Physiology of the Autonomic Nervous System Flashcards
Reflex arc
Common in pain sensory Within the spinal cord, the afferent sensory fiber synapses on the motor neuron that innervates the muscles in the arm that is being burnt
Autonomic reflex arc- where are autonomic responses processed
In the hypothalamus usually, instead of the spinal cord alpha-motor neurons are typically the efferent fiber involved
Big difference between autonomic reflex arc and somatic motor system arcs
Autonomic nervous system has two neurons between the CNS and the target organ
The pre-synaptic neuron- cell body is in the CNS, terminates in a ganglion in the periphery
The post synaptic neurons cell body is in the ganglion and terminates on the target organ
What neurotransmitter is used by autonomic pre-ganglionic neurons
Preganglionic axon releases Ach
Length of pre-ganglionic and post ganglionic axons in parasympathetic vs sympathetic
Parasympathetic preganglionic axons are long, while sympathetic are short Parasympathetic post-ganglionic axons are short, while sympathetic are long
Varicosities in the second synapse of the autonomic nervous system
Varicosities contain all the components of the pre-synaptic terminal (vesicles, mitochondria etc…) and work exactly the same way as the pre synaptic terminal of the NMJ The post synaptic side is somewhat different- the ligand gated receptors are not concentrated opposite the pre synaptic terminal, they are more spread out
M1R-M5R muscarinic cholinergic receptors
M1R- found in CNS, not autonomic, role in memory Increase secretion of salivary glands and acid secreting cells of stomach
M2R- cardiac receptor, slows heart rate
M3R- smooth muscle cell contraction and exocrine gland secretion
M4R- role uncertain
M5R- found in CNS, role is uncertain
What type of receptors are found on target tissue cell in parasympathetic system
Muscarinic cholinergic
Neurotransmitter released on target tissue in parasympathetic vs sympathetic
Parasympathetic use acetylcholine to bind to muscarinic cholinergic receptors Sympathetic use Norepinephrine to bind to adrenergic receptors
Alpha-1 adrenergic receptors function and location
Lead to increased calcium intracellularly
Located on: Smooth muscle of blood vessels- contraction
Smooth muscle of urinary and reproductive tracts
Liver- gluconeogenesis/glycogenolysis
Adipose tissue- lipolysis
Lacrimal glands- reduce watery secretion
Radial muscle of iris- contraction leads to dilation of pupil
Alpha-2 adrenergic receptors function and location
Lead to decrease adenylate cyclase/cAMP
Located on:
GI sphincters- contraction
Pancreas- increase glucagon, decrease insulin
Smooth muscle of blood vessels- dilation
Platelets- increase clotting
Beta-1 adrenergic receptors function, location
Lead to increased adenylate cyclase/cAMP production
Located on:
Cardiac tissue- increase heart rate at
SA node and increase strength of contraction in ventricular muscle
Salivary glands- viscous secretion
Adipose tissue- lipolysis
Beta-2 adrenergic receptors function, location
Lead to increased adenylate cyclase/cAMP
Located on:
Bronchiole smooth muscle- relaxation
GI smooth muscle- relaxation
Vascular smooth muscle- relaxation
Liver- glycogenolysis
Eye- relax ciliary muscle, flattens lens
Beta-3 adrenergic receptors function, location
Lead to increase adenylate cyclase/cAMP
Location:
White adipose tissue- lipolysis
Brown adipose tissue- heat production
Chromaffin cells
The adrenal medulla contains chromaffin cells that make and release epinephrine as part of the sympathetic response
