The bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body.
The extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles and glands.
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.
A neural impulse; a brief electrical charge that travels down an axon. The action potential is generated by the movement of positively charged atoms in and out of channels in the axon's membrane.
the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron
chemical messengers that traverse the synaptic gaps between neurons. When released by the 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.
a neurotransmitter that enables learning and memory and also triggers muscle contraction
"morphine within"--natural, opiatelike neurotransmitters linked to pain control and to pleasure.
The body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems.
Peripheral Nervous System (PNS)
the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.
neural "cables" containing many axons. These bundled axons, which are part of the peripheral nervous system, connect the central nervous system with muscles, glands, and sense organs.
neurons that carry incoming information from the sense receptors to the central nervous system.
neurons that carry outgoing information from the central nervous system to the muscles and glands.
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. Also called the skeletal nervous system.
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). 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.
Interconnected neural cells. With experience, networks can learn, as feedback strengthens or inhibits connections that produce certain results. Computer simulations of neural networks show analogous learning.
the body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream.
chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another.
a pair of endocrine glands just above the kidneys. the adrenals secrete the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline), which help to arouse the body in times of stress.
the endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.
tissue destruction. A brain lesion is a naturally or experimentally caused destruction of brain tissue.
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 (positron emission tomography)
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 us to see structures within the brain.
a technique for revealing blood flow and, therefore, brain activity by comparing successive MRI scans. MRI scans show brain anatomy; fMRI scans show brain function.
The oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions
a nerve network in the brainstem that plays an important role in controlling arousal.
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
the "little brain" attached to the rear of the brainstem; its functions include processing sensory input and coordinating movement output and balance
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 hippocampus, amygdala, and hypothalamus.
two lima bean-sized neural clusters that are components of the limbic system and are linked to emotion
a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion
the intricate fabric of interconnected neural cells that covers the cerebral hemispheres; the body's ultimate control and information-processing center.