Communication, Integration, Homeostasis Flashcards
Cell to cell communication(short distance)
Gap junctions, juxtacrine (contact dependant), autocrine and paracrine
2 key control systems
Endocrine and Nervous
Gap juctions
channels that produce a direct pathway between cytoplasm of one and another cell, for electrical or chemical signals
- Direct cytoplasmic transfer
Contact dependant
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
Autocrine
Cell is signaling itself, same cell releases signal and bind to receptor on the same cell
- release signal
Paracrine
Release signal to neighboring cell and binds
- release signal
communication via long distance: hormone
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
communication via long and short distance: neurons
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
Electrical signaling
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]
Membrane potential
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
How do membrane potentials arise?
1- unequal distribution of ions
2- selective membrane permiablity
Chemical (diffusional ) forces
Concentration of gradient principle, ECF vs ICF
Electrical force
ionic charge vs membrane charge
electrochemical equilibrium
= no net electrochemical force
- 2 forces(chemical and electrical) are equal but opposite = equilibrium potential.
Nerst equation, what you need to know
Nerst = Eion = 61/z *( [ion]out/[ion]in) Z= valence electrons, if anion use a (-) log(#>1)= + log(1)= 0 log(#<1)= -
Ex of different Ions
k+ = -90mv Na = +60 mV Cl- = -63 mV Ca+ = +240
Membrane potentials influenced by equilibrium potentials
due to multiple ions
reality of how much charge is unequally distributed.
unequeal distributions give us ion equilibrium potentials(Ex).
Equilibrium potentials
each ions desired value.
- ions want to move Vm towards ions Ex to be at equilibrium.
What is the driving force?
Membrane potential - Equilibrium potential = driving force
(Vm-Ex) = determines ion flow in/out of a cell
Membranes permeability to certain ions
Leakage (open), but a small drop in the ocean
K+>Cl->Na+, K+ has more votes
Resting membrane potential equation
Vm = pK(Ek)+ pNa(Ena) + pCl(Ecl) Px = permeability
How are concentration gradients maintained over time?
Active transporters, Like the Na+/K+ ATPase. 3 Na for 2K, always running and controls the “leak” of potassium
types of gated channels
chemically gated: 1- ligand(lock and key) 2- ATP channel (Na/K) Voltage: activated by depolarization Mechanically gated: Activated with stretch or pressure
How can changes to a membrane’s permeability depolarize or hyperpolarize a cell?
ion channels display specificity and allow rapid flow of ions
- ions flow to change membrane potential of cell (Vm) towards their equilibrium potential(Ex)