Block 2 Pace1 - 2011 Sem.1 Pace Quiz 3
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Dr. Yin Thick filaments are anchored to the Z disks by which of the following accessory proteins in the sarcomeres?
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Nebulin
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C protein
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Titin
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ą-actinin
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Myomesin
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.JPG "Block 2 Pace1 - 2011 Sem.1 Pace Quiz 3 - Quiz")
This quiz titled 'block 2 Pace1 - 2011 Sem. 1 PAcE quiz 3' assesses knowledge on human anatomy and physiology, focusing on reflexes, muscle function, and surgical implications. It is designed for medical students preparing for exams, enhancing understanding of practical and theoretical aspects of the musculoskeletal system.
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- 2.
Which of the following statements characterizes the cardiac muscle cells?
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Each muscle fiber is syncytium
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Neurons in the cardiac conducting system are multipolar.
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They possess dense bodies.
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They have sarcomere and myofibrils.
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They require an external stimulus to undergo contraction.
Correct Answer
A. They have sarcomere and myofibrils.Explanation
Cardiac muscle cells are characterized by the presence of sarcomeres and myofibrils. Sarcomeres are the basic contractile units of muscle cells, composed of overlapping actin and myosin filaments. Myofibrils are the bundles of sarcomeres within a muscle cell, responsible for muscle contraction. This characteristic distinguishes cardiac muscle cells from other types of muscle cells, such as smooth muscle cells, which do not have well-defined sarcomeres and myofibrils.Rate this question:
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- 3.
The level of which of these in the blood is used clinically as a measure of the amount of bone formation that is occurring?
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Acid phosphatase
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Calcium
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Vitamin D
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Alkaline phosphatase
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Somatotrophin
Correct Answer
A. Alkaline phosphataseExplanation
Alkaline phosphatase is used clinically as a measure of the amount of bone formation that is occurring. This enzyme is primarily found in the liver, bones, and kidneys, and its levels in the blood can indicate the rate at which new bone is being formed. When bone formation is increased, such as during growth or healing of fractures, alkaline phosphatase levels tend to rise. Conversely, low levels of alkaline phosphatase may indicate decreased bone formation or certain medical conditions affecting the bones. Therefore, monitoring alkaline phosphatase levels can provide valuable information about bone health and the effectiveness of treatments aimed at promoting bone formation.Rate this question:
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- 4.
Dr. Sharma A 54 year old man who has an established diagnosis of myasthenia gravis, is seen in the emergency room for complaints of weakness and difficulty breathing. He has not been regular with his medication. On examination you note that his skin is dry but not warm and that he has bilateral ptosis. He is also cyanosed. Given this clinical presentation you would consider that he is suffering from:
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Cholinergic crisis
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Medication overdose
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A Myasthenic crisis
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Acute respiratory infection
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Acute meningitis
Correct Answer
A. A Myasthenic crisisExplanation
Based on the clinical presentation of weakness, difficulty breathing, bilateral ptosis, and cyanosis in a patient with a known diagnosis of myasthenia gravis who has been noncompliant with medication, it is likely that the patient is experiencing a myasthenic crisis. A myasthenic crisis is a worsening of symptoms in patients with myasthenia gravis, often triggered by medication noncompliance or infection. It is characterized by severe muscle weakness, including respiratory muscles, leading to respiratory distress.Rate this question:
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- 5.
Dr. Moore What is the name of the structure shown in the accompanying drawing?
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Howship's lacuna
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Osteon
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Canaliculus
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Haversion canal
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Volkmann canal
Correct Answer
A. OsteonExplanation
The correct answer is Osteon. Osteon is a structural unit of compact bone, consisting of concentric layers of bone matrix called lamellae surrounding a central canal called the Haversian canal. The Haversian canal contains blood vessels and nerves. The drawing likely shows the arrangement of lamellae and the Haversian canal, which is characteristic of an osteon.Rate this question:
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- 6.
Which of the following structures can be found in smooth muscle?
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Triads
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Myofilaments
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Sarcomeres
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Intercalated discs
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Troponin
Correct Answer
A. MyofilamentsExplanation
Smooth muscle is a type of muscle tissue that is found in various organs and structures in the body. It is characterized by its lack of striations or visible bands, unlike skeletal and cardiac muscle. Myofilaments are the contractile proteins found in muscle cells, and they are responsible for the contraction and relaxation of the muscle. Therefore, myofilaments can be found in smooth muscle, making them the correct answer. Triads, sarcomeres, intercalated discs, and troponin are structures that are typically found in skeletal or cardiac muscle, not smooth muscle.Rate this question:
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- 7.
A baby is born with only rudimentary upper limbs. Discussion revealed that the mother ingested an anti-nausea drug during the first trimester of her pregnancy. What is the likely cause of this condition in the child?
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Abnormal migration of neural crest cells
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Abnormal migration of muscles into limb bud
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Apoptosis of developed bone and muscle cells
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Lack of vascular supply to limb bud
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Maldevelopment of the apical ectodermal ridge
Correct Answer
A. Maldevelopment of the apical ectodermal ridgeExplanation
The maldevelopment of the apical ectodermal ridge is the likely cause of the condition in the child. The apical ectodermal ridge is a specialized structure that plays a crucial role in limb development. It is responsible for signaling and organizing the growth of the limb bud, which eventually forms the upper limbs. If the apical ectodermal ridge is not properly developed, it can lead to abnormalities in limb formation, such as rudimentary upper limbs. The ingestion of the anti-nausea drug by the mother during the first trimester may have disrupted the development of the apical ectodermal ridge, resulting in this condition in the child.Rate this question:
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- 8.
Dr. Martin Congenital torticollis was diagnosed in an infant whose head was titled to the left with the chin turned up and to the right. Which is the most likely cause of this condition?
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Contraction of right splenius muscle
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Contraction of rectus capitis majors
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Contraction of right trapezius
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Contraction of the left sternocleidomastoid muscle
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Contraction of right sternocleidomastoid muscle
Correct Answer
A. Contraction of the left sternocleidomastoid muscleExplanation
The most likely cause of congenital torticollis in this case is the contraction of the left sternocleidomastoid muscle. Congenital torticollis is a condition characterized by the abnormal positioning of the head, typically with tilting to one side and rotation to the opposite side. The left sternocleidomastoid muscle is responsible for the rotation and tilting of the head to the opposite side. Therefore, the contraction of this muscle would result in the observed head position in the infant.Rate this question:
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- 9.
Which of these agents decreases bone production?
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Vitamin D
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Parathyroid hormone
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Somatomedin
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Testosterone
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Calcitonin
Correct Answer
A. Parathyroid hormoneExplanation
Parathyroid hormone is the correct answer because it functions to increase the levels of calcium in the blood by stimulating the release of calcium from the bones. This process is known as bone resorption, where bone is broken down and calcium is released into the bloodstream. Therefore, parathyroid hormone decreases bone production by promoting the breakdown of bone tissue.Rate this question:
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- 10.
In the steps of excitation-contraction coupling in the skeletal muscle, why can contraction can occur without calcium influxing through Dihydropyridine receptors?
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Calcium is not involved in the contraction of skeletal muscles
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Ryanodine receptors are physically coupled to Dihydropyridine receptors
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Extracellular calcium influxes through voltage-gated calcium channels not Dihydropyridine receptors
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Extracellular calcium influxes through Ryanodine receptors not Dihydropyridine receptors
Correct Answer
A. Ryanodine receptors are physically coupled to Dihydropyridine receptorsExplanation
Ryanodine receptors are physically coupled to Dihydropyridine receptors. This means that when the Dihydropyridine receptors are activated by a change in membrane potential, they physically interact with Ryanodine receptors, leading to the release of calcium from the sarcoplasmic reticulum. This calcium release is essential for muscle contraction to occur. Therefore, even if calcium does not influx through Dihydropyridine receptors, contraction can still occur due to the physical coupling between Dihydropyridine and Ryanodine receptors.Rate this question:
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- 11.
During total hip arthroplasty surgery (total hip replacement) using a posterior approach, the surgeon ligates the profunda femoris artery at its origin. The surgeon also places clamps on the lateral and medial circumflex femoral arteries to allow for removal of the head and neck of the femur. What arteries allow for a sustained flow of blood to the major muscles of the posterior compartment of the thigh while the ligature remains in place?
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Inferior gluteal & medial circumflex femoral
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Superior gluteal & lateral circumflex femoral
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Superior gluteal & medial circumflex femoral
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Femoral & popliteal
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Inferior gluteal & first perforating
Correct Answer
A. Inferior gluteal & first perforatingExplanation
During total hip arthroplasty surgery using a posterior approach, ligating the profunda femoris artery at its origin disrupts the blood supply to the major muscles of the posterior compartment of the thigh. However, the sustained flow of blood to these muscles is maintained by the inferior gluteal artery, which provides a collateral blood supply to the posterior compartment. Additionally, the first perforating artery, a branch of the profunda femoris artery, also helps in maintaining blood flow to the muscles. Therefore, the correct answer is Inferior gluteal & first perforating.Rate this question:
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- 12.
Increasing the frequency of skeletal muscle action potentials causes a tetanic contraction. Why do tetanic contractions produce more tension than a single twitch?
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Calcium is released from the sarcoplasmic reticulum faster than it is reabsorbed
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Calcium influxed from the extracellular stores increases
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The sarcoplasmic reticulum calcium ATPase works slower with increased action potentials
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The rate of a single cross-bridge cycle increases
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Skeletal muscle action potentials summate to produce a large amplitude action potential
Correct Answer
A. Calcium is released from the sarcoplasmic reticulum faster than it is reabsorbedExplanation
Tetanic contractions produce more tension than a single twitch because increasing the frequency of skeletal muscle action potentials causes calcium to be released from the sarcoplasmic reticulum faster than it can be reabsorbed. This leads to a higher concentration of calcium in the muscle fibers, which allows for more cross-bridge formations between actin and myosin filaments. As a result, more force is generated, leading to a stronger contraction.Rate this question:
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- 13.
Dr. Royer You are conducting an annual physical examination of a middle-aged patient. You perform the Patellar Reflex test, and observe strong, sudden, bilateral extension of the knees. What is the pathway followed by the sensory fibers that stimulate this deep tendon reflex?
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Femoral n. L2-L4 ventral rami L2-L4 dorsal roots L2-L4 dorsal root ganglia L2-L4 spinal cord
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Femoral n. L4-L5 ventral rami L4-L5 ventral roots L4-L5 spinal cord
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Obturator n. L2-L4 ventral rami L2-L4 dorsal roots L2-L4 dorsal root ganglia L2-L4 spinal cord
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Obturator n. L2-L4 dorsal rami L2-L4 dorsal roots L2-L4 dorsal root ganglia L2-L4 spinal cord
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Femoral n. L2-L4 dorsal ramiL2-L4 dorsal roots L2-L4 dorsal root ganglia L2-L4 spinal cord
Correct Answer
A. Femoral n. L2-L4 ventral rami L2-L4 dorsal roots L2-L4 dorsal root ganglia L2-L4 spinal cordExplanation
The correct answer is Femoral n. -> L2-L4 ventral rami -> L2-L4 dorsal roots -> L2-L4 dorsal root ganglia -> L2-L4 spinal cord. The pathway of sensory fibers that stimulate the deep tendon reflex is through the femoral nerve, which arises from the L2-L4 ventral rami. These fibers then enter the L2-L4 dorsal roots, where they synapse with neurons in the dorsal root ganglia. From there, the sensory information is transmitted to the L2-L4 spinal cord, resulting in the reflexive extension of the knees.Rate this question:
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- 14.
The accompanying micrograph shows a bone epiphyseal plate undergoing endochondral ossification, a process by which a cartilage model is turned into bone. There are five zones on the picture marked 1-5, and different events are occurring in each of these zones. In which zone do the chondrocytes die?
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Zone 5
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Zone 4
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Zone 3
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Zone 2
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Zone 1
Correct Answer
A. Zone 4Explanation
In endochondral ossification, the chondrocytes in the cartilage model undergo hypertrophy and eventually die. Zone 4 is the zone where the chondrocytes are hypertrophic and starting to die. This zone is also known as the zone of hypertrophy. Therefore, the correct answer is Zone 4.Rate this question:
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- 15.
Dr. Johannessen A single action potential propagating down a motor neuron to the neuromuscular junction will DIRECTLY cause what in the skeletal muscle fiber?
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A depolarizing graded potentia
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An increase in calcium influx from extracellular stores
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An Action potential
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A & C
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A, B & C
Correct Answer
A. A, B & CExplanation
When a single action potential travels down a motor neuron to the neuromuscular junction, it will directly cause a depolarizing graded potential in the skeletal muscle fiber. This graded potential will result in an increase in calcium influx from extracellular stores, which is necessary for muscle contraction. Therefore, all options A, B, and C are correct.Rate this question:
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.JPG "The accompanying micrograph shows a bone epiphyseal plate undergoing endochondral ossification, a process by which a cartilage model is turned into bone. There are five zones on the picture marked 1-5, and different events are occurring in each of these zones. In which zone do the chondrocytes die?")
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