B12 - Homeostasis in action Flashcards
How does the body regulate body temperature?
-thermoregulatory centre in brain (in the hypothalamus) has receptors sensitive to the temperature of the blood
-skin also contains temperature receptors and sends electrical impulses to the TR centre
Keeps body temperature around 37°C
How does the body respond to an increase in temperature?
-TR centre detects increase in temperature
-blood vessels near skin dilate (vasodilation) to radiate heat
-sweat produced from sweat glands (TE converted to KE when it evaporates, reducing temperature)
Explain how vasodilation helps to decrease body temperature:
-more blood flow near surface of skin
-blood loses more heat energy
-cools the blood, which in turn cools the body
How does the body respond to a decrease in temperature?
-TR centre detects decrease in temperature
-blood vessels constrict (vasoconstriction)
-sweating stops
-skeletal muscles contract (shiver)
-hair stands up (makes a layer of insulating air)
Explain what happens to your body temperature when you drink a cold glass of water, and how your body responds in terms of sweating:
-cold water cools the blood in the mouth/stomach
-blood flows to the thermoregulatory centre in the brain and it detects a decrease in temperature
-decreases amount of sweating so less heat is lost in order to prevent further cooling
Explain why you lose more water by breathing during a race:
-more energy needed for muscular contraction, so body needs to perform more aerobic respiration
-breathing rate increased to supply more oxygen to muscle cells and to remove carbon dioxide, and thus more water is lost in the process
What substances do we have + not have control over losing?
control
-water/ions/urea in urination (regulated by kidneys)
no control
-water via lungs during exhalation
-water/ions/urea from skin in sweat
What happens when cells undergo severe osmotic changes?
-too much water lost/gained
-cells don’t function efficiently
How is the digestion of excess proteins managed?
-proteins digested by protease into excess amino acids which need to be excreted safely
-amino acids deaminated in liver to form toxic ammonia
-ammonia is converted to urea (also in liver)
-safely excreted through kidneys + urine
What is the function of kidneys?
to produce urine by the filtration of the blood to remove urea, and the selective reabsorption of useful substances like glucose, some ions and water
ALWAYS SAY THAT IT FILTERS THE BLOOD, THERE IS NO DIFFUSION INVOLVED IN THE KIDNEYS
How are water levels regulated in the body?
-controlled by ADH which INCREASES THE PERMEABILITY of kidney tubules
-released by pit. gland when blood has too little water, so more water is reabsorbed back into blood from tubules
This process is controlled by negative feedback
4.5.3.3 - Knowledge of other parts of the urinary system, the structure of the kidney and the structure of a nephron is not required.
What would happen if a person’s kidney failed?
-unable to regulate water/ion/urea levels, cells damaged by osmosis
-waste substances and toxins build up in blood stream
-can become sick + die
Describe 2 treatments for kidney failure:
-transplant (surgical procedure, transferring healthy kidney from donor to patient)
-dialysis (artificial kidney that filters blood)
Explain the process of dialysis:
-unfiltered blood leaves arm and is pumped through machine with a PPM next to some dialysis fluid
-dialysis fluid has the ideal concentrations of glucose/water/ions (and 0 urea), so excess amounts of substances will diffuse out down a CG
-the blood eventually is fully filtered as it gets circulated (dialysis fluid is also pumped to maintain conc. gradient)
-filtered blood is returned to arm
Give some pros and cons of dialysis:
-no lack of dialysis machines (as there is with kidney donors)
-no immunosuppressants needed
-very time consuming + expensive
-painful
