biology m3 homeostasis
TRANSCRIPT
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
HOMEOSTASIS
Module 3 Unit 8 Lesson 3
1
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
OBJECTIVES
After reviewing the slides and doing the activities you will be able to:1.explain the term ‘homeostasis’ and its importance.2.outline the regulatory mechanisms involved in homeostasis.3. give examples of homeostasis in mammals, using a diagram to explain each.
2
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
HOMEOSTASIS EXPLAINED
What is it? Homeostasis is the maintenance of a constant
or stable internal environment, regardless of internal/external changes.
Why do it? Homeostasis is important to provide a suitably
stable environment for metabolic activity in cells.
When is it done in humans? Homeostasis involves regulating and
maintaining such things as salt, water, glucose, Carbon dioxide and body temperature at a ‘normal’ level.
3
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
HOMEOSTASIS EXPLAINED - EXAMPLES
The thickening of an animal’s fur in winter.
The darkening or “tanning” of skin in sunlight.
Regulation of body temperature. Regulating the levels of Carbon
dioxide. Regulating the water
concentration in the body or osmoregulation.
The production of more red blood cells at high altitude.
4
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
HOW IS HOMEOSTASIS ACHIEVED?
Homeostasis can be controlled/regulated either by a process known as a ‘negative feedback mechanism’ or by a ‘positive feedback mechanism’.
Within the human body, most homeostatic activities are regulated by a negative feedback mechanism.
5
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
A negative feedback mechanism is any process which detects a change from the normal or ‘set point’ in the internal environment, that brings a response which reverses that change so as to restore normal conditions.
6
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Negative Feedback Mechanism
Every negative feedback mechanism has the following inter-related components:
A detector or sensor which identifies the
change (stimulus)
An effector which corrects
the change
An integrator or a controller which regulates the
sensor and effector
7
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Negative Feedback Loop
Effectors
EffectorsReceptors
Factor Norm
Message
Corrective Response
Corrective Response
Factor Decrease
Factor Norm
Message
Receptors
Factor Increase
No change in factor
8
Discuss this flow diagram with your teacher.
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Components of a negative feedback mechanism
In humans, detectors/sensors are sense organs and sensory receptor cells found throughout the body.
Effectors are various muscles and glands that carry out corrective measures/respond.
The integrator or controller is the brain. Quite often it is the master control endocrine gland in the brain (Pituitary gland) that is the controller.
9
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
REGULATION OF GLUCOSE
Glucose is a respiratory substrate. Excess glucose is normally stored in
the liver as glycogen or ‘animal starch’.
If the blood/cellular glucose level gets too low, the energy level of the cells will be reduced.
If the level gets too high, the osmotic balance of the cells will be affected.
10
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Regulation of Glucose
1. If the level of glucose rises too much, special receptors (called hepatocytes) detect this.
A message is sent to the pancreas which secretes insulin. This insulin converts glucose to glycogen, which is stored in the liver, and also in skeletal muscles, until required.
Follow that sequence in the next slide by clicking the ANIMATE button.
11
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
If there is too much glucose in the blood, Insulin converts some of it to glycogen
Glycogen
Insulin
Glucose in the blood
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ANIMATE
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Regulation of Glucose
2. If the level of blood glucose falls too low, special receptors (especially hepatocytes) detect this. A message is sent to the pancreas which secretes glucagon. This glucagon converts glycogen stored in the liver/body muscles to glucose, and it is released to the blood/cells.
What are the sensors, effectors and integrators in this feedback mechanism?
13
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose.
Glycogen
Glucagon
Glucose in the blood
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ANIMATE
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Now, let’s look at those two situations together in one flow chart!
On the next slide, follow what happens starting from the stimulus on the left when food with carbohydrates is eaten.
Did you notice the opposite effects of insulin and glucagon?
15
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Feedback loops for homeostatic control of blood sugar
http://www.biologymad.com/resources/A2%20Homeostasis.pdf
16
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
A simple feedback loop for you to use!
Here is a simple diagram that you can learn how to draw !Try it now.
17
http://www.worldofteaching.com/powerpoints/biology/Blood%20sugar.ppt#257,7,Slide7
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Talk with your teacher about what is happening in this graph.
18
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
REGULATION OF CARBON DIOXIDE
The level of Carbon dioxide in the blood will be increased if there is much physical activity and increased cellular respiration.
If allowed to accumulate, CO2 will lower the pH of the cells.
If levels fall too low, CO2 will diffuse down the concentration gradient across the alveoli into the blood.
A rise is detected by chemoreceptors in blood vessels, namely the Carotid and Aortic vessels.
19
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Regulation of Carbon Dioxide
These chemoreceptors send messages to the Medulla oblongata of the brain which signals the breathing rate to increase.
If the level falls, probably due to inactivity, the same chemoreceptors in the blood vessels detect this.
Messages are sent to the Medulla oblongata and the breathing rate decreases.
20
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
HOMEOSTATIC CONTROL OF BODY TEMPERATURE
Talk with your teacher about the structure of the human skin shown in 3D section on the next two slides.
In the first diagram, note the capillary networks just below the epidermis, sweat glands, sweat pores and hair muscles.
In the second diagram of the skin, note the various types of receptors including those for sensing heat and cold.
21
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Structure of the Human Skin
22
Note the capillary networks just below the epidermis, sweat glands, sweat pores and hair muscles.
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Section through Human Skin, showing receptors
23
http://universe-review.ca/I10-13-senses.jpg
Note the various types of receptors including those for sensing heat and cold.
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Homeostatic Control of Body Temperature
In humans, body temperature is controlled by the thermoregulatory centre in the hypothalamus of the brain. It receives input from: (1) receptors in the hypothalamus itself which monitors the temperature of the blood as it passes through the brain and (2) from skin receptors that monitor the external temperature. Both sets of information are needed so that the body can make appropriate adjustments.
The thermoregulatory centre sends impulses to several different effectors (e.g. muscles in blood vessels, hair muscles) to adjust body temperature.
24
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Feedback loops for temperature control
25
http://www.biologymad.com/resources/A2%20Homeostasis.pdf
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Regulation of body temperature
Body temperature increases due to internal cellular activity. External temperatures also affect body temperature.
Body temperature falls due to low cellular activity and a fall in external temperature.
When the body temperatures falls, thermoreceptors in the skin detect this.
26
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Regulation of body temperature
A message is sent to the Hypothalamus in the brain which implements several mechanisms to increase temperature.
These mechanisms include: vasoconstriction, increased fat respiration, contraction of hair erector muscles.
The next two slides show how skin capillary loops contract and dilate during temperature regulatory processes.
Why would those changes occur?27
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
When body temperature rises…
When body temperature rises:
Blood flow to the surface is increased.
(a) is closed and (b) and (c) arterioles are open. This is vasodilation.
Blood flows closer to the skin surface. There is a larger surface area for the heat to escape through the skin surface.
More heat is lost to the external environment.
Body temperature is reduced.
28
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
When body temperature falls …
When body temperature falls:
Blood flow to the surface via arterioles is reduced.
(a) is dilated but (b) and (c) arterioles are vasoconstricted.
Blood flow to the surface is reduced.
Less heat is lost to the external environment by radiation.
Body heat is retained. 29
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Sweating when hot
In the next slide, notice that the diagrams show the sweat glands, and you can see how the openings (pores) come right up to the surface.
The sweat can easily escape to the surface of the skin through the pores.
When sweat evaporates (changing from liquid to gas), the process needs heat energy to do this; so, heat is removed from the sweat to do so. The result? Your body gets cooler!
The hairs are moved by the action of the muscle, and lie flat against the skin surface.
30
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
Notice that the diagrams show the sweat glands, and you can see how the openings (pores) come right up to the surface.
31
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
http://scienceaid.co.uk/biology/humans/homeostasis.html
32
HOMEOSTASIS EXPLAINED
HOW IS HOMEOSTASIS
ACHIEVED?
REGULATION OF
GLUCOSE
REGUALTION OF CARBON
DIOXIDE
REGULATION OF
TEMPERATURE
X
OBJECTIVES
SUMMARY
Homeostasis is an organism’s ability to regulate its internal environment, keeping cellular processes and contents at a ‘set point’ which thereby enables the organism to obtain and use resources, feed, grow, reproduce, excrete waste and generally maintain stable internal conditions while living in a constantly changing external environment. The variousreceptors and effectors within the organism’s body enable it to use negative and positive feedback mechanisms for homeostasis.
33