SBI 4U1 ~ Exam Review ~ Unit 3 ~ Homeostasis
- negative loops bring it back to range of tolerance, while positive bring farther away from range of
tolerance, intensifying the response.
Get these loops from your notes okay:
Thermoregulation, blood sugar, ADH/ aldosterone, metabolism (thyroid)
Thermoreg Loop needed info:
Physiological Effects when temperature increases - sweat (heat of evaporation)
- vasodilatation (radiator effect)
- bp decreases, offset by increased heart rate
Behavioural Effect when temp increases: - go into AC, shade, a pool, fan yourself
- drink cold drinks, wear little clothing
Physiological Effect when temp decreases: - shivering, increased blood flow
- hair stands on end (goose bumps) from muscle contraction
- waste product of respiration -> heat!
Behavioural effects when temp decreases: - increased physical activity, clothing
- warm food/drink
- change environment, furnace, fire
- Heat Escape Lessening Position (H.E.L.P.) compact body
The Nephron: Labelling
The Kidneys: Their Main Functions - remove nitrogenous wastes
- control sodium/water balance
- control blood and body pH
- release hormones
Something hunks said that seems important: controlling water balance side effect â water impacts blood
volume & pressure. Retaining more water increases pressure on blood vessel walls, impacts heart rate.
Filtration: â¢ Occurs at glomerulus where the fluids leave the capillaries & enter the Bowmanâs capsule. Only
water, salt, glucose, amino acids & hydrogen ions pass through the selective membrane of the
glomerulus, while blood cells, platelets & plasma can not. The fluid that continues through the
nephron is called the filtrate.
â¢ The renal artery entering the Bowmanâs capsule increases in pressure from 2 KPa to 8KPa. As
vessel size decreases, pressure increases. (the arteries turn into arterioles)
â¢ The filtrate now goes in the proximal convoluted tubule, where most of the fluids lost in filtration
are reabsorbed into the blood. The fluids include glucose, water and minerals. The rich supply of
mitochondria in the proximal to absorb the glucose.
â¢ Now entering the descending loop of Henle, (into medulla) water is moving out, since this part of
the loop is permeable to water not salt. So as the filtrate moves down there is an increase in salt.
â¢ Now going to the ascending loop of Henle, (into cortex) where it is permeable to salt, not water.
As sodium moves out chlorine follows because of the opposite charge.
â¢ The capillary network that parallels the loop of Henle participates in the salt gradient formation. It
recirculates salt and urea within the medullaâs tissues, but transports water out of the medulla.
Urea and salts are kept in the tissue so that water can be reabsorbed. (tissue is hypertonic to fluid
in the tubule).
â¢ Happens in the distal convoluted tubule. Secretion of drugs happens via active transport into the
tubule. Active transport is what allows materials to move from the blood into the tubule like
hydrogen ions and bicarbonates.
- Glucose: using Benedictâs. After heating, a colour change to orange shows a positive test for sugars. A
negative test would show no colour change, or kind of greenish. High sugar level in urine could be a sign of
diabetes mellitus. The high level of glucose in the diabeticâs blood affects the reabsorption of glucose back
into the blood from the nephron.
- Proteins: Using Biuretâs. A colour change to light purple indicates a positive test for proteins. Urine does
not usually have protein present, so reasons for the presence could be fever, hard exercise, pregnancy,
- pH Test: The normal pH range for urine is from 5-7. A flux in this range could be from exercise because
of lactic acid build up, affecting the urineâs pH.
- Specific Gravity: normal range is 1.002-1.030. Measures the concentration of all chemical particles in the
urine. A flux in the range could be from not drinking enough water, making the urine more concentrated.
- Ketones: the normal test is negative. When fat is broken down for energy (last resort after glucose),
ketones are present in the urine. A diet low in sugars and starches (carbohydrates), starvation, or after long
strenuous exercise may cause a pos. test.
Know your STSE topic!!(from urinalysis lab) Either xenotransplants, haemodialysis, transplants & donors
or peritoneal dialysis. Connect it to society, impact on the person, their family, their lifestyle.
Endocrine System ! â¢ The endocrine glands produce hormones. They donât excrete externally, but directly into the
â¢ The hypothalamus is the coordinating centre
â¢ The thyroid controls metabolism, the parathyroid controls calcium
Pituitary: The Master Gland. Itâs Hormones & Targets:
In the Anterior Lobeâ¦
- GH (Growth Hormone): somatotropin targets body cells, bones, stimulates growth
- PRL: prolactin targets mammary glands for milk production, so it is only necessary for
- TSH: (thyroid stimulating hormone) targets thyroid gland to help regulate metabolic rate
- FSH, LH: (follicle stimulating and luteinizing hormones) are both gametes. stimulate the
gonads; eggs, testes, sperm
- ACTH: (adrenocorticotropic hormone) targets adrenal cortex, helps stress response.
Increases hr, bp, adrenaline, fight/flight mechanism)
In the Posterior Lobeâ¦
- ADH (anti diuretic hormone): targets the nephron, allows us to reabsorb 15% of filtrate
- Oxytocin: induces contractions in the walls of uterus when giving birth