Living Control Mechanisms

Question 1

Homeostasis

Answer 1

The maintenance of a constant internal environment in response to changing external conditions.
Temperature, blood-glucose, blood-oxygen.

Question 2

Autocrine (communication)

Answer 2

Cells talking to themselves.
Signal produced goes back to the same cell.
Receptor on same cell.

Question 3

Paracrine (communication)

Answer 3

Cells talking to neighboring cells a short distance away.
Signal diffuse across gap between 2 cells.
Does not enter bloodstream.

Question 4

Endocrine (communication)

Answer 4

Cells talking to other cells elsewhere in the body.
Signal = hormone.
Travel in blood to reach more distant target.

Question 5

Hormone

Answer 5

Molecule that acts as a chemical messenger and travels in the bloodstream.
Classified according to structure: amino acid derivative, peptide and steroid.

Question 6

Amino acid derivative hormones

Answer 6

Synthesised from tyrosine. 
Very small. 
Quick response. 
Hydrophillic so can dissolve in blood. 
Adrenaline.

Question 7

Peptide hormones

Answer 7

Made of amino acids.
Vary in size from few amino acids to small protein.
Quick response - signal transduction cascade.
Hydrophillic so can dissolve in blood.
Receptor is extracellular as hormone can’t move through hydrophobic tails of phospholipid bilayer.

Question 8

Steroid hormones

Answer 8

All made from cholesterol.
Different enzymes modify cholesterol in different ways to produce a variety of hormones.
Slow response - affects DNA directly.
Lipid soluble.
Transported into blood bound to protein as can’t dissolve in water.
Receptor is intracellular as hormone is lipid soluble.

Question 9

Simple feedback loop

Answer 9

1) Stimulus.
2) Sensor.
3) Control.
4) Effector.
5) Repeats.