Neurphysiology: Neurochemistry and Communication by Receptor - Week 8 Flashcards
PHOSPHOLIPID BILAYER
The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules.
These membranes are flat sheets that form a continuous barrier around all cells.
Allows uncharged molecules through.
Plasma membrane around the neuron (nerve cells that send messages to the body).
ION
an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons.
MOLECULE
A group of atoms bonded together.
ATOM
A smallest particle of a chemical element that can exist.
RESTING MEMBRANE POTENTIAL
Is the electrical charge across the neuron’s when it is at rest (-70 mV).
Negative ions, also called anions, are formed in attachment processes in which an additional electron is captured by an atom, molecule, or cluster.
Action potentials are brief electrical impulses that are generated when the membrane potential reaches a certain threshold. These action potentials allow for the transmission of signals along the neuron’s axon.
Resting membrane potential is a result of different concentrations of Na+ and K+ ions inside and outside the cell.
At rest potassium channels are open (will flow in and out).
The resting membrane potential (RMP) is produced by the electrochemical gradient between the intracellular and extracellular fluid bordering the phospholipid bilayer membrane of the neuron
INTRACELLULAR FLUID
Intracellular (inside) fluid: ICF -> high concentration of K+ potassium and low concentration of Na+ sodium
It is approximately 40% of the total body weight. It is the total space within cells primarily defined as the cytoplasm of cells. In general, intracellular fluids are stable and do not readily adjust to rapid changes. This space is where many chemical reactions occur.
EXTRACELLULAR FLUID
Extracellular (outside) fluid: ECF -> high concentration of Na+ sodium and low concentration of K+ potassium
It is the body fluid that is not contained in cells. It is found in blood, in lymph, in body cavities lined with serous (moisture-exuding) membrane, in the cavities and channels of the brain and spinal cord, and in muscular and other body tissues.
The primary function of the ECF is the exchange of substances between the cells and the rest of the body. The fluid acts as a medium for the essential exchange of dissolved gases, nutrients, and electrolytes.
AN ELECTROCHEMICAL GRADIENT
The electrochemical gradient determines the direction that ions will flow through an open ion channel and is a combination of two types of gradients: a concentration gradient and an electrical field gradient.
POSITIVELY CHARGED IONS
Cations: Na+, K+, Ca2+
Na - Sodium - Sodium is a very soft silvery-white metal. It helps maintain normal blood pressure, supports the work of your nerves and muscles, and regulates your body’s fluid balance
K - Potassium - is an essential mineral that is needed by all tissues in the body. It is sometimes referred to as an electrolyte because it carries a small electrical charge that activates various cell and nerve functions
Ca - Calcium - it makes up much of the structure of bones and teeth and allows normal bodily movement by keeping tissue rigid, strong, and flexible.
NEGATIVELY CHARGED IONS
Anions: Cl- (Chloride)
Negative ions, also called anions, are formed in attachment processes in which an additional electron is captured by an atom, molecule, or cluster.
ELECTRICAL GRADIENT
Electrical -> the difference in electrical charge between two adjacent areas. If an area is negative, positive ions will flow to it (positive K+ ions will flow form the outside of the cell, which are more positive charged to the inside , which are more negative.
Is a change in electric potential over a given distance. (e.g., causes K+ to flow in)
CONCENTRATION GRADIENT
Concentration -> the difference in concentration of a particular ion between two adjacent areas. If an area has many K+ ions, the K+ ions will flow to an area with less K+ ions. (e.g., the inside of the cell has more K+ ions than the outside. K+ ions will then cross from the inside to the outside of the cell).
Is the change in concentration of a substance over a given distance. (e.g., causes K+ to flow out).
*At rest, K+ (potassium) channels are open, and potassium flows in and out.
RESTORING THE CHEMICAL POTENTIAL
e.g., sodium potassium (Na+/ K+) pump:
- brings in 2 K+ and removes 3 Na+ ions
-restores chemical potential (greater K+ inside)
-restores electrical potential (greater - charge inside)
-requires energy (ATP).
VOLTAGE GATED CHANNELS
Voltage channels open and close in response to changes in membrane potential.
Ligand-gated ion channels open when a chemical ligand such as a neurotransmitter binds to the protein.
K+ CHANNELS
Open when the neuron is at rest, K+ ions flow into the cell driven by electrical gradient and out of the cell driven by chemical gradient.
Open at equilibrium..
Na+/ K+ PUMPS
Actively such as with energy pump Na+ out of and K+ into the cell on a 3:2 ratio.
Na+ CHANNELS
Only open at limited voltages. Wehn open Na+ will flow into the cell along the chemical and electrical gradient (big influx).
VOLTAGE-GATED CHANNELS
Na+ ion channels and K+ ion channels are not open.
*Would allow K+ ions into and out of the cell, except only when the cell potential is positive (not at rest).
AXON HILLOCK
Is the region of a neuron that controls the initiation of an electrical impulse based on the inputs from other neurons. The electrical part of the electrochemical signal is called an action potential, which begin at the axon hillock.
DEPOLARISATION
Is a process that shifts the electrical charge distribution so that the cell is less negatively charged (more positive).
from -80mV will go up to -65mV
*In this rage the sodium channels are going to open.
*when membrane depolarises, becomes positive inside, then the potassium channels open and the sodium channels close again (because they only open within a threshold) -> following with potassium ions start to flow out then charge comes down again and this will start to become depolarised again, which will move to -50.
HYPERPOLARISATION
When the membrane potential becomes more negative (less positive) at a particular spot on the neuron’s membrane.
From -80mV will go even lower to -95mV
REPOLARISATION
Change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value.
From +30mV (action potential) down to -70mV rest potential
EQUIIBRIUM
Is the reversal potential -> as the potential at which there is no net movement of that ion across the membrane.
NEURON AT REST (-70mV)
When it is not sending an electrical signal. During this time, the inside of the neuron is negative relative to the outside.
At rest, the inside of the neuron is negative due to many proteins and chloride ions, which have negative charge, and proteins cannot leave the neuron.
At rest, inside the neuron there is a high concentration of K+ (potassium) and allow concentration of Na+ (sodium). Outside of the cell is the opposite.
