Homeostasis Flashcards
(56 cards)
Define homeostasis
The maintenance of a stable equilibrium in the conditions inside the body
What do negative feedback loops aim to do?
Reverse the initial stimulus
What do positive feedbacks aim to do?
A change in the internal environment is detected by sensory receptors and effectors are stimulated to reinforce the change and increase the response
Define thermoregulation
Maintenance of a relatively constant core body temperature to maintain optimum enzyme activity
Define ectotherm
Animals that use their surroundings to warm their bodies so their core temperature is heavily dependent on outside environment
Define endotherm
Animals that rely on their metabolic processes to warm their bodies and maintain their core temperature
Draw a graph to show the effect of changes in the internal and external temperature on ectotherms and endotherms
External temperature on x axis
Body temperature on y axis
Ectotherm linear relationship not passing through the origin
Endotherm horizontal line around 37C
What are behavioural responses that some ectotherms have to changes in temperature?
Orientating themselves to have maximum exposure to the sunshine
Conduction by placing their bodies on the warm ground
Seeking shade to decrease temperature
What are 2 key physiological responses ectotherms have?
Colour changes in their skin
Alter heart rate to change metabolic rate
Where are peripheral temperature receptors in endotherms?
Skin
Where are the 2 temperature receptors found in the body?
Skin
Hypothalamus
What are the three mechanisms that endotherms have to cool down?
Vasodilation
Increased sweating
Reducing the insulating effect of hairs
Explain what vasodilation is and how it leads to cooling of the body
Arteries near the surface of the skin dilate
Forces blood through capillary networks near the surface of the skin
Skin flushes and cools as a result of increased radiation
Explain how sweating leads to heat loss
Sweat evaporates from the surface of the skin so heat is lost and the surface below cools
Explain how hair can be used to cool the body
The erector pilli muscles in the skin relax
Hairs lie flat on the skin
Avoids trapping an insulating layer of air
Describe the 4 processes that occur to warm up an endotherm
Vasoconstriction
Decreased sweating
Raising the body hair or feathers
Shivering
Explain how vasoconstriction causes warming in the body
Arterioles near surface of the skin constrict
Arteriovenous shunt vessels dilate so little blood flows through the capillary networks close to the surface of the skin
Little radiation occurs and warm blood is kept well below the surface
Explain the process of shivering within an endotherm
The rapid, involuntary contraction and relaxation of large voluntary muscles in the body
What are the two control centres in the control of thermoregulation?
Heat loss centre
Heat gain centre
Explain how the heat loss centre is activated
Temperature of the blood flowing through the hypothalamus increases
Sends impulses through the autonomic motor neurons to effectors in the skin and muscles triggering responses to lower core temperature
Explain how the heat gain centre is activated
Temperature of the blood flowing through the hypothalamus decreases
Sends impulses through the autonomic nervous system to effectors in the skin and muscles triggering responses to increase core temperature
How is oxygenated blood supplied to the liver?
Hepatic artery
How is deoxygenated blood removed from the liver?
Hepatic vein
What is the role of the hepatic portal vein?
To carry blood containing the products of digestion straight from the intestines to the liver
