The Autonomic Nervous System and Higher-Order Functions

Comprehensive vocabulary flashcards detailing the subdivisions, pathways, neurotransmitters, receptors, higher-order memory functions, sleep states, and brain neurochemistry of the Autonomic Nervous System.

Autonomic Nervous System (ANS)

Also called the visceral motor system, a division of the peripheral nervous system that provides involuntary control of visceral effectors such as smooth muscle, glands, cardiac muscle, and adipocytes.

Nervous System Subdivisions

The structural organization dividing the nervous system into Central (brain and spinal cord) and Peripheral (sensory and motor), with motor further split into Somatic and Autonomic divisions.

Autonomic Ganglia

Clusters of cell bodies of visceral motor neurons located outside of the Central Nervous System (CNS) that innervate visceral effectors.

Autonomic Motor Pathway

A motor pathway in which visceral motor neurons in the CNS synapse with visceral motor neurons inside autonomic ganglia, which then send postganglionic fibers to target organs.

Preganglionic Neurons

Autonomic motor neurons with cell bodies in the brainstem and spinal cord that project to autonomic ganglia and synapse with postganglionic neurons.

Postganglionic Neurons

Autonomic motor neurons with cell bodies located inside autonomic ganglia whose axons synapse directly with peripheral target organs.

Sympathetic Division

The fight or flight division of the ANS that prepares the body to deal with stress or emergency by increasing alertness, respiratory rate, metabolic rate, and muscular abilities.

Parasympathetic Division

The rest and digest division of the ANS that conserves energy and maintains the resting metabolic rate.

Thoracolumbar Outflow

The sympathetic division pathway, characterized by preganglionic neuron cell bodies located in the thoracic and lumbar regions of the spinal cord.

Craniosacral Outflow

The parasympathetic division pathway, characterized by preganglionic neuron cell bodies located in the brainstem and sacral regions of the spinal cord.

Sympathetic Chain Ganglia

Paravertebral ganglia located on either side of the vertebral column where preganglionic fibers synapse on postganglionic neurons that pass through gray rami communicantes to innervate body wall, thoracic cavity, head, neck, and limb effectors.

Collateral Ganglia

Prevertebral ganglia located anterior to the vertebral column whose postganglionic neurons innervate abdominopelvic tissues and viscera to reduce blood flow and energy use by non-essential organs.

Celiac Ganglia

Collateral ganglia whose postganglionic fibers innervate the stomach, liver, gallbladder, pancreas, and spleen.

Superior Mesenteric Ganglion

A collateral ganglion whose postganglionic fibers innervate the small intestine and the proximal two-thirds of the large intestine.

Inferior Mesenteric Ganglion

A collateral ganglion whose postganglionic fibers innervate the kidneys, urinary bladder, last segment of the large intestine, and sex organs.

Adrenal Medullae

Modified sympathetic ganglia at the center of the adrenal glands containing specialized endocrine cells that secrete epinephrine and norepinephrine directly into general circulation.

Alpha-1 ($\alpha_1$) Receptors

Adrenergic GPCRs found primarily in smooth muscle cells that activate IP3/DAG, increase intracellular $\text{Ca}^{++}$ release, activate Protein Kinase C, and produce excitatory effects.

Alpha-2 ($\alpha_2$) Receptors

Adrenergic GPCRs found on pre- and postsynaptic neurons that activate an inhibitory G protein, inhibit adenylyl cyclase, reduce intracellular cAMP, and exert inhibitory effects.

Beta-1 ($\beta_1$) Receptors

Adrenergic receptors located in the heart and kidneys whose stimulation increases cAMP levels and increases metabolic activity in heart and muscles.

Beta-2 ($\beta_2$) Receptors

Adrenergic receptors located in eyes, blood vessels, lungs, liver, pancreas, and GI/GU systems that cause relaxation or dilation, such as dilation of respiratory passageways.

Beta-3 ($\beta_3$) Receptors

Adrenergic receptors found in adipocytes that stimulate lipolysis, the breakdown of triglycerides.

Nicotinic Acetylcholine Receptors

Ionotropic chemically gated $\text{Na}^+$ channels bound by acetylcholine or nicotine located on postganglionic autonomic neurons that cause excitation.

Muscarinic Acetylcholine Receptors

Metabotropic G-protein-coupled receptors bound by acetylcholine or muscarine that produce excitatory or inhibitory responses on parasympathetic target organs.

Vagus Nerve (CN X)

The cranial nerve responsible for providing $75\%$ of all parasympathetic output.

Pelvic Nerves

Nerves formed by preganglionic parasympathetic fibers leaving sacral segments $S_2, S_3, S_4$ of the spinal cord to innervate pelvic organs.

ANS Neurotransmitter Scheme

The overarching categorization of ANS neurotransmitters into Acetylcholine (acting on ionotropic nicotinic or metabotropic muscarinic receptors) and Epinephrine/Norepinephrine (acting on metabotropic adrenergic receptors).

ANS Synaptic Transmission Pathways

The exact arrangement of preganglionic ACh release onto nicotinic receptors and postganglionic release of NE/Epi (onto adrenergic receptors) or ACh (onto muscarinic receptors).

Fact Memories

Specific bits of factual information stored in the cerebral cortex.

Skill Memories

Learned motor behaviors stored in the cerebral cortex and cerebellar cortex that are incorporated unconsciously with repetition.

Memory Consolidation

The process of converting short-term memory into long-term memory, requiring essential structures including the amygdala and hippocampus.

Secondary Memories

Long-term memories that fade with time and require conscious effort to recall.

Tertiary Memories

Long-term memories that last for a lifetime and do not fade.

Deep Sleep

Also called slow-wave or non-REM (NREM) sleep; a period of total relaxation where cerebral cortex activity is minimal and heart rate, blood pressure, respiratory rate, and energy use decline by up to $30\%$.

Rapid Eye Movement (REM) Sleep

A sleep state characterized by active dreaming, rapid eye movements, fluctuating blood pressure and respiration, somatic motor neuron inhibition, and an EEG wave pattern similar to the awake state.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Antidepressant drugs—including Fluoxetine (Prozac), Celexa, Luvox, Zoloft, and Paxil—that slow the removal of serotonin at synapses.

Dopamine

A brain neurotransmitter vital for controlling intentional movements; inadequate levels cause Parkinson's disease, excessive production is linked to schizophrenia, and amphetamines stimulate its secretion.