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