Cell Physiology of Ions 2 Flashcards
Hypo
Too little
Hyper
Too much
Hypocalcaemia
Too little calcium in plasma. Causes too much activity; arrhythmias, over-reactive reflexes, seizures
Hypercalcaemia
Too much calcium n plasma. Leads to too little activity; constipation, psychological depression
Paraesthesia
An abnormal sensation of pins and needles or numbness
Tetany
Intermittent muscular spasms
Chvostek’s sign
One sign of tetany seen in hypocalcaemia. Abnormal reaction to stimulation of facial nerve; when facial nerve is tapped at angle of jaw, facial muscles on that side of the face will contract momentarily, typically twitch of nose or lips
Cytosol
The aqueous component of cytoplasm of cell
What is the second messenger for fertilisation of egg cell
High free Ca2+ content in cell is second messenger.
Excitable cells, with examples
Cells that can propagate an action potential/ cells that can produce or respond to electrical signals. Neurons and myocytes and fertilisable egg cells
Non-excitable cells, with examples and counterexamples
Cells without action potentials. Not muscle or nerve. Epithelial cells
Relationship in terms of movement between Na+, Cl- and H2O
Na+ gets pumped or moves through ion channels, Cl- tends to follow Na+ (and other permeable cations) and water follows Cl-
Which is higher in total cations, intracellular or extracellular fluid? Why are these cations needed in that compartment?
Intracellular. To balance out all the anionic proteins.
Which fluid compartment has the highest Cl- concentration but the lowest electrolyte concentration?
Interstitial fluid
Which fluid compartment has the highest electrolyte concentration?
Intracellular
Why is intracellular fluid highly negative?
Because some negative ions (Cl-) are not paired with positive ions (K+) because K+ leaks out without any anions following
What conditions must Calcium be in to partake in reactions?
Free, ionised, in solution in cytosol
Another name for free intracellular calcium
Cytosolic calcium
Action potential triggers muscle contraction via……?
A cytosolic calcium increase
If action potential in muscle cells is too weak, ……….?
Not enough Ca2+ is released so no muscle contraction
Action potential is a change in voltage. It can lead to other changes inside the cell:
Second messengers; calcium, kinases, phospholipases. Muscle contraction. Change in voltage in one cell can lead to change in voltage in other cells; synaptic transmission
Explain in terms of action potentials and ions how involuntary muscle contractions occur.
In pathological situations, AP not needed for Calcium ion release so unwanted contractions.
Give the 3 rules of ionic balance. What is the importance of the rules of ionic balance?
Charge must balance, ions must be replaced, energy maintains ionic gradients. Ion transport depends on these rules
Explain ‘charge must balance’ law
Concentration of positive and negative ions must nearly balance. If +ve ion crosses membrane, charge imbalance corrected by either -ve ion following or another _ve charge going in opposite direction. “Nearly” means that there can be tiny amounts of unbalanced cations on one side of a membrane that are near to anions on the other side of the membrane
Explain ‘ions must be replaced’ law. Give an example and explain the importance of the law in the example
Any ion that leaves the cell must be replaced soon by another ion of that same type coming into cell. When cells in salivary gland secret K+ into saliva, K+ ions replaced by K+ from blood. This is fundamental to homeostasis; otherwise the salivary cells would run out of K+.
Explain ‘energy maintains gradients’ rule. Give an example
Energy is always being used to re-establish the ionic gradients across membranes. e.g. Na-K pump
Changes in blood pH mainly corrected by……?
Kidneys and lungs
pH is a measure of the concentration of…….?
Free H+ ions
Carbonic anhydrase is used for homeostasis in many systems. Give 4 examples.
Red Blood Cells: Chloride shift for removing H+/ CO2 from muscle. Lungs: removing CO2 from blood. Gastric Parietal Cells: Secreting acid into stomach. Pancreas: secreting bicarbonate.
Describe Chloride shift in RBC for muscles.
Need to remove CO2 and H+ from respiring tissue. CO2 produced by respiring cell diffuses into RBC where CA reacts it to make H+ and HCO3-. H+ binds to RBC which acts as a buffer and HCO3- in RBC enters blood plasma in exchange for a Cl-. OPPOSITE AT LUNGS
Why is Cl- content of RBC in veins higher than that of arterial RBC?
Because venous RBC uses cloride shift to remove H+ and CO2 from cells.
What is the purpose of gastric pits and what key cells are found in them?
Increases surface area of stomach lumen. Full of gastric parietal cells.
What inhibits chloride shift?
Acetazolamide
Another name for parietal cell?
Oxyntic cell
What inhibits proton pumps?
Omeprazole
How are bicarbonate ions removed from gastric parietal cells?
Chloride-bicarbonate exchanger (passive)
How are protons removed from gastric parietal cells?
Proton pumps (active)
What inhibits chloride-bicarbonate exchangers?
Oxonol dyes
What ion is brought in simultaneously by the proton pump (in parietal cell)?
K+
How do K+ ions leave parietal cell?
Passive potassium channels
How does Cl- brought into gastric parietal cell by chloride-bicarbonate exchanger leave the cell?
Chloride channels, passive.
What does Cl- make once it has left the gastric parietal cell?
Combines with H+ from proton pump to make HCl in lumen of stomach
Where on the gastric parietal cell is the chloride-bicarbonate exchanger?
Basal side.
Where on the gastric parietal cell is the potassium channel found?
Basal and apical
Where on the gastric parietal cell is the chloride channel found?
Apical side
Where on the gastric parietal cell is the proton pump found?
Apical side
How does the gastric parietal cell ensure that it is not depleted in terms of K+ concentration?
Sodium-potassium pump, which pumps 3 Na+ out and 2K+ in, actively
Where on the gastric parietal cell is the sodium-potassium pump found?
Basal side
What inhibits the sodium-potassium pump?
Ouabain and digitalis
