Week 1 Flashcards
Cell to Cell Communication
What are direct and indirect communication?
Direct communication:
- through gap junctions
- cell-cell interaction via surface proteins
Indirect communication:
- through chemical messengers (extracellular messengers)
What are the types of chemical messengers?
Amines, amino acids, steroids, polypeptides
What can chemical communication be classified as? (Paracrine, endocrine, autocrine, neuorocrine)
Paracrine - chemical acts on another cell which is located close to the cell from which it is released (histamine during inflammation)
Endocrine - chemical acts on another cell which is located far away from the cell which utilises bloodstream as transport system
Autocrine - chemical acts on the same cell from which it is released (often mechanism for limiting release of the chemical)
Neurocrine - chemical released from a neuron and acts on another neuron or other target cell (neurotransmitters, neuromodulators, neurohormones)
Most long distance communication is the responsibility of endocrine and nervous system. Briefly, list the different chemical messengers involved in long distance communication.
Neurotransmitters, hormones, neurohormones, cytokines
What are neurotransmitters?
- A chemical signal diffuses from neuron across narrow extracellular space to cell. Hence, neurons communicate directly cells they innervate by releaseing neurotransmitters.
- Generally short range chemical messengers
- Act locally on adjoining target cell (e.g neuron or muscle)
- Transmitters can be restricted to an individual cell (is very accurate)
- Very rapid
- Eg. acetyl choline, catecholamines, amino acids, morphine like substances, peptides
What are the two classes of neurotransmitters?
Excitatory neurotransmitters:
- causes depolarisation of postsynaptic membrane
- promote action potential
Inhibitory neurotransmitters
- cause hyperpolerisation of postsynaptic membrane
- suppress action potentials
What are neurohormones?
When a chemical messengers released by a neuron diffuses into blood
What are hormones?
- cell to cell communication molecules
- chemical messengers used in body by endocrine system
- made in gland(s) or cells
- transported by blood
- activates physiological response
- provide communication allows one cell to regulate the activity of anther cell
- Distant target tissue receptors (act on cells which are located far away from the cell from which they are released)
What are cytokines (which is involved in chemical communications)
- most recently identified communication molecules
- regulatory peptide(may act as both local and long-distance signals)
- made on demand
- autocrine or paracrine signals
- some cytokines transported through blood
Functions include cell growth, cell development, cell differentiation, immune response.
What are some of the differences between the nervous system and the endocrine system?
Nervous system
- neurtoransmitters released locally in response to nerve impulses
- close to site of release, at synapse; binds to receptors in postsynaptic membrane
- target cells include muscle cells, gland cells and other neuros
- time to onset of action is typically within milliseconds, duration of action is generally briefer
Endocrine system
- hormones delivered to tissues through blood
- far from the site of release
- target cells are cells throughout body
- time to onset of action can range from seconds to hours to days. Duration of action is generally longer (seconds to days)
What is the difference between a chemical messenger being lipophic and lipophilic?
Lipophobic:
- water soluble but not lipid soluble
- dissolve in plasma/blood
- does not cross cell membrane
- receptors on cell membrane
- e.g. glycine, GABA, catecholamine’s
Lipophilic
- lipid soluble but not water soluble
- bind to carrier proteins in blood
- easily cross cell membrane
- receptors may be in the cell
- e.g. steroid hormones
What are the four categories of membrane receptors?
Receptor-channel, receptor-enzyme, G-protein coupled receptor, Integrin receptor
What are iontropic and metabotropic receptors?
Iontropic:
- gate an ion channel (binding opens ionic movement)
Metabotropic
- effects metabolism of a cell; G protein (receptor binding activates a G-protein), Receptor kinases (receptor binding activates kinases enzymes)
What is a second messenger?
Second messengers will amplify the signal of the first messenger (ligand binding) to bring about a cell response.
Name the different second messengers
Cyclic AMP (cAMP), Cyclic GMP (cGMP) Inositol triphosphate (IP3), Diaceyl glycerol (DAG) and Calcium (Ca++)
