Chapter 4 - The neural control of behavior

action potentials

Neural impulses; the all-or-nothing electrical bursts that begin at one end of the axon of a neuron and move along the axon to the other end.

amygdala

A brain structure that is part of the limbic system and is particularly important for evaluating the emotional and motivational significance of stimuli and generating emotional responses.

androgen

A category of hormones, including testosterone, which are produces by the testes in male animals and are normally thought of as “male hormones”. These hormones are also produces at lower levels by the adrenal glands, in females as well as in males.

aphasia

Any loss in language ability due to brain damage. See also Broca’s aphasia, Wernicke’s aphasia.

association areas

Areas of the cerebral cortex that receive input from the primary or secondary sensory areas for more than one sensory modality (such as vision and hearing) and are involved in associating this input with stored memories, in the processes of perception, thought, and decision making.

autonomic portion of the peripheral motor system

The set of motor neurons that act upon visceral muscles and glands.

axon

A thin, tube-like extension from a neuron that is specialized to carry neural impulses (action potentials) to other cells.

axon terminal

A swelling at the end of an axon that is designed to release a chemical substance (neurotransmitter) onto another neuron, muscle cell, or gland cell.

basal ganglia

The large masses of gray matter in the brain that lie on each side of the thalamus; they are especially important for the initiation and coordination of deliberate movements.

brainstem

The primitive, stalk-like portion of the brain that can be thought of as an extension of the spinal cord into the head; it consists of the medulla, pons, and midbrain.

Broca’s aphasia

A specific syndrome of loss in language ability that occurs due to dame in a particular part of the brain called Broca’s area; it is characterized by telegraphic speech in which the meaning is usually clear but the small words and word endings that serve grammatical purposes are missing; also called confluent aphasia. For contrast, see Wernicke’s aphasia.

cell body

The widest part of a neuron, which contains the cell nucleus and the other basic machinery common to all cells.

cell membrane

The thin, porous outer covering of a neuron or other cell that separates the cell’s intracellular fluid from extracellular fluid.

central nervous system

The brain and spinal cord.

cerebellum

The relatively large, conspicuous, convoluted portion of the brain attached to the rear side of the brainstem; it is especially important for the coordination of rapid movements.

cerebral cortex

The outermost, evolutionarily newest, and (in humans) by far the largest portion of the brain; it is divisible into two hemispheres (right and left), and each hemisphere is divisible into four lobes - the occipital, temporal, parietal, and frontal.

corpus callosum

A massive bundle of axons connecting the right and left hemispheres of the higher parts of the brain, including the cerebral cortex.

cranial nerves

A nerve that extends directly from the brain. See nerve. For contrast, see spinal nerve.

dendrites

The thin, tube-like extensions of a neuron that typically branch repeatedly near the neuron’s cell body and are specialized for receiving signals from other neurons.

electroencephalagram (EEG)

A record of the electrical activity of the brain that can be obtained by amplifying the weak electrical signals picked up by recording electrodes pasted to the person’s scalp. It is usually described in terms of wave patterns.

encephalization quotient (EQ)

Formula for evaluating the expected ratio between brain weight and body weight for animals.

excitatory synapse

A synapse at which the neurotransmitter increases the likelihood that an action potential will occur, or increases the rate at which they are already occurring, in the neuron on which it acts. For contrast, see inhibitory synapse.

frontal lobes

The frontmost lobes of the cerebral cortex, founded in the rear by the parietal and temporal lobes; the frontal lobes contain the motor area and parts of the association areas involved in planning and making judgments.

functional magnetic resonance imaging (fMRI)

A method for visually displaying brain activity that is based on the fact that protons in certain molecules can be made to resonate and give off radio waves indicating relative amounts of neural activity in each portion of the brain.

hippocampus

A structure in the limbic system of the brain that is essential for encoding explicit memories for long-term storage.

hormones

Any chemical substance that is secreted naturally by the body into the blood and can influence physiological processes at specific target tissues (such as the brain) and thereby influence behavior.

hypothalamus

A small brain structure lying just below the thalamus, connected directly to the pituitary gland and to the limbic system, that is especially important for the regulation of motivation, emotion, and the internal physiological conditions of the body.

inhibiroty synapse

A synapse at which the neurotransmitter decreases the likelihood that an action potential will occur, or decreases the rate at which they are already occurring, in the neuron upon which it acts. For contrast, see excitatory synapse.

interneurons

A neuron that exists entirely within the brain or spinal cord and carries messages from one set of neurons to another.

limbic system

An interconnected set of brain structures (including the amygdala and hippocampus) that form a circuit wrapped around the thalamus and basal ganglia, underneath the cerebral cortex. These structures are especially important for the regulation of emotion and motivation and are involved in the formation of long-term memories.

long-term potentiation (LTP)

A process by which repeated activation of synapses results in strengthening of those synapses.

medulla

The lowest portion of the brainstem, bounded at one end by the spinal cord and at the other by the pons. It is responsible, with the pons, for organizing reflexes more complex than spinal reflexes.

midbrain

The upper portion of the brainstem, bounded at its lower end by the pons and at its upper end by the thalamus, that contains neural centers that organize basic movement patterns.

mirror neurons

Neurons in the brain that become active both when the individual makes a particular motion and when the individual sees another individual making the same motion. These neurons are believed to facilitate observational learning.

motor neurons

A neuron that carries messages from the brain or spinal cord, through a nerve, to a muscle or gland.

myelin sheath

A casing of fatty cells wrapped tightly around the axon of some neurons.

nerve

A large bundle containing the axons of many neurons. Located in the peripheral nervous system, nerves connect the central nervous system with muscles, glands, and sensory organs.

neurogenesis

The creation of new neurons in which neuronal stem cells divide and replicate themselves by mitosis.

neurons

Single cells in the nervous system that are specialized for carrying information rapidly from one place to another and/or integrating information from various sources; also called nerve cells.

neuroscience

The research specialty that studies the brain.

neurotransmitter

A chemical substance released from the axon terminal of a neuron, at a synapse, that influences the activity of another neuron, a muscle cell, or a glandular cell; also called a transmitter.

nucleus

In neuroanatomy, a cluster of cell bodies of neurons within the central nervous system (not to be confused with the cell nucleus within each cell).

occipital lobes

A rearmost lobes of the cerebral cortex, bounded in front by the temporal and parietal lobes; they contain the visual areas of the brain.

parasympathetic division of the autonomic motor system

A set of motor neurons that act upon visceral muscles and glands and mediate many to the body’s regenerative, growth-promoting, and energy-conserving functions. For contrast, see sympathetic division of the autonomic motor system.

parietal lobes

The lobes of the cerebral cortex that lie in front of the occipital lobes, above the temporal lobes, and behind the frontal lobes; they contain the somatosensory areas of the brain.

pattern generators

Networks of neurons that stimulate one another in a cyclic manner and thereby produce bursts of action potentials that wax and wane in a regular, repeating rhythm. They help to control rhythmic sequences of muscle movements, such as those involved in walking, running, flying (in birds), or swimming (in fish).

peripheral nervous system

The entire set of cranial and spinal nerves that connect the central nervous system (brain and spinal cord) to the body’s sensory organs, muscles, and glands.

pons

The portion of the brainstems that is bounded at its lower end by the medulla and its upper end by the midbrain and is responsible, with the medulla, for organizing reflexes more complex than spinal reflexes.

positron emission tomography (PET)

A method for visually displaying brain activity that is based upon the uptake of a radioactive form of oxygen into active areas of the brain.

prefrontal cortex

The front-most portion of the frontal lobe of the brain’s cerebral cortex.

premotor areas

Portions of the brain’s cerebral cortex that lie directly anterior to (in front of) the motor area. They provide neural programs for producing organized movements.

primary motor area

An area in the rear part of the frontal lobe of the cerebral cortex that is directly involved in the control of movements, especially finely coordinated movements of small muscles, as in the fingers and vocal apparatus.

primary sensory areas

Specialized areas of the cerebral cortex that receive input from sensory nerves and tracts by way of the relay nuclei in the thalamus. They include the visual area (in the occipital lobe), auditory area (in the temporal lobe), and somatosensory area (in the parietal lobe).

resting potential

The constant electrical charge that exists across the membrane of an inactive neuron.

selective cell death (or apoptosis)

Early developmental process in which neurons die.

sensory neurons

A neuron that carries messages from a sensory organ, through a nerve, into the brain or spinal cord.

somatic portion of the peripheral motor system

Neurons that act on skeletal muscles of the peripheral motor system.

somatosensation

The set of senses that derive from the whole body - such as from the skin, muscles, and tendons - as opposed to those senses that come from the special sensory organs of the head.

spinal nerves

A nerve that extends directly from the spinal cord. For contrast, see cranial nerve.

sympathetic division of the autonomic motor system

The set of motor neurons that act upon visceral muscles and glands and mediate many of the body’s responses to stressful stimulation, preparing the body for possible “fight of flight”. For contrast, see parasympathetic division of the autonomic motor system.

synapse

The functional connection through which neural activity in the axon of one neuron influences the action of another neuron, a muscle cell, or a glandular cell.

temporal lobes

The lobes of the cerebral cortex that lie in front of the occipital lobes and below the parietal and frontal lobes and that contain the auditory areas of the brain.

thalamus

The brain structure that sits directly atop the brainstems; it functions as a sensory relay station, connecting incoming sensory tracts to special sensory areas of the cerebral cortex.

transcranial magnetic stimulation (TMS)

A procedure for temporarily altering the responsiveness of a localized area of the cerebral cortex by creating a magnetic field over that brain area. It is also used as a treatment for depression.

Wernicke’s aphasia

A specific syndrome of loss of language ability that occurs due to damage in a particular part of the brain called Wernicke’s area. Speech in a person with this disorder typically retains its grammatical structure but loses its meaning due to the speaker’s failure to provide meaningful content words (nouns, verb, adjectives, and adverbs); also called fluent aphasia. For contrast, see Broca’s aphasia.