Unit 2 Flashcards
Neuron
A nerve cell; the basic building block of the nervous system
Cell body
The part of a neuron that contains the nucleus; the cell’s life-support center
Dendrites
A neuron’s bushy, branching extensions that receive messages and conduct impulses toward the cell body
Axon
The neuron extension that passes messages through its branches to other neurons or to muscles or glands
Myelin sheath
A fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one node to the next
Glial cells
Cells in the nervous system that support, nourish, and protect neurons
Action potential
A neural impulse; a brief electrical charge that travels down an axon
Threshold
The level of stimulation required to trigger a neural impulse
Refractory period
The time following an action potential during which a new action potential cannot be initiated
all-or-none response
A neuron’s reaction of either firing (with a full-strength response) or not firing
Neurotransmitter
Chemical messengers that cross the synaptic gaps between neurons
Reuptake
Ena neurotransmitter ‘s reabsorption by the sending neuron
Synapse
The junction between the axon tip of the sending neurons and the dendrite or cell body of the receiving neuron
Endorphins
“Morphine within” — natural, opiatelike neurotransmitters linked to pain control and to pleasure
Agonist
A molecule that, by binding to a receptor site, stimulates a response
Antagonist
A molecule that, by binding to a receptor site, inhibits or blocks a response
nervous system
The body’s speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous system
Central nervous system
Brain and spinal cord
Peripheral nervous system
The sensory and motor neurons that connect the central nervous system to the rest of the body
Nerves
Bundled axons that form neural “cables” connecting the central nervous system with muscles, glands, and sense organs
Sensory (afferent) neurons
Neurons that carry incoming information from the sensory receptors to the brain and spinal cord
Motor (efferent) neurons
Neurons that carry outgoing information from the brain and to the muscles and glands
Interneurons
Neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs
Somatic nervous system
The division of the peripheral nervous system that controls the body’s skeletal muscles
Autonomic nervous system
The part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). It’s sympathetic division arouses; its parasympathetic division calms
