ANS Flashcards
ANS CONTROL CENTERS
spinal cord brain stem hypothalamus (also operates via visceral reflexes)
hypothalamus controls
water balance,feeding control, heat control
brain stem controls
urinary bladder, pneumotaxic center, cardiac accleration and vasoconstriction, cardiac slowing, respiratory center
sympathetic fibers vs parasympathetic fibers
sympathetic pre fibers are short post are long. opposite for parasympathetic
sympathetic efferent fibers originate
in spinal cord T1 to L2
preganglionic transmission options
- )Synapse directly with postganglionic fibers
- ) Follow preganglionic pathway to one of two peripheral ganglia where they synapse with postganglionic fibers
- ) Pass through the sympathetic chains then through the splanchnic nerves to the two adrenal medullae
Sympathetic fibers & the skeletal nerves
Some postganglionic fibers that originate in the sympathetic chains pass back into the spinal cord at all levels of the cord
They then extend to all parts of the body via the skeletal nerves
percentage of sympathetic fibers in skeletal nerves
8%. they control pili erector, sweat glands some blood vessels
cranial nerve 3
ciliary ganglion and ciliary muscles of eye
cranial nerve 7
pupillary sphincter, sphenopalatine ganglion, lacrimal glands, nasal glands
cranial nerve 5
submandibular ganglion, submandibular gland
cranial nerve 9
otic ganglion, parotid gland
cranial nerve 10
heart, stomach, pylorus, colon, small intestine, ileocecal valve, anal sphincter, detrusor, trigone,
sacral 1-4
only parasympathetic fibers from vertebrae. mostly come from 2 and 3
celiac ganglion organs
pylorus, adrenal medulla, kidney, ureter, intestine ileocecal valve, anal sphincter
hypogastric plexus
bladder, trigone, detrusor
organs that have no peripheral ganglion
eye, heart, bronchi
amount of molecules in transmitter vesicle
200-10000
4 different actions of alpha component
1.)pen specific ion channel through post synaptic membrane (long lasting).
2.)Activation of cyclic adenosine monophosphate (cAMP) of cyclic guanosine monophosphate (cGMP)( Can activate a variety of metabolic activities)
3.) Activation of one or more intracellular enzymes
4.) Activation of gene transcription
(Create changes in metabolic machinery or cellular structure)
all ANS preganglionic fibers release
ACH
most post ganglionic fiber of parasympathetic fiber release
ACH
most post ganglionic fiber of sympathetic fiber release
noreepinephrine (except sweat glands pili erector and some blood vessels which release ACH)
ACETYLCHOLINESTERASE is made from
acetyl coa and choline and requires acetylycholinetranferase
removal of ACH from synaptic cleft
ACETYLCHOLINESTERASE hydrolyses ACH into acetate ion and choline. choline is taken up by terminal nerve ending
production of NORE
Starts in axoplasm of terminal nerve ending [Tyrosine> Dopa] via hydroxylation [Dopa>Dopamine] via decarboxylation opa transported into vesicles for final production step
[Dopamine> Norepinephrine] via hydroxylation
In adrenal medulla …of the norepinephrine is converted to epinephrine via methylation process
80%
REMOVAL OF NORE
1.) 50% to 80% moved back into terminal nerve ending via active transport process
2.)Most of the rest diffuses away from the nerve endings into surrounding tissue
3.) Small amount destroyed by monoamine oxidase or catechol-O-methyl transferase
( Monoamine oxidase mainly in nerve endings Catechol-O-methyl transferase present in all tissues)
Norepinephrine Active Time
Normally remains active for several seconds
Norepinephrine and epinephrine released by adrenal medullae into blood remains active for 10 to 30 seconds
Level of activity takes 1 to 3 minutes to degenerate to nothing
Deactivated by the catechol-O-methyl transferase, mainly in the liver
MUSCARINIC AND NICOTINIC RECEPTORS
Muscarinic
Receptor on effector organs innervated by parasympathetic postganglionic fibers
Nicotinic
Receptor on postganglionic fibers of all autonomic fibers, Receptor on neuromuscular junction of skeletal muscle
both activated by ACH
types of adrenergic receptors
Alpha (alpha1 and alpha2)
Beta (beta1 (β1), beta2 (β2), and beta3 (β3)
Both types of receptors can produce excitatory AND inhibitory responses – Response depends EFFECTOR ORGAN
Norepinephrine secreted by adrenal medullae
Main affect on alpha receptors Much smaller effect on beta receptors
Epinephrine secreted by adrenal medullae
excites both types of receptors equally
alpha a1 receptors
vasoconstriction, iris dilation, intestinal relaxation, intestinal sphincter contraction, pilomotor contraction, bladder sphincter contraction
a2 receptor
inhibits neurotransmitter release
beta 1 receptor
cardio acceleration, increased myocardial strength, lipolysis
beta 2 receptors
vasodilation, intestinal relaxation, uterus relaxation, bronchodilation, calorigenesis, glycogenolysis, bladder wall relaxation
beta 3 receptors
thermogenesis
impulses required for normal tone
1 impulse per second. max with 10-20 per second
normal release of nore by medulla
0.05 μg/kg/minute
normal release of epi by medulla
0.2 μg/kg/minute
blood vessel sym/para
Most often constricted
Most often little or no effect
heart muscle
Increased rate Increased force contraction
Slowed rate Decreased force contraction mainly in atria
Heart coronaries
Dilated (β2); Constricted (α)
Dilated
lungs bronchi
dilated constricted
lungs blood vessels
Mild constriction
? Dilated
gut
decreased activity, increased activity
kidney
Decreased urine output Increased renin secretion
None
skeletal muscle
Increased glycogenolysis Increased strength
None
Systemic arterioles abdominal viscera
Constricted
None
Systemic arterioles muscle
Constricted (α) Dilated (β2) Dilated (cholinergic)
None
skin
constricted, none
blood coag
increased, none
blood glucose
increased, none
blood lipids
increased, none
basal metabolism
increased up to 100%, none
adrenal medullary secretion
increased, none
mental activity
increased, none
