Homeostasis Flashcards
Why is it important that our pH level is maintained?
If the pH of your blood is too low or too high then enzymes become denatured because the hydrogen bonds get broken. The shape of the active site gets changed so the enzyme cannot work.
Why is it important that blood glucose concentration is maintained?
If the blood glucose concentration is to high then the water potential of the blood is reduced. Therefore, water will move out of cells into the blood by osmosis. This can causes cells to shrivel up and die.
If blood glucose concentration is too low, cells are unable to carry out normal activities because there isn’t enough glucose for respiration.
What is negative feedback?
Negative feedback is a mechanism that restores the level of something and restores it to normal. E.g. If blood glucose concentration is too low then it will get detected and your negative feedback system will make more glucose.
What is positive feedback?
When there is a change in the level of something and your body responds and the level changes even further away from the normal level, e.g. When you get hypothermia the brain doesn’t work properly so you stop shivering and your body temperature falls even more.
What are ectotherms and how do they control there body temperature?
Ectotherms are animals that cannot control their body temperature internally, e.g. Reptiles. They control their body temperature by changing their behaviour. Their internal temperature depends on the external temperature. They are more active at high temperatures and less active at low temperatures. There metabolic rate varies lots and they generate very little heat.
What are endotherms and how do they control their body temperature?
Endotherms are animals that control their body temperature by homeostasis. They can also control their body temperature by changing their behaviour. Their internal temperature is less affected by external temperature. They can active at almost any temperature. They always have a high metabolic rate and they generate lots of heat.
What mechanisms do mammals have to increase there heat loss (if they are too hot) ?
Sweating - more sweat is secreted when the body is too hot. Water in sweat evaporates from the surface of your skin and takes heat from body, which cools the skin.
Hairs lie flat - when it is hot hair erector muscles relax so the hairs lie flat. Air isn’t trapped between the skin and hairs, so the skin is less insulated and hear is easily lost.
Vasodilation - when it is hot arterioles near the surface of the skin dilate so more blood runs through the capillaries. Therefore, more heat is lost from the skin by radiation and your temperature is lowered.
What mechanisms so mammals have to produce heat (when you are cold) ?
Shivering - when you are cold, muscles contract in spasms to make you shiver and produce more heat from increased respiration.
What mechanisms to mammals have to conserve heat?
Less sweating - less sweat is secreted when you are cold, so less water from sweat is evaporated from the skin, so heat loss gets reduced.
Hairs stand up - hair erector muscles contract when it is cold. This makes the hairs stand up and trap a layer of air between the skin and hairs, so this prevents heat loss.
Vasoconstriction - when it is cold arterioles near the surface of your skin constrict, so less blood flows through the capillaries at the surface of the skin. This reduces heat loss.
What is the part of the brain called that maintains body temperature in mammals?
Hypothalamus
What are the two ways that the hypothalamus receives information?
The hypothalamus receives information about the internal body temperature when thermoreceptors detect blood temperature.
Also, the hypothalamus receives information about the external temperature when thermoreceptors in the skin detect skin temperature.
What happens when a very cold or very hot external temperature is detected?
Thermoreceptors in the skin detect a low/high external temperature. The thermoreceptors send impulses along sensory neurones to the hypothalamus. The hypothalamus then sends impulses along motor neurones to effectors. The effectors respond by doing heat loss/heat conservation mechanisms to maintain the body temperature as much as possible.
How does insulin lower blood glucose concentration?
Insulin is secreted from the islets of langerhans. It binds to specific receptors on cell membranes of liver or muscle cells. It increases the permeability of these cell membranes, so the cells take up more glucose. Insulin activates enzymes that convert glucose into glycogen. The cells can store glycogen as an energy source. This process of converted glucose to glycogen is called glycogenesis.
How does glucagon increase blood glucose concentration?
Glucagon binds to receptors on the cell membranes of liver cells. Glucagon activates enzymes which break down glucagon into glucose. The process of breaking down glucagon into glucose is called glucogenolysis. Glucagon can also cause fatty acids and amino acids to form glucose. This process of forming glucose from non carbohydrates is called gluconeogenesis.
How does negative feedback keep our blood glucose concentration constant?
If there is a rise in blood glucose concentration, then beta cells release insulin into the blood. Insulin then binds to receptors on liver cells, so the cells take up more glucose from the blood. Enzymes concert glucose into glycogen (glycogenesis).
If blood glucose concentration falls, then alpha cells release glucagon into the blood. Glucagon binds to receptors on liver cells. Enzymes convert glycogen into glucose (glycogenolysis) and glucose is formed by amino acids and fatty acids (gluconeogenesis).
