Internal means its on the inside
external means its on the outside
so an internal regulator is when the proteins respond to events on the inside of a cell
and an external regulator is when the proteins respond to events outside the cell
Answer:
Body systems are used throughout your body to help you move and to live like the heart for example.
A
A haploid cell formed in the male seminiferous tubules
The reproductive tissues of male and female humans develop similarly in utero until a low level of the hormone testosterone is released from male gonads. Testosterone causes the undeveloped tissues to differentiate into male sexual organs. Primitive gonads become testes; other tissues produce a penis and scrotum in males.
Answer:
all the muscles.
Explanation:
The muscular system is composed of all muscles in the body. The main function of the muscles is to produce movement in different parts, voluntary or involuntary, creating equilibrium. Muscles are made of myocytes. There are three types of muscles: smooth muscle, skeletal muscle, and myocardium.
- The smooth muscle is formed by fusiform cells, mononucleated, and no transversal striations. There is a protein contraction system, but not as organized as the one of the skeletal muscle.
Smooth-muscle can be found in organs, vessels, veins, and arteries. It provides sustained contractions, slow and rhythmical, but not voluntary.
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Skeletal muscle is the most abundant muscle in vertebrates, constituting the somatic musculature. It proportionates motion to extremities and digits and is responsible for the position and posture of the individual. It is also involved in eye movements, respiration, mastication, deglutition, and phonation. It moves the tongue, the superior esophagus, and the pharynx.
The skeletal muscle is innervated by axons of the motor neurons coming from the CNS. The contraction of the skeletal muscle is voluntary and fast.
Cells composing the striated muscle are significantly long and multinucleated. They arrange in bundles, where cells are parallel to each other.
- Myocardium tissue is more similar to the striated tissue than to the smooth one. However, there are some differences between them. Cardiac cells are cylindrical and smaller, with ramifications. Cardiac cells only have one nucleus, and occasionally there can be two. Actin and myosin filaments are arranged just as the skeletal ones, and the contraction of cardiac cells is molecularly very similar to the skeletal
