Autonomic Nervous System

Sympathetic trunk ganglia

(paravertebral or chain ganglia) house sympathetic ganglionic neuron cell bodies. One sympathetic ganglion is approximately associated with each spinal nerve.

Four Cranial Nerves of Parasympathetic Division

1. Oculomotor (CN III) 2. Facial (CN VII) 3. Glossopharyngeal (CN IX) 4. Vagus (CN X)

Autonomic Nervous System (ANS)

A complex system of nerves that govern involuntary actions.

CNS Control of Autonomic Function Cerebrum

ANS activities are affected by conscious activities in cerebral cortex and subconscious communication between association areas in the cortex with centers of sympathetic and parasympathetic control in the hypothalamus. Sensory processing in the thalamus and emotional states controlled in the limbic system directly affect the hypothalamus.

CNS Control of Autonomic Function

Autonomic function is influenced by the: cerebrum hypothalamus brainstem spinal cord

Cervical Sympathetic Ganglia

Cervical portion of each sympathetic trunk is partitioned into three ganglia: Superior ganglia Middle ganglia Inferior ganglia

Parasympathetic division

Conservation of energy and replenishment of nutrient stores.

Sympathetic system

Controls 'fight or flight' responses: Quickly activates the body Increasing heart rate Dilating the pupils Dilating the blood vessels to the muscles Increasing skin sweating Suppressing digestion

Parasympathetic system

Controls the opposite responses to 'fight or flight' responses - The 'rest and digest' responses: Depresses the activity of the body Decreasing heart rate Constricting the pupils Constricting the blood vessels to the muscles Stimulating digestion (peristalsis and salivary production

Terminal ganglia

Ganglionic neurons are found close to the target organ.

Intramural ganglia

Ganglionic neurons are found in the wall of the target organ.

Middle and Inferior Cervical Ganglion

House neuron cell bodies that extend postganglionic axons to the thoracic viscera.

Dual Innervation

Innervation by postganglionic axons from both ANS divisions. The actions of the divisions usually oppose each other (antagonistic effects).

CNS Control of Autonomic Function Hypothalamus

Integration and command center for autonomic functions. Contains nuclei that control visceral functions in both divisions of the ANS. Communicates with other CNS regions, including cerebral cortex, thalamus, brainstem, cerebellum, and spinal cord. Central brain structure involved in emotions and drives that act through the ANS.

Celiac Ganglion

Location—adjacent to origin of celiac artery. Preganglion axons—greater thoracic splanchnic nerves (T5-T9 segment of spinal cord). Postganglionic axons—innervate stomach, spleen, liver, gallbladder, proximal duodenum, part of pancreas.

Superior Mesenteric Ganglion

Location—adjacent to origin of superior mesenteric artery. Preganglionic axons—lesser and least thoracic splanchnic nerves (T10-T12 segment of spinal cord). Postganglionic axons—innervate distal duodenum, part of pancreas, remainder of small intestine, proximal large intestine, kidneys, proximal part of ureters.

Inferior Mesenteric Ganglion

Location—adjacent to the origin of the inferior mesenteric artery. Preganglionic axons—lumbar splanchnic nerves (L1-L2 segment of spinal cord). Postganglionic axons—innervate the distal colon, rectum, urinary bladder, distal ureter, and most of reproductive organs.

CNS Control of Autonomic Function Brainstem

Nuclei in the mesencephalon, pons, medulla oblongata mediate visceral reflexes. Reflex centers control accommodation of the lens, blood pressure changes, blood vessel diameter changes, digestive activities, heart rate changes, and pupil size. Centers for cardiac, digestive, and vasomotor functions are housed within the brainstem.

Superior Cervical Ganglion

Postganglionic axons from cell bodies distribute to structures in the head and neck. Innervate sweat glands Innervate smooth muscle in blood vessels, dilator pupillae muscle of the eye, and the superior tarsal muscle of the eye

Spinal Sacral Nerve (Preganglionic Axons)

Preganglionic axons branch to form pelvic splanchnic nerves, which contribute to the superior and inferior hypogastric plexus.

Spinal Thoracic/Lumbar Nerve (Preganglionic Axons)

Preganglionic axons travel with somatic motor neuron axons to exit the spinal cord and enter the anterior roots and then the T1-L2 spinal nerves.

Spinal Sacral Nerve (Preganglionic Fibers)

Preganglionic fibers project to ganglionic neurons within terminal or intramural ganglia of large intestine, rectum, reproductive organs, urinary bladder, and distal ureter.

Spinal Sacral Nerves (Preganglionic Neurons)

Preganglionic neuron cell bodies are housed within lateral gray regions of S2-S4 spinal cord segments.

Craniosacral division (Parasympathetic Division)

Preganglionic neurons are housed within nuclei in the brainstem and within lateral gray regions of the S2-S4 spinal cord segments

Thoracolumbar division (Sympathetic Division)

Preganglionic sympathetic neuron cell bodies are housed in lateral horn between first thoracic (T1) and second lumbar (L2) spinal segments

Sympathetic division

Preparation of body for emergencies; increased activity of this division results in increased alertness and metabolic activity.

Prevertebral Ganglia

Prevertebral ganglia include: Celiac ganglion Superior mesenteric ganglion Inferior mesenteric ganglion

CNS Control of Autonomic Function Spinal Cord

Processes some autonomic responses, notably the parasympathetic activities associated with defecation and urination, without involvement of the brain. Higher centers in the brain may consciously inhibit these reflex activities.

Somatic Nervous System (SNS)

SNS operates under our conscious (voluntary) control.

SNS

Single lower motor neuron axon extends uninterrupted from the spinal cord to one or more muscle fibers.

SNS functions

Somatic motor neurons innervate skeletal muscle fibers, causing conscious voluntary movement.

Sympathetic Trunk

Sympathetic trunks are located anterior to spinal nerves and immediately lateral to vertebral column.

Autonomic tone

The balance between sympathetic and parasympathetic stimulation of an effector organ.

Preganglionic neuron

The first neuron in the ANS pathway. Its cell body is in the brain and spinal cord. It extends to the second cell body housed within an autonomic ganglion in the peripheral nervous system.

Divisions of ANS

The motor component of the ANS is subdivided into: Parasympathetic division Sympathetic division (Generally innervating the same organs but producing opposite physiological responses)

Hypothalamus

The overall regulator and controls the activities of sympathetic and parasympathetic systems.

ANS functions

The part of the peripheral nervous system that subconsciously maintains, monitors and controls our internal bodily functions: heart rate blood vessel diameter smooth muscle surrounding organs secretions of glands

Ganglionic neuron

The second neuron in the ANS pathway. It extends from its cell body to the effector (target) cells.

ANS

Two-neuron chain innervates muscles and glands.