AP Psychology

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between the brain and spinal cord. Lack of ACh is associated with Alzheimer’s disease.
Dopaminestimulates the hypothalamus to synthesize hormones and affects alertness and
movement. Lack of dopamine is associated with Parkinson’s disease; too much dopamine is
associated with schizophrenia. Serotoninis associated with sexual activity, concentration
and attention, moods, and emotions. Lack of serotonin is associated with depression.
Opioid peptides such as endorphinsare often considered the brain’s own pain killers.
Gamma-aminobutyric acid (GABA)inhibits firing of neurons. Benzodiazepine (Valium)
and anticonvulsant drugs increase activity of GABA. Huntington’s disease is associated with
insufficient GABA-producing neurons in parts of the brain involved in coordination of
movement. Seizures are associated with malfunctioning GABA systems.

Neuron Functions

All your behavior begins with the actions of your neurons. A neuron gets incoming infor-
mation from its receptors spread around its dendrites. That information is sent to its cell
body, where it’s combined with other incoming information. Neural impulses are electrical
in nature along the neuron. The neuron at rest is more negative inside the cell membrane
relative to outside of the membrane. The neuron’s resting potential results from the selective

Biological Bases of Behavior ❮ 71

node of

Ranvier

axon terminal

or

terminal button

or

synaptic knob

synaptic gap

synaptic vesicle with

neurotransmitters

enlargement of

terminal button of

presynaptic neuron

and membrane of

dendrite of postsynaptic

neuron at synapse

Figure 7.3 Typical neurons.

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