Download 45 Chemical Signals

Chapter 45 Chemical Signals in Animals
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The endocrine system
and the nervous
system are structurally,
chemically, and
functionally related.
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~ specialized
nerve cells that secrete hormones
Feedback mechanisms ~ negative
and positive (feature that is also
common in the nervous system)
Local regulators: cells adjacent to or near point of
secretion
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Growth factors ~
proteins for cell proliferation
Nitric oxide (NO) ~ (highly reactive& potentially
toxic) neurotransmitter; cell destruction
(bacteria, cancer cells); vessel dilation
Prostaglandins ~
modified fatty acids secreted by placenta
(induce labor) and immune system (fever, pain); also
found in semen (contract smooth muscle in uterus
helping convey sperm to egg.
Mode of Action: Chemical Signaling
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1- Plasma membrane reception
• signal-transduction pathways (neurotransmitters, growth factors, most
hormones)
2- Cell nucleus reception
• steroid hormones, thyroid hormones, some local regulators
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Vertebrate Endocrine System
Page 961
Tropic hormones ~
a hormone that has another
endocrine gland as a target
Hypothalamus: causes release of
hormones produced by posterior
pituitary and regulates anterior pit.
Pituitary gland
Pineal gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Gonads (ovary, testis)
The hypothalamus & pituitary
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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 (pigment
cells)(MSH)
Endorphins~natural ‘opiates’; brain
pain receptors
The pituitary
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The posterior pituitary:
Oxytocin~
uterine and mammary gland
cell contraction
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Antidiuretic (ADH)~
retention of water by kidneys,
increase permiability of epithelium to
water, amplifies water reabsorption
The pineal, thyroid, & parathyroid
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Melatonin~ pineal gland;
biological rhythms
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Thyroid hormones:
Calcitonin~
lowers blood calcium
Thyroxine~
metabolic processes
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Parathyroid (PTH)~
raises blood calcium
The pancreas
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Islets of Langerhans (clusters
of endocrine cells that secrete
hormones)
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Alpha cells:
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Beta cells:
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•glucagon~ raises blood glucose levels
•insulin~ lowers blood glucose levels
Type I diabetes mellitus (insulindependent; autoimmune disorder, attack
mounted on pancreas cells)
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Type II diabetes mellitus (noninsulin-dependent; reduced responsiveness in
insulin targets)
The adrenal glands
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Adrenal medulla (catecholamines-synthesisized from AA
tyrosine): •epinephrine & norepinephrine~ increase basal metabolic rate
(blood glucose and pressure)
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•glucocorticoids (cortisol)~ raise
blood glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+
Adrenal cortex (corticosteroids):
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
Signal Transduction Pathway
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Signal- transduction
pathways allow for small
amounts of a hormone to
have a large effect.
Endocrine System
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How are chemical signals in the body
transmitted from cell to cell?
Chemical signals called transmitters include
amino acids, polypeptides, and gases that
can be received by other cells via a protein
receptor on the surface of the receiving cell
or by entering the cell directly.
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What are some of the sources of the body’s
chemical signals?
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Neurotransmitters from nerve cells.
Endocrine signals from endocrine glands.
How are endocrine signals different from nerve
cell signals?
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Neurotransmitters are usually small, nitrogencontaining compounds that are conveyed from one
specialized nerve cell to another along specific nerve
highways throughout the body and are designed to
elicit immediate responses
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Endocrine signals are usually hormones secreted
from glands that use blood vessels to disperse
their signal molecules, to elicit a slower response.
How are endocrine signals similar to
neurotransmitters?
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Some molecules, such as epinephrine, serve as
both neurotransmitters and endocrine
signals;some specialized nerve cells called
neurosecretory cells are located in the endocrine
glands and secrete hormones into the
bloodstream.
Hormones
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Hormones, the most common class of signal
molecule used by endocrine glands, affect every cell
in the body. How is it possible that very diverse
types of cells can respond to these signals?
While some hormones require surface receptors,
most hormones because they are small and nonpolar, can pass through the cell membranes without
a channel or receptor and proceed directly to a
receptor in the cytoplasm or go into the nucleus to
act as a gene activator.
Trophic Hormones
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Some endocrine signals target other glands,
stimulating them to secrete their own signals.
What is this type of domino effect called?
These signals are called trophic hormones.
Endocrine Review
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Brain: hypothalamus, pituitary, pineal
Pituitary: Anterior
Posterior
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Endorphines
ADH
GH (Growth Hormones)
Oxytocin
ACTH (adrenal cortex
TSH (thyroid stimulating)
PRL (prolactin)
LSH,FSH (gonads)
MSH (Melanocyte cells-melatonin (skin pigment)
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Thyroid
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Parathyroid (PTH)-Increase Ca+
A dramatic drop in calcium would cause convulsive
contractions of skeletal muscles
Adrenal Glands (top of kidneys)- fight or flight
Medulla
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Metabolism (throxine)-metabolism, (calcitonin) decrease
Ca+
norepinephrine and epinephrine increase metabolism,
increase glucose (breakdown of glycogen)& pressure
-Cortex- increase glucose, reabsorption of k+, Na+
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Pancreas
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Alpha cells (glucagon)-increase glucose
Beta cells (insulin) decrease
Gonads- steroids,
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testosterone, estrogens, progestins