HOMEOSTASIS

I NYOMAN ADIPUTRA

• FK UNUD: ‘75 ; dr.• U HK: 1978-79Advanced Physiology.• IPH-UP: 1982-83 M.O.H.• OUMS, Okayama 1983 (industrial hygiene)C.O.H.• FPS UNAIR: 1988/9-92Doktor• Sp1: 1990 PFK• Guru Besar: 1- 02 – 1993 Prof.• NIWL, Stockholm, 2002/04 Dipl.OSH & D • LCU, London 1997; MLU, London, 2002.• PB IAIFI: 2009 Sp1.Erg.

HOMEOSTASIS

Definition: i.e. a state of keeping the internal environment constant within physiological limits.

What is the “internal environment”? - 60% of body is made of body fluids

“Internal environment” is the;

Components of the body fluids

CAPILLARY EXCHANGE

Homeostasis occurs at capillary level. Capillaries are the smallest blood vessel ~ one cell thick Substances (e.g. nutrients, O2,CO2 and cellular wastes) move down

their concentration gradient across capillary.

STRESS AND HOMEOSTASIS Stress – is any stimuli (external and internal) disturbing homeostasis

Examples of internal stresses - blood glucose, and acidity in ECF

Examples of external stresses - heat, cold, lack of oxygen

There are variations of stress from mild stress to extreme stress.

Examples of mild stress - thirst and hunger

Examples of extreme tress - poisoning, severe infection

For mild stress, cells respond quickly to restore imbalance

For extreme stress, cells may restore incompletely the imbalance and can result in chronic illness or even death.

The body has many homeostatic devices to oppose the stimuli of stress and restore internal environment

STRESS and HOMEOSTASIS

ALLOSTASIS

• A PROCESS WHERE THE HOMEOSTASIS IS CHANGED & SET UP INTO THE NEW VALUE LEVEL.

HOMEOSTASIS

HOMEOSTASIS

• HOMEOSTASIS

REGULATION OF HOMEOSTASIS The Nervous system and Endocrine system work together or

independently to regulate homeostasis

1) NERVOUS SYSTEM

- uses nerve impulses to respond to stresses in the body

- response is rapid compare to endocrinal system

E.g. Active muscle contraction – produces CO2 and O2 in blood. Nerve cells detects changes in blood gases sends impulses to brain brain send impulses to heart to heart rate brain also sends impulses to respiratory centre in brain to breathing rate blood gases are quickly restored back to normal.

REGULATION OF HOMEOSTASIS

2) ENDOCRINAL SYSTEM– Uses hormones to responds to stresses and to maintain

homeostasis– Response is slower than nervous system and also is more fine

tuning.

E.g. Active muscle contraction produces CO2 and O2 in blood CO2 causes the release of epinephrine into blood epinephrine causes in heart rate delivery to and removal of CO2 in lungs .

CONTROL MECHANISM FOR HOMEOSTASIS

The control mechanism for homeostasis is a feedback system.

- FEEDBACK SYSTEM has 3 parts ;

1) CONTROL CENTER

2) RECEPTOR

3) EFFECTOR

CONTROL MECHANISM FOR HOMEOSTASIS

1) CONTROL CENTER

- mainly the brain and other parts of the central nervous system- sets the values at which the controlled condition (E.g. body temperature) is to be maintained.

2) RECEPTOR - monitors changes in the controlled condition and sends information to control center.(E.g. continuously sends body temperature data to the body temperature control center in the brain)

3) EFFECTORS - receives information from controlled center and produces response to correct stimuli.

CONTROL MECHANISM FOR HOMEOSTASIS

TWO TYPES OF FEEDBACK LOOPS

1) NEGATIVE FEEDBACK LOOP

2) POSITIVE FEEDBACK LOOP

TWO TYPES OF FEEDBACK LOOPS 1)NEGATIVE FEEDBACK LOOP

- the response reverses original stimuli by inhibiting it.

- we especially see in conditions that require frequent

monitoring and make adjustment within physiological limits.

Example:

1. Body temperature and blood glucose level is regulated by negative feedback system.

2. Release of thyroxine (T3 and T4 hormones) from thyroid gland.

2) POSITIVE FEEDBACK LOOP- the response enhances the original stimulus- we see in conditions that does not require fine-tuning- usually switched off by mechanisms outside the system- can be destructive and result in various disorder but

some are normal and beneficial.

Example:i) Blood clotting. The original signal is amplified until blood

clot forms and bleeding is under control. Then othersubstances help turn off the clotting response.

ii) At birth. Positive feedback loop results in strengthening of labor contractions until the baby is finally delivered.

iii) Immune response. The positive feedback loop causes the body to amplify the signal and response to contain and quickly remove the pathogen (disease causing agent) from the body.

E.g. CLOTTING CASCADE

THERE IS A DUALISM IN THE BODY

platelets Anti-platelets

vasodilator V.Constrictor

Brochodilator Br.constrictor

Heat product. Heat-loss

Oxidant Antioxidant

Antigen Anti body

Aging Anti-aging

DISEASE :HOMEOSTASIS and IMBALANCE Body processes remains within physiological limits body

cells function well homeostasis is maintained body is healthy.

But when body processes ( 1 or >1) loose their ability to contribute to homeostasis. The outcomes would result in;

- (if moderate) diseases results

- (if severe) death results LOCAL DISEASES - disease affecting limited part/ region of the body. SYSTEMIC DISEASE- disease affecting entire body. SYMPTOMS - Subjective changes (complains) in the body function

that a patient complains about, and is not apparent to an observer.

(e.g. pain complaint by patient) SIGNS - Objective changes that a clinician can observe and measure.

- SIGNS can be ;

(ANATOMICAL changes) – Swelling, rash

(PHYSIOLOGICAL changes) – Raised blood pressure and raised body temperature