AP Psychology Test - Chapter Three

nervous system

living tissue composed of cells

synapse

A junction where information is transmitted from one neuron to another.

synaptic cleft

A microscopic cleft, a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. The neuron that sends a signal across the gap is called the presynaptic neuron, and the neuron that receives the signal is called the postsynaptic neuron.

action potential

A very brief shift in a neuron's electrical charge that travels along an axon. Like a spark travelling down a long trail of gunpowder, the voltage change races down the axon.

absolute refractory period

After the firing of an action potential, the channels in the cell membrane that opened to let in sodium close up. Some time is needed before they are ready to open up again, and until that time the neuron cannot fire. The absolute refractory period is the minimum length of time after an action potential during which another action potential cannot begin. This "down time" isn't very long, only 1 or 2 milliseconds. It is followed by a brief relative refractory period, during which the neuron can fire, but its threshold for firing is elevated, so more intense stimulation is required to initiate an action potential.

antagonist

a chemical that opposes the action of a neurotransmitter. the key fits into the lock but it doesn't turn.

efferent nerve fibers

Axons that carry I formation outward from the central nervous system to the periphery of the body. Each body nerve contains many axons of each type. Thus, somatic nerves are "two way streets" with incoming (afferent) and outgoing (efferent) lanes. The somatic nervous system lets you feel the world and move around in it.

afferent nerve fibers

Axons that carry information inward to the central nervous system form the periphery of the body.

nerves

Bundles of neuron fibers that are routed together in the peripheral nervous system. This portion of the nervous system is just what it sounds like: the part that extends outside of the central nervous system. The peripheral nervous system can be subdivided into the somatic nervous system and the autonomic nervous system.

soma

Cell body, which contains the cell nucleus and much of the chemical machinery common to most cells. Some is Greek for body. The rest of the neuron is devoted exclusively to handling information.

glia

Cells found throughout the nervous system that provide various types of support for neurons. Glia (literally "glue") tend to be much smaller than neurons, but they outnumber neurons by about 10 to 1, so glial cells appear to account for over 50% of the brain's volume. Among other things, glial cells supply nourishment to neurons, help remove neurons' waste products, and provide insulation around many axons. The myelin sheaths that encase some axons are deprived from special types of glial cells. Glia also plays a complicated role in orchestrating the development of the nervous system in the human embryo. The unsung heroes of the nervous system. New research suggests that glia may also send and receive chemical signals.

spinal cord

Connects the brain to the rest of the body through the peripheral nervous system.

axon

From the many dendrites, information flows into the cell body and then travels away from the soma along the axon. The axon is a long, thin fiber that transmits signals away from the soma to other neurons or to the muscles or glands. Axons may be quite long (sometimes several feet) and they may branch off to communicate with a number of other cells.

neurons

Individual cells in the nervous system that receives, integrate, and transmit information. They are basic links that permit communication within the nervous system. The vast majority of them communicate only with other neurons. However, a small minority receive signals from outside the nervous system (from sensory organs) or carry messages from the nervous system to the muscles that move the body.

endorphins

Internally produce chemicals that resemble opiates in structure and effects.

autonomic nervous system

Is made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands. Is a separate system, although it is ultimately governed by the central nervous system. The autonomic nervous system controls automatic, involuntary, visceral functions that people don't normally think about, such as heart rate, digestion, and perspiration. Walter Cannon discovered the fight or flight reaction, which is closely related to the autonomic system. It can be divided into two divisions, the sympathetic and the parasympathetic.

resting potential of a neuron

Its stable, negative charge when the cell is inactive. This charge is about -70 millivolts, roughly one-twentieth of the voltage of a flashlight battery. As long as the voltage of a neuron remains constant, the cell is quiet, and no messages are being sent. When the neuron is stimulated, channels in its cell membrane open, briefly allowing positively charged sodium ions to rush in. For an instant, the neuron charge is less negative, or even positive, creating an action potential.

peripheral nervous system

Made up of all those nerves that lie outside of the brain and spinal cord.

somatic nervous system

Made up of nerves that connect to voluntary skeletal muscles and to sensory receptors. These nerves are the cables that carry information from the receptors in the skin, muscles, and joints to the central nervous system and that carry commands from the CNS to the muscles. These functions require two different kinds of nerve fibers.

myelin sheath

Many axons are wrapped in cells with a high concentration of a white, fatty substance called myelin. The myelin sheath is insulating material that encases some axons and that acts to speed up the transmission of signals that move along axons. If an axon's myelin sheath deteriorates its signals may not be translated effectively. The loss of muscle control seen with the disease multiple sclerosis is due to a degeneration of myelin sheaths.

cerebrospinal fluid

Nourishes the brain and provides a protective cushion for it. The hollow cavities in the brain that are filled with CSF are called ventricles.

the central nervous system

Portion of the nervous system that lies within the skull and spinal column. Consists of the brain and the spinal cord. It is protected by enclosing sheaths called the meninges. In addition, the central nervous system is bathed in its own special nutritive "soup," the cerebrospinal fluid.

terminal buttons

Small knobs that secret chemicals called neurotransmitters. These chemicals serve as messengers that may activate neighboring neurons.

neurotransmitters

The arrival of an action potential at an axon's terminal buttons triggers the release of neurotransmitters, which are chemicals that transmit information from one neuron to another. Within the buttons, most of these chemicals re stored in small sacs, called synaptic vesicles. The neurotransmitters are released when a vesicle fuses with the membrane of the presynaptic cell and its contents spill into the synaptic cleft. After their release, neurotransmitters diffuse across the synaptic cleft to the membrane of the receiving cell.

the sympathetic division

The branch of the autonomic nervous system that demobilizes the body's resources for emergencies. It creates the fight or flight response. Activation of the sympathetic division slows digestive processes and drains blood from the periphery, lessening bleeding in the case of an injury. Key sympathetic nerves send signals to the adrenal glands, triggering the release of hormones that ready the body for exertion.

the parasympathetic division

The branch of the autonomic nervous system that generally conserves bodily resources. It activates processes that allow the body to store and save energy. For example, actions by parasympathetic nerves slow heart rate, reduce blood pressure, and promote digestion.

post synaptic potential

When a neurotransmitter and a receptor molecule combine, reactions in the cell cause a PSP, a voltage change at the receptor site on a postsynaptic cell membrane. Postsynaptic potentials do not follow the all or none law as action potentials do. Instead, postsynaptic potentials are graded. That is, the very in size and they increase or decrease the probability of a neural impulse in the receiving cell in proportion to the amount of voltage change. Excitatory PSP and inhibitory PSP.

reputake

The excitatory or inhibitory effects produced at a synapse last only a fraction of a second. The neurotransmitters drift away from receptor sites or are inactivated by enzymes that metabolize (convert) them into inactive forms. Most are reabsorbed into the presynaptic neuron through reuptake, a process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane. Reuptake allows synapses to recycle their materials.

all or none law

The neural impulse is an all-or-none proposition, like firing a gun. You can't half-fire a gun. The same is true of the neuron's firing of action potentials. Either the neuron fires or it doesn't, and its action potentials are all the same size. That is, weaker stimuli do not produce smaller action potentials. Even though the action potential is an all-or-nothing event, neurons can convey information about the strength of a stimulus. They do so by varying the rate at which they fire action potential. In general, a stronger stimulus will cause a cell to fire a more rapid volley of neural impulses than a weaker stimulus will.

agonist

a chemical that mimics the action of a neurotransmitter

neural impulse

The neural impulse is what happens when a neuron is stimulated. Alan Hodgkin and Andrew Huxley set out to answer what this is in their groundbreaking experiments with axons removed from a squid, which they chose because of how big they are. This large size permitted Hodgkin and Hurley to insert fine wires called microelectrodes into the axons, and to record electrical activity in individual neurons, they were able to unravel the mystery of the neural impulse. They learned that the neural impulse is a complex electrochemical reaction. Both inside and outside the the neuron are fluids containing electrically charged atoms and molecules called ions. Positively charged sodium and potassium ions and negatively charged chloride ions flow back and forth across the cell membrane, but they do not cross at the same rate. The difference in flow rates leads to a slightly higher concentration of negatively charged ions inside the cell. The resulting voltage means that the neuron at rest is a tiny battery, a store of potential energy.

dendrites

The parts of a neuron that are specialized to receive information. Most neurons receive information from many other cells - sometimes thousands of others - and so have extensive dendritic trees.

cells in the nervous system categories

neurons and glia

acetylcholine

the discovery that cells communicate by releasing chemicals was first made in connection with the transmitter acetylcholine. it is the only transmitter between motor neurons and voluntary muscles. Every move you make, typing, walking, talking, breathing, epends on ACh released to your muscles by motor neurons.

monoamines

the monoamines include three neurotransmitters: dopamine, norepinephrine, and serotonin. dopamine is used by neurons that control voluntary movements. the degeneration of such neurons in a specific area is parkinsonism. serotonin releasing neurons appear to play aprominent role in the regulation of sleep and wakefulness. low norepinephrine causes depression, etc etc