Unit 1 - Membrane Pysiology

Question 1

All plasma membranes contain:

Answer 1

1. lipids
2. proteins
3. carbohydrates

2-layers of phosolipids
Hydrophilic heads - polar
Hydrophobic tails - nonpolar

Question 2

What substance maintains the fluidity of a plasma membrane?

Answer 2

cholestoral

fluidity allows movement of proteins

Question 3

Peripheral proteins - where

Answer 3

appendages loosely bound to the surface of the membrane

Question 4

Integral proteins

Answer 4

• penetrate the hydrophobic core of the lipid bilayer

- often are transmembranous

Question 5

Who proposed the Fluid Mosaic Model of membrane structure?

Answer 5

S. Singer & G. Nelson in 1972

Question 6

glycolipids

Answer 6

• formed by carbohydrate groups that join with lipids
• on external surface
• function as identity markers

Question 7

glycoproteins

Answer 7

• formed by carbohydrates that join with proteins
• on external surface
• function as identity markers

Question 8

Functions of Cell Membranes

Answer 8

1. regulate passage of substances into & out of cell & between cell organelles & cytosol
2. detect chemical messengers arriving at surface
3. link adjacent cells together by membrane junctions
4. anchor cells to EC matrix

Question 9

Major functions of proteins in plasma membrane:

Answer 9

1. transport solutes across membrane
2. enzymatic activity
3. signal transduction
4. cell-to-cell recognition
5. intercellular joining
6. attachment to cytoskeleton & ECM

Question 10

osmotic pressure

Answer 10

• a “pulling” pressure
• measure of a tendency for flow of water into a solution b/c of its relative concentration of non penetrating solutes & water

Question 11

hydrostatic pressure

Answer 11

• pressure exerted by a standing (or stationary) fluid on an object.
• when osmotic & hydrostatic pressure are equal, osmosis will stop

Question 12

hyperpolarization

Answer 12

a change in a cell’s membrane potential that makes it more negative. It is the opposite of a depolarization.

Question 13

tonicity

Answer 13

measure of whether water will enter or leave a cell

Question 14

What contributes to the Resting Membrane Potential (RMP)?

Answer 14

1. 20% - Na+/K+ pump
2. 80% - membrane’s great permeability (Pk+) to K+
   - non-diffusibility of proteins (A-)
   [diffusion!]

Question 15

Na+/K+ pump

Answer 15

• pumps 2 Na+ out & brings in 2 K+ cells

- unequal pumping makes outside of cell more positive than inside

Question 16

Nernst Equation

Answer 16

• calculates Equilibrium Potentials for cells

* E = 61 * log [concentration of outside/concentration of inside)

Question 17

Equilibrium Potential of:

1. Na+
2. K+

Answer 17

1. +61 mv

2. - 90 mv

Question 18

Where are leak channels found on a neuron?

Answer 18

cell body
dendrites
axon
They operate at resting membrane potential

Question 19

Where are CHEMICALLY GATED channels found on a neuron?

Answer 19

cell body
dendrites
They operate during a graded potential.

Question 20

Where are VOLTAGE-GATED channels found on a neuron?

Answer 20

axon

They operate during an action potential.

Question 21

suprathreshold stimulus

Answer 21

Is stronger than the threshold stimulus

Question 22

subthreshold stimulus

Answer 22

a stimulus that fails to take the MP to the TP

Question 23

Characteristics of voltage-gated Na+ channels

Answer 23

1. found along axon
2. important for action potential
3. opened and closed gates

Question 24

What are the states that a VG Na+ channels could be in?

Answer 24

1. inactivated, but capable
2. open/activated
3. inactivated & incapable

Question 25

What channels are open when the membrane is at -70 mv?

Answer 25

only leak channels

Question 26

polarization

Answer 26

any time there is a - or + charge on a membrane

Question 27

depolarization

Answer 27

membrane becoming less negative, as in an action potential

Question 28

repolarization

Answer 28

the cell becoming more negative as it re-establishes the polarization of its membrane

Question 29

hyperpolarization

Answer 29

membrane becoming more polarized; the inside becoming more negative than at its RMP

Question 30

Which cells form the myelin sheath in the: PNS? CNS?

Answer 30

PNS - Schwann cells | CNS - oligodendrocytes

Question 31

Two types of synapses. Which is there more of?

Answer 31

1. Electrical - charge carrying ions pass between them. 2. Chemical - chemical messenger transmits information one way 95% of synapses are CHEMICAL

Question 32

EPSP

Answer 32

Excitatory Post-Synaptic Potential | - due to increased Na+ permeability

Question 33

IPSP

Answer 33

Inhibitory Post-Synaptic Potential | - due to increased K+ or Cl- permeability

Question 34

GABA

Answer 34

- the brains main's inhibitory neurotransmitter | - Gamma amino butyric acid

Question 35

grand postsynaptic potential (GPSP)

Answer 35

a composite of all EPSPs and IPSPs occurring around the same time

Question 36

temporal summation

Answer 36

Caused by increasing the number of action potentials on an axon in a given period of time

Question 37

spatial summation

Answer 37

Increasing the number of synapses from different neurons

Question 38

absolute refractory period

Answer 38

- Caused by closure & inactivation of the VG Nq+ channels that opened to depolarize the membrane.