Pain sensation Pain receptors are also called as nociceptors They are located at the ends of small 'C unmyelinated or myelinated A delta fibers a) Definition Pain sensation is unpleasant but protective sensation aroused by noxious stimuli that damage or can damage body tissues b) Physiology (properties & reaction) Purpose or importance: Protective Stimulus: noxious (chemicals like- Ach, bradykinin, serotonin, hydrogen ions, potassium ions, prostaglandins or mechanical or thermal) Receptors: free nerve endings (polymodal receptors) Adaptation : non or slow adapting receptors Nerve fibers: fast pain is carried by A-delta nerve fibers while slow pain by 'C' type. Neurotransmitters: glutamic acid (at spinal cord) for fast pain, substance P (at spinal cord) for slow pain and Lewis P factor for muscle pain, Pathway: lateral spinothalamic (specific neo spinothalamic for fast pain and diffuse and non specific paleo spinothalamic for slow pain) Reaction : pain is a
Special types of Active Transport (Macro- Molecules)
This includes vesicular transport...which includes Endocytosis and Exocytosis
ENDOCYTOSIS
Endocytosis includes..
- 1. Pinocytosis (cell drinking)
- 2. Phagocytosis (cell eating)
- 3. Receptor mediated endocytosis
Vesicular exocytosis includes basically release of neuro transmitter e.g. ACh
Pinocytosis (Cell drinking)
It is the process of engulfing liquid substances by enfolding of cell membrane e.g. Reabsorption by renal tubular epithelial cells
Phagocytosis (cell eating) Engulfing the solid particles e.g. bacteria, dead cells and foreign particles by the cells. This process involves three steps i) Attachment stage i) Engulfment stage iii) Degradation stage
Receptor mediated endocytosis
In this process substance binds with special receptor protein on the cell membrane. Then protein-substance complex is engulfed by the cell membrane by the process of endocytosis e.g. Transport of iron, cholesterol into the cell, LDL and Vita B12 take up
EXOCYTOSIS
Exocytosis is reverse of endocytosis, i.e. by this process substance are expelled from the cell without passing through the cell membrane
Release of hormones and enzymes by secretory cells of the body occurs by exocytosis. This process requires Ca++,energy and docking proteins
e.g. Release of insulin from pancreatic beta cells, release of ACh from nerve ending Release of dopamine from glomus cells of peripheral chemoreceptors
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