Physio: Cardiac/ Smooth Muscle And Stages Of Death Flashcards
(25 cards)
A 65-year-old male presents with severe heart failure. His physician decides to prescribe Digoxin to improve cardiac function. Based on its likely mechanism described in the sources, how would a cardiac glycoside like Digoxin affect cardiac muscle contraction?
A) By decreasing the duration of the cardiac action potential.
B) By reducing the influx of Ca2+ from the extracellular fluid.
C) By increasing the Ca2+ transient within the cardiac muscle cell.
D) By speeding up the rate of cross-bridge recycling.
C) By increasing the Ca2+ transient within the cardiac muscle cell.
Cardiac cycle contraction is increases by increase Ca2+ in the cell. Ca2+ regulates cardiac contractions.
A patient undergoing surgery requires medication to lower their blood pressure. A calcium channel blocker is administered. According to the sources, how do calcium channel blockers reduce blood pressure?
A) By increasing the activity of the sodium-calcium exchanger in cardiac myocytes.
B) By preventing the entry of Ca2+ into cardiac myocytes, thus reducing contractility.
C) By promoting temporal summation in cardiac muscle.
D) By facilitating relaxation through enhanced ATPase pump activity.
B) By preventing the entry of Ca2+ into cardiac myocytes, thus reducing contractility.
A medical student is observing a histology slide of cardiac muscle tissue. Which of the following features would they expect to see that distinguishes it from skeletal muscle according to the sources?
A) Lack of striations and a central nucleus.
B) Presence of functional syncytia connecting cells.
C) Thin filaments that lack troponin but contain caldesmon.
D) Sarcomeres anchored to dense bodies.
B) Presence of functional syncytia connecting cells
The remaining are characteristics of smooth muscle cells.
A pharmacologist is developing a new drug that inhibits the sodium-calcium exchanger in cardiac muscle cells. Based on the sources, how would inhibiting this exchanger likely affect intracellular calcium levels and potentially cardiac function?
A) It would increase Ca2+ removal, leading to decreased contractility.
B) It would facilitate relaxation by speeding up Ca2+ efflux.
C) It would lead to increased intracellular Ca2+ levels, potentially increasing contractility.
D) It would primarily affect smooth muscle contraction, not cardiac muscle.
C) It would lead to increased intracellular Ca2+ levels, potentially increasing contractility.
If the exchanger was damaged, it will cause an influx of Ca2+
A 70-year-old patient collapses and is later pronounced dead. During the postmortem examination conducted within the first hour, the medical examiner notes a general paleness of the skin in the areas not compressed by the surface the body was lying on. What stage of death does this finding most likely represent?
A) Livor mortis.
B) Rigor mortis.
C) Pallor mortis.
D) Algor mortis
C) Pallor mortis.
Pallor mortis is the 1st stage of death characterized by paleness of the skin often to seen in light/ white people
Several hours after death, a body is found. The medical examiner attempts to move the limbs and finds them to be stiff and rigid. Which stage of death is characterized by this postmortem rigidity due to chemical changes in the muscles?
A) Algor mortis.
B) Livor mortis.
C) Pallor mortis.
D) Rigor mortis
D) Rigor mortis
Rigor mortis is the 3rd stage of death and the recognizable stage where limbs of the body become stiff due to chemical changes in the body postmortem.
A forensic pathologist is examining a body found approximately 10 hours after death. They observe a significant purplish-red discoloration on the dependent parts of the body. According to the sources, when does this postmortem lividity (livor mortis) typically peak?
A) Within 20 minutes of death.
B) By two hours after death.
C) 8-12 hours after death.
D) 24-48 hours after death
C) 8-12 hours after death.
A patient presents with a condition affecting their smooth muscle function. Histological examination of a smooth muscle sample reveals an absence of a key structural component found in skeletal muscle. What structural component is specifically noted as absent from smooth muscle cells in the sources?
A) Thick filaments.
B) Thin filaments.
C) Dense bodies.
D) Sarcomeres
D) Sarcomeres
Sarcomeres are not found in smooth muscle cells.
A researcher is investigating the mechanism of smooth muscle contraction. They discover a protein that binds to tropomyosin and actin at low calcium concentrations, preventing myosin interaction. According to the sources, what protein likely has this role and is believed to be involved in latch bridges?
A) Troponin.
B) Calmodulin.
C) Myosin light chain kinase (MLCK).
D) Caldesmon
B) Calmodulin.
At low calcium levels, this results in muscle relaxation
A medical student is learning about the unique features of smooth muscle contraction. They are told that actin and myosin do not spontaneously interact in smooth muscle. What molecule is responsible for preventing this spontaneous interaction in smooth muscle at rest?
A) Caldesmon.
B) Tropomyosin.
C) Regulatory light chains on myosin.
D) Calponin
C) Regulatory light chains on myosin.
In order for actin to interact with myosin, myosin must be phosphorylated.
A patient has developed a condition causing their cardiac muscle to undergo sustained contractions without adequate relaxation periods. Based on the sources, this abnormal state, similar to skeletal muscle tetany, is normally prevented in cardiac muscle by what physiological mechanism?
A) The functional syncytial arrangement of cardiac cells.
B) The prolonged duration of the cardiac action potential compared to the contraction-relaxation cycle.
C) The reliance on extracellular calcium influx for contraction.
D) The rapid removal of calcium from the sarcoplasm by ATPase pumps
B) The prolonged duration of the cardiac action potential compared to the contraction-relaxation cycle.
To avoid tetany, the amount of time between the action potential and free Ca2+ in the SR remain the same. Therefore this prevents the firing of an action potential before the end of the contraction relaxation cycle.
A forensic technician is attempting to estimate the time of death using the Glaister equation. They measure the rectal temperature of the body. What additional information is explicitly mentioned in the sources as potentially affecting the accuracy of the Glaister equation calculation?
A) Blood type of the deceased.
B) Presence of clothing on the body.
C) Last meal consumed by the deceased
D) Time of day death
B) Presence of clothing on the body.
Ambient temperature, clothing, disease process and surface area other factors.
A patient is diagnosed with a condition affecting smooth muscle contraction in their gastrointestinal tract, leading to impaired peristalsis (propulsion). According to the sources, which typical arrangement of smooth muscle layers in the GIT contributes to this propulsive function?
A) Circumferentially arranged layers.
B) Varied arrangement.
C) Longitudinally arranged layers.
D) Multiunit arrangement
C) Longitudinally arranged layers.
A researcher is comparing excitation-contraction coupling in skeletal and cardiac muscle. According to the sources, what is a unique difference in the source of calcium that triggers contraction initiation in cardiac muscle compared to skeletal muscle?
A) Calcium release from the SR is the sole trigger in cardiac muscle.
B) Depolarization directly triggers calcium release from the SR in cardiac muscle.
C) Calcium influx during the action potential plateau triggers calcium release from the SR in cardiac muscle.
D) T-tubules are absent in cardiac muscle, altering calcium source
C) Calcium influx during the action potential plateau triggers calcium release from the SR in cardiac muscle.
A student is reviewing the different types of smooth muscle. They learn about single-unit smooth muscle where only a few fibers are innervated, and the impulse spreads between cells. What specialized structures are mentioned in the sources as facilitating the spread of impulse between cells in single-unit smooth muscle?
A) Dense bodies.
B) Sarcomeres.
C) Neuromuscular junctions.
D) Gap junctions
D) Gap junctions
In smooth muscle, the sources state that actin and myosin can bind only after a specific event occurs involving myosin. What specific modification of the myosin head is required for it to interact with actin in smooth muscle?
A) Binding of troponin.
B) Phosphorylation of regulatory light chains.
C) Binding of caldesmon.
D) Dephosphorylation by myosin phosphatase
B) Phosphorylation of regulatory light chains.
Ca binds to Caldesmon. The activates Caldesmon brings to myosin light chain kinase and releases phosphate from ATP and bind to myosin head to interact with actin.
The ‘latch mechanism’ in smooth muscle allows for sustained contractions with minimal energy use. According to the sources, what is the key feature of cross-bridges during the latch mechanism that makes tension maintenance economical?
A) Cross-bridges cycle rapidly, but use less ATP per cycle.
B) Cross-bridges release completely between cycles, conserving ATP.
C) Cross-bridges are maintained without continuous cycling and ATP hydrolysis.
D) Cross-bridges utilize ATP more efficiently than in skeletal muscle
C) Cross-bridges are maintained without continuous cycling and ATP hydrolysis.
A pathologist is explaining the functional anatomy of cardiac muscle to a group of students. They highlight the presence of specialized structures at the cell junctions that allow the tissue to act as a functional syncytium. What are these specialized gap junctions called in cardiac muscle?
A) Neuromuscular junctions.
B) Dense bodies.
C) Intercalated discs.
D) Sarcoplasmic reticulum
C) Intercalated discs.
A patient is experiencing symptoms related to the smooth muscle in their blood vessels, leading to altered vessel diameter. According to the sources, what arrangement of smooth muscle is typically found in blood vessels to allow for reduction in diameter upon contraction?
A) Longitudinally arranged.
B) Circumferentially arranged.
C) Varied arrangement.
D) Multiunit arrangement
B) Circumferentially arranged.
A physiologist is comparing the efficiency of contraction between smooth muscle and skeletal muscle. The sources state that smooth muscle has a slower rate of cross-bridge recycling. How much slower is the ATPase activity in smooth muscle compared to skeletal muscle, according to the provided information?
A) About half as fast.
B) About the same speed.
C) 1/10 to 1/300 times slower.
D) 5 times faster.
C) 1/10 to 1/300 times slower.
A student is studying the relaxation process in smooth muscle. They learn that when intracellular Ca2+ concentration falls, another enzyme is activated to dephosphorylate the cross-bridges, leading to relaxation. What enzyme performs this dephosphorylation step?
A) Myosin light chain kinase (MLCK).
B) Calmodulin.
C) Caldesmon.
D) Myosin phosphatase
D) Myosin phosphatase
In cardiac muscle, the T-tubules play a role in excitation-contraction coupling. According to the sources, how do cardiac muscle T-tubules compare in diameter to those of skeletal muscle, and what functional consequence does this difference have?
A) They are smaller, facilitating slower calcium influx.
B) They are larger (five times the diameter), facilitating more direct calcium influx from the ECF.
C) They are located along the A-lines, preventing calcium-induced calcium release.
D) They are absent, meaning calcium influx relies solely on SR stores
B) They are larger (five times the diameter), facilitating more direct calcium influx from the ECF.
A patient requires precise, fine control over a small muscle group. Which type of smooth muscle, where cells or groups of cells act as independent units and are found in structures like the arrector pili of the skin and the iris of the eye, is best suited for this function?
A) Single-unit smooth muscle.
B) Circumferential smooth muscle.
C) Longitudinal smooth muscle.
D) Multiunit smooth muscle
D) Multiunit smooth muscle
A cardiologist is adjusting the medication regimen for a patient with heart failure to improve the strength of cardiac contractions. He explains that certain medications can enhance contractility by increasing the amount of calcium available within the cardiac muscle cell during contraction. Which of the following is a primary mechanism by which the strength of cardiac muscle contraction is regulated?
a) Increasing the activity of myosin phosphatase.
b) Reducing the duration of the action potential plateau phase.
c) Relying solely on calcium release from the sarcoplasmic reticulum.
d) Regulating the amplitude of the Ca2+ transient within the cell.
d) Regulating the amplitude of the Ca2+ transient within the cell.
