6.4 Homeostasis

• Homeostasis is the maintenance of a stable internal environment
• 3 internal conditions that are maintained by homeostasis?

  Temperature, pH, blood sugar levels
• negative feedback loops are when the body responds to a stimulus to restore homeostasis
• positive feedback loops are when a change in the environment causes a change in the organism that amplifies the change
• normal concentration of glucose in the blood?

  90mg per 100cm^3
• after eating blood glucose rises
• after exercise blood gluocse falls
• insulin lowers blood glucose concentration when its too high
• Glucagon raises blood glucose concentration when it's too low
• Beta cells secrete insulin
• Alpha cells secrete glucagon
• glycogenolysis is the breakdown of glycogen into glucose
• glycogenesis is the formation of glycogen from glucose
• insulin binds to specific receptors of liver cells and muscle cells
• glucagon binds to specific receptors of liver cells
• what does insulin activate?

  glucose uptake, enzymes for glycogenesis, increases rate of respiration
• what does glucagon activate?

  enzymes for glycogenolysis and for gluconeogenesis, decreases rate of respiration
• glycogenolysis is the breaking down of glycogen
• negative feedback mechanisms keep glucose concentrations normal
• how is glucose transported into a cell?

  facilitated diffusion using channel protein GLUT4
• adrenaline is a hormone that is secreted by adrenal glands
• adrenaline binds to receptors of liver cells
• adrenaline activates glycogenolysis and inhibits glycogenesis
• what is the second messenger called?

  cyclic AMP
• what does cAMP do?

  activates protein kinase A, which leads to glycogenolysis
• adrenaline and glucagon act via a second messanger
• diabetes occurs when blood glucose concentration isn't controlled
• function of the renal artery?

  carry oxygenated blood to kidneys
• function of renal vein?

  carry deoxygenated blood away from kidneys
• function of kidney?

  regulate water content of blood
• function or ureter?

  carry urine from kidneys to bladder
• function of bladder?

  stores urine
• function of urethra?

  releases urine
• what surrounds the kidney?

  fibrous capsule
• what are the three main areas of the kidney?

  cortex, medulla, renal pelvis
• what is the function of nephrons?

  filtration and reabsorption
• what is the functional unit of the kidney?

  nephron
• where does ultrafiltration occur?

  bowman's capsule
• where does selective reabsorption occur?

  proximal convoluted tubule
• what factors affect water potential?

  pressure and solute concentration