Communication, Integration, Homeostasis

Question 1

Cell to cell communication(short distance)

Answer 1

Gap junctions, juxtacrine (contact dependant), autocrine and paracrine

Question 2

2 key control systems

Answer 2

Endocrine and Nervous

Question 3

Gap juctions

Answer 3

channels that produce a direct pathway between cytoplasm of one and another cell, for electrical or chemical signals
- Direct cytoplasmic transfer

Question 4

Contact dependant

Answer 4

Juxtacrine: one end is stuck in the membrane of one cell and receptor is stuck in another cells membrane. They have to come in contact with receiving cell.
- cell to cell dependant

Question 5

Autocrine

Answer 5

Cell is signaling itself, same cell releases signal and bind to receptor on the same cell
- release signal

Question 6

Paracrine

Answer 6

Release signal to neighboring cell and binds

- release signal

Question 7

communication via long distance: hormone

Answer 7

hormone: endocrine cells
released by endocrine cells and travels through the blood to target cells. Target cells need to have correct receptors to be activated

Question 8

communication via long and short distance: neurons

Answer 8

use local and long distance. Neurons secrete signals = neurocrines
1- neurohormone: transported like hormone, through the blood
2- neurotransmitter: something secreted by neuron into neighboring cell
3- neuromodulator: substances released by neurons, modifies how neuron responds to normal primary signal

Question 9

Electrical signaling

Answer 9

Excitable cells use e- signals for communication
ex; nerves, muscles, some endocrine cells.
- due to changes in membrane potential. [ difference in charge is only along the membrane]

Question 10

Membrane potential

Answer 10

All cells have it
electrical potential difference = Vm = voltage = stored energy
** reported inside relative to outside. Use absolute value when determining the largest potential difference

Question 11

How do membrane potentials arise?

Answer 11

1- unequal distribution of ions

2- selective membrane permiablity

Question 12

Chemical (diffusional ) forces

Answer 12

Concentration of gradient principle, ECF vs ICF

Question 13

Electrical force

Answer 13

ionic charge vs membrane charge

Question 14

electrochemical equilibrium

Answer 14

= no net electrochemical force

- 2 forces(chemical and electrical) are equal but opposite = equilibrium potential.

Question 15

Nerst equation, what you need to know

Answer 15

Nerst = Eion = 61/z *( [ion]out/[ion]in)
Z= valence electrons, if anion use a (-)
log(#>1)= +
log(1)= 0
log(#<1)= -

Question 16

Ex of different Ions

Answer 16

k+ = -90mv
Na = +60 mV
Cl- = -63 mV
Ca+ = +240

Question 17

Membrane potentials influenced by equilibrium potentials

Answer 17

due to multiple ions
reality of how much charge is unequally distributed.
unequeal distributions give us ion equilibrium potentials(Ex).

Question 18

Equilibrium potentials

Answer 18

each ions desired value.

- ions want to move Vm towards ions Ex to be at equilibrium.

Question 19

What is the driving force?

Answer 19

Membrane potential - Equilibrium potential = driving force

(Vm-Ex) = determines ion flow in/out of a cell

Question 20

Membranes permeability to certain ions

Answer 20

Leakage (open), but a small drop in the ocean

K+>Cl->Na+, K+ has more votes

Question 21

Resting membrane potential equation

Answer 21

Vm = pK(Ek)+ pNa(Ena) + pCl(Ecl)
Px = permeability

Question 22

How are concentration gradients maintained over time?

Answer 22

Active transporters, Like the Na+/K+ ATPase. 3 Na for 2K, always running and controls the “leak” of potassium

Question 23

types of gated channels

Answer 23

chemically  gated: 
1- ligand(lock and key)
2- ATP channel (Na/K)
Voltage: activated by depolarization
Mechanically gated: Activated with stretch or pressure

Question 24

How can changes to a membrane’s permeability depolarize or hyperpolarize a cell?

Answer 24

ion channels display specificity and allow rapid flow of ions
- ions flow to change membrane potential of cell (Vm) towards their equilibrium potential(Ex)

Question 25

Depolarize vs repolarize vs hyperpolarize

Answer 25

Depolarize; making more positive(|Vm decreases|)
Repolarization; returning, making more negative
hyperpolarization; too negative, pass the threshold.
|Vm increases|

Question 26

What does chemical signaling rely on?

Answer 26

ligand- receptor interactions
ligand- ex, insulin
receptor: have binding sites for ligand (specificity, competition, saturation)

Question 27

intracellular vs vs membrane receptors

Answer 27

intracellular: lipophilic, hydrophobic
membrane: lipophobic, hydrophilic,

Question 28

Lipophobic receptors:

Answer 28

receptor channels: simplest, most rapid (neurotransmitter) ** confused based on the learning goals

Question 29

GPCR

Answer 29

Most signal transduction uses GPCR

• membrane-spanning protein
• extracellular binding sites
• cytoplasmic tail linked G protein (3 parts to it)
• when activated, they can open ion channels, or alter enzyme activity inside cell [ protein kinase/phosphatases (amplifier enzymes).]

Question 30

What is amplification?

Answer 30

allows a small amount of signal to have a large effect.
2 most common amplifier enzymes:
-adenylylcyclase
- phospholipase C

Question 31

Step one of cAMP

Answer 31

ligand (1st messenger) binds to GPCR.
- G-protein activated -> exchanges GDP for GTP.
functions like molecular switch
-GTP = active
- GDP = inactive

Question 32

step 2 of the cAMP

Answer 32

activated G Protein activates adenylyl cyclase

- adnyl cyclase converts ATP => cyclic amp(secondary messenger)

Question 33

step 3 of cAMP

Answer 33

cAMP activates protein kinase A and then that has multiple functions

Question 34

What does protein kinase A do?

Answer 34

cAMP dependant, can influence many factors, including opening ion channels and regulating gene transcription.

Question 35

What stops the cAMP pathway?

Answer 35

G protein: GTPase: converts GTP back to GDP
cAMP:phosphodiesterase: breaks down cAMP
Protein kinase A:phosphatases, unphosphorylated things

Question 36

Phospholipase C pathway

Answer 36

• instead of adenylyl cyclase there is phospholipase C.
• instead of cAMP, there is DAG and IP3
• -> DAG is made from membrane phospholipids and then continues to protein kinase C on the membrane
• -> IP3 activates Ca+ storage

Question 37

can receptors have more than one ligand?

Answer 37

yes;

ex; adrenergic receptors bind to both epinephrine and norepinephrine, ligands compete

Question 38

endogenous

Answer 38

into, from within. something that is provided from within the body

Question 39

exogenous

Answer 39

drugs, come from the outside that can also bind to receptors. They block activity.

Question 40

upregulation vs down regulation

Answer 40

upregulation: mechanism to increase cell response, increase # of receptors
downregulation: mechanism to decrease cell response
decrease # of receptors or binding affinity or receptors

Question 41

Antagonistic vs tonic control

Answer 41

antagonistic is faster, both branches(S7P) are active

tonic = volume dial

Question 42

how is a signaling molecule turned off?

Answer 42

• degrade/inactive signal (1st or 2nd messenger): GTPase or phosphodiesterase
• remove signal: 1st or second mess, by transporting it, ex; pumping Ca+ back into ER
• endocytosis of receptor-ligand complex.