If the surface area available for diffusion is reduced by half, but the concentration gradient is doubled, what is the net effect on the rate of diffusion?

it will remain unchanged

A toxin slows the opening of voltage-gated K+ channels. What would be the most likely effect on the action potential waveform?

The repolarization phase would be delayed.

A drug inhibits the binding of Na+ to the Na+/K+ -ATPase pump. What is the most likely effect on the intracellular enviornment?

Intracellular Na+ levels will increase.

A cell is placed in an isosmotic solution of 300 mM Urea, which is small and uncharged. How would you describe the tonicity of this solution?

Hypotonic

If the hypothalamic axons that innervate the posterior pituitary are severed, but the portal system remains intact, which hormone's release would be impaired?

Vasopressin (ADH)

If adenyl cyclase is inhibited, how would this impact the pathophysiology of cholera?

The concentration of Na+ in the intestinal lumen would be decreased.

If a membrane becomes equally permeable to both Na+ and K+, where would the membrane potential (Vm)) most likely settle?

At a value between ENa and Ek.

If a stimulus causes the relative permeability of Na+ (PNa) to become ten times greater than the permeability of K+ (PK), what is the most likely result?

Vm will move closer to the equilibrium potential of Na (ENa)

A patient presents with High CRH, High ACTH, and Low Cortisol. Which glad is dysfunctional?

Adrenal Cortex

In a low-glucose enviornment, which is the status of the KATP channels and the membrane potential in a pancreatic beta cell?

Channels are open; the membrane is hyperpolarized.

In response to chronically low levels of a hormone, a target cell upregulates the expression of associated receptors. This increased expression results in:

Increase sensitivity, requiring less hormone for a response.

In multiple Sclerosis, the loss of myelin affects conductance speeds primarily because:

subsequent nodes are impeded from reaching threshold.

If a patient is given exogenous insulin-like Growth Factor (IGF-1) injections, what would happen to their endogenous GH and GHRH levels?

Both GH and GHRH would decrease due to negative feedback.

If you decrease the extracellular concentration of Na+, how does the equilibrium potential for Na+ (ENa) change?

It becomes less positive.

A hormone effect is observed within seconds of binding to its target receptor. Which mechanism is most likely responsible?

Binding to a membrane receptor and opening an ion channel.

During the early phase of the relative refractory period, an action potential can fire if the stimulus is suprathreshold because:

Some K+ channels still open, requiring more Na+ entry to overcome K+ efflux.

A patient has High TSH, High T3/T4, and Low TRH. The pathology is located in the:

Anterior Pituitary

If a drug inhibits Ca2+ removal from the synaptic terminal, what would happen to neurotransmitter release?

Release would be prolonged or increased.

A small, amine-derived hormone is not bound to carrier proteins in the plasma. What can be predicted about its metabolic clearance compared to a steroid hormone?

It will have a shorter half-life because it is exposed to enzymatic degradation in the blood.

In the pancreatic beta cell, if you block Voltage-Gated Ca2+ channels, what happens when plasma glucose concentrations are high?

The cell depolarizes, but no insulin released.

A patient presents with Cushing's Disease, which is a disorder of the cortisol pathway characterized by hypersecretion of the anterior pituitary. What is the most likely result of the patient's blood panel?

Low CRH, High ACTH, High Cortisol

A patient with an iodine deficiency cannot produce T3/T4. Predict their TSH and TRH levels.

Both TSH and TRH will be high.

Which of the following allows a very small amount of hormone to create a massive cellular response?

Enzymatic cascades

A rare mutation eliminates synaptic ribbons from photoreceptors. What functional deficit is most likely present?

Decrease contrast sensitivity.

The somatosensory cortex contains a distorted map of the body, reflected as the sensory homunculus, in which the amount of cortical space dedicated to a body part is proportional to its sensitivity. To which of the following is this due?

The lower degree of convergence of primary sensory neurons in highly sensitive area, leading to smaller, more numerous receptive fields.

If a drug prevented the h-gate (inactivation gate) of voltage-gated Na+ channels from closing, how would this impact the action potential of a contractile myocardial cell?

The cell could remain in a prolonged depolarized state, preventing repolarization and subsequent contraction.

A patient suffers a lesion in the ride side of the medulla that severs the ascending fibers of the medial lemniscus. Which of the following deficits would be expected?

Loss of fine touch, proprioception, and vibration on the left side of the body.

A neurodegenerative disorder has disrupted the temporal retinal fibers exiting the optic nerve. Based on the neural pathways for vision, which visual deficit would be expected?

A loss of binocular vision.

According to Starling's Law of the Heart, an increase in venous return leads to a larger stroke volume because:

Stretching the myocardial fibers brings them closer to their optimum length for contraction.

A toxin alters the function of RyR in skeletal muscle such that they are in a permanently open state. What is the most likely physiological outcome?

Prolonged muscle contraction due to the continuous presence sacroplasmic Ca2+.

During the cross-bridge cycle in skeletal muscle, which step is directly responsible for the power stroke?

The release of Pi from the myosin head while it is bound to actin.

Which of the following describes the behavior of Funny Channels in cardiac pacemaker cells?

They are open during hyperpolarization and allow the slow influx of Na+.

A drug that inhibits Myosin Light Chain Kinase (MLCK) would have what effect on smooth muscle?

It would prevent myosin from binding to actin.

What anatomical feature of the visual system allows for depth perception?

The partial decussation of fibers at the optic chiasm, sending signals from the same visual field to the same cortex.

In a patient with chronic kidney disease and hyperkalemia, why does the QRS complex widen?

Elevating resting Vm keeps many Na+ channel inactivation gates (h-gate) closed, slowing depolarization.

How does Nitroglycerin help a patient experiencing an ST-segment elevation myocardial infarction (STEMI)?

It causes vasodilation and reduces venous return.

Why is the velocity of blood flow slowest in the capillaries, despite individual capillaries having the smallest diameter?

The total cross-sectional area of all capillaries combined is significantly larger than that of the aorta or vena cava.

A retinal drug acts as a strong phosphodiesterase (PDE) inhibitor. How would this affect the signaling cascade in a rod cell and the subsequent response of its OFF-bipolar cell when the retina is exposed to bright light?

The rod and OFF-biopolar cell will be depolarized.

Which of the following would increase total peripheral resistance (TRP)?

Vasoconstriction of small arteries and arterioles.

In the cardiac cycle, when does the "lub" (first heart sound) occur?

When the AV valves close at the beginning of isovolumetric ventricular contraction.

A patient has a condition where their Baroreceptors are less sensitive to stretch. How would their body respond to a sudden increase in blood pressure?

They would fail to adequately trigger the parasympathetic nervous system to slow the heart rate.

In smooth muscle, what is the role of calmodulin (CaM)?

It binds to Ca2+ and then activates Myosin Light Chain Kinase (MLCK).

The plateau phase of the contractile myocardial action potential is primarily maintained by:

Influx of Ca2+ through L-type channels balanced by K+ efflux.

A drug is applied to an isolated retina that selectively blocks the inhibitory output from amacrine and horizontal cells. How would this most likely affect the response of an on-center/off-surround ganglion cell when a photon is focused solely on the surround portion of its receptive field?

The ganglion cell would fail to show its characteristic suppression of firing.

Which of the following is true regarding autorhythmic cells of the heart?

They have Ca2+ channels that open around threshold, resulting in the depolarization phase of the action potential.

In the cardiac cycle, the "dub" (second heart sound) corresponds to the closure of the semilunar valves. At this moment, what is happening to ventricular pressure and volume.

Ventricular pressure has fallen below aortic pressure, causing the valve to close, and volume is at its minimum.

A patient is suffering from a condition that inhibits the activity of Carbonic Anhydrase within red blood cells and renal tubule cells. Which of the following would be the most likely physiological response?

A decrease in plasma CO2 carried in the form of bicarbonate.

During the intestinal phase of digestion, the presence of acidic chyme in the duodenum triggers the release of Secretin to:

stimulate the pancreas to secrete bicarbonate to neutralize the acid before it can affect systemic pH.

A patient presents with respiratory alkalosis due to acute hyperventilation. How will the renal system compensate for this high blood pH?

Type B intercalated cells will secrete HCO3- into the filtrate and reabsorb H+ into the blood.

Due to a mean arterial pressure (MAP) of 70mmHg, the macula densa senses an altered rate of NaCl delivery to the distal tubule. Which of the following is the correct extrinsic compensatory response?

The granular cells will secrete Renin.

A patient is administered a medication that increases their gastric pH to 5.5. How will this impact the digestion of a protein-rich meal?

It will prevent the conversion of pepsinogen to pepsin, impairing protein digestion.

A patient with heart failure exhibits elevated circulating levels of Atrial Natriuretic Peptide (ANP). Which of the following describes the effects of ANP on the renal system and RAAS pathway?

ANP increases GFR by dilating the afferent arteriole and inhibits the release of Renin from granular cells.

A patient with untreated Type 1 Diabetes experiences diabetic ketoacidosis, lowering their plasma pH to 7.1. Which of the following is correct compensatory response?

Hyperventilation driven by peripheral chemoreceptors; the Bohr effect shifts the dissociation curve to the right to enhance O2 unloading.

A class of diabetes drugs, SGLT inhibitors, work by blocking the Na+-glucose cotransporter in the proximal tubule. Which of the following is the most likely physiological response?

An increase in glucose excretion.

A patient is administered a diuretic that inhibits the NKCC transporters in the thick ascending limb. After three hours, what would be the most likely change in the medullary osmotic gradient?

The gradient would be decreased, resulting in an inability to concentrate urine.

At the peripheral tissues, hemoglobin unloads O2. The resulting deoxyhemoglobin has a higher affinity for H+ than oxyhemoglobin. How does this property facilitate CO2 transport?

Hb acts as a buffer, binding the H+ generated from the carbonic anhydrase reaction, thus pulling the CO2 + H2O --> HCO3- + H+ reaction to the right.

Chronic diarrhea leads to a significant loss of bicarbonate from the lower GI tract. Which of the following is the correct compensatory response from the respiratory and renal systems?

Lungs: Hyperventilation to lower Pco2; kidneys: Type A cells secrete H+.

A patient's mean arterial pressure (MAP) increases to 135mmHg. The feedback mechanism will:

Constrict the afferent arteriole to maintain a constant GFR.

A patient has a genetic defect preventing the synthesis of apolipoprotein B, which is essential for chylomicron assembly. What is the most likely result after a meal rich in triglycerides?

Triglycerides accumulate within the enterocyte.

A patient is experiencing respiratory acidosis and the respiratory system failing. How will the renal system attempt to compensate for this?

The kidneys will excrete more H+ and reabsorb more HCO3- to buffer the Pco2-driven acidosis.

During intense exercise, lactic acid builds up in the blood. What is the direct effect of this acid on the oxygen-carrying capacity of hemoglobin?

Hb affinity for O2 decreases, facilitating O2 delivery to the muscle (right shift).

Acute pancreatitis can be caused by the premature activation of pancreatic zymogens within the pancreas, leading to auto-digestion. The destructive cascade is initiated by the activation of one key zymogen, which then activates all the others. Which zymogen's premature activation is the most likely initiator of this cascade?

Trypsinogen.

What is the functional advantage of the renal portal system?

It allows for high-pressure filtration followed by low-pressure reabsorption.

A patient overdosed on benzodiazepines, resulting in acute hypoventilation. What is the expected stimulus for the resulting respiratory compensation?

Central chemoreceptors sensing an elevated H+ in the CSF derived from high Pco2.

A patient with hypertension is treated with an ACE inhibitor. Another patient is treated with a direct renin inhibitor (DRI). Which statement best predicts the difference in their circulating hormonal profiles?

The ACE inhibitor patient will have high Renin and high ANG I, but low ANG II. The DRI patient will have low levels of Renin, ANG I, and ANG II.

An individual is in a state of severe dehydration, which is characterized by decreased blood volume and pressure, as well as increased blood osmolarity. What role does increased plasma osmolarity play in the overall feedback response of the renin-angiotensin system?

It serves as an inhibitory signal that prevents excessive aldosterone release from the adrenal cortex.

The cephalic phase of digestion is mediated by:

Vagal stimulation of parietal cells.

A tumor of the granular cells causes chronic secretion of large quantities of renin. Clinical findings would include:

Hypertension and hypokalemia.

Incretin hormones (GIP/GLP-1) are released from the small intestine in response to:

The presence of carbohydrates in the intestinal lumen.