Physio (2023) Flashcards

Question

Calcium channel antagonists block phase _ of cardiac action potential. A. 0 B. 1 C. 2 D. 4

Answer 1

C. 2 Rationale: Calcium channel antagonists primarily affect phase 2 of the cardiac action potential, which is characterized by the plateau phase due to Ca²⁺ influx.

Answer 2

D. Na⁺ influx Rationale: The amplitude of the cardiac action potential is primarily dependent on the rapid influx of Na⁺ ions during phase 0.

Answer 3

C. More negative resting membrane potential Rationale: A more negative resting membrane potential makes it harder for the cell to reach the threshold for depolarization, thus decreasing the heart rate.

Answer 4

D. All of these Rationale: Conduction velocity can change with alterations in the membrane potential at the end of repolarization, slow diastolic depolarization of phase 4, and threshold potential.

Answer 5

C. Slow response has less prolonged phase 2 Rationale: Slow response action potentials, typical of the sinoatrial and atrioventricular nodes, have a less prolonged phase 2 compared to fast response action potentials found in atrial and ventricular myocytes.

Answer 6

B. Isovolumic relaxation

Answer 7

A. Isovolumic contraction Rationale: The R wave on the electrocardiogram corresponds to the onset of ventricular depolarization, which initiates the isovolumic contraction phase of the cardiac cycle.

Answer 8

D. Myosin interacts with active site on actin Rationale: During excitation-contraction coupling, calcium binds to troponin C, causing a conformational change that moves tropomyosin away from the actin binding sites, allowing myosin to interact with these sites and generate contraction.

Answer 9

A. Decreased preload

Answer 10

C. Pulmonic Rationale: The pulmonic valve closure is best heard at the 2nd intercostal space along the left sternal border. APTM

Answer 11

B. Decreased venous return Rationale: Preload is primarily influenced by venous return to the heart. A decrease in venous return will decrease preload.

Answer 12

B. GFR is greater than the filtration rate of systemic capillaries Rationale: The GFR is significantly higher than the filtration rate of systemic capillaries due to the high permeability and large surface area of the glomerular capillaries.

Answer 13

A. These solutes are relatively small in size Rationale: Negatively charged solutes like Cl⁻ and HCO₃⁻ can cross the negatively charged filtration barrier primarily due to their small size, despite the repulsive charge.

Answer 14

A. 1.5 liters will be added to the ECF; 1.5 liters will be added to ICF Rationale: If excess water is reabsorbed due to increased ADH secretion, the water will distribute between the extracellular fluid (ECF) and intracellular fluid (ICF) compartments according to osmotic balance, typically in a roughly equal manner.

Answer 15

B. Decrease Rationale: An increase in membrane thickness reduces the rate of simple diffusion of a non-polar substance as it increases the distance that the substance must travel.

Answer 16

A. Na+ Rationale: Sodium (Na+) is commonly used in glucose symporters, where glucose is cotransported with Na+ across the cell membrane.

Answer 17

A. Concentration of water on each side of the membrane Rationale: Osmosis is driven by the concentration gradient of water across a membrane, moving from an area of higher water concentration to an area of lower water concentration.

Answer 18

B. Increase water permeability in the medullary collecting ducts Rationale: ADH increases water permeability primarily in the medullary collecting ducts, allowing for greater water reabsorption and concentration of urine.

Answer 19

C. Both afferent and efferent arterioles Rationale: Renal blood flow is regulated by altering the resistance in both afferent and efferent arterioles, which controls the pressure and flow within the glomerulus.

Answer 20

A. Ensures that GFR and RBF remain constant as blood pressure varies Rationale: Renal autoregulation maintains a relatively constant glomerular filtration rate (GFR) and renal blood flow (RBF) despite changes in systemic blood pressure, ensuring stable kidney function.

Answer 21

C. Simple diffusion Rationale: Urea is reabsorbed in the proximal tubules primarily through simple diffusion driven by the concentration gradient.

Answer 22

D. Thick ascending limb Rationale: The thick ascending limb of the loop of Henle is impermeable to water and actively transports ions out of the tubular fluid, making it the primary diluting segment in the countercurrent multiplication system.

Answer 23

C. Hypertonic Reasoning: Hypertonic means having a higher concentration of solutes compared to another solution. Gastric juice, particularly after a meal, typically has higher concentrations of hydrochloric acid (HCl), making it hypertonic compared to plasma. This includes higher concentrations of both Na and Cl ions.

Answer 24

A. Changing the driving force for K⁺ exit in the apical membrane Rationale: Increased tubular flow rate due to volume expansion can enhance the driving force for potassium exit in the apical membrane. As the flow rate increases, it washes away potassium in the tubular fluid, maintaining a gradient that promotes continued potassium secretion from the cells into the tubular lumen. This is a more direct mechanism affecting potassium secretion compared to the amount filtered by the glomerulus.

Answer 25

B. Potassium excretion increases Rationale: An increase in the flow rate of the tubular fluid typically leads to an increase in potassium excretion due to enhanced potassium secretion in the distal nephron.

Answer 26

A. The osmolarity of the interstitium is high Rationale: As isoosmotic tubular fluid enters the descending thin limb (DTL), it becomes more concentrated if the osmolarity of the surrounding interstitium is high, leading to water reabsorption and increased tubular fluid osmolarity.

Answer 27

D. Fats Rationale: The question likely pertains to a context where fats are involved, completing a specific physiological or biochemical concept.

Answer 28

C. I cells Rationale: Cholecystokinin (CCK) is released by I cells in the duodenum and jejunum in response to the presence of fats and proteins in the chyme.

Answer 29

C. Hypertonic Rationale: Gastric juice is typically hypertonic compared to plasma, especially during active secretion, due to the high concentration of hydrochloric acid (HCl) and other electrolytes present in the gastric secretions.

Answer 30

B. Substances that stimulate secretions Rationale: Secretogogues are substances that stimulate the secretion of various substances, such as digestive enzymes or hormones.

Answer 31

A. There is an ionic modification of a primary secretion Rationale: Secondary salivary secretion occurs when the initial isotonic fluid produced by acinar cells undergoes ionic modifications as it passes through the ductal system.

Answer 32

C. 1, 6 linkages of starch Rationale: Alpha amylase can cleave 1,4 glycosidic linkages in starch but cannot cleave 1,6 linkages, which are found at branch points in amylopectin.

Answer 33

B. GLUT 2 Rationale: GLUT 2 is the transport protein responsible for the efflux of glucose and galactose across the basolateral membrane of enterocytes into the bloodstream.

Answer 34

B. Alpha 1,4 bonds of maltose, maltotriose and limit dextrins Rationale: Glucoamylase breaks alpha 1,4 bonds in maltose, maltotriose, and limit dextrins, contributing to carbohydrate digestion.

Answer 35

C. Duct cell Rationale: The ionic composition of saliva is modified as it passes through the duct cells, which reabsorb sodium and chloride and secrete potassium and bicarbonate.

Answer 36

D. Pepsin Rationale: Exposure to hydrochloric acid and pepsin can cause tissue damage and peptic ulcer bleeding, as pepsin is a proteolytic enzyme that can degrade gastric mucosal tissues.

Answer 37

C. Glycerol ester hydrolase Rationale: Glycerol ester hydrolase, also known as pancreatic lipase, breaks down triglycerides into 2-monoglycerides and free fatty acids.

Answer 38

C. Triacylglycerols Rationale: Triacylglycerols (triglycerides) are the most abundant form of dietary lipids.

Answer 39

B. Caudad Rationale: The secondary swallow involves the movement of the bolus of food in the caudad (downward) direction through the esophagus towards the stomach.

Answer 40

A. Segmentation Rationale: Segmentation is the most common type of movement in the small intestines, involving rhythmic contractions that mix and slowly propel the contents.

Answer 41

C. Nitric oxide Rationale: Nitric oxide is a neurotransmitter that causes relaxation of gastrointestinal smooth muscle.

Answer 42

C. Bilateral movement and postural support Rationale: The medial corticospinal tract and other descending motor medial systems are involved in controlling bilateral movements and maintaining posture.

Answer 43

A. Cerebellum Rationale: The cerebellum compares the intended movements from higher centers with the actual movements in the periphery and makes necessary adjustments.

Answer 44

B. Loss of touch sensation on the ipsilateral side and pain sensation on the contralateral side Rationale: A spinal cord injury at T10 will result in loss of touch sensation (dorsal columns) on the ipsilateral side and pain sensation (spinothalamic tract) on the contralateral side.

Answer 45

C. Wernicke's area Rationale: Wernicke's area is responsible for the comprehension of spoken language, and damage to this area can result in difficulty understanding speech despite being able to speak.

Answer 46

B. Lens becomes spherical Rationale: During near vision, the ciliary muscles contract, causing the lens to become more spherical, which increases its refractive power to focus on close objects.

Answer 47

A. Stimulate the Leydig cells to synthesize and release testosterone Rationale: LH primarily stimulates the Leydig cells in the testes to produce and release testosterone, which is crucial for the development of male secondary sexual characteristics and spermatogenesis.

Answer 48

A. Inactivated or killed by acidic pH Rationale: Sperm are highly sensitive to pH levels and are inactivated or killed by an acidic environment, which is why the alkaline nature of seminal fluid is important for sperm viability.

Answer 49

A. LH Rationale: In the second half of the female menstrual cycle, LH stimulates the corpus luteum to secrete progesterone and some estrogen.

Answer 50

B. FSH Rationale: FSH stimulates the development of 10 to 20 primary follicles in the ovaries during the first 14 days of the menstrual cycle.

Answer 51

C. Fall in progesterone and estrogen Rationale: The drop in levels of progesterone and estrogen directly triggers the shedding of the endometrial lining, leading to menstruation.

Answer 52

C. Rigidity and bradykinesia Rationale: Lesions in the basal ganglia often manifest as rigidity and bradykinesia, which are characteristic symptoms of Parkinson's disease and other movement disorders.

Answer 53

A. Dorsal column medial lemniscal system Rationale: The dorsal column medial lemniscal system is responsible for transmitting sensations of fine touch, vibration, and proprioception to higher centers in the brain.

Answer 54

B. Lipogenesis - increased Rationale: A high insulin-glucagon ratio promotes lipogenesis (fat synthesis) and other anabolic processes while inhibiting catabolic processes like glycogenolysis and proteolysis.

Answer 55

C. Increase in plasma calcium and decrease in phosphate Rationale: Parathyroid hormone increases plasma calcium levels while decreasing phosphate levels by promoting calcium reabsorption in the kidneys and bone resorption.

Answer 56

B. Aldosterone Rationale: Increased extracellular potassium stimulates the adrenal cortex to synthesize and secrete aldosterone, which helps regulate potassium and sodium balance by increasing potassium excretion and sodium reabsorption in the kidneys.

Answer 57

D. Glucose Rationale: High levels of glucose are the most potent stimulus for insulin secretion from the beta cells of the pancreas.

Answer 58

C. Increased proteolysis and gluconeogenesis Rationale: Cortisol, produced by the zona fasciculata of the adrenal cortex, promotes increased proteolysis and gluconeogenesis, contributing to higher blood glucose levels.

Answer 59

D. Hyperosmolality of ECF Rationale: Hyperosmolality of the extracellular fluid (ECF) stimulates the release of antidiuretic hormone (ADH) from the posterior pituitary gland.

Answer 60

A. Cortisol Rationale: Cortisol secretion is regulated by the hypothalamic-pituitary-adrenal (HPA) axis.

Answer 61

B. Hypothalamus Rationale: Increased levels of TRH, TSH, and T3/T4 suggest a problem at the hypothalamus, causing excessive stimulation of the thyroid gland.

Answer 62

C. Involves gap junctions to transmit impulses from one cell to the next Rationale: Electrical synapses involve gap junctions, which allow direct transmission of electrical impulses between cells.

Answer 63

D. Acetylcholine Rationale: Acetylcholine is degraded by the enzyme acetylcholinesterase in the synaptic cleft.

Answer 64

C. Inhibitory postsynaptic potentials (IPSP) Rationale: Increased permeability of the postsynaptic membrane to chloride or potassium ions results in hyperpolarization, generating inhibitory postsynaptic potentials (IPSP).

Answer 65

D. Increases to -80mV Rationale: A hyperpolarized state occurs when the membrane potential becomes more negative than the resting membrane potential, such as increasing to -80mV from -70mV.

Answer 66

B. Na+ Rationale: Depolarization is characterized by a membrane that becomes very permeable to sodium ions (Na+), allowing them to enter the cell and reduce the membrane potential.

Answer 67

D. Potassium Rationale: The normal negative resting membrane potential of -70mV is primarily due to the efflux of potassium ions (K⁺) from the inside of the cell to the outside through potassium channels.

Answer 68

B. Repolarization Rationale: During repolarization, sodium channels close and potassium channels open, allowing K⁺ to exit the cell and restore the negative membrane potential.

Answer 69

A. Increase in the size of intracellular calcium Rationale: An increase in intracellular calcium concentration enhances the rate and force of cardiac muscle contraction.

Answer 70

A. Entry of extracellular Ca++ via voltage-gated L-type channels Rationale: In cardiac muscle, the entry of extracellular calcium through voltage-gated L-type calcium channels triggers the release of additional calcium from the sarcoplasmic reticulum, initiating contraction.

Answer 71

C. Activation of MLCK which phosphorylates the myosin heads Rationale: In smooth muscle, calcium binds to calmodulin, which activates myosin light chain kinase (MLCK). MLCK then phosphorylates the myosin heads, enabling them to bind to actin and generate contraction.

Answer 72

D. Sustained maintenance of contractile force at low ATP consumption Rationale: The "latch state" in smooth muscle refers to the ability to maintain contractile force for extended periods with minimal ATP consumption.

Answer 73

A. There will be no more overlap between actin and myosin filaments Rationale: Stretching the muscle beyond its optimal length reduces the overlap between actin and myosin filaments, decreasing the potential for cross-bridge formation and thus reducing contractile force.

Answer 74

D. Troponin Rationale: In skeletal muscle, calcium binds to troponin, causing a conformational change that moves tropomyosin away from actin binding sites, allowing actin-myosin interactions.

Answer 75

C. Sodium channels Rationale: The binding of acetylcholine to postsynaptic receptors in the sarcolemma opens sodium channels, leading to depolarization and muscle contraction.

Answer 76

B. Intracellular Ca++ decreases due to the activity of SERCA Rationale: Relaxation of skeletal muscle occurs when intracellular calcium levels decrease, primarily due to the activity of the sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA), which pumps calcium back into the sarcoplasmic reticulum.

Physio (2023) Flashcards

(100 cards)