Download Chapter 45 Presentation-Hormones and the Endocrine System

Chapter 45
Hormones and the Endocrine
System
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Internal Communication
 Animals have 2 systems of internal
communication and regulation:
 1. The nervous system.
 2. The endocrine system.
1. The Nervous System
 The nervous system is the
pathway of communication
involving high speed electrical
signals.
 There are two portions to it:
 CNS
 PNS
Nervous Tissue
 Senses stimuli and transmits
nerve impulses from one part of
the body to the next.
 The neuron is the functional unit.
 Axon
 Dendrite
What is a nerve?—Form
Fitting Function
 Near its end, an axon divides into
several branches, each ending in a
synaptic terminal.
Copyright ©2005 Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.
What is a nerve?—Form
Fitting Function
 The synapse is
the site of
communication
between one
nerve and
another.
http://biologyclass.neurobio.arizona.edu/images/synapse2.jpg
What is a nerve?—Form
Fitting Function
 Neurotransmitters
transmit the
signal from a presynaptic cell to a
post-synaptic
neuron.
http://biologyclass.neurobio.arizona.edu/images/synapse2.jpg
Synaptic
Transmission
http://biologyclass.neurobio.arizona.edu/images/synapse2.jpg
 The
transmission of
information from
the presynaptic
neuron to the
postsynaptic
neuron due to
an action
potential can
trigger short and
long term
changes—
membrane
How Do Nerve Systems
Work?
 Information
processing by the
nervous system
consisting of 3
stages:
 1. Sensory input
 2. Integration
 3. Motor output
How Do Nerve Systems
Work?
 These three stages
are handled by
specialized neurons.
 1.
How Do Nerve Systems
Work?
Sensory
neurons transmit
information from
sensors that detect
external stimuli
and internal
conditions.
 These receptors
are usually
specialized neurons
or epithelial cells.
How Do Nerve Systems
Work?
 2. Interneurons
integrate and
analyze sensory
input. They
allow the spinal
cord to work
independently of
the brain and
provide reflexes.
How Do Nerve Systems
Work?
 This reflex is an
automatic
response to
certain stimuli
and acts to
protect the body
from harm—think
about touching
something hot.
How Do Nerve Systems
Work?
 2. These
interneurons
provide inhibitory
signals to
opposing muscles
allowing the reflex
to produce the
desired result.
How Do Nerve Systems
Work?
 The CNS also
provides the
integrative
power for the
organism—
specifically the
brain.
How Do Nerve Systems
Work?
 3. Motor output
leaves the CNS
via motor
neurons which
communicate
with effector cells
eliciting a change.
How Do Nerve Systems
Work?
 These motor
neurons can be
due to voluntary
control, or
involuntary
control.
2. The Endocrine System
 The endocrine system is all of the
animal’s hormone secreting cells.
 The endocrine system coordinates
a slow, long-lasting response.
Endocrine Glands
 Endocrine glands are hormone
secreting organs.
 They are ductless glands.
 Their product is secreted into
extracellular fluid and diffuses into
circulation.
Endocrine and Nervous
Systems
 It is convenient to think of the
nervous system and the endocrine
as separate.
 They are actually very closely
linked.
 Neurosecretory cells are
specialized nerve cells that release
hormones into the blood.
Neurosecretory Cells
 The hypothalamus and the
posterior pituitary gland contains
neurosecretory cells.
 These produce neurohormones
which are distinguishable from
endocrine hormones.
 Some hormones serve as both
endocrine hormones and
neurotransmitters.
Neurosecretory Cells
 They can stimulate a response, or
they can induce a target cell to
elicit a response.
 For example, a suckling infant and
oxytocin release is an example.
Biological Control Systems
 Recall,
 These are comprised of a receptor/sensor
which detects a stimulus and sends
information to a control center that controls
an effector.
 The control center processes the
information and compares it to a set point.
 The control center sends out processed
information and directs the response of the
effector.
3 General Hormonal
Pathways
 1. A simple endocrine pathway.
 2. A simple neurohormone
pathway.
 3. A simple neuroendocrine
pathway.
1. A Simple Endocrine
Pathway
 A stimulus elicits a
response on an
endocrine cell
causing a hormone
release.
 The hormone
diffuses into the
blood where it
reaches a target
Copyright ©2005 Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.
1. A Simple Endocrine
Pathway
 For example:
 A low glucose level in the
blood stimulates the
pancreas to release
glucagon.
 Glucagon acts on liver
cells to release glycogen.
 Glycogen breaks down
into glucose and gets into
the blood.
Copyright ©2005 Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.
2. Simple Neurohormone
Pathway
 In the simple
neurohormone pathway,
a stimulus travels via a
sensory neuron to the
hypothalamus/posterior
pituitary gland.
 Neurosecretory cells here
release hormones into
the blood.
 These hormones travel
to the target cells and
Copyright ©2005 Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.
2. Simple Neurohormone
Pathway
 For example:
 A suckling infant’s
stimulation is sent via a
sensory neuron to the
hypothalamus/posterior
pituitary where oxytocin
is made and released
into the blood.
 The hormones travel to
the smooth muscle in
the breast which
responds by contracting
and releasing milk.
Copyright ©2005 Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.
3. A Simple
Neuroendocrine Pathway
 A stimulus sends the
signal to the
hypothalamus via a
sensory neuron.
 The neurosecretory cells
of the hypothalamus
release hormones into
the blood.
 These act on endocrine
cells to release different
hormones into the
Copyright ©2005 Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.
3. A Simple Neuroendocrine
Pathway
 For example:
 Neural and hormonal signals tell
the hypothalamus to secrete
prolactin releasing hormone.
 This hormone travels through
the blood to the anterior
pituitary which releases
prolactin.
 Prolactin travels through the
blood to the mammary glands
stimulating milk production.
Copyright ©2005 Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.
Positive and Negative
Feedback
 Recall,
 Positive feedback acts to reinforce
the stimulus. It leads to a greater
response.
 Negative feedback acts to reduce
the response of the stimulus.
Molecules Functioning as
Hormones
 There are 3 major classes of
molecules that function as
hormones:
 1. Proteins/peptides-water soluble.
 2. Amines-water soluble.
 3. Steroids-not water soluble.
Key Events
 There are 3 key events involved in
signaling:
 1. Reception-is when the signal binds to
the receptor protein in or on the target cell.
 Receptors can be inside or outside the cell.
 2. Signal transduction-signal binds and
triggers events within the cell (cascade
events).
 3. Response-changes a cell’s behavior.
Signal Transduction
 Receptors for most
water soluble
proteins are
embedded in the
plasma
membrane.
 Binding of a
hormone initiates
a signal
transduction
Signal Transduction
 The pathway is a series of changes
where cellular proteins convert an
extracellular chemical signal into
an intracellular response.
 Examples:
 Activation of an enzyme
 Uptake or secretion of a specific molecule
 Rearrangement of a cytoskeleton
Signal Transduction
 The signals can
activate proteins that
can act to directly or
indirectly regulate
transcription of
certain genes.
 Hormones can cause
a variety of
responses in target
cells with different
receptors.
Water Soluble Hormones
 Most water soluble hormones have
receptors embedded in the
membrane.
 Surface receptor proteins activate
proteins in the cytoplasm which
then move into the nucleus and
regulate transcription.
Epinephrine ExampleWater Soluble Hormone
 Liver cells and smooth muscle of
blood vessels supplying skeletal
muscle contain -type epinephrine
receptors.
Epinephrine ExampleWater Soluble Hormone
 Smooth muscle of
intestinal blood
vessels contain  type receptors.
 The tissues
respond
differently to
epinephrine.
 Increased blood flow
and glucose to the
skeletal muscles.
Lipid Soluble Hormone
 Lipid soluble hormones
have their receptors
located inside of the cell.
Either in the cytoplasm
or the nucleus.
 Entrance of the signal
and binding of the signal
to the receptor initiates
the signal transduction
pathway.
 Binding to DNA stimulates
transcription of genes.
 mRNA produced is translated
Estrogen Example-Lipid
Soluble Hormone
 Estrogen induces cells within the
female bird’s reproductive system
to make large amounts of
ovalbumin.
Paracrine Signaling
 Neighboring cells signal local
regulators to convey signals between
these neighboring cells.
 Neurotransmitters, cytokines, and
growth factors are all examples of
local regulators.
Paracrine SignalingExample
 Nitric oxide (NO).
 When blood O2 levels fall,
endothelial cells in the blood
vessel walls synthesize and
release NO.
 NO activates an enzyme that
relaxes neighboring smooth
muscle.
 This results in the dilation of blood
Endocrine Control
 The hypothalamus
integrates the
vertebrates’ nervous
and endocrine
systems.
 It is found on the
underside of the brain.
 It receives information
from nerves throughout
the body and brain.
 It initiates the
appropriate endocrine
signals for varying
The Hypothalamus
 Contains 2 sets of
neurosecretory
cells.
 The secretions from
these cells are
stored in or
regulate the
activity of the
pituitary gland.
The Pituitary
 The pituitary gland has 2 parts:
the anterior and the posterior.
The Anterior Pituitary
Gland
 It is regulated by hormones produced by
neurosecretory cells in the hypothalamus.
 Some inhibit hormone release, others stimulate it.
 The adenohypophysis consists of endocrince cells
that make and secrete at least 6 different hormones.
 Many of them target and stimulate endocrine glands.
The Anterior Pituitary
Gland
 FSH-stimulates production of ova and
sperm.
 LH-stimulates ovaries and testes.
 TSH-stimulates the thyroid gland.
 ACTH-stimulates production and
secretion of the hormones of the
adrenal cortex.
 MSH-stimulates concentration of
melanin in skin.
 Prolactin-stimulates mammary gland
The Posterior Pituitary
Gland
 The neurohypophysis is
an extension of the
hypothalamus.
 It stores and secretes 2
hormones: ADH and
oxytocin.
 ADH acts on the kidneys
increasing H2O retention.
 Oxytocin signals uterine
muscle contraction and
mammary gland excretion of
milk.
The Thyroid Gland
 The thyroid produces 2 hormones.
 Triiodothyroxine (T3)
 Thyroxin (T4)
 In mammals, T4 is converted to
T3 by target cells.
 T3 is mostly responsible for the
cellular response.
The Thyroid Gland
 The thyroid is crucial to development.
 It is required for normal functioning of
bone-forming cells.
 It promotes branching of nerves in
utero.
 It helps skeletal growth and mental
development.
 It helps maintain muscle tone,
digestion, reproductive functions,
The Thyroid Gland
 The thyroid
creates
calcitonin.
 It works in
conjunction with
the parathyroid
to maintain
calcium
homeostasis.
Parathyroid Hormone
 Released by the
parathyroid gland
in response to low
blood calcium
levels.
 PTH induces the
breakdown of
osteoclasts.
 Ca2+ is then
released into the
blood.
 PTH stimulates
Parathyroid Hormone
 PTH also promotes the conversion
of vitamin D into its active form.
 The active form of vitamin D acts
on the intestines stimulating the
uptake of Ca2+ from food.
 When Ca2+ gets above a certain
setpoint, it promotes the release
of calcitonin which opposes the
effects of PTH lowering blood Ca2+
levels.
Homeostasis
 Homeostatic mechanisms
moderate changes in internal
environments and have 3
functional components:
 1. A receptor
 2. A control center
 3. An effector
The Receptor
 Detects a change in the internal
environment of an animal.
 Example:
Body temperature.
The Control Center
 Processes the information it
receives and directs an
appropriate response.
 Example: Brain.
The Effector
 The effector displays the
appropriate response.
 Example: Shivering, dilation or
constriction of blood vessels.
For Example:
 The regulation of room temperature.
 The control center is the thermostat
and it contains a receptor called the
thermometer.
 When the temp falls below a set
point, it switches the heater (the
effector) on.
 When the thermometer senses the
temp is above the set point, it
switches the heat off--negative
feedback.
Negative Feedback
 Occurs when the variable being
monitored counteracts any further
change in the same direction.
 There are only slight variations
above and below the set point in a
negative feedback system.
 Most homeostatic mechanisms in
an animal operate under this
principle.
Positive Feedback
 On the other hand, positive
feedback occurs when a change in
an environmental variable triggers
mechanisms that amplify the
change.
 For example:
 During childbirth, the head against the
uterine wall stimulates more
contractions in the uterus.
 Positive feedback completes childbirth.
Thermoregulation
 This is the process by which animals
maintain an internal temperature
within a tolerable range.
 This ability is critical to survival
because enzyme function and
membrane permeability is
dramatically affected by large
changes in temperature.
Heat Exchange
 Endotherms and ectotherms use 4
modes of heat exchange:
 1. Conduction
 2. Convection
 3. Radiation
 4. Evaporation
Thermoregulatory
Functions
 Thermoregulators function by
balancing heat loss with heat gain.
 There are 5 general categories to
assist with this:
 1. Insulation
 2. Circulatory Adaptation
 3. Evaporative Cooling
 4. Behavioral Responses
 5. Adjusting Metabolism
1. Insulation
 Fat, hair, and/or feathers help to
reduce heat flow between the
organism and the surroundings.
 The integumentary system in
mammals acts as this insulating
layer.
2. Circulatory Adaptations
 Vasodilation and vasoconstriction
work together to transfer body
heat form the core to the
surroundings.
 Vasodilation--vessels get larger.
 Vasoconstriciton--vessels get smaller.
3. Evaporative Cooling
 Many animals have structural
adaptations that enable them to
take advantage of evaporation as
a way of controlling body
temperature.
 For Example: Sweat glands, panting,
and mucous secretions.
4. Behavioral Adaptations
 Behavioral responses are used by
endotherms and ectotherms as a
means to control body
temperature.
 Basking in the sun
 Migration
 Hibernation
5. Adjusting Metabolism
 There are a variety of ways by
which animals can control their
body temperature by changing
their metabolic activity.
 In some mammals, hormones can
stimulate mitochondria to
generate heat instead of ATP-non-shivering thermogenesis.
5. Adjusting Metabolism
 In other mammals, a layer of
brown fat is found in the neck
region and is specialized in rapid
heat production.
 Some female pythons can increase
their body temperature when
incubating eggs.
5. Adjusting Metabolism
 Humans have nerve cells
concentrated in the hypothalamus
to control thermoregulation.
 These nerve cells are grouped
together and function as a
thermostat regulating mechanisms
that increase or decrease heat
loss.
Pancreas
 The pancreas is both an endocrine
and a exocrine gland.
 Exocrine-releases secretions into
ducts.
 Endocrine-secretions diffuse into
bloodstream.
 Islets of Langerhans are scattered
throughout the exocrine portion of
the pancreas.
Pancreas
 Each islet contains  -cells and -
cells.

 -cells produce glucagon.

-cells produce insulin.
 Insulin and glucagon oppose each
other and regulate the concentration
of glucose in the blood.
Blood Glucose
 Glucagon gets
released when
blood glucose falls
below a setpoint.
 Insulin gets
released when
blood glucose is
elevated.
 Insulin stimulates
most cells to take
up glucose from
the blood.
Diabetes Mellitus
 Diabetes is an endocrine disorder
caused by a deficiency in insulin or
decreased response to insulin.
 There are 2 types:
 Type I-insulin dependent.
 Type II-non-insulin dependent.
Type I Diabetes
 Insulin dependent. It’s an
autoimmune disease resulting in
the destruction of the body’s cells.
 The pancreas can’t produce insulin
and the person requires insulin
injections.
Type II Diabetes
 Non-insulin dependent.
 It is caused by a reduced
responsiveness of the cells to
insulin.