Which of the following is the name for the shaft of a long bone?

A. Elastin is a protein found in connective tissue that provides elasticity, allowing the skin and other tissues to return to their original shape after stretching. It does not influence skin color.

B. Hemoglobin is the oxygen-carrying component of red blood cells. It gives the skin a reddish tint due to blood flow, but it is not the primary determinant of overall skin color.

C. Melanin is the pigment produced by melanocytes in the skin. The type and amount of melanin determine the color of an individual's skin, with darker skin having more melanin.

D. Keratin is a structural protein found in the skin, hair, and nails, providing strength and protection. While it contributes to the skin's texture and appearance, it does not determine skin color.

A. Peristalsis, the wave-like contraction of the digestive tract, is typically decreased during sympathetic stimulation. The sympathetic nervous system tends to slow digestive processes as the body prioritizes "fight-or-flight" responses.

B. Bladder tone is typically decreased by sympathetic stimulation. The sympathetic nervous system causes relaxation of the bladder, inhibiting urination during stressful situations.

C. Heart rate increases with sympathetic stimulation. The sympathetic nervous system prepares the body for action by increasing heart rate, enhancing blood flow to muscles, and increasing energy levels.

D. Saliva production decreases with sympathetic stimulation. The body reduces non-essential functions such as salivation during stress, focusing energy on immediate survival functions.