BIOL 109 Chap 10 (Chapter 14)

autonomic nervous system

Autonomic nervous system (ANS)

division of the peripheral nervous system located throughout the body that controls involuntary functions by regulating cardiac muscle, smooth muscle, and glands to maintain homeostasis

Visceral reflex arc

pathway involving receptors in organs, sensory neurons, integration in the central nervous system, and autonomic motor output that produces automatic responses in internal organs

Preganglionic neuron

neuron with cell body in the brainstem or spinal cord whose axon travels to an autonomic ganglion where it synapses with another neuron to relay signals

Postganglionic neuron

neuron with cell body in an autonomic ganglion whose axon extends to cardiac muscle, smooth muscle, or glands to produce a response

Autonomic ganglion

cluster of neuron cell bodies in the peripheral nervous system where synapses occur between preganglionic and postganglionic neurons to relay autonomic signals

Somatic motor pathway

single neuron pathway from the central nervous system to skeletal muscle that produces voluntary movement without synapsing in a ganglion

Autonomic motor pathway

two neuron pathway involving preganglionic and postganglionic neurons that synapse in a ganglion before reaching target organs to control involuntary activity

Short axon (autonomic)

nerve fiber found in neurons located close to their synapse point where distance to next structure is minimal due to ganglion placement

Long axon (autonomic)

nerve fiber found in neurons that must travel farther distances due to ganglion location relative to spinal cord or target organ

Sympathetic preganglionic neuron

neuron with cell body in lateral horn of T1-L2 spinal cord whose short axon travels through ventral root and white ramus to synapse in sympathetic ganglia

Sympathetic postganglionic neuron

neuron with cell body in chain or collateral ganglia whose long axon travels to target organs to produce stress responses

Sympathetic chain ganglia

paired ganglia located along both sides of the vertebral column that receive input from preganglionic neurons and distribute signals to postganglionic neurons

Collateral ganglia

ganglia located anterior to the vertebral column near the abdominal aorta that receive splanchnic nerve input and send signals to abdominal and pelvic organs

Splanchnic nerves

nerves carrying preganglionic fibers from thoracic spinal cord through chain ganglia to collateral ganglia for synapsing

White ramus communicans

branch containing myelinated preganglionic sympathetic fibers that connect spinal nerves to sympathetic chain ganglia

Gray ramus communicans

branch containing unmyelinated postganglionic sympathetic fibers that return to spinal nerves to reach target tissues

Acetylcholine (ACh)

neurotransmitter released by all preganglionic neurons and some postganglionic neurons that binds to cholinergic receptors to transmit signals

Norepinephrine (NE)

neurotransmitter released by most sympathetic postganglionic neurons that binds to adrenergic receptors to activate stress responses

Epinephrine (Epi)

hormone released from adrenal medulla into bloodstream that enhances sympathetic effects by binding to adrenergic receptors throughout the body

Adrenergic receptor

receptor on target cells of cardiac muscle, smooth muscle, and glands that binds norepinephrine or epinephrine to produce sympathetic effects

Alpha 1 receptor

receptor on smooth muscle that causes contraction when activated leading to effects like vasoconstriction

Alpha 2 receptor

receptor that regulates neurotransmitter release and modulates sympathetic activity

Beta 1 receptor

receptor on cardiac muscle that increases heart rate and contraction strength when activated

Beta 2 receptor

receptor on smooth muscle that causes relaxation such as bronchodilation in airways

Beta 3 receptor

receptor involved in fat metabolism and energy regulation in adipose tissue

Adrenal medulla

inner region of adrenal gland composed of modified neurons that release epinephrine and norepinephrine into blood when stimulated by sympathetic input

Chromaffin cells

modified postganglionic neurons in adrenal medulla that release hormones into bloodstream instead of using synapses

Sympathetic activation

state in which signals increase heart rate, dilate airways, reduce digestion, and mobilize energy to prepare for stress

Parasympathetic preganglionic neuron

neuron with cell body in brainstem or sacral spinal cord whose long axon travels to ganglia near or within target organs

Parasympathetic postganglionic neuron

neuron with cell body in ganglia near or in target organs whose short axon delivers signals directly to tissues

Parasympathetic ganglion

ganglion located near or within target organs where synapse occurs between preganglionic and postganglionic neurons

Cholinergic receptor

receptor on neurons or target cells that binds acetylcholine and mediates parasympathetic or ganglionic signaling

Nicotinic receptor

receptor located on postganglionic neurons in autonomic ganglia that binds acetylcholine and causes depolarization

Muscarinic receptor

receptor located on target organs that binds acetylcholine and produces parasympathetic effects

Parasympathetic activation

state in which signals decrease heart rate, increase digestion, stimulate gland secretion, and promote energy storage

Hypothalamus

brain region in the diencephalon that integrates autonomic functions and maintains homeostasis by controlling both divisions

Reticular formation

network in the brainstem that processes autonomic signals and helps regulate vital functions like heart rate and breathing

Amygdala

brain structure involved in emotional processing that influences autonomic responses through connections with hypothalamus

Cerebral cortex

outer brain region that can influence autonomic activity through conscious thought and decision making

Autonomic centers

regions in hypothalamus and brainstem that coordinate and regulate involuntary body functions

Dual innervation

condition where most organs receive input from both sympathetic and parasympathetic divisions allowing balanced regulation of function