When a muscle cell receives a signal from a motor neuron, every sarcomere within that muscle cell is activated. The signal moves from the motor neuron to the muscle cell by crossing the synapse. When acetylcholine binds the sodium enters the T tubules and this causes calcium to be released from the sarcoplamic reticulum. Calcium binds to tropomyosin, which allows actin to bind to myosin and each sarcomere contracts. There is nothing and no way to separate individual sarcomeres. They are all activated together.
Explanation:
A keystone species is an organism that helps define an entire ecosystem. By keeping populations of mussels and barnacles in check, this sea star helps ensure healthy populations of seaweeds and the communities that feed on them—sea urchins, sea snails, limpets, and bivalves.
Answer:
When a child is conceived each parent gives 23 of their chromosomes
Answer:
igneous rocks - geosphere
oceans, frozen lakes - hydrosphere
gaseous nitrogen - atmosphere
sea animals, marine plants - biosphere
Explanation:
