Fundamentals of Physiology and Cell Ions

Question 1

What is homeostasis?

Answer 1

Homeostasis is the process by which biological systems maintain defined constant conditions in response to changes in the external or internal environment.

Question 2

How does homeostasis regulate variables?

Answer 2

Homeostasis uses negative feedback mechanisms, where a controller detects when a variable deviates from its normal range and initiates a response via an effector to bring the variable back to the normal range.

Question 3

What are baroreceptors and where are they located?

Answer 3

Baroreceptors are sensory receptors found in the walls of the carotid artery (in the neck) and the arch of the aorta (in the thorax). They detect changes in blood pressure.

Question 4

How does the body respond to high blood pressure?

Answer 4

In response to high blood pressure, there is reduced activity in the vasomotor center, leading to decreased heart rate and vasodilation (widening of blood vessels).

Question 5

How does the body respond to low blood pressure?

Answer 5

In response to low blood pressure, the baroreceptors become less active, resulting in increased activity of the vasomotor center. This leads to vasoconstriction (narrowing of blood vessels) and increased heart rate.

Question 6

What is positive feedback in the context of homeostasis?

Answer 6

Positive feedback is a mechanism in which the response to a stimulus amplifies or reinforces the original change, leading to an increase in the deviation from the normal range rather than restoring it.

Question 7

What is the effect of positive feedback on system stability?

Answer 7

Positive feedback can rapidly lead to system instability as it amplifies the initial change, pushing the system further away from its normal state.

Question 8

When are positive feedback control mechanisms appropriate?

Answer 8

Positive feedback control mechanisms are appropriate under certain circumstances, such as during specific physiological processes or events that require a rapid and decisive response.

Question 9

How does stretching of the cervix trigger positive feedback?

Answer 9

Stretching of the cervix during childbirth causes the release of oxytocin, a hormone involved in labor and delivery.

Question 10

What is the effect of oxytocin on the uterus?

Answer 10

Oxytocin stimulates the uterus to contract, which helps in pushing the baby through the birth canal.

Question 11

How does uterine contraction in response to oxytocin contribute to positive feedback?

Answer 11

Uterine contractions increase pressure and stretching on the cervix, which further stimulates the release of oxytocin. This creates a cycle of increasing contractions and stretching, amplifying the labor process.

Question 12

What is the role of Ca2+ in cellular function?

Answer 12

Ca2+ activates enzymes and proteins in the cell. It is normally present at low levels in the cytosol (100-200nM), but an increase in intracellular calcium can activate many enzymes and proteins. This can result in significant changes in the cell.

Question 13

what happens to water molecules in osmosis?

Answer 13

In osmosis, water molecules are displaced by ions such as Na+ and Cl-. They move from an area of lower solute concentration to an area of higher solute concentration.

Question 14

Where is the water concentration lower in osmosis?

Answer 14

The water concentration is lower on the right side of the barrier, where there is a higher solute concentration.

Question 15

: In which direction does the net diffusion of water occur in osmosis?

Answer 15

The net diffusion of water occurs from left to right, moving from the side of lower solute concentration to the side of higher solute concentration.

Question 16

What determines the osmotic pressure of a solution?

Answer 16

The concentration of solutes in the solution is the principal factor that determines the osmotic pressure. Higher solute concentration results in higher osmotic pressure.

Question 17

When does osmosis stop?

Answer 17

Osmosis will continue until the pressure difference between two sides (e.g., chamber A and B) is sufficient to halt the flow of water. This pressure difference is known as the osmotic pressure of the solution in chamber A.

Question 18

What are channel proteins in facilitated diffusion?

Answer 18

Channel proteins can be non-specific, allowing the passage of various atoms or molecules, or they can be specific, selectively allowing the passage of a particular atom or molecule.

Question 19

How do carrier proteins function in facilitated diffusion?

Answer 19

Carrier proteins change their conformation after binding to the target molecule, allowing the molecule to pass through the cell membrane.

Question 20

What happens when the concentration of the diffusing molecule is high in facilitated diffusion?

Answer 20

When the concentration of the diffusing molecule is high, the rate of facilitated diffusion reaches a maximum rate. This occurs when the carrier protein becomes saturated with its target molecule. Biochemically, this is known as the Vmax.

Question 21

How does cotransport via symporters work in active transport?

Answer 21

Channel proteins, known as symporters, can transport molecules in the same direction using the gradient of one component. This process requires energy.

Question 22

How does exchange via antiporters work in active transport?

Answer 22

Channel proteins, known as antiporters, can transport molecules in opposite directions using the gradient of one component. This process also requires energy.

Question 23

What is the primary active transport mechanism involving the Na+-K+ ATP pump?

Answer 23

The Na+-K+ ATP pump is an example of primary active transport. It utilizes ATP as an energy source to pump sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, against their concentration gradients.

Question 24

What is the role of parietal cells in the stomach?

Answer 24

Parietal cells release hydrochloric acid (HCl) into the stomach. The concentration of HCl is approximately 160mM. HCl helps in food digestion and protects the stomach from pathogens.

Question 25

How is carbon dioxide (CO2) transported into parietal cells?

Answer 25

CO2 enters the cell via passive transport. It can be generated through cellular metabolism or obtained from external sources.

Question 26

What happens when CO2 and water (H2O) react inside parietal cells?

Answer 26

CO2 and H2O react with the help of the enzyme carbonic anhydrase. This reaction forms carbonic acid (H2CO3), which dissociates into a proton (H+) and bicarbonate (HCO3-).

Question 27

How are the dissociated protons (H+) transported across the cell membrane?

Answer 27

The dissociated protons (H+) are transported across the membrane via the H+/K+ ATPase pump. This is an active transport mechanism that requires ATP.

Question 28

What happens to potassium ions (K+) in parietal cells?

Answer 28

K+ ions are recycled across the membrane, maintaining their concentration gradient.

Question 29

How is bicarbonate (HCO3-) transported to the plasma?

Answer 29

Bicarbonate (HCO3-) is transported to the plasma via a chloride (Cl-) antiporter. This exchange mechanism ensures the movement of HCO3- out of the cell.

Question 30

What happens to chloride ions (Cl-) in parietal cells?

Answer 30

Chloride ions (Cl-) are transported across the membrane into the lumen, where they combine with protons (H+) to form hydrochloric acid (HCl).

Question 31

How do omeprazole and oxonol dyes affect the transport processes in parietal cells?

Answer 31

Omeprazole is a proton pump inhibitor (PPI) that forms a disulfide bond with target residues in the H+/K+ ATPase, reducing its activity and inhibiting acid secretion. Oxonol dyes, on the other hand, inhibit the chloride bicarbonate antiporter and other transporters.

Question 32

What is voltage?

Answer 32

Voltage is the potential difference between two points in an electrical field. In biological systems, it is a consequence of membrane properties and ion concentrations.

Question 33

Are cell membranes normally permeable to charged ions?

Answer 33

No, cell membranes are not normally permeable to charged ions. They have selective ion channels and transporters that control the movement of ions across the membrane.

Question 34

Which ions are important in cellular function?

Answer 34

Potassium ions (K+) are the major cations inside the cell, while sodium ions (Na+) are the major cations outside the cell. Chloride ions (Cl-) are also important for cellular function.

Question 35

What is the relationship between voltage and potential?

Answer 35

Voltage is synonymous with electrical potential. It measures the amount of work required to move a charged species from one point to another.

Question 36

What happens when ions flow in a circuit?

Answer 36

When ions flow, a current is generated. Current is the flow of charged particles, such as ions, through a conductor.

Question 37

What are the rules of ionic balance?

Answer 37

he concentration of positive and negative ions must "nearly" balance. Any ion that leaves the cell must be replaced soon by another ion of that type coming into the cell. Energy is always being used to re-establish the ionic gradients across membranes.

Question 38

What is the difference between excitable and non-excitable cells?

Answer 38

Excitable cells have the ability to produce or respond to electrical signals. They can propagate action potentials. Examples of excitable cells include neurons, skeletal muscle cells, smooth muscle cells, and cardiac myocytes. Non-excitable cells do not have these abilities and include most other types of cells in the body.

Question 39

Which cells can propagate action potentials?

Answer 39

Excitable cells have the ability to propagate action potentials. These include neurons, skeletal muscle cells, smooth muscle cells, and cardiac myocytes.