Edexcel Biology Gcse - Coordination and Control - The Human Endocrine System Part 3
This deck Nutrients such as sugars, starch, and cellulose that provide energy for humans and are used in plants for photosynthesis; excess is stored as fat.
Homeostatic control
| Negative feedback mechanism
A negative feedback mechanism is an important type of control that is found in homeostasis. A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback.
Key Terms
Homeostatic control
| Negative feedback mechanism
A negative feedback mechanism is an important type of control that is found in homeostasis. A negative feedback control system responds when condit...
General stages in negative feedback
| In general this works by:
if the level of something rises, control systems reduce it again
if the level of something falls, control systems raise it again
Negative feedback
| any order (is a loop)
Change detected
→
Corrective mechanisms activated
→
Conditions returned to set point
→
Corrective mechanisms sw...
An example of negative feedback is the control of body temperature.
An example of negative feedback is the control of body temperature. Body temperature is controlled by the hypothalamus in your brain. If your body ...
Thyroxine
Thyroxine is produced from the thyroid gland, which stimulates the metabolic rate. It controls the speed at which oxygen and food products react to...
The hypothalamus and pituitary gland have important roles in detecting and controlling thyroxine levels.
low thyroxine levels
1) Low thyroxine levels in the bloodstream stimulate the hypothalamus to release TRH and this causes the pituitary to release TSH so the thyroid re...
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| Term | Definition |
|---|---|
Homeostatic control | Negative feedback mechanism | A negative feedback mechanism is an important type of control that is found in homeostasis. A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback. |
General stages in negative feedback | In general this works by: | if the level of something rises, control systems reduce it again if the level of something falls, control systems raise it again |
Negative feedback | any order (is a loop) | Change detected → Corrective mechanisms activated → Conditions returned to set point → Corrective mechanisms switched off → Conditions in the body change from set point |
An example of negative feedback is the control of body temperature. | An example of negative feedback is the control of body temperature. Body temperature is controlled by the hypothalamus in your brain. If your body gets too hot, your body begins to sweat, which reduces body temperature. In the opposite way, if the body gets too cold, your body begins to shiver to raise body temperature. |
Thyroxine | Thyroxine is produced from the thyroid gland, which stimulates the metabolic rate. It controls the speed at which oxygen and food products react to release energy for the body to use. Thyroxine also plays an important role in growth and development. Its levels are controlled by negative feedback. |
The hypothalamus and pituitary gland have important roles in detecting and controlling thyroxine levels. | 1) Low thyroxine levels in the bloodstream stimulate the hypothalamus to release TRH and this causes the pituitary to release TSH so the thyroid releases more thyroxine. So blood levels return to normal. |
The hypothalamus and pituitary gland have important roles in detecting and controlling thyroxine levels. | Normal thyroxine levels in the bloodstream inhibit TRH release from the hypothalamus and the production of TSH by the pituitary, so normal blood levels are maintained. |
The control of thyroxine levels by the hypothalamus and pituitary gland is an example of what? | The control of thyroxine levels by the hypothalamus and pituitary gland is an example of negative feedback. |
Adrenaline | Adrenaline is produced by the adrenal glands in times of fear or stress. It targets vital organs, increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles. Preparing the body for 'flight or fight'. Adrenaline is not controlled by negative feedback. |
When adrenaline is released into the bloodstream it creates multiple effects: | 1) increases breathing rate, heart rate (therefore blood flow) and blood pressure 2) conversion of glycogen to glucose in liver cells, increasing blood glucose These effects result in more glucose being delivered to the muscles and more energy being released by respiration in the muscles. |
What do the effects of adrenaline do? | The effects of adrenaline allow the body to prepare for action in situations where a quick response may be needed. |
Regulating blood glucose | Glucose is needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level and controlled carefully. Insulin is a hormone produced by the pancreas which regulates glucose concentrations in the blood. |
What happens if the blood glucose concentration is too high? | If the blood glucose concentration is too high, the pancreas produces the hormone insulin, this causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage, and will be used at a later date. |
Action of insulin | effect of low glucose on pancreas | Insulin not secreted into the blood |
Action of insulin | effect of high glucose on pancreas | Insulin secreted into the blood |
Action of insulin | effect of low glucose on liver | Does not convert glucose into glycogen |
Action of insulin | effect of high glucose on liver | Converts glucose into glycogen |
Action of insulin | effect of low glucose on blood glucose level | Increases |
Action of insulin | effect of high glucose on blood glucose level | Decreases |
how insulin works in the body | high levels of glucose | 1) too much glucose in the blood 2) pancreas produces insulin which enters blood 3) Insulin allows glucose to be absorbed by body cells 4) blood glucose is reduced. |
how insulin works in the body | low levels of glucose | 1) normal levels of glucose in the blood 2) insulin not produced by the pancreas 3) Less glucose absorbed by body cells 4) Blood glucose remains the same. |
What is diabetes? | Diabetes is a condition where the blood glucose levels cannot be controlled by the body. There are two types of diabetes - type 1 and type 2. |
What is type 1 diabetes? | Type 1 diabetes is a disorder in which the pancreas fails to produce enough insulin. This can be detected from an early age. It is characterised by uncontrolled high blood glucose levels and it can be controlled by injecting insulin. |
Effect and mangement of type 1 diabetes | People with type 1 diabetes have to monitor their blood sugar levels throughout the day. Their levels of physical activity and their diet affect the amount of insulin needed. |
Control (somewhat) of type 1 diabetes | They can help to control their blood glucose level by being careful with their diet, and eat foods that will not cause large increases in blood sugar level, and by exercising, which can lower blood glucose levels due to increased respiration in the muscles. |