Chapter 3A

Question 1

Nervous system is organized into two
main subdivisions:

Answer 1

1. Central nervous system (CNS):
   brain and spinal cord
2. Peripheral nervous system
   (PNS): all nervous tissue
   outside CNS.

Question 2

Nervous tissue comprises two types of cells:

Answer 2

Neurons
Neuroglia (support neurons, maintain fluid that bathes them)

Question 3

Neuroglia can be found in the CNS and in the PNS
True/false

Answer 3

True

Question 4

Neuroglia of the CNS exists of four types:

Answer 4

astrocytes,
oligodendrocytes, microglial cells, and ependymal cells.

Question 5

Neuroglia of the PNS exists of two types:

Answer 5

Schwann cells
Satellite cells
(see p 12, chapter 3A)

Question 6

What is electrical excitability?

Answer 6

to respond to stimulus and convert it into an action potential.

Question 7

stimulus is any change in the environment that is strong enough to initiate
an x

Answer 7

action potential

Question 8

action potential (nerve impulse) = an x signal that propagates
along the surface of the x of a neuron

Answer 8

x = electrical
x= membrane

Question 9

an action potential begins and travels due to the movement of x between interstitial fluid and the inside of a neuron through
specific x in its plasma membrane

Answer 9

x = ions
x = ion channels

Question 10

Dendrites: are the x or x portions of a neuron. The plasma membranes
of dendrites (and cell bodies) contain numerous receptor sites for binding chemical
messengers from other cells. Dendrites usually are short, tapering, and highly
branched.

Answer 10

receiving
input

Question 11

Axon: propagates x: a muscle fiber, or a gland
cell. An axon is a long, thin, cylindrical projection.

Answer 11

nerve impulses toward another neuron

Question 12

Trigger zone: this is where..

Answer 12

nerve impulses arise (begin van de steel aan de kant van het lichaam van de cel)

Question 13

Little neurons contain two or even three types of neurotransmitters
True/false

Answer 13

False (=many)

Question 14

Direction of information
flows (put in right order)

axon
cell body
axon terminals
dendrites

Answer 14

dendrites → cell body → axon → axon
terminals

Question 15

Cytoplasm of an axon is called

Answer 15

axoplasm

Question 16

plasma membrane of axon is called

Answer 16

axolemma

Question 17

axon collaterals = ?

Answer 17

side branches along the length of an axon
(see p 16, chapter 3A)

Question 18

Classification of neurons: STRUCTURAL CLASSIFICATION: vs FUNCTIONAL CLASSIFICATION:

Answer 18

structural: number of precesses extending from the body
functional: direction in which the action potential is conveyed relative to the CNS

Question 19

STRUCTURAL CLASSIFICATION:

Multipolar neurons
Bipolar neurons
Unipolar neurons

Answer 19

multipolar: several dendrites and one axon (brain & spinal)
Bipolar: one main dendrite and one axon (eye, olfactory (smell) area of brain)
Unipolar: dendrites and one axon that are fused together

Question 20

FUNCTIONAL CLASSIFICATION
Sensory/afferent
Motor neurons/efferent neurons
Interneurons/association neurons

Answer 20

Sensory/afferent: (into the CNS)
Motor neurons/efferent neurons: away from CNS
Interneurons/association neurons: within CNS

Question 21

Myelin sheath: multilayered lipid and protein covering around some axons that
A them and B of nerve impulse conduction

Answer 21

A insulates
B increases the speed

Question 22

Two types of neuroglia produce and maintain myelin sheaths

Answer 22

Schwann cells in the PNS (each schwann myelinates a single axon)
Oligodendrocytes in the CNS (single oligodendrocyte myelinates several axons)

Question 23

Schwann cells begin to form myelin sheaths around axons during fetal development.
* Multiple layers of glial plasma membrane surround the axon

The Schwann cell’s cytoplasm and nucleus forming the X layer.
The x portion (myelin sheath), consisting of up to 100 layers of Schwann cell membrane

Answer 23

x = outermost
x = inner

Question 24

Neuronal cell bodies are often grouped together in clusters: what are they called in CNS vs PNS?

Answer 24

ganglion in the PNS
and nucleus in the CNS.

Question 25

The axons of neurons are usually grouped together in x

Answer 25

bundles

Question 26

white matter vs grey matter: composed of?

Answer 26

White matter: myelinated axons Gray matter: the rest neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia

Question 27

uneven distribution of ions: ONLY at the cell membrane part? True/false?

Answer 27

True

Question 28

A cell that exhibits a membrane potential is said to be X

Answer 28

polarized.

Question 29

Most body cells are polarized. True/false

Answer 29

true

Question 30

The minus sign indicates that the outside of the cell is negative relative to the outside. True/false

Answer 30

false: inside is negative

Question 31

the resting membrane potential is maintained by the activity of a protein called the ...

Answer 31

sodium-potassium pump.

Question 32

The pump moves sodium and potassium ions in opposite directions, each against its concentration gradient. Thus it requires x

Answer 32

ATP

Question 33

In a single cycle of the pump, X sodium ions are extruded from and X ions are imported into the cell.

Answer 33

three sodium two potassium

Question 34

Because 3 Na+ are exported for every 2 K+ brought into the cell, the pump makes the membrane potential slightly more X than it would otherwise be.

Answer 34

negative

Question 35

In neurons, the resting membrane potential varies from .... mV to .....

Answer 35

-70 mV -90

Question 36

The production of potentials depends on two basic features of the plasma membrane of excitable cells: 1. the existence of X across the membrane and 2. the presence of specific types of X.

Answer 36

a resting membrane potential ion channels

Question 37

A graded potential is a small deviation from the resting membrane potential that makes the membrane potential: * more negative: X * more positive (less negative):

Answer 37

hyperpolarizing depolarizing (p.36)

Question 38

1, 2, 3 will tend to ENTER the cell. (type ionen) 4 will tend to LEAVE the cell.

Answer 38

Na+, , Ca+ and Cl- * K+

Question 39

The opening of sodium and calcium channels causes .... The opening of chlorine and potasium channels causes:

Answer 39

1. depolarization: both ions (positive charges) enter the cell and make the membrane potential LESS negative. 2. hyperpolarization: chlorine (negative charges) enters the cell and potasium (positive charges) leaves the cell. Both events make the membrane potential MORE negative).

Question 40

What is a graded potential?

Answer 40

Graded potentials (small deviation from the resting membrane)

Question 41

where do graded potentials mostly occur?

Answer 41

mainly in the dendrites and cell body of a neuron. (p40)

Question 42

The X of a graded potential depends on the stimulus strength. The larger the X, the greater the stimulus strength.

Answer 42

amplitude

Question 43

X is the process by which graded potentials add together:

Answer 43

Summation

Question 44

Summation: If two depolarizing graded potentials summate, the net result is a larger depolarizing graded potential. * If two hyperpolarizing graded potentials summate, the net result is a larger hyperpolarizing graded potential. * If two equal but opposite graded potentials summate (one depolarizing and the other hyperpolarizing), then they cancel each other out and the overall graded potential disappears

Answer 44

bien

Question 45

A graded potential occurs when a stimulus causes X or X channels to open or close in an excitable cell’s plasma membrane.

Answer 45

X mechanicallygated, ligand-gated

Question 46

An action potential occurs in the A of the axon of a neuron when depolarization reaches a certain level termed the B (about − 55 mV in many neurons).

Answer 46

A membrane B threshold

Question 47

An action potential will not occur in response to a subthreshold stimulus: a weak depolarization that cannot bring the membrane potential to threshold. However, an action potential will occur in response to a threshold stimulus, a stimulus that is just strong enough to depolarize the membrane to threshold. True/false

Answer 47

true

Question 48

Several (read: multiple!!) action potentials will form in response to a X stimulus, a stimulus that is strong enough to depolarize the membrane above threshold.

Answer 48

suprathreshold

Question 49

An action potential has two main phases After these phases: afterhyperpolarizing phase (more negative than resting)

Answer 49

Depolarizing phase: the negative membrane potential becomes less negative, reaches zero, and then becomes positive. 2. Repolarizing phase: the membrane potential is restored to the resting state of − 70 mV.

Question 50

An action potential is generated in response to a threshold stimulus but does not form when there is a subthreshold stimulus. * In other words, an action potential either occurs completely or it does not occur at all. * This characteristic of an action potential is known as the X principle.

Answer 50

all-or-none

Question 51

ACTION POTENTIAL MECHANISM for ion channels: 1. Resting state: .... channels are closed 2. Depolarizing state: when membrane potential reaches threshold, the .... channels open 3. repolarizing state: ... channels close and .... channels open 4. repolarizing: .... outflow continues.

Answer 51

1. Na+ and k+ 2. Na+ 3. NA+ close, K+ opens 4. K+

Question 52

Because the voltage-gated K+ channels open more slowly during repolarizing, their opening occurs at about the same time the voltage-gated Na+ channels are closing. True/false

Answer 52

true

Question 53

Refractory period: what cannot happen during this period?

Answer 53

an excitable cell cannot generate another action potential in response to a normal threshold stimulus. (because the action potential is beginning)

Question 54

Absolute refractory period: even a very strong stimulus cannot initiate a second action potential. Is this true? If so, why?

Answer 54

yes Inactivated Na+ channels cannot reopen; they first must return to the resting state.

Question 55

At the start of action potential: we say that he Na+ channels are RESTING and the K+ channels are closed.

Answer 55

gracias

Question 56

In terms of channels open and close, what do the channels do during the absolute refractory period?

Answer 56

NA+ gates open and, K+ channels open, NA+ inactivating

Question 57

What two stages can be destinguished of the refractory period?

Answer 57

absolute (no second action potential) and relative (second action potential only with very strong stimulus)