Chapter 014

The Human Body in Health and Illness, 4th edition

Barbara Herlihy

Chapter 14:Endocrine System

Lesson 14-1 Objectives

• List the functions of the endocrine system.• Define hormone.• Explain negative and positive feedback control

loops as regulators for hormone levels.• Describe the relationship of the hypothalamus

to the pituitary gland.• Describe the location, hormones, and

regulation of the pituitary gland.Copyright © 2011, 2007 by Saunders,

an imprint of Elsevier Inc. All rights reserved.

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Endocrine Glands

• Ductless glands• Secrete hormones• Widely distributed

throughout the body

Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights

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Hormones

• Chemical messengers that influence or control activities of other tissues and organs

• Classification– Proteins (and protein-related substances)– Steroids


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Hormones and their Receptors

• Gland aims hormone at target organs

• Hormone activates receptors– On cell membrane– Within cell nucleus


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Control of Hormonal Secretion

• Feedback control– Negative– Positive

• Biorhythms– Circadian and monthly

• Central nervous system– Psychoneuroendocrinology


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Control by Negative Feedback Loop

• Example: As level of cortisol rises in the blood to needed level, cortisol shuts off further secretion of ACTH.

• As level of cortisol drops, inhibition is relieved.


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Control by Positive Feedback Loop

• A bodily change stimulates further change in the same direction.

• The following are some examples. During labor, pressure of baby’s head on cervix

stimulates release of oxytocin. Oxytocin stimulates uterine contraction, further

increasing pressure on cervix. More oxytocin is released until delivery.


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Hypothalamus and Pituitary Gland

• Hypothalamus controls pituitary function.

• Connected to anterior pituitary through capillaries and to posterior pituitary through tissue extension


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Pituitary Gland: Two Parts

• Anterior pituitary– Adenohypophysis– Controlled by

releasing hormones of hypothalamus

• Posterior pituitary– Neurohypophysis– Extension of

hypothalamusCopyright © 2011, 2007 by Saunders,


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Hormones of Anterior Pituitary

• TSH• ACTH• Growth

hormone• Gonadotropins

– FSH and LH

• Prolactin


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Hormones of Posterior Pituitary

• Oxytocin• ADH


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Lesson 14-2 Objectives

• Identify the major endocrine glands and their hormones.

• Explain the effects of hyposecretion and hypersecretion of the major endocrine glands.


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Thyroid Gland: Hormones

• Follicular cells secrete T3 and T4 into colloid for storage.

• FSH releases T3, T4 into the blood.

• Parafollicular cells secrete calcitonin.


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Thyroid Hormones: Functions

• T3 and T4

– Regulate metabolism– Permit proper functioning of all other hormones– Promote normal maturation of the nervous

system – Promote normal growth and development

• Calcitonin– Helps regulate calcium levels in the blood


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Abnormal Thyroid Secretion

• Hypothyroidism: Deficiency of T3/T4, resulting in a slowed down metabolic rate or myxedema

• Hyperthyroidism: Excess of T3/T4, causing accelerated metabolic rate or Graves’ disease


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Control of T3 and T4 Secretion

Releasing hormone (TRH)

TSH

T3 and T4

Negative feedback loop by T3 and T4


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Thyroid Gland and Iodine

T3 = triiodothyronine

T4 = tetraiodothyronine (thyroxine)

• Iodine essential for synthesis of T3 and T4

• Iodine deficiency causes goiter or enlargement of thyroid gland.– Iodine deficiency interferes with negative

feedback loop


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Four Parathyroid Glands

• Lie along posterior wall of thyroid gland• Are most important regulator of blood calcium• Secrete parathyroid hormone (PTH), which

elevates blood calcium level


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PTH Raises Blood Calcium

• Three mechanisms– Bone

• Resorption

• Kidney– Reabsorbs Ca2+ from

urine

• Intestine– Absorbs dietary Ca2+


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Calcitonin and Blood Calcium

• Thyroid gland secretes calcitonin in response to elevated blood calcium level.

• Calcitonin lowers blood calcium level– By bone by stimulating osteoblastic activity– By kidney by excreting excess calcium

Copyright © 2011, 2007 by Saunders,


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Parathyroid Glands: Abnormal Secretion

• Hyposecretion: Hypocalcemic tetany, causing carpal spasm

• Hypersecretion: Hypercalcemia

• “Bones, stones, moans, and groans”


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Adrenal Glands

• Located above kidneys • Adrenal medulla

– Inner region – Secretes catecholamines

• Adrenal cortex– Outer region – Secretes steroids


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Adrenal Glands: Medulla and Cortex


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Adrenal Medulla

• Extension of sympathetic nervous system• Fight-or-flight response

– Increases heart rate and blood pressure– Mobilizes body for emergencies

• Catecholamines– Epinephrine– Norepinephrine


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Adrenal Cortex: Steroids

• Sugar: Glucocorticoids– Cortisol, most important

• Salt: Mineralocorticoids– Aldosterone

• Sex: Sex hormones– Testosterone, most important


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Functions of Steroids

• Cortisol affects metabolism of carbohydrate, protein, and fat.

• Aldosterone stimulates the kidney’s reabsorption of salt and water and excretion of potassium.

• Testosterone exerts virilizing effects.


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Abnormal Secretion of Steroids

• Hyposecretion – Addison’s disease– Acute adrenal cortical insufficiency

• Hypersecretion– Cushing’s syndrome– Excess use of steroids as drug (prednisone) will

cause cushingoid appearance.


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Cortisol: Negative Feedback Loop

Releasing hormone

ACTH

Cortisol

Negative feedback by cortisol


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Pancreas• Across abdomen• Islets of Langerhans

secrete hormones.• Hormones

Insulin glucoseGlucagon glucose


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Pancreas Regulates Blood Glucose

• Blood glucose level rises, pancreas secretes insulin

• Blood glucose level falls, pancreas secretes glucagon


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Insulin in Normal Metabolism

• Carbohydrate– Increased transport of glucose into cell– Use of glucose as fuel– Storage of excess glucose as glycogen

• Protein– Stimulation of protein synthesis

• Fat– Stimulation of fatty acid synthesis


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Deficiency of Insulin

• Carbohydrate– Decreased transport of glucose from blood to cell– Decreased utilization of glucose as fuel

• Protein– Conversion of protein to glucose: gluconeogenesis

• Fats– Formation of ketone bodies: Acetone and

ketoacids


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Diabetes Mellitus: Insulin Deficiency or Ineffectiveness

Hyperglycemia• Glucosuria• Polyuria/polydipsia• Dehydration• Low blood volume• Shock

Rapid Fatty Acid Catabolism• Ketone bodies• Acetone (fruity odor to

breath)• Ketoacids• Kussmaul respirations• Diabetic ketoacidosis


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Hormones and Blood Glucose

• Insulin: Only hormone to lower blood glucose level

• All other hormones raise blood glucose level.– Glucagon– Cortisol– Epinephrine– Growth hormone


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Other Glands• Gonads

– Testes secrete testosterone.– Ovaries secrete progesterone and estrogen.

• Thymus – Secretes thymosins – Affects immune function

• Pineal – Secretes melatonin– Affects biological clock

• Adipose tissue secretes unhealthy cytokines.Copyright © 2011, 2007 by Saunders,


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Other Hormones

• Organ-specific hormones– Secreted by organs such as heart, kidney, digestive

organs

• Prostaglandins– Secreted by most tissues– Most act locally– Play a role in regulation of smooth muscle

contraction, inflammatory response, and pain


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Chapter 014

Health & Medicine

Transcript of Chapter 014