3 / The Biological Bases of Behavior

Central Nervous System (CNS)

The portion of the nervous system (of neurons, axons, and supporting tissue) that includes the brain and spinal cord.

spinal cord

A part of the central nervous system (CNS) that extends from the lower end of the medulla oblongata, at the base of the brain, through the spine until near the tailbone.

spinal reflex

An automatic response controlled by neural circuits in the spinal cord. It often relates to posture or locomotion.

Peripheral Nervous System (PNS)

Basically the nervous system other than the CNS. All of the nerve cells that connect the central nervous system to all the other parts of the body.

sensory nerve

Nerves that carry signals to the brain to help convey/process touch, taste, smell, and sight.

motor nerve

Nerves that carry signals to the muscles or glands to help move and function.

somatic nervous system

A subdivision of the PNS that processes sensory information and controls voluntary muscle movements. Includes the cranial nerve and spinal nerves.

autonomous (autonomic) nervous system (ANS)

A subdivision of the PNS that controls other muscles and visceral organs. Includes the parasympathetic and sympathetic nervous systems.

sympathetic nervous system

One of the two subdivisions of the ANS that can activate the body's "flight-or-fight" response. Its activity increases when the individual is stressed, in danger, or physically active.

parasympathetic nervous system

One of the two subdivisions of the ANS that can relax the body after periods of stress or danger. It can also help with life-sustaining processes, like digestion, during times when you feel safe and relaxed.

neuron

Individual brain cells

glia

Nonneuronal tissue in the nervous system that provides structural, nutritional, and other kinds of support to neurons.

dendrite

Short nerve fibers that project form a neuron, generally receiving messages from the axons of other neurons and relaying them to the cell's nucleus.

cell body

The part of a neuron (nerve cell) that contains the nucleus and most organelles. Also called perikaryon; soma.

axon

a long, thin, and hollow single nerve fiber that transmits messages via electrochemical impulses, from the body of the neuron to dendrites of other neurons, or directly to body tissues such as muscles.

axon terminal

The very end of the exon, where electrochemical signals are passed through the synapse to neighboring cells by means of neurotransmitters and other neurochemicals. A collection of axons coming from, or going to, a specific brain area may be called a white matter fiber tract.

myelin sheath

the insulating layer around many axons that increases the speed of conduction of nerve impulses.

nodes

gaps along the myelin sheath that covers the axon of neuron cells.

nerve

A bundle of axons outside the CNS, enclosed in a sheath of connective tissue to form a cordlike structure.

neurogenesis

The growth and development of nervous tissue.

stem cells

Cells that have the potential to differentiate, to develop into many different specific cell types with specialized functions.

synaptic cleft

The space after the axon terminal of a neuron between the next target cells. Also known as the synaptic gap.

synapse

The site of transmission of electric nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell (effector)

plasticity

the brain's tendency to change and adapt as a result of new experiences and learning

action potential

a rapid sequence of changes in the voltage across a membrane.

synaptic vesicles

small, electron-lucent vesicles that are clustered at presynaptic terminals

neurotransmitter

endogenous chemicals that allow neurons to communicate with each other throughout the body

receptor sites

a region of specialized membrane on the surface of a cell (e.g. a neuron) that contains receptor molecules that receive and react with particular messenger molecules (e.g. neurotransmitters).

endorphins

Hormones produced by the brain, in response to pain or stress, to blunt the sensation of pain.

hormones

Substance secreted into the bloodstream by an endocrine gland or other tissue or organ to regulate processes in distant target organs and tissues.

endocrine glands

Any ductless gland that secretes hormones directly into the bloodstream to act on distant targets.

melatonin

n. an amine hormone, produced mainly by the pineal gland as a metabolic product of the neurotransmitter serotonin, that helps to regulate seasonal changes in physiology and may also influence puberty. Implicated in the initiation of sleep and in the regulation of the sleep-wake cycle.

adrenal hormones

Adrenal hormones help regulate several bodily functions including metabolism, blood pressure, and the body's response to stress.

cortisol

a steroid hormone produced by the adrenal glands that controls how the body uses fat, protein, carbohydrates, and minerals, and helps reduce inflammation.

epinephrine

also called adrenaline. hormone that is secreted by the adrenal glands in response to stress and other challenges to the body. The release of adrenaline causes a number of changes throughout the body, including the metabolism of carbohydrates to supply the body's energy demands and increase arousal or alertness.

norepinephrine

a catecholamine neurotransmitter and hormone produced mainly by brainstem nuclei and in the adrenal medulla. Also called noradrenaline.

lesion method

The function of a brain area is inferred by observing the deficits that are produced when the area is removed from the brain.

electrode

an instrument with a positive-pole cathode and a negative-pole anode used to stimulate biological tissues electrically or record electrical activity in these tissues. Also called bipolar electrode.

electroencephalogram (EEG)

a method that measures electrical activity in the brain using small electrodes placed on the scalp.

transcranial magnetic stimulation (TMS)

A non-invasive procedure that uses the energy from a strong magnet to stimulate changes in neural processing as well as a research method to investigate cognitive processes.

androgen

Any of a group of hormones that primarily influence the growth and development of the male reproductive system.

estrogen

A hormone that plays a role in both the male and female reproductive systems.

progesterone

A hormone that occurs naturally in the body, involved in pregnancy and produced mainly in the ovaries.

PET scan (positron-emission tomography)

An imaging technique, often used for brain imaging. For a PET scan of the brain, a radioactive "marker" that emits, or released positrons (parts of an atom that release gamma radiation) is injected into the bloodstream. Detectors outside of the head can see these "positron emissions" that are then reconstructed using sophisticated computer programs to create computer images. Areas with more blood flow and metabolism increase brain regions at work, those areas have higher concentrations of the marker, and researchers can see which brain regions activate during certain tasks or exposure to sensory stimuli. Ligands can be added to PET scans to detect pathological entities such as amyloid or tau deposits.

MRI (magnetic resonance imaging)

A non-invasive imaging technology, often used for brain imaging. An MRI scanner typically includes intensely powerful magnets, typically 10,000-40,000 times as strong as the Earth's magnetic field. These magnets, along with coils that send electromagnetic pulses into the scanned tissue, induce radio-frequency signals from individual hydrogen atoms within the tissue. The scanner records and processes these signals to create an image of the scanned tissue. Can produce high resolution images of the entire brain. Is adapted to measure brain activity with functional MRI methods.

localization of function

Refers to the theory that specific parts of the brain control specific aspects of brain function

brainstem

A primitive part of the brain that connects the brain to the spinal cord, the brain stem controls functions basic to survival, such as heart rate, breathing, digestive processes, and sleeping

pons

The portion of the brainstem between the midbrain above and the medulla oblongata below

medulla (oblongata)

The lower part of the brain stem, responsible for life-regulating functions like breathing and heart rate.

reticular activating system

A network of anatomically and physiologicaly distinct nuclei in the brainstem that function to "activate" the cerebral cortex and maintain consciousness.

cerebellum

a brain structure located at the top of the brainstem that coordinates the brain's instructions for skilled, repetitive movements and helps maintain balance and posture.

thalamus

A brain structure located at the top of the brain stem that acts as a two-way relay station, sorting, processing, and directing signals from the spinal cord and midbrain structures to the cerebrum, and from the cerebrum down.

olfactory bulb

A rounded mass of tissue that contains several types of nerve cells that are involved in the sense of smell. There are two olfactory bulbs on the bottom side of the brain, one above each nasal cavity

hypothalamus

A small structure located at the base of the brain, where signals from the brain and body's hormonal system interact.

pituitary gland

An endocrine gland at the base of the brain that is closely linked with the hypothalamus. The pituitary gland is composed of two lobes, the anterior and posterior lobes, and secretes hormones that regulate the activity of the other endocrine organs in the body.

limbic system

A group of evolutionarily older brain structures that encircle the top of the brain stem. The limbic structures play complex roles in emotions, instincts, and appetitive behaviors.

amygdala

A primitive brain structure lying deep in the center of the brain, involved in emotional reactions, such as anger or fear, as well as emotionally charged memories.

hippocampus

A primitive brain structure, located deep in the brain, that is critical for memory and learning

cerebrum

The largest part of the brain is associated with white matter. Usually refers to the cerebral cortex, but some texts include the subcortical structures.

cerebral hemispheres

One of the two symmetrical halves of the brain.

corpus callosum

The collection of nerve fibers connecting the two cerebral hemispheres.

lateralization

a functional dominance of one hemisphere over the other, in which one is more responsible or entirely responsible for control of a function in comparison to the other.

cerebral cortex

The outer layer of the cerebrum.

occipital lobes

A brain lobe located at the back of the cerebral cortex, the house of the visual area of the brain.

visual cortex

The primary cortical region of the brain that receives, integrates, and processes visual information relayed from the retinas (eyes).

parietal lobes

A brain lobe located at the upper back of the cerebral cortex, where touch and taste are processed.

somatosensory cortex

The region of "neocortex" specialized to represent and process touch, which includes light touch and proprioception, as well as temperature and pain.

temporal lobes

A brain lobe located on the underside of the cerebral cortex, where sounds and smells are processed.

auditory cortex

The sensory area for hearing, located on the upper side of the temporal lobe of the cerebral cortex

Wernicke's area

Located in Brodmann area 22, the posterior segment of the superior temporal gyrus in the dominant hemisphere.

frontal lobes

A brain lobe located at the forward part of the cerebral cortex is where behavioral motor plans are processed as well as a number of highly complicated processes occur including speech and language use, creative problem solving, and planning and organization.

motor cortex

The region of the frontal lobe of the brain responsible for the control of voluntary movement. It is divided into two parts.

Broca's area

An area in the frontal lobe of the left hemisphere. It is implicated in language production/linguistics.

association cortex

any of various areas of the cerebral cortex that are not involved principally in sensory or motor representations but may be involved in integrative functions. Also called association area.

split-brain surgery

A type of survey to treat seizures when antiseizure medications don't help. Splits the corpus callosum.

hemispheric dominance

The tendency for either the left or the right side of the brain to carry out specific brain activities.