Dendrites
The bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body.
Axon
The extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands.
Myelin Sheath
A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.
Action Potential
A neural impulse; a brief electrical charge that travels down an axon. Generated by the movement of positively charged atoms in and out of channels in the axon's membrane.
Synapse
The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron.
Neurotransmitters
Chemical messengers that traverse the synaptic gaps between neurons. When released by the sending neuron, they travel across the synapse and blind the receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.
Acetylcholine (Ach)
A neurotransmitter that enables learning and memory and also triggers muscle contraction. Also involved in memory, anger, and aggression.
Endorphins
"Morphin Within"-- Natural, opiatelike neurotransmitters linked to pain control and to pleasure.
Nervous System
The body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems.
Peripheral Nervous System
The sensory and motor neurons that connect the central nervous system and the rest of the body.
Nerves
Neural "cables" containing many axons. The bundled axons, which are part of the peripheral nervous system, connect the central nervous system with muscles, glands, and sense organs.
Sensory Neurons
Neurons that carry incoming information from the sense receptors to the central nervous system.
Motor Neurons
Neurons that carry outgoing information from the central nervous system to the muscles and glands.
Interneurons
Central nervous system neurons that internally communicate 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.
Autonomic Nervous System
The part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). It's sympathetic division arouses, it's parasympathetic division calms.
Sympathetic Nervous System
The division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations.
Ex: If you have a longed-for job interview, your heart rate will accelerate, raise your blood pressure, slow your digestion, and cool you with sweat, making you alert and ready for action.
Parasympathetic Nervous System
The division of the autonomic nervous system that calms your body, conserving energy.
Reflexes
A simple, automatic, inborn response to a sensory stimulus, such as the knee-jerk response.
Spinal Cord
The central nervous system's information highway connecting the peripheral nervous system to the brain.
Endocrine System
The body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream.
Agonists
A molecule may be similar enough to the neurotransmitter to mimic it's effects.
Ex: Morphine mimics the action of endorphins.
All-or-None Response
Like guns, neurons either fire or they don't.
Ex: A strong stimulus, a slap rather than a tap-can trigger more neurons to fire, and to fire more often. But, it does not effect the action potential's strength or speed.
Hormones
Chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and effect the other, including the brain.
Adrenal Glands
A pair of endocrine glands just above the kidneys. They secrete the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline), which helps to arouse the body in times of stress.
Pituitary Gland
The endocrine's system most influential gland. Regulates growth and controls other endocrine glands while under the influence of the hypothalamus; the master gland.
Electroencephalogram (EEG)
An amplified recording of the waves of electrical activity that sweep across the brain's surface. These waves are measured by electrodes placed on the scalp.
PET (Position 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 Imaging)
A technique that uses magnetic fields and radio waves to produce computer-generated images that distinguish among different types of soft-tissue; allows to see structures within the brain. (brain anatomy)
fMRI (Functional MRI)
A technique for revealing blood flow and, therefore, brain activity by comparing successive MRI scans. (brain function)
Brainstem
The oldest part and control core of the brain, beginning where the spinal cord swells as it enters the skull; responsible for automatic survival functions.
Reticular Formation
A nerve network in the brainstem that plays an important role in controlling arousal. Filters incoming stimuli and relays important information to other areas of the brain.
(A finger shaped network of neurons that extends from the spinal cord right up to the thalamus. Inside the brainstem and between the ears.)
Thalamus
The brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla.
Cerebellum
The "little brain" attached to the rear of the brainstem; its functions include processing sensory input and coordinating movement output and balance.(Organ of agility)
Limbic System
A doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres; associated with emotions such as fear and aggression and drives such as those for food and sex. Includes the hippocamus, amygdala, and hypothalamus.
Amygdala
Two lima bean sized neural clusters that are components of the limbic system and are linked to emotion; influences aggression and fear.
Hypothalamus
A neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion. Contains reward centers. Fight or flight response.
Cerebral Cortex
The intricate fabric of interconnected neural cells that covers the cerebral hemispheres; the body's ultimate control and information processing center.
Frontal Lobe
The portion of the cerebral cortex lying just being the forehead; involved in speaking and muscle movements and in making plans and judgements.
Parietal Lobe
The portion of the cerebral cortex lying at the top of the head and toward the rear; receives sensory input for touch and body position.
Occipital Lobe
The portion of the cerebral cortex lying at the back of the head; includes the visual areas which receive visual information from the opposite visual field.
Temporal Lobe
The portion of the cerebral cortex lying roughly above the ears; includes the auditory areas, each of which receives auditory information primarily from the opposite ear.
Sensory Cortex
The area at the front of the parietal lobe that registers and processes body touch and movement sensations.
Association Areas
Areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking. (3/4 of the brain)
Aphasia
Impairment of language, usually caused by left hemisphere damage either to Broca's area (impairing speaking) or to Wernicke's area (impairing understanding).
Broca's Area
Controls language expression - an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movements involved in speech.
Wernicke's Area
Controls language reception - a brain area involved in language comprehension and expression, usually in the left temporal lobe.
Plasticity
The brain's capacity for modification, as evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development.
Corpus Callosum
The large band of neural fibers connecting the two brain hemispheres and carrying messages between them.
Split Brain
A condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them.