Important questions for Universi ty by Gagre sir , solution

 ## General Physiology

### Long Answer Questions

1. **Transport Mechanisms Across the Cell Membrane**

   The cell membrane, or plasma membrane, is a dynamic structure that plays a crucial role in controlling the movement of substances in and out of cells. The various mechanisms of transport include:

   - **Passive Transport**:

     - **Simple Diffusion**: Molecules move from an area of higher concentration to an area of lower concentration directly through the lipid bilayer. This process does not require energy. Examples include the diffusion of oxygen and carbon dioxide.

     - **Facilitated Diffusion**: Utilizes specific transport proteins to move substances down their concentration gradient. These proteins include channel proteins and carrier proteins. An example is the glucose transport into cells.

     - **Osmosis**: A specific type of passive transport involving the movement of water molecules through a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration.

   - **Active Transport**:

     - **Primary Active Transport**: Direct use of metabolic energy (ATP) to transport molecules against their concentration gradient. The Na+/K+ pump (sodium-potassium pump) is a classic example, maintaining the electrochemical gradient across the cell membrane by moving three sodium ions out of the cell and two potassium ions into the cell against their respective concentration gradients.

     - **Secondary Active Transport (Co-transport)**: Uses the energy from the electrochemical gradient established by primary active transport to move other substances. This includes symporters, which move substances in the same direction, and antiporters, which move substances in opposite directions. An example is the glucose-sodium symporter in the intestinal cells.

   - **Endocytosis and Exocytosis**:

     - **Endocytosis**: The process by which cells engulf large particles, liquids, or other cells. This includes phagocytosis ("cell eating") for solids, pinocytosis ("cell drinking") for liquids, and receptor-mediated endocytosis for specific molecules.

     - **Exocytosis**: The process by which cells expel materials using vesicles that fuse with the plasma membrane. This is critical for processes like neurotransmitter release at synapses and secretion of hormones.

   - **Ion Channels and Transporters**:

     - **Ion Channels**: Protein channels that allow specific ions to pass through the membrane in response to various stimuli, such as voltage changes (voltage-gated channels), ligand binding (ligand-gated channels), or mechanical stress (mechanically-gated channels).

     - **Transporters**: Proteins that facilitate the movement of ions and small molecules across the membrane. These include uniporters, which move a single substance, and co-transporters (symporters and antiporters).

2. **Action Potential**

   - **Definition**: An action potential is a rapid and temporary change in the electrical membrane potential of a cell, which allows it to communicate information quickly over long distances. Action potentials are fundamental to the function of neurons and muscle cells.

   - **Ionic Basis**:

     - **Resting Membrane Potential (RMP)**: Typically around -70mV in neurons, it is the electrical potential difference across the plasma membrane when the cell is in a non-excited state. It is mainly established by the differential permeability of the membrane to K+ and Na+ ions, and the action of the Na+/K+ pump, which maintains higher concentrations of Na+ outside the cell and K+ inside the cell.

     - **Depolarization**: Triggered when the cell membrane potential becomes less negative (more positive) due to the influx of Na+ ions through voltage-gated Na+ channels. Once the membrane potential reaches a threshold (around -55mV), a rapid opening of these channels occurs, leading to a further influx of Na+ and a spike in membrane potential.

     - **Repolarization**: Occurs as Na+ channels inactivate and voltage-gated K+ channels open, allowing K+ to exit the cell, returning the membrane potential back toward the resting level.

     - **Hyperpolarization**: A phase where the membrane potential temporarily becomes more negative than the resting potential due to the continued efflux of K+ through slowly closing K+ channels.

     - **Return to RMP**: The membrane potential is restored to its resting state by the Na+/K+ pump and leak channels, ready for the next action potential.

   - **Resting Membrane Potential (RMP)**: The RMP is essential for the maintenance of the excitability of the neuron. It is generated by the unequal distribution of ions across the cell membrane, primarily maintained by the Na+/K+ pump, which actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell against their concentration gradients, using ATP as an energy source.

### Short Notes

1. **Cell Membrane**: The cell membrane, also known as the plasma membrane, is a phospholipid bilayer with embedded proteins that enclose the cell's contents and regulates the passage of substances into and out of the cell. It is semi-permeable, allowing selective passage of ions and molecules, and plays a critical role in cell communication and signaling.

   

2. **Mitochondria**: Organelles known as the powerhouses of the cell, mitochondria are responsible for producing ATP through oxidative phosphorylation. They have their own DNA and are involved in energy metabolism, apoptosis, and calcium storage.

   

3. **Endoplasmic Reticulum (ER)**: A network of membranous tubules within the cytoplasm of eukaryotic cells. The rough ER, studded with ribosomes, is involved in protein synthesis and processing. The smooth ER, lacking ribosomes, is involved in lipid synthesis, detoxification, and calcium storage.

4. **Homeostasis**:

   - **Positive Feedback Mechanism**: Enhances the original stimulus, leading to an amplified response. Example: blood clotting, where each step of the process releases chemicals that further accelerate the process.

   - **Negative Feedback Mechanism**: Counteracts changes, helping to maintain equilibrium. Example: regulation of blood glucose levels, where an increase in blood glucose triggers insulin release, promoting glucose uptake by cells and decreasing blood glucose levels.

5. **Simple Diffusion vs. Facilitated Diffusion**:

   - **Simple Diffusion**: Passive movement of molecules from an area of higher concentration to an area of lower concentration, directly through the lipid bilayer. No energy or carrier proteins are involved.

   - **Facilitated Diffusion**: Also passive, but involves specific carrier proteins or channels that help transport substances across the cell membrane along the concentration gradient.

6. **Active Transport**: The movement of molecules against their concentration gradient, requiring energy in the form of ATP. Active transport is essential for maintaining concentration gradients of ions across the cell membrane. Examples include the Na+/K+ pump and the calcium pump in muscle cells.

7. **Saltatory Conduction**: The process by which action potentials jump from one Node of Ranvier to the next in myelinated axons. This type of conduction increases the speed of nerve impulse transmission compared to continuous conduction in unmyelinated fibers.

## Muscle Physiology

### Long Answer Questions

1. **Sarcomere and Skeletal Muscle Contraction**

   - **Sarcomere**: The basic functional unit of striated muscle fibers, defined by Z lines. Each sarcomere contains interdigitating thick (myosin) and thin (actin) filaments. The arrangement of these filaments creates the striated appearance of skeletal muscle.

   

   - **Molecular Basis of Contraction**:

     - **Sliding Filament Theory**: Muscle contraction occurs when myosin heads bind to actin, forming cross-bridges and pulling the actin filaments toward the center of the sarcomere. This process is powered by ATP hydrolysis.

     - **Role of Calcium**: Calcium ions released from the sarcoplasmic reticulum bind to troponin, causing a conformational change in tropomyosin, which exposes the binding sites on actin for myosin heads.

     - **ATP Role**: ATP is required for the attachment of myosin to actin, the power stroke that moves actin, and the detachment of myosin from actin. Without ATP, myosin remains bound to actin, leading to rigor mortis.

   - **Myasthenia Gravis**: An autoimmune disorder characterized by the production of antibodies against acetylcholine receptors at the neuromuscular junction. This impairs the ability of acetylcholine to stimulate muscle contraction, leading to muscle weakness and fatigue.

2. **Mechanism of Muscle Contraction**:

   - **Excitation-Contraction Coupling**: The sequence of events from the generation of an action potential in the muscle cell membrane to the sliding of myofilaments. This includes the release of Ca2+ from the sarcoplasmic reticulum, the binding of Ca2+ to troponin, and the subsequent cross-bridge cycling between actin and myosin.

   - **Myasthenia Gravis or Rigor Mortis**:

     - **Myasthenia Gravis**: As previously described, results in progressive muscle weakness.

     - **Rigor Mortis**: Occurs post-mortem due to the lack of ATP, which prevents the detachment of myosin heads from actin, resulting in muscle stiffness.

### Short Notes

1. **Neuromuscular Junction**: The synapse between a motor neuron and a skeletal muscle fiber. It is the site where acetylcholine is released from the nerve terminal, crosses the synaptic cleft, and binds to receptors on the muscle membrane, triggering an action potential that leads to muscle contraction.

2. **Myasthenia Gravis**: As described, it

 is an autoimmune disorder affecting the neuromuscular junction, characterized by muscle weakness that worsens with activity and improves with rest. Treatment often involves acetylcholinesterase inhibitors, immunosuppressants, and sometimes thymectomy.

3. **Properties of Skeletal Muscle**: 

   - **Excitability**: Ability to respond to stimuli.

   - **Contractility**: Ability to contract and generate force.

   - **Extensibility**: Ability to be stretched.

   - **Elasticity**: Ability to return to original length after being stretched or contracted.

## Cardiovascular System (CVS)

### Long Answer Questions

1. **Properties of Cardiac Muscle**

   - **Automaticity**: The ability of cardiac muscle cells to depolarize spontaneously and initiate an action potential without external stimuli, primarily due to the SA node.

   - **Excitability**: The ability to respond to an electrical stimulus.

   - **Conductivity**: The ability to transmit an electrical impulse from one cell to another.

   - **Contractility**: The ability to contract and generate force.

   - **Rhythmicity**: The regular and consistent generation of action potentials by the SA node, resulting in coordinated contractions.

2. **Cardiac Impulse Origin and Spread**

   - **Sinoatrial (SA) Node**: The primary pacemaker of the heart located in the right atrium. It generates action potentials at a regular rate, initiating the cardiac cycle.

   - **Atrioventricular (AV) Node**: Located at the junction of the atria and ventricles. It delays the impulse to allow complete atrial contraction before ventricular contraction.

   - **Bundle of His**: Transmits impulses from the AV node to the ventricles.

   - **Purkinje Fibers**: Rapidly conduct the impulse throughout the ventricles, ensuring a coordinated contraction.

3. **Cardiac Cycle**

   - **Events**: Includes systole (contraction phase) and diastole (relaxation phase).

   - **Phases**:

     - **Atrial Systole**: Atria contract, pushing blood into the ventricles.

     - **Isovolumetric Contraction**: Ventricles contract with no volume change as all valves are closed.

     - **Ventricular Ejection**: Semilunar valves open, and blood is ejected into the aorta and pulmonary artery.

     - **Isovolumetric Relaxation**: Ventricles relax with no volume change as all valves are closed.

     - **Ventricular Filling**: AV valves open, and blood flows into the ventricles from the atria.

   - **Pressure and Volume Changes**: During the cardiac cycle, ventricular pressure increases during systole and decreases during diastole. Volume changes include end-diastolic volume (EDV) and end-systolic volume (ESV).

### Short Notes

1. **Heart Sounds**: 

   - **First Heart Sound (S1)**: Caused by the closure of AV valves (mitral and tricuspid) at the beginning of ventricular systole.

   - **Second Heart Sound (S2)**: Caused by the closure of semilunar valves (aortic and pulmonary) at the beginning of ventricular diastole.

2. **ECG in Lead II**: The electrocardiogram (ECG) records the electrical activity of the heart. In Lead II:

   - **P Wave**: Atrial depolarization.

   - **QRS Complex**: Ventricular depolarization.

   - **T Wave**: Ventricular repolarization.

3. **Baroreceptor Mechanism**: Baroreceptors in the carotid sinuses and aortic arch sense changes in blood pressure and relay information to the medulla oblongata, which adjusts heart rate and vessel diameter to maintain stable blood pressure.

4. **Poiseuille's Law**: Describes the flow of fluid through a cylindrical vessel. It states that flow is directly proportional to the fourth power of the vessel's radius and the pressure difference, and inversely proportional to the vessel's length and fluid viscosity.

5. **Coronary Circulation**: The blood supply to the heart muscle itself. It is unique due to its high oxygen demand, the presence of collateral vessels, and autoregulation to match blood flow with metabolic needs.

## Respiratory System

### Long Answer Questions

1. **Nervous Regulation of Respiration**

   - **Medullary Respiratory Centers**: The medulla oblongata contains the dorsal respiratory group (DRG) and ventral respiratory group (VRG). The DRG primarily controls inspiration, while the VRG controls both inspiration and expiration.

   - **Pontine Respiratory Centers**: The pons contains the pneumotaxic and apneustic centers, which modulate the rhythm and depth of breathing set by the medulla.

2. **Chemical Regulation of Respiration**

   - **Central Chemoreceptors**: Located in the medulla, they respond to changes in CO2 levels and pH in the cerebrospinal fluid.

   - **Peripheral Chemoreceptors**: Located in the carotid bodies and aortic bodies, they respond to changes in blood O2, CO2, and pH levels.

3. **Transport of Respiratory Gases**

   - **Oxygen Transport**: 

     - **Bound to Hemoglobin**: About 98.5% of O2 is transported bound to hemoglobin in red blood cells.

     - **Dissolved in Plasma**: About 1.5% of O2 is dissolved in the plasma.

   - **Carbon Dioxide Transport**: 

     - **Dissolved in Plasma**: About 7-10% of CO2 is dissolved in the plasma.

     - **Carbaminohemoglobin**: About 20% of CO2 binds to hemoglobin.

     - **Bicarbonate Ions**: About 70% of CO2 is transported as bicarbonate ions (HCO3-) formed by the reaction with water and carbonic anhydrase in red blood cells.

   - **Oxygen-Hemoglobin Dissociation Curve**: A sigmoidal curve that shows the relationship between PO2 and hemoglobin saturation. Factors such as pH, CO2, temperature, and 2,3-BPG can shift the curve.

### Short Notes

1. **Surfactant**: A substance produced by type II alveolar cells that reduces surface tension in the alveoli, preventing collapse and aiding in lung compliance. **Hyaline Membrane Disease**: A condition primarily seen in premature infants due to insufficient surfactant, leading to respiratory distress.

2. **Respiratory Membrane**: Composed of the alveolar epithelium, the capillary endothelium, and their fused basement membranes. It is the site of gas exchange between the alveoli and the blood.

3. **Hyaline Membrane Disease (Respiratory Distress Syndrome)**: A condition in premature infants caused by the lack of surfactant, leading to the collapse of alveoli, impaired gas exchange, and respiratory distress.

4. **Lung Compliance**: The measure of the lung's ability to expand and contract. It is influenced by the elasticity of lung tissue and the surface tension within the alveoli. High compliance indicates easy lung expansion, while low compliance indicates stiffness.

5. **Lung Volumes and Capacities**: 

   - **Tidal Volume (TV)**: The amount of air inhaled or exhaled during normal breathing.

   - **Vital Capacity (VC)**: The maximum amount of air that can be exhaled after a maximum inhalation.

   - **Residual Volume (RV)**: The amount of air remaining in the lungs after a maximal exhalation.

   - **Total Lung Capacity (TLC)**: The total volume of the lungs, including the residual volume.

6. **Oxygen-Hemoglobin Dissociation Curve**: Illustrates how readily hemoglobin acquires and releases oxygen molecules. The curve shifts to the right (indicating decreased affinity) in response to increased CO2, decreased pH, increased temperature, and increased 2,3-BPG.

7. **Bohr and Haldane Effects**: 

   - **Bohr Effect**: The influence of CO2 and pH on the oxygen binding affinity of hemoglobin. Increased CO2 and decreased pH (acidosis) reduce hemoglobin's affinity for O2, facilitating oxygen release to tissues.

   - **Haldane Effect**: The influence of oxygen on CO2 transport. Deoxygenation of hemoglobin increases its ability to carry CO2.

8. **Muscles of Respiration**: 

   - **Primary Muscles**: Diaphragm and intercostal muscles.

   - **Accessory Muscles**: Sternocleidomastoid, scalenes, and abdominal muscles, which are recruited during forced breathing.

Feel free to ask for more details or additional explanations on any specific topic!