🫘Maintaining Internal Environments Flashcards
What is homeostasis and why is it important?
Homeostasis is the regulation of internal conditions (like temperature, water, pH, and glucose) to maintain a stable environment for enzyme function and cell health.
If homeostasis fails, enzymes may denature and cells can be damaged or die.
What are the components of a control system in homeostasis?
Receptors detect changes (stimuli)
Coordination centres (brain, spinal cord, pancreas) process info
Effectors (muscles/glands) bring about a response to restore balance
This often works through negative feedback loops.
What are the main parts and roles of the nephron?
Parts of the nephron:
Bowman’s capsule & glomerulus: ultrafiltration
Convoluted tubules & Loop of Henlé: selective reabsorption
Collecting duct: water reabsorption (regulated by ADH)
Main roles:
Remove waste (urea)
Reabsorb useful substances
Control water balance
What happens during ultrafiltration and selective reabsorption?
Ultrafiltration: Small molecules (glucose, water, urea, ions) forced from blood into Bowman’s capsule. Proteins & blood cells stay in blood.
Selective reabsorption:
All glucose (by active transport)
Water (by osmosis, depending on need)
Ions (by diffusion)
What does ADH do and how does it control water levels?
(and what does it do to urine conc_)
ADH (anti-diuretic hormone), from the pituitary gland, controls how much water is reabsorbed in the collecting ducts of the kidney:
Low water: More ADH → more water reabsorbed → concentrated urine
High water: Less ADH → less water reabsorbed → dilute urine
This is part of a negative feedback system.
How and why does the composition of urine vary?
High water intake: Pale, dilute, large volume of urine
Low water intake / dehydration: Dark, concentrated, small volume
Urine always contains urea, excess salts, and water, but amounts vary to help maintain internal balance.
How does the body regulate temperature?
Via the thermoregulatory centre in the hypothalamus:
Too hot: Vasodilation, sweating, hairs lie flat
Too cold: Vasoconstriction, shivering, hairs stand up
These responses maintain enzyme activity around 37°C.
How is blood glucose concentration controlled?
Too high: Pancreas releases insulin, converting glucose → glycogen in liver
Too low: Pancreas releases glucagon, converting glycogen → glucose
This maintains glucose levels via negative feedback.
What are the effects of dehydration and overhydration?
Dehydration: Headache, tiredness, dark urine, dizziness → kidneys reabsorb more water
Overhydration: Headache, confusion, potential brain swelling → kidneys excrete more water
Both disrupt osmotic balance and affect brain and kidney function.
What happens to animal cells in different water potentials?
In low water potential (e.g. salty solution): water leaves cell → cell crenates (shrivels)
In high water potential (e.g. distilled water): water enters cell → cell may burst (lysis)
Animal cells lack a cell wall, so they are sensitive to osmosis.
