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Human physiology Spain > Chapter 3A > Flashcards

Chapter 3A Flashcards

1
Q

Nervous system is organized into two
main subdivisions:

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

Nervous tissue comprises two types of cells:

A

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

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3
Q

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

A

True

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4
Q

Neuroglia of the CNS exists of four types:

A

astrocytes,
oligodendrocytes, microglial cells, and ependymal cells.

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5
Q

Neuroglia of the PNS exists of two types:

A

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

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6
Q

What is electrical excitability?

A

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

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7
Q

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

A

action potential

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8
Q

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

A

x = electrical
x= membrane

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9
Q

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

A

x = ions
x = ion channels

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10
Q

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.

A

receiving
input

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11
Q

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

A

nerve impulses toward another neuron

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12
Q

Trigger zone: this is where..

A

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

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13
Q

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

A

False (=many)

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14
Q

Direction of information
flows (put in right order)

axon
cell body
axon terminals
dendrites

A

dendrites → cell body → axon → axon
terminals

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15
Q

Cytoplasm of an axon is called

A

axoplasm

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16
Q

plasma membrane of axon is called

A

axolemma

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17
Q

axon collaterals = ?

A

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

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18
Q

Classification of neurons: STRUCTURAL CLASSIFICATION: vs FUNCTIONAL CLASSIFICATION:

A

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

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19
Q

STRUCTURAL CLASSIFICATION:

Multipolar neurons
Bipolar neurons
Unipolar neurons

A

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

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20
Q

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

A

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

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21
Q

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

A

A insulates
B increases the speed

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22
Q

Two types of neuroglia produce and maintain myelin sheaths

A

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

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23
Q

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

A

x = outermost
x = inner

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24
Q

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

A

ganglion in the PNS
and nucleus in the CNS.

25
Q

The axons of neurons are usually grouped together in x

A

bundles

26
Q

white matter vs grey matter: composed of?

A

White matter: myelinated axons

Gray matter: the rest

neuronal
cell bodies, dendrites,
unmyelinated axons, axon
terminals, and neuroglia

27
Q

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

A

True

28
Q

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

A

polarized.

29
Q

Most body cells are polarized.
True/false

A

true

30
Q

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

A

false: inside is negative

31
Q

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

A

sodium-potassium pump.

32
Q

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

A

ATP

33
Q

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

A

three sodium
two potassium

34
Q

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.

A

negative

35
Q

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

A

-70 mV
-90

36
Q

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.
A

a resting membrane potential
ion channels

37
Q

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

A

hyperpolarizing
depolarizing (p.36)

38
Q

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

A

Na+, , Ca+ and Cl-

  • K+
39
Q

The opening of sodium and calcium channels causes ….

The opening of chlorine and
potasium channels causes:

A
  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).
40
Q

What is a graded potential?

A

Graded potentials (small deviation from the resting membrane)

41
Q

where do graded potentials mostly occur?

A

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

42
Q

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

A

amplitude

43
Q

X is the process by which graded potentials add together:

A

Summation

44
Q

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

A

bien

45
Q

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

A

X mechanicallygated,
ligand-gated

46
Q

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).

A

A membrane
B threshold

47
Q

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

A

true

48
Q

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.

A

suprathreshold

49
Q

An action potential has two main phases

After these phases: afterhyperpolarizing phase (more negative than resting)

A

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.

50
Q

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.

A

all-or-none

51
Q

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.
A
  1. Na+ and k+
  2. Na+
  3. NA+ close, K+ opens
  4. K+
52
Q

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

A

true

53
Q

Refractory period: what cannot happen during this period?

A

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

54
Q

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

A

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

55
Q

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

A

gracias

56
Q

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

A

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

57
Q

What two stages can be destinguished of the refractory period?

A

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

58
Q
A

Human physiology Spain (23 decks)

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