פיזיולוגיה Flashcards
What happens to Ca2+ during muscle contractions?
1. Transport back to t-tubule by SERCA
2. Increase in Ca2+ from RYR
3. AP moves along the t-tubule and affects SR
4. AP moves along SR and affects the t-tubule
- Increase in Ca2+ from RYR
When AP arrives in SR and spreads towards the t-tubules, Ca2+ is released from the cistern terminal of the SR via RYR receptor into the myoplasm. this allows binding of Ca2+ to troponin which moves the topomyosine from the binding sites of myosin on top of actin filaments which results in contraction of the sarcomere
What is Paired Pulse Facilitation (PPF) ?
PPF- a form of short term synaptic plasticity where there is an enhancement in the amplitude of the second of two rapidly evoked excitatory postsynaptic potentials (EPSPs). this is enabled by residual intraterminal free [Ca(2+)] from the first action potential facilitates the probability of transmitter release evoked by the second stimulus.
What does Dynamin do?
A protein of type GTPase that is involved in the receptor mediated endocytosis process. specifically, it participates in detaching fused vesicles from the membrane into the cell
What is the role of Desmin?
Desmin is a muscle-specific, type III intermediate filament, that integrates the sarcolemma, Z disk, and nuclear membrane in sarcomeres and regulates sarcomere architecture
Neuronal repolarisation is possible through which mechanism?
1. Na+/K+ pump (ATP driven)
2. Voltage gated NA+ channels
3. Voltage gated K+ channels
4. Antiporters
- Na+/K+ pump (ATP driven)
its a primary atpase, comprised of 3 subunits alpha, beta gamma; it uses 1 ATP molecule, thereby importing 2 K+ ions and exporting 3 Na+ ions. This transports occurs against the electrochemical gradient, and is the main means of repolarisation after an AP.
an AP is generated in the cell when Na+ ions enter the cell through a voltage gated Na+ channel which cause the cell to depolarise. Na+ channels are fast, so the cell depolarises fast. in the meantime, K+ channels open and K+ ions flow out of the cell. The slow K+ channels allow the cell to hyperpolarise. after hyperpolarisation the Na+/K+ pump needs to bring the cell to its equilibrium state by replenishing the ion balance in and out of the cell.
a researcher increased the intra-extracellular concentration difference of K+ ions by 100. what would be the effect on membrane voltage?
according to Nerst equation:
E = -61.5mV * Z * log10(Cin/Cout)
E = -61.51log10(100) = -61.5 mV * 2 = -123 mV
-> the membrane potential will grow by 123.5 mV
When does synaptic depression occur?
Synaptic depression is a phenomenon that occurs in chemical synapses, where if 2 pulses that occur within a short time window, the second pulse will have a lower amplitude than the first one.
synaptic depression is the result of high release probability- the number of readily releasable vesicles is a limited pool. When the release probability is high, most of the vesicles in the RRP will be released in the first pulse (the larger one). and since the RRP takes time to be replenished, the second pulse will release less vesicles
when synaptic depression is driven by the post synaptic site, it is not related to the release probability, but rather, is the result if de-sensitisation of the post synaptic receptors.
The opposite phenomenon of synaptic depression is called synaptic facilitation, which occurs when the second pulses of 2 temporally adjacent pulses has larger amplitude
what is the SGLT transporter? and in which disease it is affected?
SGLT is a sodium-glucose-linked-transporter is a family of transport proteins in the intestine (SGLT1) and in the proximal tubule cells in the kidneys (SGLT2) which is responsible for transporting glucose from the intestines to the kidney.
in the small intestines, glucose ingested from food needs to be absorbed into the blood stream, and reabsorbed by the kidney, to prevent a leak of glucose into the urine.
SGLT is a symporter, meaning thy move 2 molecules in the same direction, through using the energy from the electrochemical gradient of one of the molecules.
SGLT are affected in diabetes, and medications that play SGLT activity helps diabetic patients by delaying glucose reabsorption in the kidney, thereby reducing blood-glucose levels
How to measure bloods osmolality?
Sodium is the main ion that determines the ECF osmolarity (as its concentration outside the cell is high).
The ECF is divided into 2 parts - plasma and interstitial fluid. Therefore, the blood osmolality can be calculated by multiplying the ECF Na+ concentration by 2
