Autonomic Nervous System, receptors Flashcards
Autonomic nervous system
Signal from Hypothalamus -> Preganglion -> ganglion -> postganglion
Ganglion
boost signal
cluster of neurons outside the CNS otherwise it is a nucleus
Preganglion: neurons before ganglion
postganglion: neurons after ganglion
Sympathetic ganglia
close to spine, far from effectors
length of preganglion «< postganglion
=> urgent communication
Parasympathetic ganglia
near effector organs, far from spine
length of preganglion»_space;> postganglion
(besides for S2 S3 S4 that are close to the reproductive organs and bladder)
Ach
Acethylcholine
secreted by cholinergic neurons -> all preganglions
all parasympathetic postganglions and some sympathetic postganglions
Receptors are nicotinic receptors (ligand gated)
on the effector organs they are muscarinic receptors (G-protein)
NE
Norepinephrine / Noradrenaline
secreted by adrenargic neurons
received by adrenargic receptor (alpha and beta)
most sympathetic postganglions
Difference sympathetic parasympathetic
Neurons in CNS
Relative length of fibers (pre/post ganglion)
ganglia location
Sympathetic : prepares for activity, secrete mainly norepinephrine
Parasympathetic: relax, secrete mainly acethylcoline
Sympathetic location
between thoracic and lumbar vertebrae
T1 -> L2
Parasympathetic location
cranio sacral : cranial nerves and sacrum (s2,s3,s5)
sacrum: reproductive organs, bladder
cranial nerves: oculomotor (eye movement, constriction pupil), facial (facial movement, salivary glands,…), vagus (organs), glossopharyngeal (tongue,pharynx)
vagus and glossopharyngeal are found on the brainstem : medulla oblongata
Aside of vagus and sacrum, synapse near organ but not on organ
Vagus nerve
Sensory and motor
left side of the neck
Originates from medula oblongato (under pons)
goes between left carotid and subclavian artery
Connected to lungs, heart, liver, stomach, spleen, kidney, colon and intestines
Celiac plexus: betwee stomach,spleen, kidney,GI tract
Esophagal plexus: stomach
pulmonary plexus: heart
Cardiovascular centers
Found in medulla oblongata
Part of the baroreflex
Controls cardiac output
Vasomotor control center : control vessels diameter, sympathetic
Cardiac control center:
cardiac accelerator -> HR & Contractility goes up -> sympathetic
cardiac deccelerator -> HR goes down -> parasympathetic
Neurotransmitters
Chemical messengers of nerve cells that travel synapses
Hormones
Chemical messengers secreted by glands (endocrine system)
Sympathetic pathway
CNS -> AP down spine
-> preganglion release ACh -> nicotinic receptor open -> Na+ & Ca2+ enter -> post ganglion activated -> release norepinephrine -> adrenargic receptors on effector organ
OR
-> adrenal glands -> release (nor)epinephrine (in this case they are then hormones and not neurotransmitters)
Adrenergic receptors and effects (effectors, pressure, exercises)
G protein coupled
bind to norepinephine and epinephrine
alpha receptors are more sensitive to norepinephrine
beta recepetors are equally sensitive
vessels: alpha 1 & 2 vasoconstriction GI tract
beta 2 vasodilation skeletal & brain
heart: alpha 1, beta 1 HR and contractility up
lungs : beta 2 bronchodilation -> oxygen up in cells
exercise : active muscles, heart and brain : alpha 1 blocked b2 up -> vasodilation
vasoconstriction elsewhere -> arterial pressure up
HR up -> arterial pressure up
venous contraction up -> systemic filling -> pressure up
=> systolic blood pressure up
diastolic blood pressure can slightly go down from vasodilation
alpha receptor
(nor)epinephrine -> vasoconstriction -> BF down
Blood system of digestive system
alpha 1 : smooth muscle contraction
alpha 2: negative feedback loop norepinephrine
beta receptor
(nor)epinephrine -> vasodilaton -> BF up skeletal muscle beta 1: positive chronotopic (HR), dromotropic (conduction velocity) & inotropic (contractility) beta 2: smooth muscle relaxation beta 3: relaxation bladder
Parasympathetic pathway
CNS -> AP down spine -> preganglion release ACh -> nicotinic receptor open -> Na + and Ca2+ enter -> postganglionic activated -> release ACh -> muscarinic receptors on effector organ
Muscarinic receptors
Bind to ACh on effector organ
M1 - 5
M2: decrease HR, contractility of atrium, conduction velocity AV node
M3: smooth muscle contraction, bronchoconstriction
Arterial Baroreceptors
nerve endings in vessels walls
blood pressure sensors from stretch of walls
a lot found on aortic arch and carotid sinus (vagus nerve pass along both, glossopharyngeal is also nearby)
pressure up (stretch up) -> frequency nerve impulse up -> vagus (& glossopharyngeal) -> cardiovascular centers -> inhibit sympathetic & stimulate parasympathetic -> vasomotor down -> vasoconstriction down
pressure down (stretch down) -> frequency nerve impulse down -> vagus (& glossopharyngeal) -> cardiovascular centers -> stimulate sympathetic & inhibit parasympathetic
-> cardiac accelerator up cardiac deccelerator down -> HR, contractility up -> CO up
AND
-> vasomotor up -> vasoconstriction up -> peripheral arterial resistance up -> venous return up -> preload up -> CO up
=> BP back to normal
Cardiopulmonary baroreceptors
blood volume sensors
found in pulmonary arteries, right atrium and right ventricle
volume up -> frequency signal up -> vagus nerve -> cardiovascular center -> HR up -> CO up blood up -> kidneys -> water and sodium up -> blood volume down -> brainbridge reflex
Vasovagal collapse/syncope
BF brain down (often caused by low BP) -> faint
Cause : Parasympathetic activation -> vagus nerve discharge 20 mmHg or/and HR drop > 20 bpm
lying/sitting -> standing up - > delay constriction (vessels constrict to not pool in legs) -> too much blood in legs - > CO down
Carotid sinus hypersensitivity
pressure on neck induce reflex from carotid bodies
