Homeostasis
What is homeostasis, and why is it important in maintaining physiological balance?
Homeostasis is a state where the internal and external environments of the cell are balanced. It is crucial for maintaining stable physiological conditions essential for survival.
How does the sodium-potassium pump contribute to cell function?
It actively transports 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell, maintaining the electrical gradient critical for nerve and muscle function.
Define osmotic pressure and its role in fluid movement within the body.
Osmotic pressure is the chemical pressure exerted by solutes in the bloodstream, pulling water into the extracellular space to maintain fluid balance.
What triggers the release of renin, and what is its primary function?
Renin is released in response to low blood pressure or poor perfusion and converts angiotensinogen to angiotensin I.
What is the primary function of the plasma membrane in a cell?
The plasma membrane forms the boundary between the inside and the outside of the cell, regulating the entry and exit of substances.
What is upregulation in cellular receptors, and under what condition might it occur?
Upregulation is an increase in the number of receptors in response to low levels of a stimulus, such as increased TSH receptors in hypothyroidism.
What is the difference between facilitated diffusion and active transport?
Facilitated diffusion is a passive process where molecules move down their concentration gradient with the help of a protein, without energy input. Active transport requires energy (ATP) to move molecules against their concentration gradient.
What is the difference between dependent edema and anasarca?
Dependent edema is localized swelling due to gravity, while anasarca is generalized swelling across the body due to osmotic imbalances.
A patient presents with confusion and muscle cramps. Lab results reveal a sodium level of 122 mEq/L. Explain the underlying physiological imbalance and identify an appropriate treatment strategy.
The patient has severe hyponatremia, likely causing intracellular swelling due to fluid shifts. Treatment involves cautiously increasing serum sodium with hypertonic saline to avoid osmotic demyelination syndrome.
A mutation in a gene coding for phospholipids causes impaired plasma membrane function. Predict how this defect might affect cellular homeostasis.
Impaired plasma membrane function could disrupt selective permeability, leading to ionic imbalances, altered osmotic pressure, and potential cell swelling or dehydration.
A patient with severe burns develops edema in the lower extremities. Using Starling’s Law, explain the pathophysiology behind this finding.
Burn injuries increase capillary permeability, leading to protein leakage into the interstitial space. This reduces oncotic pressure in capillaries and increases hydrostatic pressure, causing fluid accumulation (edema).
During labor, a patient experiences uterine contractions that intensify progressively. How does the positive feedback loop involving oxytocin contribute to this process?
Oxytocin released from the posterior pituitary stimulates uterine contractions. These contractions increase cervical pressure, which signals more oxytocin release, continuing until delivery.
A patient with uncontrolled diabetes presents with a blood glucose level of 600 mg/dL and symptoms of dehydration. Explain how this condition disrupts homeostasis and contributes to dehydration.
The high blood glucose level creates an osmotic gradient, pulling water from intracellular and interstitial compartments into the bloodstream. This leads to increased urination (osmotic diuresis), which depletes body water and causes dehydration.
A genetic defect reduces sodium-potassium pump activity. Analyze how this defect would affect nerve impulse transmission.
Reduced pump activity disrupts the resting membrane potential, making neurons less responsive to stimuli and impairing action potential propagation.
A patient receives 3% saline IV for severe hyponatremia. What risks should be monitored during treatment, and why?
Rapid correction can cause osmotic demyelination syndrome as brain cells cannot restore lost solutes quickly. Monitor for neurological symptoms like weakness, dysarthria, or seizures.
A patient with chronic kidney disease has a potassium level of 6.2 mEq/L. EKG shows tall, peaked T-waves. What immediate intervention is needed, and why?
Administer calcium gluconate to stabilize the cardiac membrane, followed by insulin and glucose to shift potassium intracellularly and prevent cardiac arrhythmias.
A 45-year-old male presents with confusion, fatigue, and a serum sodium of 118 mEq/L. What is the best next step in management?
A patient with cystic fibrosis has a defective chloride channel. What cellular process is most directly affected?
A patient with cirrhosis presents with ascites. Which mechanism best explains this fluid accumulation?
A 70-year-old man with heart failure is given an ACE inhibitor. Which physiological effect is directly mediated by this drug?