EXCITABLE TISSUES Flashcards
integral proteins
- they have hydrophobic and hydrophilic region
- span the membrane- allow passage of ions into and out of the cell.
- carrier proteins or ion channels
peripheral proteins
- loosely bound to the surface of the cell membrane, either on integral protein or polar region of the bilipid layer.
- function- cell adhesion and communication.
- does not span the membrane.
ion channels
- made from integral proteins.
2. channels are either leaked or gated.
leak channel
- ion channel
- always open
- allow passage of Na, K, Ca, and Cl
- ions move down their concentration gradient, from high to low.
gated channel
- ion channel
2. consists of, ligand-gated, mechanically gated, and voltage-gated.
ligand-gated
- gated channel
- can be a chemical messenger
- respond to the binding of a ligand to the integral protein that causes it to open.
mechanically gated
- gated channel
2. respond to vibration, stretch, and pressure
voltage-gated
- gated channel
2. open or close due to change in membrane potential.
unassisted membrane transport
consists of :
1. simple diffusion
2. osmosis
allows small permeable molecules.
assisted membrane transport
consists of : 1. facilitated diffusion 2. active transport 3. vesicular transport impermeable molecules are assisted by integral proteins.
simple diffusion
- transport molecules down their concentration gradient and electrical gradient.
- do not require ATP and carrier proteins.
facilitated diffusion
- requires carrier proteins or ion channels to transport ions down their concentration gradient and electrical gradient.
- does not require ATP.
active transport
- requires carrier proteins or ion channels.
- transport molecules against their concentration gradient.
- requires ATP
- there is primary and secondary active transport.
primary active transport
- NA, K pump
- transport NA against its concentration gradient, from less to more
- transport K against its concentration gradient, outside to inside
secondary active transport
- Na glucose symport transporter
- moves Na down its concentration gradient in doing so it provides energy for glucose to move against its concentration gradient into the cell.
vesicular transport
the active method of membrane transport
- exocytosis
- endocytosis
membrane potential
the difference in charge across the plasma membrane
potential is measured in
millivolts(Mv)
where is sodium greater?
ECF
where is Na greater?
ECF
where is Cl greater?
ECF
where is calcium greater?
ECF
where are proteins greater?
ICF
equilibrium potential
membrane potential at which ion influx and reflux are at electrochemical equilibrium.
potassium equilibrium poteintial
- concentration gradient moves K out of the cell, making the outside of the cell more positive.
- cell membrane is impermeable to anions thus the inside becomes more negative.
- electrical gradient is formed which moves K back into the cell.
- no further movement of K, the membrane is at equilibrium.
- the potential of K is -90 Mv
sodium equilibrium potential
- concentration gradient moves Na into the cell, making the inside more positive.
- outside becomes unbalanced negative charge mostly Cl.
- electrical gradient moves Na outside
- no further movement of Na, the membrane is at equilibrium.
- the potential is +60 Mv
chloride potential equilibrium
-70 Mv
resting membrane potential
the concentration gradient of ions
- K diffuses outside the cell through leak channels
2. Na diffuses inside the cell through leak channels.
resting membrane potential
permeability of the membrane to ions
- small net diffusion of Na inward
- large net diffusion of K outward
- no net movement of Anions across the membrane.
resting membrane potential
the activity of Na K ATPase pump
- moves 3 Na out and 2 K in
2. maintains the concentration gradient
