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APHY 101 Exam 5d
Ch. 14 Autonomic Nervous System
| Question | Answer |
|---|---|
| the ANS motor neurons do what 4 things? | innvervate smooth/cardiac muscle and glands, make adjustments to ensure optimal support for body activities, operate via subconscious control, have viscera as most of their effectors (see Fig. 14.1) |
| In which 3 areas does the ANS differ from the somatic nervous system? | effectors are different, and so are the efferent pathways and target organ responses |
| contrast the effectors of the SNS and ANS? | SNS effectors are skeletal muscles while ANS effectors are cardiac muscle, smooth muscle, and glands |
| contrast the efferent pathways of the SNS and ANS? | SNS uses a heavily myelinated, single-neuron pathway to directly innervate skeletal muscle from the CNS; ANS employs a lightly myelinated, two-neuron chain (preganglionic/postganglionic) to regulate smooth/cardiac muscle and glands |
| what are the parts of the ANS two-neuron chain for efferent pathways? | preganglionic (first) neuron has a lightly myelinated axon, and the postganglionic (second) neuron is unmyelinated, extending to an effector organ |
| why does myelination matter for efferent pathways? | skeletal muscle (heavily myelinated) receives a faster innervation for rapid, excitatory control, while the lack of heavy myelination in the ANS makes for slower, often inhibitory, involuntary responses |
| what are the neurotransmitter effects in the SNS vs. the ANS? | SNS motor neurons release ACh (excitatory); in the ANS, preganglionic fibers release ACh, postganglionic fibers release NE or ACh, and whether the effect is stimulatory or inhibitory depends on the NT released AND the receptor type of the effector |
| what are the 2 divisions of the ANS? | sympathetic and parasympathetic, these counterbalance each other |
| what does the sympathetic division of the autonomic nervous system generally do? | mobilizes the body during extreme situations, "fight or flight" system |
| what does the parasympathetic division of the autonomic nervous system generally do? | performs maintenance activities and conserves body energy, concerned with keeping body energy use low |
| what are the 3 D's of activities that the parasympathetic division does? | digestion, defecation, and diuresis |
| how are some activities illustrated of the parasympathetic nervous system? | a person who relaxes after a meal will have low BP/heart rate/ respiratory rates, high GI tract activity, warm skin, constricted pupils |
| what are the 4 E's of activities that the sympathetic division does? | exercise, excitement, emergency, and embarrassment |
| how does the sympathetic division promote adjustments during exercise? | blood flow to organs is reduced, flow to muscles is increased |
| how are activities of the sympathetic nervous system illustrated? | a person who is faced with a tiger/threatened will have an increased heart rate, breathing is rapid/deep, skin is cold/sweaty, pupils dilate |
| (starred) where do sympathetic fibers originate? | thorcolumbar region of the spinal cord |
| (starred) what are the lengths of sympathetic fibers pre/post ganglionic? | short preganglionic and long postganglionic |
| (starred) where are the ganglia of sympathetic fibers? | close to the spinal cord |
| (starred) where do parasympathetic fibers originate? | brain and sacral spinal cord |
| (starred) what are the lengths of parasympathetic fibers pre/post ganglionic? | long preganglionic and short postganglionic |
| (starred) where are parasympathetic ganglia located? | in the visceral effector organs |
| what is sympathetic outflow? | nerve signals sent from the thoracic and lumbar regions of the spinal cord (the thoracolumbar division) to peripheral organs, initiating "fight-or-flight" responses |
| what is parasympathetic outflow? | nerve signals sent from the craniosacral regions of the spinal cord to peripheral organs, initiating "rest and digest" |
| (starred) how is the parasympathetic division outflow divided? | cranial outflow chart and sacral outflow chart (know your cranial nerves) |
| how does the sympathetic nervous system outflow begin? | first it arises from spinal cord segments T1 through L2, and sympathetic neurons reside in the lateral horns of the spinal cord |
| what about the fibers of sympathetic outflow? | preganglionic fibers pass through the white rami communicantes and synapse in the chain (paravertebral) ganglia; fibers from T5-L2 form splancnic nerves and synapse with collateral ganglic; postganglionic fibers innervate the numerous organs of the body |
| what is the sympathetic trunk (or chain)? | a paired, ganglionated nerve cord running vertically along the entire length of the vertebral column, from the base of the skull to the coccyx |
| what comprises the sympathetic trunk or chain? | paravertebral ganglia form part of it, and there are 23 ganglia and 3 collateral ganglia (the 23 are 3 cervial, 11 thoracic, 4 lumbar, 4 sacral, 1 coccygeal) |
| what are the 3 collateral ganglia of the sympathetic trunk? | celiac, superior mesenteric, and inferior mesenteric |
| sympathetic nervous system - what organs does the celiac collateral ganglia serve? | kidney, adrenal glands, liver, stomach |
| sympathetic nervous system - what organs does the superior mesenteric collateral ganglia serve? | small and large intestine |
| sympathetic nervous system - what organs does the inferior mesenteric collateral ganglic serve? | rectum, bladder, and genitals |
| sympathetic nervous system - what are the 3 pathways a preganglionic fiber follows upon entering the paravertebral ganglia? | 1. synapse with the postganglionic neuron within the same ganglion; 2. ascend or descend the sympathetic chain to synapse in another chain ganglion; 3. pass through the chain ganglion and emerge without synapsing into a splanchic nerve |
| what are the fibers that innervate sweat glands and arrector pili muscles? | postganglionic axons that enter the ventral rami via the gray rami communicantes (under the hierarchy of pathways with synapses in chain ganglia) |
| which nervous division are rami communicantes associated with? | sympathetic division only |
| what are the 2 major neurotransmitters of the autonomic nervous system? | acetylcholine and norepinephrine |
| which axons parts release ACh? | all preganglionic axons and all parasympathetic postganglionic axons |
| there are cholinergic fibers and adrenergenic fibers - which releaes what? | cholinergic are ACh-releasing fibers, while adrenergic fibers are sympathetic postganglion axons that release NE |
| true or false, neurotransmitter effects don't depend on receptor type | false, NT effects can be excitatory or inhibitory depending on receptor type |
| what are most visceral organs innervated by? | both sympathetic and parasympathetic fibers, resulting in dynamic antagonisms that precisely control visceral activity |
| review: sympathetic fibers increase what and inhibit what? | increase heart and respiratory rates, and inhibit digestion and elimination |
| review: parasympathetic fibers decrease what and allow for what? | decrease heart and respiratory rates, and allow for digestion and the discarding of wastes |
| what is sympathetic tone? | sympathetic tone refers to the constant, baseline activity of the sympathetic nervous system, which regulates involuntary functions like blood pressure, heart rate, and temperature, acting as the body's "accelerator" |
| what does the sympathetic division do regarding blood pressure? | controls BP and keeps the blood vessels in a continual state of partial constriction/ causes BP to rise as needed or dilate if BP is to be decreased |
| what is a treatment for hypertension (high BP)? | alpha-blocker drugs that intervere with vasomotor fibers |
| what is parasympathetic tone? | baseline activity of the parasympathetic nervous system, maintaining homeostasis by slowing the heart rate, lowering BP, and dictating normal activity of digestion/urination |
| fun fact about the SNS/PNS | the sympathetic division can override PNS effects during times of stress |
| what PNS drugs are there and what do they do? | drugs can block parasympathetic responses and increase heart rate and block fecal and urinary retention |
| fun fact about ANS cooperation | autonomic nervous system cooperation is best seen in control of the external genitalia - PNS fibers cause vasodilation and erect the penis/clitoris, SNS fibers cause ejaculation of semen in males and reflex peristalsis in females |
| uniquely, what organs' activity does the SNS regulate that are not subject to PNS influence? | activity of the adrenal medulla, sweat glands, arrector pili muscles, kidneys, and most blood vessels |
| what are some unique roles the SNS controls? | thermoregulatory responses to heat, release of renin from the kidneys, and metabolic effects |
| for your own edification, what does renin do? | renin is an enzyme produced by the juxtaglomerular (JG) cells in the kidney that acts as the primary, rate-limiting regulator of blood pressure, blood volume, and sodium balance |
| where is the main integration center of autonomic nervous system activity? | hypothalamus - subconscious cerebral input via limbic lobe connections influences hypothalamic function |
| besides the hypothalamus, where are other controls of the autonomic nervous system? | cerebral cortex, reticular formation, and spinal cord (Fig. 14.9) |
| what 4 areas do the centers of the hypothalamus control? | 1. heart activity and BP 2. body temp, water balance, endocrine activity 3. emotional stages and biological drives (rage, pleasure, hunger, thirst, sex) 4. reactions to fear and the fight-or-flight system |
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