Homeostasis And Excretion Flashcards
What happens in the Bowman’s Capsule?
- Blood enters the kidney through the renal artery, this splits into smaller and smaller arteries.
- The smallest arteries called arterioles supply the capillaries of the glomerus.
- Due to the HIGH PRESSURE fluid from the blood is forced through the walls of the capillaries and Bowman’s capsule into the centre of the capsule.
Describe ultrafiltration in Bowman’s capsule
- This is when smaller molecules such as water, ions can pass through these filters.
- The cells on either side have gaps and only act as a coarse filter unlike the basement membrane which is the fine molecule filter. This means larger molecules such as RBC and Proteins stay in the blood.
- Filtration occurs as the pressure in the arteriole is higher than Bowman’s capsule. What passes through is called the glomerular filtrate.
How does your body control the water content?
- As you body looses water your blood becomes more concentrated.
- This is detected by you hypothalamus in your brain.
- Your hypothalamus sends a signal to toy pituitary gland to release more ADH (anti-diuretic hormone).
- As the ADH travels through your blood to the kidneys this makes the collecting ducts to become more permeable to water, so that more water is reabsorbed.
- This will make the urine more concentrated so that the body loses less water and the blood becomes more dilute.
What happens in the proximal convoluted tubule?
This is where selective reabsorption of glucose into the blood, using active transport, against concentration gradient, as it is needed by the cells for respiration
What happens in the Loop of Henlé?
distal convoluted tubule and collecting duct
- The descending loop is concerned with the reabsorption of water into the blood (this may be longer to give more chance for example in desert animals)
- On the ascending side as well as in the distal convoluted tubule, sufficient salt is reabsorbed and in the collecting duct sufficient water is reabsorbed into the bloodstream
- Remaining substances including water, salts and urea form urine
What is homeostasis?
- Is the maintaining of a constant internal environment
- Your body wants to stay around 37℃
- Body water content and body temperature are both examples of homeostasis
What is osmoregulation?
Is keeping the water and salt concentration of the internal environment constant
What is excretion?
Is the process by which waste products of metabolism are removed from the body?
Which organs excrete what?
lungs - CO2
Kidney - Urea, water and salt
Skin - water and salt
Where is urea formed?
Since proteins contain nitrogen, when the amino acids are broken down in the liver, they are converted into carbohydrates and the main nitrogenous containing waste product which is Urea, this is passed into the blood to be filtered by the kidneys
What does your body do if it is too hot?
- Sweat glands release more sweat and then the liquid sweat evaporates via latent heat of vaporisation. To do this it needs energy supplied by the body’s heat and so as you sweat and the water evaporates off your skin, heat is transferred from you to the environment cooling you down (in a humid atmosphere the sweat does not evaporate)
- Vasodilation, the arterioles leading to the capillary loops dilate, which increases the blood flow to the skin’s surface, therefore more heat is radiated to the outside so your body cools down
- Hair erector muscles lie flat (relaxed) meaning that more heat is lost since a thinner layer of air is trapped
What does your body do if you are too cold?
- Vasoconstriction, the arterioles leading the surface capillary loops constrict so that blood flow to the surface is reduced, so less heat is radiated to the outside, keeping you warm
- Piloerection, hair erector muscles contract causing the hairs to be pulled upright. This traps a layer of air near to the skin and since air is a poor conductor of heat, this acts as insulation (better on hair mammals and birds than humans)
- Metabolism speeds up which generates more heat, large organs such as the liver can produce a lot of metabolic heat in this way
- Shivering, which is rapid muscle contractions and relaxations, require respiration and so some of the energy is released as heat, which warms the body
- Behavioural changes e.g. animals may huddle together to reduce exposed SA so smaller SA:Volume ratio.
How does size affect heat?
- Smaller organisms cool down quicker as they have a bigger surface area : volume ratio
- Organisms with bigger SA:V can gain or lose heat faster because there is more area for the heat to transfer across
- This allows smaller organisms to loose body heat more easily in hot climates and reduces the change of them overheating, it also means that they are vulnerable in cold environments
- Organisms with smaller SA:V gain or loose heat more slowly because there is less area for the heat to transfer across
- This is why animals living in cold conditions have a compact (rounded) shape to keep their SA to a minimum, reducing heat loss
How is water lost from the body?
Your body takes in water from food and drink but it is lost from the body: -Through the skin as sweat -Via the lungs in breathe -Via the kidneys in urine Your kidneys control the water balance
What will happen on a hot day or when you are exercising?
- Your body will sweat more to cool you down
- You will produce less urine and it will be more concentrated (a darker colour) as your body must retain onto water
- You will loose more water through your breath when you exercise as you are breathing faster
