neuron
a nerve cell; the basic building block of the nervous system
cell body
contains nucleus, cell’s life support center
dendrites
a neurons bushy, branching extensions that receive messages and conduct impulses toward the cell body
axon
the neuron extensions that passes messages through its branches to other neurons or to muscles or glands
myelin sheath
a fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one sausage-like node to the next
glial cells (glia)
cells in the nervous system that support, nourish, and protect neurons; they may also play a role in learning and thinking
action potential
a neural impulse; a brief electrical charge that travels down an axon
threshold
the level of stimulation required to trigger a neural impulse
refractory period
a period of inactivity after a neuron has fired
all-or-none response
a neurons reaction of either firing (with a full-strength response) or not firing
synapse
the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft
neurotransmitters
chemical messengers that cross the synaptic gaps between neurons. When released by sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse
reuptake
a neurotransmitters reabsorption by the sending neuron
endorphins
“morphine within"--natural opiate-like neurotransmitters linked to pain control and to pleasure
agonist
a molecule that, by binding to a receptor site, stimulates a response
antagonist
a molecule that, by binding to a receptor site, inhibits or blocks a response
nervous system
the bodys speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous system
central nervous system (CNS)
the brain and spinal cord
peripheral nervous system (PNS)
the sensory and motor neurons that connect the central nervous system to the rest of the body
Nerves
bundled axons that from neural "cables" connecting the central nervous system with muscles, glands, and sense organs
Sensory (afferent) neurons
neurons that carry incoming information from the sensory receptors to the brain and spinal cord
motor (efferent) neurons
neurons that carry outgoing information from the brain and spinal cord to the muscles and glands
interneurons
neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs
somatic nervous system
the division of the peripheral nervous system that controls the body's skeletal muscles. also called the skeletal nervous system
autonomic nervous system (ANS)
the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). its sympathetic division arouses; its parasympathetic division calms
sympathetic nervous system
the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations
parasympathetic nervous system
the division of the autonomic nervous system that calms the body, conserving its energy
reflex
a simple, automatic response to a sensory stimulus, such as the knee-jerk response
endocrine system
chemical communication system; a set of glands that secrete hormones into the bloodstream
hormones
chemical messengers that are manufactured by the endocrine glands travel through the bloodstream and affect other tissues
adrenal glands
a pair of endocrine glands that sit just above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arous the body in times of stress
pituitary gland
the endocrine systems most influential gland. under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.
lesion
tissue destruction. a Brian lesion is a naturally or experimentally causes destruction of brain tissue
EEG (electroencephalogram)
an amplified recording of the waves of electrical activity sweeping across the brains surface. these waves are measured by electrodes placed on the scalp
MEG (magnetoencephalography)
a brain imaging technique that measures magnetic fields from the brains natural electrical activity
CT (computed tomography) scan
a series of x-ray photographs taken from different angles and combined by computer into a composite representation of a slice of the brains structure
PET (positron emission tomography) scan
a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task
MRI (magnetic resonance imagine)
a technique that use magnetic fields and radio waves to produce computer generated images of soft tissue. MRI scans show brain anatomy
fMRI (functional MRI)
a technique for revealing blood flow and, therefore, Brian activity by comparing successive MRI scans. fMRI scans show Brian function as well as its structure