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Organismal Systems. A Summary of Biological Systems. Chemical Defense Systems. Animal and plants have chemical defenses to fight against foreign invaders. The vertebrate immune system is one of the best studied of these systems. Vertebrate Immune System.

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organismal systems

Organismal Systems

A Summary of Biological Systems

chemical defense systems
Chemical Defense Systems
  • Animal and plants have chemical defenses to fight against foreign invaders.
  • The vertebrate immune system is one of the best studied of these systems.
vertebrate immune system
Vertebrate Immune System
  • The immune system recognizes foreign invaders such as viruses, bacteria, fungi, parasites and other pathogens.
  • Two major modes of attack have evolved:
    • Innate Immunity (Nonspecific, Generalized Attack)
    • Acquired Immunity (Specific, Specialized Attack)
slide4

“Generalized Attack”: these cells wage an instant campaign of destruction against any pathogen while signaling other cells of the presence of intruders

“Specialized Attack”: these cells wage a more specific and enduring attack and are capable of producing lasting immunity against specific invaders.

lines of defense
Lines of Defense
  • The immune system has

3 main lines of defense:

    • 1st line: Physicalbarriers, chemical barriers, and mechanical barriers.
    • 2nd line: Phagocytes, complement, inflammation, fever
    • 3rd line: Cell-mediated and humoral

Innate and Nonspecific

Acquired and Specific

innate vs acquired immunity
Innate vs. Acquired Immunity
  • Innate Immunity: is present at birth (before exposure to pathogens), is nonspecificand consists of external barriers plus internal cellular and chemical defenses
  • Acquired Immunity:develops after exposure to foreign invaders and involves a very specific response to pathogens.
slide7

Fig. 43-2

Pathogens

(microorganisms

and viruses)

Barrier defenses:

Skin

Mucous membranes

Secretions

INNATE IMMUNITY

Recognition of traits

shared by broad ranges

of pathogens, using a

small set of receptors

Internal defenses:

Phagocytic cells

Antimicrobial proteins

Inflammatory response

Natural killer cells

Rapid response

Humoral response:

Antibodies defend against

infection in body fluids.

ACQUIRED IMMUNITY

Recognition of traits

specific to particular

pathogens, using a vast

array of receptors

Cell-mediated response:

Cytotoxic lymphocytes defend

against infection in body cells.

Slower response

a microbe invading the body will encounter the following defenses
A Microbe Invading the Body will Encounter the Following Defenses:
  • 1st Line of Defense:
    • Barrier defenses:
      • Skin: physical barrier prevents entry into body: low pH prevents microbial growth
      • Mucous membranes of respiratory, urinary, and reproductive tracts: traps microbes, low pH of body fluids is hostile to microbes
once past the 1 st line
Once past the 1st line:
  • 2nd Line of Defense:
    • White blood cells are the key players in a series of increasingly specific attacks against invading microbes.
      • White blood cells (leukocytes): engulf a pathogen in the body and trap it within a vacuole. The vacuole then fuses with a lysosome to destroy the microbe (phagocytosis). Many cells are involved in this “Generalized Attack”
the generalized attack
The Generalized Attack
  • “On-the-ready” cellsof the generalized attack:
    • Neutrophils: “eat” pathogens and send out distress signals.
    • Macrophages: arise from monocytes. They are the “big eaters”. They circulate through the lymph system looking for any foreign invader. Some reside permanently in the spleen and lymph nodes, lying in wait for microbes.
    • Eosinophils: release destructive enzymes to attack large invaders like parasitic worms. Also involved in the inflammatory response.
    • Basophils: contain histamines that are released during the inflammatory response.
    • Dendritic cells: arise from monocytes. They stimulate the development of acquired immunity.
slide11

Notice that all of the immune cells are derived from a multi-potent cell in the bone marrow known as a Hematopoietic stem cell.

(Dendritic cells not shown)

proteins complement and inflammation
Proteins, Complement and Inflammation
  • The remaining components of the 2nd line of defense do not involve white blood cells.
    • Peptidesand proteinsattack microbes directly or impede their reproduction.
      • Example: Interferon proteins provide innate defense against virusesand help to activate microphages.
slide13

Interferon produced by one infected cell can induce nearby cells to produce substances that interfere with viral reproduction. This limits the cell-to-cell spread of viruses

slide14

About 30 proteins make up the complement system, which causes lysisof invading cells and helps trigger inflammation

inflammatory responses
Inflammatory Responses
  • Following an injury, mast cells release histamine, which promotes changes in blood vessels; this is part of the inflammatory response
  • These changes increase local blood supply and allow more phagocytesand antimicrobial proteins to enter tissues.
  • Pus (a fluid rich in white blood cells, dead microbes, and cell debris) accumulates at the site of inflammation.
slide16

Fig. 43-8-1

Pathogen

Splinter

Chemical

signals

Macrophage

Mast cell

Capillary

Red blood cells

Phagocytic cell

slide17

Fig. 43-8-2

Pathogen

Splinter

Chemical

signals

Macrophage

Fluid

Mast cell

Capillary

Red blood cells

Phagocytic cell

slide18

Fig. 43-8-3

Pathogen

Splinter

Chemical

signals

Macrophage

Fluid

Mast cell

Capillary

Phagocytosis

Red blood cells

Phagocytic cell

slide19

Symptoms of inflammation include redness, warmth, pain, and swelling.

  • Inflammation can be either local or systemic (throughout the body)
  • Feveris a systemic inflammatory response triggered by pyrogensreleased by macrophages, and toxins from pathogens.
  • Septic shock is a life-threatening condition caused by an overwhelming inflammatory response.
natural killer cells
Natural Killer Cells
  • The last component of the innate immune system are the natural killer cells.
  • All cells in the body (except red blood cells) have a class 1 MHC protein on their surface. (major histocompatibility complex)
  • Cancerous or infected cells no longer express this protein
  • Natural killer (NK) cells attack these damaged cells, inhibiting further spread of the virus or cancer.
evading the innate immune system
Evading the Innate Immune System
  • Some pathogens evade the innate immune attack by modifying their surface to prevent recognition or by resisting breakdown following phagocytosis.
  • Example: Tuberculosis (TB)—these bacterium are resistant to the enzymes inside the lysosomes. Thus, they can hide inside white blood cells without being digested. This disease kills more than a million people per year.
acquired immunity
Acquired Immunity
  • The 3rd Line of Defense:
    • White blood cells called lymphocytes recognize and respond to antigens(foreign molecules).
    • Lymphocytes that mature in the thymusabove the heart are called T cells, and those that mature in bone marrow are called B cells.
    • These are the cells involved in the “Specialized Attack”
slide23

Lymphocytes contribute to immunological memory, an enhanced response to a foreign molecule encountered previously. This is what allows us to develop lifetime immunity to diseases like chickenpox.

  • The specialized attack usually occurs after being signaled by cells already involved in the generalized attack.
    • Cytokinesare secreted by macrophages and dendritic cells to recruit and activate lymphocytes.
the specialized attack
The Specialized Attack
  • The three stars of this more specialized attack are the B cells, Helper T cells, and Killer T cells (cytotoxic T cells).
    • B cells mature into plasma cells that generate highly specific antibodiescapable of lasting immunity.
    • Helper T cells play a central role in coordinating the attack
    • Killer T cells, once activated, destroy virus-infected cells.
slide26

B cells and T cells have receptor proteins that can bind to foreign molecules.

  • Each individual lymphocyte is specialized to recognize a specific type of molecule.
antigen recognition by lymphocytes
Antigen Recognition by Lymphocytes
  • An antigenis any foreign molecule to which a lymphocyte responds
  • A single B cell or T cell has about 100,000 identical antigen receptors.
  • A typical immune response to a virus is seen in the following diagram.
slide29

From the diagram, we can see that there are two types of specific responses: humoral response (involving B-cells)and cell mediated response (involving cytotoxic T-cells)

  • The helper T cells can initiate both responses.
antigen recognition
Antigen Recognition
  • Recognition of the antigen begins when a macrophage(as seen in the diagram), a B-cell, or a dendritic cell presents the foreign antigen by engulfing the invader, digesting the particle, and then presenting the antigen on the cell’s surface.
    • MHC molecules (major histocompatibility complex) are used to present the antigens
slide31

Fig. 43-12

Microbe

Antigen-

presenting

cell

Infected cell

1

Antigen

associates

with MHC

molecule

Antigen

fragment

Antigen

fragment

1

1

Class I MHC

molecule

Class II MHC

molecule

2

2

T cell

receptor

T cell

receptor

2

T cell

recognizes

combination

(a)

Cytotoxic T cell

(b)

Helper T cell

Class II are on macrophages,

dendritic cells or B cells. Display

to cytotoxic T cells and Helper T cells

Class I are found on body cells.

Display antigens to cytotoxic T cells

slide32

Helper T cells then bindto the presented antigen and signalthe production of more T and B cells by releasing cytokines.

  • This initiates both the humoral and the cell-mediated response.
the humoral response
The Humoral Response
  • In the humoral response, activated B cells give rise to plasma cells, which secrete antibodies or immunoglobulins (Ig) specific to the antigen presented.
  • Memory B cells also form during the humoral response and persist long after the initial infection ends.
slide34

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 role of antibodies
The Role of Antibodies
  • By binding to a pathogen, antibodies can neutralizethe pathogen so that it can no longer infect a host cell.
  • By binding to a pathogen, antibodies can flagthem so that they are more easily and quickly identified and destroyed by phagocytic cells.
  • Antibodies, together with proteins of the complement system generate a membrane attack complex and cell lysis.
slide36

Fig. 43-21

Viral neutralization

Opsonization

Activation of complement system and pore formation

Bacterium

Complement proteins

Virus

Formation of

membrane

attack complex

Flow of water

and ions

Macrophage

Pore

Foreign

cell

the cell mediated response
The Cell-Mediated Response
  • In the cell-mediated response, cytotoxic T- cells target intracellular pathogens which B-cells cannot recognize.
  • Antibodies are not used.
  • Cytotoxic T-cells and Natural Killer cells detect and destroy altered or infected body cells.
  • Memory T-cells are also generated.
slide38

Fig. 43-16

Humoral (antibody-mediated) immune response

Cell-mediated immune response

Key

Antigen (1st exposure)

Stimulates

Gives rise to

+

Engulfed by

Antigen-

presenting cell

+

+

+

B cell

Helper T cell

Cytotoxic T cell

+

+

Memory

Helper T cells

+

+

+

Antigen (2nd exposure)

Memory

Cytotoxic T cells

Active

Cytotoxic T cells

+

Plasma cells

Memory B 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.

primary and secondary responses
Primary and Secondary Responses
  • The first exposure to a specific antigen represents the primary immune response.
  • During this time, plasma cells are generated, T cells are activated, antibodiesand memory B and T cells are produced.
  • In the secondary immune response, memory cells facilitate a faster, more efficient response.
slide40

Fig. 43-15

Primary immune response

to antigen A produces

antibodies to A.

Secondary immune response to

antigen A produces antibodies to A;

primary immune response to antigen

B produces antibodies to B.

104

103

Antibody concentration

(arbitrary units)

Antibodies

to A

Antibodies

to B

102

101

100

0

7

14

21

28

35

42

49

56

Exposure

to antigen A

Exposure to

antigens A and B

Time (days)

lymphocyte development
Lymphocyte Development
  • The acquired immune system has three important properties
    • Receptor diversity—our cells have an amazing ability to rearrange genes to generate over 1 million different B cells and 10 million different T cells.
    • A lack of reactivity against host cells—as lymphocytes mature, any that exhibit receptors specific for the body’s own molecules are destroyed by apoptosis.
    • Immunological memory—there is an increase in cell number and behavior triggered by the binding of antigen that allows the immune system to “remember attackers”
active and passive immunity
Active and Passive Immunity
  • Active immunity develops naturally in response to an infection.
    • It can also develop following immunization, also called vaccination.
  • Passive immunity provides immediate, short-term protection
    • It is conferred naturally when antibodies cross the placenta from mother to fetus or from mother to infant in breast milk.
    • It can be conferred artificially by injecting antibodies into a non-immune person
immune rejection
Immune Rejection
  • Cells transferred from one person to another can be attacked by immune defenses
  • This complicates blood transfusions and organ transplants.
  • MHC molecules are different from person to person and this difference stimulates most organ rejections.
    • Successful transplants try to match MHC tissue types and utilize immunosuppressive drugs.
blood groups
Blood Groups
  • Antigens on red blood cells determine whether a person has blood type A (A antigen), B (B antigen), AB (both A and B antigens), or O (neither antigen)
  • Antibodies to nonself blood types exist in the body
  • Transfusion with incompatible blood leads to destruction of the transfused cells
  • Recipient-donor combinations can be fatal or safe
disruptions of immune system function
Disruptions ofImmune System Function
  • Allergies: exaggerated responses to certain antigens called allergens
  • Anaphylactic shock: an acute, allergic, life-threatening reaction that can occur within seconds of allergen exposure
slide46

Autoimmune Diseases: the immune system loses tolerance for self and turns against certain molecules of the body.

    • Examples: Lupus, rheumatoid arthritis, and multiple sclerosis.
slide47

Acquired Immunodeficiency Syndrome (AIDS):

    • Caused by human immunodeficiency virus(HIV)
    • Infects Helper T-cells
    • Impairs both the humoral and the cell-mediated immune responses.
    • HIV eludes the immune system because of antigenic variation and an ability to remain latent while integrated into host DNA.
    • People with AIDS are highly susceptible to opportunistic infections and cancersthat take advantage of an immune system in collapse.
slide48

Cancer: The frequency of certain cancers increases when the immune response is impaired.

  • Two suggested explanations are:
    • Immune system normally suppresses cancerous cells
    • Increased inflammation increases the risk of cancer.
eliminating wastes and obtaining nutrients
Eliminating Wastes and Obtaining Nutrients
  • Organisms have a variety of mechanisms for obtaining nutrients and eliminating wastes.
  • These mechanisms all contribute to maintaining homeostasis in living things.
removal of nitrogen waste
Removal of Nitrogen Waste
  • All animals must regulate the amount of, and composition of, their body fluids.
  • Examples:
    • Sponges: have no excretory organs,: nitrogen waste diffuses out across the body wall.
    • Flatworms: have a tubular excretory organ that delivers nitrogen waste in the form of ammonia to a special pore in the body surface.
    • Insects: convert ammonia to uric acidto reduce water loss.
    • Vertebrates: have a urinary system with two kidneys that filters the blood and adjusts its solute concentration.
circulation and gas exchange
Circulation and Gas Exchange
  • In most organisms, circulation and gas exchange play a critical role in carrying nutrients and oxygen to cells and assisting in the removal of wastes.
circulation and gas exchange1
Circulation and Gas Exchange
  • In most animals, the circulatory and respiratory systems are closely linked.
    • In small and/or thin animals, cells can exchange materials directlywith the surrounding medium
    • In other animals, transport systems connect the organs of exchange with the body cells.
    • Most complex animals have internal transport systems that circulate fluid.
gastrovascular cavities
Gastrovascular Cavities
  • Simple animals, such as cnidarians and flatworms, have a body wall that is only two cells thick and encloses a gastrovascular cavity.
  • This cavity functions in both digestion and distribution of substances throughout the body.
slide54

Fig. 42-2

Circular

canal

Mouth

Pharynx

Mouth

Radial canal

5 cm

2 mm

(a) The moon jelly Aurelia, a cnidarian

(b)

The planarian Dugesia, a

flatworm

open and closed circulatory systems
Open and Closed Circulatory Systems
  • More complex animals have either open or closed circulatory systems.
  • Both systems have three basic components:
    • A circulatory fluid (blood or hemolymph)
    • A set of tubes (blood vessels)
    • A muscular pump (the heart)
slide56

In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system

    • There is no distinction between blood and interstitial fluid, and this general body fluid is more correctly called hemolymph.
  • Vertebrate animals have a closed circulatory system in which blood is confined to vessels and is distinct from the interstitial fluid.
    • Closed systems are more efficient.
slide57

Fig. 42-3

Heart

Heart

Blood

Hemolymph in sinuses

surrounding organs

Small branch vessels

In each organ

Interstitial

fluid

Pores

Dorsal vessel

(main heart)

Tubular heart

Auxiliary hearts

Ventral vessels

(a) An open circulatory system

(b) A closed circulatory system

organization of vertebrate circulatory systems
Organization of Vertebrate Circulatory Systems
  • The circulatory system is an example of a homeostatic mechanism that supports the idea of common ancestry.
  • It carries nutrients and oxygen to cells and assists in the removal of wastes from cells.
  • All vertebrate circulatory systems are closed (common ancestry)
  • However, there are variations between fish, amphibians, and mammals that have evolved over millions of years (diversity)
slide59

Fish: heart has two chambers (one atrium and one ventricle) and blood flows through one circuit. It picks up oxygen in the capillary beds of the gills and delivers it to capillary beds in all body tissue.

  • Amphibians: heart has three chambers (two atria and one ventricle) and blood flows along two partially separated circuits. Oxygenated blood and oxygen-poor blood mix a bit in the ventricle.
  • Mammals and Birds: heart has four chambers (two atria and two ventricles) and blood flows through two fully separated circuits. One goes to the lungs and back and the second goes from the heart to all body tissues and back. This keeps oxygen rich blood completely separate from the oxygen poor blood.
slide60

Fig. 42-4

Gill capillaries

Gill

circulation

Artery

Ventricle

Heart

Atrium

Systemic

circulation

Vein

Systemic capillaries

slide61

Fig. 42-5

Amphibians

Reptiles (Except Birds)

Mammals and Birds

Lung and skin capillaries

Lung capillaries

Lung capillaries

Right

systemic

aorta

Pulmocutaneous

circuit

Pulmonary

circuit

Pulmonary

circuit

Atrium (A)

Atrium (A)

A

A

A

A

V

V

Ventricle (V)

V

V

Left

systemic

aorta

Left

Right

Left

Right

Right

Left

Systemic

circuit

Systemic

circuit

Systemic capillaries

Systemic capillaries

Systemic capillaries

mammalian circulation
Mammalian Circulation
  • Mammals provide an excellent example of double circulation.
  • Blood begins its flow with the right ventricle pumping blood to the lungs
  • In the lungs, the blood loads O2and unloads CO2
  • Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped through the aortato the body tissues by the left ventricle
  • The aorta provides blood to the heart through the coronary arteries
slide63

Blood returns to the heart through the superior vena cava (blood from head, neck, and forelimbs) and inferior vena cava (blood from trunk and hind limbs)

  • The superior vena cava and inferior vena cavaflow into the right atrium
  • Four valves prevent backflow of blood in the heart.
    • Two atrioventricular (AV) valves separate each atrium and ventricle.
    • The semilunar valves control blood flow to the aorta and the pulmonary artery.
slide64

Fig. 42-6

Capillaries of

head and

forelimbs

Superior

vena cava

7

Pulmonary

artery

Pulmonary

artery

Capillaries

of right lung

Aorta

9

Capillaries

of left lung

3

3

2

4

11

Pulmonary

vein

Pulmonary

vein

5

1

Right atrium

Left atrium

10

Right ventricle

Left ventricle

Inferior

vena cava

Aorta

Capillaries of

abdominal organs

and hind limbs

8

slide65

Fig. 42-7

Pulmonary artery

Aorta

Pulmonary

artery

Right

atrium

Left

atrium

Semilunar

valve

Semilunar

valve

Atrioventricular

valve

Atrioventricular

valve

Right

ventricle

Left

ventricle

the mammalian heart
The Mammalian Heart
  • A closer look at the mammalian heart provides a better understanding of double circulation.
  • The contraction, or pumping, phase is called systole.
  • The relaxation, or filling, phase is called diastole.
slide67

Fig. 42-8-1

Semilunar

valves

closed

AV

valves

open

0.4 sec

1

Atrial and

ventricular

diastole

slide68

Fig. 42-8-2

Atrial systole;

ventricular

diastole

2

Semilunar

valves

closed

0.1 sec

AV

valves

open

0.4 sec

1

Atrial and

ventricular

diastole

slide69

Fig. 42-8

Atrial systole;

ventricular

diastole

2

Semilunar

valves

closed

0.1 sec

Semilunar

valves

open

AV

valves

open

0.4 sec

0.3 sec

1

Atrial and

ventricular

diastole

AV valves

closed

3

Ventricular systole;

atrial diastole

vessels of the circulatory system
Vessels of the Circulatory System
  • Three main blood vessels are: arteries, veins and capillaries
    • Arteries: carry oxygenated blood awayfrom heart; branch into arteriolesand then to capillaries
    • Capillaries: form a network known as capillary beds; provide the site for chemical exchange between the blood and interstitial fluid.
    • Veins: carry deoxygenatedblood backto heart; capillaries converge into venulesand then into veins
slide71
The critical exchange of substances between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries
  • The difference between blood pressure and osmotic pressure drives fluids outof capillaries at the arteriole end and intocapillaries at the venule end
slide72

Fig. 42-16

Body tissue

INTERSTITIAL FLUID

Capillary

Net fluid

movement out

Net fluid

movement in

Direction of

blood flow

Blood pressure

Inward flow

Pressure

Outward flow

Osmotic pressure

Arterial end of capillary

Venous end

slide73
The lymphatic system returns fluid that leaks out in the capillary beds
  • This system aids in body defense
  • Fluid, called lymph, reenters the circulation directly at the venous end of the capillary bed and indirectly through the lymphatic system
  • The lymphatic system drains into veins in the neck
slide74
Lymph nodes are organs that filter lymphand play an important role in the body’s defense
  • Edemais swelling caused by disruptions in the flow of lymph
gas exchange
Gas Exchange
  • Gas exchange supplies oxygen for cellular respiration and disposes of carbon dioxide.
  • Gases like O2 and CO2, diffuse down pressure gradients in the lungs and other organs from where their partial pressures are higher to where they are lower.
respiratory media
Respiratory Media
  • Animals can use air or water as a source of oxygen.
  • Obtaining oxygen from water actually requires greater efficiency than air breathing since there is less oxygen available in water than in air.
  • Gas exchange takes place by diffusionacross either the skin, gills, tracheae, or lungs.
  • All respiratory organs increase surface area for gas exchange.
gills
Gills
  • Gills are out foldingsof the body
  • Fish move water over their gills and use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets.
slide78

Fig. 42-22

Fluid flow

through

gill filament

Oxygen-poor blood

Anatomy of gills

Oxygen-rich blood

Gill

arch

Lamella

Gill

arch

Gill filament

organization

Blood

vessels

Water

flow

Operculum

Water flow

between

lamellae

Blood flow through

capillaries in lamella

Countercurrent exchange

PO2 (mm Hg) in water

150

120

90

60

30

Gill filaments

Net diffu-

sion of O2

from water

to blood

110

80

50

20

140

PO2 (mm Hg) in blood

tracheal systems
Tracheal Systems
  • The tracheal system of insects consists of tiny branching tubes that penetrate the body.
  • These tubes supply O2directly to body cells.
  • The respiratory and circulatory systems are separate.
  • Larger insects must ventilate their tracheal system to meet O2 demands.
slide80

Fig. 42-23

Air sacs

Tracheae

External

opening

Tracheoles

Mitochondria

Muscle fiber

Body

cell

Air

sac

Tracheole

Trachea

Body wall

Air

2.5 µm

lungs
Lungs
  • Lungs are in-foldings of the body surface.
  • The circulatory system (open or closed) transports gases between the lungs and the rest of the body.
  • Air inhaled through the nostrils passes through the pharynx to the larynx, trachea, bronchi, bronchioles, and alveoli.
slide82

Fig. 42-24

Branch of

pulmonary

vein

(oxygen-rich

blood)

Branch of

pulmonary

artery

(oxygen-poor

blood)

Terminal

bronchiole

Nasal

cavity

Pharynx

Larynx

Alveoli

(Esophagus)

Left

lung

Trachea

Right lung

Bronchus

Bronchiole

Diaphragm

Heart

SEM

Colorized

SEM

50 µm

50 µm

how animals breath
How animals breath
  • An amphibian ventilates its lungs by positive pressure breathing, which forces air down the trachea.
  • Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs.
  • In either case, the gas exchange must be coordinated with circulation.
coordination of circulation and gas exchange
Coordination of Circulation and Gas Exchange
  • Blood arriving in the lungs has a low partial pressure of O2 and a high partial pressure of CO2 relative to air in the alveoli
  • In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air
  • In tissue capillaries, partial pressure gradients favor diffusion of O2 into the interstitial fluids and CO2 into the blood
respiratory pigments
Respiratory Pigments
  • Respiratory pigments, proteins that transport oxygen, greatly increase the amount of oxygen that blood can carry
  • Arthropods (other than insects) and many molluscs have hemocyaninwith copperas the oxygen-binding component
  • Most vertebrates and some invertebrates use hemoglobincontained within erythrocytes
carbon dioxide transport
Carbon Dioxide Transport
  • Hemoglobin also helps transport CO2 and assists in buffering
  • CO2from respiring cells diffuses into the blood and is transported either in blood plasma, bound to hemoglobin, or as bicarbonate ions (HCO3–)
developmental regulation
Developmental Regulation
  • Many mechanisms control the development of an organism.
  • All cells in a multicellullular organism are derived from the same fertilized egg and contain the same genes.
  • Differentiation is the process in which cells become specialized to express certain genes.
slide88

Example: all cells express genes that code for the enzymes of glycolysis: but only red blood cells express the genes that code for hemoglobin.

  • Most cells use less than 10% of their genes
  • Cells contain transcription factors (regulatory proteins) that turn on certain genes
master genes
Master Genes
  • Master genes control other genes.
    • Example: Homeotic genes (a type of master gene)code for the transcription factors needed to express certain other genes. The products of these homeotic genes cause cells to differentiate into tissues that form specific structures like the head.
    • The products of these genes create gradients which affect other genes.
    • Thus, development of an embryo is controlled layer after layer by master genes.
apoptosis
Apoptosis
  • Apoptosis (programmed cell death) also plays a role in normal development.
  • Many cells must self destruct at a specific time in order to ensure proper development.
  • Example: Formation of human hand
nervous system
Nervous System
  • Many animals have a complex nervous system that consists of:
    • A central nervous system (CNS): where integration takes place. Consists of brain and spinal cord.
    • A peripheral nervous system (PNS): brings information into and out of the CNS.
introduction to information processing
Introduction to Information Processing
  • Nervous systems process information in three stages: sensory input, integration, and motor output
slide94
Sensory receptors collect information from both outside and inside the body. Ex: rods and cones of the eyes; pressure receptors in the skin. They send this information along sensory neurons to the brain or ganglia.
  • Here interneuronsconnect sensory and motor neurons or make local connections in the brain and spinal cord.
  • Motor output leaves the brain or ganglia via motor neurons, which transmit signals to effectors, such as muscle cells and glands, to trigger a response.
slide95

Fig. 48-3

Sensory input

Integration

Sensor

Motor output

Central nervous

system (CNS)

Effector

Peripheral nervous

system (PNS)

neurons
Neurons
  • Neurons = nerve cells
    • Use two types of signals: electrical signals (long distance) and chemical signals (short distance)
    • 3 parts:
      • Cell body—contains the nucleus and organelles
      • Dendrites—short extensions: receive incoming messages from other cells
      • Axons—long extensions: transmit messages to other cells.
    • A Synapse is a junction between an axon and another cell.
slide97
The synaptic terminal of one axon passes information across the synapse in the form of chemical messengers called neurotransmitters
  • Examples of neurotransmitters include acetylcholine, dopamine, and serotonin.
  • Information is transmitted from a presynaptic cell (a neuron) to a postsynaptic cell(a neuron, muscle, or gland cell)
  • Most neurons are nourished or insulated by cells called glia
slide98

Fig. 48-4

Dendrites

Stimulus

Presynaptic

cell

Nucleus

Axon

hillock

Cell

body

Axon

Synapse

Synaptic terminals

Postsynaptic cell

Neurotransmitter

ion pumps and ion channels
Ion pumps and ion channels
  • Membrane potential (Voltage) is the difference in electrical charge across the plasma membrane of a cell.
  • Messages are transmitted as changes in membrane potential
  • The resting potential is the membrane potential of a neuron at rest.
formation of the resting potential
Formation of the Resting Potential
  • In a mammalian neuron at resting potential, the concentration of K+ is greater inside the cell, while the concentration of Na+ is greater outside the cell
  • Sodium-potassium pumps use the energy of ATP to maintainthese K+ and Na+gradientsacross the plasma membrane
  • These concentration gradients represent chemical potential energy
slide101

Fig. 7-16-7

EXTRACELLULAR

FLUID

Na+

[Na+] high

Na+

[K+] low

Na+

Na+

Na+

Na+

Na+

Na+

ATP

[Na+] low

P

Na+

P

[K+] high

CYTOPLASM

ADP

2

3

1

K+

K+

K+

K+

K+

P

K+

P

6

5

4

slide102
The opening of ion channels in the plasma membrane converts chemical potential to electrical potential
  • A neuron at resting potential contains many open K+ channels and fewer open Na+ channels; K+ diffuses out of the cell
  • Anionstrapped inside the cell contribute to the negative charge within the neuron
slide103

Fig. 48-6a

OUTSIDE

CELL

[Na+]

150 mM

[Cl–]

120 mM

[K+]

5 mM

[A–]

100 mM

[K+]

140 mM

INSIDE

CELL

[Na+]

15 mM

[Cl–]

10 mM

(a)

slide104

Fig. 48-6b

Key

Sodium-

potassium

pump

Na+

Potassium

channel

Sodium

channel

K+

OUTSIDE

CELL

INSIDE

CELL

(b)

the generation of action potentials
The Generation of Action Potentials
  • The signals carried by axons are called Action Potentials.
  • An Action potential begins when gated ion channels opens or closes in response to stimuli which changes the membrane potential of the cell.
  • The potassium and sodium gates are the most important for stimulating action potentials.
slide106

When gated K+ channels open, K+ diffuses out, making the inside of the cell more negative

  • This is hyperpolarization
  • If gated Na+ channels open and Na+ diffuses into the cell, then the inside of the cell is more positive
  • This is depolarization.
  • Graded potentials are changes in polarization where the magnitude of the change varies with the strength of the stimulus
slide107

Fig. 48-9a

Stimuli

+50

Hyperpolarization

0

Membrane potential (mV)

–50

Threshold

Resting

potential

Hyperpolarizations

–100

1

5

2

3

4

0

Time (msec)

(a) Graded hyperpolarizations

slide108

Fig. 48-9b

Stimuli

+50

Depolarization

0

Membrane potential (mV)

Threshold

–50

Resting

potential

Depolarizations

–100

0

1

5

2

3

4

Time (msec)

(b) Graded depolarizations

slide109

An action potential is a brief all-or-none depolarization of a neuron’s plasma membrane

  • It occurs if a stimulus causes the membrane voltage to cross a particular threshold
  • A neuron can produce hundreds of action potentials per second
  • The frequency of action potentials can reflect the strength of a stimulus
slide110
At resting potential
    • Most voltage-gated Na+ and K+ channels are closed, but some K+ channels (not voltage-gated) are open
slide111

Fig. 48-10-1

Key

Na+

K+

+50

Action

potential

3

0

Membrane potential

(mV)

2

4

Threshold

–50

1

1

5

Resting potential

Depolarization

–100

Time

Extracellular fluid

Sodium

channel

Potassium

channel

Plasma

membrane

Cytosol

Inactivation loop

Resting state

1

slide112
When an action potential is generated
    • Voltage-gated Na+ channels open first and Na+ flows into the cell
    • During the rising phase, the threshold is crossed, and the membrane potential increases
    • During the falling phase, voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell
slide113

Fig. 48-10-2

Key

Na+

K+

+50

Action

potential

3

0

Membrane potential

(mV)

2

4

Threshold

–50

1

1

5

Resting potential

Depolarization

2

–100

Time

Extracellular fluid

Sodium

channel

Potassium

channel

Plasma

membrane

Cytosol

Inactivation loop

Resting state

1

slide114

Fig. 48-10-3

Key

Na+

K+

Rising phase of the action potential

3

+50

Action

potential

3

0

Membrane potential

(mV)

2

4

Threshold

–50

1

1

5

Resting potential

Depolarization

2

–100

Time

Extracellular fluid

Sodium

channel

Potassium

channel

Plasma

membrane

Cytosol

Inactivation loop

Resting state

1

slide115

Fig. 48-10-4

Key

Na+

K+

Falling phase of the action potential

4

Rising phase of the action potential

3

+50

Action

potential

3

0

Membrane potential

(mV)

2

4

Threshold

–50

1

1

5

Resting potential

Depolarization

2

–100

Time

Extracellular fluid

Sodium

channel

Potassium

channel

Plasma

membrane

Cytosol

Inactivation loop

Resting state

1

slide116
During the undershoot, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close; resting potential is restored
slide117

Fig. 48-10-5

Key

Na+

K+

Falling phase of the action potential

4

Rising phase of the action potential

3

+50

Action

potential

3

0

Membrane potential

(mV)

2

4

Threshold

–50

1

1

5

Resting potential

Depolarization

2

–100

Time

Extracellular fluid

Sodium

channel

Potassium

channel

Plasma

membrane

Cytosol

Inactivation loop

Undershoot

5

Resting state

1

saltatory conduction
Saltatory Conduction
  • Action potentials travel in one direction only.
  • Their speed is influenced by the myelin sheath (insulating layer of glia cells)
  • Action potential form only at the Nodes of Ranvier(gaps in the myelin sheath)
  • They jump from node to node in a movement called, saltatory conduction, which greatly increases their speed.
slide119

Fig. 48-13

Schwann cell

Depolarized region

(node of Ranvier)

Cell body

Myelin

sheath

Axon

synapses
Synapses
  • Nerve cells communicate with each other at gaps known as synapses
  • Most synapses are chemical synapses and involve neurotransmitters.
  • Action potentials cause the release of neurotransmitters.
  • They travel across the synaptic cleft and affect the post synaptic cell.
  • Neurotransmitters can be excitatory or inhibitory.
slide121

Fig. 48-15

5

Na+

K+

Synaptic vesicles

containing

neurotransmitter

Presynaptic

membrane

Voltage-gated

Ca2+ channel

Postsynaptic

membrane

Ca2+

1

4

6

2

3

Synaptic

cleft

Ligand-gated

ion channels