C12 - Homeostasis Flashcards
What is Homeostasis?
The maintenance of a constant internal environment within a living organism.
What is an internal environment?
An internal environment refers to the prevailing conditions within the cells of the body
What is the set point
The setpoint is the baseline which allows optimal and constant cell function inside the body.
What is the benefit of homeostasis?
Or…
What is the benefit of maintaining a constant internal environment?
- Homeostasis keeps the concentration of body fluids at a constant and optimal level to allow normal cell function in the body…
- Homeostasis helps to
- Protect cells from changes in the external environment
- Ensures reactions occur at a constant and appropriate rate
- & allows cells to function normally
What is meant by negative feedback
A change in a system,
produces a second change
which reverses the first change.
What does the control of a self-regulating system by -ve feedback mechanism involve
It involves a series of stages, in which an output from an effector reduces the stimulus and restores the system to its original level
What is the series of stages in which the Negative feedback works
- The setpoint is the norm at which the system operates
- A receptor detects the level of the factor and its deviation from the setpoint.
- The receptor sends instructions to a controller
- The controller communicates 1 or >1 effectors.
- The factor returns to normal as the effectors reduce the level.
- The receptor sends a signal to the controller once the factor has reached the normal to stop the effectors.
What is the first step of the negative feedback cycle
The set point for a factor is the norm at which the system operates
what is the second step of the negative feedback cycle
A receptor detects the level of the factor and its deviation from the set point
What is the third step of the negative feedback cycle
The receptor sends instructions to a co-coordinator or controller
What is the 4th step of the negative feedback cycle
4/the co-coordinator communicates with one or more effectors e.g. muscles or glands
what is the 5th and final step of the negative feedback cycle
the factor returns to normal,
This is identified by the receptor
and information is fed back to the effectors,
which stop making the correction
What are 2 examples of negative feedback cycles
- Glucose concentration in the plasma
- Core temperature of the body
What happens if the glucose concentration in the plasma increases above the set point
insulin is secreted.
Reduces the glucose concentration by converting it into glycogen
increasing the rate at which it is respired hence reducing the concentration
What happens if the glucose concentration in the plasma decrease below the set point
Glucagon is secreated resulting in glycogen being converted into glucose which increases the glucose concentration
What happens if the body’s core temperature falls below the set point
Increased respiration generates heat
constriction of superficial blood vessels allows the body to retain it,
hence increasing core body temperature
What happens if the body’s core temperature rises above the set point
Superficial blood vessels dilate,
heat radiates from the body reducing its temperature
What is a positive feedback mechanism in the body and how does it work
If a factor moves from a set point, a positive feedback mechanism increases the movement already made from the set point, further.
What are two examples of positive feedback
- Oxytocin
- Clotting factors
Why is Oxytocin a positive feedback mechanism?
Oxytocin is released at the end of pregnancy and stimulates the contraction of the uterus
The contractions stimulate the production of more oxytocin which increases the length, intensity and frequency of contractions i.e. The stimulus.
How does the clotting mechanism use positive feedback
When the skin is cut
The first stage of clot formation occurs when platelets adhere to the surface
These platelets secrete signaling molecules which attract more platelets to the site.
