chapter 3

Question 1

membrane potential defintition

Answer 1

• plasma membrane- of all living cells has a membrane potential ( polarized electrically )
  -separation of opposite charges across the plasma membrane ( across ICF and ECF)
• electrical potential difference across the plasma membrane when the cell is in a non-excited state.
• responsible for signal transmission

Question 2

key ions :

Answer 2

sodium ( Na+) - ECF/ 15-75X more permeable
potassium ( K+) - ICF/ low permeability ( needs excitation)

Question 3

other ions :

Answer 3

( don’t move often )
chloride ( CL-)
Bicarbonate (HCO3)
larger ions and proteins ( A-)

Question 4

when at membrane potential is at rest :

Answer 4

-constant membrane potential is present in cells of NON-EXCITABLE tissues
-The resting membrane potential (electrochemical equilibrium) is typically –70 mV on the inside.

Question 5

nerve and muscle cells

Answer 5

excitable cells, have the ability to produce rapid and transient changes in there membrane potential when excited

Question 6

effects of a sodium-potassium pump on membrane potential:

Answer 6

-makes a contribute through its unequal transport of positive ions
-maintains equilibrium

Question 7

role of the Na + and K+ pump

Answer 7

ongoing role of stabilizing the membrane potential and equilibrium

Question 8

factors of the Na+ and K+ pump

Answer 8

ratio 3:2
primary active transport ( needs ATP)
restores the membrane
higher to lower

Question 9

various changes in the membrane potential

Answer 9

-polarization - any state when the membrane potential is other than 0mv
-depolarization- the membrane becomes less polarized than at the resting potential
- depolarization- the membrane returns to its resting potential
- hyper polarization- the membrane becomes more polarized than at the resting potential

Question 10

two different types of electrical signals

Answer 10

graded potential and action potential

Question 11

graded potenial

Answer 11

local changes in the membrane potential that occur varying grades or degrees of magnitude or strength
occurs in small, special regions of the membrane
short distance
few mm
local current flow
leaks - decremental
cytoplasmic resistance
depends on the amplitude of the stimulus

Question 12

examples of graded potential

Answer 12

postsynaptic potential ( PSP)
receptor potential
end-plate potentials ( EPP)
pacemaker potentials

Question 13

action potential

Answer 13

when the membrane reaches the threshold potential
flow of the sodium ions move into the ICF, reverses the membrane potential from -70Mv to +30 Mv
flow of the potassium ions move into the ECF and restore the membrane potential to resting state
“positive feedback” - childbirth
double gating sodium channels

Question 14

factors of action potential

Answer 14

rising phase- increasing the movement of Na+ ions [ influx] INTO the cell
permeability change or P Na+ influx ( peak)
peaks at 30Mv ( the P Na+ decreases) ( the P K+ increases)
P K+ increases [ efflux ] - leaves cells
goes to rest - brief , rapid, large, 100Mc change
positive feedback - Na+ channels open
double gating of Na+ channels
( 1) leak or 2) gated channel)

Question 15

activation gates of sodium channels

Answer 15

rising phase
closed at rest and opens after the state of depolarization
allows influx of sodium

Question 16

inactivation gates of sodium channels

Answer 16

stops the flow of sodium
falling phase

Question 17

refractory periods

Answer 17

all-or-none principle
current flow is ALWAYS unidirectional
( stubborn)
periods of time following an action potential
marked by decreased excitability
two refractory periods

Question 18

absolute refractory period

Answer 18

spans all of the depolarization and most of the repolarization phase
second action potential cannot be generated
sodium gates are inactivated
Na+ CLOSE
K+ OPEN

Question 19

relative refactory period

Answer 19

• stimulus needs to be strong
  spans last part of repolarization phase and hyperpolarization
  sodium gates closed
  few potassium channels still open
  Na+ REST
  K+ FEW

Question 20

3 parts of a neuron

Answer 20

cell body - typical cell

dendrites- input zone ( unique )

axons -
* axon hillock- input zone
* conducting
* axon terminal- output zone

Question 21

myelinated fibers

Answer 21

• provide info from the CNS to the PNS
  ** primary composed of lips
  formed by oligodendrocytes in CNS
  formed by Schwann cells in PNS

Question 22

unmyelinated fibers

Answer 22

known as the nodes of the Ranvier
C-fiber
highly composed of Na+ and K+ channels
larger diameter- faster conduction

Question 23

multiple sclerosis

Answer 23

losing myelin/disintegrating myelin
extreme weakness and fatigue
difficulty walking- wheelchair bound
loss of vison

Question 24

2 types of propagation- action potential

Answer 24

contiguous conduction ( to touch )
saltatory conduction ( to jump )

Question 25

contiguous conduction -

Answer 25

in unmyelenated fibers
action potential spreads along every portion of the membrane

Question 26

saltatory conduction

Answer 26

in myelinated fibers
impulse jumps over sections of the fibers covered with insulating myeline
travels/conducts 50X faster

Question 27

signal transduction at synapses

Answer 27

excitatory synapses
EPSP
Na+ = influx
K+= efflux

inhibitory synapses- hyperpolarization
IPSP
K+ efflux- leak
Cl- influx- more negative

synaptic delay
time interval between peak of inward current through the presynaptic membrane and commencement of inward current through the postsynaptic membrane.

Question 28

neural summation

Answer 28

a) temporal summation
- “ in the time it adds “
b) spatial summation
- “ in space “

Question 29

effects of cocaine

Answer 29

COCAINE
Cocaine BLOCKS the reuptake of the neurotransmitters - dopamine
Does so by binding with the neurotransmitters- the cocaine is occupying the transporter, dopamine remains in the synaptic cleft longer than usual & continues to interact with its post-synaptic receptor sites
Cocaine is addictive because it can cause all the neurons involved to generate long term molecular adaptions- such that they cannot transmit normally across synapse without increasing higher doses of the drugs

Question 30

parkinsons

Answer 30

PARKINSONS
PD- is the deficiency of dopamine in the BASAL NUCLEI - a region in the brain involved in controlling complex movements
Characterized by muscular rigidity & involuntary tremors
Leva dopa ( L- dopa) - a precursor of dopamine
Dopamine itself cannot be administered because it is unable to cross the blood- barrier , but L- Dopa can enter the brain through blood
Once inside the brain- L- dopa can be converted into dopamine - thus submitting for the neurotransmitter

Question 31

paracrine, autocrine

Answer 31

paracrine- Acts on nearby cells- adjacent cells

autocrine- Acting on surface receptors of the same cell

Question 32

neurocrine

Answer 32

1) Neurotransmitter- chemical substance released at the end of a nerve fiber- by diffusing across membrane
2) Neuromodulators (are primarily neuropeptides)- transmission of a nerve impulse- do not directly activate - but work together
3) Neurohormone- produced by nerve cells- pass along axons and are released into the bloodstream

Question 33

cytokines and hormones

Answer 33

Cytokines
Immune response; cell differentiation
eg/ INTERLUKIN-1
L-1 is used for fever response

Hormones
Small amounts: into blood: targets with receptor