Originates from the thoracic and lumbar regions of the spinal cord (thoracolumbar outflow)
Preganglionic neurons exit the spinal cord and synapse with postganglionic neurons in ganglia located near the spinalcord (paravertebral ganglia) or close to the target organ (prevertebral ganglia)
Sympathetic Nervous System (SNS)
Associated with the "fight or flight" response
Increases heart rate, dilates airways, redirects blood flow to muscles, and stimulates the release of glucose for energy
Parasympathetic Nervous System (PNS)
Originates from the brainstem and the sacral region of the spinal cord (craniosacral outflow)
Preganglionic neurons exit the brainstem or sacral spinal cord and synapse with postganglionic neurons in ganglia located near or within the target organs
Parasympathetic Nervous System (PNS)
Associated with the "rest and digest" response
Conserves energy by slowing heart rate, stimulating digestion, and promoting relaxation
Functions of the Autonomic Nervous System (ANS)
Maintenance of homeostasis
Contraction and relaxation of smooth muscle
All exocrine and some endocrine secretions
Heart rate and contraction
Metabolism (in the liver and skeletal muscle)
Sympathetic Nervous System (SNS)
Responsible for the "fight or flight" response, which prepares the body for action in response to stress or danger
Factors that activate the Sympathetic Nervous System (SNS)
Environmental changes
Emotional stress and anxiety
Exercise
Dehydration
Some disease states
Parasympathetic Nervous System (PNS)
The "rest and digest" system, which helps conserve energy and promotes relaxation
Acetylcholine (ACh)
Neurotransmitter for both the Sympathetic Nervous System (SNS) and Parasympathetic Nervous System (PNS)
Muscarinic Receptors
ACh binds to muscarinic receptors, which are G protein-coupled receptors
Activation of muscarinic receptors can lead to changes in ion flow across the cell membrane, modulation of enzyme activity, and changes in gene expression
Nicotinic Receptors
ACh binds to nicotinic receptors, which are ligand-gated ion channels
Activation of nicotinic receptors leads to the influx of ions, such as sodium and potassium, which can depolarize the cell membrane and trigger an action potential
Adrenergic Receptors
Norepinephrine (NE) and Epinephrine (E) bind to adrenergic receptors, which are G protein-coupled receptors
Activation of adrenergic receptors can lead to changes in intracellular signaling pathways, resulting in various physiological responses, such as smooth muscle contraction, glycogenolysis, and changes in heart rate
Physiological responses associated with Sympathetic Nervous System (SNS) activation
Increased heart rate and contractility
Pupil dilation
Relaxation of eye ciliary muscles
Decreased salivary gland secretion
Bronchodilation
Inhibition of gastrointestinal motility and secretion
Inhibition of bladder contraction
Increased speed of skeletal muscle contraction, increased muscle mass, and glycogenolysis
Physiological responses associated with Parasympathetic Nervous System (PNS) activation
Decreased heart rate, automaticity, and contractility
Pupil constriction
Accommodation of the eye lens
Increased salivary gland secretion
Bronchoconstriction
Enhanced digestion and absorption of nutrients
Increased bladder emptying
Adrenergic Agonists (Sympathomimetics)
Drugs that mimic the effects of norepinephrine and epinephrine by activating adrenergic receptors (α and β receptors)
Adrenergic Agonists (Sympathomimetics)
Epinephrine
Dobutamine
Albuterol
Adrenergic Antagonists (Sympatholytics)
Drugs that block the effects of norepinephrine and epinephrine by binding to adrenergic receptors
Adrenergic Antagonists (Sympatholytics)
Propranolol
Prazosin
Muscarinic Agonists (Cholinergic Agonists)
Drugs that mimic the effects of acetylcholine by activating cholinergic receptors (muscarinic and nicotinic receptors)
Muscarinic Agonists (Cholinergic Agonists)
Bethanechol
Pilocarpine
Muscarinic Antagonists (Anticholinergic Agents)
Drugs that block the effects of acetylcholine by binding to cholinergic receptors
Muscarinic Antagonists (Anticholinergic Agents)
Atropine
Scopolamine
Ganglionic Blockers
Drugs that block transmission in autonomic ganglia, leading to widespread autonomic effects