a tissues ability to generate and respond to electrical signals
what is the most abundant tissue in the body
what are cells linked by
think about the types
Gap junctions-simplest for fast cell to cell communication (liver, pancreas, ovaries, etc)
Tight junctions- restrict movement between the cells that they link (intestinal tract, kidneys, etc)
Anchoring junctions- attach cells together
how much of the body weight is water?
is 2/3 of that water in the ECF or the ICF?
What separates the two?
selectively permeable plasma membrane
In the 1/3 of body's water in the ECF how much of it is interstitial fluid and how much is plasma?
what separates the two?
80% is interstitial fluid, 20% is plasma
separated by a blood vessel wall
What ions are usually found in the ICF? ECF?
ICF: K+, Pr-, Na+, Cl-, Ca+
ECF: Na+, Cl-, Ca++, K+, Pr-
What is homeostasis?
Where is this goal taking place?
keeping a relatively stable internal environment even when the external environment changes
the goal is to keep the ECF regulated and maintained
What are some regulation variables for homeostasis?
temperature, PH, gases, nutrients, electrolytes, wastes, blood, pressure, etc.
when variables are maintained within very narrow limits, what are those variables called?
what detects the changes in set points and regulated variables?
what do they do? what are the 2 types
they create feedback loops
positive and negative
what is negative feedback?
what are the 2 types? explain each
Negative feedback: makes a change in the opposite direction from which the original disturbance came to bring it back to a normal level.
extrinsic: central nervous system or endocrine system
intrinsic: occurs when a cell/tissue detects a chance in the environment and responds
what is positive feedback and does it happen often?
NO, it is very rare. it pushes variables awar from their set point moving it away from homeostasis
functionally, what are the 3 fluid compartments of the body
the ICF, ECF, and cell membrane
what is the 4 main purposes of the cell membrane
1. to be a physical barrier between the ICF and ECF
2. to control exits and entries
3. to communicate between the cell and its environment
4. provides structural support
what are cell/plasma membranes primarily made up of? which is more abundant (there are 3 main)
what is there also a little bit of
lipids and proteins
Lipids: most abundant, acts as a barrier called phospholipids. the polar hydrophilic heads are on the outside and the fatty acid, nonpolar tails are on the inside
Proteins: act as transporters via channels that connect with ICF and ECF by different types of gates and via carriers that never connect with the ICF nor ECF, instead they undergo confirmational changes
Carbohydrates: small amounts found on ECF for cells to use as identification markers
what are the 3 types of transport across the cell membrane?
what are the 2 gradients that happen by passive transport?
explain each, what causes them?
What else is considered passive transport?
1. concentration gradient- difference in concen. between the ICF and ECF.
It goes from high to low concentration, allowed by Brownian motion
Brownian motion: all substances are in constant motion above 0 degrees Kelvin
2. Electrical gradient- difference in charge between 2 areas
-like charges repel
-opposite charges attract
What is a cell at rest?
what is resting membrane potential?
A cell at rest is negative on the inside of the ICF and positive in the ECF
charge across a membrane for a cell at rest
what are the 2 types?
-can happen down a concen. gradient of an electrical gradient
1. simple- non-mediated, can move through a channel or lipid bilayer on its own
2. facilitated-mediated because it needs a carrier
-competitive (and inhibitor)
when does net movement stop?
what makes it faster? what law is this?
when it reached dynamic equilibium
higher concentration gradients
more lipid soluble molecules
more membrane permeability (surface area)
ficks law of diffusion
What are characteristics of active transport?
what 2 kinds are there?
requires energy input, moves substances across a concentration gradient, always mediated (with a carrier)
primary- uses ATP as ATPases (sodium potassium pump) pumps in 2 K+ while pumping out 3 Na+
-is considered electrogenic because it causes a charge
secondary-uses kinetic energy stored in the concentration gradient. When Na+ moved down its concentration gradient it can take Glucose with it (think of the lock and key model. Na+ can change the lock's confirmation for different transporters).
What is vesicular transport?
2 main types
vesicles are created when there are too many big particles, to move in and out of the cell
Endocytosis- membrane engulfs particle and forms a vesicle to bring it inside of the cell
Exocytosis- extracellular vesicles fuse with the membrane to release contents to the outside
What is osmosis
the movement of water across a cell membrane in response to the solute concentration gradient
what is osmotic pressure
the pressure on a piston that exactly opposes the osmotic movement of water into compartment B
what is iso, hypo, and hyper osmotic
isosmotic- if the is the same number of solutes on the inside and outside of the cell
hyperosmotic- there are more solutes on the outside of the cell than the inside of the cell
hyposmotic- there are more solutes inside the cell than outside the cell
what is iso, hypo, and hyper tonic
isotonic- if the cell does not change in size when places in water
hypotonic- if the cell swells or lyses when placed in water
hypertonic- if the cell shrinks and loses water
osmolarity vs tonicity
osmolarity is referring to the number of particles inside or outside of the cell (osmoles of solute per kilogram of water)
tonicity how the solution effects the cell volume or shape of the ell
what is crenation?
when a cell is hypertonic, it shrinks and gets the ridges along its edges
what is lysing?
when a cell is hypotonic and swells, but swells too much and bursts
what is resting membrane potential
the potential at which the membrane stabilizes
its the difference in charge across the cell membrane
describe a cell at rest
what ion is it most permeable to? why?
Negative charge on the inside of the cell, positive charge on the outside of the cell
K+ because of K+ leak channels
the relative measurement of the electrical gradient between the ICF and the ECF