The nervous system comprises the central nervous
system and the peripheral nervous system.
The central nervous system consists of the brain and the spinal cord. The spinal cord connects the brain to the rest of
The peripheral nervous system consists of the somatic nervous
system and the autonomic nervous system. The somatic nervous
system affects voluntary muscles and organs. The autonomic nervous system
affects the heart, blood vessels, glands, and smooth or involuntary muscles.
The autonomic nervous system contains the sympathetic nervous
system, which prepares the body for emergency action, and the parasympathetic nervous system, which helps the body conserve
energy and relax.
Neurons: Cells of the Nervous System
Glial cells support neuron function.
Neurons, the other type of cell in the nervous system,
receive, integrate, and pass along information.
A neuron contains the soma, dendrites, axon, and myelin sheath.
Terminal buttons at the ends of axons release neurotransmitters or chemicals that cross over to neighboring
The space between neurons is the synapse.
The resting potential of a neuron is the stable negative
charge inside the neuron when it is inactive.
The action potential is a temporary change in electric charge
inside a neuron.
Neural impulses conform to the all-or-none law, which means
that neurons fire to generate an action potential only if stimulation reaches a
In neural communication, receptor sites on postsynaptic cells can be excitatory or inhibitory.
Neurotransmitters are chemicals that enable neurons to
communicate with each other.
Major neurotransmitters include acetylcholine, dopamine, serotonin, endorphins, norepinephrine, GABA, and glutamate.
Agonists are chemicals that mimic the action of
Antagonists are chemicals that block the action of
Studying the Brain
Researchers use lesioning and electric stimulation of
the brain to study animals.
To study human brains, researchers use electroencephalographs, computerized tomography, magnetic resonance imaging, and positron emission
tomography. Researchers also study the impact of brain injuries and
Structure and Functions of the Brain
The brain consists of the hindbrain, midbrain,
and forebrain. Each section of the brain contains subsections,
which control different functions.
The hindbrain contains the medulla, the pons,
and the cerebellum.
The midbrain contains a dopamine-releasing system and helps us to locate
events in space.
The forebrain is the largest part of the brain and includes the thalamus, the hypothalamus, the limbic
system, and the cerebrum.
Lateralization refers to how the right and left sides of the
brain specialize in different functions. The left hemisphere processes verbal
skills, while the right side processes nonverbal tasks.
The left side of the brain affects the functioning of the right side of
the body. Conversely, the right side of the brain affects the functioning of the
left side of the body.
The Endocrine System
The endocrine system, which consists of glands that release
hormones, also helps communication within the body.
Hormones are chemicals that regulate body functions.
The pituitary gland is the master gland of the endocrine
Major hormones include thyroxine, insulin, melatonin, adrenal hormones, androgens, estrogens, and progesterone.