Lesson 19 Flashcards
somatic nervous system (3)
- operates under conscious control
- controls skeletal muscles
- seldom affect long term survival
autonomic nervous system (4)
- visceral motor system
- operates without conscious instructions
- controls things like cardiac/smooth muscles, glands, adipocytes
- coordinates organ systems
primary target organs of the autonomic nervous system (2)
- viscera of the thoracic and abdominal cavities
- structures of the body wall like cutaneous blood vessels, sweat glands, arrector muscles
what happens when you sever the ANS nerves to organs?
it results in an exaggerated response; denervation hypersensitivity
visceral reflexes
unconscious, automatic, stereotyped responses to stimulation involving visceral receptors and effectors that is controlled by the autonomic nervous system
visceral reflex arc
- receptors
- afferent neuron
- integrating center
- efferent neurons
- effectors
sympathetic division of the ANS
prepares body for physical activity like exercise, trauma, arousal, etc.; fight or flight
parasympathetic division of the ANS
calms many body functions, reducing energy expenditure and assists in bodily maintenance; resting and digesting state
autonomic tone
normal background rate of activity that represents balance of the two systems according to the body’s needs
the ANS has components in both the central and peripheral nervous system (3)
- control nuclei in the hypothalamus and other brainstem regions
- motor neurons can be located in the spinal cord and peripheral ganglia
- nerve fibers that travel through
in a somatic pathway…
a neuron does what?
a motor neuron from the brainstem or spinal cord issues a myelinated axon that reaches all the way to skeletal muscle
in an autonomic pathway…
where must a signal travel?
a signal must travel across two neurons to get to the target organ, and cross a synapse where these two neurons meet in an autonomic ganglion
preganglionic fiber
cell body in the brainstem or spinal cord; its axon that extends to the autonomic ganglion
what is the neurotransmitter of the presynaptic neuron? (preganglionic fiber)
ACh; acetylcholine
what is the neurotransmitter of the postsynaptic neuron? (postganglionic fiber)
ACh or NE; acetylcholine or norepinephrine
anatomy of the sympathetic division (2)
- pathways arise from thoracic and lumbar regions of the spinal cord; aka the thoracolumbar division
- relatively short preganglionic and long postganglionic fibers
sympathetic division general pathway (4)
- cell bodies of preganglionic neurons in lateral horns and nearby regions of spinal grey matter; fibers exit the cord via spinal nerves T1 to L2
- lead to nearby sympathetic chain of ganglia
- usually 3 cervical, 11 thoracic, 4 lumbar, and 4 sacral, and 1 coccygeal
- sympathetic fibers are in every level of the body
paravertebral ganglia
a series of longitudinal ganglia adjacent to both sides of the vertebral column from cervical to coccygeal levels
where are preganglionic neurons located in the sympathetic division?
T1 to L2 of the spinal cord
where are the cell bodies of the preganglionic neurons located?
the lateral gray horns of the spinal cord
axons leave the _____ _____ and enter the _____ _____ of segments before terminating on _____ neurons
spinal cord, central roots, ganglionic
Typically, the axon of the _____ neuron is short and the axon of the _____ neuron is long
preganglionic, postganglionic
seven responses to increased sympathetic activity
- heightened mental alertness
- increased metabolic rate
- reduced digestive and urinary function
- energy reserves activated
- increased respiratory rate and respiratory passageway dilate
- increased heart rate and blood pressure
- sweat glands activated
the ganglionic neurons in the sympathetic division are located in three possible areas:
- sympathetic chain ganglia
- collateral ganglia
- adrenal medullae
sympathetic chain ganglia (2)
- on both sides of the vertebral column
- control effectors in the body wall, thoracic cavity, head, and limbs
collateral ganglia (3)
- anterior to vertebral bodies
- contain ganglionic neurons that innervate tissues and organs in the abdominopelvic cavity
- preganglionic axons that synapse here are from the motor neurons in the CNS
adrenal medullae (3)
- very short axons (are endocrine cells); innervated by axons from the CNS that travel through the sympathetic chain and collateral ganglia
- when stimulated, release neurotransmitters into BLOODSTREAM (ACh and NE)
- function as hormones to affect target cells throughout body
adrenal (suprarenal) glands
paired glands located on superior poles of kidneys; each is two glands with different functions
adrenal cortex
outer later, secretes steroid hormones
adrenal medulla
of the adrenal glands
inner core; essentially a sympathetic ganglion
stimulation of sympathetic preganglionic neurons (2)
- release ACh at synapses with ganglionic neurons
- always excitatory on ganglionic neurons
stimulation of sympathetic ganglionic neurons
does what?
release neurotransmitters from the postganglionic axons at specific target organs; mostly NE but some release ACh
ganglionic neurons - axon terminals (2)
- from branching networks of telodendria instead of synaptic terminals
- telodendria form sympathetic varicosities (resemble pearls)
varicosities mostly release what neurotransmitter?
norepinephrine; adrenergic neuron
- some release ACh and are cholinergic
where are ganglionic cholinergic neurons located? (4)
body wall, skin, brain, and skeletal muscle
sympathetic activation
activates the entire sympathetic division during a crisis
how does sympathetic activation change activities of tissues? (4)
- distributes NE at peripheral synapses
- targets specific effectors
- distributing E and NE throughout body in bloodstream
- also alterns CNS activity
what is sympathetic activation controlled by?
centers in the hypothalamus
stimulating what causes increased alertness during sympathetic activation?
reticular activating system
stimulating what areas causes changes in breathing during sympathetic activation?
pons and medulla
in the parasympathetic pathways, the preganglionic fibers are _____ and the postganglionic are _____
long, short
preganglionic fibers in the parasympathetic pathways travel through cranial or sacral nerves, and end in ______ _____ in or near the target
terminal ganglia
what cranial nerves control visceral structures in the head? (3)
III - oculomotor
VII - facial
IX - glossopharyngeal
parasympathetic preganglionic fibers leave the brain as part of these cranial nerves (4)
III - oculomotor
VII - facial
IX - glossopharyngeal
X - vagus (75% of parasympathetic outflow)
parasympathetic preganglionic fibers leave the spinal cord as _____ nerves
pelvic
the _____ nerve innervates structures in the neck, thoracic and abdominopelvic cavities
vagus
all neuromuscular and neuroglandular junctions release what as a neurotransmitter?
acetylcholine
five responses to increased parasympathetic activity
- decreased metabolic rate
- decreased heart rate and blood pressure
- increased secretion by salivary and digestive glands
- increased motility (movement of material in the digestive tract) and blood flow in the digestive tract
- urinary and defecation stimulation
enteric plexus
the nervous network of the digestive tract
- aka enteric nervous system
where does the enteric nervous system arise from?
not the brainstem or spinal cord lol idk
what does the enteric nervous system innervate? (2)
- smooth muscle
- glands
what does the enteric nervous system regulate?
- esophagus
- stomach
- intestines
- secretion of digestive enzymes and acids
acetylcholine (ACh)
secreted by all preganglionic neurons in both divisions and by postganglionic parasympathetic neurons
cholinergic neurons
neurons that secrete ACh
cholinergic receptor
any receptor that binds ACh
muscarinic receptors
found on cardiac muscle, smooth muscle, and gland cells with cholinergic innervation
nicotinic receptors
found on postganglionic neuron cell bodies in autonomic ganglia; on cells of adrenal medulla; and neuromuscular junction of skeletal muscle fibers
nicotine (2)
- binds to nicotine receptors in sympathetic and parasympathetic ganglion cells
- targets autonomic ganglia and skeletal neuromuscular junctions
signs and symptoms of nicotine poisoning (7)
- vomiting
- diarrhea
- high blood pressure
- rapid heart rate
- sweating
- profuse salivation
- convulsions
muscarine
toxin produced from some poisonous mushrooms
what does muscarine target?
parasympathetic neuromuscular or neuroglandular junctions
signs and symptoms of muscarine poisoning (7)
- salivation
- nausea
- vomiting
- diarrhea
- constriction of respiratory passages
- low blood pressure
- slow heart rate
norepinephrine
secreted by nearly all sympathetic postganglionic neurons
adrenergic fibers
nerve fibers that secrete NE
adrenergic receptors
receptors for NE
alpha-adrenergic receptors (2)
- usually excitatory
- two subclasses use different second messengers
beta-adrenergic receptors
- usually inhibitory
- two subclasses with different effects, but both act through cAMP as a second messenger
alpha-1 adrenergic messenger (3)
more common type
- releases intracellular calcium ions from reserves in ER
- has excitatory effect on target cells ie. causes constriction of smooth muscle blood vessels at digestive and urinary tract
alpha-2 adrenergic messenger (3)
- lowers cAMP levels in cytoplasm
- has inhibitory effect on the cell
- helps coordinate sympathetic and parasympathetic activities
beta receptors (4)
- affect membranes in many organs (skeletal muscle, lungs, heart, liver)
- triggers metabolic changes in target cells
- stimulation increase intracellular cAMP levels
- binding of NE/E causes opposite effect on cAMP compares to alpha-2 receptors
three main types of beta receptors
beta-1, beta-2, and beta-3
beta-1 receptors (2)
- increases metabolic activity
- increase activity of skeletal and cardiac muscle
beta-2 receptors
- triggers relaxation of smooth muscles along respiratory tract
- increases diameter of air passages
beta-3 receptors (2)
- leads to lipolysis, the breakdown of triglycerides in adipocytes
- releases nutrients into bloodstream
cholinergic sympathetic terminals (2)
- innervates sweat glands of skin and blood vessels of skeletal muscles and brain
- stimulate sweat gland secretion and dilate blood vessels to skeletal muscles and brain
autonomic effects on glandular secretions (2)
- increased blood flow, increased secretion
- decreased blood flow, decreased secretion
sympathetic effects tend to last longer than parasympathetic effects (2)
NE breakdown vs. ACh breakdown
- NE released by sympathetic fibers can be reabsorbed by axon terminal, diffuse to adjacent tissues, or pass into bloodstream
- ACh from parasympathetic fibers broke down quickly at the synapse
some ANS fibers release other neurotransmitters in addition to ACh or NE
enkephalin, substance P, neuropeptide Y, somatostatin, neurotensin, etc.
dual innervation
most viscera receive nerve fibers from both parasympathetic and sympathetic divisions
antagonistic effects (3)
oppose each other
- can be exerted through dual innervation of same effector cells
- can be exerted because each division innervates different cells
cooperative effects (2)
two divisions act on different effectors to produce a unified overall effect
- even when both divisions innervate a single organ, innervation is not always equal or exert equal influence
dual innervation _____ always necessary for ANS to produce opposite effects in an organ
NOT
what receptors receive only sympathetic fibers (4)
- adrenal medulla
- arrector muscles
- sweat glands
- many blood vessels
vasomotor tone
vessels in a continual state of partial constriction
blood vessels and sweat glands are _____ dual innervated
not, only innervated by the sympathetic division
cerebral cortex and limbic system - ANS
emotions influence the ANS because of the connections between our limbic system and they hypothalamus
hypothalamus - ANS
contains nuclei for primitive functions; hunger, thirst, sex
midbrain, pons, and medulla oblongata - ANS
contain nuclei for cardiac and vasomotor control, salivation, swallowing, sweating, bladder control, and pupillary changes
spinal cord - ANS
reflexes for defecation and micturition
neuropharmacology
study of effects of drugs on the nervous system
sympathomimetics (3)
enhance sympathetic activity
- stimulate receptors or increase norepinephrine
- cold medicines that dilate the bronchioles or constrict nasal blood vessels
sympatholytics suppress sympathetic activity (2)
- block receptors or inhibit norepinephrine
- beta blockers reduce high BP interfering with the effects of epinephrine and norepinephrine on heart and blood vessels
parasympathomimetics
enhance parasympathetic effects
parasympatholytics
suppress parasympathetic effects
Prozac
SSRI, blocks reuptake of serotonin to prolong its mood-elevating effect
MAO inhibitors
block enzyme monoamine oxidase to slow the breakdown of monoamine neurotransmitters
- aids in treating depression
caffeine
competes with adenosine (the presence of which causes sleepiness) by binding to its receptors
