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Key Terms Chapter 15: The Autonomic Nervous System

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    62666
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    acetylcholine (ACh)
    neurotransmitter that binds at a motor end-plate to trigger depolarization
    adrenal medulla
    interior portion of the adrenal (or suprarenal) gland that releases epinephrine and norepinephrine into the bloodstream as hormones
    adrenergic
    synapse where norepinephrine is released, which binds to α- or β-adrenergic receptors
    afferent branch
    component of a reflex arc that represents the input from a sensory neuron, for either a special or general sense
    agonist
    any exogenous substance that binds to a receptor and produces a similar effect to the endogenous ligand
    alpha (α)-adrenergic receptor
    one of the receptors to which epinephrine and norepinephrine bind, which comes in two subtypes: α1 and α2
    antagonist
    any exogenous substance that binds to a receptor and produces an opposing effect to the endogenous ligand
    anticholinergic drugs
    drugs that interrupt or reduce the function of the parasympathetic system
    autonomic tone
    tendency of an organ system to be governed by one division of the autonomic nervous system over the other, such as heart rate being lowered by parasympathetic input at rest
    baroreceptor
    mechanoreceptor that senses the stretch of blood vessels to indicate changes in blood pressure
    beta (β)-adrenergic receptor
    one of the receptors to which epinephrine and norepinephrine bind, which comes in three subtypes: β1, β2, and β3
    cardiac accelerator nerves
    preganglionic sympathetic fibers that cause the heart rate to increase when the cardiovascular center in the medulla initiates a signal
    cardiovascular center
    region in the medulla that controls the cardiovascular system through cardiac accelerator nerves and vasomotor nerves, which are components of the sympathetic division of the autonomic nervous system
    celiac ganglion
    one of the collateral ganglia of the sympathetic system that projects to the digestive system
    central neuron
    specifically referring to the cell body of a neuron in the autonomic system that is located in the central nervous system, specifically the lateral horn of the spinal cord or a brain stem nucleus
    cholinergic
    synapse at which acetylcholine is released and binds to the nicotinic or muscarinic receptor
    chromaffin cells
    neuroendocrine cells of the adrenal medulla that release epinephrine and norepinephrine into the bloodstream as part of sympathetic system activity
    ciliary ganglion
    one of the terminal ganglia of the parasympathetic system, located in the posterior orbit, axons from which project to the iris
    collateral ganglia
    ganglia outside of the sympathetic chain that are targets of sympathetic preganglionic fibers, which are the celiac, inferior mesenteric, and superior mesenteric ganglia
    craniosacral system
    alternate name for the parasympathetic division of the autonomic nervous system that is based on the anatomical location of central neurons in brain-stem nuclei and the lateral horn of the sacral spinal cord; also referred to as craniosacral outflow
    dorsal longitudinal fasciculus
    major output pathway of the hypothalamus that descends through the gray matter of the brain stem and into the spinal cord
    dorsal nucleus of the vagus nerve
    location of parasympathetic neurons that project through the vagus nerve to terminal ganglia in the thoracic and abdominal cavities
    Edinger–Westphal nucleus
    location of parasympathetic neurons that project to the ciliary ganglion
    efferent branch
    component of a reflex arc that represents the output, with the target being an effector, such as muscle or glandular tissue
    endogenous
    describes substance made in the human body
    endogenous chemical
    substance produced and released within the body to interact with a receptor protein
    epinephrine
    signaling molecule released from the adrenal medulla into the bloodstream as part of the sympathetic response
    exogenous
    describes substance made outside of the human body
    exogenous chemical
    substance from a source outside the body, whether it be another organism such as a plant or from the synthetic processes of a laboratory, that binds to a transmembrane receptor protein
    fight-or-flight response
    set of responses induced by sympathetic activity that lead to either fleeing a threat or standing up to it, which in the modern world is often associated with anxious feelings
    G protein–coupled receptor
    membrane protein complex that consists of a receptor protein that binds to a signaling molecule—a G protein—that is activated by that binding and in turn activates an effector protein (enzyme) that creates a second-messenger molecule in the cytoplasm of the target cell
    ganglionic neuron
    specifically refers to the cell body of a neuron in the autonomic system that is located in a ganglion
    gray rami communicantes
    (singular = ramus communicans) unmyelinated structures that provide a short connection from a sympathetic chain ganglion to the spinal nerve that contains the postganglionic sympathetic fiber
    greater splanchnic nerve
    nerve that contains fibers of the central sympathetic neurons that do not synapse in the chain ganglia but project onto the celiac ganglion
    inferior mesenteric ganglion
    one of the collateral ganglia of the sympathetic system that projects to the digestive system
    intramural ganglia
    terminal ganglia of the parasympathetic system that are found within the walls of the target effector
    lesser splanchnic nerve
    nerve that contains fibers of the central sympathetic neurons that do not synapse in the chain ganglia but project onto the inferior mesenteric ganglion
    ligand-gated cation channel
    ion channel, such as the nicotinic receptor, that is specific to positively charged ions and opens when a molecule such as a neurotransmitter binds to it
    limbic lobe
    structures arranged around the edges of the cerebrum that are involved in memory and emotion
    long reflex
    reflex arc that includes the central nervous system
    medial forebrain bundle
    fiber pathway that extends anteriorly into the basal forebrain, passes through the hypothalamus, and extends into the brain stem and spinal cord
    mesenteric plexus
    nervous tissue within the wall of the digestive tract that contains neurons that are the targets of autonomic preganglionic fibers and that project to the smooth muscle and glandular tissues in the digestive organ
    muscarinic receptor
    type of acetylcholine receptor protein that is characterized by also binding to muscarine and is a metabotropic receptor
    mydriasis
    dilation of the pupil; typically the result of disease, trauma, or drugs
    nicotinic receptor
    type of acetylcholine receptor protein that is characterized by also binding to nicotine and is an ionotropic receptor
    norepinephrine
    signaling molecule released as a neurotransmitter by most postganglionic sympathetic fibers as part of the sympathetic response, or as a hormone into the bloodstream from the adrenal medulla
    nucleus ambiguus
    brain-stem nucleus that contains neurons that project through the vagus nerve to terminal ganglia in the thoracic cavity; specifically associated with the heart
    parasympathetic division
    division of the autonomic nervous system responsible for restful and digestive functions
    parasympathomimetic drugs
    drugs that enhance or mimic the function of the parasympathetic system
    paravertebral ganglia
    autonomic ganglia superior to the sympathetic chain ganglia
    postganglionic fiber
    axon from a ganglionic neuron in the autonomic nervous system that projects to and synapses with the target effector; sometimes referred to as a postganglionic neuron
    preganglionic fiber
    axon from a central neuron in the autonomic nervous system that projects to and synapses with a ganglionic neuron; sometimes referred to as a preganglionic neuron
    prevertebral ganglia
    autonomic ganglia that are anterior to the vertebral column and functionally related to the sympathetic chain ganglia
    referred pain
    the conscious perception of visceral sensation projected to a different region of the body, such as the left shoulder and arm pain as a sign for a heart attack
    reflex arc
    circuit of a reflex that involves a sensory input and motor output, or an afferent branch and an efferent branch, and an integrating center to connect the two branches
    rest and digest
    set of functions associated with the parasympathetic system that lead to restful actions and digestion
    short reflex
    reflex arc that does not include any components of the central nervous system
    somatic reflex
    reflex involving skeletal muscle as the effector, under the control of the somatic nervous system
    superior cervical ganglion
    one of the paravertebral ganglia of the sympathetic system that projects to the head
    superior mesenteric ganglion
    one of the collateral ganglia of the sympathetic system that projects to the digestive system
    sympathetic chain ganglia
    series of ganglia adjacent to the vertebral column that receive input from central sympathetic neurons
    sympathetic division
    division of the autonomic nervous system associated with the fight-or-flight response
    sympatholytic drug
    drug that interrupts, or “lyses,” the function of the sympathetic system
    sympathomimetic drug
    drug that enhances or mimics the function of the sympathetic system
    target effector
    organ, tissue, or gland that will respond to the control of an autonomic or somatic or endocrine signal
    terminal ganglia
    ganglia of the parasympathetic division of the autonomic system, which are located near or within the target effector, the latter also known as intramural ganglia
    thoracolumbar system
    alternate name for the sympathetic division of the autonomic nervous system that is based on the anatomical location of central neurons in the lateral horn of the thoracic and upper lumbar spinal cord
    varicosity
    structure of some autonomic connections that is not a typical synaptic end bulb, but a string of swellings along the length of a fiber that makes a network of connections with the target effector
    vasomotor nerves
    preganglionic sympathetic fibers that cause the constriction of blood vessels in response to signals from the cardiovascular center
    visceral reflex
    reflex involving an internal organ as the effector, under the control of the autonomic nervous system
    white rami communicantes
    (singular = ramus communicans) myelinated structures that provide a short connection from a sympathetic chain ganglion to the spinal nerve that contains the preganglionic sympathetic fiber
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