Download Chapter 24: The Immune System 24.1 Innate defenses against

Chapter 24: The Immune System
24.1 Innate defenses against infection include the skin and mucous membranes,
phagocytic cells, and antimicrobial proteins
• Innate immunity
– Is present and effective long before exposure to pathogens
• Microbes that breach the body’s external defenses
– Are engulfed and destroyed by macrophages
• Interferons are proteins produced by virus-infected cells
– That help other cells resist viruses
24.2 The inflammatory response mobilizes nonspecific defense forces
• Tissue damage triggers the inflammatory response
• The inflammatory response
• Can disinfect tissues and limit further infection
24.3 The lymphatic system becomes a crucial battleground during infection
• The lymphatic system
– Is a network of lymphatic vessels and organs
• The vessels collect fluid from body tissues
– And return it as lymph to the blood
• Lymph organs such as the spleen and lymph nodes
– Are packed with white blood cells that fight infections
24.4 The immune response counters specific invaders
• Our immune system
– Responds to foreign molecules called antigens
• The immune system reacts to antigens
– And “remembers” an invader
• We can temporarily acquire passive immunity
– By receiving “premade” antibodies
• Infection or vaccination
– Triggers active immunity
24.5 Lymphocytes mount a dual defense
• Two kinds of lymphocytes carry out the immune response
– B cells secrete antibodies that attack antigens
– T cells attack cells infected with pathogens
• Millions of kinds of B cells and T cells, each with different membrane
receptors
– Wait in the lymphatic system, where they may respond to invaders
24.6 Antigens have specific regions where antibodies bind to them
• Antigenic determinants
– Are the specific regions on an antigen to which antibodies bind
24.7 Clonal selection musters defensive forces against specific antigens
• When an antigen enters the body
– It activates only a small subset of lymphocytes with
complementary receptors
• The selected lymphocyte cells multiply into clones of short-lived effector
cells
–
Specialized for defending against the antigen that triggered the
response
The Steps of Clonal Selection
• 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, which initiates a faster and more massive response
Primary vs. Secondary Immune Response
• The primary immune response
– Is slower than the secondary immune response
24.8 Antibodies are the weapons of humoral immunity
• Antibody molecules
– Are secreted by plasma (effector) B cells
• An antibody molecule
– Has antigen-binding sites specific to the antigenic determinants
that elicited its secretion
24.9 Antibodies mark antigens for elimination
• Antibodies promote antigen elimination
– Through several mechanisms
24.10 Monoclonal antibodies are powerful tools in the lab and clinic
• Monoclonal antibodies
– Are produced by fusing B cells specific for a single antigenic
determinant with easy to grow tumor cells
• These molecules
– Are useful in research, diagnosis, and treatment of certain cancers
24.11 Helper T cells stimulate humoral and cell-mediated immunity
• Helper T cells and cytotoxic T cells
– Are the main effectors of cell-mediated immunity
• Helper T cells
– Also stimulate the humoral responses
• In cell-mediated immunity, an antigen-presenting cell
– Displays a foreign antigen and one of the body’s own self proteins
to a helper T cell
• The helper T cell’s receptors
– Recognize the self-nonself complexes and the interaction activates
the helper T cells
• The helper T cell
– Can then activate cytotoxic T cells and B cells
24.12 HIV destroys helper T cells, compromising the body’s defenses
• The AIDS virus attacks helper T Cells
– Opening the way for opportunistic infection
24.13 Cytotoxic T cells destroy infected body cells
• Cytotoxic T cells
– Bind to infected body cells and destroy them
24.14 Cytotoxic T cells may help prevent cancer
• Cytotoxic T cells may attack cancer cells
– Which have abnormal surface molecules
24.15 The immune system depends on our molecular fingerprints
• The immune system
– Normally reacts only against nonself substances, not against self
– May reject transplanted organs because these cells lack the unique
“fingerprint” of the recipient’s self proteins
24.16 Malfunction or failure of the immune system causes disease
• In autoimmune diseases
– The system turns against the body’s own molecules
• In immunodeficiency diseases
– Immune components are lacking, and frequent infections recur
• Physical and emotional stress
– May weaken the immune system
24.17 Allergies are overreactions to certain environmental antigens
• Allergies
– Are abnormal sensitivities to antigens (allergens) in the
surroundings
NERVOUS SYSTEM STRUCTURE AND FUNCTION
28.1 Nervous systems receive sensory input, interpret it, and send out appropriate
commands
• Nervous systems
– Are the most intricately organized data-processing systems on
Earth
• The nervous system obtains and processes sensory information
– And sends commands to effector cells, such as muscles, that carry
out appropriate responses
• Sensory neurons
– Conduct signals from sensory receptors to the central nervous
system (CNS)
• The CNS
– Consists of the brain and spinal cord
• Interneurons in the CNS
– Integrate information and send it to motor neurons
• Motor neurons
– Convey signals to effector cells
• Automatic responses called reflexes
– Provide an example of nervous system function
• Located outside the CNS, the peripheral nervous system (PNS)
– Consists of nerves (bundles of fibers of sensory and motor
neurons) and ganglia (clusters of cell bodies of the neurons)
28.2 Neurons are the functional units of nervous systems
• Neurons
– Are cells specialized for carrying signals
• A neuron consists of
– A cell body
– Two types of extensions (fibers) that conduct signals, dendrites and
axons
• Many axons are enclosed by cellular insulation called the myelin sheath
– Which speeds up signal transmission
28.3 A neuron maintains a membrane potential across its membrane
• At rest, a neuron’s plasma membrane
– Has an electrical voltage called the resting potential
• The resting potential
– Is caused by the membrane’s ability to maintain a positive charge
on its outer surface opposing a negative charge on its inner surface
28.4 A nerve signal begins as a change in the membrane potential
• A stimulus alters the permeability of a portion of the membrane
– Allowing ions to pass through and changing the membrane’s
voltage
• A nerve signal, called an action potential
– Is a change in the membrane voltage from the resting potential to a
maximum level and back to the resting potential
28.5 The action potential propagates itself along the neuron
•
Action potentials
– Are self-propagated in a one-way chain reaction along a neuron
– Are all-or-none events
• The frequency of action potentials, but not their strength
– Changes with the strength of the stimulus
28.6 Neurons communicate at synapses
• The transmission of signals between neurons
– Or between neurons and effector cells occurs at junctions called
synapses
• Electrical signals
– Pass between cells at electrical synapses
• At chemical synapses
– The sending cell secretes a chemical signal, a neurotransmitter
• The neurotransmitter
– Crosses the synaptic cleft and binds to a receptor on the surface of
the receiving
28.7 Chemical synapses make complex information processing possible
• A neuron may receive information
– From hundreds of other neurons via thousands of synaptic
terminals
• Some neurotransmitters
– Excite the receiving cell
• Other types of neurotransmitters
– Inhibit the receiving cell’s activity by decreasing its ability to
develop action potentials
• The summation of excitation and inhibition
– Determines whether or not a neuron will transmit a nerve signal
28.8 A variety of small molecules function as neurotransmitters
• Many small, nitrogen-containing molecules
– Serve as neurotransmitters
28.9 Many drugs act at chemical synapses
• Many psychoactive drugs
– Act at synapses and affect neurotransmitter action
28.10 Nervous system organization usually correlates with body symmetry
• Radially symmetrical animals
– Have a nervous system arranged in a weblike system of neurons
called a nerve net
• Most bilaterally symmetrical animals exhibit
– Cephalization, the concentration of the nervous system in the head
region
– Centralization, the presence of a central nervous system
28.11 Vertebrate nervous systems are highly centralized and cephalized
• The brain and spinal cord
– Contain fluid-filled spaces
• Cranial and spinal nerves
– Make up the peripheral nervous system
28.12 The peripheral nervous system of vertebrates is a functional hierarchy
• The PNS can be divided into two functional components
– The somatic nervous system and the autonomic nervous system
• The somatic nervous system
– Carries signals to and from skeletal muscles, mainly in response to
external stimuli
• The autonomic nervous system
– Regulates the internal environment by controlling smooth and
cardiac muscles and the organs of various body systems
28.13 Opposing actions of sympathetic and parasympathetic neurons regulate the internal
environment
• The parasympathetic division of the autonomic nervous system
– Primes the body for activities that gain and conserve energy for the
body
• The sympathetic division of the autonomic nervous system
– Prepares the body for intense, energy-consuming activities
28.14 The vertebrate brain develops from three anterior bulges of the neural tube
• The vertebrate brain
– Develops from the forebrain, midbrain, and hindbrain
• The size and complexity of the cerebrum in birds and mammals
– Correlates with their sophisticated behavior
28.15 The structure of a living supercomputer: The human brain
• The human brain
– Is more powerful than the most sophisticated computer
• The human brain is composed of three main parts
– The forebrain, the midbrain, and the hindbrain
• The forebrain’s cerebrum
– Is the largest and most complex part of the brain
• Most of the cerebrum’s integrative power
– Resides in the cerebral cortex of the two cerebral hemispheres
28.16 The cerebral cortex is a mosaic of specialized, interactive regions
• Specialized integrative regions of the cerebral cortex include
– The somatosensory cortex and centers for vision, hearing, taste,
and smell
• The motor cortex
– Directs responses
• Association areas
– Concerned with higher mental activities such as reasoning and
language, make up most of the cerebrum
• The right and left cerebral hemispheres
– Tend to specialize in different mental tasks
28.17 Injuries and brain operations provide insight into brain function
• Brain injuries and surgeries
– Have been used to study brain function
28.18 Several parts of the brain regulate sleep and arousal
• Sleep and arousal involve
–
Activity by the hypothalamus, medulla oblongata, pons, and
neurons of the reticular formation
• The reticular formation
– Receives data from sensory receptors and sends useful data to the
cerebral cortex
• An EEG
– Measures brain waves during sleep and arousal
28.19 The limbic system is involved in emotions, memory, and learning
• The limbic system
– Is a functional group of integrating centers in the cerebral cortex,
thalamus, and hypothalamus
– Is involved in emotions, memory, and learning
20.20 Changes in brain physiology can produce neurological disorders
Schizophrenia
• Schizophrenia is a severe mental disturbance
– Characterized by psychotic episodes in which patients lose the
ability to distinguish reality
Depression
• Two broad forms of depressive illness have been identified
– Major depression and bipolar disorder
• Selective serotonin reuptake inhibitors (SSRIs)
– Are prescribed to treat depression
Alzheimer’s Disease
• Alzheimer’s disease (AD)
– Is characterized by confusion, memory loss, and a variety of other
symptoms
Parkinson’s Disease
• Parkinson’s disease is a motor disorder
– Characterized by difficulty in initiating movements, slowness of
movement, and rigidity
Chapter 30: How Animals Move
• Movement
– Is one of the most distinctive features of animals
30.1 Diverse means of animal locomotion have evolved
• Locomotion, active travel from place to place
– Requires that an animal use energy to overcome friction and
gravity
Swimming
• Animals that swim
– Are supported by water but are slowed by friction
Locomotion on Land: Hopping, Walking, Running, and Crawling
• Animals that walk, hop, or run on land
– Are less affected by friction, but must support themselves against
gravity
Locomotion on Land: Hopping, Walking, Running, and Crawling
• Animals that walk, hop, or run on land
– Are less affected by friction, but must support themselves against
gravity
• Burrowing or crawling animals
– Must overcome friction
– May move by side-to-side undulation or by peristalsis
Flying
• The wings of birds, bats, and flying insects
– Are airfoils, which generate lift
30.2 Skeletons function in support, movement, and protection
• A skeleton has many functions
– Body support
– Movement as muscles pull against it
– Protection of internal organs
Hydrostatic Skeletons
• Hydrostatic skeletons
– Consist of fluid held under pressure in a closed body compartment
– Are found in worms and cnidarians
Exoskeletons
• Exoskeletons are hard external cases
– Such as the chitinous, jointed skeletons of arthropods
– That also include the shells of some molluscs
Endoskeletons
• An endoskeleton consists of hard or leathery supporting elements
– Situated among the soft tissues of an animal
• The vertebrate endoskeleton
– Is composed of cartilage and bone
30.3 The human skeleton is a unique variation on an ancient theme
• The human skeleton consists of
– An axial skeleton (skull, vertebrae, and ribs)
–
An appendicular skeleton (shoulder girdle, upper limbs, pelvic
girdle, and lower limbs)
• The vertebrate skeleton
– Changed dramatically as upright posture and bipedalism evolved
• Movable joints
– Provide the human skeleton with flexibility
30.4 Bones are complex living organs
• Cartilage at the ends of bones
– Cushions the joints
• Bone cells, serviced by blood vessels and nerves
– Live in a matrix of flexible protein fibers and hard calcium salts
• Long bones have a central cavity
– That stores yellow bone marrow, which is mostly stored fat
• Spongy bone contains red marrow
– Where blood cells are made
30.5 Broken bones can heal themselves
• Broken bones
– Are realigned and immobilized
• Bone cells
– Build new bone, healing the break
• Artificial joints
– Are often used to repair severe injuries
30.6 Weak, brittle bones are a serious health problem, even in young people
• Osteoporosis, a bone disease characterized by weak, porous bones
– Is a growing health concern
30.7 The skeleton and muscles interact in movement
• Antagonistic pairs of muscles
– Produce opposite movements
• Muscles perform work
– Only when contracting
30.8 Each muscle cell has its own contractile apparatus
• Skeletal muscle
– Produces body movements
• Muscle fibers, or cells
– Consist of bundles of myofibrils
• Myofibrils
– Contain bundles of overlapping thick (myosin) and thin (actin)
protein filaments
• Sarcomeres
– Are repeating groups of
thick and thin filaments
– Are the contractile units
30.9 A muscle contracts when thin filaments slide across thick filaments
• The sliding-filament model
– Explains muscle contraction
• The myosin heads of the thick filaments
– Bind ATP and extend to high-energy states
• The heads then attach to binding sites on the actin molecules
– And pull the thin filaments toward the center of the sarcomere
30.10 Motor neurons stimulate muscle contraction
• Motor neurons carry action potentials
– That stimulate muscle contraction
• A motor unit consists of
– A neuron and the muscle fibers it controls
• The axon of a motor neuron
– Forms synapses with the muscle at a neuromuscular junction
• Acetylcholine released at a neuromuscular junction triggers an action
potential
– That passes along tubules into the center of the muscle cell
• Calcium released from the endoplasmic reticulum
– Initiates muscle contraction
30.11 Athletic training increases strength and endurance
• A balance of aerobic and anaerobic exercise
– Increases endurance and strength
30.12 The structure-function theme underlies all the parts and activities of an animal
• Animal movement
– Is a visible reminder that function emerges from structure
• An animal’s nervous system
– Connects sensations derived from environmental stimuli to
responses carried out by its muscles
Chapter 9: 9.1 The science of genetics has ancient roots
• The science of heredity dates back to ancient attempts at selective breeding
• Until the 20th century, however, many biologists erroneously believed that
– characteristics acquired during lifetime could be passed on
– characteristics of both parents blended irreversibly in their offspring
9.2 Experimental genetics began in an abbey garden
• Modern genetics began with Gregor Mendel’s quantitative experiments with pea
plants
• Mendel crossed pea plants that differed in certain characteristics and traced the
traits from generation to generation
This illustration shows his technique for cross-fertilization
• Mendel studied seven pea characteristics
He hypothesized that there are alternative forms of genes (although he did not use that
term), the units that determine heredity
9.3 Mendel’s principle of segregation describes the inheritance of a single
characteristic
• From his experimental data, Mendel deduced that an organism has two genes
(alleles) for each inherited characteristic
– One characteristic comes from each parent
• A sperm or egg carries only one allele of each pair
– The pairs of alleles separate when gametes form
• This process describes Mendel’s law of segregation
• Alleles can be dominant or recessive
9.4 Homologous chromosomes bear the two alleles for each characteristic
• Alternative forms of a gene (alleles) reside at the same locus on homologous
chromosomes
9.5 The principle of independent assortment is revealed by tracking two
characteristics at once
• By looking at two characteristics at once, Mendel found that the alleles of a pair
segregate independently of other allele pairs during gamete formation
– This is known as the principle of independent assortment
9.6 Geneticists use the testcross to determine unknown genotypes
The offspring of a testcross often reveal the genotype of an individual when it is
unknown
9.7 Mendel’s principles reflect the rules of probability
• Inheritance follows the rules of probability
– The rule of multiplication and the rule of addition can be used to
determine the probability of certain events occurring
9.8 Connection: Genetic traits in humans can be tracked through family pedigrees
The inheritance of many human traits follows Mendel’s principles and the rules of
probability
Family pedigrees are used to determine patterns of inheritance and individual genotypes
9.9 Connection: Many inherited disorders in humans are controlled by a single
gene
• Most such disorders are caused by autosomal recessive alleles
– Examples: cystic fibrosis, sickle-cell disease
•
A few are caused by dominant alleles
– Examples: achondroplasia, Huntington’s disease
9.10 Fetal testing can spot many inherited disorders early in pregnancy
• Karyotyping and biochemical tests of fetal cells and molecules can help people
make reproductive decisions
– Fetal cells can be obtained through amniocentesis
• Chorionic villus sampling is another procedure that obtains fetal cells for
karyotyping
9.11 The relationship of genotype to phenotype is rarely simple
• Mendel’s principles are valid for all sexually reproducing species
– However, often the genotype does not dictate the phenotype in the simple
way his principles describe
9.12 Incomplete dominance results in intermediate phenotypes
• When an offspring’s phenotype—such
as flower color— is
in between the phenotypes of its parents, it exhibits incomplete dominance
• Incomplete dominance in human hypercholesterolemia
9.12 Incomplete dominance results in intermediate phenotypes
• In a population, multiple alleles often exist for a characteristic
– The three alleles for ABO blood type in humans is an example
– The alleles for A and B blood types are codominant, and both are
expressed in the phenotype
9.14 A single gene may affect many phenotypic characteristics
• A single gene may affect phenotype in many ways
– This is called pleiotropy
– The allele for sickle-cell disease is an example
Genetic testing can be of value to those at risk of developing a genetic disorder or of
passing it on to offspring
9.16 A single characteristic may be influenced by many genes
• This situation creates a continuum of phenotypes
– Example: skin color
9.17 Chromosome behavior accounts for Mendel’s principles
• Genes are located on chromosomes
– Their behavior during meiosis accounts for inheritance patterns
9.18 Genes on the same chromosome tend to be inherited together
•
9.19
•
•
9.20
•
Certain genes are linked
– They tend to be inherited together because they reside close together on
the same chromosome
Crossing over produces new combinations of alleles
This produces gametes with recombinant chromosomes
The fruit fly Drosophila melanogaster was used in the first experiments to
demonstrate the effects of crossing over
Geneticists use crossover data to map genes
Crossing over is more likely to occur between genes that are farther apart
9.21
•
•
•
•
9.22
•
9.23
•
– Recombination frequencies can be used to map the relative positions of
genes on chromosomes
Chromosomes determine sex in many species
A human male has one X chromosome and one Y chromosome
A human female has two X chromosomes
Whether a sperm cell has an X or Y chromosome determines the sex of the
offspring
Other systems of sex determination exist in other animals and plants
Sex-linked genes exhibit a unique pattern of inheritance
All genes on the sex chromosomes are said to be sex-linked
– In many organisms, the X chromosome carries many genes unrelated to
sex
– Fruit fly eye color is a sex-linked characteristic
– Their inheritance pattern reflects the fact that males have one X
chromosome and females have two
– These figures illustrate inheritance patterns for white eye color (r) in the
fruit fly, an X-linked recessive trait
Connection: Sex-linked disorders affect mostly males
Most sex-linked human disorders are due to recessive alleles
– Examples: hemophilia, red-green color blindness
– These are mostly seen in males
– A male receives a single X-linked allele from his mother, and will have
the disorder, while a female has to receive the allele from both parents to
be affected