The Brain

Biological psychology- a branch of psychology concerned with the links between biology and behavior

Neuron- a nerve cell; the basic building block of the nervous system

Dendrite- 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. The action potential is generated by the movement of positively charged atoms in and out of the channels in the axon's membrane

Threshold- a level of stimulation required to trigger a neural impulse

Synapse- the junction between the axon tip of the sending neuron and the dendrite and cell body of the receiving neuron. The tin gap at this junction is called the synaptic gap or cleft

Neurotransmitters- 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.

Acetylcholine (Ach) - a neurotransmitter that, among its functions, triggers muscle contraction

Endorphins- "morphine within"- natural, opiate like neurotransmitters linked to pain control and pleasure

Nervous system- the body's speedy, electrochemical communication system, consisting of all the nerve cells of the peripheral and central nervous systems.

Central nervous system (CNS) - the brain and the spinal cord

Peripheral nervous system (PNS) - the sensory and motor neurons that connect the central nervous system to the rest of the body

Nerves- 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.

Sensory neurons- neurons that carry incoming information from the sense receptors to the central nervous system

Interneuron- central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs

Motor neurons- neurons that carry outgoing information from the central nervous system to the muscles and glands.

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

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, inborn response to a sensory stimulus, such as the knee-jerk response

Neural Networks- interconnected neural cells. With experience, networks learn, as a feedback strengthens or inhibits connections that produce certain results. Computer simulations of neural networks show analogous learning

Lesion- tissue destruction. A brain lesion is a naturally or experimentally caused destruction of brain tissue.

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 of the scalp

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 through the body (CAT scan).

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 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

Brainstem- the oldest part of the central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions.

Medulla- the base of the brainstem; controls heartbeat and breathing

Reticular formation- a nerve network in the brainstem that plays an important role in controlling arousal

Thalamus- the brain's sensory switchboard, located on top of the brainstem. It directs messages to 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; it helps coordinate voluntary movement and balance.

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 hippocampus, amygdala, and hypothalamus.

Amygdala- two almond-shaped neural clusters that are components of the limbic system and are linked to emotion.

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

Cerebral cortex- the intricate fabric of interconnected neural cells that covers the cerebral hemispheres; the body's ultimate control and information-processing center.

Glial cells- cells in the nervous system that support, nourish, and protect neurons.

Fontal lobes- the portion of the cerebral cortex lying just behind the forehead; invo9lved in speaking and making muscle movements and in making plans and judgments.

Parietal lobes- the