Autonomic Nervous System Function - Chest and Abdomen

Vocabulary practice flashcards covering the sympathetic and parasympathetic innervation, receptor subtypes, and physiological functions of the autonomic nervous system on the chest and abdominal viscera.

Sympathetic Preganglionic Neurons (Thoracic Viscera)

Preganglionic autonomic neurons that supply thoracic organs, originating in the lateral horn cells (LHCs) of the upper $4-5$ thoracic spinal segments ($T_{1-5}$).

Thoracic Sympathetic Ganglia Relay

The relay sites in the paravertebral sympathetic chain for preganglionic thoracic fibers, consisting of the cervical ganglia and upper $4-5$ thoracic ganglia.

Cardiac Properties ($4 \times 4$)

The four intrinsic cardiac properties increased by sympathetic stimulation via $\beta_1$ receptors: automaticity (rate), conductivity (rate of conduction), excitability, and contractility (force of contraction).

Coronary Vasodilatation (Sympathetic Effect)

The indirect dilation of coronary blood vessels occurring in response to increased cardiac work and metabolic demand, mediated through $\beta_2$ adrenergic receptors.

Bronchial Tree (Sympathetic Effect)

Dilatation and relaxation of the entire bronchial tree mediated by $\beta_2$ adrenergic receptors.

Pulmonary Blood Vessels (Sympathetic Effect)

Vasoconstriction of pulmonary vasculature mediated via $\alpha_1$ adrenergic receptors.

Vagus Nerve (Cr X)

The tenth cranial nerve containing $75\%$ of all parasympathetic nerve fibers, arising from the vagal nuclei (nucleus ambiguus and dorsal motor nucleus [DM]) in the medulla oblongata to innervate thoracic and abdominal viscera.

Terminal Ganglia

Parasympathetic peripheral ganglia located directly within the walls of effector organs where preganglionic vagal fibers synapse.

Cardiac Ventricles (Parasympathetic Supply)

The lower heart chambers that lack vagal parasympathetic innervation; the vagus nerve supplies the atria only ($2 \times 4$).

Atrial Properties (Parasympathetic Effect)

The inhibition of all properties of atrial cardiac muscle, along with decreased coronary blood flow and reduced $O_2$ consumption, mediated via $M_2$ muscarinic receptors.

Bronchial Tree (Parasympathetic Effect)

Constriction of bronchi and bronchioles accompanied by increased secretions from bronchial glands, mediated through $M_3$ muscarinic receptors.

Esophageal Peristalsis (Parasympathetic Effect)

An increase in esophageal motor activity and peristaltic contractions mediated by muscarinic $M_3$ receptors.

Sympathetic Preganglionic Neurons (Abdominal Viscera)

Preganglionic autonomic neurons that supply abdominal viscera, arising from the lateral horn cells (LHCs) of segments $T_{5-12}$.

Greater Splanchnic Nerve

Splanchnic nerve pathway formed by preganglionic sympathetic fibers that pass through the paravertebral chain without synapsing to reach collateral (prevertebral) ganglia.

Celiac Ganglion

A collateral sympathetic ganglion receiving preganglionic fibers from $T_{5-9}$ that sends postganglionic fibers to the stomach, liver, pancreas, and spleen.

Superior Mesenteric Ganglion

A collateral sympathetic ganglion receiving preganglionic fibers from $T_{10-12}$ that innervates the small intestine and proximal colon.

Adrenal Medulla Innervation

Direct sympathetic innervation from preganglionic fibers originating at $T_{9-10}$ that bypass collateral ganglia and synapse directly on specialized chromaffin cells via $N_N$ receptors.

Adrenal Medullary Secretions

Endocrine catecholamines discharged directly into the blood, composed of approximately $80\%$ adrenaline and $20\%$ noradrenaline.

GIT Wall Muscles (Sympathetic vs. Parasympathetic)

Inhibited (relaxed) by sympathetic activity via $\beta_2$ receptors; stimulated (motor) by parasympathetic activity via $M_3$ receptors.

GIT Sphincters (Sympathetic vs. Parasympathetic)

Constricted (motor) by sympathetic activity via $\alpha_1$ receptors (e.g., cardiac, pyloric, and ileocecal); relaxed (inhibited) by parasympathetic activity via $M_3$ receptors.

Abdominal Arterioles (Sympathetic Effect)

Vasoconstriction ($\text{VC}$) of arterioles supplying the stomach, small intestine, proximal large intestine, kidney, pancreas, and liver mediated by $\alpha_1$ adrenergic receptors.

Hepatic Glycogenolysis (Sympathetic Effect)

Stimulation of glycogen breakdown in the liver to increase blood glucose levels, mediated by $\alpha_1$ and $\beta_2$ adrenergic receptors.

Splenic Capsule (Sympathetic Effect)

Capsular contraction mediated by $\alpha_1$ receptors that empties stored blood rich in red blood cells (RBCs) into the systemic circulation.

Pancreatic Secretions (Sympathetic Control)

Reduced exocrine acinar secretions ($\alpha$ receptor) combined with decreased insulin ($\alpha_2$ receptor) and increased glucagon ($\beta_2$ receptor) islet secretions.

Gallbladder Evacuation (Parasympathetic Effect)

Vagus-mediated evacuation achieved through wall contraction and simultaneous relaxation of the sphincter of Oddi via muscarinic $M_3$ receptors.