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Chapter 26
Hormones and the
Endocrine System
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
Chemical signals coordinate body functions
 The endocrine system
– consists of all hormone-secreting cells and
– works with the nervous system in regulating body
activities.
 The nervous system also
– communicates,
– regulates, and
– uses electrical signals via nerve cells.
© 2012 Pearson Education, Inc.
Chemical signals coordinate body functions
 Comparing the endocrine and nervous systems
– The nervous system reacts faster.
– The responses of the endocrine system last longer.
© 2012 Pearson Education, Inc.
Chemical signals coordinate body functions
 Hormones are
– chemical signals,
– produced by endocrine glands,
– usually carried in the blood, and
– responsible for specific changes in target cells.
 Hormones may also be released from specialized
nerve cells called neurosecretory cells.
© 2012 Pearson Education, Inc.
Figure 26.1A
Secretory vesicles
Endocrine
cell
Hormone
molecules
Blood
vessel
Target cell
Nerve
cell
Nerve
signals
Neurotransmitter
molecules
Nerve cell
Hormones affect target cells using two main
signaling mechanisms
 Two major classes of molecules function as
hormones in vertebrates.
– The first class includes hydrophilic (water-soluble),
amino-acid-derived hormones. Among these are
– proteins,
– peptides, and
– amines.
– The second class of hormones are steroid hormones,
which include small, hydrophobic molecules made from
cholesterol.
© 2012 Pearson Education, Inc.
Hormones affect target cells using two main
signaling mechanisms
 Hormone signaling involves three key events:
– reception,
– signal transduction, and
– response.
© 2012 Pearson Education, Inc.
Figure 26.2A_s1
Water-soluble
hormone
1
Target cell
Nucleus
Interstitial fluid
Receptor
protein
Plasma
membrane
Figure 26.2A_s2
Water-soluble
hormone
1
Interstitial fluid
Receptor
protein
Plasma
membrane
Target cell
2
Signal
transduction
pathway
Relay
molecules
Nucleus
Figure 26.2A_s3
Interstitial fluid
Water-soluble
hormone
Receptor
protein
1
Plasma
membrane
Target cell
2
Signal
transduction
pathway
Relay
molecules
3
Cytoplasmic
response
Cellular responses
or
Gene regulation
Nucleus
Hormones affect target cells using two main
signaling mechanisms
 A steroid hormone can
– diffuse through plasma membranes,
– bind to a receptor protein in the cytoplasm or nucleus,
and
– form a hormone-receptor complex that carries out the
transduction of the hormonal signal.
© 2012 Pearson Education, Inc.
Figure 26.2B_s1
Interstitial fluid
Steroid
hormone
1
Target cell
Nucleus
Figure 26.2B_s2
Interstitial fluid
Steroid
hormone
1
Target cell
2
Receptor
protein
Nucleus
Figure 26.2B_s3
Interstitial fluid
Steroid
hormone
1
Target cell
2
Receptor
protein
Nucleus
DNA
3
Hormonereceptor
complex
Figure 26.2B_s4
Interstitial fluid
Steroid
hormone
1
Target cell
2
Receptor
protein
Nucleus
3
Hormonereceptor
complex
DNA
4
Transcription
mRNA
New
protein
Cellular response:
activation of a gene and synthesis
of new protein
Figure 26.3
Thyroid gland
Hypothalamus
Pituitary gland
Parathyroid glands
(embedded within
thyroid)
Thymus
Adrenal glands
(atop kidneys)
Pancreas
Ovaries
(female)
Testes
(male)
The hypothalamus, which is closely tied to the
pituitary, connects the nervous and endocrine
systems
 The hypothalamus
– blurs the distinction between endocrine and nervous
systems,
– receives input from nerves about the internal conditions of
the body and the external environment,
– responds by sending out appropriate nervous or
endocrine signals, and
– uses the pituitary gland to exert master control over the
endocrine system.
© 2012 Pearson Education, Inc.
Figure 26.4A
Brain
Hypothalamus
Posterior pituitary
Anterior pituitary
Bone
Figure 26.4B
Hypothalamus
Neurosecretory
cell
Hormone
Posterior
pituitary
Blood
vessel
Oxytocin
Uterine muscles
Mammary glands
Anterior
pituitary
ADH
Kidney
tubules
Figure 26.4C
Neurosecretory
cell of hypothalamus
Blood
vessel
Releasing hormones
from hypothalamus
Endocrine cells of
the anterior pituitary
Pituitary hormones
TSH
ACTH
FSH
and
LH
Prolactin
(PRL)
Growth
hormone
(GH)
Thyroid
Adrenal
cortex
Testes or
ovaries
Mammary
glands
(in mammals)
Entire
body
Endorphins
Pain
receptors
in the brain
Figure 26.4E
Hypothalamus
Inhibition
TRH
Anterior
pituitary
TSH
Thyroid
Thyroxine
Inhibition
The thyroid regulates development and
metabolism
 Iodine deficiency can produce a goiter, an
enlargement of the thyroid. In this condition,
– the thyroid gland cannot synthesize adequate amounts of
T4 and T3, and
– the thyroid gland enlarges.
© 2012 Pearson Education, Inc.
Figure 2.2A
Figure 26.5B
No inhibition
Hypothalamus
TRH
Anterior
pituitary
No inhibition
TSH
No iodine
Thyroid
Thyroid grows
to form goiter
Insufficient
T4 and T3
produced
Hormones from the thyroid and parathyroid
glands maintain calcium homeostasis
 Blood calcium level is regulated by antagonistic
hormones each working to oppose the actions of
the other hormone:
– calcitonin, from the thyroid, lowers the calcium level in
the blood, and
– parathyroid hormone (PTH), from the parathyroid
glands, raises the calcium level in the blood.
© 2012 Pearson Education, Inc.
Figure 26.6
8
7
Calcitonin
Thyroid
gland
releases
calcitonin
Stimulates
Ca2 deposition
in bones
Reduces
Ca2 reabsorption
in kidneys
9
6
Stimulus:
Rising
blood Ca2
level
(imbalance)
Blood Ca2 falls
Ca2
level
Homeostasis: Normal blood
calcium level (about 10 mg/100 mL)
Ca2
level
Stimulus:
Falling
blood Ca2
level
(imbalance)
1
Blood Ca2 rises
Parathyroid
glands
release parathyroid
hormone (PTH)
5
Stimulates
Ca2 release
from bones
2
3
PTH
Active
vitamin D
Increases
Ca2 uptake
in intestines
4
Increases
Ca2
reabsorption
in kidneys
Parathyroid
gland
Figure 26.6_1
Ca2
level
Homeostasis
Ca2
level
Stimulus:
Falling
blood
Ca2 level
Blood Ca2 rises
1
Release of
parathyroid
hormone
5
Ca2
release
Ca2
uptake
Active
vita- Ca2
min D reabsorp4
tion
3
PTH
2
Figure 26.6_2
8
7
Calcitonin
Thyroid
gland
releases
calcitonin
Stimulates
Ca2
deposition
Reduces Ca2
reabsorption
9
6
Stimulus:
Rising
blood Ca2
level
Blood Ca2 falls
Ca2
level
Homeostasis
Ca2
level
Pancreatic hormones regulate blood glucose levels
 The pancreas secretes two hormones that control
blood glucose:
– insulin signals cells to use and store glucose, and
– glucagon causes cells to release stored glucose into the
blood.
© 2012 Pearson Education, Inc.
Figure 26.7
Insulin
Body
cells
take up more
glucose
3
2
Beta cells
of pancreas stimulated
to release insulin into
the blood
1
4
Liver takes
up glucose
and stores it as
glycogen
High blood
glucose level
Stimulus:
Rising blood glucose
level (e.g., after eating
a carbohydrate-rich
meal)
Blood glucose level
declines to a set point;
stimulus for insulin
release diminishes
Glucose
level
Homeostasis: Normal blood glucose level
(about 90 mg/100 mL)
Glucose
level
Stimulus:
Declining blood
glucose level
(e.g., after
skipping a meal)
5
Blood glucose level
rises to set point;
stimulus for glucagon
release diminishes
8
6
Liver
breaks down
glycogen and
releases glucose
to the blood
7
Glucagon
Alpha
cells of
pancreas stimulated
to release glucagon
into the blood
Low blood
glucose level
Figure 26.7_1
Body
cells take up
glucose
Insulin
3
2
Beta cells
of pancreas
stimulated
4
Liver takes
up glucose;
stores as
glycogen
1
Stimulus:
Rising blood
glucose level
Glucose
level
Homeostasis
Glucose
level
Blood
glucose
declines;
insulin
release
stimulus
diminishes
Figure 26.7_2
Glucose
level
Homeostasis
Stimulus:
Declining
blood
glucose
level
Glucose
level
8
Blood glucose
rises; glucagon
release stimulus
decreases
5
6
Liver
breaks down
glycogen;
glucose is
released
Alpha cells of
pancreas stimulated
7
Glucagon
CONNECTION: Diabetes is a common endocrine
disorder
 Diabetes mellitus
– affects about 8% of the U.S. population and
– results from a
– lack of insulin or
– failure of cells to respond to insulin.
© 2012 Pearson Education, Inc.
CONNECTION: Diabetes is a common endocrine
disorder
 There are three types of diabetes mellitus.
1. Type 1 (insulin-dependent) is
– an autoimmune disease
– caused by the destruction of insulin-producing cells.
2. Type 2 (non-insulin-dependent) is
–
caused by a reduced response to insulin,
–
associated with being overweight and underactive, and
–
the cause of more than 90% of diabetes
3. Gestational diabetes
– can affect any pregnant woman and
– lead to dangerously large babies, which can complicate delivery
© 2012 Pearson Education, Inc.
Blood glucose (mg/100 mL)
Figure 26.8B
400
350
300
Diabetic
250
200
150
Healthy
100
50
0
0
1
2
1
2
3
Hours after glucose ingestion
4
5
Nervous systems receive sensory input, interpret it,
and send out appropriate commands
 The central nervous system (CNS) consists of the
– brain and
– spinal cord (vertebrates).
 The peripheral nervous system (PNS)
– is located outside the CNS and
– consists of
– nerves (bundles of neurons wrapped in connective tissue) and
– ganglia (clusters of neuron cell bodies).
© 2012 Pearson Education, Inc.
Nervous systems receive sensory input, interpret it,
and send out appropriate commands
 Sensory neurons
– convey signals from sensory receptors
– to the CNS.
 Interneurons
– are located entirely in the CNS,
– integrate information, and
– send it to motor neurons.
 Motor neurons convey signals to effector cells.
© 2012 Pearson Education, Inc.
Figure 28.1B
1
Sensory
receptor
2
Sensory
neuron
Brain
Ganglion
Motor
neuron
Spinal
cord
3
Quadriceps
muscles
4
Interneuron
Nerve
Flexor
muscles
PNS
CNS
Figure 28.2_1
Signal direction
Nucleus
Nodes of
Ranvier
Myelin
sheath
Dendrites
Cell
body
Schwann
cell
Axon
Signal
pathway
Synaptic
terminals
Nerve function depends on charge differences
across neuron membranes
 The resting potential exists because of differences in
ion concentration of the fluids inside and outside the
neuron.
– Inside the neuron
– K+ is high and
– Na+ is low.
– Outside the neuron
– K+ is low and
– Na+ is high.
© 2012 Pearson Education, Inc.
Figure 28.3
Neuron
Axon
Plasma
membrane
Outside of neuron
Na
Na
Na
Na
K
K
Na
channel
Na
Plasma
membrane
Na
Na
Na
K
Na
Na
Na
Na
Na-K
pump
K
K
Na
Na
Na
Na
ATP
K channel
K
Na
K
K
Na
Na
K
K
Inside of neuron
K
K
K
K
K
K
K
Figure 28.3_1
Neuron
Plasma
membrane
Axon
Figure 28.3_2
Outside of neuron
Na
Na
Na
Na
K
K
Na
Na
Na
Na
K
Na
Na
Na
Na
Na
Na
Na
Na
channel
Plasma
membrane
K
Na-K
pump
K
Na
ATP
K channel
K
Na
K
K
Na
Na
K
K
Inside of neuron
K
K
K
K
K
K
K
Figure 28.4_s1
Membrane potential
(mV)
50
Action
potential
0
50 Threshold
1
100
Resting potential
Time (msec)
1
Resting state: Voltagegated Na and K
channels are closed;
resting potential is
maintained by ungated
channels (not shown).
Na
Na
Sodium Potassium
channel channel
Outside
of neuron
Plasma membrane
K
Inside of neuron
Figure 28.4_s2
Membrane potential
(mV)
50
Action
potential
0
2
50 Threshold
1
100
Resting potential
Time (msec)
2 A stimulus opens some Na
channels; if threshold is reached,
an action potential is triggered.
Na
Na
K
Figure 28.4_s3
Membrane potential
(mV)
50
Action
potential
3
0
2
50 Threshold
1
100
Resting potential
Time (msec)
3
Additional Na channels
open, K channels are
closed; interior of cell
becomes more positive.
Na
Na
K
Figure 28.4_s4
Membrane potential
(mV)
50
Action
potential
3
0
4
2
50 Threshold
1
100
Resting potential
Time (msec)
4
Na channels close
and inactivate; K
channels open, and
K rushes out;
interior of cell is more
negative than outside.
Na
Na
K
Figure 28.4_s5
Membrane potential
(mV)
50
Action
potential
3
0
2
50 Threshold
1
100
Resting potential
Time (msec)
5
The K channels
close relatively
slowly, causing a
brief undershoot.
4
5
Figure 28.4_s6
Membrane potential
(mV)
50
Action
potential
3
0
2
50 Threshold
1
1
100
5
Resting potential
Time (msec)
1 Return to resting
Na
4
Na
state.
K
Figure 28.5_s1
Action
potential
Na
Plasma
membrane
Axon
segment
1
Na
Figure 28.5_s2
Action
potential
Na
Plasma
membrane
Axon
segment
1
Na
Action potential
Na
K
2
K
Na
Figure 28.5_s3
Action
potential
Na
Plasma
membrane
Axon
segment
1
Na
Action potential
Na
K
2
K
Na
Action potential
Na
K
3
K
Na
Figure 28.5
Axon
Plasma
membrane
Action

Na potential
Axon
segment
1
Na
Action potential
Na
K
2
K
Na
Action potential
Na
K
3
K
Na
Figure 24.1A
Immune System
Innate immunity (24.1–3)
The response is the same whether
or not the pathogen has been
previously encountered
External
barriers (24.1)
Internal
defenses (24.1–2)
• Skin/
exoskeleton
• Acidic
environment
• Secretions
• Mucous
membranes
• Hairs
• Cilia
• Phagocytic cells
• NK cells
• Defensive
proteins
• Inflammatory
response (24.2)
Adaptive immunity
(24.4–15)
Found only in
vertebrates; previous
exposure to the
pathogen enhances the
immune response
• Antibodies (24.8–10)
• Lymphocytes
(24.11–13)
The lymphatic system (24.3)
Figure 24.2
Pin
Skin surface
Swelling
Bacteria
Blood clot
Phagocytes and
fluid move
into the area
Signaling
molecules
Phagocytes
White
blood cell
Blood vessel
1
Tissue injury; signaling
molecules, such as histamine,
are released.
2
Dilation and increased leakiness of
local blood vessels; phagocytes
migrate to the area.
3
Phagocytes (macrophages and
neutrophils) consume bacteria and
cellular debris; the tissue heals.
The adaptive immune response counters specific
invaders
 Our immune system responds to foreign molecules
called antigens, which elicit the adaptive immune
response.
 The adaptive immune system
– is found only in the vertebrates,
– reacts to specific pathogens, and
– “remembers” an invader.
© 2012 Pearson Education, Inc.
The adaptive immune response counters specific
invaders
 Infection or vaccination triggers active immunity.
 Vaccination, or immunization, exposes the
immune system to a vaccine,
– a harmless variant or
– part of a disease-causing microbe.
 We can temporarily acquire passive immunity by
receiving premade antibodies.
© 2012 Pearson Education, Inc.
Lymphocytes mount a dual defense
 Lymphocytes
– are white blood cells that spend most of their time in the
tissues and organs of the lymphatic system,
– are responsible for adaptive immunity, and
– originate from stem cells in the bone marrow.
– B lymphocytes or B cells continue developing in bone marrow.
– T lymphocytes or T cells develop further in the thymus.
© 2012 Pearson Education, Inc.
Lymphocytes mount a dual defense
 B cells
– participate in the humoral immune response and
– secrete antibodies into the blood and lymph.
 T cells
– participate in the cell-mediated immune response,
– attack cells infected with bacteria or viruses, and
– promote phagocytosis by other white blood cells and by
stimulating B cells to produce antibodies.
© 2012 Pearson Education, Inc.
Figure 24.5A
Stem cell
Bone
marrow
Via
blood
Immature lymphocytes
Thymus
Antigen
receptors
B cell
Via
blood
T cell
Final maturation
of B and T cells in a
lymphatic organ
Lymph
nodes,
spleen, and
other
lymphatic
organs
Humoral
immune response
Cell-mediated
immune response
Figure 24.5A_1
Stem cell
Bone
marrow
Immature lymphocytes
Via
blood
Thymus
Antigen
receptors
B cell
T cell
Figure 24.5A_2
Antigen
receptors
B cell
Via
blood
T cell
Final maturation
of B and T cells in a
lymphatic organ
Lymph
nodes,
spleen, and
other
lymphatic
organs
Humoral
immune response
Cell-mediated
immune response
Lymphocytes mount a dual defense
 Millions of kinds of B cells and T cells
– each with different antigen receptors, capable of binding
one specific type of antigen,
– wait in the lymphatic system,
– where they may respond to invaders.
© 2012 Pearson Education, Inc.
Antigens have specific regions where antibodies
bind to them
 Antigenic determinants
are specific regions on
an antigen where
antibodies bind.
– An antigen usually has
several different
determinants.
– The antigen-binding site
of an antibody and an
antigenic determinant
have complementary
shapes.
© 2012 Pearson Education, Inc.
Clonal selection musters defensive forces against
specific antigens
 The clonal selection of B cells occurs in two
responses.
– In the primary immune response, clonal selection
produces
– effector cells and
– memory cells that may confer lifelong immunity.
– In the secondary immune response, memory cells are
activated by a second exposure to the same antigen.
© 2012 Pearson Education, Inc.
Figure 24.7A
Primary immune response
Secondary immune response
2
1 B cells with
different
antigen
receptors
Antigen
molecules
Antigen
receptor
on the cell
surface
Antibody
molecules
3 First exposure
to the antigen
Cell activation:
growth, division,
and differentiation
Antigen
molecules
Antibody
molecules
4
6 Second exposure
5
to the same antigen
First clone
Endoplasmic
reticulum
Plasma (effector) cells secreting antibodies
Second clone
Clone of plasma (effector) cells
secreting antibodies
Memory cells
Clone of memory cells
Figure 24.7A_s1
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
Figure 24.7A_s2
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
2
Antigen
molecules
Figure 24.7A_s3
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
2
Antigen
molecules
3
Cell activation:
growth, division,
and differentiation
First exposure
to the antigen
Figure 24.7A_s4
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
2
Antigen
molecules
3
First exposure
to the antigen
Cell activation:
growth, division,
and differentiation
Antibody
molecules
4
5
First clone
Endoplasmic
reticulum
Plasma (effector) cells secreting antibodies
Memory cells
Figure 24.7A_s5
Antigen
molecules
6
Memory cells
Second
exposure
to the same
antigen
Figure 24.7A_s6
Secondary immune response
Antibody
molecules
Antigen
molecules
6
Memory cells
Second
exposure
to the same
antigen
Clone of plasma (effector) cells
secreting antibodies
Second clone
Clone of memory cells
Clonal selection musters defensive forces against
specific antigens
 Primary vs. secondary immune responses
– The primary immune response
– occurs upon first exposure to an antigen and
– is slower than the secondary immune response.
– The secondary immune response
– occurs upon second exposure to an antigen and
– is faster and stronger than the primary immune response.
© 2012 Pearson Education, Inc.
Figure 24.7B
Antibody concentration
Second exposure
to antigen X,
first exposure
to antigen Y
Secondary immune
response to
antigen X
First exposure
to antigen X
Primary immune
response to
antigen X
Antibodies
to Y
Antibodies
to X
0
7
14
21
Primary immune
response to
antigen Y
35
28
Time (days)
42
49
56
Antibodies are the weapons of the humoral
immune response
 Antibodies are secreted
– by plasma (effector) B cells,
– into the blood and lymph.
© 2012 Pearson Education, Inc.
Figure 24.8A
Light chain
Heavy chain
Antibodies are the weapons of the humoral
immune response
 An antibody molecule
– is Y-shaped and
– has two antigen-binding sites specific to the antigenic
determinants that elicited its secretion.
© 2012 Pearson Education, Inc.
Figure 24.8B
Antigen
Antigen-binding
sites
Light
chain
C
C
Heavy
chain
Antibodies mark antigens for elimination
 Antibodies promote antigen elimination through
several mechanisms:
1. neutralization, binding to surface proteins on a virus or
bacterium and blocking its ability to infect a host,
2. agglutination, using both binding sites of an antibody to
join invading cells together into a clump,
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Antibodies mark antigens for elimination
3. precipitation, similar to agglutination, except that the
antibody molecules link dissolved antigen molecules
together, and
4. activation of the complement system by antigen-antibody
complexes.
© 2012 Pearson Education, Inc.
Figure 24.9
Binding of antibodies to antigens
inactivates antigens by
Neutralization
(blocks viral binding sites;
coats bacteria)
Virus
Agglutination
of microbes
Precipitation of
dissolved antigens
Activation of the
complement system
Complement
molecule
Bacteria
Antigen
molecules
Bacterium
Foreign cell
Enhances
Leads to
Phagocytosis
Cell lysis
Macrophage
Hole
Figure 24.9_1
Neutralization
(blocks viral binding
sites; coats bacteria)
Agglutination
of microbes
Precipitation of
dissolved antigens
Bacteria
Virus
Antigen
molecules
Bacterium
Enhances
Phagocytosis
Macrophage
Figure 24.9_2
Activation of the
complement system
Complement
molecule
Foreign cell
Leads to
Cell lysis
Hole