1. Endocrine System Part 5B

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Adrenal Glands
Hormones of the adrenal cortex (continued)
Glucocorticoids (including cortisone and cortisol)
Produced by middle layer of adrenal cortex
Promote normal cell metabolism
Help resist long-term stressors by increasing blood glucose levels (hyperglycemic hormone)
Anti-inflammatory properties
Released in response to increased blood levels of ACTH
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Adrenal Glands
Hormones of the adrenal cortex (continued)
Sex hormones
Produced in the inner layer of the adrenal cortex
Small amounts are made throughout life
Most of the hormones produced are androgens (male sex hormones), but some estrogens (female sex hormones) are also formed
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Adrenal Glands
Adrenal medulla
Produces two similar hormones (catecholamines)
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
These hormones prepare the body to deal with short-term stress (“fight or flight”) by:
Increasing heart rate, blood pressure, blood glucose levels
Dilating small passageways of lungs
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5. Figure 9.8 Microscopic structure of the adrenal gland.
Capsule
Mineralocorticoid- secreting area
Kidney
Glucocorticoid- secreting area
Cortex
Adrenal gland
Adrenal cortex
Medulla
Cortex
Sex hormone- secreting area
Kidney
Medulla
Adrenal
medulla

6. Figure 9.10 Roles of the hypothalamus, adrenal medulla, and adrenal cortex in the stress response.
Short term
More prolonged
Stress
Hypothalamus
Releasing hormones
Nerve impulses
Spinal cord
Corticotropic cells of anterior pituitary
ACTH
Adrenal cortex
Preganglionic sympathetic
fibers
Adrenal
medulla
Mineralocorticoids
Glucocorticoids
Short-term stress response
Long-term stress response
Catecholamines (epinephrine and norepinephrine)
Increased heart rate
Increased blood pressure
Liver converts glycogen to glucose and releases glucose to blood
Dilation of bronchioles
Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity
Increased metabolic rate
Retention of sodium and water by kidneys
Increased blood volume and blood pressure
Proteins and fats converted to glucose or broken down for energy
Increased blood sugar
Suppression of immune system

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Pancreatic Islets
Pancreas
Located in the abdomen, close to stomach
Mixed gland, with both endocrine and exocrine functions
The pancreatic islets (islets of Langerhans) produce hormones
Insulin—produced by beta cells
Glucagon—produced by alpha cells
These hormones are antagonists that maintain blood sugar homeostasis
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8. Figure 9.11a Pancreatic tissue.
Stomach
Pancreas
(a)

9. Figure 9.11b Pancreatic tissue.
Exocrine cells of pancreas
Pancreatic
islets
(b)

10. Figure 9.11c Pancreatic tissue.
Exocrine cells of pancreas
Alpha () cells
Figure 9.11c Pancreatic tissue.
Capillaries
Cord of beta () cells secreting
insulin into capillaries
(c)

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Pancreatic Islets
Insulin
Released when blood glucose levels are high
Increases the rate of glucose uptake and metabolism by body cells
Effects are hypoglycemic
Glucagon
Released when blood glucose levels are low
Stimulates the liver to release glucose to blood, thus increasing blood glucose levels
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12. Uptake of glucose from blood is enhanced in most body cells.
Figure 9.12 Regulation of the blood glucose level by a negative feedback mechanism involving pancreatic hormones.
Tissue cells
Insulin-secreting cells
of the pancreas activated; release insulin into
the blood.
Insulin
Pancreas
Glucose
Glycogen
Blood glucose
falls to homeostatic set point; stimulus for insulin release diminishes.
Elevated blood sugar level
Liver takes up glucose and stores as glycogen.
IMBALANCE
Stimulus
Blood glucose level (e.g., after eating four jelly doughnuts)
BALANCE: Normal blood glucose level
(about 90 mg/100 ml)
Stimulus
Blood glucose level (e.g., after skipping a meal)
IMBALANCE
Blood glucose rises
to homeostatic
set point; stimulus
for glucagon
release diminishes.
Low blood sugar level
Glucagon-releasing cells of pancreas activated; release glucagon into blood.
Glucose
Glycogen
Liver breaks down glycogen stores and releases glucose to the blood.
Liver
Glucagon

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Gonads
Gonads
Produce sex cells
Produce sex hormones
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Gonads
Ovaries
Female gonads located in the pelvic cavity
Produce eggs
Produce two groups of steroid hormones
Estrogens
Progesterone
Testes
Male gonads suspended outside the pelvic cavity
Produce sperm
Produce androgens, such as testosterone
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15. Figure 9.3 Location of the major endocrine organs of the body.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)

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Gonads
Estrogens
Stimulate the development of secondary female characteristics
Mature the female reproductive organs
With progesterone, estrogens also:
Promote breast development
Regulate menstrual cycle
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Gonads
Progesterone
Acts with estrogen to bring about the menstrual cycle
Helps in the implantation of an embryo in the uterus
Helps prepare breasts for lactation
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Gonads
Testes
Produce several androgens
Testosterone is the most important androgen
Responsible for adult male secondary sex characteristics
Promotes growth and maturation of male reproductive system
Required for sperm cell production
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