Download 45-Hormones and the Endocrine System

Hormones and the Endocrine
System
Introduction to Regulatory Systems
Chemical Signals and their Modes of
Action
Vertebrate Endocrine System
Regulatory systems
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Hormone~ chemical signal secreted into
body fluids (blood) communicating
regulatory messages
Target cells~ body cells that respond to
hormones
Endocrine system/glands~ hormone
secreting system/glands (ductless);
exocrine glands secrete chemicals (sweat,
mucus, enzymes) through ducts
Neurosecretory cells~ actual cells that
secrete hormones
Feedback mechanisms ~ negative and
positive
Table 45-1
Table 45-1a
Table 45-1b
Table 45-1c
Table 45-1d
Introduction to Regulatory
Systems
• Nervous system involved with high speed
responses
• Endocrine system is slower and involves the
production, release, and movement of chemical
messages
• specialized nerve cells found within the endocrine
system are called neurosecretory cells
• some chemicals function in both systems-ex.
norepinephrine
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
Two Classes of Vertebrate
Hormones
• Most signal molecules are unable to diffuse
through the plasma membrane (peptides,
proteins, glycoproteins), require a
membrane receptor and signal transduction
pathway
• some molecules can diffuse through the
membrane (steroids, thyroid hormones,
NO), receptors are within the target cells
Fig. 45-3
Water-soluble
Lipid-soluble
0.8 nm
Polypeptide:
Insulin
Steroid:
Cortisol
Amine:
Epinephrine
Amine:
Thyroxine
Vertebrate Endocrine System
• Hypothalamus and pituitary integrate much
of the endocrine system
• includes: hypothalamus, anterior and
posterior pituitary, pineal, thyroid,
parathyroid, pancreas, adrenal, testis, and
ovary
Vertebrate Endocrine System
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Tropic hormones ~
a hormone that has another
endocrine gland as a target
Hypothalamus~pituitary
Pituitary gland
Pineal gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Gonads (ovary, testis)
The hypothalamus & pituitary, I
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Releasing and inhibiting hormones
Anterior pituitary:
Growth (GH)~bones
√gigantism/dwarfism
√acromegaly
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-insulin-dependent; 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
Diabetes
• Two types:
• Type I- Insulin dependent
• Type II-Non-insulin dependent
Fig. 45-11
Pathway
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Example
Stimulus
Low pH in
duodenum
S cells of duodenum
secrete secretin ( )
Endocrine
cell
Blood
vessel
Target
cells
Response
Pancreas
Bicarbonate release
Fig. 45-12-1
Insulin
Beta cells of
pancreas
release insulin
into the blood.
STIMULUS:
Blood glucose level
rises.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Fig. 45-12-2
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level
rises.
Blood glucose
level declines.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Fig. 45-12-3
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
STIMULUS:
Blood glucose level
falls.
Alpha cells of pancreas
release glucagon.
Glucagon
Fig. 45-12-4
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
STIMULUS:
Blood glucose level
falls.
Blood glucose
level rises.
Alpha cells of pancreas
release glucagon.
Liver breaks
down glycogen
and releases
glucose.
Glucagon
Fig. 45-12-5
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level
rises.
Blood glucose
level declines.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
STIMULUS:
Blood glucose level
falls.
Blood glucose
level rises.
Alpha cells of pancreas
release glucagon.
Liver breaks
down glycogen
and releases
glucose.
Glucagon