INTERCELLULAR COMMUNICATION بسم الله الرحمن الرحيم INTERCELLULAR COMMUNICATION Dr.Mohammed Sharique Ahmed Quadri Assistant prof. Physiology Al Maarefa College

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 F

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 differs

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)

Hormones 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

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