Chapter 12: The Nervous System and Nervous Tissue

**neurotransmitter**

When this signal reaches the end bulbs, it causes the release of a signaling molecule called a

**nonspecific channel**

Some ion channels are selective for charge but not necessarily for size, and thus are called a

**voltage-gated channel**

is a channel that responds to changes in the electrical properties of the membrane in which it is embedded.

**leakage channel**

is randomly gated, meaning that it opens and closes at random, hence the reference to leaking.

**Repolarization**

meaning that the membrane voltage moves back toward the -70 mV value of the resting membrane potential.

**postsynaptic potential (PSP)**

is the graded potential in the dendrites of a neuron that is receiving synapses from other cells.

**Spatial summation**

is related to associating the activity of multiple inputs to a neuron with each other.

**chemical synapse**

a chemical signal—namely, a neurotransmitter—is released from one cell and it affects the other cell.

**electrical synapse**

there is a direct connection between the two cells so that ions can pass directly from one cell to the next.

**biogenic amine**

a group of neurotransmitters that are enzymatically made from amino acids.

**neuropeptide**

is a neurotransmitter molecule made up of chains of amino acids connected by peptide bonds.

**metabotropic receptor**

involves a complex of proteins that result in metabolic changes within the cell.

**effector protein**

is an enzyme that catalyzes the generation of a new molecule, which acts as the intracellular mediator of the signal.

**Temporal summation**

is the relationship of multiple action potentials from a single cell resulting in a significant change in the membrane potential.

**mechanically gated channel**

opens because of a physical distortion of the cell membrane.

**ligand-gated channel**

opens because a signaling molecule, a ligand, binds to the extracellular region of the channel.

**electrochemical exclusion**

meaning that the channel pore is charge-specific.

**precentral gyrus of the frontal cortex**

which has an axon that extends all the way down the spinal cord.

**thermoreceptor**

Found in the skin of your fingers or toes is a type of sensory receptor that is sensitive to temperature, called a

**action potential**

resulting electrical signal is called an

**propagation**

The action potential travels—a process known as

**threshold**

The voltage at which such a signal is generated is called the

 **graded potential**

The amount of change is dependent on the strength of the stimulus (how hot the water is).

**Schwann cell**

which insulate axons with myelin in the periphery.

**satellite cell**

One of the two types of glial cells found in the PNS is the

**choroid plexus**

is a specialized structure in the ventricles where ependymal cells come in contact with blood vessels and filter and absorbcomponents of the blood to produce cerebrospinal fluid.

**white matter**

(the regions with many axons).

**ganglion**

In the PNS, a cluster of neuron cell bodies is referred to as a

**tract**

A bundle of axons, or fibers, found in the CNS is called a

**initial segment**

Because the axon hillock represents the beginning of the axon, it is also referred to as the

**Microglia**

as the name implies, smaller than most of the other glial cells.

**oligodendrocyte**

sometimes called just “oligo,” which is the glial cell type that insulates axons in the CNS.

**pia mater**

Those processes extend to interact with neurons, blood vessels, or the connective tissue covering the CNS that is called the

**Multipolar**

neurons are all of the neurons that are not unipolar or bipolar.

**Bipolar**

cells have two processes, which extend from each end of the cell body, opposite to each other.

**Unipolar**

cells have only one process emerging from the cell.

**axon segment**

The length of the axon between each gap, which is wrapped in myelin, is referred to as an

**axoplasm**

Within the axon hillock, the cytoplasm changes to a solution of limited components called

**axon hillock**

Where the axon emerges from the cell body, there is a special region referred to as the

**synapses**

The other processes of the neuron are dendrites, which receive information from other neurons at specialized areas of contact called

**enteric nervous system** (ENS)

is responsible for controlling the smooth muscle and glandular tissue in your digestive system.

**autonomic nervous system (ANS)**

is responsible for involuntary control of the body, usually for the sake of homeostasis (regulation of the internal environment).

**somatic nervous system (SNS**)

is responsible for conscious perception and voluntary motor responses.

**stimulus**

The sensory functions of the nervous system register the presence of a change from homeostasis or a particular event in the environment, known as a

**nucleus**

A localized collection of neuron cell bodies in the CNS is referred to as a

**myelin**

But white matter is white because axons are insulated by a lipid-rich substance called

**Dendrites**

are responsible for receiving most of the input from other neurons.

**central nervous system (CNS)**

is the brain and spinal cord

**peripheral nervous system (PNS)**

is everything else.

**glial cell**

is one of a variety of cells that provide a framework of tissue that supports the neurons and their activities.

**axon**

There is one important process that every neuron has called an

**ependymal cell**

is a glial cell that filters blood to make cerebrospinal fluid (CSF), the fluid that circulates through the CNS.