Chapter 6

Front 1

•Blood brain barrier surrounds the

Back 1

CNS only

Front 2

Cerebrospinal fluid is only in

Back 2

the CNS

Front 3

Astrocytes, oligodendrocytes, microglia, and ependymal cells only in the

Back 3

CNS

Front 4

Schwann cells only in

Back 4

PNS

Front 5

Receive information (stimuli) from other neurons or from the chemical or physical environment.

Back 5

Dendrites

Front 6

Integrates information, decides whether the neuron will respond (produce an action potential)

Back 6

initial segment

Front 7

transmits information to distant sites

Back 7

axon

Front 8

Delivers information to targets - other neurons, muscles, organs, etc. Can make a synapse with other cells, or release chemicals into the ISF

Back 8

axon terminals

Front 9

a system of barriers and transport mechanisms that control passage of molecules between the blood and extracellular fluids of the brain

Back 9

the blood brain barrior

Front 10

between endothelial cells lining capillaries in the brain form the barrier

Back 10

tight junctions

Front 11

help to maintain the junctions and prevent leakages

Back 11

astrocyte endfeet

Front 12

is a fatty sheath that consists of many layers of cell membrane wrapped around axons

Back 12

Myelin

Front 13

form the myelin sheath on PNS axons

Back 13

Schwann Cells

Front 14

form the myelin sheath on CNS axons

Back 14

• Oligodendrocytes

Front 15

functions to insulate the electrical activity of axons and greatly increase the speed of action potential conduction

Back 15

Myelin

Front 16

Produced from the blood by ependymal cells in the choroid plexuses

Back 16

cerebrospinal fluid

Front 17

cells form the CSF-blood barrier

Back 17

Chroid Plexus

Front 18

functions of cerebral spinal fluid

Back 18

protection, waste and nutrient transport

Front 19

bring sensory information to the CNS

Back 19

afferent neurons

Front 20

take information from the CNS

Back 20

efferent neurons

Front 21

in the CNS integrate information and make decisions . About 90-95% of our neurons are

Back 21

interneurons

Front 22

grey matter contains cell bodies and

Back 22

dendrites

Front 23

white matter contains

Back 23

myelinated axons

Front 24

The PNS is divided into the ________ nervous systems.

Back 24

somatic and autonomic

Front 25

gives excitatory input to skeletal muscles, causing them to contract

Back 25

somatic nervous system

Front 26

modulates the activity of everything else - modulation can be excitatory or inhibitory

Back 26

autonomic nervous system

Front 27

NS can be further divided into the sympathetic division and the parasympathetic division

Back 27

autonomic

Front 28

Know the major branches, their properties, organization, neurotransmitters used, etc. Read pages 178-184

Back 28

.

Front 29

The inside of the cell is about ______ relative to the outside. The cell is polarized

Back 29

-70 mV

Front 30

-70mV is called the _____ (the potential at which the cell is at rest with no external inputs)

Back 30

resting potential

Front 31

• It is the________ forces that determines what direction an ion will move across a membrane

Back 31

balance of chemical and electrical

Front 32

The major ions involved in bioelectricity are

Back 32

Na +, K + , Ca2+, and Cl-.

Front 33

Membranes in a cell are always leaky - they always have some ion channels open. These are often called

Back 33

leak channels

Front 34

(when a cell is stable at its resting potential), the leakage of Na+ and K+ ions through the membrane is equal to the rate of transport by the Na+/K+ pump

Back 34

equilibrium

Front 35

Flow of ions through a membrane is called a

Back 35

current

Front 36

refers to the development of a charge reversal.

Back 36

overshoot

Front 37

movement back toward the resting potential

Back 37

repolarization

Front 38

A cell is ____ because its interior is more negative than its exterior.

Back 38

polarized

Front 39

occurs when ion movement reduces the charge imbalance

Back 39

depolarization

Front 40

is the development of even more negative charge inside the cell

Back 40

hyperpolarization

Front 41

Caused by input (stimuli) to the cell – vary in amplitude • Can be depolarizing or hyperpolarizing, and vary in size. • Get smaller with distance (degrade). • Can be summated (added together).

Back 41

graded potentials

Front 42

Triggered when graded potentials summate to reach threshold. • Are always depolarizing (with a small hyperpolarizing part at the end). • Do not get smaller with distance. • Are "all or none" – one size only.

Back 42

action potentials

Front 43

Graded potentials can be

Back 43

EXCITATORY or INHIBITORY

Front 44

The size of a _____ varies with the size of the stimulus that produced them: bigger stimulus = bigger potential

Back 44

graded potential

Front 45

decay as they move over distance

Back 45

graded potential

Front 46

are triggered at certain sites in cells (usually on the dendrites) where they receive stimuli from other cells or the environment, and they spread from there in all directions through the cell

Back 46

graded potentials

Front 47

The size of a graded potential decreases with distance from the stimulus (it decays), because some of the current leaks out of the membrane through

Back 47

leak channels

Front 48

Graded potentials are summed by the cell, and this information determines if the cell generates an

Back 48

action potential

Front 49

Sign (+/-) of a graded potential, strength of the stimulus, and distance of the stimulus from the initial segment all determine whether an

Back 49

action potential can be formed

Front 50

describes graded potentials that add together because they are close in time (they only last a short time)

Back 50

temporal summation

Front 51

describes graded potentials that add together because they are close in space (on the dendrites of the cell)

Back 51

spatial summation

Front 52

• If the graded potentials sum to reach threshold, an

Back 52

action potential is formed

Front 53

occur as a result of some external signal triggering a sensory neuron

Back 53

receptor potentials

Front 54

are produced if graded potentials sum up to reach threshold for the cell. Once produced, they pass down the axon of the neuron and trigger output at the axon terminals

Back 54

action potentials

Front 55

• Graded potentials that do not produce action potentials are called

Back 55

subthreshold potentials

Front 56

• Are all or none: there is one size, they do not sum to make bigger or smaller action potentials, and they do not change with stimulus size. • Are regenerating, so they stay the same size as they pass down an axon. • Only go in one direction

Back 56

action potentials

Front 57

are due to the opening and closing of voltage gated ion channels (open in response to a certain electrical potential in the cells)

Back 57

action potentials

Front 58

Voltage gated Na+ channels open at

Back 58

-55 mV

Front 59

channels open at the peak of the action potential

Back 59

potassium

Front 60

Closing is quite slow. •Voltage gated K+ channel closing is a

Back 60

negative feedback mechanism

Front 61

• Opening of voltage gated Na + channels is an example of

Back 61

positive feedback

Front 62

is the time during which it is either impossible or much more difficult for a cell to fire a second action potential

Back 62

refractory period

Front 63

is the time during which an action potential is being generated. It is impossible to form a second action potential

Back 63

absolute refractory period

Front 64

is the time during which the after hyperpolarization lasts. It is harder to form a second action potential because a greater depolarization is required to reach threshold

Back 64

relative refractory period

Front 65

is formed from many layers of oligodendrocyte or Schwann cell membrane wrapped around an axon

Back 65

myelin sheath

Front 66

•Spread of current through a cell is not due to diffusion, it is due to

Back 66

shift of charge

Front 67

is activated when an action potential opens voltage gated Ca2+ channels

Back 67

synapse

Front 68

The strength of a synapse (size of the graded potential in the post synaptic cell) can be increased or decreased by many mechanisms.

Back 68

Changing the amount of neurotransmitter released. •Changing the numbers or properties of the postsynaptic receptors. •Changing other properties of the postsynaptic cell (e.g. leakiness)

Front 69

two major ways of changing synaptic strength by changing the amount of transmitter released.

Back 69

Autoreceptors and pre-synaptic inputs

Front 70

can pass directly through gap junctions, from one cell to another

Back 70

action potentials

Front 71

Change how the cell receives information

Back 71

dendrites

Front 72

Change how the cell integrates information

Back 72

initial segment

Front 73

Change how the cell delivers information

Back 73

axon terminals