Lecture 21 Flashcards
How do cell communicate
using signalling molecules
Where are the receptors
• Cell surface • Signal transduction pathways • Second messengers • Intracellular receptors
Where are hormone produced
• Endocrine organs
What are the hormonal signalling molecules
• peptide, amine derived, steroids,
eicosanoids
What are the ways of signalling
Hormonal Electrical External Mechanical Immunological Metabolic Dissolved gases
What are external ways of signalling
• odorants, taste, light
What are immunological ways of signalling
• cytokines, chemokines
How does chemical cell
communication
• Extracellular signal binds to receptor • Signal is transduced into an activation or inactivation response through a cascade of intracellular messengers
What are the signal pathway for chemical cell communication
Multiple, hierarchical steps Amplification Activation of multiple pathways within the cell Antagonism by feedback mechani
What does the signalling molecule physiologic effect depends on
• Depends largely on the concentration of signalling
molecules in blood and extracellular fluid
• Nanomolar-Picomolar 10-9 -10-12 M
• Is also dependent on the number of receptors, their
distribution and developmental expression
• The concentration of hormones and other signalling
molecules seen by target cells is determined by three
factors:
1) Rate of production
2) Rate of delivery
3) Rate of degradation and elimination
What does feedback imply
implies a mechanism for changing rate of
production or secretion
What determine the level and duration of hormonal effects
• Lifespan in blood • Extent of binding to plasma proteins • Metabolic inactivation • Excretion • Number & sensitivity of receptors • Upregulation • Downregulation
What do cells in direct contact(adjecent) to each other signal each other
Gap
Junctions
What is the use of gap junction
Allow direct electrical and chemical communication between cells. Signals are passed through gap junctions from the cytosol of one cell to the cytosol of the next cell Quick signalling Important in propagating changes in electrical potential through tiss
How do lung cilia move in unison and heart move in unison
on
via gap junction signal
How contact is made between two cell
Contact is made between a membrane-bound signalling molecule on the surface of one cell and a complementary receptor on the surface of another cell
What does endocrine mean
If the molecule acts on
distant cells or tissues it is
What does paracrine mean
• Signal acts on neighbouring
cells
What does autocrine mean
• Signal acts on on the same
cell that released the signal
molecules
• Self-inducing
What is one thing the target cell must have in order to receive the signal
Target cell must have the
correct receptor for the
signal molecule
What are the examples of autocrine signalling
IL-1 produced by monocytes
IL-2 produced by lymphocyt
How fast does paracrine signalling degrade
The signalling molecule is rapidly taken up by cells or broken down by extracellular enzymes • Often results in a signalling concentration gradient
What is endocrine signalling
• Intercellular communication involving a molecule produced by one cell that acts on distant cells or tissues • Called hormones
Where are endocrine distributed
• Distributed in blood
What are the 4 types of hormones
- Four types of hormones
- Peptides and proteins
- Steroids
- Amines
- Eicosanoids
What are the classical hormones
- Insulin
- Adrenalin
- Thyroxine
What are the neurohormones
• Oxytocin • Antidiuretic hormone • Hypothalamic releasing and inhibiting hormones Act like classical hormones, but are released into blood from neurones
What are the main hormone producing organs in animals
- Hypothalamus
- Anterior pituitary
- Thyroid gland
- Adrenal gland
- Pancreas
- Ovaries
- Testes
What hormone does hypothalamus produce and what it hormone
(oxytocin, antidiuretic hormone via posterior pituitary & hormones that act on the anterior pituitary)
