The tetanus toxin tetanospasmin blocks release of the neurotransmitter (GABA) that inhibits motor neurons and decreases muscle contraction
This causes persistence of the signal to contract and the resulting violent muscle contraction known as tetanic spasm. Compare the sustained contraction of muscle cells in rigor mortis with muscle contraction caused by the action of tetanospasmin on motor neurons.
What will be an ideal response?
Answer: In the case of rigor mortis, the ATP supply is depleted because the cells are in various stages of dying. Loss of ATP causes myosin head crossbridges to lock onto actin thin filaments. The cells accumulate crossbridges over time until ATP is depleted from the cell.
In the case of tetanospasmin, the continuous stimulation of contraction prevents lowering of sarcoplasmic Ca2+ ion concentration by stimulating continual release of Ca2+ pumped back into the sarcoplasmic reticulum by Ca2+-ATPases. As a result, the consistent activating levels of Ca2+ in cytosol keep the muscle cells in a chronic state of contraction.
You might also like to view...
What is true of the Shannon diversity index? Select all that apply.
_____ Within a community, Its value increases as the number of species sampled increases. _____ Its value is independent of species relative abundance. _____ It does not take into account very rare species. _____ Its value increases when individuals are more evenly distributed among species
Which of the following can result in speciation
within a few generations? a. development of a physical barrier b. polyploidy arising in a plant species c. postzygotic isolating mechanisms d. change in environmental conditions e. the introduction of a new predator into an area
The change in one population driven by a change in an associated population is called
A) assortative evolution. B) genetic drift. C) coevolution. D) random mutation. E) fitness.
Regarding the order Rhizobiales of the class Alphaproteobacteria, which genus includes human pathogens?
a. Agrobacterium b. Bradyrhizobium c. Beijerinckia d. Brucella