12. Intro To Endocrine System And Appetite Flashcards
What are the characteristics of a control system?
Stimulus
Receptor
Communication via afferent pathway to control centre
Communication via efferent pathway to effector (causes change)
Via negative feedback to stimulus
What curs from the environment keep body on a 24 hour cycle?
Light Temperature Social interaction Exercise Eating/drinking pattern
Which hormone is involved in setting biological clock?
Melatonin from pineal gland
What is the body’s natural body clock called?
Circadian rhythmic
Where is the ‘biological clock’?
In brain in small group of neurones in suprachiasmatic nucleus
What is negative feedback?
Response in a way to reverse direction of change
Most common form of feedback in physiological systems
What is positive feedback?
Response in a way also as to change the variable even more in the direction of the change
Used when rapid change is desirable
E.g. blood clotting, in childbirth
How does negative feedback work?
Hypothalamus detects change and releases hormone 1
Anterior pituitary receives hormone 1 and releases hormone 2
Target gland receives hormone 2 and releases hormone 3 to cause change
What is osmolarity?
Number of osmoles per litre of solution
What is osmolality?
Number of osmoles per Kg of solution
What is an osmole?
Amount of substance that dissociates in solution to form one mole of osmotically active particles
What is autocrine communication?
Hormone signal acts back on cell of origin
What is paracrine communication?
Hormone signal carried to adjacent cells over a short distance via interstitial fluid
What is endocrine communication?
Hormone signal released into bloodstream and carried to distant target cells
What is neurocrine communication?
Hormone originates in neurone and after transport down axon released into bloodstream and carried to distant target cells
What are the similarities between endocrine and nervous systems?
Both neurons and endocrine cels are capable of secreting
Both neurons and endocrine cells can be depolarised
Some molecules act as both neurotransmitter and hormone
Mechanism of action requires interaction with specific receptors in target cells
Both work in parallel to control homeostasis
What are the 4 classes of hormones?
Peptide/polypeptide
Amino acid derivatives
Glycoproteins
Steroids
Describe peptide/polypeptide hormones
Short chains of amino acids
E.g. insulin, glucagon, growth hormones
All water soluble
Describe amino acid derivatives hormones
Synthesised from aromatic amino acids
E.g. adrenaline, noradrenaline, thyroid hormones, melatonin
Adrenal medulla hormones water soluble
Thyroid hormones lipid soluble
Describe glycoprotein hormones
Often made up of subunits
Carbohydrates size chain
E.g. luteinizing hormone, follicle stimulating hormone, thyroid stimulating hormone
All water soluble
Describe steroid hormones
All derived from cholesterol
Steroidogenic tissues convert cholesterol to different hormones
E.g. cortisol, aldosterone, testosterone
All lipid soluble
How are hormones transported?
Some travel in blood in simple solution (peptides, adrenaline)
Most hormones must bind to proteins
Dynamic equilibrium between bound and free forms of hormone in plasma
Only free form is biologically active
What are the roles of carrier proteins?
Increase solubility of hormone in plasma
Increase half-life
Readily accessible reserve
What are the 3 main factors that determine hormone levels in blood?
Rate of production: synthesis and secretion
Rate of delivery: higher blood flow will deliver more hormone
Rate of degradation: hormones are metabolised and excreted from the body
