Homeostasis Flashcards
(28 cards)
What is homeostasis?
The maintenance of a constant internal environment in organisms
Ensuring that cells are in an environment that meets their needs despite external changes
Why is homeostasis important?
Enzyme function - temperature and pH
Water potential- blood glucose level
Gives an organism a wider geographical range and a greater chance of finding food
What is the control mechanism for homeostasis?
Set point the desired level. Monitored by the…
Receptor detects deviation. Informs the…
Controller coordinates information sending instructions to an appropriate…
Effector brings about change. Creates a…
Feedback loop informs the receptors of the changes
How do animals gain heat?
Produce heat through respiration
Gain heat from the environment by conduction, convection and radiation
How do animals lose heat?
Evaporation of water - sweat
Loss of heat to the environment though convection, conduction and radiation
What is an endotherm?
Metabolic processes happen inside the body
‘Inside heat’
Endo = indo
What are ectotherms?
Obtain most heat from outside their bodies
‘Outside heat’
How do ectotherms regulate body temperature?
Expose themselves to the Sun
Take shelter to prevent over heating
Gain warmth from the ground
Generate metabolic heat
Colour variations - black absorbs more heat
How do endotherms regulate body temperature?
Internal metabolic activities
34-44 degrees C
Conserving heat in a cold environment
Small surface area to volume ratio
Smaller extremities
Vasoconstriction- diameter of the arterioles is made smaller
Shivering- produces metabolic heat
Hair raising- trapping a layer of air by the body
Decrease in sweating
Increased metabolic rate
Losing heat in a warm environment
Large surface to volume ratio
Light coloured
Vasodilation- arterioles diameter increases
Increased sweating
Lower body hair
Behavioural mechanism- avoid heat by sheltering
How is the hypothalamus used in controlling body temperature?
The stimulus is detected by receptors
These pass information to the hypothalamus
Causing the effector to produce a response
What happens in the hypothalamus?
A thermoregulatory centre consisting of:
Heat gain centre activated by low temperature
Heat loss centre activated by high temperature
Characteristics of hormones
Produced by glands
Carried in the blood plasma
Act on target cells
Effective in small quantities and have long lasting effects
What is the second messenger model used for?
Used by two hormones, adrenaline and glucose to regulate blood glucose
How does the second messenger model work?
A hormone is the first messenger and binds to a specific receptor on the cell membrane forming a hormone-receptor complex
Hormone-receptor complex activated an enzyme inside the cell - second messenger
Enzymes cause chemical changes produce a response. Adrenaline converts glycogen to glucose
What is the pancreas used for?
Produces enzymes used in digestion and hormones used to regulate blood glucose
Islets of Langerhans
Found in the pancreas and produce the hormones
Two types of cell:
a cells - larger and produce GLUCAGON
B cells - smaller and produce INSULIN
Insulin and the B cells of the pancreas
Detect a rise in blood glucose level and respond by secreting insulin
What changes does insulin cause?
Change the tertiary structure of the glucose transport protein allowing more more glucose in
Increases the number of carrier molecules in the cell membrane
Activation of enzymes that convert glucose to glycogen and fat
How is blood glucose lowered?
Increase rate of glucose absorption into cells
Increasing respiratory rate of cells
Increasing the rate of conversion of glucose to glycogen
Increase the rate of conversion of glucose to fat
Glucagon and the a cells of the pancreas
Detect a fall in blood glucose by secreting glucagon into the blood plasma
Only liver cells have receptors that bind to glucagon
How do liver cells respond to glucagon?
Activate enzymes to convert glycogen to glucose
Increase gluconeogenesis (amino acids and glycerol into glucose)
Cause of type I diabetes
The body is unable to produce insulin
Maybe as a result of an autoimmune response whereby the body’s immune system attacks it’s own cells
