Living Control Mechanisms Flashcards
What is homeostasis?
Maintenance of a constant internal environment
Examples of homeostasis in the body
Potassium levels
Temperature
Hydrogen ion
Glucose
Blood oxygen
What are the stages of the homeostasis model?
Set Point
Control Centre
Effectors
Regulated variable
Sensor
Control centre etc
Why is communication important in homeostasis?
Cells must communicate with each other to achieve homeostasis
There needs to be a co-ordinated response
What are the two different communication systems in homeostasis?
Endocrine - hormones
Nervous - electrical
What is a receptor?
The thing that receives the signal
What is autocrine signalling?
Cells talking to themselves
Form of cell signalling in which a cell secretes a hormone or chemical messenger that binds to autocrine receptors on that same all
What is paracrine signalling?
Cells talking to neighbouring cells a short distance away
Type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells
How is the signal in paracrine signalling transport?
•Signal diffuses across gap between cells
•Inactivated locally, so doesn’t enter the blood stream
Give examples of paracrine signalling
Interleukins
•Signalling in the immune system
•Mainly between white blood cells
Platelet derived growth factor (PDGF)
•Released from platelets
•Regulates cell growth
What is endocrine signalling?
Cells talking to other cells elsewhere in the body
Hormones are secreted by specialised endocrine cells and carried through the circulation to act on target cells at distant body sites
Give examples of endocrine organs/glands?
• Hypothalamus
• Pituitary
•Thyroid
• Adrenals
• Pancreas
• Ovaries
• Testes
What is a hormone?
Molecule that acts as a chemical messenger
What are amino acid hormones?
Synthesised from tyrosine
Example; adrenaline
What are hormones classified according to?
Classified according to structure;
●Amino-acid derivatives
●Peptide
●Steroid
What are peptide hormones?
●Made of amino acids
●Vary in size from few amino acids to small proteins
●Some have carbohydrate side chains (glycoproteins)
●Hydrophillic (like water)
What do peptide and amino acid hormones have in common?
Produce a quick reaction in the body
What type of hormone is TSH?
Peptide hormones
What are steroid hormones?
●All made from cholesterol
●Different enzymes modify molecule to produce a variety of hormones
●Can’t dissolve in water
●Can dissolve in lipids
How do steroid hormones work?
Steroid hormones produce a slow response
Give an example of a steroid hormone
Testosterone
What is a positive feedback loop?
Signal is amplified
When the product of a reaction leads to an increase in that reaction
What is a negative feedback loop?
Allows the body to regulate itself
The process starts when there is an increase in output from a body system, which results
In higher levels of certain proteins or hormones
Give an example of a negative feedback loop
Pituitary-thyroid loop
What is the set point?
What we are aiming for
