Unit Two: Biology Flashcards
Lesion
tissue destruction; a brain lesion is a naturally or experimentally created destruction of brain tissue
Neuron
a nerve cell; the basic building block of the nervous system
Axon
the neuron extension that passes messages through its branches to other neurons or to muscles or glands
Dendrite
the fibers at the end of a cell body that receive information and conduct it toward the cell body
Myelin sheath
a layer of fatty tissue that insulates the axon and speeds its impulses
Synapse
the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron; the tiny gap at this junction is called the synaptic gap or the synaptic cleft
Action potential
a neural impulse; a brief electrical charge that travels down an axon
Refractory period
a period of inactivity after a neuron has fired
Threshold
the level of stimulation required to trigger a neural impulse
All-or-none responce
a neuron’s reaction of either firing (with a full-strength response) or not firing
Neurotransmitters
chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse
Reuptake
a neurotransmitter’s reabsorption by the sending neuron
Endorphins
“morphine within”—natural, opiate-like 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 systems
Central nervous system (CNS)
the brain and spinal cord
Peripheral nervous system (PNS)
the sensory and motor neurons that connect the central nervous system (CNS) 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 neurons
carry messages from the body’s tissues and sensory receptors inward to the brain and spinal cord for processing
Motor neurons
carry instructions from the central nervous system out to the body’s 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 (ANS)
the division of the peripheral nervous system that controls our glands and the muscles of our internal organs, influencing such functions as glandular activity, heartbeat, and digestion