Download Stem Cells, Cancer, and Human Health

All Multicellular Organisms Must
Coordinate Their Functions
• The many cells, tissues, and organs in the animal body need
to communicate so that the whole organism can develop
and function effectively
• The endocrine system consists of different types of
secretory cells that release a variety of signaling molecules
called hormones
The Endocrine System
• Animal hormones are
produced by specialized
cells that are often
organized into discrete
organs called endocrine
glands
• Endocrine glands release
hormones into body fluids,
which then carry these
chemical messengers
throughout the body
• Some endocrine cells are
embedded as single cells or
clusters of cells within other
specialized tissues and
organs
The Endocrine System
• The hypothalamus is
responsible for
coordinating the
endocrine system and
integrating it with the
nervous system
• The hypothalamus
contains both neurons
that interact with the
brain and also endocrine
cells that produce
hormones
The Endocrine System
• The hypothalamus
makes releasing and
inhibiting hormones
that direct the
pituitary to release
another set of
hormones
• These hormones from
the pituitary will travel
through the
circulatory system to
regulate the various
endocrine glands.
The Endocrine System
• Hormones are often
distributed through
the body by the
circulatory system
and therefore move
only as fast as blood
is circulated
• Hormones are
effective in small
amounts because
they bind to target
cells with great
specificity and
tenacity
Hormones and their Target Cell
• A hormone released by one cell causes one or
more specific responses in the target cells,
which may lie in more than one type of tissue
• Hormones can act on target cells by binding to
plasma membrane receptors or intracellular
receptors
Hormones and their Target Cell
• A single
hormone can
produce a
diversity of
effects in a
variety of
potential
target cells
Hormonal Signals to the Cell
• Hormonal signals are amplified inside the
target cell and alter key cellular processes
• There are four main categories of cellular
responses produces by a hormonal signal:
– Changes in protein production
– Changes in metabolism
– Changes in the activity of the cytoskeleton
– Changes in plasma membrane transport
Hormonal Signals to the Cell
• Animals usually produce hormones in tiny amounts
measured in micrograms
• When hormone molecules bind to receptors in the target
cell, they set in motion a chain of events that may
activate thousands of protein molecules in that cell
• Through signal amplification, just a few hormone
molecules can have a substantial impact on the whole
body
Hormonal Signals to the Cell
• Signal transduction is
the process in which a
signal received by a
membrane receptor is
relayed within the
cytoplasm to produce
responses from the
target cell
• Notice the
amplification of the
singnal
Hormonal Signals to the Cell
• Some hormones
bind to receptors
on the plasma
membrane
• Others, like
steroids, are able
to cross the plasma
membrane and
deliver the
hormonal message
within the cell
Specific Hormonal Processes we will Cover
Glucose homeostasis
The fight-or-flight response
Growth
Menstruation
Glucose Homeostasis
• Hormones that regulate
homeostasis must act quickly
to maintain a constant
internal environment
• Glucose homeostasis is
controlled by the pancreas
• The pancreas, function as
endocrine glands and also as
exocrine (ducted) glands
• The pancreas contains
clusters of endocrine cells
called islet cells that produce
and release insulin and
glucagon
Glucose Homeostasis
• Insulin and glucagon are hormones
that act in opposite ways to
maintain homeostasis in blood
glucose levels
• Insulin acts on target cells
throughout the body, but especially
in the liver, fat tissue, and skeletal
muscles, signaling these cells to
increase their uptake of glucose
from the blood
• Insulin= into cell out of blood
• Causes decrease blood sugar
• Glucagon= gone from cell into blood
• Causes increased blood sugar
Disruption in Glucose Homeostasis:
Diabetes
• Too much glucose in the blood results in diabetes
• Most cases of type 1 diabetes result from:
– autoimmune damage to the islet cells preventing
insulin production or
– production of a defective form of insulin by the
pancreas
• Type 2 diabetes occurs when:
– too little insulin is produced or
– the receptors on target cells respond poorly to insulin
Short Term Control:
Fight-or-Flight Response
• The adrenals regulate
the fight-or-flight
response
• The adrenal glands are
a pair of endocrine
glands that sit on top
of the kidneys and
release epinephrine
and norepinephrine,
which coordinate our
response to sudden
stress
Short Term Control:
Fight-or-Flight Response
• Epinephrine stimulates glycogen breakdown in liver and
skeletal muscle cells, which raises blood glucose levels
and in turn increases the speed and force with which
the heart contracts
Regulating Long-Term Processes: Growth
• The pituitary gland
produces growth
hormone (GH), which
promotes the growth of
bones and stimulates
increases in muscle
mass
• Too much or too little
GH can have lifelong
consequences on an
individual, resulting in a
variety of conditions
Regulating Long-Term
Processes: Reproduction
• Animals rely on hormones to regulate nearly
all aspects of reproduction
• In humans, hormones influence nearly all
aspects of sexual development and
reproduction, including sperm production in
males and the menstrual cycle of women
Sex Hormones Play a Role in
Sexual Development before Birth
• It is through the action of the
hormones that a fetus develops
into a male or a female
• By the seventh week of the
fetus’s development, the sex
glands, or gonads, are producing
the sex hormones
• These sex hormones signal genes
in their target cells to begin the
process of sexual development
• The gonads of both sexes
produce estrogens,
progestogens, and androgens in
varying amounts
Sex Hormones Play a Role in
Sexual Development before Birth
• Estrogen produces female characteristics, while
progestogens, including progesterone, create a suitable
environment for a developing fetus
• Androgens, such as testosterone, stimulate cells to
develop the characteristics of maleness
Sex Hormones Coordinate
Sexual Maturation at Puberty
• During puberty, the
hypothalamus makes
Gonadotropin Releasing
Hormone (GnRH) that activates
the production of
gonadatropins made in the
pituitary gland
• These gonadatropins,
Luteinizing hormone (LH) and
follicle-stimulating hormone
(FSH) coordinate the
development of sperm in males
and play a role in regulating the
menstrual cycle in females
GnRH
Sex Hormones Coordinate the Menstrual Cycle
• In humans females, individual eggs mature and
are released in a hormone-driven sequence of
events known as the menstrual cycle
• The menstrual cycle is marked by a succession of
hormones that stimulate the release of an egg
and prepare the uterine lining to grow and
thicken in preparation for a potential pregnancy
• Between 40 and 50 years of age, a drop in the
levels of estrogen and progesterone results in
menopause, in which the menstrual cycle ceases
permanently
Sex Hormones Coordinate the Menstrual Cycle
• The menstrual cycle is marked by a succession of
hormones that stimulate the release of an egg and
prepare the uterine lining to grow and thicken in
preparation for a potential pregnancy
Sex Hormones Coordinate the Menstrual Cycle