Human Physiology: Urine Formation, Endocrine & Nervous Systems
Physiology of Urine Formation
Physiology of urine formation: Kidneys form urine by filtration and secretion of waste materials from the blood. In addition, selective reabsorption by tubular cells contributes to the maintenance of homeostasis and the regulatory activities of the kidneys.
Formation of Urine
The urinary system: The nephrons of the kidney perform this function. Primarily, three processes are involved in the formation of urine: glomerular filtration, tubular reabsorption, and tubular secretion.
Read MoreKey Functions in Human Biology
Digestive and Metabolic Functions
1. Saliva and Stomach Acid
- Saliva: Lubricates food for swallowing, moistens the mouth, and contains the enzyme Salivary Amylase (Ptyalin) which begins the digestion of carbohydrates (starches).
- HCl (Hydrochloric Acid): Maintains an acidic pH (1.5–3.5) in the stomach to activate pepsinogen into pepsin (for protein digestion) and kills ingested bacteria/microbes.
2. Basal Metabolic Rate (BMR)
- BMR: The minimum amount of energy (calories) required by the body to maintain
Respiration, Photosynthesis, Carbon Allotropes and Essential Elements
1. Respiration and Photosynthesis
Ans. Respiration is the process in which organisms break down glucose with oxygen to release energy (ATP) for cellular functions, producing carbon dioxide and water as byproducts. Photosynthesis is the opposite process, carried out by plants and algae, which uses light energy, water, and carbon dioxide to create glucose (a sugar for energy) and oxygen. These processes are interconnected: the glucose and oxygen from photosynthesis provide the fuel for respiration,
Mechanisms of Biological Gas Exchange
Gas Exchange Fundamentals
Gas exchange is the process where an organism takes in oxygen and eliminates carbon dioxide. Oxygen is essential for respiration and must reach every cell. Carbon dioxide is a waste product of respiration that must be removed from the body. Gas exchange occurs via diffusion across a gas exchange surface. Oxygen diffuses from air or water, either into the blood for transport to the cells or directly into the cells. Carbon dioxide diffuses from the cells or the blood back
Read MoreComparative Adaptations for Respiratory Gas Exchange
The Process of Gas Exchange
Gas exchange is the vital physiological process by which oxygen ($ ext{O}_2$) from the environment is taken into the body and carbon dioxide ($ ext{CO}_2$), a waste product of cellular respiration, is removed. In animals, this process typically occurs across specialized respiratory surfaces, such as:
- Lungs (mammals, birds, reptiles)
- Gills (fish, some amphibians)
- Skin (some amphibians, invertebrates)
Oxygen diffuses across thin, moist membranes into the bloodstream or directly
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