Homeostasis Flashcards
How is temperature control achieved by?
monitoring the temperature of the body and the surroundings, comparing the actual body temperature with the desired set point, controlling effectors to conserve heat
What is homeostasis?
is the maintenance of conditions inside the body at a near constant level
What are the homeostasis mechanisms?
receptors(monitoring core body temperature and temp of surroundings), control centre, coordination system, effectors in the skin
Where is the body’s thermostat?
hypothalamus in the brain
What is mechanism for body temp?
negative feedback- because the responses stimulated by the hypothalamus counteract the change in body temp, also reduces the difference between actual body temp and set point
What 4 ways do cells signal to each other using chemicals?
cell signalling chemicals are released by cells to influence other cells in the immediate area
cells in ductless glands secrete hormones into the blood
nerve endings release neurotransmitter chemicals at synapses
nerve endings release hormones into the blood
What are target cells & hormones?
tc-are receptors on the surface of cells specifically for hormones eg adrenaline
hormones- are chemical substances that acts as messengers molecules in the body
What parts of the body work together to supply cells with glucose?
the digestive system- digests starch to glucose & absorbs it into the blood
the endocrine system- the islets of Langerhans in the pancreas secrete insulin and glucagon to control the concentration of glucose in the blood
the liver and muscles store glucose as glycogen
the circulatory system- transport glucose, insulin & glucagon dissolved in the plasma
What happens when the glucose concentration is above the set point?
Beta cells in the islets of Langerhans act as glucose detectors, b cells secrete insulin in response to an increasing concentration of glucose in the blood, insulin circulates in the bloodstream and binds to insulin receptors on target cells, insulin receptor is a transmembrane protein in the cell surface membrane of the target cells, binding of insulin to its receptor stimulates the formation of a second messenger that activates target cells to absorb and use glucose
What effect does glucose have on liver cells?
it increases the use of glucose, inhibits the enzymes that break down glycogen to glucose, inhibits the conversion of fats and proteins into glucose
What happens when glucose concentration decrease below the set point?
alpha cells in the islets of Langerhans respond to decreasing concentrations of glucose by releasing glucagon, glucagon circulates in the bloodstream and binds to glucagon receptors on liver cells, the receptor interacts with other membrane proteins to increase the concentration of cyclic AMP inside liver cells
What effect does glucagon have on liver cells?
it stimulates glycogenolysis by activating the enzymes that break down glycogen, stimulates the conversion of fat and protein into intermediate metabolites that are converted into glucose(gluconeogenesis)
What is ethylene(plant hormone)?
its a small molecule that is volatile and forms a gas almost as soon as it is diffuse out into the atmosphere, stimulates fruit ripening
What is an example of ripening with ethylene?
unripe tomatoes are green, when ripening they stop synthesising chlorophyll and produce red pigment lycopene
enzymes convert starch and organic acids to sugar
volatile chemicals are produced that give ripe tomatoes their characteristics smell
enzymes hydrolyse pectins in cell walls, pectin hold cellulose fibres together once broken down, fruits become much softer
