Unit 3 & 5 (Bio and State of Consciousness) Flashcards
Neuron
a nerve cell; the basic building block of the nervous system.
Afferent (sensory) neurons
neurons that carry incoming information from the sensory receptors to the brain and spinal cord.
Efferent (motor) neurons
neurons that carry outgoing information from the brain and spinal cord 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.
Dendrite
the bushy, branching extensions of a neuron that receive messages and conduct impulses toward toward the cell body.
Soma
cell body where the nucleus of the neuron is located.
Axon
the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands.
Mylein sheath
a layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.
Glial cells
cells in the nervous system that support, nourish, and protect neurons.
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 synaptic cleft.
Synaptic vesicle
the vesicle that holds neurotransmitters at the synapse, then releases them into the synaptic gap.
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.
Resting potential
when a neuron is completely polarized and not active.
Action potential
a neural impulse; a brief electrical charge that travels down the axon (depolarizes the neuron as it travels through).
Threshold
the level of stimulation required to trigger a neural impulse.
All-or-none principle
neurons will only fire at full power, either all the way or not at all.
Polarization
at resting potential a neuron is polarized. All sodium ions are on the outside of the neuron and all potassium ions are on the inside.
Depolarization
occurs when action potential travels down the axon, causing the sodium ions to rush in (a mixing of different ions) causing depolarization and the energy to fire.
Refractory period
a neuron’s resting period after firing, when it recharges and can not fire again until recharged.
Endorphins
morphine within, natural, opiatelike neurotransmitter linked to pain control and to pleasure. Gives a “runner’s high” feeling, released when injured or in pain.
Dopamine
a neurotransmitter that influences movement, learning, attention, and emotion. Some stimulant substances mimic its effects. Too much is linked to schizophrenia, too little is linked to Parkinson’s disease.
Serotonin
a neurotransmitter that affects mood, hunger, sleep, and arousal. An undersupply is linked to depression.
Acetylcholine
a neurotransmitter that enables muscle action, learning and memory. With Alzherimer’s disease, Ach-producing neurons deteriorate. Blocking of it causes paralyses.