Receptors, signals ans responses Flashcards
why is cell communication important?
there are lots of tissues, organs + cell types in the human body - need to keep responding to changes in environment.
Growth, infection, blood glucose, wounds, and time to die.
3 important steps in cell signalling
signal, receptor, response
cellular response without a signal can lead to
cancer
over reacting immunity signals
inflammatory response
not responding to immunity signals
immunodeficiency
which cells make insulin?
Beta cells in the islets of lagerhands, located in the pancreas
what do the alpha cells in the pancreas make?
glucagon
what happens when there are low blood sugar levels?
glucagon is released, tells the cells that you need fat cells to start releasing their energy source to maintain blood sugar levels
ENDOCRIN SIGNALLING
hormone secretion into the blood by an endocrine gland - to act on distinct target cells in the body
PARACRINE SIGNALLING
cells secrete signals close to the target cells
what are direct contacts?
in the epithelial sheet forming connections between cells.
they detect signals from neighbouring cells and the ECM (how rigid is the ECM)
what is synaptic signalling
where nerve cells release neurotransmitter into the synaptic cleft - taken up and causes a response in the target cells
example of hormones that use endocrine signalling
testosterone and insulin
examples of paracrine signalling
growth factors, cytokines (immune cells), NO
what are neurotransmitters derived from/
amino acids
what are steroids derived from?
cholesterol
example of a small molecule signal
adrenaline
examples of peptide hormones
hCG, LH
insuline
example of a steroid hormone
testosterone
what are the 4 main receptor types
steroid receptors, G protein coupled, ligand gated channels, enzyme linked
what are 2 main types of repsonsed to signals
Turn genes on or off
Modulate the activity of cellular proteins
what are steroid receptors?
they are transcription factors/activators that turn genes on and off
are steroid lipophilic or hydrophilic?
lipophilic
so they diffuse across cell membranes
where would you find a steroid receptor?
in the nucleus or cytoplasm
sequence of events for steroid receptors
2 steroid receptors – form dimer – only in this form can the steroid recpetors act as transcription factor – need to bind to enhancer – induce recruitment of standard transcription machinery to the proton region (initiation complex) and then polymerases transcribe the gene
What does the enhancer region do?
coordinated signals and timing
what provides specificity for steroid receptors?
Different steroid receptors bind different steroids and different steroid receptors different enhancers
which drug is used for medical abortions?
Mifepristone