C12 - Homeostasis

Question 1

What is Homeostasis?

Answer 1

The maintenance of a constant internal environment within a living organism.

Question 2

What is an internal environment?

Answer 2

An internal environment refers to the prevailing conditions within the cells of the body

Question 3

What is the set point

Answer 3

The setpoint is the baseline which allows optimal and constant cell function inside the body.

Question 4

What is the benefit of homeostasis?

Or…

What is the benefit of maintaining a constant internal environment?

Answer 4

• 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

Question 5

What is meant by negative feedback

Answer 5

A change in a system,

produces a second change

which reverses the first change.

Question 6

What does the control of a self-regulating system by -ve feedback mechanism involve

Answer 6

It involves a series of stages, in which an output from an effector reduces the stimulus and restores the system to its original level

Question 7

What is the series of stages in which the Negative feedback works

Answer 7

1. The setpoint is the norm at which the system operates
2. A receptor detects the level of the factor and its deviation from the setpoint.
3. The receptor sends instructions to a controller
4. The controller communicates 1 or >1 effectors.
5. The factor returns to normal as the effectors reduce the level.
6. The receptor sends a signal to the controller once the factor has reached the normal to stop the effectors.

Question 8

What is the first step of the negative feedback cycle

Answer 8

The set point for a factor is the norm at which the system operates

Question 9

what is the second step of the negative feedback cycle

Answer 9

A receptor detects the level of the factor and its deviation from the set point

Question 10

What is the third step of the negative feedback cycle

Answer 10

The receptor sends instructions to a co-coordinator or controller

Question 11

What is the 4th step of the negative feedback cycle

Answer 11

4/the co-coordinator communicates with one or more effectors e.g. muscles or glands

Question 12

what is the 5th and final step of the negative feedback cycle

Answer 12

the factor returns to normal,

This is identified by the receptor

and information is fed back to the effectors,

which stop making the correction

Question 13

What are 2 examples of negative feedback cycles

Answer 13

1. Glucose concentration in the plasma
2. Core temperature of the body

Question 14

What happens if the glucose concentration in the plasma increases above the set point

Answer 14

insulin is secreted.

Reduces the glucose concentration by converting it into glycogen

increasing the rate at which it is respired hence reducing the concentration

Question 15

What happens if the glucose concentration in the plasma decrease below the set point

Answer 15

Glucagon is secreated resulting in glycogen being converted into glucose which increases the glucose concentration

Question 16

What happens if the body’s core temperature falls below the set point

Answer 16

Increased respiration generates heat

constriction of superficial blood vessels allows the body to retain it,

hence increasing core body temperature

Question 17

What happens if the body’s core temperature rises above the set point

Answer 17

Superficial blood vessels dilate,

heat radiates from the body reducing its temperature

Question 18

What is a positive feedback mechanism in the body and how does it work

Answer 18

If a factor moves from a set point, a positive feedback mechanism increases the movement already made from the set point, further.

Question 19

What are two examples of positive feedback

Answer 19

1. Oxytocin
2. Clotting factors

Question 20

Why is Oxytocin a positive feedback mechanism?

Answer 20

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.

Question 21

How does the clotting mechanism use positive feedback

Answer 21

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.