Transcript cobra 11

Poison
apparatus
Dr. J AGDISH KAUR
P.G.G.C.,Sector 11
Chandigarh
Components of poison apparatus
poison glands (secretion of
poison)
 poison ducts (conduction of
poison),
Fangs ( injection of poison)
 muscles (squeezing the poison)
1.
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Poison glands:
Saclike glands situated one on either side of the upper jaw.
Modified superior labial, or parotid glands.
Each gland is covered by a constrictor muscle
The contraction of the muscle, during the bite, squeezes the poison from the
gland.
2. Poison duct:
From each poison gland a narrow poison duct leads to the base of the poison fang.
3. Fangs:
These are modified teeth attached to maxillary bones.
 They are grooved and help in injecting the poison into the body of the victim.
 Fangs serve as hypodermic needles.
The poison is faint yellow, tasteless and odour less fluid acidic in reaction. It is fatal
only when mixed in blood.
Snake venom
 Highly modified saliva that is produced by
special glands of certain species of snakes.
 a combination of many different proteins and
enzymes.
 Many of these proteins are harmless to
humans, but some are toxins.
Snake venoms are generally not dangerous
when ingested, and are therefore not technically
poisons.
Consists of proteins, enzymes, substances with
a cytotoxic effect, neurotoxins and coagulants.
* Phosphodiesterases are used to interfere with the prey's
cardiac system, mainly to lower the blood pressure.
* Phospholipase A2 causes hemolysis by lysing the
phospholipid cell membranes of red blood cells.
* Snake venom inhibits cholinesterase to make the prey
lose muscle control.
* Hyaluronidase increases tissue permeability to increase
the rate that other enzymes are absorbed into the prey's
tissues.
* Amino acid oxidases and proteases are used for digestion.
Amino acid oxidase also triggers some other enzymes and is
responsible for the yellow color of the venom of some
species.
* Snake venom often contains ATPase, an enzyme which
catalyzes the hydrolysis of ATP to ADP and a free phosphate
ion, or to AMP and diphosphate.
1. Neurotoxins
1. Fasciculins
2. Dendrotoxins
3. α-neurotoxins
2. Cytotoxins
1. Phospholipases
2. Cardiotoxins
3. Haemotoxins
1) Fasciculins:
These toxins attack cholinergic neurons (those that use ACh as a
transmitter) by destroying acetylcholinesterase (AChE). ACh
therefore cannot be broken down and stays in the receptor. This
causes tetany, which can lead to death.
Snake example: Black Mamba
2) Dendrotoxins:
Dendrotoxins inhibit neurotransmissions by blocking the exchange
of + and – ions across the neuronal membrane ==> no nerve
impulse. So it paralyses the nerves.
Snake example: Mambas
3) α-neurotoxins:
α-neurotoxins also attack cholinergic neurons. They mimic
the shape of the acetylcholine molecule and therefore fit
into the receptors → they block the ACh flow → feeling of
numbness and paralysis.
Snake examples:
- Kraits use erabutoxin (the Many-banded krait uses
Bungarotoxin)
-Cobras use cobratoxin,
1) Phospholipases:
Phospholipase is an enzyme that transforms the
phospholipid molecule into a lysophospholipid (soap) ==>
the new molecule attracts and binds fat and rips a hole in
the cell membrane. Consequently water flows into the cell
and destroys the molecules in it. That is called necrosis.
Snake example: The Japanese Habu snakes (low toxicity)
2) Cardiotoxins:
Actually cardiotoxins are muscle venoms. They bind to
particular sites on the surface of muscle cells causing
depolarisation ==> the toxin prevents muscle contraction.
For example the heart muscle: the heart will beat
irregularly and stop beating, which will cause death.
Snake example: King Cobra and some other cobras
3) Haemotoxins:
The toxin destroys red blood cells (erythrocytes).
This symptom is called haemolysis. As it is a very
slowly progressing venom it would probably not kill
a human - another toxin in the snake’s venom would
most certainly have caused death by then.
Snake example: most Vipers and the members of
Naja genus
Antivenin
• An antivenin is prepared by injecting
increased doses of snake venom into
the horse until the horse becomes fully
immunised. Then blood serum of the
horse is collected and preserved. In
India Antivenin is produced at the
Haffkin's Institute at Bombay and
Central Research Institute in Himachal
Pradesh.