Anatomy And Physiology 1 (Martini Nath) : Chapter 12 - Neural Tissue

Front 1

Basic functional units of nervous system, which perform all communication, info processing and control functions of the nervous system

Back 1

neurons

Front 2

supporting cells (supporting neural tissue)

Back 2

neuroglia (a.k.a. glial cells), which outnumber neurons

Front 3

how neuroglia (glial cells) support neural tissue:

Back 3

separate and protect neurons, provide supportive framework for neural tissue, act as phagocytes, help regulate composition of interstitial fluid

Front 4

neural tissue forms body parts:

Back 4

brain, spinal cord, receptors in complex sense organs (in eye and ear), nerves that link nervous system with other systems

Front 5

central nervous system (components)

Back 5

spinal cord and brain (including both neural tissue and blood vessels and connective tissues

Front 6

central nervous system (CNS function)

Back 6

integrating, processing, coordinating sensory data and motor commands

aka

seat of higher functions

Front 7

sensory data

Back 7

info about conditions inside and outside the body

Front 8

motor commands

Back 8

actions to control activities of peripheral organs (such as skeletal muscles)

Front 9

peripheral nervous system components

Back 9

includes all neural tissue outside CNS, bundles of axons (nerves) and their supporting tissue

Front 10

peripheral nervous system subtypes

Back 10

peripheral nerves/nerves, cranial nerves, spinal nerves

Front 11

Peripheral nervous system (PNS) is divided into two divisions

Back 11

Afferent (afferens to bring to)

and

Efferent (effero to bring out)

Front 12

Afferent division of PNS

Back 12

brings sensory information to CNS from receptors in peripheral tissues and organs

Front 13

receptors, which may be neurons or specialized cells, are:

Back 13

sensory structures that:

detect changes in environment (internal body or external)

OR

respond to specific stimuli

Front 14

function of the Efferent division (PNS), which has both somatic and autonomic components,

Back 14

carries motor commands from CNS to three types of effectors: muscles, glands and adipose tissue

Front 15

effectors

Back 15

target organs which respond by doing something

Front 16

Somatic section (SNS) of the Efferent division of CNS:

Back 16

controls skeletal muscle contractions, which mostly means voluntary movements along with a few involuntary limb reflexes

Front 17

Autonomic section (ANS) of the Efferent division of CNS:

Back 17

regulates smooth muscle

cardiac muscle contractions and

glandular secretions

adipose tissue

(this is all subconscious)

Front 18

Most common type of neuron shape

Back 18

multipolar neuron (large cell body, several short branched dendrites, long single axon which ends in several telodendria)

Front 19

cell body is called

Back 19

soma

Front 20

soma/cell body contains

Back 20

perikaryon (cytoplasm around nucleus) and its cytoskeleton,

a large round nucleus...

Front 21

neurofibrils in a neuron

Back 21

bundles of neurofilaments extend into dendrites and axon, providing internal support

Front 22

perikaryon

Back 22

includes cytoplasm around nucleus which contains neurofilaments and neurotubules

contains organelles that provide energy and synthesize organic materials

Front 23

organelles inside the perikaryon of the neuron

Back 23

regions withRough endoplasmic reticulum and free ribosomes

= nissl bodies (gray) (cause brain etc to be gray)

Front 24

organelles not inside the perikaryon of the neuron

Back 24

centrioles are not present

Front 25

CNS neurons cannot

Back 25

divide

Front 26

dendrites

Back 26

-variable in number
-extend from cell body
-highly branched
-each branch has studded dendritic spines

Front 27

axon

Back 27

a long cytoplasmic process capable of propagating an electrical impulse aka action potential

Front 28

dendrites' roles

Back 28

involved in intercellular communication

Front 29

a process in anatomy is a

Back 29

a projection or outgrowth of tissue from a larger body

Front 30

electrical impulse

Back 30

action potential

Front 31

axoplasm is:

Back 31

cytoplasm of the axon containing neurofibrils, neurotubules, small vesicles, lysosomes, mitochondria and enzymes

Front 32

-next to the slender axon
-specialized portion of plasma membrane which surrounds the axoplasm

Back 32

axolemma

Front 33

type of fluid that an axolemma MAY be exposed to in CNS, OR type of cells that the axolemma MAY be covered by

Back 33

interstitial fluid, neuroglia

Front 34

thick base of an axon

Back 34

initial segment

Front 35

thickest part of initial segment base

Back 35

axon HILLOCK

Front 36

axon may branch out along its length in side branches called

Back 36

collaterals

Front 37

collaterals (function)

Back 37

enable a single neuron to communicate with several other cells

Front 38

collaterals end in fine extensions (with circular tips)

Those extensions/endings are called:

Back 38

telodendria

Front 39

telodendria also known as

Back 39

terminal branches

Front 40

circular endings of telondria are called

Back 40

synaptic terminals

Front 41

synapse includes the

Back 41

synaptic terminal (tips)

Front 42

synapse

Back 42

specialized site where the neuron communicates with another cell

Front 43

every synapse involves two cells, the:

Back 43

presynaptic cell (sends message) and post synaptic cell (receives message)

Front 44

synaptic cleft

Back 44

area between two cells

Front 45

chemicals released into synaptic cleft space after the arrival of the action potential

Back 45

neurotransmitters

Front 46

presynaptic cell is usually

Back 46

a neuron

Front 47

structures that house neurotransmitters within the synaptic cleft

Back 47

synaptic vesicles

Front 48

post synaptic cell can be

Back 48

either a neuron or another type of cell

Front 49

synapse between neuron and muscle

Back 49

a neuromuscular junction

Front 50

a neuroglandular junction

Back 50

where a neuron controls or regulates the activity of a secretory (gland) cell

Front 51

to innervate

Back 51

to be distributed to

Front 52

neurons innervates several cell types including

Back 52

adipocytes

Front 53

structure of synaptic terminal depends on

Back 53

the type of postsynaptic cell

Front 54

structure of synaptic terminal is simple and round

Back 54

post-synaptic cell is another neuron

Front 55

neurotransmitters are released from

Back 55

the presynaptic membrane

Front 56

where receptors for neurotransmitters are

Back 56

postsynaptic membrane

Front 57

when the postsynaptic cell is a muscle and it is a neuromuscular junction, the synaptic terminal is

Back 57

more complex

Front 58

mitochondria, endoplasmic reticulum, vesicles filled with neurotransmitter molecules

Back 58

are located at the synaptic terminal

Front 59

synaptic terminal reabsorbs and reassembles the

Back 59

breakdown products of neurotransmitters formed at the synapse

Front 60

neurotransmitters, enzymes and lysosomes

Back 60

are received by synaptic terminal, after being hauled by molecular motors KINESIN and DYNEIN

Front 61

AXOPLASMIC TRANSPORT

Back 61

the movement of materials between the cell body and synaptic terminals

Front 62

types of axoplasmic transport

Back 62

slow stream and fast stream

Front 63

neurotransmitters move in axoplasmic transport using

Back 63

fast stream

Front 64

types of axoplasmic flow of materials: if from cell body to the synaptic terminals then it is

Back 64

anterograde flow

Front 65

types of axoplasmic flow of materials: if from synaptic terminals to cell body then it is

Back 65

retrograde flow

Front 66

anaxonic neurons

Back 66

have more than two processes

Front 67

anaxonic neurons' axons

Back 67

cannot be distinguished from dendrites

Front 68

bipolar neurons

Back 68

have 2 processes separated from the cell body

Front 69

bipolar neurons

Back 69

have dendritic branches

Front 70

unipolar neurons

Back 70

have a single elongate process, with the cell body situated off to the side

Front 71

multipolar neuron

Back 71

have more than two processes

Front 72

multipolar processes

Back 72

have a single axon and multiple dendrites

Front 73

bipolar neurons

Back 73

have one dendrite that branches extensively into the dendritic branches at its distal tip,

and one axon with the cell body between the two

Front 74

bipolar neuron

Back 74

are actually small and rare and occur in special sense organs

Front 75

unipolar neurons are aka

Back 75

pseudounipolar neurons

Front 76

unipolar neurons' dendrites and axons are

Back 76

continuous

Front 77

initial segment of a unipolar neuron is located

Back 77

where the dendrites converge

Front 78

most sensory neurons of the peripheral nervous system are

Back 78

unipolar neurons

Front 79

unipolar neurons' axons may extend

Back 79

a meter or more. the longest carry sensations from the tips to the toes to the spinal cord

Front 80

multipolar neurons have

Back 80

2 or more dendrites and a single axon

Front 81

the most common neurons in the CNS are

Back 81

multipolar neurons

Front 82

true or false: the axons of multipolar neurons can be as long as those of unipolar neurons

Back 82

true, the longest axons of multipolar neurons carry motor commands from the spinal cord to small muscles that move the toes

Front 83

The graded potential is a stimulus that

Back 83

temporarily causes a localized change in the resting potential.

Front 84

The oligodendrocyte functions to

Back 84

sheath certain axons of the central nervous system (CNS).

Front 85

Astrocytes have many functions, including

Back 85

the maintenance of the blood - brain barrier (BBB).

Front 86

Microglial cells are

Back 86

the phagocytes of the central nervous system (CNS).

Front 87

An action potential is an electrical impulse, which

Back 87

propagates along the surface of the axon.

Front 88

The graded potential is a stimulus that

Back 88

temporarily causes a localized change in the resting potential.

Front 89

The resting membrane potential is the

Back 89

moment-to-moment variation of the transmembrane potential in all living cells.

Front 90

Synaptic activity results in the production of graded potentials in

Back 90

the plasma membrane of the postsynaptic cell.

Front 91

The resting membrane potential is the

Back 91

moment-to-moment variation of the transmembrane potential in all living cells.

Front 92

An action potential is the brief but striking reversal of

Back 92

the membrane potential in excitable cells.

Front 93

A threshold potential is the

Back 93

minimum depolarization required to elicit an action potential.

Front 94

Synaptic activity results in the production of

Back 94

graded potentials in the plasma membrane of the postsynaptic cell.

Front 95

The resting membrane potential is the

Back 95

baseline potential that can be recorded across the plasma membrane of an excitable cell prior to excitation.

Front 96

Sodium-potassium ATPases are present in all cells, but they actively transport Na+ and K+ across the

Back 96

plasma membrane.

Front 97

Some ligand-gated channels do permit Na+ and K+ to

Back 97

passively move across plasma membranes, but they are not present in all cells.

Front 98

Leak channels for Na+ and K+ are ubiquitous, and they allow for the

Back 98

diffusion of these ions across plasma membranes.

Front 99

The inside surface of the plasma membrane accumulates more negative charge because

Back 99

of the presence of Na+ and K+ gradients and the selective permeability of the membrane to Na+ and K+.

Front 100

There are many more K+ leak channels than

Back 100

than Na+ leak channels in the plasma membrane.

Front 101

More leak channels translates into more

Back 101

leakiness. Thus the outward flux of K+ is greater than the inward flux of Na+.

Front 102

The Na+-K+ pumps maintain the resting membrane potential by

Back 102

maintaining the Na+ and K+ gradients across the plasma membrane.

Front 103

True or False: Pump activity is not a major determinant of the RMP.

Back 103

True

Front 104

Due to the time involved in calcium influx and neurotransmitter release, the transmission of an action potential is delayed at

Back 104

the synaptic cleft.

Front 105

The events that occur at a functioning cholinergic synapse cause

Back 105

synaptic delay

Front 106

Where do most action potentials originate?

Back 106

initial segment

Front 107

Voltage-gated K+ channels are comparatively slow to open in response to

Back 107

a threshold stimulus.

Front 108

Ligand-gated Cl- channels are located in the

Back 108

plasma membrane of postsynaptic cell bodies and dendrites.

Front 109

The opening of Ligand-gated Cl- channels allows

Back 109

Cl- to diffuse into the cell.

Front 110

This Cl- diffusion results in a hyperpolarization, which can lead to

Back 110

inhibition.

Front 111

Ligand-gated cation channels are located in the

Back 111

plasma membrane of postsynaptic cell bodies and dendrites.

Front 112

Na+ and K+ diffusion results in a depolarization, which can lead to

Back 112

excitation.

Front 113

The opening of Ligand-gated cation channels allows

Back 113

Na+ to enter and K+ to exit the cell.

Front 114

Synaptic transmission refers to the transfer of neural information between a neuron and

Back 114

another cell

Front 115

A synapse between two neurons influences the generation and propagation of

Back 115

an action potential in the postsynaptic axon.

Front 116

An action potential is conducted in a saltatory (Latin, saltare; to leap) fashion along

Back 116

myelinated axons

Front 117

An action potential is conducted continuously along

Back 117

an unmyelinated axon from its initial segment to the axon terminals.

Front 118

The term continuous in continuous conduction refers to the fact that the action potential is regenerated when voltage-gated Na+ channels open in

Back 118

every consecutive segment of the axon, NOT at nodes of Ranvier.

Front 119

An action potential is self-regenerating because

Back 119

flow down the axon and trigger an action potential at the next segment

Front 120

Regeneration of the action potential occurs in one direction BECAUSE

Back 120

The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.

Front 121

The myelin sheath increases the speed of action potential conduction from the

Back 121

initial segment to the axon terminals.

Front 122

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

Back 122

Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.

Front 123

Closing of voltage-gated channels is

Back 123

time dependent. Typically, the inactivation gates of voltage-gated Na+ channels close about a millisecond after the activation gates open. At the same time, the activation gates of voltage-gated K+ channels open.

Front 124

In which type of axon will velocity of action potential conduction be the fastest?

Back 124

Myelinated axons with the largest diameter

Front 125

Where in the neuron is an action potential initially generated?

Back 125

axon hillock

Front 126

The depolarization phase of an action potential results from the opening of which channels?

Back 126

voltage-gated Na+ channels (when the voltage-gated Na+ channels open, Na+ rushes into the cell causing depolarization.)

Front 127

The repolarization phase of an action potential results from

Back 127

the opening of voltage-gated K+ channels

Front 128

as the voltage-gated K+ channels open, K+ rushes out of the cell, causing

Back 128

the membrane potential to become more negative on the inside, thus repolarizing the cell.

Front 129

Hyperpolarization results from

Back 129

slow closing of voltage-gated K+ channels

Front 130

the slow closing of the voltage-gated K+ channels means that more K+ is leaving the cell, making it more _____ inside.

Back 130

negative

Front 131

the membrane goes from –70 mV to

Back 131

+30 mV.

Front 132

Thus, during the action potential, the inside of the cell becomes more ______ than the outside of the cell.

Back 132

positive

Front 133

What is the magnitude (amplitude) of an action potential?

Back 133

100 mV

Front 134

How is an action potential propagated along an axon?

Back 134

An influx of sodium ions from the current action potential depolarizes the adjacent area.

Front 135

the influx of sodium ions depolarizes adjacent areas, causing the membrane to

Back 135

reach threshold and cause an action potential. Thus, the action potential is regenerated at each new area.

Front 136

Why does the action potential only move away from the cell body?

Back 136

The areas that have had the action potential are refractory to a new action potential. (sodium channels are inactivated in the area that just had the action potential.)

Front 137

The velocity of the action potential is fastest in which of the following axons?

Back 137

a small myelinated axon

Front 138

the myelination acts as insulation and the action potential is generated only at

Back 138

the nodes of Ranvier.

Front 139

Propagation along myelinated axons is known as

Back 139

saltatory conduction.

Front 140

slower propagating
smaller diameter
unmyelinated

Back 140

characteristics of TYPE C AXONS, compared to to the faster, larger more myelinated type A axons are

Front 141

Compared to nerve action potentials, muscle action potentials do not have __________.

Back 141

faster propagation

Front 142

Which of these axons will conduct an action potential most quickly?

Back 142

Type A fiber

Front 143

The activation gates of voltage-gated Na+ channels open very

Back 143

rapidly in response to threshold stimuli.

Front 144

relative to the activation gates of voltage-gated Na+ channels, the activation gates of voltage-gated K+ channels are comparatively

Back 144

slow to open.

Front 145

The synaptic cleft is the small space between

Back 145

the sending neuron and the receiving neuron.

Front 146

Neurotransmitter molecules carry information across

Back 146

a synaptic cleft.

Front 147

Resting voltage of -70 mV to a threshold value of -55 mV, this is the minimum value required to

Back 147

open enough voltage-gated Na+ channels so that depolarization is irreversible.

Front 148

When calcium ions enter the synaptic terminal, they cause

Back 148

vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

Front 149

The plasma membrane, which was polarized to a negative value at the RMP, depolarizes to

Back 149

a positive value.

Front 150

The activation gates of voltage-gated Na+ channels open, and ____ diffuses into the cytoplasm.

Back 150

Na+

Front 151

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

Back 151

ion channels in the plasma membrane of the receiving neuron open.

Front 152

If a signal from a sending neuron makes the receiving neuron more negative inside,

Back 152

the receiving neuron is less likely to generate an action potential.

Front 153

acetylcholine is broken down by acetylcholinesterase AND THEN IS

Back 153

returned to the presynaptic neuron’s axon terminal.

Front 154

Which of the neurotransmitter is broken down by an enzyme before being returned?

Back 154

acetylcholine

Front 155

the neurotransmitter can cause the postsynaptic membrane to either

Back 155

depolarize or hyperpolarize, depending on which ion channels are opened.

Front 156

the neurotransmitter is a chemical released from the presynaptic membrane, so it would open

Back 156

chemically gated channels on the postsynaptic membrane.

Front 157

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

Back 157

Binding of a neurotransmitter to its receptors opens _____CHEMICALLY GATED_____ channels on the ______POSTSYNAPTIC____ membrane.

Front 158

An action potential releases neurotransmitter from a neuron by opening which channels?

Back 158

voltage-gated Ca2+ channels

Front 159

opening of voltage-gated Ca2+ channels causes calcium to move into

Back 159

the axon terminal.

Front 160

Calcium inside the neuron causes the vesicles to merge with the _____ and release the ______ via exocytosis into the synaptic cleft

Back 160

Calcium inside the neuron causes the vesicles to merge with the membrane and release the neurotransmitter via exocytosis into the synaptic cleft.

Front 161

neurotransmitters are stored in the axon terminals of the presynaptic neuron.

Back 161

neurotransmitters are stored in the axon terminals of the presynaptic neuron.

Front 162

Which of these neurotransmitters does not bind to a plasma membrane receptor?

Back 162

nitric oxide

Front 163

The sodium-potassium exchange pump stabilizes resting potential at about __________.

Back 163

-70 mV

Front 164

The most abundant intracellular cation is __________ while the most abundant extracellular anion is __________.

Back 164

The most abundant intracellular cation is potassium while the most abundant extracellular anion is chloride

Front 165

Which type of ion channel is always open?

Back 165

passive

Front 166

Action potential propagation begins (is first generated at) what region of a neuron?

Back 166

initial segment

Front 167

Graded potentials created in the dendrites and soma will, if sufficiently depolarizing, generate an action potential in the initial segment of the axon.

Back 167

an action potential in the initial segment of the axon.

Front 168

Where are action potentials regenerated as they propagate along an unmyelinated axon?

Back 168

at every segment of the axon

Front 169

The action potential will then propagate away from

Back 169

the initial segment, down the axon.

Front 170

In unmyelinated axons, the action potential is regenerated continuously along every segment of the axon

and that is called

Back 170

continuous propagation

Front 171

The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold?

Back 171

sodium (Na+)

Front 172

Sodium ions enter the cell during the

Back 172

beginning of an action potential.

Front 173

In an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction?

Back 173

The previous axonal segment is refractory.

Front 174

Approximately how fast do action potentials propagate in unmyelinated axons in humans?

Back 174

1 meter per second

Front 175

In contrast to the internodes of a myelinated axon, the nodes

Back 175

have lower membrane resistance to ion movement

Front 176

Where are action potentials regenerated as they propagate along a myelinated axon?

Back 176

at the nodes

Front 177

In myelinated axons, voltage-gated sodium channels are largely restricted to the nodes between

Back 177

myelinated internodes.

Front 178

action potentials only regenerate at

Back 178

the nodes.

Front 179

The high membrane resistance of the internodes ensures that local currents generated at one node will quickly

Back 179

bring the next node to threshold, even though it is 1-2 mm away.

Front 180

The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.

Back 180

Saltatory propagation, which is derived from the Latin word saltare, which means leaping.

Front 181

How do action potential propagation speeds in myelinated and unmyelinated axons compare?

Back 181

Propagation is faster in myelinated axons.

Front 182

Multiple sclerosis (MS) is a disease that stops action potential propagation by destroying the myelin around (normally) myelinated axons. Which of the following best describes how MS stops action potential propagation?

Back 182

Without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes.

Front 183

Myelin increases the membrane resistance of the axon section it surrounds, allowing local currents to

Back 183

travel between nodes, even though they are 1-2 mm apart.

Front 184

The initial segment has the lowest threshold and, therefore, is the place where

Back 184

most action potentials are initiated.

Front 185

During an action potential of a neuron, what directly causes the different channels to open and close?

Back 185

the transmembrane potential (voltage)

Front 186

Changes in transmembrane potential directly cause voltage-gated channel proteins to

Back 186

change shape and allow the flow of ions across the cell membrane.

Front 187

What is the typical duration of a nerve action potential?

Back 187

2 ms (although they can be longer in the heart)

Front 188

Around what transmembrane potential does threshold commonly occur?

Back 188

At approximately -60 mV, an action potential is initiated. A transmembrane potential -60 mV corresponds to a depolarization of 10-15 mV away from the resting membrane potential.

Front 189

A transmembrane potential of ______ is near the resting potential of the cell.

Back 189

-70 mV

Front 190

What ion is responsible for the depolarization of the neuron during an action potential?

Back 190

Na+ (sodium)

Front 191

What type of membrane transport causes the depolarization phase of the action potential in neurons?

Back 191

diffusion

Front 192

Ions move through channels according to

Back 192

their electrochemical gradient from one side of the membrane to the other.

Front 193

Ions move through channels according to their electrochemical gradient from one side of the membrane to the other AND THIS

Back 193

movement is known as channel-mediated diffusion.

Front 194

During an action potential, after the membrane potential reaches +30 mV, which event(s) primarily affect(s) the membrane potential?

Back 194

Voltage-gated sodium channels begin to inactivate (close) and voltage-gated potassium channels begin to open.

Front 195

The repolarization phase of the action potential involves decreasing sodium influx via inactivation of sodium channels and increasing potassium efflux (exit) via opening

Back 195

potassium channels. Both of these processes begin near the peak of the action potential.

Front 196

What ion causes repolarization of the neuron during an action potential?

Back 196

K+ (potassium)

Front 197

What causes repolarization of the membrane potential during the action potential of a neuron?

Back 197

potassium efflux (leaving the cell)

Front 198

Positively charged potassium ions flowing out of the cell makes the transmembrane potential more

Back 198

negative, repolarizing the membrane towards the resting potential.

Front 199

What is primarily responsible for the brief hyperpolarization near the end of the action potential?

Back 199

voltage-gated potassium channels taking some time to close in response to the negative membrane potential

Front 200

Which of these is the earliest step in the generation of an action potential?

Back 200

Sodium channels open.

Front 201

What happens just after an axon is depolarized to threshold?

Back 201

Some sodium channels open.

Front 202

During propagation of the action potential, WHAT 3 THINGS HAPPEN?

Back 202

1-the axon hillock depolarizes the initial segment

2-Local currents depolarize a spot adjacent to the active zone

3-after threshold is reached, sodium channels open rapidly

Front 203

What causes calcium channels in the synaptic knob to open?

Back 203

depolarization of the presynaptic membrane due to an arriving action potential

Front 204

Which of the following best describes the role of calcium in synaptic activity?

Back 204

Calcium enters the presynaptic cell and causes the release of ACh.

Front 205

As a presynaptic action potential reaches the synaptic terminal, _____ channels open.

Back 205

voltage-gated calcium channels open.

Front 206

The open calcium channels allow calcium to

Back 206

diffuse into the synaptic terminal.

Front 207

This calcium influx causes synaptic vesicles to

Back 207

fuse with the presynaptic membrane.

Front 208

Neurotransmitters exit the presynaptic cell via __________.

Back 208

Neurotransmitters exit the presynaptic cell via exocytosis

Front 209

When ACh receptors open, what ion causes depolarization of the postsynaptic membrane?

Back 209

sodium

Front 210

Positively charged sodium ions cross the postsynaptic membrane

Back 210

open ACh receptors.

Front 211

Which of the following best describes how ACh causes depolarization of the postsynaptic membrane?

Back 211

ACh opens ACh receptors.

Front 212

ACh receptors on the postsynaptic membrane are

Back 212

chemically gated ion channels. These channels open when they bind ACh.

Front 213

Once open, chemically gated channels allow sodium to enter, depolarizing the cell. Chemically gated channels are often called

Back 213

"receptors" because they must "receive" (or bind) a particular chemical before they can open.

Front 214

Which of the following best describes the order of events in synaptic activity?

Back 214

An action potential arrives and depolarizes the synaptic knob. Extracellular calcium enters the synaptic knob, triggering exocytosis of ACh. ACh binds to receptors and depolarizes postsynaptic membrane. ACh is removed by AChE.

Front 215

Where is acetylcholinesterase (AChE) primarily located?

Back 215

in the synaptic cleft

Front 216

What is the primary role of acetylcholinesterase (AChE) at a cholinergic synapse?

Back 216

AChE degrades acetylcholine in the synaptic cleft.

Front 217

Curare is a drug that prevents ACh from binding to ACh receptors. How would you expect curare to affect events at a cholinergic synapse?

Back 217

The postsynaptic cell would not depolarize.

Front 218

Which ion triggers synaptic vesicles to discharge neurotransmitter into the synaptic cleft?

Back 218

calcium

Front 219

The effect of a nerve impulse on a postsynaptic neuron depends on the __________.

what 3 things?

Back 219

1) characteristics of the receptor on the postsynaptic neuron

2) kind of neurotransmitter released by the presynaptic neuron

3) quantity of neurotransmitter released

Front 220

EPSPs and IPSPs summate at the __________.

Back 220

axon hillock

Front 221

EPSPs are ___________.

Back 221

excitatory, postsynaptic, graded

Front 222

If a nerve cell receives many IPSPs at the same time, __________.

Back 222

it will show spatial summation

Front 223

If EPSPs summate to a sustained value above threshold, then the initial segment will __________.

Back 223

generate a string of action potentials

Front 224

At rest, why is the transmembrane potential of a neuron (-70 mV) closer to the potassium equilibrium potential (-90 mV) than it is to the sodium equilibrium potential (+66 mV)?

Back 224

The membrane is much more permeable to potassium ions than to sodium ions.

Front 225

In a typical neuron, what is the equilibrium potential for sodium?

Back 225

+66 mV

Front 226

true or false: the equilibrium potential for sodium must be positive.

Back 226

positive, because it must oppose the entry of sodium ions.

Front 227

In a typical neuron, what is the equilibrium potential for sodium?

Back 227

+66 mV

Front 228

Compared to the electrical gradient for sodium at rest, the electrical gradient for potassium at rest is __________.

Back 228

in the same direction and of the same magnitude.

Front 229

The electrochemical gradient for sodium ions in a neuron when the transmembrane potential is at the resting potential is caused by what?

Back 229

chemical and electrical gradients both going into the cell

Front 230

In a typical neuron, what is the equilibrium potential for potassium?

Back 230

-90 mV

Front 231

What is the electrochemical gradient of an ion?

Back 231

the sum of the electrical and chemical gradients for that ion

Front 232

The electrochemical gradient for potassium ions when the transmembrane potential is at the resting potential (-70 mV) is caused by what?

Back 232

a chemical gradient going out of the cell and an electrical gradient going into the cell

Front 233

Leak channels allow the movement of potassium and sodium ions by what type of membrane transport?

Back 233

channel-mediated diffusion

Front 234

In a neuron, sodium and potassium concentrations are maintained by the sodium-potassium exchange pump such that __________.

Back 234

the sodium concentration is higher outside the cell than inside the cell and the potassium concentration is higher inside the cell than outside the cell.