3.5.4 - Homeostasis Flashcards
Importance of homeostasis
Enzymes are sensitive to temperature or pH changes, and don’t function properly in wrong conditions
Allows for reactions to take place at constant rate
Changes to water potential may cause cells to shrink or burst
Ectotherm definition
Organisms that control body temperature by using the external environment through changing behaviour
Example of an ectotherm
Lizards
Endothermic definition
Organisms that control body temperature by behaviour and internal metabolic activity
How ectothermic organisms control temperature?
Exposing themselves to sunlight/ taking shelter
Gaining hear from the ground
Generating metabolic heat
Colour variations (black for more heat)
Is the body temperature is too high?
The thermoreceptors in the skin/ hypothalamus detect the change
They send an impulse to the heat loss centre of the hypothalamus (in the brain)
The impulse is sent to the skin (effector), and undergoes: vasodilation, sweating, lowering hair, lowering metabolic rate
Vasoconstriction definition
When the body temperature is too low, the lumen of the arterioles near the skin surface gets smaller. This means that there’s a reduction in the volume of blood reaching the surface, so less heat lost
How shivering increases body temperature?
Muscles of the body undergoing rhythmic contractions that produce metabolic heat
How raising hair helps to increase body temperature?
Hair erector muscles in skin contract, raising the hair on body, enabling a thick layer of air which is a good insulator. Heat is conserved
How does sweating reduce body temperature?
Evaporating water from the skin surface requires heat energy, so energy is lost
Hormone characteristics?
Produced by glands that secrete the hormones directly into blood stream
Carried in blood plasma to target cells
Effective in small quantities, but have widespread effects
Target cells definition
Cells on which hormones act, which have receptors on their membranes, which are complementary to the hormones
Pancreas definition
Large gland in the abdomen, produces enzymes for digestion, and hormones for controlling blood glucose levels
Islets of Langerhans defintion
Groups of hormone producing cells in the pancreas
Types of cells in the Islets of Langerhans
Alpha and beta cells
What alpha cells do?
Produce glucagon
What beta cells do?
Produce insulin
Why is it important to control blood glucose levels?
Glucose is main substrate for respiration, providing source of energy (ATP) for almost all organisms
If too low, cells would be deprived of energy and die
If too high, water potential in blood reduces, causing dehydration…
Sources of glucose
Directly from the carbohydrates in the diet
From the breakdown of glycogen
From gluconeogenesis - the production of glucose from other sources (amino acids/ fats)
If blood glucose levels are to high?
The beta cells in Islets of Lamgerhans detect this change, and produce insulin, which causes: Conversion of glucose into glycogen Conversion of glucose into fats Absorption of glucose into cells Increased cellular respiration
Insulin defintion
Globular protein, hormone that brings a fall in the blog glucose levels of a person
If blood glucose levels are too low?
The alpha cells in the Islets of Langerhans detect this change, and produce glucagon, which brings about the:
Conversion of glycogen to glucose
Conversion of amino acids to glucose
Adrenaline definition
Adrenaline is another hormone that brings about a rise in the blood glucose levels, similar to glucagon
It activates an enzyme that breaks glycogen to glucose and inactivates the enzyme that synthesises glycogen from glucose
Type 1 diabetes facts
Develops usually in childhood and quickly. It occurs when the body is unable to produce insulin, so has to be controlled by insulin injections 2-4 times a day
