Cranial Nerves and the Autonomic Nervous System

Vocabulary flashcards covering the cranial nerves, cranial nerve pathologies, and the structural and functional divisions of the autonomic nervous system.

Optic and Trochlear Nerves

The two cranial nerves that serve as exceptions to the rule that cranial nerves transmit impulses exclusively to receptors on the same side of the body.

Trigeminal Neuralgia (Tic Douloureux)

A disorder caused by inflammation of the trigeminal nerve (cranial nerve V), marked by recurring, brief episodes of intense pain triggered by everyday activities such as eating, drinking, shaving, brushing teeth, or temperature changes.

Bell's Palsy

A disorder resulting from dysfunction of the facial nerve (cranial nerve VII) that causes paralysis and sagging of facial muscles on one side, drooping of the eyelid, and loss of facial expression; it typically resolves within $3$ to $5\text{ weeks}$.

Autonomic Nervous System (ANS)

A subdivision of the nervous system that autonomously regulates activities maintaining homeostasis, such as digestive enzyme secretion, hormone secretion, and blood vessel constriction and dilation.

Visceral Motor System

An alternate term for the autonomic nervous system, reflecting its role in delivering motor impulses to cardiac muscle, smooth muscle, and glands rather than skeletal muscle.

Baroreceptors

Pressure receptors located in the carotid artery that detect increases in blood pressure during an autonomic visceral reflex arc.

Visceral Reflex

An involuntary reflex arc regulated by the autonomic nervous system that exerts control over an organ (effector) rather than a skeletal muscle.

Sympathetic Division

The division of the autonomic nervous system that primes the body for physical exertion and stress by producing the 'fight or flight' response, increasing heart rate, dilating bronchioles, and inhibiting digestion.

Parasympathetic Division

The division of the autonomic nervous system responsible for a calming effect and promoting the 'resting and digesting' state, reducing heart rate and stimulating digestion and bladder contraction.

Autonomic Tone

The continuous, background level of activity maintained by the simultaneous operation of both the sympathetic and parasympathetic divisions of the autonomic nervous system.

Thoracolumbar Division

Another name for the sympathetic division of the autonomic nervous system, designating its origin from the thoracic and lumbar segments of the spinal cord.

Sympathetic Ganglia

Chains of nerve cell bodies situated alongside both sides of the spinal cord where short, myelinated preganglionic sympathetic fibers synapse.

Preganglionic Neurons (Sympathetic)

Short, myelinated neurons originating within the spinal cord that branch to synapse with multiple postganglionic neurons simultaneously across the sympathetic ganglionic chain.

Adrenal Medulla

The inner core of the adrenal gland stimulated directly by sympathetic preganglionic fibers to secrete epinephrine and norepinephrine into the bloodstream, prolonging the sympathetic response.

Craniosacral Division

Another name for the parasympathetic division of the autonomic nervous system, referencing its origin in the brain and the sacral region of the spinal cord.

Vagus Nerve (Cranial Nerve X)

The cranial nerve that carries approximately $90\%$ of all parasympathetic preganglionic fibers, distributing them to organs throughout both the thoracic and abdominal cavities.

Pelvic Nerves

Nerves through which parasympathetic fibers exit the sacral spinal cord to innervate and regulate portions of the colon and the urinary bladder.

Parasympathetic Ganglia

Autonomic ganglia situated in or immediately near the target organs, resulting in long preganglionic fibers, short postganglionic fibers, and localized effects.

Oculomotor Nerve (Cranial Nerve III)

A cranial nerve that conveys parasympathetic fibers to the ciliary muscle (thickening the lens) and the pupillary constrictor (constricting the pupil), and whose function is compromised by brain swelling from head trauma.

Glossopharyngeal Nerve (Cranial Nerve IX)

A cranial nerve that conveys afferent sensory signals from carotid baroreceptors to the medulla oblongata and carries parasympathetic motor fibers that stimulate salivation.

Norepinephrine

The primary neurotransmitter employed by postganglionic fibers of the sympathetic division to produce widespread effector responses.

Acetylcholine

The primary neurotransmitter utilized by the parasympathetic division to generate local effector responses in target organs.