Negative feedback is important because it preserves homeostasis in the body, meaning a _______ internal state.
Adv.
Cells called melanocytes that lie deep in the epidermis produce a pigment, called melanin, that gives skin its color. Exposure to ultraviolet light—from the sun or a tanning bed—causes melanocytes to produce more melanin, which they pass along to the skin cells above them, yielding a suntan. But why would sun exposure prompt this increased melanin production? What is the function of a tan, in other words?
To survive, the human body needs to maintain ________ and does so primarily through the means of self-regulation known as ______.
a. high energy output; positive feedback
b. adequate fat layers; exocrine secretion
c. bone density; muscle contraction
d. homeostasis; negative feedback
e. nerve signal transmission; hormonal secretion
The text notes that bone density can increase in response to exercise. Imagine two fairly inactive people who decide to start exercising. One becomes a runner while the other becomes a swimmer. Who experiences the greater increase in bone density: the swimmer (in the arm bones) or the runner (in the leg bones)?
The four basic types of tissue in the human body are:
a. epithelial, connective, muscle, nervous.
b. epithelial, blood, muscle, nervous.
c. skin, bone, muscle, nervous.
d. skin, connective, heart, nervous.
e. epithelial, bone, connective, muscle.
Acids secreted by the stomach give the materials within it a pH level that can lie between that of lemon juice and battery acid. Yet our small intestines, which the stomach feeds into, have chemical buffers flowing into them that raise the pH level of the material coming from the stomach. Why should the stomach need such an extreme pH level while the small intestines do not?
Muscle fibers that are striated and voluntary are found in:
a. cardiac muscle.
b. skeletal muscle.
c. smooth muscle.
d. rough muscle.
e. all four types of muscle.
Hormones and the glands or cells that secrete them make up the:
a. cardiovascular system.
b. respiratory system.
c. lymphatic system.
d. urinary system.
e. endocrine system.
Surface epidermal cells of the skin:
a. rapidly divide and are filled mostly with keratin.
b. never divide and remain in place through adult life.
c. rapidly divide and are in place only a short time.
d. are dead and filled with keratin.
e. rapidly divide and are filled with fat.
Cells called _____ build bone tissue, _____ maintain it, and _____ break it down.
a. osteoblasts; osteoclasts; osteocytes
b. osteoclasts; osteons; osteoblasts
c. osteoblasts; osteocytes; osteoclasts
d. osteons; osteocytes; osteoclasts
e. osteocytes; osteoblasts; osteoclasts
The essence of muscle contraction is that thick and thin muscle proteins:
a. slide past each other.
b. link irreversibly with each other.
c. are short enough to respond quickly.
d. stay completely separate.
e. pull in opposite directions.
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