D3.3 Biology SL/HL

This is for IBDP Biology SL/HL students

Explain the control of blood glucose concentration

concentration of glucose dissolved in blood plasma. Usually stays within 4 mmol dm-3 and 8 mmol dm-3 to maintain osmotic balance of the blood. If level is too high or too low, alpha and beta cells produce hormones to correct it

What is the function of alpha and beta cells?

Found in regions of the pancreas (Islets of Langerhans) and produce hormones that turn on control mechanisms to correct low or high blood sugar → negative feedback

Outline responses to a rise in blood glucose above normal

beta cells produce insulin to stimulate cells in the liver and muscles to take in glucose and convert it to glycogen and fat

Outline response to a fall in blood glucose below normal

alpha cells in the pancreas produce glucagon that stimulates hydrolysis of glycogen to glucose in liver cells

Distinguish between Diabetes Type I and Type II

beta cells do not produce insulin and glucose is not up by body cells so blood levels remain high (hyperglycemia) / the pancreas does produce insulin but body cells fail to respond to insulin → hyperglycemia

What is the function of thyroxine

produced in thyroid and regulates metabolic rate and helps to control body temperature

Outline physiological changes if there is an increase in temperature

Vasodilation (arterioles supplying blood to the skin dilate), muscles attached to hair in the skin relax, sweat glands are activated

Outline physiological changes if there is a decrease in temperature

Vasoconstriction (arterioles supplying blood to skin constrict), muscles attached to hairs in the skin contract, decrease sweat production, metabolic activity in the liver increases

What is osmoregulation?

Maintenance of proper balance of water and dissolved substances in an organism: regulation of osmotic concentration

What is the role of the nephron in the bowman’s capsule + glomerulus?

Ultrafiltration

What is the role of the nephron in the proximal convoluted tubule?

Selective reabsorption from filtrate

What is the role of the nephron in the loop of henle?

Water conservation

What is the role of the nephron in the distal convoluted tubule?

pH adjustment and ion reabsorption

What is the role of the nephron in the collecting duct?

Water reabsorption

What is the function of the loop of Henle?

Enable the kidneys to conserve water

What is ADH and when is it secreted?

Secreted by posterior pituitary when water content of the blood is low