Download CH 45 Chemcial Signals2013

 Chapter
45
~Hormones and
the Endocrine
System
Endocrine and Nervous System
Regulation
 Nervous
-
-
system
Electrical signals
Fast acting for immediate response
 Endocrine
-
system
Hormones
Slower and longer acting
Negative Feedback Loops
The hormonal
response reduces
the initial stimulus
 Prevents
overreaction of the
system and
maintains
homeostasis
(sugar levels in
the blood)

Positive Feedback Loops
Reinforces
the stimulus
 Creates a
greater
response

Regulatory systems





Hormone~ chemical signal secreted into body
fluids (blood) communicating regulatory
messages
Target cells~ body cells that respond to
hormones
Endocrine glands~ hormone secreting glands;
ductless, travel through interstitial fluid or
circulatory system
Exocrine glands secrete chemicals through
ducts; tears, mucus, saliva
Neurosecretory cells~ actual cells that
secrete hormones
Water and Fat Soluble Hormones


Water soluble- faster
acting, reversible, protein
based, removed from
blood quickly– insulin,
ADH: attaches to cell
membrane
Fat soluble hormonesslower acting and longer
lasting, irreversible,
stimulated by a trophic
hormone – steroids:
enters the cell
Paracrine signaling
Cell to cell
communication
 Induces a change in
nearby cells
 Travel in short
distances
 Example-Hedgehog
proteins

Local regulators



Nitric oxide (NO)`
vessel dilation, increase
blood flow for more O2
Growth factors ~
proteins for cell
proliferation
Prostaglandins~
immune, reproduction,
blood clotting
Local Regulators



Histamine- triggers
dilation and increased
permeability in the
immune response
Interleukins-a cytokine
protein that activates
lymphocytes
Retinoic acid- necessary
for vision and bone growth
(anti aging hormones in
cosmetics)
Trophic Hormones
Growth effect on
the gland it
stimulates
 It is released in the
bloodstream to
travel to the target
organ or gland

The pancreas- feedback for glucose


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+
Epinephrine Release
Fight or flight
 Stress hormone
 Increases blood
pressure
 Increases diameter
of blood vessels

The gonads

Steroid hormones:
precursor is cholesterol

androgens
(testosterone)~ sperm
formation; male secondary sex
characteristics;

estrogens
(estradiol)~uterine lining growth;
female secondary sex
characteristics

Progestins
(progesterone)~uterine lining
growth
Gonadotropic Hormones



Stimulates gonads
FSH- follicle
stimulating hormone
(in women regulates
menstruation and
ovulation)
LH- luteinizing
hormone (ovulation in
women and production
of testosterone in men)

Arthropods have extensive endocrine
systems regulating molting in insects and
crustaceans.

The regulation of molting in insects.


Neurosecretory cells in the brain produce brain
hormone (BH), which regulates the secretion of
ecdysone.
Ecdysone also promotes the development of
adult features and molting
 Juvenile
hormone (JH) promotes the
retention of larval characteristics.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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