Excitable Cells and muscles Flashcards
Typical concentrations of Na, k and Cl inside the cell
Na = 15mM K = 150mM Cl = 5mM
Typical concentrations of Na, K and Cl outside the cell
Na = 145 mM K = 5mM Cl = 100mM
Kinetics of voltage gated sodium channels
Rapid opening triggered at threshold
Slow closing triggered at threshold
Kinetics of voltage gated potassium channels
Delayed opening triggered at threshold
Movement of ions at resting state
2 K+ in
3 Na+ out
Via sodium-potassium exchange pump
ATP used to do so
Describe ligand gated ion channels
Neurotransmitters bind
Channel opens
Ions flow in
Describe G protein coupled receptors
Neurotransmitter binds
G protein activated
G protein subunits or intracellular messengers modulate ion channels
ion channel opens ions flow across membrane
Protein acts as a regulator
Sources of ATP in muscle
- Dephosphorylation of phosphocreatine
- Glycolysis
- Oxidation of glucose/glycogen
- Oxidation of free fatty acids
Titanic fusion frequency
Frequency of action potential delivery to enable smooth muscle contraction
What does RT stand for in a length tension curve
Resting tension
What does TT stand for in a length tension curve
Total tension
What does AT stand for in a length tension curve
Active tension
Describe cardiac muscle stretch resistance
- Has higher resistance to stretch then skeletal muscle
- High abundance of connective tissue prevents muscle rupture and over stretching
Frank-Starling law
- Stretching occurs at times of increased venous return
- force of contraction is increased by stretch and by sympathetic contraction
- helps heart pump whatever volume of blood it receives
Important mechanism
Chronotropy
Rate of contraction
Inotropy
Force of contraction
Luistropy
Ability to relax
Affect of epinerphrine and norepinephrine on cardiac excitation contraction
Bind to andonergic receptors that set of signalling pathways in the cell that allow calcium to be pumped back into the cell and stimulate Ryr
What are important proteins in the myofilaments of cardiac muscle
Scaffolding proteins
Elastic protein Titin: prevents overstretching and may also serve as signalling role as a stretch sensor. When calcium levels go down you get passive relaxation that titin aids with
Where is smooth muscle located
Internal organs
Walls of blood vessels
Around hollow organs
Layers around respiratory, circulatory, digestive and reproductive tracts
What are the functions of smooth muscle
Move food, urine and reproductive tract secretions
Control diameter of respiratory pathways
Regulate diameter of blood vessels
What is the structure of smooth muscle
Spindle Shaped Single nucleus Not strained Smooth muscle fibres often embedded in matrix of connective tissue and arranged in parallel with one another 100-300 um long 2.5 um wide
What is multi unit smooth muscle
Each individual cell responds on its own. Needs to receive neurotransmitter
What is single unit smooth muscle
Gaps junctions = propagation.
