Unit 3 A: The Neuron

biological psychology

a branch of psychology concerned with the links between biology and behavior

agonists

a drug that is similar enough in structure to a neurotransmitter molecule to mimic its effects (e.g., morphine mimics the action of endorphins)

Resting potential

State in which a neuron is NOT transmitting a nerve impulse. A neuron in this state has a net negative charge relative to its outside environment, and this state of potential energy prepares it to be activated by an impulse from an adjacent neuron.

antagonists

a drug that is similar enough in structure to a neurotransmitter to occupy its receptor site and block its action, but not similar enough to stimulate the receptor (e.g., the poison called curare paralyzes its victims by blocking the receptor sites for Ach)

myelin 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

glutamate

a major excitatory neurotransmitters: involved in memory. Oversupply can overstimulate brain,producing migraines or seizures (which is why some people avoid MSG (monosodium glutamate) in food

GABA (gamma-aminobutyric acid)

a major inhibitory neurotransmitter; an undersupply linked to seizures, tremors, anxiety and insomnia

neuron

a nerve cell; the basic building block of the nervous system

action potential

a neural impulse; a brief electrical charge that travels down an axon

dopamine

a neurotransmitter associated with movement, attention and learning and the brain's pleasure and reward system; excess activity of this neurotransmitter is linked to schizophrenia, and the lack of it is related to the decreased mobility and tremors of Parkinson's disease

serotonin

a neurotransmitter that affects hunger, sleep, arousal, and mood; it appears in lower than normal levels in depressed persons

reuptake

a neurotransmitter's reabsorption by the sending neuron

neurotransmitters

chemical messengers that traverse the synaptic gaps between neurons. When released by the sending neuron, they travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.

acetylcholine (Ach)

enables muscle action, learning, and memory; with Alzheimer's disease, the neurons that produce it deteriorate

norepinephrine

helps control alertness and arousal; an undersupply can depress mood; while an oversupply can lead to mania

endorphins

natural, opiatelike neurotransmitters linked to pain control and to pleasure

motor neurons

neurons that carry outgoing information from the central nervous system to the muscles and glands; also known as efferent neurons

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 the cell body

axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

threshold

the level of stimulation required to trigger a neural impulse

cell body

the neuron's life-support center; also known as the soma

sensory neurons

type of neuron that carries INCOMING MESSAGES FROM THE SENSORY RECEPTORS (found in the eyes, ears, skin, etc.) to the brain or the spinal cord; known also as afferent neurons