bladder control, and pupillary changes
How are defecation and urination and ejaculation controlled?
Via spinal cord reflexes, but if those are severed, the autonomic reflexes then take over
What is neuropharmacology?
The study of effects of drugs on the nervous system
What do sympathomimetics do?
Enhance sympathetic activity. Stimulate receptors or increase norepinephrine release
What do sympatholytics do?
Suppress sympathetic activity. Block receptors or inhibit norepinephrine release
What do parasympathomimetics do?
Enhance activity of parasympathetic nervous system
What do parasympatholytics do?
Suppress activity of parasympathetic nervous system
How does Prozac work?
It acts like a neurotransmitter on the CNS, blocking reuptake of serotonin to prolong its mood-elevating effect
How does caffeine work?
It competes with adenosine (which, when present, causes sleepiness) by binding to its receptors
What is autonomic tone?
The balance between sympathetic and parasympathetic activity
Sympathetic fibers arise from what regions of the spinal cord?
Thoracic and lumbar
Why do parasympathetic effects last longer?
When parasymp. releases ACh, it quickly is broken down. Meanwhile, NE gets to circulate
Do all sympathetic postganglionic adrenergic fibers secrete adrenaline?
Yes
Autonomic nervous system fibers are not involved in:
Maintaining tonicity of the muscles of the neck
Preganglionic fibers of the autonomic efferent pathway are ____ and secrete _____
Myelinated, acetylcholine
Does acetylcholine always have an excitatory effect?
No
Where do fibers of the vagus nerve end?
Very near or within their target organs
Antagonistic effects of the 2 divisions of the autonomic nervous system are exemplified in the control of…
Gastrointestinal motility
If a cell as alpha 1 adrenergic receptors, it is sensitive to….
Adrenaline and norepinephrine
In response to high blood pressure, stretch receptors called ____ in the walls of arteries carrying blood to the head will trigger a reflex that causes the heart to ____ its beats per minute
Baroreceptors, decrease
