Question

Predict what effect each of these venoms would have had on the muscle contractions of the biventer cervicis muscle. Remember to justify your answer

Venoms and Reactions -

1.      Redback spider (Latrodectus hasseltii) – contains a toxin which forms pores in the cell membrane of neurons, allowing the influx of Ca²⁺ into the nerve terminal

2.      Blue-ringed octopus (Hapalochlaena lunulata) – contains a toxin which blocks voltage-gated Na⁺ channels

3.      Funnel-web spider (Atrax robustus) - contains a toxin which causes delayed inactivation of voltage-gated Na⁺ channels

4.      Tiger snake (Notechis scutatus) – contains a toxin which prevents ACh binding to nAChRs on muscle fibres

Answer 1

Answer:

Effect of venoms on muscle contractions of the biventer cervicis muscle,

1.      Redback spider (Latrodectus hasseltii) – contains a toxin which forms pores in the cell membrane of neurons, allowing the influx of Ca2+ into the nerve terminal-

Its venom is alpha-latrotoxin (neurotoxic venom) which results in the exocytosis of synaptic vesicles from parasympathetic terminals due to the stimulation of calcium-dependent mechanisms, releasing catecholamines and acetylcholine leading to muscle contraction of the biventer cervicis muscle.

2.      Blue-ringed octopus (Hapalochlaena lunulata) – contains a toxin which blocks voltage-gated Na+ channels-

Blue-ringed octopus venom contains toxin Tetrodotoxin which blocks sodium channels and produces a dose-dependent flaccid voluntary paralysis and autonomic nerve dysfunction; the sting is often fatal. It may develop numbness and muscle paralysis.

3.      Funnel-web spider (Atrax robustus) - contains a toxin which causes delayed inactivation of voltage-gated Na+ channels-

Delta atracotoxin is the toxin produced by the funnel spider, produces potentially fatal neurotoxic symptoms by slowing the inactivation of sodium ion channels in autonomic and motor neurons. In the spiders the toxin exerts this same activity upon potassium and calcium ion channels resulting in generalized skeletal muscle fasciculation or involuntary muscle contractions and relaxation of the cervicis muscle.

4.      Tiger snake (Notechis scutatus) – contains a toxin which prevents ACh binding to nAChRs on muscle fibres-

Tiger snake venom contains a potent procoagulant toxin that causes venom-induced consumption coagulopathy (VICC) in bite victims. This life-threatening pathology is the most common serious consequence of snakebite.

The venom contains pre- and post-synaptic neurotoxins.i.e ACh and nAChRs

Myotoxicity occurs in a small percentage of bite cases, the result of enzymatic phospholipase a2 toxins in the venom resulting in flaccid paralysis of cervicis muscle