Height in Feet and Inches
4
Diabetes and Obesity Are Metabolic
Disorders 422
5
The Heat from Metabolism Must Be
Regulated 427
• Diabetes mellitus has two main forms: Type 1 (lack of insulin)
and Type 2 (insulin resistance or insensitivity). Regardless
of the type, the body reacts as if it is in a fasting state and
strives to increase blood glucose by metabolizing body fuel
stores. The increased blood glucose causes most diabetic
symptoms, including glucosuria, increased urine flow, de-
creased capillary filtration, tissue dehydration, and increased
appetite. Treatment depends on the type of diabetes but can
include monitoring of diet, exercise, and insulin injection.
• Body weight regulation is a balance between energy intake
(food intake, absorption) and energy expenditure (basal me-
tabolism, physical activity, thermic effects of food). Body
fat stores are regulated by a system involving the hormone
leptin, appetite control centers in the hypothalamus, and
activity of the sympathetic nervous system and thyroid hor-
mones, which govern food intake and energy metabolism.
• As shown, obesity is defined as body weight greater than
20% of accepted standards for age, height, and gender or
BMI of 30 or higher, as shown. Many factors contribute to
obesity, including genetic factors, eating habits, sedentary
lifestyle, and social customs. Obesity treatments include
behavior therapy (dieting, exercise), drugs, and possibly
surgery (gastric bypass, gastric banding).
B od y m ass in d ex • Figure 1 4 .1 6
Weight
in
Pounds
120
130
140
150
160
170
180
190
200
210
220
230
240
250
4'6"
29
31
34
36
39
41
43
46
48
51
53
56
58
60
4'8"
27
29
31
34
36
38
40
43
45
47
49
52
54
56
4'10"
25
27
29
31
34
36
38
40
42
44
46
48
50
52
5'0"
23
25
27
29
31
33
35
37
39
41
43
45
47
49
5'2"
22
24
26
27
29
31
33
35
37
38
40
42
44
46
5'4"
21
22
24
26
28
29
31
33
34
36
38
40
41
43
5' 6"
19
21
23
24
26
27
29
31
32
34
36
37
39
40
5'8"
18
20
21
23
24
26
27
29
30
32
34
35
37
38
5'10"
17
19
20
22
23
24
26
27
29
30
32
33
35
36
6' 0"
16
18
19
20
22
23
24
26
27
28
30
31
33
34
6'2"
15
17
18
19
21
22
23
24
26
27
28
30
31
32
6' 4"
15
16
17
18
20
21
22
23
24
26
27
28
29
30
6' 6"
14
15
16
17
19
20
21
22
23
24
25
27
28
29
6'8"
13
14
15
17
18
19
20
21
22
23
24
25
26
28
Underweight
Q Healthy weight
Q Overweight
Q Obese
• Body temperature is a balance between heat production
and heat loss. Heat production is mainly due to the basal
metabolic rate (BMR), which can be influenced by physical
activity, hormones, nervous activity, food intake, age, and
other factors. Heat loss is mainly due to radiation, conduc-
tion, convection, and evaporation.
• The temperature regulation system includes thermorecep-
tors in the skin and hypothalamus, a “thermostat” in the
hypothalamus, and effectors including sympathetic nerve
activity and thyroid hormones. If body temperature drops, it
sets off a negative-feedback system in which vasoconstric-
tion conserves body heat, muscle contractions generate
heat, and adrenal and thyroid hormones increase BMR.
These processes work to restore normal body temperature.
• Increases in body temperature trigger a negative-feedback
system, as shown, that works to increase radiative heat loss
by vasodilation and evaporative heat loss by sweating. De-
creases in thyroid hormones reduce BMR, thereby reducing
heat production. All these processes work to restore normal
body temperature.
N e g a tiv e -fe e d b a c k m ech an ism s th at d e c r e a se
h ea t p rod uction and in crease h eat loss in re sp o n se
to increasing b o d y tem p e ra tu r e • Figure 1 4 .1 9
Effectors
Decreased
thyroid hormone
levels lower
BMR
• Infections, bacterial toxins, hyperthyroidism, and immune
reactions can cause fevers in which the hypothalamic ther-
mostat is reset to higher temperatures. The resetting pro-
cess involves pyrogens and prostaglandins that work in the
hypothalamus. The elevated temperatures continue until the
primary cause is eliminated. Fevers can be reduced through
the administration of aspirin, acetaminophen, or ibuprofen.
Vasodilation
increases heat
loss through skin
by radiation and
conduction
Sweat glands
secrete sweat and
remove heat by
evaporation
432 CHAPTER 14
The Digestive System, Nutrition, and Metabolism
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