Chapter 35 Flashcards
A network of many interconnected nerve cells.
nervous system
Nerve cell; the basic fundamental unit of nervous systems.
neuron
A neuron that receives and transmits information about an animal’s environment or its internal physiological state.
sensory neurons
A neuron that processes information received by sensory neurons and transmits it to motor neurons in different body regions.
interneuron
A neuron that, on receiving information from interneurons, effects a response in the body.
motor neuron
The active regulation and maintenance, in animals, organs, or cells, of a stable internal physiological state in the face of a changing external environment.
homeostasis
A group of nerve cell bodies that processes sensory information received from a local, nearby region, resulting in a signal to motor neurons that control some physiological function of the animal.
ganglion
The centralized concentration of neurons in an organ that processes complex sensory stimuli from the environment or from anywhere in the body.
brain
A bundle of long fiberlike extensions from multiple nerve cells that serves as the central nervous system of invertebrates such as flatworms and earthworms.
nerve cord
A bundle of long fiberlike extensions from multiple nerve cells.
nerves
The concentration of nervous system components at one end of the body.
cephalization
A fiberlike extension from the cell body of a neuron that receives signals from other nerve cells or from specialized sensory endings; the input end of a nerve cell.
dendrite
The fiberlike extension from the cell body of a neuron that transmits signals away from the nerve’s cell body; the output end of a nerve cell.
axon
The junction of the nerve cell body and its axon.
axon hillock
A brief electrical signal transmitted from the nerve cell body along one or more axon branches.
action potential
A junction through which the axon terminal communicates with a neighboring cell.
synapse
The space between the axon of the presynaptic cell and the neighboring postsynaptic cell.
synaptic cleft
A molecule that conveys a signal from the end of the axon to the postsynaptic target cell.
neurotransmitter
A type of cell that surrounds neurons and provides them with nutrition and physical support.
glial cell
A type of star-shaped glial cell that contributes to the blood–brain barrier by surrounding blood vessels in the brain and thus limiting the size of compounds that can diffuse from the blood into the brain.
astrocyte
A difference in electrical charge across the plasma membrane.
membrane potential
Having opposite properties in opposite parts; describes a resting membrane potential in which there is a buildup of negatively charged ions on the inside surface of the cell’s plasma membrane and positively charged ions on its outer surface.
polarized
The negative voltage across the membrane at rest.
resting membrane potential
An increase in membrane potential
depolarization
Ion membrane channels that open and close in response to changes in membrane potential.
voltage-gated channels
The critical depolarization voltage of –50 mV required for an action potential.
threshold potential
In the nervous system, the type of feedback in which a stimulus causes a response that leads to an enhancement of the original stimulus that leads to a larger response. In the endocrine system, the type of feedback in which a stimulus causes a response, and that response causes a further response in the same direction. In both cases, the process reinforces itself until interrupted.
postive feedback
The period following an action potential during which the inner membrane voltage falls below and then returns to the resting potential.
refractory period
Continuing without input from an outside source; action potentials are self-propagating in that they move along axons by sequentially opening and closing adjacent ion channels.
self-propagating
Lipid-rich layers or sheaths formed by glial cells that wrap around the axons of vertebrate neurons and provide electrical insulation.
myelin
Sites on an axon that lie between adjacent myelin-wrapped segments, where the axon membrane is exposed.
nodes of Ranvier
The movement of an action potential along a myelinated axon, “jumping” from node to node.
saltatory propagation
A receptor that alters the flow of ions across the plasma membrane when bound by its ligand.
ligand-gated ion channel
A positive change in the postsynaptic membrane potential.
excitatory postsynaptic potential (EPSP)
A negative change in the postsynaptic membrane potential.
inhibitory postsynaptic potential (IPSP)
The frequency of synaptic stimuli; the integration of sensory stimuli that are received repeatedly over time by the same sensory cell.
temporal summation
The converging of multiple receptors onto a neighboring neuron, increasing its firing rate proportionally to the number of signals received.
spatial summation
Collectively, the sensory and motor nerves, including the cranial and spinal nerves, and interneurons and ganglia.
peripheral nervous system (PNS)
In vertebrates, the brain and spinal cord; in invertebrates, centralized information-processing ganglia.
central nervous system (CNS)
In vertebrates, a central tract of neurons that passes through the vertebrae to transmit information between the brain and the periphery of the body.
spinal cord
In vertebrates, a nerve that links specialized sensory organs to the brain; most contain axons of both sensory and motor neurons.
cranial nerve
In vertebrates, a nerve running from the spinal cord to the periphery containing axons of both sensory and motor neurons.
spinal nerve
Describes the component of the nervous system that handles sensing and responding to external stimuli.
voluntary
Describes the component of the nervous system that regulates internal bodily functions.
involuntary
The voluntary component of the peripheral nervous system, which is made up of sensory neurons that respond to external stimuli and motor neurons that synapse with voluntary muscles.
somatic nervous system
The involuntary component of the peripheral nervous system, which controls internal functions of the body such as heart rate, blood flow, digestion, excretion, and temperature.
autonomic nervous system
The division of the autonomic nervous system that generally produces arousal and increased activity; active in the fight-or-flight response.
sympathetic division
The division of the autonomic nervous system that slows the heart and stimulates digestion and metabolic processes that store energy, enabling the body to “rest and digest.”
parasympathetic division
Describes the effect in which the final product of a biochemical pathway inhibits the first step; the process in which a stimulus acts on a sensor that communicates with an effector, producing a response that opposes the initial stimulus. Negative feedback is used to maintain steady conditions, or homeostasis.
negative feedback
A reflex commonly tested by physicians to evaluate peripheral nervous and muscular system function.
knee-jerk extension reflex