BIO 201: Autonomic Nervous System (ANS) Study Guide

parasympathetic division

-(craniosacral division) of ANS -"rest and digest" -calms many body functions; assists in bodily maintenance -digestion & waste elimination

sympathetic division

-(thorocolumbar division) of ANS -"fight or flight" -prepares body for physical activity *increases heart rate, BP, airflow, blood glucose levels, etc.

catecholamines

-85% epinephrine -15% norepinephrine

enteric NS

-NS of the digestive system -composed of 100 million neurons found in the walls of the GI tracts *NO components in CNS! -has its own reflex arcs -regulates motility of esophagus, stomach, & intestines -regulates secretion of digestive enzymes & acid -normal digestive function also requires regulation by sympathetic & parasympathetic systems

organs without dual innervation

-adrenal medulla -arrector pili muscles -sweat glands in skin -most blood vessels

visceral motor system

-another name for autonomic nervous system -bc ANS actions are automatic

spinal cord

-central control of autonomic function -defecation & micturition reflexes -control over skeletal muscle sphincters; if this area is damaged the smooth muscle of bowl & bladder is controlled by autonomic reflexes

cerebral cortex

-central control of autonomic function -influenced by emotions

hypothalamus

-central control of autonomic function -major visceral control center *hunger, thirst, sexuality, thermoregulation *fight or flight responses originate here

brainstem

-central control of autonomic function -nuclei for cardiac & vasomotor control, salivation, swallowing, sweating, bladder control, and pupillary changes

nicotinic receptors

-cholinergic -occur on all ANS postganglionic neurons, adrenal medulla, on skeletal muscle -EXCITATORY when ACh binding occurs

muscarinic receptors

-cholinergic -occur on all glands, smooth muscle & cardiac muscle that receives cholinergic innervation -either excitatory OR inhibitory when ACh binding occurs

anatomy of parasympathetic NS: pathways of preganglionic fibers

-cranial nerves III VII, IX, & X *cardiac, pulmonary esophageal, abdominal aortic plexus -arising from sacral spinal chord *pelvic splanchnic nerves & inferior hypogastric plexus

neuronal divergence

-each PREganglionic cell branches and synapses ON multiple POSTganglionic cells -there are ~ 17 POSTganglionic neurons for every preganglionic neuron in the sympathetic NS -have relatively widespread effects on multiple organs

spinal nerve route

-effectors in body wall are innervated by sympathetic fibers that exit a ganglion by the gray ramus and travel through spinal nerves -sweat glands, piloerector muscles, blood vessels of skin & skeletal muscles

sympathetic nerve route

-effectors in head and thoracic cavity are innervated by fibers in specific sympathetic nerves that form a CAROTID PLEXUS -sweat, salivary, nasal glands; blood vessels, heart, iris

parasympathomimetics

-enhance parasympathetic activity *pilocarpine - treats glaucoma by reducing pressure in the eye

sympathomimetics

-enhance sympathetic activity -stimulate receptors or increase norepinephrine release -ephedrine

ANS controls

-glands -cardiac muscle -smooth muscles

parasympatholytics

-inhibit ACh release or block its receptors - -atropine to dilate eyes for eye exams

sympathetic tone

-keeps most blood vessels partially constricted -maintains blood pressure -loss of XXX can cause a rapid drop in BP causing a person to go into shock

adrenal medulla

-modified sympathetic ganglion that secretes neurotransmitters (in the form of hormones) into blood rather than onto other neurons -complementary involvement in mass activation that occurs during fight or flight reaction

parasympathetic cranial nerves

-oculomotor nerve (III) *narrows pupil and focuses lens -facial nerve (VII) *tear, nasal, and salivary glands -glossopharyngeal nerve (IX) *parotid salivary gland -vagus nerve (X) *viscera as far as proximal half of colon

antagonistic effects

-oppose each other -exerted through dual innervation of same effector cells *heart slowed down or sped up -exerted bc each division innervates different cells *pupillary dilator muscle & constrictor pupillae change pupil size

anatomy of sympathetic NS

-origin of presynaptic neurons: *lateral horns of gray matter of thoracic to lumbar cord *fibers exit via spinal nerves T1-L2 leading to sympathetic chain ganglia

adrenal glands

-paired glands -sit on superior pole of each kidney

sympathetic chain ganglia

-paravertebral ganglia -on average 3 cervical, 11 thoracic, 4 lumbar, 4 sacral, & 1 coccygeal ganglia -2 branches called white & gray communicating rami suspend ganglia from spinal nerve

anatomy of parasympathetic NS: origin of preganglionic fibers

-pons & medulla oblongata (cranial nerve nuclei) -spinal cord segments S2-S4

clinical depression treatment

-raise seratonin levels: *SSRI =selective seratonin reuptake inhibitor (i.e. prozac) *MAO inhibitors = interfere w/ the breakdown of monoamine neurotransmitters by blocking the action of monoamine oxidase (MAO)

cholinergic fibers

-secrete ACh -ACh binds to 2 classes of receptors: *nicotinic receptors *muscarinic receptors

adrenergic fibers

-secrete NE (norepinephrine) -only postganglionic sympathetic fibers

cooperative effects

-seen when 2 divisions act on different effectors to produce a UNIFIED effect (salivation) -parasympathetic NS increases salivary serous cell secretion -sympathetic NS increases salivary mucous cell secretion

postsynaptic neuron

-spans the distance from CNS to effectors -cell body in peripheral ganglion

presynaptic neuron

-spans the distance from CNS to effectors -cell body located in CNS -brain or spinal chord

sympatholytics

-suppress sympathetic activity -inhibit norepinephrine release or block receptors -beta-blockers that reduce blood pressure

autonomic tone

-the normal rate of activity that represents the balance of the 2 systems -this balance shifts depending on the needs of the body

small myelinated preganglionic fiber

-travel from spinal nerve to the WHITE COMMUNICATING RAMUS, then enter ganglia *some synapse immediately w/ a postganglionic fiber *some travel to higher or lower ganglia & synapse *some pass through chain w/o synapsing to reach collateral ganglia via splanchnic nerves

ANS regulates

-unconscious processes that maintain homeostasis *BP, body temp, respiratory airflow *receptors detect internal stimuli (stretch, etc)

visceral reflexes steps

1) receptors -detect internal stimuli (stretch, blood chemicals, etc) 2) afferent neurons -transmit sensory signals to interneurons in the CNS 3) efferent neurons -carry motor signals to effectors -ANS is the efferent neurons of these reflex arcs 4) effectors -glands, smooth or cardiac muscles -ANS modifies effector activity, rather than causing it

biofeedback

conscious control of the ANS

neuronal convergence

each POSTganglionic cell may receive signals FROM multiple PREganglionic cells

splanchnic (viscera)l nerve route

effectors in abdominal cavity are innervated by sympathetic fibers in splanchnic nerves that lead to 3 major COLLATERAL GANGLIA

unmyelinated postganglionic fibers

leave ganglia via GRAY COMMUNICATING RAMUS

splanchnic nerves

nerves that supply signals and information to and from the visceral organs and blood vessels

adrenal cortex

secretes steroid hormones (androgens, cortisol, etc)

anatomy of parasympathetic NS

terminal ganglia in target organs due to normally short postganglionic fibers

visceral reflexes

unconscious responses to stimulation of glands, cardiac, or smooth muscle