HUMAN PHYSIOLOGY

1. HUMAN PHYSIOLOGY LECTURES 1 & 2

2. CENTRAL THEMES IN PHYSIOLOGY

3. CENTRAL THEMES IN PHYSIOLOGY • Structure – Function relationship • Adaptations, acclimatization and acclimation • Homeostasis • Conformity and regulation • Feedback control systems

4. STRUCTURE – FUNCTION RELATIONSHIP Function is based on structure at all levels of organization

5. LEVELS OF ORGANIZATION IN FUNCTION Population Organism Community Ecosystem Organ-systems Organs Tissues Cells Molecules Atoms and subatomic particles

6. Hierarchy of life

7. The figure is showing one movement of frog leg from organism to molecular level. • This is same in human body muscles.

8. Example of frog – this is same for human muscles, replace insect with a protein food • Frog catches a passing fly by a leap (skeletal muscle) • After eating fly, frog’s stomach mixes and massages the contents (smooth muscles) • The nutrients absorbed into the blood are propelled by the beating of heart to the body (cardiac muscle)

9. SOME EXAMPLES OF STRUCTURE - FUNCTION RELATIONSHIP • Movement (leap) of a frog from organism to molecular level • Reflex arc • Nutrition and digestion

10. ADAPTATIONS, ACCLIMATIZATION AND ACCLIMATION • Adaptation is a physiological, biochemical or anatomic change that typically occurs in a gradual manner over generation. Generally it is not reversible. Physiology of an animal is usually well matched with the environment. Evolution by natural selection is the explanation of the process called adaptation.

11. Acclimatization is a physiological, biochemical or anatomic change within and individual animal during its life that results from the animals chronic exposure in its native habitat to new, naturally occurring environmental conditions. • Acclimation is same process but when the same changes are induced experimentally in laboratory or in wild habitat by researcher.

12. Adaptation ----contd • Adaptation is a change in genotype that result in a structural or functional change in phenotype (expression of genotype). • Migration of a bear from low-lying valley to high mountain result in increased ventilation in beginning but later on returned to normal as other physiological mechanisms takes its place, for example, RBC’s increase in number to increase oxygen-carrying capacity of blood. This is called Acclimatization.

13. Adaptations --- contd • If the conditions of mountain (hypobaric) are developed in laboratory for any animal, same response could be seen, but it is called Acclimation. • Bar-headed goose fly up to the peaks of Himalayas, which if other animals do, they die. This is adaptation of the goose selected via process of natural selection to survive in this extreme environment.

14. Adaptation --- cotnd • Adaptation was thought to be optimal but now it is realized that it is not “optimal” all the time but good enough to ensure survival of the animal in its environment. For example, temperature range of 1 -2 °C is adapted, it could be more precise but may not selected by natural selection to ensure survival.

15. Adaptation --- contd • It could be difficult to know that whether a physiological characteristic is of adaptive value or not. A physiological process is adaptive if it is present at high frequency in a population. The reason is that it results in a higher probability of survival and reproduction.

16. Adaptation --- contd Llama • How to prove certain character is adaptive? Comparative approach tells us how is it possible. • Llama and camel’ blood have same affinity for oxygen (which is very high). Hilly & cold area Camel Low lands

17. Adaptation --- contd • The reason for all this is that both physiological and anatomic adaptations are genetically based, i.e. these are in germ line. And these pass from one generation to the next. Animals inherit information in the form of DNA. Mutation (Spontaneous alteration) occur in the nucleotide sequence of DNA that cause alteration in RNA and then proteins. Mutations that enhance animals’ survival and hence chances of its reproduction are retained by natural selection and their frequency in population increases over time. This result in Adaptation.

18. Adaptation --- contd • Genetic material (DNA) is passed from parents to offspring's • Germ line is derived from the parents germ line, to continue the germ line DNA. • Evolution is centered on the survival of DNA, since information it have defines a species. • Failure to reproduce its DNA leads to extinction of a species.

19. Adaptation --- contd • From biological point of view, animal life’s main purpose is to reproduce and propagate its DNA. All physiological processes, behaviours and anatomic structures are ultimately subservient to continuation of germ line. • Adaptation is to cope with constraints and demands of environment to survive.

21. HOMEOSTASIS Homeostasis is defined as “consistency of internal environment”. This is a concept first recognized by a French pioneer of modern Physiology, Claude Bernard. Animals live in quite hostile environments Aquatic animals face more dilute (fresh water) or more salty (sea water) than their body. Terrestrial animals face too hot or too cold temperature Aerial mode of life have resistance to flight etc

22. HOMEOSTASIS -- contd • Also most environments have fluctuations, i.e. changes over time and in seasonal changes. • To survive animals have to cope with these changes. • Homeostasis is the mechanism for this. • Various physiological processes and anatomic structures are adapted to maintain homeostasis.

23. HOMEOSTASIS -- contd • For example, • pH in blood (around 7) • Temperature of the body (37°C) • Search for examples of homeostasis

24. Conformity and Regulation • Conformity: Changing internal conditions according to change in external environment. E.g., fishes change body temperature if water temp. varies • Regulation: maintenance of internal environment by indigenous mechanisms, like temperature maintenance in human body.

25. Conformity and Regulation • Organisms demonstrates conformity are called conformers. E.g fishes • Organisms demonstrates regulation are called regulators. E.g. humans

26. Feedback Mechanisms • Systems in the body of regulators that: • Records any environmental changes – both in internal and external environments of the body and send to another controlling system (called sensor). • The controlling system analyzes the information and send information to a response system which upregulates or downregulates the function of concerned part of the body or level of any compound in the body or else.

27. Feedback Types • Negative feedback: When a function / production is reduced or stopped. (Example: level of a hormone after functioning is reduced due to negative feedback) • Positive feedback: When a function / production is upregulated. (Example: during child birth, oxytocin level increases in mother’s body to induce muscular contraction, its level increases more and more due to positive feedback)