C12 - 1.0 Homeostasis COPY Flashcards Preview

Biology Year 2 > C12 - 1.0 Homeostasis COPY > Flashcards

Flashcards in C12 - 1.0 Homeostasis COPY Deck (23):
1

What is Homeostasis?

The maintenance of a constant internal enviroment

2

What is an internal environment?

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

It is one where... tissue fluids... bathe cells, supply nutrients and remove waste.

They also help to maintain PH, glucose levels, core temperature and solute potential.

 

3

What is the set point

The set point is the baseline which allows optimal and constant cell function inside the body

 

e.g.

Normal Body temperature 36.5 to 37.5 degrees centigrade

Normal PH of blood is between 7.35 and 7.45

4

What is Homeostasis - Long answer

  • Homeostasis is
  • The maintenance of a constant internal environment
  • Where tissue fluids...
    • Bathe cells,
    • supply nutrients
    • remove waste
  • and help to maintain...
    • PH
    • Glucose levels 
    • Core temperature
    • Solute potential.
  • At the set point. e.g. Body temperature 36.5-37.6 degrees

5

What is the benefit of homeostais?

Or...

What is the benefit of maintining a contstant 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
  • If for example the PH of blood rises above the set point of 7.3-7.45, then a negative feedback mechanism reverses this change back to the set point.

6

What is meant by negative feedback

A change in a system,

produces a second change

which reverses the first change.

 

Longer answer Jamie

If there is a change in the internal environment, e.g. Body temperature rises above its set point...36.5-37.6 degrees centigrade.

This change is later reversed by a negative feedback mechanism, returning the temperature to its normal set point.

 

7

What is an example of a negative feedback mechanism

  • The way the endocrine system controls haeomostatic responses via hormone activity

8

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 e.g. gland or muscle, reduces the stimulus and resotres the system to its original level e.g. the set point.

9

What is the series of stages in which the Negative feed back works

  1. The set point for a factor is the norm at which the system operates
    • e.g. Body temperature 36.5-37.6 degrees
    • e.g. PH of blood 7.35-7.45 
  2. A receptor detects the level of the factor and its deviation from the set point
  3. The receptor sends instructions to a co-coordinator or controller
  4. The co-coordinator communicates with one or more effectors e.g. muscles/glands
  5. The factor returns to normal
  6. The receptor recognises this and the info is fed back to the effectors which stop making the correction.

10

What is the first step of the negative feedback cycle

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

e.g. The PH of blood is 7.35-7.45

11

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

12

What is the third step of the negative feedback cycle

The receptor sends instructions to a co-coordinator or controller

13

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

14

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

15

What are 2 examples of negative feedback cycles

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

16

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

insulin is secreated. Reduces the glucose concentration by converting it into glycogen increasing the rate at which it is respired hence reducing the concentration

17

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

18

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

Increased respiration generates heat and...constriction of superficial blood vessels allows the body to retain it, hence increasing core body temperature

19

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

20

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.

21

What are two examples of positive feedback

  1. Oxytocin
  2. Clotting factors

 

22

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.

23

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.