The motor end plate differs from the rest of the sarcolemma in that it contains large numbers of .

Acetylcholine receptors.

Explanation:

Acetylcholine receptors are basically membrane proteins present on the muscle cells at the synaptic end of neuromuscular junction.

A neurotransmitter known as acetylcholine binds with these acetylcholine receptors and response generated by these membrane proteins when signal transduced into muscular cell, the muscular contraction will occur and when signal ends then muscular relaxation phase started.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.