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Biology Unit 3 > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What is homeostasis?

A

The maintenance of a state of dynamic equilibrium in the body despite fluctuations in internal and external conditions.

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2
Q

Why is homeostasis important?

A

To ensure optimum conditions for enzymes and cellular processes in the body.

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3
Q

Define Negative feedback :

A

Self-regulatory mechanisms which return the internal environment to the optimum when there is a fluctuation.

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4
Q

Define Positive feedback:

A

A fluctuation which triggers changes that result in an even greater deviation from the normal level.

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5
Q

What is the set point?

A

A desired value or range of values determined by a coordinator.

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6
Q

Describe Effectors:

A

Muscles or glands which enable a response to a stimulus.

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7
Q

Describe the role of a coordinator:

A

Coordinates information from the receptors and sends instructions to the effectors.

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8
Q

What is osmoregulation?

A

The regulation of the water potential of body fluids (e.g blood,tissue fluid,lymph) by the kidney.

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9
Q

Why is osmoregulation important?

A

Prevents cells bursting or shrinking when water enters or leaves by osmosis.
Cellular reactions occur in aqueous solution therefore water levels affect conc and rate of reactions in cells

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10
Q

Define excretion?

A

The process of removing metabolic waste from an organism.

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11
Q

What is the function of the renal artery?

A

Supplies blood to the kidneys

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12
Q

What is the function of the renal vein?

A

Takes blood aways from the kidneys

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13
Q

What is the function of the ureter?

A

Takes urine to the bladder from the kidneys

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14
Q

What is the function of the urethra?

A

Release urine from the bladder, out of the body.

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15
Q

Key components of a kidney:

A

Bowman’s Capsule,cortex,renal pyramids,renal pelvis and medulla

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16
Q

Where are nephrons found in the kidneys?

A

Part of the nephron is located in the medulla and part in the cortex.

17
Q

Define Ultrafiltration:

A

The removal of small molecules,water and ions from the blood in the glomerulus of the kidney at high pressure

18
Q

Why is there a build-up of pressure in the glomerulus?

A

Afferent arteriole leading into the glomerulus is wider than the efferent arteriole taking blood
from the glomerulus.

19
Q

How are cells of the Bowman’s capsule adapted for ultrafiltration?

A

● Fenestrations between endothelial cells of capillaries

● Fluid can pass between and under folded membrane of podocytes

20
Q

Where does selective reabsorption occur?

A

Proximal convoluted tubule

21
Q

What happens during selective reabsorption?

A

● Useful molecules from glomerular filtrate (glucose, some water, some ions) are reabsorbed into the blood
● Involves membrane transport proteins

22
Q

By what mechanism are amino acids and glucose selectively reabsorbed into the blood?

A

● Secondary active transport

● Uses a co-transport mechanism involving Na+

23
Q

By what mechanism are mineral ions selectively reabsorbed into the blood?

A

Active transport

24
Q

How are filtered proteins (and some urea) selectively reabsorbed into the blood?

A

Via diffusion

25
Q

Describe the loop of Henlé.

A

A loop consisting of a descending limb (dips into the medulla) and ascending limb (rises into the cortex) surrounded by blood capillaries.

26
Q

What is an endocrine gland?

A

A gland of the endocrine system that secrete hormones directly into the bloodstream.

27
Q

How is the concentration and volume of urine controlled?

A

Controlled by the secretion of anti-diuretic hormone (ADH).

28
Q

Explain the role of the hypothalamus in osmoregulation.

A

● Osmoreceptors in hypothalamus detect the concentration of the blood plasma
● Hypothalamus secretes ADH

29
Q

Explain the role of the posterior pituitary gland in osmoregulation.

A

Stores and secretes the ADH produced by the hypothalamus.

30
Q

Describe the effects of kidney failure.

A

● Build-up of toxic waste products (e.g. urea) causes symptoms such
as vomiting
● Fluid accumulation leads to swelling
● Disruption to electrolyte balance can make bones more brittle
● High concentrations of renin may lead to hypertension
● Low concentrations of EPO can lead to anaemia

31
Q

Outline the potential treatments for kidney failure.

A 
● Low protein diet
● Control of blood calcium and potassium levels using medication
● Drugs to lower blood pressure
● Renal dialysis
● Kidney transplant
32
Q

Describe renal dialysis.

A

● Medical procedure that artificially filters the blood
● Relies on a partially permeable membrane between
the patient’s blood and dialysis fluid
● Two types: haemodialysis and peritoneal dialysis.

33
Q

Describe how animal excretory products can differ.

A

● Freshwater animal species excrete ammonia
● Reptiles, birds and insects produce uric acid
● Mammals excrete urea

34
Q

How does the length of the loop of Henlé differ between mammals?

A

● Length of the loop varies depending on the availability of water in the mammal’s environment
● Longer loop in desert animals (e.g. kangaroo rat) to allow greater time for reabsorption of water and salts

35
Q

Describe the process of ultrafiltration:

A

Bowman’s capsule
High Hydrostatic Pressure in G forces small molecules (U,W,G,I) out of capillary fenestrations against O G
Basement membrane filter - Blood cells and large molecules (P) remain in capillary.

36
Q

How are cells in the proximal convoluted tubule adapted for selective reabsorption?

A

MV LSA for Co-T P
Lots M ATP for AT of G into intercellular spaces
Folded Basal Membrane LSA
Tight Junctions stop ReA materials leaking back intol filterate
Peritubular C extend into the M enabling reabsorption of materials

37
Q

Describe what happens in the loop of Henlé.

A 
AT of Na+ and Cl- out of AL
WP of Interstial Fluid D
Movement of water out of DL via O
WP of F D going down D (lowest M,highest AL)
Counter Current Multiplier
38
Q

Describe how ADH affects the reabsorption of water from the kidney tubules.

A

● ADH causes insertion of aquaporins into the plasma membranes
of cells of the DCT and collecting duct
● Increases permeability of the DCT and collecting duct
● More water reabsorbed
● More concentrated urine produced

Biology Unit 3 (4 decks)

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