B12 - Homeostasis In Action Flashcards
What is homeostasis?
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
Why is homeostasis important?
Homeostasis is important as cells and organs can become damaged if the internal environment changes too much. This is because enzymes cannot work properly.
Which part of the brain controls body temperature?
The hypothalamus is a part of the brain that monitors blood temperature.
Other than the brain, how else is body temperature controlled?
The skin has receptors that monitor the external temperature. Nerves carry messages from these to the brain.
Describe some changes that take place in/on the body it body temperature is too low
• Shivering - uses energy
• Less sweating
• Increased respiration- releasing energy from food
• Vasoconstriction (narrowing) of blood vessels near surface of skin
• Hairs stand upright to trap air (insulating)
Describe some changes that take place in/on the body if body temperature is too high
• Sweating (water evaporates from skin surface taking heat away)
• Vasodilation (widening) of blood vessels near surface of skin
• Hairs lie flat
What is your understanding of the term ‘negative feedback’.
Negative feedback means that whenever a change occurs in a system, this automatically causes a corrective mechanism to start, which reverses the original change and brings the system back towards the set point (i.e. ‘normal’).
Describe the ways that water is lost from the body.
• Water leaves the body via the lungs during exhalation (breathing out)
• Water, ions and urea are lost from the skin in sweat.
List the 4 main waste products that are released from the body.
• Water
• Urea
• Ions
• Carbon dioxide
From which organ is there CONTROLLED loss of water?
Controlled loss of excess water, ions and urea is controlled by the kidneys when they filter the blood to produce urine.
What is deamination?
Deamination is the process of breaking down excess amino acids (from proteins).
Using a brief flow chart, describe the process of deamination
Protein -> amino acids -> ammonia (toxic) -> Urea (excreted in urine & sweat)
Where does deamination take place?
The liver
What are the 3 main functions of the kidneys?
- Filters the blood (this is called ultrafiltration).
- Reabsorb water (and other useful substances e.g. glucose, some salts, water) back into the blood stream. This is called selective reabsorption.
- Excrete urea, water, and salts (in urine)
What are the functional units of the kidney where filtration and selective reabsorption takes place called?
Nephrons
Describe the process of ultrafiltration.
• Blood enters the kidneys via the renal artery.
• Blood is filtered under very high pressure.
• Large plasma proteins and blood cells are too large to pass through the filter.
• The filtered blood is now called filtrate.
• This is occurs in the nephron of the kidney
Describe the process of ‘selective reabsorption’
• Useful substances (that the body doesn’t want to lose) are selectively reabsorbed by the nephron back into the bloodstream.
• E.g. All of the glucose, amino acids, some ions, some water are reabsorbed.
• The rest of the filtrate passes through the rest of the nephron.
Describe the process of urine formation and excretion.
• Urine is formed with the substances that were not reabsorbed.
• Urine is a solution of excess water, salts and urea.
• Urine is collected in the collecting duct.
It passes through the ureter to the bladder.
What does ADH stand for and what is it’s function?
Anti-diuretic hormone (ADH) is a hormone involved in the control of the loss of water as urine.
Which part of the brain releases ADH?
The pituitary gland
In what situation is ADH released?
It is released into the bloodstream by the pituitary gland when receptors in the brain detect that the blood is too concentrated.
Where does ADH travel to once released and what effect does it have?
ADH acts on the walls of the kidney tubules making them more permeable, therefore more water is reabsorbed back into the blood from the kidney tubules.
If the blood water potential rises, the pituitary gland will release __________ ADH.
LESS
Which part of the brain detects the level of water in the bloodstream.
The hypothalamus
