INTERCELLULAR COMMUNICATION Dr.Mohammed Sharique Ahmed Quadri Assistant prof. Physiology Al Maarefa College م ي ح ر ل ا ن م ح ر ل ه ا ل ل م ا س ب
Jan 17, 2016
INTERCELLULAR COMMUNICATION
Dr.Mohammed Sharique Ahmed QuadriAssistant prof. Physiology
Al Maarefa College
بسم الله الرحمن الرحيم
INTERCELLULAR COMMUNICATION
• Direct intercellular communication– Gap junction – Transient direct linkup of surface markers
• Indirect intercellular communication– Through extracellular chemical messengers or signal
molecules • Paracrine• Neurotransmitters• Hormones• Neurohormones
Direct intercellular communication
Direct intercellular communication
(complementary surface markers)
Indirect intercellular communication
– extracellular chemical messengers or signal molecules • Paracrine• Neurotransmitters• Hormones• Neurohormones
Source
Distance
Means by which get to target cells
diff
ers
–Paracrines• Local chemical messengers• Exert effect only on neighboring
cells in immediate environment of secretion site
–Neurotransmitters• Short-range chemical messengers• Diffuse across narrow space to act
locally on adjoining target cell (another neuron, a muscle, or a gland)
• Long-range messengers• Secreted into blood by endocrine glands in response to
appropriate signal• Exert effect on target cells some distance away from
release site
Hormones
– Neurohormones• Hormones released into blood by neurosecretory
neurons• Distributed through blood to distant target cells
Hormones
• Two distinct groups of hormones based on their solubility properties– Hydrophilic hormones
• Highly water soluble • Low lipid solubility
– Lipophilic hormones• High lipid solubility• Poorly soluble in water
–Extracellular chemical messengers bring about cell responses primarily by signal transduction
Process by which incoming signals are conveyed to target cell’s interior
• Binding of extracellular messenger (first messenger) to matching receptor brings about desired intracellular response by either– Opening or closing channels– By activating receptor enzymes – Activating second-messenger systems
• Activated by first messenger• Relays message to intracellular proteins that carry out
dictated response
Opening of receptor-channel when an extracellular messenger binds
Tyrosine kinase pathway.
Activation of second messenger pathway via G-Protein couples receptors
Amplification of the initial signal by a second-messenger pathway
• RECEPTORS AND THEIR REGULATION The receptors on target tissues are not static. They are
dynamic and mobile and their number also changes during the process of regulation.
Up Regulation of Receptors – The number of receptors is increased on the target
tissue. This happens when there is less concentration of ligand in the ECF
Down Regulation of Receptors The number of receptors is decreased on the target
tissue. This happens when ligand concentration is more in the ECF
References
• Human physiology by Lauralee Sherwood, seventh edition
• Text book physiology by Guyton &Hall,11th edition
• Text book of physiology by Linda .s contanzo,third edition
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