Biological Bases of Behavior ❮ 93• Frontal lobes—interpret and control emotional behaviors, make decisions, carry out
plans; motor cortex strip just in front of somatosensory cortex initiates movements
and integrates activities of skeletal muscles; produces speech (Broca’s area).• Temporal lobes—primary area for hearing, understanding language (Wernicke’s
area), understanding music/tonality, processing smell.Aphasia—impairment of the ability to understand or use language.
Glial cells—supportive cells of the nervous system that guide the growth of developing
neurons, help provide nutrition for and get rid of wastes of neurons, and form an insulat-
ing sheath around neurons that speeds conduction.
Neuron—the basic unit of structure and function of your nervous system. Neurons
perform three major functions: receive information, process it, and transmit it to the rest
of your body. Terms relating to the structure and function of the neuron include:
• Cell body—also called the cyton or soma; the part of the neuron that con-
tains cytoplasm and the nucleus, which directs synthesis of such substances as
neurotransmitters.• Dendrites—branching tubular processes of a neuron that have receptor sites for
receiving information.• Axon—a long, single conducting fiber extending from the cell body of a neuron
that transmits an action potential and that branches and ends in tips called terminal
buttons (a.k.a. axon terminals, or synaptic knobs), which secrete neurotransmitters.• Myelin sheath—a fatty covering of the axon made by glial cells, which speeds up
conduction of the action potential.• Terminal buttons (a.k.a. axon terminals, end bulbs, or synaptic knobs)—tips at
the end of axons that secrete neurotransmitters when stimulated by the action
potential.Neurotransmitters—chemical messengers released by the terminal buttons of the
presyn aptic neuron into the synapse. Different neurotransmitters have different chemi-
cal structures and perform different tasks:
• Acetylcholine (ACh)—a neurotransmitter that causes contraction of skeletal mus-
cles, helps regulate heart muscles, is involved in memory, and also transmits messages
between the brain and spinal cord. Lack of ACh is associated with Alzheimer’s disease.• Dopamine—a neurotransmitter that stimulates the hypothalamus to synthesize hor-
mones and affects alertness, attention, and movement. Lack of dopamine is associated
with Parkinson’s disease; too much is associated with schizophrenia.• Glutamate—a neurotransmitter that stimulates cells throughout the brain, but espe-
cially in the hypothalamus, and is associated with memory formation and information
processing.• Serotonin—a neurotransmitter associated with arousal, sleep, appetite, moods, and
emotions. Lack of serotonin is associated with depression.• Endorphin—a neurotransmitter similar to the opiate morphine that relieves pain and
may induce feelings of pleasure.