B3.4 Flashcards
Define Homeostasis
The ability of the body to maintain a constant internal environment despite fluctuations in the external environment and the body’s activities
How is homeostasis usually achieved?
Through a process called negative feedback. If the system is disturbed, it sets in place a series of events to counteract the disturbance and return the body to its original state
What are the steps of negative feedback?
- Deviation of factor from its norm value
- Receptors detect the deviation
- Effectors (eg. hormones) are activated by the receptors and correct the deviation to restore the norm.
What must happen for osmoregulation to be maintained?
Water gained= water lost
How is water gained by the body?
Drinking
Free water in food
Metabolism (water is waste product of respiration
How is water lost by the body?
Evaporation through from lungs and skin
Excretion of urine
Egestion of faeces
What factor affects the length of the Loop of Henle? What does this have to do with the urine concentration?
- The length of the loop is related to the organism’s environment: a long loop conserves water, so animals in dry environments have longer loops.
- eg. beavers’ are short as they take in a lot of water so don’t need to reabsorb lots
- eg. mole rats are long as they dont take in much water so want to reabsorb lots.
- The thicker the medulla so longer the LOH, the more concentrated the urine will be.
What factor affects the Loop of Henle?
The length of the loop is related to the organism’s environment: a long loop conserves water, so animals in dry environments have longer loops.
What are the three areas of the kidney and their purposes?
- Outer cortex: Contains Bowmans Capsules and capillaries for site of blood filtration
- Inner medulla: Contains loop of henle for reabsorption of water and salt
- Renal pelvis: Collects urine from the kidney tubules and funnels it into the ureter.
What is contained in a nephron?
- Bowmans Capsule
- Proximal Convoluted Tubule
- Loop of Henle
- Distil Convouted Tubule
- Collecting Duct
What is the structure and function of Bowman’s Capsules?
- Cavity which contains bunch of capillaries called glomerulus.
- Filters the blood by forcing fluid through the capillaries of the glomerulus, forming a filtrate similar to blood (inc. urea, salt, water, glucose) but without blood cells and proteins as they are too big to pass out of the capillaries
What is the function of the Proximal Convoluted Tubule?
- Returns much of what has been filtered out of blood must be returned to blood through selective reabsorption.
- NaCl, glucose, amino acids and vitamins go back into the blood by active transport.
- Some water follows by osmosis.
What is the structure and function of the loop of Henle?
- The loop crosses both the cortex and the medulla
- Descending limb: Water flows out into the tissue fluid by osmosis (it is reabsorbed back into the blood). This causes the filtrate concentration to be high when it reaches the bottom of the loop.
- Ascending limb: NaCl is actively pumped out of the filtrate. No water follows as this limb is IMPERMEABLE to water. Filtrate gets more and more dilute moving up as the ions are being lost
NOTE: H2O flows out of the descending arm as a result of the Na and Cl ions released next to it making the blood more concentrated.
What is the function of the distil convoluted tubule?
- Secretion of unwanted substances (ammonia) and reabsorption of ions and water.
What is the primary role of the kidneys?
Regulate blood volume and compositions so that homeostasis of water is contained.
