Homeostasis

Question 1

What is homeostasis?

Answer 1

Maintaining a constant internal environment

Question 2

What does homeostasis control?

Answer 2

Water levels (osmoregulation)
Tissue fluid
O2 levels
Blood sugar levels
Composition of blood
Temperature (thermoregulation)

Question 3

Explain why the control + maintenance of internal conditions are important for an organism

Answer 3

Temperature = stops proteins denaturing = enzymes needed for reactions = eg. respiration
In/decrease rate of diffusion
Sugar levels = water potential = lysis of cells
Respiration
O2 levels = respiration

Question 4

What is thermoregulation?

Answer 4

The control of internal body temperature

Question 5

What is an ectotherm?

Answer 5

Maintain a proportion of their heat from outside sources

Question 6

What is an example of an ectotherm?

Answer 6

Lizard + snakes

Question 7

What is an endotherm?

Answer 7

Derive heat from source of metabolic activities inside their body

Question 8

What is an example of an exotherm?

Answer 8

Mammals + birds

Question 9

What is the hypothalamus?

Answer 9

Control unit for most responses

Question 10

What does the hypothalamus link?

Answer 10

N.S to endocrine system via pituitary gland

Question 11

What is the response to a decrease in temperature?

Answer 11

Vasoconstriction of arterioles
Shivering
Piloerection
+ metabolism

Question 12

What is the response to an increase in temperature?

Answer 12

Vasodilation
Sweating
Pilorelaxation
- metabolism

Question 13

What is a negative feedback loop?

Answer 13

Initiating corrective mechanisms whenever the internal environment deviates from its normal or acceptable levels

Question 14

What is a positive feedback loop?

Answer 14

Deviation from normal conditions is amplified, leading to further deviation

Question 15

What are examples of negative feedback mechanisms in the body?

Answer 15

Temperature control
Blood sugar levels control
Changes in heart rate

Question 16

What are examples of positive feedback mechanisms in the body?

Answer 16

Blood clotting
Oxytocin causes more contractions
Adrenaline - HR increases till stimuli removed
Disease - increases temperature

Question 17

What is osmoregulation?

Answer 17

The homeostasis control of water potential in the blood

Question 18

What is the role of the kidney?

Answer 18

Control the vol of water in the body
Clean the blood
Remove any unwanted water, waste or toxins

Question 19

What is the nephron?

Answer 19

The filtering unit of the kidney, which performs the jobs of filtering + fluid balance

Question 20

What are the processes of osmoregulation?

Answer 20

Ultrafiltration
Selective reabsorption
Counter current multiplier
Reabsorption

Question 21

Where does ultrafiltration happen?

Answer 21

Glomerulus

Question 22

What is ultrafiltration as a result of?

Answer 22

Hydrostatic pressure

Question 23

Which is bigger the efferent or afferent arteriole?

Answer 23

Afferent

Question 24

What does the capillaries merge to form?

Answer 24

Efferent arteriole

Question 25

Describe ultrafiltration

Answer 25

Afferent arteriole is wider than efferent Hydrostatic pressure builds Causes ultrafiltration through pores of membrane

Question 26

What moves out for ultrafiltration?

Answer 26

H2O C6H12O6 Urea Mineral ions

Question 27

What remains in for ultrafiltration?

Answer 27

RBCs | Proteins

Question 28

What is the movement of filtrate restricted in the glomerulus by?

Answer 28

``` Capillary epithelial cells Connective tissues Epithelial cells of renal capsule Low hydrostatic pressure Low water potential of blood ```

Question 29

What are the main adaptions of Bowman's capsule to combat barriers of filtrate movement in glomerulus?

Answer 29

Podocytes (specialised cells) | Gaps in epithelial cells

Question 30

What is the importance of podocytes?

Answer 30

Attach to capillaries to form gaps = shorter diffusion pathway

Question 31

What is the importance of gaps in epithelial cells?

Answer 31

Easy to pass through = shorter diffusion pathway

Question 32

What is selective reabsorption?

Answer 32

Reabsorption of certain molecules back into the blood?

Question 33

How does selective reabsorption happen?

Answer 33

Co-transport

Question 34

Where does co-transport happen in reabsorption?

Answer 34

Proximal convoluted tubule

Question 35

Where does counter current mechanism happen in reabsorption?

Answer 35

Loop of Henle

Question 36

Where does anti diuretic hormone happen in reabsorption?

Answer 36

Collecting duct

Question 37

Describe co-transport

Answer 37

Na+ actively pumped out of cell to lumen from NaK pump Higher conc inside lumen so lower conc inside cell Na+ facilitatedly diffuses back in via another carrier protein Coupled movement with glucose/amino acid Molecule conc increases Molecules diffuse into blood alongside some water

Question 38

Describe the medulla

Answer 38

Inner region made up of loops of Henle, collecting ducts + blood vessels

Question 39

Describe convoluted tubule

Answer 39

Series of loops surrounded by blood capillaries | Walls made up of epithelial cells with microvilli

Question 40

Describe ureter

Answer 40

Tube that carries urine to the bladder

Question 41

Describe glomerulus

Answer 41

Many branched knot of capillaries from which fluid is forced out of the blood

Question 42

Describe renal vein

Answer 42

Returns blood to heart via vena cava

Question 43

Describe cortex

Answer 43

Outer region made up of renal capsules (Bowman's capsule), convoluted tubules + blood vessels

Question 44

Describe Loop of Henle

Answer 44

Long hairpin loop extending from cortex + into medulla

Question 45

Describe Bowman's capsule

Answer 45

Cup shaped structure at the start of nephron, surrounding a mass of blood capillaries (glomerulus)

Question 46

Describe renal artery

Answer 46

Supplies kidney with blood from heart via aorta

Question 47

Describe collecting duct

Answer 47

Tube with several distal convoluted tubules from several nephrons empty Increases width as it empties into the pelvis of the kidney

Question 48

How many regions does the loop of Henle of have?

Answer 48

2

Question 49

What are the 2 regions of the loop of Henle called?

Answer 49

Descending limb | Ascending limb

Question 50

What does the 2 regions of the loop of Henle allow?

Answer 50

Allows salts to be transferred from descending to ascending limb

Question 51

What is the arrangement called that is involved in the reabsorption of water?

Answer 51

Counter-current multiplies system

Question 52

Describe the descending limb

Answer 52

Into the medulla Narrow Thin walls Highly permeable to H2O

Question 53

Describe the ascending limb

Answer 53

Back to cortex Wider Thicker Impermeable to H2O

Question 54

What happens at the descending limb?

Answer 54

H2O leaves via osmosis | + enters the blood

Question 55

What helps H2O to leave from the descending limb?

Answer 55

Low H2O potential surrounding it

Question 56

What is happening at the same time in the loop of Henle, whilst the descending limb happens?

Answer 56

Na+ is actively transported out of the ascending limb into the interstitial region

Question 57

What happens at the ascending limb?

Answer 57

Ascending = impermeable = H2O cannot leave

Question 58

Why is there a high H2O potential in the distal convoluted tubule?

Answer 58

To form H2O potential gradient = H20 can move out of collecting duct + into the blood

Question 59

Why can H2O move out of the collecting duct?

Answer 59

As its walls vary in permeability

Question 60

Where does ultrafiltration happen?

Answer 60

Glomerulus

Question 61

Where does selective reabsorption happen?

Answer 61

Proximal convoluted tubule

Question 62

Where does the counter current multiplier happen?

Answer 62

Loop of Henle

Question 63

Where does reabsorption into the blood happen?

Answer 63

Distal convoluted tubule | Collecting duct

Question 64

Explain why your water levels vary

Answer 64

``` External temperature Exercise Fluid intake Salt intake Diet Drug intake Medication ```

Question 65

Which hormone controls H2O?

Answer 65

ADH

Question 66

Where is ADH secreted from?

Answer 66

Posterior pituitary gland

Question 67

What does ADH do?

Answer 67

Increase permeability of DCT + CD | = concentrates the urine

Question 68

What happens when you are dehydrated?

Answer 68

Decrease ψ of blood Osmoreceptor cells in hypothalamus detect change Cells lose water = shrivel Stimulate neurosecretory cells in hypothalamus Increased AP's to posterior pituitary gland ADH secreted into blood Travels in blood to DCT + CD Permeability increases More H2O reabsorbed into blood

Question 69

What when you have too much water?

Answer 69

``` Increase ψ of blood Osmoreceptors detect change Gain H2O = swell Doesn't stimulate neurosecretory cells Decreased AP's to posterior pituitary gland ADH not secreted Permeability decreases at DCT + CD Less water reabsorbed ```

Question 70

How does ADH actually work?

Answer 70

``` Binds to complementary receptors on DCT + CD Activates enzyme phosphorylase Aquaporin fuses with membrane Increases permeability Water leaves CD Increases ψ gradient Concentrated urine ```