Endocrine System
Chapter 11
Communication Within the Body
• Nervous System: electrochemical signals
• Endocrine System: involves hormones
(chemicals) released by glands
Fig11.01
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Nerve impulse
Neuron
transmits
nerve
impulse
Neurotransmitter
released into
synaptic cleft
Postsynaptic
cell responds
(a)
Glandular
cells secrete
hormone into
bloodstream
(b)
Bloodstream
Target cells
(cells with hormone
receptors) respond
to hormone
Hormones have no
effect on other cells
General Overview
• Hormones are released into bloodstream
• Eventually, they act on target cells
Types of Glands
• Exocrine (secretes products into ducts)
– Sweat, sebaceous glands
• Endocrine (secretes products into body fluids
to affect target cells)
Specificity
• Hormones can only signal target cells with
receptors specific to them
Functions
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•
•
•
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Regulate metabolism
Control reaction rates
Transport substances across membranes
Regulate water/electrolyte balances
Reproduction, development, growth
Major Endocrine Glands
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•
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•
•
Pituitary
Thyroid
Parathyroid
Adrenal
Pancreas
Pineal
Reproductive (testes, ovaries)
Kidneys
Thymus
Hypothalamus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hypothalamus
Pituitary gland
Parathyroid gland
Pineal gland
Thyroid gland
Thymus
Adrenal gland
Kidney
Pancreas
Ovary
(in female)
Testis
(in male)
Control of Hormone Secretions
• Negative Feedback: as hormone levels rise,
glands are inhibited from releasing more
hormones
• As hormones in the blood decrease, this
inhibition stops and more hormone is released
Control of Endocrine Secretion
• Hypothalamus hormones control the pituitary
gland
• Link between the nervous system and
endocrine system
• Negative Feedback
Pituitary Gland
• Anterior and Posterior portions
• Controlled by hypothalamus (nerve impulses or hormones)
• Releases:
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1.
2.
3.
4.
5.
6.
7.
8.
Growth Hormone (GH)
Prolactin (PRL)
Thyroid-Stimulating Hormone (TSH)
Adrenocorticotropic Hormone
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Antidiuretic Hormone (ADH)
Oxytocin (OT)
Growth Hormone (GH)
• Signals cells to grow and divide
• Increases rate of carb/fat/amino acid usage by
cells
• Disorders-dwarfism, gigantism, acromegaly
Antidiuretic Hormone (ADH)
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•
•
•
Regulates water concentration in body
Diuretic: increases urine production
Antidiuretic: decreases urine formation
ADH lowers amount of water excreted by kidneys
• Dehydration – more ADH secreted; less urine
• Drinking too much water – less ADH secreted;
more dilute urine excreted
Applications
• Alcohol
– Lowers ADH
– What will happen?
• Diabetes Insipidus
– Lowered ADH production/release
– Due to tumor or damage
– 25-30 liters of dilute urine per day
Prolactin and Oxytocin
• Childbirth
• Milk production and secretion
• Uterine contractions
Thyroid Gland
• Two thyroid hormones: thyroxine (T4),
triiodothryonine (T3)
– Regulate metabolism
• Controlled by TSH (from pituitary)
• Calcitonin hormone: regulates calcium and
phosphate levels in the blood
– Calcium levels go up, causes calcitonin to go up
– Calcitonin inhibits osteoclasts and increases kidney
secretion of calcium
Disorders
• Hyperthyroidism
• Hypothyroidism
Parathyroid Gland
• Parathyroid Hormone (PTH)
• Increase blood calcium concentration,
decreases blood phosphate
• Inhibits blasts, stimulates clasts
Adrenal Glands
• Epinephrine/Norepinephrine: increase heart
rate, force of cardiac muscle contraction,
breathing rate, blood glucose level
• Flight or fight responses
• Which part of the nervous system do you
think is closely related to these glands?
Other adrenal hormones
• Aldosterone: regulates electrolytes
• Cortisol: increases blood glucose
– Important between meals
• Androgens: supplemental sex hormones
Pancreas
• Glucagon: raises blood glucose
• Insulin: lowers blood glucose
Glucose Loop
Other glands
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Pineal: secretes melatonin; “biological clock”
Thymus: immune system
Ovaries: estrogen, progesterone
Testes: testosterone