2ND YEAR BIOLOGY CHAPTER 15 HOMEOSTASIS INTRODUCTION

1. PUNJAB GROUP OF COLLEGE OF BWP

2. Prof. Rabia Ramzan
Lecture 1
Chapter 15
Homeostasis

3. Discovery
• The concept of homeostasis was first given by
French Physiologist Claude Bernard in 1865.
• The word Homeostasis was coined by Walter
Bradford Cannon.

4. Types of Environment
External environment
Internal environment

5. 1. External Environment 2. Internal Environment

6. External Environment Internal Environment
Definition
Environment that surround organism
Factor of External environment
Water
Light
Temperature
Air
Fluctuate continuously
Example temperature
in winter
summer
day
night
Definition
Environment inside organism
Factor most susceptible
Solute
Water
temperature
Organism maintain enternal environment
Keep at narrow range

7. HOMEOSTASIS:
• DEFINITION: The Protection of internal
environment form the harms of fluctuations
in external environment

8. Most susceptible component of enternal environment
in organisms
1. Solute
2. Water
3. temperature

9. 1)OSMOREGULATION:
• DEFINITION: The maintenance of water and
salts in the body is called Thermoregulation.
• The mechanism regulates the solute between
the internal environment and external
environment.

10. 2)THERMOREGULATION:
• The maintenance of internal body temperature with
in tolerable range is called Thermoregulation.

11. EXCRETION:
• The mechanism of elimination of nitrogenous
wastes from the body is called excretion.
• The adaptation of this mechanism also depends
on the availability of water

12. Control at organism level
Extracellular Environment Intracellular Environment
Environment with in cellEnvironment surround cell
Example
Vascular and interstitial fluid

13. SIGNIFICANCE OF HOMEOSTASIS:
• The external Environment always changes but the
Organism make adjustment with various control
system to keep its internal fluctuations with in
narrow range.

14. SIGNIFICANCE OF HOMEOSTASIS:
• The homeostasis protect internal environment
from the harms of fluctuations in external
Environment.

15. Controlling system

16. NATURE OF CONTROLLING SYSTEM:
• Control systems are used for different homeostatic
functions.
• TYPES OF CONTROL SYSTEM:
PHYSICAL CONTROL SYSTEM.
LIVING CONTROL SYSTEM.
Living control system work exactly on
mechanism of Physical control system.

17. PHYSICAL CONTROL SYSTEM:
• TEMPERATURE CONTROL SYSTEM:

18. PHYSICAL CONTROL SYSTEM:
• SWITCHING ON:
• Cooling System incase of increase of temperature
from set point.
• KEY POINTS:
• SENSOR RECEPTOR
• THERMOSTAT CONTROL CENTRE
• Compressor EFFECTOR

21. LIVING CONTROL SYSTEM: