Nervous System

Question 1

Sensory input

Answer 1

Information about the internal and external environments of the body that travels from sensory receptors to a control center via afferent pathways.

Question 2

Integration

Answer 2

The process by which the nervous system processes and interprets sensory input and makes decisions about what should be done at each moment.

Question 3

Motor output

Answer 3

Information from a control center that travels via efferent pathways to effectors (muscles and glands) in order to cause a response.

Question 4

Central Nervous System

Answer 4

Consists of brain and spinal cord

Question 5

Peripheral Nervous System

Answer 5

Consists of cranial nerves, spinal nerves, ganglia

Question 6

Which division of the CNS is voluntary?

Answer 6

Somatic

Question 7

Which division of the CNS is involuntary?

Answer 7

Autonomic

Question 8

What are the two types of cells that make up nervous tissue?

Answer 8

Neurons and neuroglia

Question 9

Neuroglia

Answer 9

Nonexcitable cells of neural tissue that support, protect, and insulate the neurons. Also called glial cells, or glia

Question 10

Astrocyte

Answer 10

A type of CNS supporting cell; assists in exchanges between blood capillaries and neurons. Most abundant type of glia

Question 11

Microglial cells

Answer 11

A type of CNS supporting cell; can transform into phagocytes in areas of neural damage or inflammation. Also called microglia

Question 12

Ependymal cells

Answer 12

A type of CNS supporting cell; lines the central cavities of the brain and spinal cord. Help circulate the cerebrospinal fluid that cushions the brain

Question 13

Oligodendrocytes

Answer 13

A type of CNS supporting cell that composes myelin sheaths

Question 14

Satellite cells

Answer 14

A type of supporting cell in the PNS; supports the neuronal cell body

Question 15

Schwann cells

Answer 15

Surround all nerve fibers in the PNS and form myelin sheaths around the thicker nerve fibers

Question 16

Neurons

Answer 16

Nerve cells; structural units of the nervous system; conduct messages in the form of action potentials (nerve impulses) from one part of the body to another

Question 17

Soma

Answer 17

Neuron cell body; consists of a spherical nucleus (with a conspicuous nucleolus) surrounded by cytoplasm

Question 18

What are the two types of neuron processes?

Answer 18

Dendrites and axons

Question 19

Dendrite

Answer 19

Branching neuron process that serves as a receptive, or input, region; transmits an electrical signal toward the cell body.

Question 20

Axon

Answer 20

Neuron process that carries action potentials away from the neuron cell body; efferent process; the conducting portion of a neuron.

Question 21

Axon hillock

Answer 21

The cone-shaped area of the cell body from which the axon arises.

Question 22

Any long axon is also called a ________

Answer 22

nerve fiber

Question 23

Myelin sheath

Answer 23

Whitish, fatty insulating sheath that surrounds all but the smallest axons; protects and electrically insulates axons, and it increases the transmission speed of nerve impulses

Question 24

Myelin sheath gaps

Answer 24

The short segments of exposed axon plasma membrane that are located between the areas of the axon that are wrapped in myelin; also called nodes of Ranvier.

Question 25

Nissl body

Answer 25

Sistinct structure found within the cell body (soma) and dendrites of neurons, composed primarily of rough endoplasmic reticulum

Question 26

Excitatory Postsynaptic Potential (EPSP)

Answer 26

(EPSPs) Depolarizing graded potential in a postsynaptic neuron; makes the neuron more likely to fire an AP

Question 27

Ganglia

Answer 27

A collection of nerve cell bodies, primarily found in the peripheral nervous system

Question 28

Tracts

Answer 28

Bundles of axons in the central nervous system

Question 29

Multipolar neurons

Answer 29

Have three or more processes—one axon and the rest dendrites. Most common neuron type in humans; major neuron type in the CNS

Question 30

Bipolar neurons

Answer 30

Have two processes—an axon and a dendrite—that extend from opposite sides of the cell body. Rare; found in some of the special sense organs such as in the retina of the eye and in the olfactory mucosa

Question 31

Unipolar neurons

Answer 31

Have a single short process that emerges from the cell body and divides T-like into proximal and distal branches; found chiefly in ganglia in the PNS, where they function as sensory neurons

Question 32

Sensory neurons

Answer 32

Transmit impulses from sensory receptors in the skin or internal organs toward or into the central nervous system; virtually all are unipolar

Question 33

Motor neurons

Answer 33

Carry impulses away from the CNS to the effectors (muscles and glands) of the body; multipolar

Question 34

Interneurons

Answer 34

Lie between motor and sensory neurons in neural pathways and shuttle signals through CNS pathways where integration occurs; most are multipolar

Question 35

Leakage (nongated) channel

Answer 35

An ion channel that is always open

Question 36

Chemically (ligand) gated channel

Answer 36

Open when the appropriate chemical (e.g a neurotransmitter) binds

Question 37

Voltage-gated channel

Answer 37

Opens and closes in response to changes in the membrane potential

Question 38

Mechanically gated channel

Answer 38

Opens in response to physical deformation of the receptor

Question 39

Resting membrane potential

Answer 39

The voltage that exists across the plasma membrane during the resting state of an excitable cell; typically ranges from -50 to -90 millivolts depending on cell type.

Question 40

Graded potential

Answer 40

Short-lived, localized changes in membrane potential, usually in dendrites or the cell body; operate over short distances that have variable (graded) strength

Question 41

Action potential

Answer 41

Long-distance signals of axons that always have the same strength

Question 42

Depolarization

Answer 42

A decrease in membrane potential—inside of membrane potential becomes less negative than the resting potential

Question 43

Hyperpolarization

Answer 43

An increase in membrane potential—the inside of the membrane becomes more negative (moves farther from zero) than the resting potential

Question 44

What triggers a graded potential?

Answer 44

Some change (a stimulus) in the neuron’s environment that opens gated ion channels

Question 45

Postsynaptic potential

Answer 45

Produced when the stimulus is a neurotransmitter released by another neuron

Question 46

End-plate potential

Answer 46

Occurs in a muscle cell, where it triggers an action potential that leads to muscle contraction

Question 47

In a neuron, an action potential is also called a _____

Answer 47

nerve impulse

Question 48

What are the steps of an action potential?

Answer 48

1. Resting state: All gated Na+ and K+ channels are closed 2. Depolarization: Na+ channels open, allowing Na+ entry 3. Repolarization: Na+ channels inactivate, K+ channels open, allowing K+ to exit 4. Hyperpolarization: Some K+ channels remain open, Na+ channels reset

Question 49

Resting state (stage of AP)

Answer 49

All gated Na+ and K+ channels are closed

Question 50

Depolarization (stage of AP)

Answer 50

Na+ channels open, allowing Na+ entry

Question 51

Repolarization (stage of AP)

Answer 51

Na+ channels inactivate, K+ channels open, allowing K+ to exit

Question 52

Hyperpolarization (stage of AP)

Answer 52

Some K+ channels remain open, Na+ channels reset

Question 53

Threshold

Answer 53

The membrane potential (b/t -55 and -50 mv) required to open enough voltage-gated ion channels to initiate an action potential.

Question 54

How does the nervous system code for stimulus intensity?

Answer 54

Strong stimuli generate nerve impulses more frequently (higher frequency of action potentials) in a given time interval than weak stimuli

Question 55

Absolute refractory period

Answer 55

Period that begins with the opening of the Na+ channels and ends when the Na+ channels begin to reset to their original resting state; neuron cannot generate another AP, no matter how strong the stimulus

Question 56

Relative refractory period

Answer 56

Follows the absolute refractory period; Period when exceptionally strong stimulus can reopen the channels that have already returned to their resting state and generate another AP

Question 57

What two factors impact the speed of impulse propagation?

Answer 57

1. Axon diameter (larger = faster) 2. Degree of myelination (presence of myelin sheath = faster)

Question 58

Saltatory conduction

Answer 58

Transmission of an action potential along a myelinated fiber in which the action potentials appears to leap from gap to gap.

Question 59

A fibers

Answer 59

- Largest diameter - Heavily myelinated - Fast impulses (300+ mph)

Question 60

B fibers

Answer 60

- Intermediate diameter - Lightly myelinated - Transmits impulses at ~30 mph

Question 61

C fibers

Answer 61

- Smallest diameter - Nonmyelinated axons - Slow conduction of impulses (2 mph)

Question 62

Neural integration

Answer 62

The summation of many EPSPs and IPSPs at the axon's initial segment

Question 63

Inhibitory postsynaptic potentials

Answer 63

(IPSPs) A graded potential in a postsynaptic neuron that inhibits action potential generation; usually hyperpolarizing.

Question 64

Synaptic potentiation

Answer 64

The phenomenon in which repeated or continuous use of a synapse enhances the presynaptic neuron’s ability to excite the postsynaptic neuron, producing larger-than-expected excitatory postsynaptic potentials (EPSPs).

Question 65

Presynaptic inhibition

Answer 65

Decreased release of excitatory neurotransmitter from a presynaptic neuron due to the activity of another neuron via an axoaxonal synapse; reduces the excitatory stimulation on the postsynaptic membrane.

Question 66

Serial processing

Answer 66

A pattern of neural processing in which information is processed sequentially; for example, one neuron stimulates the next neuron, which in turn stimulates the next neuron, and so on, eventually causing a response.

Question 67

Parallel processing

Answer 67

A pattern of neural processing in which information splits into many pathways, and different parts of the neural circuitry deal simultaneously with the information delivered by each pathway.

Question 68

Neural circuit

Answer 68

The pattern of synaptic connections between neurons.

Question 69

Diverging circuit

Answer 69

One input, many outputs; amplifying

Question 70

Converging circuit

Answer 70

Many inputs, one output; concentrating circuit

Question 71

Reverberating circuit

Answer 71

Signal travels through a chain of neurons, each providing feedback to previous neurons; oscillating circuit; controls rhythmic activity