Cholinergic and Adrenergic Receptors

two major branches of the Nervous system

central nervous system (CNS) & Peripheral nervous system (PNS)

CNS

contains the brain and the spinal cord

PNS

subdivided into somatic & autonomic nervous system

autonomic nervous system

subdivided into the parasympathetic and sympathetic nervous system

cholinergic drugs

work on parasympathetic nervous system

adrenergic drugs

work on sympathetic nervous system

Three principal functions of the autonomic nervous system

regulate the heart, regulate the secretory glands (salivary, gastric, sweat, and bronchial) and regulate the smooth muscles (bronchi, blood vessels, urogenital system, gastrointestinal system)

autonomic nervous system

regulates unconscious body functions to maintain homeostasis

sympathetic nervous system structures

nerve fibers: arise from thoracic and lumbar regions of the spinal cord join at prevertebral ganglion, then from here nerve fibers exit and connect to the vital organs

sympathetic nervous system functions

dilation of pupils of the eyes and bronchioles of lungs, increases HR, BG concentration, blood to skeletal muscle

sympathetic nervous system functions

slows peristaltic action, decreases glandular secretions, blood to digestive organs, relaxes muscles of gallbladder and urinary bladder

parasympathetic structures

Nerve fibers: (preganglionic) that arise from brainstem and sacral region of the spinal cord to join the nerve fibers (postganglionic) in the muscles and glands

functions of the parasympathetic NS

constricts pupils of the eyes and bronchioles of the lungs, decreases HR, blood glucose concentration, blood to skeletal muscles

functions of the parasympathetic NS

increases peristaltic action, glandular secretions, blood to digestive organs, contracts muscles of gallbladder and urinary bladder

parasympathetic nervous system drugs

promote the digestion of food, promote the excretion of waste, promote the control of vision, promote the conservation of energy

sympathetic nervous system drugs

regulation of the cardiovascular system, maintaining blood flow to the brain, redistributing blood and compensating for the loss of blood

sympathetic nervous system drugs

regulation of temperature: blood flow to the skin, promotes sweat and erector pili. Implementation of fight or flight reaction: increasing HR and blood pressure, shunting blood away from the skin, dilating the bronchi and pupils, mobilizing stored energy

Parasympathetic nerve

slows HR

Sympathetic nerve

accelerates HR

Cholinergic receptors

mediated by acetylcholine

adrenergic receptors

mediated by epinephrine and norepinephrine

Subtypes of cholinergic receptors

Nicotinic N, Nicotinic M, Muscarinic

Subtypes of adrenergic receptors

Alpha 1, Alpha 2, Beta 1, Beta 2, Dopamine

Cholinergic Drugs

Agents that influence the activity of cholinergic receptors, most mimic or block the actions of acetylcholine

Cholinesterase Inhibitors

prevent the breakdown of acetylcholine

parasympathetic nervous system

primarily releases acetylcholine at the end of the postganglionic nerve fibers to influence effector organs by stimulating cholinergic receptors, creating the effects we expect to see in when the parasympathetic nervous system is activated

Nicotinic N receptors

located between preganglionic and postganglionic nerve fibers

Nicotinic N receptors

promote the synaptic communication between the preganglionic and postganglionic nerve fibers through the use of the neurotransmitter acetylcholine

Nicotinic M Receptors

located at neuromuscular junctions and are responsive to acetylcholine

Nicotinic M receptors

the impulse from a neuron to a muscle cell signals contraction and is responsible for muscle tone

Muscarinic Receptors

acetylcholine receptors

Muscarinic Receptors

Play several roles; including acting as the main end receptor stimulated by acetylcholine released from postganglionic fibers in the parasympathetic nervous system

M1

increase exocrine gland secretions

M2

located in heart and slow down heart rate by slowing speed of depolarization

M3

located in smooth muscles of blood vessels and lungs

M3

increase intracellular calcium and cause contraction of smooth muscle; stimulate secretion in salivary glands and stomach and excitation in GI tract

sympathetic nervous system

primarily releases norepinephrine pr epinephrine

norepinephrine and epinephrine

released at the end of the postganglionic nerve fibers to influence effector organs by stimulating adrenergic receptors, creating the effects we expect to see when the sympathetic nervous system is activated

Alpha adrenergic receptors type 1 (constrictors)

located on blood vessels. when turned on cause vasoconstriction, ejaculation and contraction of the bladder neck and prostate

Alpha adrenergic receptors type 2 (feedback inhibition)

located in the CNS, platelets, exocrine glands of the pancreas, liver. When turned on inhibit insulin and enzyme release from pancreas, inhibit gallbladder contractions

Alpha adrenergic receptors type 2 (feedback inhibition)

inhibit release of NE and can decrease hypertension crisis, produce sedation and analgesia, partially block acute withdrawal symptoms in chronic opioid users

Beta 1 adrenergic receptors

located in the heart and kidneys

Beta 1 adrenergic receptors

increases HR, including speed and strength of contraction, Increases the release of renin in the kidneys to stimulate the RAAS feedback for blood pressure regulation

Beta 2 adrenergic receptors

located in the lungs, coronary blood vessels and smooth muscle of digestive systems

Beta 2 adrenergic receptors

produces bronchodilation, dilation of the lung and heart blood vessels, decreased motility and tone of digestive system