BIO100 Chptr 10 Nervous System I Basic Structure and Function

Question 1

astr-

Answer 1

astr-, starlike:

astrocyte—star-shaped neuroglia.

Question 2

ax-, axle

Answer 2

ax-, axle: axon—

cylindrical process that conducts impulses away from a neuron cell body.

Question 3

bi-

Answer 3

bi-, two: bipolar neuron

—neuron with two processes extending from the cell body.

Question 4

dendr-

Answer 4

dendr-, tree: dendrite

—branched process that serves as the receptor surface of a neuron.

Question 5

ependym-

Answer 5

ependym-, tunic: ependyma

—neuroglia that line spaces in the brain and spinal cord.

Question 6

-lemm

Answer 6

-lemm, rind or peel: neurilemma

—sheath that surrounds the myelin of a nerve cell process.

Question 7

moto-

Answer 7

moto-, moving: motor neuron

—neuron that stimulates a muscle to contract or a gland to release a secretion.

Question 8

multi-

Answer 8

multi-, many: multipolar neuron

—neuron with many processes extending from the cell body.

Question 9

oligo-

Answer 9

oligo-, few: oligodendrocyte

—small type of neuroglia with few cellular processes.

Question 10

peri-

Answer 10

peri-, all around: peripheral nervous system PNS

—portion of the nervous system that consists of the nerves branching from the brain and spinal cord.

Question 11

saltator-

Answer 11

saltator-, a dancer: saltatory conduction

—impulse conduction in which the impulse seems to jump from node to node along the axon.

Question 12

sens-

Answer 12

sens-, feeling: sensory neuron

—neuron that can be stimulated by a sensory receptor and conducts impulses into the brain or spinal cord.

Question 13

syn-

Answer 13

syn-, together: synapse

—junction between two neurons.

Question 14

uni-

Answer 14

uni-, one: unipolar

—neuron with only one process extending from the cell body.

Question 15

Neural tissue consists of two cell types:

Answer 15

nerve cells, or neurons (nu′ronz), and neuroglia (nu-ro′gle-ah) (or neuroglial cells).

Question 16

dendrites

Answer 16

Small cellular processes - receive the input

Question 17

axon

Answer 17

A longer process - or nerve fiber, carries the information away from the cell in the form of bioelectric signals, called impulses (action potentials) which allow the neuron to communicate with other neurons and with cells outside the nervous system

Question 18

Neuroglia

Answer 18

These cells that form myelin, protect, support, and maintain equilibrium in your nervous system are called glial cells. They are also commonly known as neuroglia and even more simply glia. In more detailed terms, neuroglia are cells in your nervous system that are not neurons.

Question 19

astrocytes

Answer 19

a star-shaped glial cell of the central nervous system.

Question 20

synapse

Answer 20

a junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.

Question 21

synaptic cleft

Answer 21

is a space that separates two neurons. It forms a junction between two or more neurons and helps nerve impulse pass from one neuron to the other.

Question 22

neurotransmitters

Answer 22

Biological messenger molecules called neurotransmitters (nu″ro-transmit′erz) convey this neural information.

Question 23

central nervous system (CNS)

Answer 23

consisting of the brain and spinal cord

one of two nervous systems-

Question 24

peripheral nervous system (PNS)

Answer 24

includes the nerves (cranial and spinal nerves) that connect the central nervous system to other body parts. The PNS also includes ganglia, which are clusters of neuron cell bodies located outside the brain and spinal cord.

one of two nervous systems-

Question 25

The three general functions of the nervous system

Answer 25

receiving information, deciding what to do, and acting on those decisions—are termed sensory, integrative, and motor.

Question 26

sensory receptors

Answer 26

at the ends of neurons in the peripheral nervous system (peripheral neurons) provide the sensory function of the nervous system (Receptors, Sensation, and Perception). These receptors gather information by detecting changes inside and outside the body. They monitor external environmental factors such as light and sound intensities as well as the temperature, oxygen concentration, and other conditions of the body’s internal environment.

Question 27

somatic nervous system

Answer 27

communicates voluntary (conscious) instructions originating in the CNS to skeletal muscles, causing contraction

Question 28

autonomic nervous system

Answer 28

communicates instructions from the CNS that control viscera, such as the heart and various glands, and thus causes involuntary, subconscious actions. Typically these responses counteract the effects of the changes detected. In this way, the nervous system helps maintain homeostasis.

Question 29

Every neuron has a cell body

Answer 29

Neurons vary in size and shape. They may differ in the lengths and sizes of their axons and dendrites and in the number of processes. Despite this variability, neurons share certain features. Every neuron has a cell body, dendrites, and an axon.

Question 30

A neuron’s cell body (soma or perikaryon)

Answer 30

contains granular cytoplasm, mitochondria, lysosomes, a Golgi apparatus, and many microtubules. A network of fine threads called neurofilaments extends into the axon and supports it.

Question 31

chromatophilic substance (Nissl bodies)

Answer 31

The cell body (soma or perikaryon) contains the nucleus and other cell organelles. There are clusters of rough endoplasmic reticulum (not shown in Figure 1) that are called Nissl bodies or are sometimes referred to as chromatophilic substances.

Question 32

axon hillock.

Answer 32

A neuron may have many dendrites, but no more than one axon. In most neurons the axon arises from the cell body as a cone-shaped thickening called the axon hillock.

Question 33

collaterals

Answer 33

The axon may give off branches, called collaterals.

Question 34

axon terminal

Answer 34

Near its end, an axon may have many fine extensions, each with a specialized ending called an axon terminal. The axon terminal ends as a synaptic knob close to the receptive surface of another cell, separated only by a space called the synaptic cleft.

Question 35

synaptic knob

Answer 35

A synaptic knob is one of many terminal endpoints on a neuron’s axon. While nerve cells generally only have one axon, they can have many terminal.

Question 36

axonal transport

Answer 36

also called axoplasmic transport or axoplasmic flow, is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other organelles to and from a neurons cell body, through the cytoplasm of its axon called the axoplasm.

Question 37

Schwann cells

Answer 37

also called neurilemma cell, any of the cells in the peripheral nervous system that produce the myelin sheath around neuronal axons (In the PNS)

Question 38

myelin sheath

Answer 38

Myelin is an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. This myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells.

Question 39

neurilemma

Answer 39

the thin sheath around a nerve axon (including myelin where this is present).

Question 40

nodes of Ranvier

Answer 40

Narrow gaps in the myelin sheath between Schwann cells

Question 41

oligodendrocyte

Answer 41

are a type of neuroglia whose main functions are to provide support and insulation to axons in the central nervous system of some vertebrates, equivalent to the function performed by Schwann cells in the peripheral nervous system.

Question 42

Gray nerves - Why?

Answer 42

Unmyelinated nerve tissue appears gray. Thus, the gray matter in the CNS contains many unmyelinated axons and neuron cell bodies.

Question 43

White-colored appearing nerves?

Answer 43

Groups of myelinated axons appear white. The white matter in the brain and spinal cord gets its color from masses of myelinated axons.

Question 44

multipolar neuron

Answer 44

has many processes arising from its cell body.

Only one is an axon; the rest are dendrites.

Question 45

bipolar neuron

Answer 45

The cell body of a bipolar neuron has only two processes, one arising from either end. Although these processes are similar in structure, one is an axon and the other is a dendrite. Bipolar neurons are found in specialized parts of the eyes, nose, and ears.

Question 46

unipolar neuron

Answer 46

has a single process extending from its cell body. (These are also called pseudounipolar, because they start out with two processes that merge into one during development.) A short distance from the cell body, this process divides into two branches, which really function as a single axon: One branch (peripheral process) has dendrites near a peripheral body part. The other branch (central process) enters the brain or spinal cord. The cell bodies of most unipolar neurons are found in ganglia.

Question 47

Sensory neurons (afferent neurons)

Answer 47

conduct impulses from peripheral body parts into the brain or spinal cord. At their distal ends, the dendrites of these neurons or specialized structures associated with them act as sensory receptors, detecting changes in the outside world

Question 48

Interneurons (also called association or internuncial neurons)

Answer 48

lie within the brain or spinal cord. They are multipolar and form links with other neurons. Interneurons relay information from one part of the brain or spinal cord to another. That is, they may conduct incoming sensory information to appropriate regions for processing and interpreting. Other instructions are transferred to motor neurons. The cell bodies of some interneurons aggregate in specialized masses of nervous tissue called nuclei (singular, nucleus). Nuclei are similar to ganglia, but are within the CNS.

Question 49

Motor neurons (efferent neurons)

Answer 49

are multipolar and conduct impulses out of the brain or spinal cord to effectors. For example, when motor neurons stimulate muscle cells, the muscle cells contract; when motor neurons stimulate glands, the glands release secretions.

Question 50

four types of CNS neuroglia

Answer 50

astrocytes, oligodendrocytes, microglia, and ependyma

Question 51

Microglia

Answer 51

it is known that these cells mediate immune responses in the central nervous system by acting as macrophages, clearing cellular debris and dead neurons from nervous tissue through the process of phagocytosis (cell eating).

Question 52

Ependyma

Answer 52

The functions of the ependymal cells is as follows: 1) they give rise to the epithelial layer surrounding the choroid plexus in the lateral ventricles of the cerebral hemisphere. These epithelial cells mainly produce cerebro - spinal fluid. 2) the ependymal cells have cilia , facing the cavity of the ventricles.

Question 53

Neuroglia and Axonal Regeneration (summarized)

Answer 53

Neuroregeneration refers to the regrowth or repair of nervous tissues, cells or cell products. Such mechanisms may include generation of new neurons, glia, axons, myelin, or synapses. … When an axon is damaged, the distal segment undergoes Wallerian degeneration, losing its myelin sheath.

Question 54

synaptic vesicles

Answer 54

or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the cell.

Question 55

neurotransmitter binds to receptors

Answer 55

Once the neurotransmitter binds to receptors on a postsynaptic cell, the action is either excitatory (turning a process on) or inhibitory (turning a process off).

Question 56

inhibitory

Answer 56

slowing down or preventing a process, reaction, or function.

Question 57

excitatory

Answer 57

characterized by, causing, or constituting excitation.

Question 58

cell depolarization

Answer 58

is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell.

*peak -40v

Question 59

cell hyperpolarization

Answer 59

s a change in a cell’s membrane potential that makes it more negative. It is the opposite of a depolarization. It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold.

-70mv

Question 60

Ligand-gated Ion Channel

Answer 60

Ligand-gated ion channels bind neurotransmitters and open in response to ligand binding. These channels control synaptic transmission between two neurons or between a neuron and a muscle.

Question 61

Under resting conditions, non-gated (always open) channels

Answer 61

determine the membrane permeability to sodium and potassium ions.
A resting nerve cell is not being stimulated to send an impulse
The resting cell membrane is much more permeable to potassium ions than to sodium ions - Calcium ions are less able to cross the resting cell membrane

Question 62

membrane potential

Answer 62

The difference in electrical charge between two points is measured in units called volts. It is called a potential difference because it represents stored electrical energy that can be used to do work at some future time. The potential difference across the cell membrane is called the membrane potential (transmembrane potential) and is measured in millivolts (mV).

Question 63

threshold potential

Answer 63

is the critical level to which a membrane potential must be depolarized to initiate an action potential. In neuroscience, threshold potentials are necessary to regulate and propagate signaling in both the central nervous system (CNS) and the peripheral nervous system (PNS).

Question 64

Events Leading to Impulse Conduction

Answer 64

Nerve cell membrane maintains resting potential by diffusion of Na+ and K+ down their concentration gradients as the cell pumps them up the gradients.
Neurons receive stimulation, causing local potential changes, which may sum to reach threshold.
If threshold is reached, sodium channels in the trigger zone of the axon open.
Sodium ions diffuse inward, depolarizing the membrane.
Potassium channels in the membrane open.
Potassium ions diffuse outward, repolarizing the membrane.
The resulting action potential causes an electric current that stimulates adjacent portions of the membrane.
The action potential propagates along the length of the axon.

Question 65

refractory period

Answer 65

a period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation.

Question 66

saltatory conduction

Answer 66

is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

Question 67

synaptic potentials

Answer 67

refers to the potential difference across the postsynaptic membrane that results from the action of neurotransmitters at a neuronal synapse. In other words, it is the “incoming” signal that a neuron receives. There are two forms of synaptic potential: excitatory and inhibitory.

Question 68

acetylcholinesterase

Answer 68

also known as AChE or acetylhydrolase, is the primary cholinesterase in the body. It is an enzyme that catalyzes the breakdown of acetylcholine and of some other choline esters that function as neurotransmitters.

Question 69

reuptake

Answer 69

Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal or glial cell after it has performed its function of transmitting a neural impulse.

Question 70

monoamine oxidase

Answer 70

Monoamine oxidases are a family of enzymes that catalyze the oxidation of monoamines, employing oxygen to clip off their amine group. They are found bound to the outer membrane of mitochondria in most cell types of the body.

Question 71

neuropeptides

Answer 71

any of a group of compounds which act as neurotransmitters and are short-chain polypeptides.

Question 72

Events Leading to Neurotransmitter Release

Answer 72

Action potential passes along an axon and over the surface of its synaptic knob.
Synaptic knob membrane becomes more permeable to calcium ions, and they diffuse inward.
In the presence of calcium ions, synaptic vesicles fuse to synaptic knob membrane.
Synaptic vesicles release their neurotransmitter by exocytosis into the synaptic cleft.
Synaptic vesicle membrane becomes part of the cell membrane.
The added membrane provides material for endocytotic vesicles.

Question 73

enkephalins

Answer 73

either of two compounds that occur naturally in the brain. They are peptides related to the endorphins, with similar physiological effects.
The enkephalins are termed endogenous ligands, as they are internally derived and bind to the body’s opioid receptors.

Question 74

Substance P

Answer 74

Substance P (SP) is an undecapeptide (a peptide composed of a chain of 11 amino acid residues) member of the tachykinin neuropeptide family. It is a neuropeptide, acting as a neurotransmitter and as a neuromodulator.

Question 75

neuronal pools

Answer 75

functional groups of neurons that integrate incoming information from receptors which then forward processed information to other destingations.

Question 76

facilitation

Answer 76

the enhancement of the response of a neuron to a stimulus following stimulation.
“the response is dependent on the frequency of stimulation and on neuromuscular facilitation”

Question 77

convergence

Answer 77

Allows one neuron to relay information to its neighbor. Long chains of these can be used to propagate information through the nervous system.

Question 78

divergence

Answer 78

an impulse originating from a single motor neuron in the CNS may stimulate several muscle fibers in a skeletal muscle to contract.
allows one neuron to communicate with many other neurons in a network.