ANS Overview Exam 2

from Ahangari ANS notes (flashcards generated by copilot) for Exam 2 (PCB3703C)

Autonomic Nervous System (ANS)

Controls visceral organs, glands, and blood vessels; divided into sympathetic and parasympathetic systems.

Sympathetic Nervous System Function

Fight or flight; increases HR, BP, pupil dilation, bronchodilation, sweat gland activity.

Parasympathetic Nervous System Function

Rest and digest; decreases HR, increases GI motility and gland secretion, pupil constriction.

Sympathetic Outflow

Thoracolumbar (T1–L2/3).

Parasympathetic Outflow

Craniosacral (CN III, VII, IX, X + S2–S4).

Preganglionic Neurotransmitter

Acetylcholine (ACh).

Sympathetic Postganglionic Neurotransmitter

Norepinephrine (NE).

Parasympathetic Postganglionic Neurotransmitter

Acetylcholine (ACh).

Adrenal Medulla Function

Releases epinephrine (80%) and norepinephrine (20%) into circulation.

Pheochromocytoma

Tumor of adrenal medulla causing excess catecholamine secretion and increased VMA.

α1 Receptor

Causes contraction (vasoconstriction); uses IP3/Ca²⁺ pathway.

α2 Receptor

Inhibitory; decreases cAMP.

β1 Receptor

Increases HR, conduction velocity, and contractility.

β2 Receptor

Causes relaxation (bronchodilation, vasodilation).

Propranolol

β1 blocker; decreases HR and contractility.

Albuterol

β2 agonist; bronchodilation for asthma.

Nicotinic Receptors

Found in autonomic ganglia, adrenal medulla, NM junction; excitatory.

Muscarinic Receptors

Heart inhibition (↓ HR), smooth muscle/gland excitation; blocked by atropine.

Medulla Autonomic Centers

Vasomotor, respiratory, swallowing, coughing, vomiting.

Pons Autonomic Center

Pneumotaxic (respiratory) center.

Midbrain Autonomic Center

Micturition center.

Hypothalamus Functions

Temperature regulation, endocrine control, sleep, thirst, food intake, emotions.

Sympathetic Effect on Bronchi

β2 → bronchodilation.

Parasympathetic Effect on GI Tract

Increased peristalsis, secretion; sphincter relaxation.

Sympathetic Effect on Bladder

Sphincter contraction; detrusor relaxation.

Parasympathetic Effect on Bladder

Sphincter relaxation; detrusor contraction.

Parasympathetic Effect on Genitals

Erection (vasodilation).

Sympathetic Effect on Genitals

Ejaculation (emission).

Mechanoreceptors

Respond to mechanical stimuli (pressure, stretch, vibration).

Photoreceptors

Respond to light (rods and cones).

Chemoreceptors

Detect chemicals (taste, smell, osmoreceptors).

Nociceptors

Detect pain and extreme temperatures.

A-alpha Fibers

Fastest; motor.

A-delta Fibers

Fast pain and temperature.

C Fibers

Slow pain; slowest conduction.

Receptor Potential

Change in membrane potential caused by a stimulus.

Slowly Adapting Receptors

Tonic; respond throughout stimulus (muscle spindle, pressure).

Rapidly Adapting Receptors

Phasic; respond at onset (Pacinian corpuscles, light touch).

First-Order Neurons

Located in dorsal root ganglia; bring info to CNS.

Second-Order Neurons

Located in spinal cord/brainstem; cross midline and ascend to thalamus.

Third-Order Neurons

Located in thalamus; project to cortex.

Fourth-Order Neurons

Located in sensory cortex; produce conscious perception.

Dorsal Column System

Fine touch, vibration, pressure; ascends ipsilaterally then crosses in medulla.

Anterolateral System

Pain, temperature, light touch; crosses immediately in spinal cord.

Substance P

Neurotransmitter for pain transmission.

Fast Pain

A-delta fibers; sharp, localized.

Slow Pain

C fibers; dull, aching, throbbing.

Referred Pain

Visceral pain perceived at skin sites sharing the same spinal segment.