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Lecture
Date _______
• Chapter 45
• Chemical Signals in
Animals
Regulatory systems
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Hormone
– chemical signal secreted into body
fluids (blood) communicating
regulatory messages
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Target cells
– body cells that respond to
hormones
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Endocrine system/glands~
– hormone secreting system/glands
(ductless); exocrine glands
secrete chemicals (sweat, mucus,
enzymes) through ducts
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Neurosecretory cells
– actual cells that secrete hormones
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Feedback mechanisms
– negative and positive
Local regulators: cells adjacent to or near point of
secretion
• Growth factors
– proteins for cell proliferation
• Nitric oxide (NO)
– neurotransmitter; cell destruction; vessel
dilation
• Prostaglandins
– modified fatty acids secreted by placenta and
immune system; also found in semen
Mode of Action: Chemical
Signaling
• 1- Plasma membrane reception
– signal-transduction pathways (neurotransmitters, growth factors,
most hormones)
• 2- Cell nucleus reception
– steroid hormones, thyroid hormones, some local regulators
Vertebrate Endocrine System
• Tropic hormones
– a hormone that has
another endocrine gland as
a target
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Hypothalamus~pituitary
Pituitary gland
Pineal gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Gonads (ovary, testis)
The hypothalamus & pituitary, I
• Releasing and inhibiting hormones
• Anterior pituitary:
– Growth (GH)~bones
• gigantism/dwarfism
• acromegaly
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Prolactin (PRL)~mammary glands; milk production
Follicle-stimulating (FSH) &
Luteinizing (LH) ~ ovaries/testes
Thyroid-stimulating (TSH) ~ thyroid
Adrenocorticotropic (ACTH) ~ adrenal cortex
Melanocyte-stimulating (MSH)
Endorphins~natural ‘opiates’; brain pain receptors
The pituitary, II
• The posterior
pituitary:
• Oxytocin
– uterine and mammary
gland cell contraction
• Antidiuretic (ADH)
– retention of water by
kidneys
The pineal, thyroid, & parathyroid
• Melatonin
– pineal gland; biological rhythms
• Thyroid hormones:
– Calcitonin - lowers blood calcium
– Thyroxine - metabolic processes
• Parathyroid (PTH)
– raises blood calcium
The pancreas
• Islets of Langerhans
• Alpha cells:
– Glucagon - raises blood glucose levels
• Beta cells:
– Insulin - lowers blood glucose levels
• Type I diabetes mellitus (insulin-dependent;
autoimmune disorder)
• Type II diabetes mellitus (non-insulindependent; reduced responsiveness in insulin targets)
The adrenal glands
• Adrenal medulla (catecholamines):
– epinephrine & norepinephrine - increase basal metabolic rate (blood
glucose and pressure)
• Adrenal cortex (corticosteroids):
– glucocorticoids (cortisol) - raise blood glucose
– mineralocorticoids (aldosterone) - reabsorption of Na+ and K+
The gonads
• Steroid hormones: precursor is
cholesterol
• Androgens (testosterone)
– sperm formation; male secondary sex characteristics;
gonadotropin
• Estrogens (estradiol)
– uterine lining growth; female secondary sex
characteristics; gonadotropin
• Progestins (progesterone)
– uterine lining growth