Unit 5 - Human Physiology

 1. Breathing and Respiration

Breathing refers to the physical process of inhaling and exhaling air, while respiration involves the biochemical breakdown of glucose to release energy.

Respiratory System in Humans

• Organs: Nose, pharynx, larynx, trachea, bronchi, lungs.
• Mechanism of Breathing:
• Inspiration: Diaphragm contracts, thoracic cavity expands, air enters lungs.
• Expiration: Diaphragm relaxes, thoracic cavity reduces, air exits lungs.
• Exchange of Gases: Occurs in alveoli via diffusion; oxygen enters blood, carbon dioxide exits.
• Transport of Gases:
• Oxygen binds to hemoglobin in RBCs to form oxyhemoglobin.
• CO₂ is transported as bicarbonate ions (70%), bound to hemoglobin (23%), and dissolved in plasma (7%).

Respiratory Volumes

• Tidal Volume (TV): Air inhaled/exhaled during normal breathing (~500 mL).
• Inspiratory Reserve Volume (IRV): Additional air inhaled (~3000 mL).
• Expiratory Reserve Volume (ERV): Additional air exhaled (~1000 mL).
• Residual Volume (RV): Air remaining after forceful exhalation (~1200 mL).

Disorders Related to Respiration

1. Asthma: Chronic inflammation causing airway narrowing.
2. Emphysema: Damage to alveoli reduces gas exchange efficiency.
3. Occupational Respiratory Disorders: Caused by exposure to pollutants (e.g., coal dust).

2. Body Fluids and Circulation

The circulatory system ensures the transport of nutrients, gases, hormones, and waste products.

Composition of Blood

1. Plasma (55%): Water, proteins (albumin, globulin), nutrients, hormones.
2. Formed Elements (45%): RBCs (oxygen transport), WBCs (immunity), platelets (clotting).

Blood Groups

• ABO system based on antigens on RBCs; Rh factor determines positive/negative blood type.

Coagulation of Blood

• Platelets release thromboplastin → Prothrombin converts to thrombin → Fibrinogen forms fibrin → Clot forms.

Human Circulatory System

1. Heart Structure:
• Four chambers: Right atrium, right ventricle, left atrium, left ventricle.
• Valves prevent backflow: Tricuspid valve (right side), bicuspid valve (left side), semilunar valves.
2. Blood Vessels:
• Arteries carry oxygenated blood; veins carry deoxygenated blood; capillaries facilitate exchange.
3. Cardiac Cycle:
• Systole (contraction) and diastole (relaxation) regulate blood flow.
4. ECG:
• P wave: Atrial depolarization.
• QRS complex: Ventricular depolarization.
• T wave: Ventricular repolarization.

Disorders of Circulatory System

1. Hypertension (high BP).
2. Coronary Artery Disease (blockage in coronary arteries).
3. Angina Pectoris (chest pain due to reduced blood flow).
4. Heart Failure (inadequate pumping by heart).

3. Excretory Products and Their Elimination

Modes of Excretion

1. Ammonotelism: Excretion of ammonia (e.g., fish).
2. Ureotelism: Excretion of urea (e.g., humans).
3. Uricotelism: Excretion of uric acid (e.g., birds).

Human Excretory System

• Organs include kidneys, ureters, urinary bladder, urethra.
• Kidney structure:
• Cortex and medulla contain nephrons.
• Nephron filters blood and forms urine.

Urine Formation

1. Filtration in Bowman’s capsule.
2. Reabsorption in proximal tubule.
3. Secretion in distal tubule.

Regulation of Kidney Function

1. Renin-Angiotensin System regulates BP and filtration rate.
2. Atrial Natriuretic Factor reduces BP by inhibiting renin.
3. ADH increases water reabsorption; deficiency causes diabetes insipidus.

Disorders Related to Excretion

1. Uraemia: Accumulation of urea in blood.
2. Renal Failure: Loss of kidney function.
3. Renal Calculi: Kidney stones.
4. Nephritis: Inflammation of kidneys.

4. Locomotion and Movement

Types of Movement

1. Ciliary movement (e.g., respiratory tract).
2. Flagellar movement (e.g., sperm cells).
3. Muscular movement.

Skeletal Muscle

• Contractile proteins:
• Actin forms thin filaments; myosin forms thick filaments.
• Muscle contraction:
• Sliding filament theory explains interaction between actin and myosin using ATP.

Skeletal System

• Functions include support, protection, movement.
• Joints allow flexibility:
• Ball-and-socket joint (shoulder).
• Hinge joint (knee).

Disorders Related to Muscular and Skeletal Systems

1. Myasthenia Gravis: Autoimmune disorder causing muscle weakness.
2. Tetany: Muscle spasms due to low calcium levels.
3. Muscular Dystrophy: Genetic disorder causing muscle degeneration.
4. Arthritis: Inflammation of joints.
5. Osteoporosis: Reduced bone density due to calcium deficiency.

5. Neural Control and Coordination

Neuron Structure

• Cell body contains nucleus and organelles.
• Dendrites receive signals; axons transmit signals.

Nervous System in Humans

1. Central Nervous System:
• Brain and spinal cord control voluntary actions.
2. Peripheral Nervous System:
• Nerves connect CNS to body parts.
3. Visceral Nervous System:
• Controls involuntary actions like digestion.

Generation and Conduction of Nerve Impulse

1. Resting potential maintained by Na⁺/K⁺ pump.
2. Action potential generated by influx of Na⁺ ions.
3. Impulse travels along axon; neurotransmitters relay signal across synapse.

6. Chemical Coordination and Regulation

Endocrine Glands and Hormones

1. Hypothalamus regulates pituitary gland activity.
2. Pituitary secretes growth hormone (GH), thyroid-stimulating hormone (TSH).
3. Thyroid produces thyroxine (T₄) for metabolism regulation.
4. Adrenal glands secrete adrenaline for stress response.
5. Pancreas secretes insulin for glucose regulation.

Mechanism of Hormone Action

Hormones bind to specific receptors on target cells to initiate cellular responses.

Disorders Related to Endocrine System

1. Dwarfism (GH deficiency).
2. Acromegaly (GH excess).
3. Cretinism (thyroxine deficiency in children).
4. Goiter (iodine deficiency).
5. Diabetes Mellitus (insulin deficiency).
6. Addison’s Disease (adrenal cortex insufficiency).

Key Diagrams

1. Structure of human heart showing chambers and valves.
2. Nephron structure explaining filtration process.
3. Sliding filament model for muscle contraction.

Summary

Human physiology integrates multiple systems working together to maintain homeostasis:

1. Respiratory system ensures oxygen supply and CO₂ removal.
2. Circulatory system transports nutrients and gases efficiently while regulating heart activity.
3. Excretory system eliminates waste products while maintaining water balance.
4. Locomotion involves coordinated movements supported by muscles and bones.
5. Nervous system controls voluntary/involuntary actions via neurons and impulses.
6. Endocrine system regulates metabolic activities through hormones acting as messengers.