Autonomic and Sensory Nervous System Review

Comprehensive vocabulary flashcards covering the Autonomic Nervous System, adrenergic and cholinergic receptors, sensory receptors, nerve fibers, somatosensory pathways, and clinical conditions of taste, smell, and vision based on the lecture notes.

Autonomic Nervous System (ANS)

A component of the nervous system composed of sympathetic and parasympathetic divisions that controls and regulates visceral organs, glands, and blood vessels alongside the endocrine system.

Sympathetic Nervous System

A division of the ANS that prepares the body for emergencies, characterized by thoracolumbar efferent outflow from the lateral horn of $T_1 - L_{2/3}$.

Parasympathetic Nervous System

A division of the ANS that conserves and stores energy, characterized by craniosacral efferent outflow from brainstem cranial nerve nuclei ($CNIII$, $CNVII$, $CNIX$, $CNX$) and $S_2 - S_4$.

Sympathetic Ganglionic Pathway Sketch

Illustration depicting preganglionic fibers releasing acetylcholine ($ACh$) in sympathetic ganglia and postganglionic fibers releasing norepinephrine ($NE$) to effector organs.

Pheochromocytoma

A tumor of the adrenal medulla that secretes excessive amounts of catecholamines and results in increased urinary excretion of 3-methoxy-4-hydroxymandelic acid ($VMA$).

Chromaffin Cells

Specialized cells in the adrenal medulla innervated by preganglionic sympathetic fibers that secrete epinephrine ($80\%$) and norepinephrine ($20\%$) directly into circulation.

Adrenergic vs Cholinergic Neurotransmitters

Classification of autonomic nerve fibers based on their released neurotransmitter: adrenergic fibers release norepinephrine ($NE$) for sympathetic pathways, while cholinergic fibers release acetylcholine ($ACh$) for parasympathetic pathways.

$\alpha_1$ Adrenergic Receptor

Postsynaptic receptor on vascular smooth muscle, pupillary smooth muscle, and sphincters that produces excitation and contraction via $IP_3$ formation and increased intracellular $Ca^{2+}$.

$\alpha$ Adrenergic Receptors Overview

Summary table comparing postsynaptic $\alpha_1$ receptors (causing muscle contraction, mydriasis, and piloerection) with mostly presynaptic $\alpha_2$ receptors (inhibiting neurotransmitter release and lipolysis).

$\alpha_2$ Adrenergic Receptor

Predominantly presynaptic receptor on nerve terminals, fat cells, and platelets that produces inhibition by inhibiting adenylate cyclase and decreasing cyclic $AMP$ ($cAMP$).

$\beta_1$ Adrenergic Receptor

Receptor located in the heart ($SA$ node, $AV$ node, myocardium) that produces excitation by increasing heart rate, conduction velocity, and contractility via increased cyclic $AMP$ ($cAMP$).

$\beta$ Adrenergic Receptors Overview

Summary table detailing $\beta_1$ receptors (located in the heart to stimulate rate and force) and $\beta_2$ receptors (located in vascular/bronchial smooth muscle to induce relaxation and glycogenolysis).

Propranolol

A non-selective $\beta$ blocker that inhibits the effect of norepinephrine on $\beta_1$ receptors, thereby decreasing heart rate and myocardial contractility.

Albuterol

A $\beta_2$ agonist that selectively relaxes bronchial smooth muscle to treat broncho-constriction in conditions such as asthma.

Atenolol

A cardioselective $\beta_1$ blocker used to treat heart rate and arrhythmia without blocking $\beta_2$ receptors or causing bronchospasm in asthmatic patients.

Nicotinic Receptor

An ionotropic cholinergic receptor found in autonomic ganglia, the adrenal medulla, and the neuromuscular junction that produces excitation upon binding acetylcholine or nicotine.

Muscarinic Receptor

A metabotropic cholinergic receptor located in the heart, smooth muscle, and glands that is activated by acetylcholine or muscarine and blocked by atropine.

Autonomic Pancreatic Regulation

Summary table showing that sympathetic stimulation inhibits insulin via $\alpha$ receptors and activates insulin via $\beta$ receptors, while exocrine secretion is inhibited by $\alpha$ receptors and activated by parasympathetic input.

Mechanoreceptors

Sensory receptors that transduce mechanical stimuli, including Pacinian corpuscles, joint receptors, muscle stretch receptors, auditory hair cells, and carotid sinus baroreceptors.

Photoreceptors

Sensory receptors consisting of rods and cones located in the retina that transduce light signals.

Chemoreceptors

Sensory receptors sensitive to chemical molecules, including olfactory receptors, taste receptors, osmoreceptors, and carotid body $O_2$ receptors.

Nociceptors

Free nerve endings in skin, muscle, and viscera that detect painful or noxious stimuli using substance $P$ as a primary neurotransmitter.

A-alpha Nerve Fibers

Large alpha-motoneuron nerve fibers characterized by having the fastest conduction velocity among peripheral nerve fibers.

C Nerve Fibers

Unmyelinated postganglionic autonomic and slow-pain nerve fibers characterized by having the slowest conduction velocity.

Tonic Receptors

Slowly adapting sensory receptors, such as muscle spindles and slow pain receptors, that fire repetitively in response to a prolonged stimulus.

Phasic Receptors

Rapidly adapting sensory receptors, such as Pacinian corpuscles, that show a decline in action potential frequency over time during a constant stimulus.

Receptor Potential

Also known as a generator potential, the graded membrane potential change produced in a sensory receptor when an environmental stimulus opens ion channels.

Dorsal Column System

A somatosensory pathway that conveys fine touch, pressure, two-point discrimination, and vibration, crossing the midline at the medulla oblongata.

Anterolateral System

A somatosensory pathway that conveys temperature, pain, and light touch, crossing the midline in the spinal cord before ascending to the contralateral thalamus.

Referred Pain

Pain originating from visceral organs that is perceived at cutaneous sites sharing innervation from the same spinal cord segment (e.g., heart pain referred to the left shoulder).

Ageusia

The complete loss of taste sensation, which can occur secondary to damage to the facial nerve ($CNVII$).

Glossodynia

A clinical condition characterized by a burning sensation localized to the tongue.

Benign Migratory Glossitis

Also known as geographic tongue, a condition presenting with irregular, inflamed patches with white borders on the surface of the tongue.

Anosmia

The complete absence or loss of the sense of smell.

Phantosmia

The olfactory perception or phenomenon of smelling odors that are not actually present in the environment.

Mitral Cells

Second-order neurons located in the olfactory bulb whose axons form the olfactory tract projecting to the cerebral cortex.

Sclera

The tough, white, fibrous outer layer of the eyeball measuring approximately $2.5\,cm$ in diameter that maintains, protects, and supports eye structure.

Cornea

The transparent anterior section of the sclera that refracts light entering the eye and acts as the outer window of the eyeball.