Topic 6C: Homeostasis Flashcards
What is Homeostasis?
Maintaining a constant/stable internal environment.
-Changes in your external environment can affect your internal environment.
What 3 main things should be maintained in the body?
- Temperature
- Blood pH
- Blood Glucose Conc
If body temp is too high…
-enzymes denature because
-they vibrate too much
-breaks hydrogen bond
-alters tertiary structure
-changes shape of active site
-No longer works as a catalyst
-METABOLIC REACTION less efficient
-
If body temp too low…
-Low enzyme activity
slow metabolic reactions
What is the optimum body temperature?
37 degrees C
If the blood pH is too low/too high…
- enzymes denature because
- breaks hydrogen bond
- alters tertiary structure
- changes shape of active site
- No longer works as a catalyst
- METABOLIC REACTION less efficient
What is the optimum pH?
pH7
If blood glucose conc is too high…
- lowers water potential
- water molecules diffuse out of cell and into blood
- by osmosis
- cells shrivel up and die
If blood glucose conc is too low…
cells are unable to carry out normal activity because not enough glucose is the cells for respiration to provide energy.
What is Negative Feedback Mechanism?
A response when the homeostatic system detects change.
Receptors, a Communication system and effector are in…
the homeostatic system
What do receptors do in the homeostatic system?
- detects if levels are too high/too low
- sends a signal to the nervous system or the hormonal system
Name two types of communication system?
Nervous and Hormonal
What do effectors do in the homeostatic system?
respond to counteract change to bring levels back to normal.
If the change in the internal environment is too big…
- effectors can not counteract the change
- no negative feeback
Multiple negative feebacks gives…
a faster response and more control
What is Positive Feedback Mechanism?
amplify a change from the normal level.
What do effectors do in a positive feedback mechanism?
Further increases the level away from normal
Examples of positive feedback?
- blood clots after injury
- hypothermia (low body temperature)
What is the concentration of glucose in the blood normally?
90mg per 100cm3
When does blood glucose concentration increase?
When we eat food containing carbohydrates.
When does blood glucose concentration decrease?
-after exercise because more glucose is used for respiration to release energy.
Name three hormones that control the blood glucose concentration.
- Insulin
- Glucagon
- Adrenaline
Which hormones do the hormonal system control
Insulin and Glucagon
What is a hormone?
A chemical messenger that travels in the blood to their target cells (effectors)
Where are insulin and glucagon secreted?
cluster of cells in the pancreas called the islet of Langerhans
What types of cells are in the islet of Langerhans?
Beta cells which secrete insulin
Alpha cells which secret glucagon
What does insulin do?
-lowers the blood glucose concentration in blood when it is too high.
How does insulin lower blood glucose concentration?
-insulin bind to specific receptors on liver and muscle cells. This…
1) increases the permeability of cell membranes to glucose. This involves increases channel proteins too.
2) activates enzymes in liver and muscle cells to convert glucose into glycogen (glycogenesis)
3 increases the rate of respiration
What does glucagon do?
-raises the blood glucose concentration in blood when it is too low.
How does glucagon lower blood glucose concentration?
- Glucagon bind to specific receptors on liver cells. This…
1) activates enzymes in liver to break down glycogen to glucose (glycogenolysis)
2) activates enzymes that make glucose from glycerol and amino acids. (glyconeogenesis)
3) decreases rates of respiration)
What is Glycogenesis?
Making glycogen from glucose as a energy storage.
What is Glycogenolysis?
Break down of glycogen to glucose
What is Glyconeogenisis?
Forming glucose from amino acids and glycerol.(non-carbohydrates)
Name a channel protein/glucose transporter?
GLUT4
Which cells contain GLUT4?
Cardiac and Skeletal muscle cells
Where are GLUT4 stored in cells?
Vesicles in the cytoplasm
What triggers the movement of GLUT4 from the cytoplasm to the cell membrane?
The binding of insulin and receptors on the cell-surface membrane.
How is the glucose transported through GLUT4?
Faciliated Diffusion
Where is adrenaline secreted from?
Adrenal glands
When is adrenaline secreted from?
- When there is a low concentration of glucose in the blood.
- stress
- after excercise
What does adrenaline do?
- activates glygenolysis
- inhibits gylcogenesis
- activates glucagon secretion
- inhibits insulin secretion
How does adrenaline and glucagon activate glycogenolysis inside a cell?
- Adrenaline and Glucagon bind to receptors that have a complementary shape to them. (on cell membrane)
- activates an enzyme called adenylate cyclase
- Adenylate cyclase converts ATP into a chemical signal called cyclic AMP
- This is a secondary messenger
- cAMP activates protein kinase A
- this activates a cascade of glycogenolysis
Adrenaline and Glucagon can only work via…
a secondary messenger
