Download APDC Unit VII- Nerv Imm

UNIT VII- NERVOUS &
IMMUNE
CHAPTERS 35, 37, 38*
REVIEW WARM-UP
1.
Contrast the functions of B cells and T cells.
2.
What are memory cells?
3.
How do vaccines work?
4.
How does HIV affect the immune system?
WARM-UP
1.
Draw and label the parts of a neuron.
2.
Describe saltatory conduction.
3.
Explain how a nerve impulse is transmitted across a neuron.
WARM-UP
1.
What happens at the synapse?
2.
Choose 1 neurotransmitter. Describe its action.
3.
What is the role of the following structures in the human brain?
a)
Brainstem
b)
Cerebellum
c)
Cerebrum
d)
Corpus callosum
NERVOUS SYSTEMS
CHAPTERS 37, 38*
YOU MUST KNOW
 The anatomy of a neuron.
 The mechanisms of impulse transmission in a neuron.
 The process that leads to release of neurotransmitters, and what happens at the
synapse.
 How the vertebrate brain integrates information, which leads to an appropriate
response.
 Different regions of the brain have different functions.
TWO REGULATORY SYSTEMS
• Nervous System
• Endocrine System
• Fast!
• Slower to start
• Short duration effect
• Longer duration effect
• Electric (ionic) signals
…but also chemicals
(neurotransmitters)
• Chemical signals
(hormones)
• Affects nearby cells
(local)
• Affects any cell (long
distance)
NS & ES ARE RELATED
1. Neurosecretory Cells
• In brain, but secrete hormones
• Ex: epinephrine as hormone & neurotransmitter
2. Each system affects outcome of other
• Ex: suckling…neurons…oxytocin…more milk
• Ex: chemoreceptors detect glucose in
blood…pancreas secretes insulin/glucagon
NS & ES ARE RELATED
3. Feedback Mechanisms
• Positive
• Ex: suckling/oxytocin
• Negative
• Ex: calcium levels/
PTH/calcitonin
ORGANIZATION OF THE NERVOUS SYSTEM
 Central nervous system (CNS) = brain + spinal cord
 Peripheral nervous system (PNS) = nerves throughout
body
 Sensory receptors: collect info
 Sensory neurons: body  CNS
 Motor neurons: CNS  body (muscles, glands)
 Interneurons: connect sensory & motor neurons
 Nerves = bundles of neurons
 Contains motor neurons +/or sensory neurons
PERIPHERAL NERVOUS SYSTEM
Peripheral
nervous system
Somatic
nervous
system
Autonomic
nervous
system
Sympathetic
division
Parasympathetic
division
Enteric
division
NEURON = DENDRITE + CELL BODY + AXON
Fig. 48-5
STRUCTURAL DIVERSITY OF NEURONS
Dendrites
Axon
Cell
body
Portion
of axon
Sensory neuron
Interneurons
Cell bodies of
overlapping neurons
80 µm
Motor neuron
NEURON
• cell body: contains nucleus & organelles
• dendrites: receive incoming messages
• axons: transmit messages away to other cells
• myelin sheath: fatty insulation covering axon, speeds up nerve
impulses
• synapse: junction between 2 neurons
• neurotransmitter: chemical messengers sent across synapse
• Glia: cells that support neurons
• Eg. Schwann cells (forms myelin sheath)
SCHWANN CELLS AND THE MYELIN SHEATH
MAKE A MAD MAD, MAD NEURON
• http://learn.genetics.utah.edu/content/neuroscience/madneuron/
BIOFLIX: HOW
NEURONS WORK
HTTP://MEDIA.PEARSONCMG.COM/BC/BC_0MEDIA_BIO/BIOFLIX/BIOFLIX.HT
M?C8ENEURONS
MEMBRANE POTENTIAL: DIFFERENCE IN
ELECTRICAL CHARGE ACROSS CELL MEMBRANE
Microelectrode
–70 mV
Voltage
recorder
Reference
electrode
GATED ION CHANNELS
OPEN OR CLOSE IN RESPONSE TO 3 KINDS OF
STIMULI • Stretch–gated - in cells that sense stretch; open when
membrane mechanically deformed
• Ligand–gated - at synapses; open/close when specific
neurotransmitter binds to channel
• Voltage–gated - in axons; open/close when membrane
potential changes
• Gated ion channels are responsible for generating the signals
of the nervous system
MEMBRANE POTENTIAL
the outside of the cell is
more positive
the difference in charge
while it is not “firing” is
called the “resting
potential”
Action Potential Cartoon –Self-Guided
http://outreach.mcb.harvard.edu/animations/actionpotential_
short.swf
Action Potential Video
https://www.youtube.com/watch?
v=U0NpTdge3aw
VOLTAGE-GATED ION CHANNELS
• Resting state…more (+) outside than inside
VOLTAGE-GATED ION CHANNELS
• Stimulus causes Na channels to open
VOLTAGE-GATED ION CHANNELS
• Once enough Na+ moves in, membrane is
“depolarized”
VOLTAGE-GATED ION CHANNELS
• Next, K+ gates open to allow them to move out…just
as Na+ gates close… ”repolarization”
VOLTAGE-GATED ION CHANNELS
The Na+/K+ pump (using ATP) maintains a
negative potential inside the neuron.
ACTION POTENTIALS (NERVE IMPULSES) ARE
THE SIGNALS CONDUCTED BY AXONS
Resting potential: membrane potential at rest; polarized
 Na+ outside, K+ inside cell
 Voltage-gated Na+ channel = CLOSED
Nerve impulse: stimulus causes a change in membrane potential
 Action potential: neuron membrane depolarizes
 All-or-nothing response
Na+ channels
open
Na+ enters cell
K+ channels
open
K+ leaves cell
PROPAGATION OF THE ACTION
POTENTIAL
• How related to neuron?
• As Na+ ions move in, the potential
“flip-flops” triggering K+ gates to
open
• Meanwhile the Na+ ions diffuse
over to next area causing the “flipflop” in charge
• And it goes on and on…
PROPAGATION OF THE ACTION POTENTIAL
CONDUCTION
OF AN ACTION
POTENTIAL
NERVE IMPULSE
ANIMATION
HTTPS://WWW.YOUTUBE.COM/WATCH?V=9EUDB4TN3B0
5:41
SALTATORY CONDUCTION: NERVE IMPULSE JUMPS
BETWEEN NODES OF RANVIER (UNMYELINATED
GAPS)  SPEEDS UP IMPULSE
Saltatory conduction speed: 120 m/sec
BIOFLIX: HOW
SYNAPSES WORK
HTTP://MEDIA.PEARSONCMG.COM/BC/BC_0MEDIA_BIO/BIOFLIX/BIOFLIX.HT
M?8APSYNAPSES
CELL COMMUNICATION: NEUROTRANSMITTER RELEASED
AT SYNAPSES
AXON (PRESYNAPTIC CELL)  DENDRITE (POSTSYNAPTIC
CELL)
NEUROTRANSMITTERS
• Chemicals released from vesicles by exocytosis into synaptic cleft
• Diffuse across synapse
• Bind to receptors on neurons, muscle cells, or gland cells
• Broken down by enzymes or taken back up into surrounding cells
• Types of neurotransmitters:
• Excitatory: speed up impulses by causing depolarization of postsynaptic
membrane
• Inhibitory: slow impulses by causing hyperpolarization of postsynaptic
membrane
EXAMPLES OF NEUROTRANSMITTERS
• Acetylcholine (ACh): stimulates muscles, memory formation, learning
• Epinephrine: (adrenaline) fight-or-flight
• Norepinephrine: fight-or-flight
• Dopamine: reward, pleasure (“high”)
• Loss of dopamine  Parkinson’s Disease
• Serotonin: well-being, happiness
• Low levels  Depression
• GABA: inhibitory NT
• Affected by alcohol
NERVOUS SYSTEM DISORDERS
• LSD/mescaline – bind to serotonin and dopamine receptors 
hallucinations
• Prozac – enhances effect of serotonin by inhibiting uptake after release
• Morphine, heroin – bind to endorphin receptors  decrease pain
perception
• Viagra – increase NO (nitric oxide) effects  maintain erection
• Alzheimer’s Disease (AD) – develop senile plaques, shrinkage of brain
tissue
MOUSE PARTY
HTTP://LEARN.GENETICS.UTAH.EDU/CONTENT/ADDICTION/MOUSE/
MOUSE PARTY
Mini-Poster Presentation:
Drug: which drug and background information
Neurotransmitter(s) Involved
Action of Drug
Summary Illustration: mouse drug affects
REFLEXES
• Simple, automatic response to a stimulus
• Conscious thought not required
• Reflex arc:
1. Stimulus detected by receptor
2. Sensory neuron
3. Interneuron (spinal cord or brain stem)
4. Motor neuron
5. Response by effector organ (muscles, glands)
KNEE-JERK REFLEX
EVOLUTION OF NERVOUS SYSTEMS
VERTEBRATE BRAIN IS REGIONALLY
SPECIALIZED
Major Regions: forebrain, midbrain, hindbrain
•
•
•
Forebrain  cerebrum
Midbrain  brainstem
Hindbrain  cerebellum
HUMAN BRAIN
Structure
Function
Cerebrum
• Information processing (learning, emotion,
memory, perception, voluntary movement)
• Right & Left cerebral hemispheres
• Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
•Basic, autonomic survival behaviors
•Medulla oblongata –breathing, heart & blood
vessel activity, digestion, swallowing, vomiting
•Transfer info between PNS & CNS
Cerebellum
• Coordinate movement & balance
• Motor skill learning
Human Brain
Structure
Function
Cerebrum
• Information processing (learning, emotion,
memory, perception, voluntary movement)
• Right & Left cerebral hemispheres
• Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
•Basic, autonomic survival behaviors
•Medulla oblongata –breathing, heart & blood
vessel activity, digestion, swallowing, vomiting
•Transfer info between PNS & CNS
Cerebellum
• Coordinate movement & balance
• Motor skill learning
Human Brain
Structure
Function
Cerebrum
• Information processing (learning, emotion,
memory, perception, voluntary movement)
• Right & Left cerebral hemispheres
• Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
•Basic, autonomic survival behaviors
•Medulla oblongata –breathing, heart & blood
vessel activity, digestion, swallowing, vomiting
•Transfer info between PNS & CNS
Cerebellum
• Coordinate movement & balance
• Motor skill learning
Human Brain
Structure
Function
Cerebrum
• Information processing (learning, emotion,
memory, perception, voluntary movement)
• Right & Left cerebral hemispheres
• Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
•Basic, autonomic survival behaviors
•Medulla oblongata –breathing, heart & blood
vessel activity, digestion, swallowing, vomiting
•Transfer info between PNS & CNS
Cerebellum
• Coordinate movement & balance
• Motor skill learning
GREY MATTER: NEURON CELL BODIES,
UNMYELINATED AXONS
WHITE MATTER: FATTY, MYELINATED AXONS
CHAPTER 35 WARM-UP
1. Define the following terms:
• Pathogen
• Antigen
• Antibody
• Allergen
• Vaccine
2. What are lymphocytes? Where do B cells and T
cells mature?
CH. 35 REVIEW WARM-UP
1. What is the difference between innate vs.
adaptive immunity?
2. Contrast the functions of B cells and T cells.
3. How are antigens recognized by immune
system cells?
4. What are memory cells?
5. How does HIV affect the immune system?
Chapter 35
THE IMMUNE SYSTEM
WHAT YOU MUST KNOW:
• Several elements of an innate immune response
• The differences between B and T cells relative to their
activation and actions.
• How antigens are recognized by immune system cells
• The differences in humoral and cell-mediated
immunity
• Why Helper T cells are central to immune responses
TYPES OF IMMUNITY
Innate Immunity
• Non-specific
• All plants & animals
Adaptive Immunity
• Pathogen-specific
• Only in vertebrates
• Involves B and T cells
PLANT DEFENSES
• Nonspecific responses
• Receptors recognize pathogen molecules and
trigger defense responses
• Thicken cell wall, produce antimicrobial compounds, cell death
• Localize effects
FIGURE 43.2
Pathogens
(such as bacteria,
fungi, and viruses)
INNATE IMMUNITY
(all animals)
• Recognition of traits shared
by broad ranges of
pathogens, using a small
set of receptors
• Rapid response
ADAPTIVE IMMUNITY
(vertebrates only)
• Recognition of traits
specific to particular
pathogens, using a vast
array of receptors
• Slower response
Barrier defenses:
Skin
Mucous membranes
Secretions
Internal defenses:
Phagocytic cells
Natural killer cells
Antimicrobial proteins
Inflammatory response
Humoral response:
Antibodies defend against
infection in body fluids.
Cell-mediated response:
Cytotoxic cells defend
against infection in body cells.
Barrier Defenses:
•Skin
•Mucous membranes
•Lysozyme (tears, saliva,
mucus)
Antimicrobial Proteins:
• Interferons (inhibit viral reproduction)
• Complement system (~30 proteins,
membrane attack complex)
Innate
Immunity
(non-specific)
Natural Killer Cells:
•Virus-infected and
cancer cells
Inflammatory Response:
• Mast cells release histamine
• Blood vessels dilate, increase
permeability (redness, swelling)
• Deliver clotting agents,
phagocytic cells
• Fever
Phagocytic WBCs:
•Neutrophils (engulf)
•Macrophage (“big eaters”)
•Eosinophils (parasites)
•Dendritic cells (adaptive
response)
NONSPECIFIC DEFENSES
FIRST LINE OF DEFENSE
• Skin
• Antimicrobial proteins
• Mucous membranes
• Cilia
• Gastric juice
• Symbiotic Bacteria
• Temperature
NONSPECIFIC DEFENSES
SECOND LINE OF DEFENSE
• Inflammatory Response
• Injury breaking the skin introducing pathogens
• Histamine is released causing increase blood flow to area
• Causes redness, swelling, warmth, and pain
• Vasodilation (dilation of the blood vessels)
• Caused by histamine
• Phagocytes pass through capillary walls into tissues to ingest and destroy
pathogens
NONSPECIFIC DEFENSES
SECOND LINE OF DEFENSE
• Phagocytes destroy the pathogens and the injury begins to
heal.
• Neutrophil; Macrophage
• Natural killer cells
• Attack pathogen-infected cells
• Effective at killing cancer cells and virus-infected
cells
NONSPECIFIC DEFENSES
SECOND LINE OF DEFENSE
• Complement
• A group of about twenty proteins that “complement” defense
reactions.
• Help to destroy foreign or infected cell by promoting cell lysis
• Interferon
• Molecules secreted by viral infected cells that stimulate
neighboring cells to produce proteins that help them defend
against viruses
SPECIFIC DEFENSES
THIRD LINE OF DEFENSE
A RESPONSE AIMED SPECIFICALLY AT THE PATHOGEN
• Lymphocyte = white blood cell of the immune system
• React to antigens
• Two types
– B cells
• Made in the bone marrow
• A part of the humoral immune response
• Produce antibodies
• Plasma cell- B cells that release specific antibodies
• Memory cell- long-lived B cells that do not release their antibodies, they circulate in the body
and respond quickly to eliminate any subsequent invasion by the same antigen.
SPECIFIC DEFENSES
THIRD LINE OF DEFENSE
A RESPONSE AIMED SPECIFICALLY AT THE PATHOGEN
• T cells
• Made in the bone marrow, mature in the Thymus (T
for thymus)
• A part of the cell-mediated response
• Destroy infected cells
• Cytotoxic T cells (killer T cells); Helper T cells;
Suppressor T cells
COMPARING IMMUNE RESPONSES-PG 20
Type of cell
Function
Macrophage
Engulfs and kills pathogens
Neutrophil
Engulfs and destroys pathogens
Natural killer cell
Punctures infected cells
Helper T cell
Activates cytotoxic T cells
Cytotoxic T cell
Punctures labeled infected cells
B cell
Labels invaders for destruction by
macrophages
Plasma cell
Releases antibodies
Memory cell
Stores information about a pathogen
PHAGOCYTOSIS
INFLAMMATORY RESPONSE
LYMPHATIC SYSTEM: INVOLVED IN ADAPTIVE
IMMUNITY
ADAPTIVE RESPONSE
Lymphocytes (WBCs): produced
by stem cells in bone marrow
• T cells: mature in thymus
• helper T, cytotoxic T
• B cells: stay and mature in bone
marrow
• plasma cells  antibodies
• Antigen: substance that elicits lymphocyte response
• Antibody (immunoglobulin – Ig): protein made by B
cell that binds to antigens
Fig. 43-9
Antigenbinding
site
Antigenbinding site
Antigenbinding
site
Disulfide
bridge
C
C
Light
chain
Heavy chains
Variable
regions
V
V
Constant
regions
C
C
Transmembrane
region
Plasma
membrane
chain
chain
Disulfide bridge
B cell
(a) B cell receptor
Cytoplasm of B cell
Cytoplasm of T cell
(b) T cell receptor
T cell
Fig. 43-9a
Antigenbinding site
Antigenbinding
site
Disulfide
bridge
Variable
regions
C
C
Light
chain
Constant
regions
Transmembrane
region
Plasma
membrane
Heavy chains
B cell
(a) B cell receptor
Cytoplasm of B cell
Fig. 43-9b
Antigenbinding
site
Variable
regions
V
V
Constant
regions
C
C
Transmembrane
region
Plasma
membrane
chain
chain
Disulfide bridge
Cytoplasm of T cell
(b) T cell receptor
T cell
THE ANTIGEN RECEPTORS OF B CELLS AND T CELLS
• B cell receptors bind to specific, intact antigens
• The B cell receptor consists of two identical heavy
chains and two identical light chains
• The tips of the chains form a constant (C) region, and
each chain contains a variable (V) region, so named
because its amino acid sequence varies extensively
from one B cell to another
• Secreted antibodies, or immunoglobulins, are
structurally similar to B cell receptors but lack
transmembrane regions that anchor receptors in
the plasma membrane
• Each T cell receptor consists of two different
polypeptide chains
• The tips of the chain form a variable (V) region; the
rest is a constant (C) region
• T cells can bind to an antigen that is free or on the
surface of a pathogen
MAJOR HISTOCOMPATIBILITY COMPLEX
(MHC)
• Proteins displayed on cell surface
• Responsible for tissue/organ rejection (“self” vs. “nonself”)
• B and T cells bind to MHC molecule in adaptive response
• Class I: all body cells (except RBCs)
• Class II: displayed by immune cells; “non-self”
Fig. 43-11
Top view: binding surface
exposed to antigen receptors
Antigen
Class I MHC
molecule
Antigen
Plasma
membrane of
infected cell
• Class I MHC molecules are found on almost all
nucleated cells of the body
• They display peptide antigens to cytotoxic T cells
Fig. 43-12
Infected cell
Microbe
Antigenpresenting
cell
1 Antigen
associates
with MHC
molecule
Antigen
fragment
Antigen
fragment
1
Class I MHC
molecule
1
T cell
receptor
(a)
2
2
Cytotoxic T cell
Class II MHC
molecule
T cell
receptor
2 T cell
recognizes
combination
(b)
Helper T cell
• Class II MHC molecules are located mainly on
dendritic cells, macrophages, and B cells
• Dendritic cells, macrophages, and B cells are
antigen-presenting cells that display antigens to
cytotoxic T cells and helper T cells
LYMPHOCYTE DEVELOPMENT
• The acquired immune system has three important
properties:
• Receptor diversity
• A lack of reactivity against host cells
• Immunological memory
GENERATION OF LYMPHOCYTE DIVERSITY BY GENE
REARRANGEMENT
• Differences in the variable region account for
specificity of antigen receptors
• The immunoglobulin (Ig) gene encodes one chain of
the B cell receptor
• Many different chains can be produced from the
same Ig chain gene by rearrangement of the DNA
• Rearranged DNA is transcribed and translated and
the antigen receptor formed
Fig. 43-13
DNA of undifferentiated B cell
V37
V38
V39
V40
J1
J2
J3
J4
J5
C
Intron
1 DNA deleted between randomly selected V and J
segments
DNA of differentiated B cell
V37
V38
V39 J5
Intron
C
Functional gene
2 Transcription
pre-mRNA
V39 J5
Intron
C
3 RNA processing
V39 J5
mRNA Cap
C
B cell receptor
Poly-A tail
V
V
V
4 Translation
V
C
C
Light-chain polypeptide
V
Variable
region
C
C
Constant
region
B cell
C
ORIGIN OF SELF-TOLERANCE
• Antigen receptors are generated by random
rearrangement of DNA
• As lymphocytes mature in bone marrow or the
thymus, they are tested for self-reactivity
• Lymphocytes with receptors specific for the body’s
own molecules are destroyed by apoptosis, or
rendered nonfunctional
AMPLIFYING LYMPHOCYTES BY CLONAL SELECTION
• In the body there are few lymphocytes with antigen
receptors for any particular epitope
• The binding of a mature lymphocyte to an antigen
induces the lymphocyte to divide rapidly
• This proliferation of lymphocytes is called clonal
selection
• Two types of clones are produced: short-lived
activated effector cells and long-lived memory
cells
Fig. 43-14
Antigen molecules
B cells that
differ in
antigen
specificity
Antigen
receptor
Antibody
molecules
Clone of memory cells
Clone of plasma cells
• The first exposure to a specific antigen represents
the primary immune response
• During this time, effector B cells called plasma
cells are generated, and T cells are activated to their
effector forms
• In the secondary immune response, memory
cells facilitate a faster, more efficient response
Primary immune response
to antigen A produces
antibodies to A.
Antibody concentration
(arbitrary units)
Fig. 43-15
Secondary immune response to
antigen A produces antibodies to A;
primary immune response to antigen
B produces antibodies to B.
104
103
Antibodies
to A
102
Antibodies
to B
101
100
0
7
Exposure
to antigen A
14
21
28
35
42
Exposure to
antigens A and B
Time (days)
49
56
ACQUIRED IMMUNITY DEFENDS AGAINST
INFECTION OF BODY CELLS AND FLUIDS
• Acquired immunity has two branches: the humoral
immune response and the cell-mediated immune
response
• Humoral immune response involves activation
and clonal selection of B cells, resulting in
production of secreted antibodies
• Cell-mediated immune response involves
activation and clonal selection of cytotoxic T cells
• Helper T cells aid both responses
Fig. 43-16
Humoral (antibody-mediated) immune response
Cell-mediated immune response
Key
Antigen (1st exposure)
+
Engulfed by
Gives rise to
Antigenpresenting cell
+
Stimulates
+
+
B cell
Helper T cell
+
Cytotoxic T cell
+
Memory
Helper T cells
+
+
+
Antigen (2nd exposure)
Plasma cells
Memory B cells
+
Memory
Cytotoxic T cells
Active
Cytotoxic T cells
Secreted
antibodies
Defend against extracellular pathogens by binding to antigens,
thereby neutralizing pathogens or making them better targets
for phagocytes and complement proteins.
Defend against intracellular pathogens
and cancer by binding to and lysing the
infected cells or cancer cells.
Fig. 43-16a
Humoral (antibody-mediated) immune response
Key
+
Antigen (1st exposure)
Stimulates
Gives rise to
Engulfed by
Antigenpresenting cell
+
+
B cell
Helper T cell
+
Memory
Helper T cells
+
Plasma cells
+
Antigen (2nd exposure)
Memory
B cells
Secreted
antibodies
Defend against extracellular pathogens
+
Fig. 43-16b
Cell-mediated immune response
Key
+
Antigen (1st exposure)
Engulfed by
Antigenpresenting cell
Stimulates
Gives rise to
+
+
Helper T cell
Cytotoxic T cell
+
Memory
Helper T cells
+
+
Antigen (2nd exposure)
+
Active
Cytotoxic T cells
Memory
Cytotoxic T cells
Defend against intracellular pathogens
MC EXAMPLES
• 26. The brain coordinates the circulatory and respiratory systems of the human body. The
control of breathing, for example, involves neural pathways among the structures represented
in the figure above. One important stimulus in the control of breathing is an increase in blood
CO2 concentration, which is detected as a decrease in blood
• pH.Which of the following best describes the physiological response to an overall increase in
cellular respiration in the body?
• (A) In response to depleted blood CO2 levels, the pH sensors send signals directly to the rib
muscles, resulting in an increase in the rate of CO2 uptake by the lungs and a decrease in CO2
utilization by the brain.
• (B) In response to low blood pH, the pH sensors send a signal to the brain, which then sends a
signal to the diaphragm, resulting in an increased rate of breathing to help eliminate excess
blood CO2 .
• (C) In response to high blood pH, the pH sensors send a signal directly to the lungs, resulting
in a slower rate of breathing, and the lungs send a signal back to the heart once CO2
availability has been restored.
• (D) In response to an increased rate of breathing, the rib muscles send a signal to the brain,
which then sends a signal to the heart, resulting in a decrease in heart activity and slower flow
of blood through the body.
MC EXAMPLE
• 27. Thyroxin is a hormone that increases metabolic activities within various tissue targets. Low levels of circulating
thyroxin trigger the secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH secretion
then stimulates thyroxin production and release by the thyroid gland. The increased level of circulating thyroxin
inhibits further secretion of TSH from the anterior pituitary.
• Based on the information provided, which of the following can most likely be concluded about the TSH-thyroxin
loop?
• (A) A person taking thyroxin to supplement low thyroxin secretion will produce more TSH.
• (B) Increased thyroxin production would cause elevated ribosomal activity in the anterior pituitary.
• (C) The structure of the loop would lead to elevated thyroid and tissue activity due to positive feedback.
• (D) The feedback mechanism would maintain relatively constant levels of thyroxin throughout tissue targets.
MC EXAMPLE
• Antigen invader  B-cell meets antigen  B-cell differentiates into plasma cells and memory cells  plasma cells
produce antibodies  antibodies eliminate antigen. The preceding sequence of events is a description of
A. Cell mediated immunity
B. Humoral immunity
C. Nonspecific immunity
D. Phagocytosis
E. Cytotoxic T-cell maturation
• A man contracts the same flu strain for the second time in a single winter season. The second time he experiences
fewer symptoms and recovers more quickly. Which cells are responsible for this rapid recovery?
A. Helper T-cells
B. Cytotoxic T-cells
C. Memory cells
D. Plasma cells
MC EXAMPLE
• Which of the following cells is most closely associated with phagocytosis?
• Neutrophils
• Plasma cells
• B cells
• Memory cells
• LFRQ
• The immune system is the body's defense against foreign invaders and is divided into specific and nonspecific immunity,
and humoral and cell mediated immunity. Answer 3 of the 4 following questions:
• Describe the primary immune response and how an invading antigen is met, dealt with, and eliminated. Describe the cells involved
and how they are created.
• Describe the mechanism by which the immune system deals with viruses, invaders that make it inside our cells
• Define nonspecific immunity, and list 3 examples of nonspecific defense mechanisms in humans
• Define the term vaccination, and describe how a vaccination works.