Exam 4 - Lecture 33, Intro to ANS

Main control centers for conscious thought and all body activities Brain: located in cranial cavity Spinal Cord: located in vertebral cavity

connects CNS with organs and glands 12 pairs of cranial nerves 31 pairs of spinal nerves

Parasympathetic stimulation Caused by activation of M3-R leads to constriction of the circular muscle Acetylcholine, opiates and opioids cause

Sympathatic stimulation Caused by activation of a1-R leads to constriction of radial muscle Adrenaline, Anticholinergics, Cocaine, Amphetamine, Hallucinogens cause

Sensory (afferent) nerves and motor (efferent) nerves

Somatic NS for voluntary contraction of skeletal muscles Autonomic NS regulate involuntary control of smooth, cardiac muscles and glands

Sympathetic and parasympathetic Sympathetic stimulates tissues Parasympathetic inhibit tissues

CNS (Preganglionic neuron, almost always ACh, released onto nicotinic receptors) Peripheral ganglion (Postganglionic neuron, AChi, NE released onto M/a,b receptors…onto target cell)

Typically monosynaptic, ACh to N1 receptors Heavily myelinated axon Effect: Stimulatory Effector organs: Skeletal muscle

Preganglionic neuron releases ACh onto N2-Rs Lightly myelinated Most neurons release NE onto adrenergic GPCRs (alpha and beta)

Preganglionic neuron release ACh onto N2-Rs Lightly myelinated Most neurons release ACh onto muscarinic GPCRs (M1 - M5)

with endocrine system, regulates activity of most internal organs by innervating smooth muscle, cardiac muscle and glands Independent of thought

controls involuntary or reflex activities Typically 2 neuron chain, Preganglionic neurons originate in brain or spinal cord, postganglionic neurons originate in ganglion located outside the CNS

Preganglionic fibers are long Postganglionic fibers are short Fibers originate in brain stem (cranial) or Sacral Ganglia are within or near visceral effector organs

Preganglionic fibers are short Postganglionic fibers are long Fibers originate in thoracic and lumbar spinal cord Ganglia are close to spinal cord

Generally stimulates the effector organ Can be activated in emergencies, fight or flight reaction

Preganglionic fibers produce ACh (cholinergic fiber), and Postganglionic produce NE (adrenergic fiber) Short pre-, long post-ganglionic fibers

Most pre- and post-ganglionic fibers produce ACh (cholinergic) Long pre-, short post-ganglionic fibers

• tyrosine enters via Na+ dependent carrier • tyrosine converted to dopamine • Dopamine and related amines enter vesicles via VMAT • Dopamine converted to NE by DBH • Vesicles with NE (and other signaling molecules) released into synaptic cleft • NE activated postsynaptic adrenoreceptors • NE diffuses away and is taken back up into presynaptic neuron by NET

Alpha-1 receptors (Gaq coupled) Alpha-2 receptors (Gai coupled

Gaq coupled Mediate fight or flight response cause constriction of blood vessels (control BP) inhibit motility in gut by contracting sphincter muscles and relaxing non-sphincter tissue Mobilize energy by breaking down liver glycogen to glucose

Gai coupled Presynaptic, provide feedback control for neurotransmitter release (decrease Ca2+ influx to decrease release of transmitter)

Beta-1 receptors (Gas coupled) Beta-2 receptors (Gas coupled0

Cardiac, inotropic, chronotropic Smooth muscle relaxation in the gut