Principles of Human Physiology

A collection of flashcards summarizing key concepts from the principles of human physiology, focusing on muscular and cardiovascular systems.

What are the layers of connective tissue surrounding skeletal muscles?

The layers include the epimysium (outer layer), perimysium (middle layer surrounding fascicles), and endomysium (inner layer surrounding individual muscle fibers).

What are the functions of the epimysium?

The epimysium protects muscles from friction against other muscles and bones and helps maintain the muscle's shape.

What are the functions of the perimysium?

The perimysium provides support and protection to groups of muscle fibers (fascicles) and contains blood vessels and nerves.

What are the functions of the endomysium?

The endomysium insulates individual muscle fibers, providing a supportive environment, and facilitates the exchange of nutrients and waste.

What are the unique features of skeletal muscle compared to a typical cell?

Skeletal muscle fibers are multinucleated, have a striated appearance due to organized myofibrils, and possess a high volume of mitochondria for energy production.

What is the structural and functional unit of muscle?

The structural and functional unit of muscle is the sarcomere, which is the segment between two Z-discs and is responsible for muscle contraction.

How do the proteins in thick and thin filaments regulate muscle contraction and relaxation?

The thick filaments (myosin) and thin filaments (actin, troponin, and tropomyosin) interact during contraction; myosin heads attach to actin, pulling it inward, while troponin and tropomyosin regulate the exposure of binding sites in response to calcium influx.

What are the three functional states of thin filaments?

1. Inactive State: When tropomyosin blocks myosin-binding sites on actin.
2. Activated State: Calcium binds to troponin, causing tropomyosin to move and expose myosin-binding sites.
3. Relaxed State: Calcium is removed, tropomyosin returns to block binding sites, and contraction ceases.

What are the three states in which the myosin heads can exist?

1. Attached State: Myosin heads are firmly attached to actin in a rigor state (no ATP).
2. Release State: Myosin heads are detached from actin after ATP binds.
3. Cocked State: Myosin heads extend after hydrolyzing ATP, ready to perform a power stroke.

What is the difference between calcium-mediated activation of the thin filament and crossbridge-mediated activation of the thin filament?

Calcium-mediated activation involves the binding of calcium to troponin, altering tropomyosin to expose binding sites on actin. Crossbridge-mediated activation occurs when myosin heads attach to the exposed sites and perform power strokes to facilitate contraction.

What are the steps involved in excitation-contraction coupling of skeletal muscles?

1. Action Potential: An action potential travels down a motor neuron.
2. Neuromuscular Junction: Release of acetylcholine triggers muscle fiber depolarization.
3. T-Tubules: The depolarization spreads through T-tubules, triggering calcium release from the sarcoplasmic reticulum.
4. Calcium Release: Calcium binds to troponin, initiating contraction.

What are the steps involved in relaxation of the skeletal muscles?

1. Calcium Pump: Calcium ions are actively transported back into the sarcoplasmic reticulum.
2. Tropomyosin Coverage: Tropomyosin returns to block binding sites on actin.
3. Muscle Fiber Relaxation: The reduction in crossbridge cycling leads to cessation of contraction and relaxation of the muscle fiber.

What are the structural differences between skeletal and cardiac muscles?

Skeletal muscle fibers are long, cylindrical, and multinucleated, while cardiac muscle fibers are branched, striated, and typically have one or two central nuclei.

What are the functional differences between skeletal and cardiac muscles?

Skeletal muscles are under voluntary control and contract rapidly; cardiac muscle is involuntary, has rhythmic contractions, and relies on intrinsic pacemaker cells for contraction.

What are the structural differences between skeletal and smooth muscles?

Skeletal muscles have striations and are multinucleated; smooth muscles lack striations and are spindle-shaped with a single nucleus.

What are the functional differences between skeletal and smooth muscles?

Skeletal muscles contract voluntarily and enable rapid movement; smooth muscles contract involuntarily, controlling functions like digestion and blood vessel diameter.

What are the structural differences between cardiac and smooth muscles?

Cardiac muscle fibers are striated and branched with intercalated discs, while smooth muscle fibers are non-striated, spindle-shaped, and lack intercalated discs.

What are the functional differences between cardiac and smooth muscles?

Cardiac muscle contractions are rhythmic and involuntary, whereas smooth muscle contractions are also involuntary but can be rhythmic or phasic and maintain muscle tone.

What fuels do muscles use during high-intensity physical activities?

During high-intensity activities, muscles primarily use glucose through anaerobic metabolism (glycolysis) due to the limited oxygen supply.

What fuels do muscles use during low-intensity physical activities?

During low-intensity activities, muscles primarily use fatty acids and oxygen through aerobic metabolism for more sustained energy production.

What are the various metabolic pathways used by the body to make ATP?

1. Phosphagen System: Rapid ATP from creatine phosphate.
2. Anaerobic Glycolysis: Fast ATP from glucose without oxygen.
3. Aerobic Respiration: Long-term ATP from glucose, fats, and proteins with oxygen.

How does the body make ATP from carbohydrates, fats, and proteins?

Carbohydrates are broken down into glucose, fats into fatty acids and glycerol, and proteins into amino acids; all converted to acetyl-CoA for entry into the Krebs cycle to produce ATP.

What is the connection between metabolism and respiration?

Metabolism encompasses all chemical reactions in the body, including energy production through ATP synthesis, while respiration refers specifically to the exchange of gases helping to supply oxygen for aerobic metabolism and remove carbon dioxide.

How are the six carbons in glucose ultimately converted into six molecules of carbon dioxide?

Through glycolysis, the Krebs cycle, and subsequent decarboxylation reactions, each of the six carbons in glucose is oxidized and released as CO2 during cellular respiration.

Why does the body use different types of fuels for different physical activities?

The body shifts fuel sources based on activity intensity and duration to optimize energy production; carbohydrates provide quick energy for short bursts, while fats yield more energy over longer durations.

What does an RQ (respiratory quotient) value indicate?

RQ indicates the substrate being metabolized for ATP production; an RQ of approximately 0.7 suggests fat oxidation, while around 1.0 suggests carbohydrate oxidation.

What type of activity and substrate are associated with a low RQ value (around 0.7)?

Low-intensity, long-duration activities rely primarily on fat as the substrate for ATP production, such as walking or casual cycling.

What type of activity and substrate are associated with a high RQ value (around 1.0)?

High-intensity, short-duration activities rely primarily on carbohydrates for rapid ATP production, such as sprinting or heavy lifting.

What are the major differences between fast, slow, and intermediate muscle fibers?

1. Fast Fibers: Contract quickly, fatigue quickly, primarily use anaerobic pathways.
2. Slow Fibers: Contract slowly, fatigue resistant, primarily use aerobic pathways.
3. Intermediate Fibers: Have characteristics of both fast and slow fibers, moderate contraction speed and fatigue resistance.

How are muscle contractions classified based on muscle length?

Muscle contractions can be classified as isometric (length remains the same while generating force) or isotonic (muscle changes length, can be concentric or eccentric).

How are muscle contractions classified based on the load?

Contractions can be classified as isotonic (muscle shortens or lengthens against a load) or isometric (muscle generates force without changing length against an immovable load).

What are the four ways skeletal muscle force can be regulated?

1. Recruitment of Motor Units: Activating more motor units increases force.
2. Frequency of Stimulation: Increased frequency boosts calcium availability, leading to stronger contractions.
3. Muscle Fiber Diameter: Larger fibers generate more force.
4. Muscle Length: Optimal length allows for maximum overlap of actin and myosin for efficient force generation.

What are the two methods of fine-tuning force generation in both cardiac and skeletal muscles?

1. Recruitment of muscle fibers: More fibers are recruited to increase force.
2. Increased frequency of stimulation: Higher stimulation rates enhance contractile force. Unique features include that cardiac muscle fibers are interconnected, allowing for synchronized contraction, while skeletal muscles are voluntary and can vary recruitment more selectively.

How does the muscular system impact other body systems?

The muscular system enables movement, affecting the skeletal (movement of bones), digestive (peristalsis), circulatory (pumping blood), reproductive (movement during childbirth), and nervous systems (coordination of movement and reflexes).

What are the main types of blood vessels that regulate blood flow to and from the heart?

1. Arteries: Carry oxygenated blood away from the heart (except pulmonary arteries).
2. Veins: Carry deoxygenated blood back to the heart (except pulmonary veins).
3. Capillaries: Microscopic vessels where nutrient and gas exchange occurs between blood and tissues.

What are the functions of the cardiac valves?

Cardiac valves ensure unidirectional blood flow through the heart, preventing backflow during contractions. Key valves include:

1. Atrioventricular Valves: Tricuspid (right side) and mitral (left side) valves regulate blood flow from atria to ventricles.
2. Semilunar Valves: Pulmonary valve (to the lungs) and aortic valve (to the body) regulate flow from ventricles to arteries.

What are the components of the cardiac conduction system?

1. Sinoatrial (SA) Node: Pacemaker that initiates electrical impulses, causing atrial contraction.
2. Atrioventricular (AV) Node: Receives impulses from SA node and sends them to the ventricles after a delay.
3. Bundle of His: Pathway for impulses from AV node to ventricles.
4. Purkinje Fibers: Distribute electrical impulses throughout the ventricles, causing contraction.

What are the two types of cells in the heart muscle and their functions?

1. Cardiac Muscle Cells (Myocytes): Contract to pump blood throughout the body, comprising the heart’s contractile force.
2. Specialized Pacemaker Cells: Generate and conduct electrical impulses that trigger heart contractions, ensuring coordinated beating.

How do autorhythmic cells generate an action potential?

Autorhythmic cells generate action potentials through a gradual depolarization due to ion channel activity, particularly through the influx of sodium (Na+) and calcium (Ca2+) ions, leading to spontaneous firing and initiating the heartbeat.

What are the steps involved in the action potential of the pacemaker cells?

1. Pacemaker Potential: Slow depolarization due to Na+ influx and reduced K+ permeability.
2. Threshold Potential: Reaches a critical level, opening voltage-gated Ca2+ channels.
3. Depolarization Phase: Rapid influx of Ca2+ leads to a strong depolarization.
4. Repolarization Phase: Ca2+ channels close, and K+ channels open, allowing K+ efflux, leading to repolarization.

How does the action potential of pacemaker cells differ from contractile cells?

Pacemaker cells have a spontaneous depolarization and shorter action potentials, while contractile cells have a stable resting potential, longer action potentials, and involve a plateau phase, critical for effective contraction.

What are the notable parts of the electrocardiogram (ECG/EKG)?

Key components of an ECG include:

1. P Wave: Atrial depolarization.
2. QRS Complex: Ventricular depolarization and atrial repolarization.
3. T Wave: Ventricular repolarization.

How do the various parts of the electrocardiogram relate to the cardiac cycle?

1. P Wave: Corresponds with atrial contraction (systole).
2. QRS Complex: Indicates ventricular contraction (systole).
3. T Wave: Represents ventricular relaxation (diastole).

Give an example of a pathology related to electrical activity of the heart.

A common pathology is atrial fibrillation, characterized by disorganized electrical signals leading to irregular and often rapid heart rate, increasing the risk of stroke and other heart-related complications.

How can electrocardiogram readings indicate various pathologies of the heart?

1. ST Segment Elevation: Indicates myocardial infarction (heart attack).
2. Prolonged QT Interval: Suggests risk of serious arrhythmias, potentially leading to sudden cardiac events.

How do blood pressure and blood volume change in the ventricles and atria during the cardiac cycle?

As the heart contracts:

1. Atria: Blood volume decreases as they contract, and pressure increases, pushing blood into ventricles.
2. Ventricles: Blood volume increases during diastole and decreases during systole, with pressure rising significantly during contraction.

How is the cardiac cycle represented using a pressure-volume loop?

A pressure-volume loop represents the relationship between ventricular pressure and volume during the cardiac cycle, illustrating phases of filling (diastole), isovolumetric contraction, ejection (systole), and isovolumetric relaxation; useful for assessing cardiac function and efficiency.

How does the autonomic nervous system regulate heart rate?

The autonomic nervous system alters heart rate via sympathetic (increases heart rate) and parasympathetic (decreases heart rate) pathways.

What role do smooth muscles play in blood vessels?

Smooth muscles regulate vessel diameters, controlling blood flow and pressure through vasoconstriction and vasodilation.

How do blood vessels branch from the aorta to capillaries?

Blood vessels branch from the aorta into large arteries, smaller arterioles, and then into capillary beds, facilitating nutrient exchange.

How does blood pressure change from the aorta to the vena cava?

Blood pressure decreases progressively from the aorta to the vena cava due to resistance and branching of blood vessels.

How does blood flow rate change from the aorta to the vena cava?

Blood flow rate remains steady in large vessels but slows in capillaries, enhancing nutrient exchange.

How does resistance to blood flow vary from the aorta to the vena cava?

Resistance increases in smaller arterioles and decreases in larger veins, affecting overall circulation.

How do vessel diameters change from the aorta to capillaries?

Diameters decrease in smaller branches, then increase at the capillary level due to increased total cross-sectional area.

How does branching of blood vessels affect cross-sectional area and pressure?

Branching increases total cross-sectional area, resulting in decreased blood pressure at capillary beds for efficient exchange.

What is the pressure-flow-resistance relationship in circulation?

Flow (Q) equals pressure (P) divided by resistance (R): Q = P/R; thus, increased resistance reduces flow.

What are the major functions of blood?

Blood functions include transportation of oxygen, nutrients, waste products, hormones; regulation of body temperature, pH, and fluid balance; protection against infections and blood loss.

What are the components of blood and their proportions?

Blood consists of:

1. Plasma: ~55%
2. Red Blood Cells (RBCs): ~45%
3. White Blood Cells (WBCs) and Platelets: <1% combined.

What are the structural features and functions of red blood cells (RBCs)?

RBCs are biconcave discs, lack nuclei, and contain hemoglobin, allowing them to transport oxygen and carbon dioxide efficiently.

What are the structural features and functions of white blood cells (WBCs)?

WBCs have nuclei and are categorized into types (e.g., lymphocytes, neutrophils) that help defend the body against infections and foreign substances.

What are the structural features and functions of platelets?

Platelets are small, cell fragments derived from megakaryocytes, playing a crucial role in blood clotting and wound healing.

What are the steps involved in the synthesis of red blood cells (erythropoiesis)?

1. Stimulus: Low oxygen levels.
2. EPO production: Kidneys release erythropoietin.
3. Stem Cell Differentiation: Hematopoietic stem cells develop into RBCs in bone marrow.
4. Maturation: Cells acquire hemoglobin and lose nuclei.

What are the steps involved in the breakdown of red blood cells?

1. Aging RBCs: RBCs identified by macrophages.
2. Phagocytosis: Macrophages engulf and digest RBCs.
3. Hemoglobin Breakdown: Hemoglobin is split into heme and globin.

What are the steps involved in heme recycling?

1. Heme conversion: Heme is converted into bilirubin.
2. Transport: Bilirubin is transported to the liver.
3. Excretion: Bilirubin is excreted in bile or urine.

What is the structure and function of hemoglobin?

Hemoglobin is a protein made of four polypeptide chains and heme groups, binding oxygen in the lungs and releasing it in tissues; also carries carbon dioxide.

How is red blood cell production regulated compared to white blood cell production?

RBC production is primarily regulated by erythropoietin based on oxygen needs, whereas WBC production is responsive to infection and inflammation, involving various growth factors.

What factors are required to produce different components of blood?

Factors include hormones (e.g., erythropoietin for RBCs), cytokines (for WBCs), and nutrients like iron, vitamins B12, and folic acid for overall blood production.