Animal physiology (IB)

Introduction to Animal Physiology

Animal physiology is the study of the functions and processes of living animals. It explores how organs, tissues, cells, and systems interact to sustain life. Animal physiology is essential for understanding the mechanisms of survival, growth, reproduction, and adaptation.

Key Concepts:

• Adaptation: The ability of animals to adjust to their environments over time.

• Homeostasis: The maintenance of a stable internal environment despite external changes.

Homeostasis

Homeostasis is crucial for maintaining the internal environment of the body within certain limits that allow cells to function efficiently. It involves feedback mechanisms that regulate various physiological parameters such as body temperature, pH, and water balance.

• Negative Feedback: A response that counteracts a change in the system. For example, the regulation of body temperature: if the body temperature rises, sweating occurs to cool the body down.

• Positive Feedback: Amplifies a change. For example, during childbirth, the release of oxytocin intensifies uterine contractions, leading to delivery.

• Set Point: The ideal value of a physiological parameter (e.g., body temperature of 37°C).

Example of Homeostasis:

• Blood Glucose Regulation: After eating, blood glucose levels rise. The pancreas releases insulin to lower glucose levels, restoring homeostasis.

Key Physiological Systems

Animal physiology focuses on various systems that work together to maintain homeostasis and ensure proper functioning.

Circulatory System

• Function: Delivers oxygen, nutrients, hormones, and removes waste products. It also plays a role in immune responses and temperature regulation.

• Circulatory Pathway:

  • Pulmonary Circulation: Blood flows from the heart to the lungs and back, where gas exchange occurs.

  • Systemic Circulation: Blood is pumped from the heart to the body and back to deliver oxygen and nutrients.

Blood Components:

• Plasma: Carries nutrients, hormones, and waste products.

• Red Blood Cells: Contain hemoglobin, which binds to oxygen.

• White Blood Cells: Part of the immune system, helping to fight infections.

• Platelets: Help in blood clotting.

Respiratory System

• Function: Gas exchange – oxygen is absorbed into the bloodstream and carbon dioxide is expelled.

• Mechanisms:

  • Ventilation: The movement of air into and out of the lungs.

  • Diffusion: Oxygen diffuses from the alveoli (air sacs in the lungs) into the blood, and carbon dioxide diffuses from the blood into the alveoli to be exhaled.

Adaptations in Different Environments:

• Aquatic animals have gills that extract oxygen from water.

• Terrestrial animals have lungs that extract oxygen from air.

• Insects use a system of tubes called tracheae to deliver oxygen directly to tissues.

Digestive System

• Function: Breaks down food into absorbable nutrients and removes undigested waste.

• Digestive Process:

  • Mechanical Digestion: Physical breakdown of food (e.g., chewing).

  • Chemical Digestion: Enzymatic breakdown of food into smaller molecules (e.g., proteins into amino acids).

• Absorption: Nutrients are absorbed in the small intestine, while water and salts are absorbed in the large intestine.

Excretory System

• Function: Removes metabolic waste products (e.g., urea) and helps maintain water and electrolyte balance.

• Kidneys filter blood, remove waste, and maintain water balance. The nephron is the functional unit of the kidney.

  • Ultrafiltration: Blood pressure forces water and solutes into the nephron.

  • Reabsorption: Useful substances like glucose and water are reabsorbed into the blood.

  • Secretion: Waste products are secreted into the urine.

Musculoskeletal System

• Function: Provides structure, supports the body, and facilitates movement.

• Muscle Types:

  • Skeletal Muscle: Voluntary muscle that moves bones.

  • Smooth Muscle: Involuntary muscle found in organs (e.g., intestines).

  • Cardiac Muscle: Involuntary muscle that makes up the heart.

• Bone Structure: Bones are made of collagen and calcium salts. They provide protection and act as levers for movement.

Nervous System

• Function: Coordinates body activities, processes sensory information, and sends signals to muscles and organs.

• Components:

  • Central Nervous System (CNS): Brain and spinal cord, which process information.

  • Peripheral Nervous System (PNS): Nerves that connect the CNS to the rest of the body.

  • Neurotransmitters: Chemicals like dopamine, serotonin, and acetylcholine that allow communication between neurons.

Neural Control:

• Action Potentials: Electrical impulses that travel along neurons, allowing for rapid communication.

• Synapse: The junction between two neurons, where neurotransmitters are released.

Endocrine System

• Function: Regulates growth, metabolism, and reproduction via hormone secretion.

• Glands and Hormones:

  • Pituitary Gland: Secretes growth hormone and controls other endocrine glands.

  • Thyroid Gland: Secretes thyroid hormones that regulate metabolism.

  • Adrenal Glands: Secrete adrenaline and cortisol, which are involved in stress responses.

Reproductive System

• Function: Ensures species survival by producing offspring.

• Male System:

  • Testes: Produce sperm and testosterone.

  • Penis: Delivers sperm into the female reproductive tract.

• Female System:

  • Ovaries: Produce eggs and estrogen.

  • Uterus: Where the fertilized egg implants and develops.

Fertilization: The fusion of sperm and egg to form a zygote, which undergoes development.

Neural and Hormonal Control

Both the nervous system and endocrine system work together to regulate physiological processes:

• Nervous System: Provides rapid, short-term responses to stimuli. Examples: Reflex actions (e.g., pulling hand away from a hot surface).

• Endocrine System: Slower, but longer-lasting responses through hormones. Example: Regulation of blood sugar by insulin and glucagon.

Circulatory and Respiratory Adaptations in Different Environments

Animals have evolved various adaptations to thrive in different environments:

• High Altitude: Animals like llamas and mountain goats have more red blood cells and hemoglobin to carry oxygen.

• Aquatic Environments: Fish have specialized gills for extracting oxygen from water. Mammals like whales have adaptations to hold their breath for long periods during diving.

Adaptations for Gas Exchange:

• Lungs in terrestrial animals have a large surface area (alveoli) for gas exchange.

• Gills in fish have thin membranes for efficient oxygen absorption.

• Tracheal systems in insects deliver oxygen directly to cells without the need for a circulatory system.

Thermoregulation

Thermoregulation is the process by which animals maintain their body temperature within a narrow range.

• Endotherms (Warm-blooded): Animals that regulate their body temperature internally through metabolic processes (e.g., mammals, birds).

• Ectotherms (Cold-blooded): Animals whose body temperature is determined by the external environment (e.g., reptiles, amphibians).

• Adaptations for Thermoregulation:

  • Behavioral: Seeking shade or sunlight.

  • Physiological: Sweating, shivering, blood flow adjustments.

Immune System

The immune system defends the body against infections and diseases. It has two main components:

• Innate Immunity: Non-specific defenses like skin, mucus, and phagocytes (e.g., macrophages).

• Adaptive Immunity: Specific responses to pathogens, involving T cells and B cells. B cells produce antibodies to neutralize pathogens.

Inflammation: A response to infection or injury involving increased blood flow, immune cell activation, and tissue repair.

Energy and Metabolism

Metabolism refers to the biochemical processes that convert food into energy for bodily functions.

• Catabolism: The breakdown of complex molecules (e.g., glucose) to release energy.

• Anabolism: The synthesis of complex molecules (e.g., proteins) from simpler ones.

Cellular Respiration:

• Aerobic Respiration: Oxygen is used to break down glucose, producing a large amount of ATP (energy).

• Anaerobic Respiration: In the absence of oxygen, less ATP is produced, and lactic acid or ethanol is formed.

Adaptations to Different Diets

• Herbivores: Adapted to digest plant material, often with specialized teeth (e.g., flat molars) and a large cecum for fermentation of cellulose.

• Carnivores: Have sharp teeth for tearing meat and a shorter digestive tract.

• Omnivores: Have a variety of teeth and digestive enzymes to break down both plant and animal matter.

Animal physiology is a complex and fascinating field that explores how organisms maintain homeostasis, adapt to their environment, and perform essential life functions. From the regulation of body temperature to the coordination of the circulatory and respiratory systems, every aspect of animal physiology is interconnected, ensuring the survival of the species.