HOMEOSTASIS:MAINTAINING AN INTERNAL BALANCESBI 4U, December 12th, 2012

Maintaining an Internal Balance Ray Zahab vs. Fennec Fox Fennec fox ears allow for efficient

hearing and act as radiator

Maintaining and Internal Balance Homeostasis: the physiological state of

the body in which the internal physical and chemical conditions are maintained within an acceptable or tolerable range that is suitable for essential biological processes

Dynamic state

Maintaining an Internal Balance Body has several conditions that must be

monitored. Such as:-internal temperature-hormone levels-pH-flow and concentration of glucose and

other solutes *some tolerable ranges are narrow, while

others are more broad*

The Internal Environment Purpose of homeostasis: to maintain internal physical

and chemical conditions that are appropriate for the cells to function properly

Internal environment: the extracellular fluid, which consists of the fluid that surrounds the cells and tissues in the body and the plasma portion of the blood

Focus on fluid outside of the cells

Organ Systems Involved in Homeostasis

Nervous System Endocrine System Muscular System Integumentary System Excretory System Reproductive System

Organ Systems Involved in Homeostasis

All of the organ systems are coordinated to carry out the tasks necessary for the survival of the organism. No matter how simple or complex the animal, these functions include:

1. Taking in nutrients and other required chemicals, processing and excreting

2. Synthesizing proteins, fats and carbs3. Sensing and responding to changes in

external environment4. Protecting body 5. Reproducing, protecting and feeding offspring

Organ Systems Involved in Homeostasis

Homeostatic Mechanisms: a system that monitors internal and external conditions and changes bodily functions to maintain homeostasis

Ex: shivering in response to cold weather

Negative Feedback Mechanisms

Primary mechanism of homeostasis Negative feedback: the response of a system that acts to maintain

equilibrium by compensating for any changes made to the system 3 components: sensor, integrator and effector

Negative Feedback Mechanisms Sensor: consists of tissues or organs

that detect any change in external or internal factors

Info transmitted to integrator acts as a processing or control centre. Compares environmental conditions with the optimal function conditions called set points

Integrator activates the effector the element of a feedback system that acts to return the system to its optimal state

Negative Feedback Mechanisms

Antagonistic effects response opposite to change Ex: thermostat1. Sensor measures temperature2. Integrator compares the measures temperature to

set point3. Integrator activates electrical effector (furnace or

air conditioner)4. Temperature returned to normal state

Negative Feedback in Animals Ex: humans1. Neurons in preoptic region of

hypothalamus receive info from thermoreceptors

2. Hypothalamus compares info to set point

3. Hypothalamus activates effectors that induce vasoconstriction in skin. Less thermal energy lost. Body temperature increases

Positive Feedback Mechanisms Positive Feedback: the response of a

system that acts to increase the effect of any changes made to the system

Do not result in homeostasis Operate when a continuous increase in

some internal variable is required (ex: fight or flight)

Ex: childbirth contractions release of oxytocin