1 2 Think about… 18.1The concept of homeostasis 18.2Regulation of blood glucose level Recall...
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Think about…
18.1 The concept of homeostasis
18.2 Regulation of blood glucose level
Recall ‘Think about…’
Summary concept map
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18.1 The concept of homeostasis
Do you know what homeostasis is?
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• ability of the body to maintain a stable internal environment
What is homeostasis?18.1 The concept of homeostasis
• important for body to function properly
- composition of blood and tissue fluid
- body temperature
- blood pressure
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What is homeostasis?18.1 The concept of homeostasis
For example:
Our body is exposed to changes in the external environment, e.g. air temperature
homeostasis
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What is homeostasis?18.1 The concept of homeostasis
For example:
The condition of blood and tissue fluid is kept constant for proper functions of cells
capillaryblood
body cell bathed in tissue fluid
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Parameters of the internal environment to be kept stable
18.1 The concept of homeostasis
What parameters must be kept
constant in our body?
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affects
1 Water content in blood18.1 The concept of homeostasis
water content in blood
water potential of tissue fluid
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1 Water content in blood18.1 The concept of homeostasis
If water potential of tissue fluid is different from that of the cells, water will …
enter the cells
leave the cells
or
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1 Water content in blood18.1 The concept of homeostasis
If too much water is gained …
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1 Water content in blood18.1 The concept of homeostasis
If too much water is lost …
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1 Water content in blood18.1 The concept of homeostasis
If too much water is lost …cells cannot function properly and may even die
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1 Water content in blood18.1 The concept of homeostasis
• regulated by kidneys ( 腎 )
kidneys ureters
urinary bladder urethra
mammalian urinary system
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2 Glucose level in blood18.1 The concept of homeostasis
• for respiration in cells
glucose + O2
energy + CO2 + water
- level in blood is kept steady to ensure a sufficient supply
- as it is water soluble, any change in level affects water potential of the tissue fluid
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2 Glucose level in blood18.1 The concept of homeostasis
In humans,
• normal range is 90–100 mg/cm3
• maintained by
liver pancreas
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3 Gas content in blood18.1 The concept of homeostasis
• in respiration
glucose + O2
energy + CO2 + water
content in blood is kept steady to ensure a sufficient supply
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3 Gas content in blood18.1 The concept of homeostasis
• in respiration
glucose + O2
energy + CO2 + water
dissolves in blood
affects pH of blood and tissue fluid
affects enzyme activity
too much / too little
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3 Gas content in blood18.1 The concept of homeostasis
• regulated by
breathing heartbeat
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4 Body temperature18.1 The concept of homeostasis
• normal range is 36.5–37C • kept steady for enzymes to function
properly• regulated by
skin
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4 Body temperature18.1 The concept of homeostasis
What are the effects of failing to regulate body temperature?
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4 Body temperature18.1 The concept of homeostasis
C4442
>37.5
33
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deathCNS breakdownfever
loss of consciousness
muscle failure
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Mechanism of homeostasis18.1 The concept of homeostasis
• by negative feedback mechanism (負反饋機制 )
What does that mean?
Let me explain with an example.
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18.1 The concept of homeostasis
When the room temperature (RT) is higher than the set temperature (S) …
Negative feedback mechanism
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18.1 The concept of homeostasis
thermostat turns compressor on, cooling the air back to set temperature
RT > S
Negative feedback mechanism
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18.1 The concept of homeostasis
When the room temperature (RT) is lower than the set temperature (S) …
Negative feedback mechanism
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18.1 The concept of homeostasis
thermostat turns compressor off, allowing room temperature to increase
RT < S
Negative feedback mechanism
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18.1 The concept of homeostasis
Three components:Receptor Detects changes in the level
of the parameterControl centre
Processes information from receptor and coordinates different organs
Negative feedback mechanism
nervous system or endocrine system
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18.1 The concept of homeostasis
Three components:Receptor Detects changes in the level
of the parameterControl centre
Processes information from receptor and coordinates different organs
Effector Produces a response opposite to the original change
Negative feedback mechanism
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18.1 The concept of homeostasis
normal level of parameter
When level of parameter is higher than normal,
receptorcontrol centre
effector
response to decrease the level
back to normal
Negative feedback mechanism
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18.1 The concept of homeostasis
When level of parameter is lower than normal,
receptorcontrol centre
effector
Negative feedback mechanismresponse to
increase the level back to normal
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1 is the ability of the body to maintain a stable internal environment.
Homeostasis
18.1 The concept of homeostasis
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2 Homeostasis is important for the of organisms because it provides a stable internal environment for cells to function.
survival
18.1 The concept of homeostasis
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18.1 The concept of homeostasis
ParameterImportance of regulating
the parameter
Water content in blood
• To keep a stable water potential in cells so that they can carry out metabolic activities properly
waterpotential
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18.1 The concept of homeostasis
ParameterImportance of regulating
the parameter
Glucose content in blood
• To provide sufficient glucose to cells for
• To keep a stable water potential in blood
respiration
potentialwater
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18.1 The concept of homeostasis
ParameterImportance of regulating
the parameter
Gas content in blood
• To provide sufficient oxygen to cells for respiration
• To maintain a stable for enzymes to work
oxygen
pH
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18.1 The concept of homeostasis
ParameterImportance of regulating
the parameter
Body temperature
• To maintain a stable temperature that is optimal for to work
enzymes
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4 The system and the system coordinate different organs to achieve homeostasis.
nervousendocrine
18.1 The concept of homeostasis
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5 results in responses that have opposite effects to the changes in the parameter, so that the level of the parameter can be restored to normal.
Negative feedback mechanism
18.1 The concept of homeostasis
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18.2 Regulation of blood glucose level
How do the liver and pancreas regulate our blood glucose level?
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Roles of liver and pancreas18.2 Regulation of blood glucose level
• pancreas secretes hormones
insulin glucagon
both act on liver but with opposite effects
• they work together
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body cells
Roles of liver and pancreas18.2 Regulation of blood glucose level
Insulin decreases blood glucose level
excess glucose
liver cellsglycogen
stored in
muscles liver
Body cells take in more glucose
glucose CO2 + water
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liver cells
Roles of liver and pancreas18.2 Regulation of blood glucose level
Glucagon increases blood glucose level
stored glycogen
glucose
Let’s see how blood glucose level is
regulated by negative feedback mechanism.
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Roles of liver and pancreas18.2 Regulation of blood glucose level
normal blood glucose level
higher than
normal
pancreas secretes more insulin and
less glucagon
liver cells and body
cells
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Roles of liver and pancreas18.2 Regulation of blood glucose level
Decrease level by:1 converting more glucose to
glycogen in liver cells2 increasing glucose uptake and
oxidation by body cells
higher than
normal
pancreas secretes more insulin and
less glucagon
liver cells and body
cells
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Roles of liver and pancreas18.2 Regulation of blood glucose level
lower than
normal
pancreas secretes more glucagon and less insulin
Increase level by:converting stored glycogen to glucose
liver cells
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Failing to regulate blood glucose level
18.2 Regulation of blood glucose level
What will happen if blood glucose level is too high?
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Failing to regulate blood glucose level
18.2 Regulation of blood glucose level
diabetes mellitus
blood glucose level too high
water leaves cells by osmosis
glucose passes out in urine
normal metabolism affected
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Failing to regulate blood glucose level
18.2 Regulation of blood glucose level
diabetes mellitus
it results when the pancreas fails to produce or does not
produce enough insulin
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18.2 Regulation of blood glucose level
blood glucose level (mg/100cm3)
100
200
150
time (hrs)1 2 3
normal
glucose intake
healthy person
level returns to normal within a short time
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18.2 Regulation of blood glucose level
blood glucose level (mg/100cm3)
100
200
150
time (hrs)1 2 3
normal
glucose intake
diabetic
level remains high and then drops very slowly
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18.2 Regulation of blood glucose level
blood glucose level (mg/100cm3)
100
200
150
time (hrs)1 2 3
normal
glucose intake
diabetic
the drop is due to the loss of glucose in urine
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18.2 Regulation of blood glucose level
glucose level in urine
1 2 3glucose intake
time (hrs)
diabetic
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18.2 Regulation of blood glucose level
Diabetics need insulin injections
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18.2 Regulation of blood glucose level
blood glucose level (mg/100cm3)
100
200
150
time (hrs)1 2 3
normal
glucose intake
injection of insulin
level drops quickly
diabetic
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18.2 Regulation of blood glucose level
Failing to regulate blood glucose level
How about if the blood glucose level is too low?
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18.2 Regulation of blood glucose level
Failing to regulate blood glucose level
person becomes unconscious
blood glucose level too low
insufficient supply of glucose for respiration
neurones cannot function
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Pancreatic hormones regulate blood glucose levels
– The pancreas secretes two hormones• Insulin
– Signals cells to use and store glucose
• Glucagon– Signals cells to release stored
glucose into the blood
Pancreatic hormonesPancreatic hormones
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http://www.sunyniagara.cc.ny.us/val/pancreas2.jpg
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http://www.cytochemistry.net/microanatomy/Endocrines/pancreas2.jpg
The insulin producing cells are called cells and make up about 70% of the islet cells.
The glucagon producing cells are called cells and make up about 15 - 20% of the islet cells.
The islets are composed of three cell types: alpha cells, beta cells, and delta cells. These cells cannot be readily distinguished without special stains.
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SECRETORY SECRETORY ROLEROLE
CELL CHARACTERISTICSCELL CHARACTERISTICS
cells of islets cells of islets of Langerhansof Langerhans
Glucagon 15 - 20% of the islet cells; generally more peripherally located in the islet; more uniform in size; cytoplasm appears to be more densely packed than the cells
cells of islets cells of islets of Langerhansof Langerhans
Insulin 70% of the islet cells; generally more centrally located in the islet
Acinus cellsAcinus cells Digestive enzymes
Usually oriented in a circular pattern
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Body
cells
take up moreglucose
Insulin
Blood glucose leveldeclines to a set point;stimulus for insulinrelease diminishes
Stimulus:
Declining bloodglucose level(e.g., afterskipping a meal)
Alphacells ofpancreas stimulatedto release glucagoninto the blood
Glucagon
Liverbreaks downglycogen andreleases glucoseto the blood
Blood glucose levelrises to set point;stimulus for glucagonrelease diminishes
Stimulus:
Rising blood glucoselevel (e.g., after eatinga carbohydrate-richmeal)
Homeostasis: Normal blood glucose level
(about 90 mg/100mL)
Beta cells
of pancreas stimulatedto release insulin intothe blood Liver takes
up glucoseand stores it asglycogen
High blood
glucose level
GlucoseGlucose
balancebalance
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– Diabetes can be detected• By a test called a glucose tolerance test
Blo
od
glu
cose
(m
g/1
00
mL
)
0
50
100
150
200
250
300
350
400
12
1 2 3 4 5
Diabetic
Normal
0Hours after glucose ingestion
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Diabetes is a common endocrine disorder
– Diabetes mellitus• Results from a lack of insulin or a failure of cells to
respond to it (absolute or relative inadequacy)
– 2 types of diabetes• Type I (insulin-dependent)
– Autoimmune disease
– Beta cells destroyed, no insulin made
• Type II – Body cells fail to respond to insulin
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Diabetes type I and type IIDiabetes type I and type IIType I - autoimmune disorder (destroys ability to produce insulin)
Type II - due to aging, lifestyle, heredity and other lifestyle (diet) factors decreased responsiveness by cells of target organs to insulin
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Complications Complications related to related to DiabetesDiabetes
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Insulin PumpInsulin Pump
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People with diabetes mellitus (糖尿病 ) need to check blood glucose level and
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People with diabetes mellitus (糖尿病 ) need to receive insulin injections
several times a day…
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This greatly affects our daily activities.
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A new device consists of a glucose sensor and an insulin pump
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The sensor checks the blood glucose level
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A suitable amount of insulin is released automatically into the body
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1
18.2 Regulation of blood glucose level
normal blood glucose level
high blood glucose level
more and less secreted
blood glucose level falls
1 more is converted to
in liver2 more is oxidized by body cells
insulinglucagon
glucose
glycogen
glucose
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stored is converted to in liver
1
18.2 Regulation of blood glucose level
normal blood glucose level
low blood glucose level
blood glucose level rises
more and less secretedinsulin
glucagon
glucose
glycogen
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2a If the blood glucose level is too high, cells water by osmosis and their metabolic activities will be affected. Glucose may be lost in .urine
lose
18.2 Regulation of blood glucose level
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2bIf the blood glucose level is too low, cells cannot obtain enough energy for metabolism and they may die.energy
18.2 Regulation of blood glucose level
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What is the relationship between1When the pancreas fails to secrete enough insulin, a person will have diabetes mellitus.
diabetes mellitus and insulin?
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Why do people with diabetes mellitus 2
Since the blood glucose level varies with body activities, it is necessary to check the level and inject suitable amounts of insulin regularly.
need to check their blood glucose levels and receive insulin injections regularly?
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What other modern advances in 3
Other than insulin injections, diabetes mellitus may be controlled or cured by pancreas transplant.
science and technology may help control or cure diabetes mellitus?
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is brought about by
through
nervous system
Homeostasis
endocrine system
negative feedback mechanism
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parameters include
is the maintenance of a
stable internal environment
Homeostasis
water content in blood
glucose level in blood
gas content in blood
body temperature
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is regulated by
act on
pancreas
secreted by
glucagon
glucose level in blood
insulin
liver body cells