BIOL 180 Exam 3 Study Notes
Structure of Muscle Types
Question 1: Which of the following structures is found in all three types of muscle covered in class?
Answer: b) sarcoplasmic reticulum (SR)
Explanation: The sarcoplasmic reticulum (SR) is a specialized endoplasmic reticulum that stores and releases calcium ions, which are crucial for muscle contraction in all muscle types (skeletal, cardiac, and smooth). Sarcomeres and T-tubules are characteristic of skeletal and cardiac muscle but absent in smooth muscle. Neuromuscular junctions are specific to skeletal muscle. Gap junctions are found in cardiac and smooth muscle, but not typically in skeletal muscle in the context of individual fiber contraction.
Question 2: Arteries are compliant and elastic. Why?
Answer: e) A & B only. (They need to stretch when blood from the heart is pumped directly into them and they need to recoil after a large amount of blood is pumped into them.)
Explanation: Arteries are compliant because they can stretch to accommodate the surge of blood during systole and elastic because they recoil to maintain blood pressure and flow during diastole. This stretching and recoiling ensures continuous blood flow and dampens pressure fluctuations.
Question 3: If a person with a normal resting heart rate of 60 bpm and stroke volume of 300 mL became severely dehydrated and their stroke volume decreased to 200 mL, what would happen to their heart rate in order to maintain the same cardiac output?
Answer: d) it would increase to 90 bpm
Explanation: Cardiac output (CO) is calculated as heart rate (HR) multiplied by stroke volume (SV). If the initial CO is 60 \text{ bpm} \times 300 \text{ mL} = 18000 \text{ mL/min}. To maintain this CO with a decreased SV of 200 mL, the new HR must be 18000 \text{ mL/min} / 200 \text{ mL} = 90 \text{ bpm}.
Question 4: Why is blood pressure higher in systemic circulation than in pulmonary circulation?
Answer: b) The systolic circulation has to pump blood to the entire body.
Explanation: Systemic circulation is responsible for pumping blood to the entire body, which requires overcoming much greater resistance and distance compared to pulmonary circulation, which only pumps blood a short distance to the lungs. Therefore, higher pressure is needed in the systemic circuit.
Question 5: Of the following locations in the body, which has the HIGHEST PCO₂?
Answer: d) Mitochondria of body cells
Explanation: Carbon dioxide (CO₂) is a waste product of cellular respiration, which primarily occurs in the mitochondria. Therefore, the partial pressure of CO₂ (PCO₂) will be highest directly at the site of its production, within the mitochondria of active body cells, before it diffuses into the bloodstream.
Question 6: Key ways that smooth muscle contraction differs from skeletal muscle contraction:
Answer: d) A & C. (Ca²⁺ interacts (indirectly) with myosin, rather than with actin, and there are two sources of Ca²⁺ in smooth muscle.)
Explanation: In smooth muscle, Ca^{2+} indirectly interacts with myosin by binding to calmodulin, which then activates myosin light chain kinase (MLCK), leading to myosin phosphorylation. Smooth muscle also has two sources of Ca^{2+}: influx from the extracellular fluid and release from the sarcoplasmic reticulum (SR).
Electrocardiogram (ECG) Interpretation
Question 7: An ECG with many short, irregular P waves suggests that a patient's…
Answer: d) atria are contracting rapidly & irregularly (atrial fibrillation).
Explanation: The P wave on an ECG represents atrial depolarization. Many short, irregular P waves are characteristic of atrial fibrillation, a condition where the atria beat chaotically and irregularly.
Venous Return Mechanisms
Question 8: Why do veins in your legs contain skeletal muscle pump with valves?
Answer: d) all of the above. (to pump blood back to the heart, to prevent blood from "leaking" (flowing) backwards through your veins, and to increase stroke volume and cardiac output.)
Explanation: The skeletal muscle pump compresses veins, pushing blood towards the heart. Valves prevent the backflow of blood due to gravity. Both actions contribute to increased venous return, which in turn increases preload, stroke volume, and ultimately cardiac output.
Capillary Fluid Levels
Question 9: The amount of fluid in the capillaries stays approximately the same because of…
Answer: c) net filtration pressure; the net movement of fluid out of or back into capillaries = 0 because of A & B.
Explanation: Fluid movement in and out of capillaries is governed by the balance between hydrostatic pressure (forcing fluid out) and colloid osmotic pressure (drawing fluid back in). Under normal conditions, these opposing forces are roughly balanced, resulting in a net filtration pressure of approximately zero, meaning net fluid movement is balanced.
Smooth Muscle Relaxation Processes
Question 10: What two processes cause smooth muscle to relax?
Answer: c) calmodulin is inactivated when Ca²⁺ is removed & myosin phosphatase dephosphorylates myosin.
Explanation: Smooth muscle relaxation requires the removal of Ca^{2+} from the cytosol, which inactivates calmodulin. Simultaneously, myosin phosphatase dephosphorylates the myosin light chains, preventing myosin from binding to actin, thus leading to relaxation.
Muscle Contraction and ATP
Question 11: Which of the following happens immediately after myosin in skeletal muscle binds a molecule of ATP?
Answer: a) the myosin detaches from actin.
Explanation: In skeletal muscle, the binding of a new ATP molecule to the myosin head causes the myosin head to detach from the actin filament, an essential step in the cross-bridge cycle.
Pacemaker Potential Mechanisms
Question 12: "Pacemaker" node cells control heartbeat by undergoing cycles of depolarization. This process is also called the pacemaker potential.
Answer: b) Leakage of Na⁺ & Ca²⁺ through ion channels until AP threshold is reached.
Explanation: The pacemaker potential (slow depolarization) in pacemaker cells is primarily driven by a slow, constant leakage of Na^+ (via 'funny' channels) and Ca^{2+} (via T-type calcium channels) until the action potential threshold is reached.
Ryanodine Receptor Activation
Question 13: The direct stimulus for opening ryanodine receptors in skeletal muscle is…
Answer: c) action potential propagation down transverse (T) tubules to the sarcoplasmic reticulum (SR).
Explanation: In skeletal muscle, when an action potential propagates down the T-tubules, it causes a conformational change in dihydropyridine receptors (DHP receptors), which are mechanically linked to ryanodine receptors on the SR. This mechanical coupling directly opens the ryanodine receptors, leading to Ca^{2+} release.
Reflex Arc Components
Question 14: Which of the following is NOT an effector in the reflex arc that responds to a sudden drop in blood pressure?
Answer: c) diaphragm and intercostal muscles.
Explanation: A reflex arc responding to a drop in blood pressure (e.g., baroreceptor reflex) typically involves effectors that regulate heart rate, contractility, and peripheral vascular resistance (SA node, cardiac muscle, smooth muscle of arterioles and veins). The diaphragm and intercostal muscles are involved in breathing, not direct regulation of blood pressure in this reflex.
Understanding Pulmonary Edema
Question 15: What is TRUE about Pulmonary Edema?
Answer: e) All of the above.
Explanation: Pulmonary edema is characterized by fluid accumulation in the lungs, impairing gas exchange. It can result from increased blood pressure in pulmonary capillaries (disrupting hydrostatic pressure), left ventricular failure, or severe inflammation due to infection.
Skeletal Muscle Relaxants
Question 16: A drug that acts as a skeletal muscle relaxant would…
Answer: b) block nicotinic ACh receptors on the outer membrane of the muscle cell.
Explanation: Skeletal muscle contraction is initiated by acetylcholine (ACh) binding to nicotinic ACh receptors. Blocking these receptors would prevent the muscle cell from depolarizing in response to nerve signals, thus causing relaxation.
Metabolic Pathways in Muscle
Question 17: Which of the following metabolic pathways in skeletal muscle do NOT require oxygen?
Answer: d) both A and B. (creatine phosphate cycle and glycolysis)
Explanation: The creatine phosphate cycle rapidly regenerates ATP for short bursts of activity without oxygen. Glycolysis also produces ATP by breaking down glucose without oxygen. The citric acid cycle and electron transport chain require oxygen.
Diaphragm and Intercostal Muscle Relaxation
Question 18: When the diaphragm and intercostal muscles relax…
Answer: c) air flows out of the lungs.
Explanation: Relaxation of the diaphragm and intercostal muscles during quiet expiration leads to a decrease in lung volume, which increases the alveolar pressure above atmospheric pressure. This pressure gradient causes air to flow out of the lungs.
Blood Vessel Structure and Function
Question 19: These blood vessels contain smooth muscle and can constrict to restrict blood flow to tissues or organs that are not needed during your body's sympathetic nervous system response:
Answer: b) arterioles.
Explanation: Arterioles are the primary resistance vessels in the circulatory system. Their smooth muscle walls can constrict or dilate to regulate blood flow to specific capillary beds, playing a crucial role in directing blood during sympathetic responses.
Effects of Hypoventilation
Question 20: Which of the following about hypoventilation is TRUE?
Answer: c) it causes an increase in [H^+].
Explanation: Hypoventilation means less CO₂ is expelled, leading to an increase in blood PCO₂. Increased PCO₂ shifts the bicarbonate buffer system equilibrium, producing more carbonic acid (H₂CO₃), which dissociates into H^+ and bicarbonate ions, thus causing an increase in [H^+] (acidosis).
Weight Resistance Impact on Muscle
Question 21: You are at the gym doing bicep curls with 5-lb weights. Which of the following will INCREASE in your bicep muscles if you repeat the same exercise with 10-lb weights?
Answer: d) twitch duration.
Explanation: Increasing the load on a muscle generally leads to an increase in the twitch duration, meaning the muscle contraction lasts longer to overcome the greater resistance.
Atherosclerosis Effects
Question 22: Which of the following statements about atherosclerosis is TRUE?
Answer: d) it reduces stroke volume.
Explanation: Atherosclerosis involves hardening and narrowing of arteries, which decreases arterial compliance and increases afterload on the heart due to higher resistance. This increased afterload, combined with potentially impaired ventricular function, can lead to a reduced stroke volume and typically causes hypertension.
Ca²⁺ Binding Mutations
Question 23: What would happen to someone with a mutation that prevents Ca²⁺ from binding to troponin?
Answer: a) their skeletal muscles would not contract.
Explanation: In skeletal muscle, Ca^{2+} binding to troponin is the crucial step that moves tropomyosin away from the myosin-binding sites on actin, allowing myosin to bind and initiate contraction. If Ca^{2+} cannot bind to troponin, these sites remain blocked, and skeletal muscle contraction cannot occur.
Minute Ventilation and Alveolar Ventilation Rates
Question 24: José breaths 10 times per minute with a tidal volume of 500 mL per breath, while Lam is breathing 15 breaths per minute with a tidal volume of 300 mL per breath. Which of the following is TRUE, based on this information?
Answer: d) José has a high minute ventilation rate (MVR) than Lam.
Explanation: José's Minute Ventilation Rate (MVR) is 500 \text{ mL} \times 10 \text{ bpm} = 5000 \text{ mL/min}. Lam's MVR is 300 \text{ mL} \times 15 \text{ bpm} = 4500 \text{ mL/min}. Therefore, José has a higher MVR than Lam.
Blood Flow in the Heart
Question 25: Deoxygenated blood enters the atrium of the heart through the…
Answer: b) right; vena cavae; rest of the body.
Explanation: Deoxygenated blood from the systemic circulation (rest of the body) returns to the heart via the superior and inferior vena cavae, which empty into the right atrium.
Muscle Contraction During Breathing
Question 26: Contraction of the pectoral and neck muscles occurs during…
Answer: c) forced inspiration.
Explanation: During forced inspiration, accessory muscles like the pectoralis minor and sternocleidomastoid (neck muscles) contract to maximize lung expansion, beyond what happens in passive inspiration.
Cardiac Electrical Impulse Control
Question 27: The part of the heart that controls the electrical impulses of your heartbeat is the…
Answer: c) Sinoatrial (SA) node.
Explanation: The Sinoatrial (SA) node is the natural pacemaker of the heart, initiating the electrical impulses that determine the heart rate.
Inhibiting Acetylcholinesterase Effects
Question 28: If someone took a drug that inhibited the production of acetylcholinesterase enzyme, what would happen?
Answer: c) Their skeletal muscles would stay contracted.
Explanation: Acetylcholinesterase (AChE) breaks down acetylcholine (ACh) at the neuromuscular junction, allowing muscles to relax. Inhibiting AChE would cause ACh to remain in the synapse longer, continuously stimulating nicotinic receptors and leading to prolonged skeletal muscle contraction (tetanus).
Myasthenia Gravis Treatment Query
Question 29: Could the drug in the above question be used to treat someone with Myasthenia Gravis (a disease in which antibodies destroy nicotinic ACh receptors on skeletal muscle cells)? Why?
Answer: a) Yes, because ACh would stay in the synapse longer and bind to any nicotinic receptors.
Explanation: Myasthenia Gravis is characterized by a reduction in functional nicotinic ACh receptors. By inhibiting acetylcholinesterase, ACh remains in the synaptic cleft for a longer duration, increasing the probability that it will bind to the remaining functional receptors, thereby improving muscle contraction and reducing symptoms of weakness.
Hemoglobin and Oxygen Affinity
Question 30: Hemoglobin has the highest affinity for oxygen when…
Answer: a) all four subunits are bound.
Explanation: Hemoglobin exhibits cooperative binding. Its affinity for oxygen increases progressively with each successive oxygen molecule that binds. Therefore, it has the highest affinity when all four of its heme subunits are already bound to oxygen.
Oxygen Delivery Mechanism
Question 31: Hemoglobin is good at delivering oxygen to tissues in the body that need it because…
Answer: d) A & B. (O₂ stays attached to hemoglobin until it reaches areas with low partial pressure for O₂, and hemoglobin loses affinity for O₂ as it begins to lose O₂ where it is needed.)
Explanation: Hemoglobin efficiently delivers oxygen because it stays attached to oxygen in high P₀₂ areas and releases it in areas of low P₀₂ (where oxygen is needed). As it loses one oxygen molecule, its affinity for the remaining oxygen molecules decreases, facilitating further release (Bohr effect).
Heart Murmur Causes
Question 32: A heart murmur heard during systole could be produced by…
Answer: e) either A or C. (a stenotic semilunar valve or an insufficient atrioventricular (AV) valve.)
Explanation: During systole (ventricular contraction), a stenotic semilunar valve (narrowed aortic or pulmonary valve) would impede forward blood flow, creating a murmur. An insufficient atrioventricular (AV) valve (mitral or tricuspid valve) would allow blood to leak backward into the atria, also creating a murmur during systole.
Sequence of Muscle Activation Steps
Question 33: Of the following steps that occur after a motor neuron releases acetylcholine, which happens FIRST (before the others)?
Answer: d) the muscle cell membrane is depolarized.
Explanation: Following acetylcholine release and binding to receptors at the neuromuscular junction, the first event in the muscle cell is the depolarization of its membrane (generation of an end-plate potential, leading to an action potential).
Vital Capacity Measurement
Question 34: Your yoga instructor asks you to take a really deep breath in, then breathe out as much air as you can out of the lungs. The volume of air moved during this process is your…
Answer: c) vital capacity.
Explanation: Vital capacity is the maximum amount of air a person can exhale after a maximum inhalation. This precisely describes the action of taking a deep breath in and then breathing out as much air as possible.
Goblet Cells Function
Question 35: What is the function of goblet cells?
Answer: a) They produce mucus that allows you to clear pathogens and particles from the airways.
Explanation: Goblet cells produce and secrete mucus, which traps inhaled particles, dust, and pathogens in the airways, contributing to the mucociliary escalator defense mechanism that clears the respiratory tract.
Impact of Blocking L-type Channels
Question 36: Which of the following would happen if you blocked L-type channels in cardiac muscle?
Answer: b) the force of contractions will be reduced.
Explanation: L-type calcium channels are crucial in cardiac muscle for the influx of extracellular Ca^{2+}, which triggers further Ca^{2+} release from the SR (calcium-induced calcium release). Blocking these channels would significantly reduce the amount of Ca^{2+} available, thereby reducing the force of contraction.
Arteriole Contraction Effects
Question 37: What happens if the smooth muscle in the wall of a single arteriole contracts?
Answer: b) blood flow into the capillary bed fed by the arteriole decreases.
Explanation: Contraction of smooth muscle in an arteriole causes vasoconstriction, which narrows the lumen of the arteriole. This increases resistance to blood flow in that specific arteriole, thereby reducing blood flow into the capillary bed it supplies.
Lung Surfactant Functions
Question 38: What is the function of lung surfactant?
Answer: e) A & B. (Surfactant reduces tension and cohesion between H₂O molecules, and surfactant makes your lungs compliant.)
Explanation: Lung surfactant reduces the surface tension of the fluid lining the alveoli, preventing them from collapsing. This reduction in surface tension also significantly increases the compliance of the lungs, making them easier to inflate.
Interpleural Fluid Necessity
Question 39: What might happen to a person that doesn't have interpleural fluid?
Answer: b) They would have trouble breathing because there would be friction between the thoracic wall and the lungs.
Explanation: The interpleural fluid acts as a lubricant, allowing the parietal and visceral pleurae to slide smoothly past each other during breathing. Without it, friction would increase, making breathing painful and difficult and impacting the mechanical coupling of lungs to the thoracic wall.
Cardiac Output Influencing Factors
Question 40: Which of the following would NOT increase cardiac output?
Answer: c) Increasing afterload.
Explanation: Increasing afterload (the resistance against which the ventricles must pump) makes it harder for the heart to eject blood, thereby decreasing stroke volume and thus cardiac output. Administering epinephrine, increasing preload, increasing heart rate, or increasing contractility all generally increase cardiac output.
Alterations in Ventilation Rate
Question 41: Which of the following can alter your ventilation rate?
Answer: e) all of these.
Explanation: Ventilation rate is sensitive to changes in [H^+] (pH), partial pressures of O₂ and CO₂ (detected by chemoreceptors in the brain and periphery), and can also be consciously controlled by thoughts from the cerebral cortex.
Cardiac vs. Skeletal Muscle Contraction
Question 42: What is different about cardiac muscle contraction compared to skeletal muscle?
Answer: e) Both B & C. (Voltage-gated Ca^{2+} channels depolarize the cell and open ligand-gated Ca^{2+} channels in the SR, and the L-type Ca^{2+} channels take a long time to close, so contraction lasts a while.)
Explanation: In cardiac muscle, the influx of extracellular Ca^{2+} through voltage-gated L-type Ca^{2+} channels during the plateau phase of the action potential acts as the trigger for the release of more Ca^{2+} from the SR. Also, the prolonged opening of L-type Ca^{2+} channels creates a long plateau phase, leading to a longer contraction and preventing tetanus.
Bonus Questions
Bonus Question 43: Your "fight-or-flight" sympathetic nervous system response is immediately enacted. What happens physiologically?
Answer: e) Your veins & arterioles constrict, your airways dilate, your heart pumps more blood per contraction.
Explanation: During a 'fight-or-flight' response, sympathetic stimulation causes veins and arterioles to constrict (redistributing blood), airways (bronchioles) to dilate (increasing air intake), and heart rate and contractility to increase, leading to more blood pumped per contraction.
Bonus Question 44: As Smooshie lunges at a bird, what is happening in her contracting muscles?
Answer: d) All of the above.
**Explanation