7.2 Neurotransmitters Flashcards
Whatdo cholinergic fibers release
- acetylcholine (Ach)
- released at:
- > sympathetic preganglionic axons
- > parasympathetic pre and post ganglionic axons
- > somatic motor neurons
what do adrenergic fibers release
- norepinephrine or epinephrine
*released from most sympathetic postganglionic axons
exceptions: sympathetic postganglionic fibers secrete ACh at sweat glands & some blood vessels in skeletal muscles
what do cholinergic receptors bind? what are the types
- bicotinic and muscarinic receptors bind ACh
where are nicotinic receptors found? what is the effect of Ach binding
found on
- > Motor end plates of skeletal muscle cells
- > All ganglionic neurons (SNS & PSNS)
- > Hormone-producing cells of adrenal medulla
*effects of Ach at nicotininc receptors is always stimulatory
where are muscarinic receptors found? what is their effect when Ach binds?
- found on all effector cells stimulated by postganglionic cholinergic fibers
- effect can be inhibitory or excitatory
what are the types of adrenergic receptors?
- Alpha = Generally stimulatory
- Beta = Generally inhibitory (except heart)
(effects depend on receptor subclass of targer organ
action of epinephrine and norepinephrine at beta and alpha adrenergic receptors
NE: alpha > beta
E: Alpha = beta
what happens when NE or E binds α1
acts on: blood vessles serving skin, ucosae, abdominal viscera, kidneys, and salivary glands
*vitally all sympathetic target organs except the heart
effect of binding: contricts blood vessels and visceral organ sphincters; dilates pupils of the eyes
*think α looks like a blood vesel if errase the tail
what happens when NE or E binds α2
- binds the membrane of adrenergic axon terminals, pancrease, and blood platlets
- inhibits NE release from adrenergic terminals, inhibits insulin secretion by pancreas and promotes blood clotting
what happens when NE or E binds β1
binds to: heart predominantly but also kidneys and adipose tissue
- increases HR and strength, stimulates renin release by kidnys
*β1 = heart, β2 = lungs bc have 2 lungs
what happens when NE or E binds β2
- binds to lungs and most other sympathetic target organs
- abundant on blodo vessels serving the heart, liver and skeletal muscle
effects are mostly inhibitory: dilates BV and bronchioles, relax smooth muslce walls of digestive and urinary organs, relax uterus
*relas bronchioles to have more air going in and out
what happens when NE or E binds β3
acts on adipose tissue
0 stimulates lipolysis by fat cells
why are there interactions of the autonomic divisions
Most visceral organs have dual innervation
Dynamic antagonism allows for precise control of visceral activity
what receptors are found in dilator, sphincter, cilary muscle and cilary epithelium of the eye
dilator: alpha
Sphincter: M
cilary epithelium: Beta
cilary muscle; M
what is parasympathetic tone
PSNS normally dominates heart & smooth muscle of digestive & urinary tract organs
- >Slows heart
- > Dictates normal activity levels of digestive & urinary tracts
* SNS can override these effects during times of stress
describe sympathetic tone
aka vasomotor tone
- dont have dual innervation, BV only have 1 input
- keeps blood vessel in a continual state of partial constriction
what organs do not have dual inneration? what are they responsible for?
*these only have sympathetic inneravation
- sweat glands and arrector pili muscles: thermoregulatory response
- kidneys: release renin
- most blood vessels: reg blood presure
- adrenal medulla: metabolic effects
- inc metabolic rate of cells
- inc blood glucose
- metabolize fats as fuels
describe localized vs diffuse effects in PSNS and SNS
PSNS: short-lived, highly localized control over effectors
SNS: long-lasting, bodywide effects
what are the effects of sympathetic activation
duration of sympathetic activation
- long lasting because:
- > NE is inactivated more slowly than ACh
- > NE & E released into blood & remain there until destroyed by liver
components of visceral reflexes
same as comatic reflexes
- stimulus deteceted by sensory receptor in viscerea
- visceral sensory neuron
- integration center: amy be preganglionic neuron (as shown), doral horn interneuron, or within walls of GI tract
- efferent pathway (two neuron chain): pre and post ganglionic neuron
- visceral effector -> response
*can have short relfexe that bypasses CNS
what controls ANS functioning
Cerebral cortex (frontal lobe) limbic system (emotional input) hypothalamus (overall integration of ANS) —> Brain stem —–> spinal chord
*brain stem: reg pupil size, respiration, heart, BP, swallowing
*spina chord: reg urination, defication, erection and ejactualtion reflexes
