Homeostasis Flashcards
(71 cards)
1
Q
Define Homeostasis
A
Using control systems to maintain a stable internal environment
2
Q
Why is it vital to keep your internal environment stable?
A
For cells to function normally and to stop them being damaged
3
Q
What happens when the body temperature is too high?
A
- Enzymes denature
- Vibrate too much, breaks the H bonds that hold the 3D shape
- Metabolic reaction are less efficient
4
Q
What happens when the body temperature is too low?
A
- Enzyme activity is reduced
- Slows down rate of metabolic reaction
5
Q
What is the optimum temperature for the highest rate of enzyme activity?
A
37oC
6
Q
What happens when the blood pH is too high or too low?
A
- Enzymes denature
- H bonds holding 3D shape are broken
- Shape of active site changes and no longer work as catalyst
- Metabolic reactions are less efficient
7
Q
What is the optimum pH for the highest rate of enzyme activity?
A
pH 7
8
Q
What happens when the blood glucose concentration is too high?
A
- Water potential of blood is reduced
- Water leaves cell into blood via osmosis
- Cells shrivel up and die
9
Q
What happens when the blood glucose concentration is too low?
A
- Cells unable to carry out normal activities
- Not enough glucose for respiration to provide energy
10
Q
What does the homeostatic system involve?
A
- Recepors
- Communication system
- Effector
11
Q
What does the receptor do?
A
Detect when levels are too high or too low
12
Q
Which mechanism restores the level back to normal?
A
Negative feedback mechanism
13
Q
Negative feeback works…
A
W/in certain limits- change too big, effector may not be able to counteract it
14
Q
Homeostasis involves ____ negative feedback mechanism
A
Multiple
15
Q
What does having multiple negative feedback mechanism mean?
A
- Can actively inc or dec level so it returns to normal
- More control
16
Q
What happens when you only have one negative feedback mechanism?
A
- Can only actively change level in 1 direction
- Slower response
- Less control
17
Q
Positive feedback ___ change from normal level
A
Amplify
18
Q
How does effectors respond in positive feedback mechanisms?
A
Further increase level away from normal level
19
Q
When is positive feedback useful?
A
- Rapidy activate something eg. Blood clot
- Homeostatic system breaks down eg. Hypothermia
20
Q
Is positive feedback involved in homeostasis? Why?
A
- No
- Doesn’t keep internal env stable
21
Q
The concentration of glucose in the blood is usually around…
A
90 mg per 100cm3
22
Q
When does glucose conc increase?
A
After eating food containing carbs
23
Q
When does glucose conc fall?
A
After exercise, glucose used for respiration to release energy
24
Q
Which 2 hormones control blood glucose conc?
A
- Insulin
- Glucagon
25
Where are insulin and glucagon secreted from?
* Cluster of cells in pancreas called **Islets of Langerhans**
* **Beta cells** secrete **insulin**
* **Alpha cells** secrete **glucagon**
26
Outline how insulin lowers blood glucose conc when it's too high
* Binds to **receptor** on cell membrane of **liver cells** and **muscle cel**l, **inc permeability** of muscle cell membrane to glucose, cells **take up more glucose**- involves **inc** no. **channel proteins**
* **Activates enzymes** that convert **glucose to glycogen**, cells able to store glycogen as **energy source** (**glycogenesis**)
* **Inc** rate of **respiration** of glucose
27
Outline how glucagon inc blood glucose conc when it's too low
* Binds to **receptors** on cell membrane of **liver cells**
* **Activates enzymes** in liver cells that **break down glycogen** to glucose (**glycogenolysis**)
* **Activates enzymes** involved in formation of glucose from **glycerol** + **aa** (non-carbs = **gluconeogenesis**)
* **Dec** rate of **respiration** of glucose
28
Outline what happens when the blood glucose conc falls
* **Pancrease** detects **too low**
* **A- se****crete glucagon, b- stop screting insulin**
* **Glucagon** binds to **liver cell**
* **Glycogenolysis activated**
* **Gluconeogenesis activated**
* Cells **respire less glucose**
* Cells **release glucose** to blood
29
Outline what happens when the blood glucose conc rise
* **Pancrease** detects **too high**
* **A- stop secreting glucagon, b- secrete in**sulin
* **Insulin** binds to **muscle + liver cell**
* **Cells take up more glucose**
* **Glycogenesis activated**
* Cells **respire more glucose**
* **Less glucose** to blood
30
Outline how insulin makes glucose transporters available for facilitated diffusion
* **Skeletal + cardiac muscle cells** contain **channel protein** **GLUT4** - **glucose transporter**
* **Insulin** levels **low**, GLUT4 stored in **vesicles** in **cytoplasm**
* Insulin binds to **receptors** on cell surface membrane, **triggers movement** of GLUT4 to **membrane**
* **Glucose** can then be **transported** into cell **through** **GLUT4** **via. FD**
31
Which gland secretes adrenaline?
**Adrenal** gland
32
When is adrenaline secreted?
* **Low conc** of **glucose** in blood
* **Stressed**
* **Exercising**
33
Outline the function of adrenaline
* **Binds** to **receptors** in cell membrane of **liver cells**
* **Activates glycogenolysis**
* **Inhibits glycogenesis**
* **Activates glucagon secretion**
* **Inhibits insulin secretion**
* **More glucose** available for **muscles to respire**
34
Describe the second messenger model of adrenaline and glucagon
* **Adrenaline** and **glucagon** bind to **receptor**
* **Activate enzyme adenylate cyclase**
* **Converts ATP** to **chemical signal**- **second messenger**
* **Cyclic AMP**
* **Activates enzyme protein kinase A**
* Activates **cascade** breaking **glycogen to glucose**
35
Define diabetes mellitus
Condition where **blood glucose conc can't** be **controlled**
36
How is type 1 diabetes acquired?
* **Immune system attacks b cells** in islet of langerhans so **can't produce insulin**
* **Genetic predispositioning**
* **Triggered** by **viral infection**
37
Define hyperglycaemia
After eating, **glood glucose level rises** and **stays high**
38
How is type 1 diabetes treated?
* **Insulin therapy**:
* **Regular insulin injection**
* **Insulin pump** (continuous)
39
Define hypoglycaemia
Dangerous **drop** in **blood glucose level**
40
How do you avoid a sudden rise in glucose?
* **Eating regularly**
* **Control carbohydrate intake**
41
How is type 2 diabetes acquired?
* **Obesity**
* **More likely** with **family history**
* **Lack** of **exercise**
* **Age**
* **Poor diet**
42
Why does type 2 diabetes occur?
* **B cells dont** produce enough **insulin**
* **Body's cell don't respond** properly to insulin bc insulin **receptors don't work**, so cells **don't take up** enough **glucose**- high blood glucose conc
43
How is type 2 diabetes treated?
* **Eating healthy**
* **Balanced diet**
* **Losing weight**
* **Regular exercise**
* **Glucose-lowering medication** (if diet and exercise can control it)
* **Insulin injections**
44
How do health advisors respond to the inc in type 2 diabetes?
* Eat diet **low** in **fat, sugar** and **salt**
* **Regular exercise**
* **Lose weight**
* **Educate people**
* **Challenged food industry** to **reduce advertising junk food** and use **clearer labels**
45
How do food companies respond to the inc in type 2 diabetes?
* Use **sugar alternatives**
* **Reducing sugar, fat** and **salt** content
46
What is the normal conc of glucose in the urine?
What does it mean when the conc is higher?
* **0-0.8mM**
* Indicates **diabetes**
47
How is quantitative benedict's reagent different to normal benedict's reagent?
When **heated w/ glucose**, initial **blue colour** is **lost** but **brick** **red ppt isn't produced**
48
Which method do you use to determine the conc of glucose in urine?
**Colorimetry**
49
Higher the conc of glucose the more/less blue colour will be lost/produced, increasing/decreasing absorbance of solution
* More
* Lost
* Decreasing
50
Outline how to do a serial dilution?
* **5 test tubes** in racks
* Add **10cm3 of initial 4mM glucose sol** to **1st test tube** and **add 5cm3 of distilled water** to other **4** test tube
* Using **pipette**, draw **5cm3 of sol to second test tube** (half conc - 2mM)
* Repeat 3 times to create **1mM, 0.5mM** and **0.25mM**
51
Outline the method used to determine the conc of glucose in a uring sample
* Need **several glucose solutions** of **diff, known conc** (serial dilution)
* Need to make a **calibration curve**:
* Do q**uantitative benedict's test** on each solution (plus **water** as **control**)
* Use **colorimeter w/ red filter**
* Make calibration curve - **absorbance against glucose conc**
* Can test unknown sol
52
Outline the function of the kidneys
* **Excrete waste products**
* **Regulate water potential** of **blood**
53
Label a nephron
* **Afferent arteriole**
* **Glomerulus**
* **Efferent arteriole**
* **Proximal convoluted tubule**
* **Loop of Henle**
* **Distal convoluted tubule**
* **Collecting duct**
54
Where does selective reabsorption take place?
* **PCT**
* **Loop of henle**
* **DCT**
55
Where does ultrafiltration occur?
**Bowman's capsule**
56
Describe how ultrafiltration produces glomerular filtrate (5)
* **Hydrostatic pressure**
* **Small molecules**
* Pass through **basement membrane**
* **Protein too large** to pass
* Presence of **pores/podocytes**
57
Name 4 substances present in the glomerular filtrate
* **Urea**
* **aa**
* **Fatty acids**
* **Ions**
58
Outline how the proximal convoluted tubule are adapted for reabsorption
* **Infolding** inc SA
* **Microvilli** inc SA
* **Lots** of **mitochondria**
59
Describe the process of selective reabsorption
* **Useful filtrate** (glucose) are **reabsorbed** along PCT by **AT** and **FD**
* **Water enters blood** by osmosis bc water potential of blood is lower than filtrate
* **Filtrate** that **remains** is **urine**
60
What is urine made up of?
* **Water**
* **Dissolved salts**
* **Urea**
* **Hormones**
* **Excess vitamins**
61
What does urine not usually contain?
* **Proteins**- too big to be filtered out
* **Blood** **cells**- too big to be filtered out
* **Glucose**- actively reabsorbed
62
Give ways water is lost in the body?
* **Excretion**
* **Sweat**
* **Breathing**
63
Define osmoregulation
**Regulation** of the **water potential** of the **blood**
64
What happens when the water potential of the blood is too low (dehydrated)?
* **More water** is **reabsorbed** into the blood
* Via **osmosis**
* **Urine** is **more conc** so less water is lost during excretion
65
What happens when the water potential of the blood is too high?
* **Less water** is **reabsorbed** into the blood
* **Urine** is **dilute**, more water is lost during excretion
66
Where does the regulation of water potential mainly take place?
* **Loop of henle**
* **DCT**
* **Collecting duct**
67
Describe how the loop of henle maintains a sodium ion gradient
* **Ascending limb**, **Na+** pumped out into medulla using **AT**
* **AL impermeable** to **water** so water stays inside tubule, creates **low WP** in medulla
* **Water moves out** of **descending limb** into medulla via osmosis
* **Filtrate more conc**
* **Water in** **medulla** is **reabsorbed** into **blood** through **capillary network**
* Bottom of **AL Na+ diffuse out medulla**, **further lowering WP**
68
Describe what happens in the collecting duct
* **High ion conc** in **medulla lowers wp**
* Causes **water** to **move out collecting duct** via **osmosis**
* Water in medulla is **reabsored** into **blood** via **capillary network**
69
Which cells moniter the water content of blood?
**Osmoreceptors** in the **hypothalmus**
70
When is ADH (antidiuretic hormone) secreted?
**Water potential of blood inc**
71
Explain the role of ADH in the production of concentrated urine
* When **water potential** of **blood** is **too low**, **osmoreceptors** in **hypothalamus** detect it
* **Post pituitary gland secretes more ADH**
* ADH **increases permeability** in **DCT** and **collecting duct**
* **More water reabsorbed** into **blood** via **osmosis**
