Physiology
Integrated Physiology
Integrated physiology for MBBS and NEET-PG: responses to exercise, haemorrhage, altitude and temperature, plus fluid, glucose and acid-base regulation, mapped to NMC codes PY11.
MedNext Academy | 3 min read
Integrated Physiology
Integrated physiology for MBBS and NEET-PG: responses to exercise, haemorrhage, altitude and temperature, plus fluid, glucose and acid-base regulation, mapped to NMC codes PY11.
Integrated physiology brings the separate systems together to explain how the body responds to real situations. It covers the responses to exercise, haemorrhage, altitude, temperature change and stress, along with the coordinated control of fluid, glucose and acid-base balance.
High-yield: Integrated Physiology
- Integrated physiology looks at how organ systems work together to maintain homeostasis.
- In exercise, cardiac output rises and blood is redirected to the working muscles.
- During exercise ventilation increases to match the greater oxygen demand and carbon dioxide production.
- In haemorrhage the baroreceptor reflex and the renin-angiotensin system act to restore blood pressure.
- Acclimatisation to high altitude raises red cell mass and 2,3-DPG to improve oxygen delivery.
- The body defends its core temperature by sweating and vasodilatation in heat and by shivering and vasoconstriction in cold.
- The stress response involves the sympathetic nervous system and cortisol from the adrenal cortex.
- Fluid balance is controlled by antidiuretic hormone, aldosterone and thirst working together.
- Blood glucose is kept stable by the balance of insulin against glucagon, cortisol and adrenaline.
- Acid-base balance depends on the lungs, the kidneys and the buffer systems of the blood.
- The bicarbonate buffer is the most important extracellular buffer and is described by the Henderson-Hasselbalch relation.
- Respiratory compensation for a metabolic disturbance is rapid, while renal compensation is slow but powerful.
- In shock, poor tissue perfusion leads to a shift toward anaerobic metabolism and a lactic acidosis.
- The circadian rhythm is set by the suprachiasmatic nucleus and influences hormone release and sleep.
Coordinated responses
- **Exercise:** Cardiac output and ventilation rise; blood shifts to muscle.
- **Haemorrhage:** Baroreceptor reflex and renin-angiotensin restore blood pressure.
- **High altitude:** Higher red cell mass and 2,3-DPG improve oxygen delivery.
- **Acid-base:** Lungs give rapid compensation; kidneys give slow, powerful correction.
NMC competencies in this chapter
- **PY11.1:** Concept of integrated physiology and homeostasis
- **PY11.2:** Physiological response to exercise
- **PY11.4:** Physiology of high altitude and acclimatisation
- **PY11.6:** Physiology of temperature regulation
- **PY11.8:** Response to haemorrhage and shock
- **PY11.10:** The stress response
- **PY11.12:** Acid-base balance and its regulation
- **PY11.14:** Biological rhythms and the circadian clock
Frequently Asked Questions
How does the body respond to exercise?
During exercise the heart rate and stroke volume rise to increase cardiac output, blood is redirected to the working muscles, and ventilation increases to supply oxygen and clear carbon dioxide.
How does the body adapt to high altitude?
Over days to weeks the body increases ventilation, raises red cell mass through erythropoietin and increases 2,3-DPG, all of which improve oxygen delivery in the thin air.
How is blood pressure restored after bleeding?
The baroreceptor reflex raises heart rate and constricts vessels within seconds, and the renin-angiotensin-aldosterone system then conserves salt and water to restore blood volume over hours.
How does the body keep acid-base balance?
The blood buffers, chiefly the bicarbonate system, act at once, the lungs adjust carbon dioxide within minutes, and the kidneys handle bicarbonate and hydrogen ions over hours to days.
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