11: Neural Pathways and Autonomic Reflexes

Comprehensive vocabulary flashcards covering the Autonomic Nervous System (ANS), reflex arcs, sympathetic and parasympathetic divisions, neurotransmitters, and anatomical pathways based on lecture notes.

Autonomic Nervous System (ANS)

Also called the involuntary nervous system, this subdivision of the PNS has a certain amount of functional independence and provides subconscious control over visceral effectors.

Visceral Effectors

The targets regulated by the autonomic nervous system, specifically smooth muscle, cardiac muscle, and glands.

Enteric Nervous System (ENS)

The third division of the ANS, consisting of a large intrinsic neuronal network embedded in the wall of the gastrointestinal system.

Autonomic Reflex Arc

A reflex pathway consisting of a receptor, sensory neuron, integration center, two consecutive motor neurons, and an effector (smooth muscle, cardiac muscle, or glands).

ANS Integration Center

The hypothalamus, which acts as the main integrative center for the autonomic nervous system and regulates whole-body homeostasis.

Preganglionic Neuron

The first motor neuron in the autonomic two-neuron chain, with its cell body in the brainstem or spinal cord and a thin, lightly myelinated axon.

Postganglionic Neuron

The second motor neuron in the autonomic two-neuron chain, with its cell body in an autonomic ganglion and an even thinner, nonmyelinated axon that innervates the effector.

Autonomic Ganglion

A motor ganglion containing the cell bodies of postganglionic autonomic motor neurons; it is the site of synapse between pre- and postganglionic neurons.

Chromaffin Cells

Specialized neuroendocrine cells in the adrenal medulla that, when stimulated by sympathetic preganglionic axons, release epinephrine and norepinephrine into the blood.

Cholinergic Axons

Axons that release the neurotransmitter Acetylcholine (ACh), including all somatic motor neurons, all parasympathetic neurons, and sympathetic preganglionic axons.

Adrenergic Axons

Axons that release the neurotransmitter Norepinephrine (NE), which includes most sympathetic postganglionic axons.

Dual Innervation

A feature where many effector organs are innervated by both sympathetic and parasympathetic divisions, allowing their actions to counterbalance each other.

Sympathetic Division

Also known as the thoracolumbar division, it promotes functions to prepare the body for action, often referred to as the 'fight-or-flight' response.

Parasympathetic Division

Also known as the craniosacral division, it promotes body maintenance, energy conservation, and functions referred to as 'rest-and-digest'.

Lateral Gray Horns

Specific regions of the spinal cord in segments $T1$ to $L2$ that house the cell bodies of sympathetic preganglionic neurons.

Sympathetic Trunk Ganglia

Also called paravertebral ganglia, these are two vertical rows of ganglia located on either side of the vertebral column from the base of the skull to the coccyx.

Collateral Ganglia

Also called prevertebral ganglia, these are located anterior to the vertebrae and abdominal aorta and are associated with controlling abdominal organs.

White Rami Communicantes

Myelinated bundles of sympathetic preganglionic axons that connect the ventral ramus of a spinal nerve with the nearest sympathetic trunk ganglion ($T1$ to $L2$ only).

Gray Rami Communicantes

Unmyelinated bundles of sympathetic postganglionic axons that connect the sympathetic trunk ganglion back to the ventral ramus of the spinal nerve at all spinal levels.

Terminal (Intramural) Ganglia

Autonomic ganglia of the parasympathetic division located very close to, or within the wall of, the target effector organ.

Vagus Nerves (CN X)

The pair of cranial nerves that carry approximately $90\%$ of all preganglionic parasympathetic axons in the body.

SLUDD

An acronym for specific parasympathetic responses: Salivation, Lacrimation, Urination, Digestion, and Defecation.