5 Steps to a 5 AP Psychology 2019

84 ❯ STEP 4. Review the Knowledge You Need to Score High

nucleus, which directs synthesis of such substances as neurotransmitters. The dendrites are

branching tubular processes capable of receiving information. The axon emerges from the

cyton as a single conducting fiber (longer than a dendrite) which branches and ends in tips

called terminal buttons, axon terminals, or synaptic knobs. The axon is usually covered

by an insulating myelin sheath (formed by glial cells). Neurogenesis, the growth of new

neurons, takes place throughout life.

Neurotransmitters are chemicals stored in structures of the terminal buttons called

synaptic vesicles. Different neurotransmitters have different chemical structures and per-

form different functions. For example, acetylcholine (ACh) causes contraction of skeletal

muscles, 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 stimulates 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. Glutamate is a major excitatory neurotransmitter involved

in information processing throughout the cortex and especially memory formation in

the hippocampus. Both schizophrenia and Alzheimer’s may involve glutamate receptors.

Node of

Ranvier

Myelin sheath

Nucleus Axon

Cyton or cell body

or soma

Motor or Efferent Neuron

Sensory or Afferent Neuron

Axon terminal

or

Terminal button

or

Synaptic knob

Synaptic gap

Dendrite

terminal button

Nucleus Cell body

Terminal

button

Dendrite

Dendrite

Receptor site

Neurotransmitter

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.