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Lecture 11 Outline (Ch. 42)

I. Circulatory Systems

II. Human Heart

III. Blood & Vessels

IV. Cardiovascular disorders

V. Methods – bulk flow vs. diffusion

VII. Gas exchange and partial pressures

VIII. Breathing mechanisms

IX. Preparation for next lecture

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Circulation carries energy, dissolved gasses, wastes

• Connects individual cells in distant parts of body

• Requirements– Blood – fluid for transport– Blood vessels – channels for

transport– Heart – pump for circulation

Circulation Overview

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Circulatory systems are open or closed• Open- bathes organs in a hemocoel • Closed- direct vessel connections to organs

Circulation Overview

Heart

Hemolymph in sinusessurrounding organs

Heart

Interstitialfluid

Small branch vesselsIn each organ

Blood

Dorsal vessel(main heart)

Auxiliary hearts Ventral vessels

(b) A closed circulatory system(a) An open circulatory system

Tubular heart

Pores

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Vertebrates have a closed circulatory system

• More efficient– Blood is 5 – 10% of body volume– Flow is more rapid, pressure is higher

• Multifunctional– Transport dissolved gasses– Distribute nutrients & hormones– Transport waste– Thermoregulation– Circulate immunodefenses

Circulation Overview

Arteries – away from heart, Veins – toward heart

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• Set of muscular chambers

• Atria collect blood• Ventricles send blood

through body

• The heart has evolved

The Vertebrate Heart

Ventricle gill capillaries: gas exchange

Blood collects - body capillaries gas exchange

Blood returns to heart, swimming helps

Single circulation

Artery

Heart:

Atrium (A)

Ventricle (V)

Vein

Gillcapillaries

Bodycapillaries

Key

Oxygen-rich blood

Oxygen-poor blood

Bony fishes, rays, sharks

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The Vertebrate Heart

2 atria empty into 2 ventricles

Complete septum (this varies) – right side receives oxygen poor blood from body – sends to lungs

Endotherms need to deliver 10X as much dissolved gasses and nutrients/waste as same size ectotherms!

Systemic circuit

Systemiccapillaries

Right Left

A A

VV

Lungcapillaries

Pulmonary circuit

Key

Oxygen-rich blood

Oxygen-poor blood

Amphibians, reptiles, mammals

Double circulation – pulmonary circuit and systemic circuit

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4-chambered heart: A closer look

• 2 pumps• Right:

deoxygenated blood

• Left: oxygenated blood

Heart

Pulmonary artery

Rightatrium

Semilunarvalve

Atrioventricularvalve

Rightventricle

Leftventricle

Atrioventricularvalve

Semilunarvalve

Leftatrium

Pulmonaryartery

Aorta

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Right ventricle pumps deO2 blood to lungs through pulmonary arteries

Pumps into right ventricle

Heart• Right atrium receives deO2 blood from veins

– Superior vena cava

– Inferior vena cava

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• Oxygenated blood returns to left atrium from lungs via pulmonary veins

Oxygenated blood pumped to body through aorta

Pumps into left ventricle

Heart

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Keeping blood moving• Heart valves maintain

one-way flow• Atrioventricular valves

– Between atria & ventricles

• Semilunar valves– Between ventricles &

arteries

Heart

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The Cardiac Cycle

Heart

Atrial andventricular diastole

0.4sec

1

Atrial systole and ventricular diastole

0.1sec

2

Ventricular systole and atrialdiastole

0.3 sec

3

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The Cardiac Cycle & Blood Pressure

Heart

Normal blood pressure ~120/70

• “Lub-dup” sounds heard with stethoscope– Lub – blood against closed AV valves– Dup – blood against closed semilunar valves

• Systolic– Ventricular contractions

(higher pressure)• Diastolic

– Period between contractions (lower pressure)

sphygmomanometer

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Cardiac muscle contracts

• Present only in the heart

Heart

Cells linked by intercalated discs

Prevents strong contractions from tearing muscle

Allows rapid spread of electrical signal for

simultaneous regional

contraction

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Keeping blood moving• Pacemaker cells initiate and

coordinate contractions• Sinoatrial (SA) node

– Primary pacemaker– Stimulates atrial contractions

• Atrioventricular (AV) node– Delayed impulse received from

SA node– Ventricular contraction after

atrial contractions have filled them with blood (delay ~0.1 sec)

Heart

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Plasma • Primarily water• Dissolved proteins and electrolytes

Blood

Blood • Plasma fluid• Cells

– Red blood cells – transport – White blood cells – defense– Platelets – clotting

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Red blood cells: Erythrocytes

• Most abundant blood cells (over 99%)

• Transport O2 and CO2

• Iron-based hemoglobin protein binds to O2 and transports from areas of high concentration to low concentration

Blood

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Erythrocytes are short-lived• Formed in bone marrow• Lack nuclei (cannot divide or make proteins)• Dead cells are removed by liver and spleen

– Iron is recycled, although some is excreted• Number of erythrocytes

maintained by negative feedback

Blood

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White blood cells: leukocytes

• Less than 1% of blood cells• Disease defense

– Consume foreign – particles – (macrophages)– Produce antibodies – (lymphocytes)

Blood

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Platelets

• Cellular fragments aid blood clotting

• Ruptured cells and platelets work together to produce substances that plug damaged vessels

• Scabs are platelets embedded in web of fibrin proteins

Blood

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Blood is carried in vessels

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Artery Vein

SEM100 µm

Endothelium

Artery

Smoothmuscle

Connectivetissue Capillary

Basal lamina

Endothelium

Smoothmuscle

Connectivetissue

Valve

Vein

Arteriole Venule

Red blood cell

Capillary

15 µ

mL

M

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Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Carry blood away from heart

• Thick-walled:

• Smooth muscle/elastic fibers

• Withstand high pressure

Arteries

Blood Vessels

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Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Control distribution of blood flow

• Smooth muscle expands / contracts

• Under hormone / NS control

Arterioles

Blood Vessels

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• Arterioles• Contract walls: redirects blood to heart and muscles when

needed (stress, exercise, cold)• Relax walls: brings more blood to skin capillaries to

dissipate excess heat• Precapillary sphincters control blood flow to capillaries

Blood Vessels

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Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Nutrients/waste exchanged with cells:

• Vessel wall one-cell thick

• Blood flow very slow

• Materials exit/enter via diffusion

Capillaries

Blood Vessels

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Heart

Arteries Arterioles

Capillaries

VenulesVeins

• Carry blood towards the heart

• Thin-walled; large diameter

• One-way to prevent backflow

Venules & Veins

Blood Vessels

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Skeletal Muscle Pump:

Vein Valve:

Blood Vessels

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Blood Vessels

Varicose veins occur if the vein valves become inefficient

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Cardiovascular Disorders:

• Leading cause of death in the United States

1) Hypertension = High blood pressure

• Resistance in vessels = work for heart

Blood Vessels

2) Atherosclerosis = Deposits (plaques) collect in vesselsConnectivetissue

Smoothmuscle Endothelium Plaque

(a) Normal artery (b) Partly clogged artery50 µm 250 µm

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If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation?

Thought Question:

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Living things process energy

• They need oxygen for this - Why?

Overview

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Respiratory systems enable gas exchange

• Bulk flow– Movement in bulk– Air/water to respiratory

surface– Blood through vessels

• Diffusion– Individual molecules move

down concentration gradients

– Gas exchange across respiratory surface

– Gas exchange in tissues

Gas Exchange Systems

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Gills• Aquatic gas exchange

Gas Exchange Systems

• Elaborately folded ( surface area)

• Contain capillary beds

• Gill size inversely related to [O2]

• Large gills = low [O2]

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Gas Exchange SystemsFish Efficiency

• Dissolved O2 is < 1% of water (21% of air)

• Countercurrent exchange increases efficiency

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Reptiles & Mammals use lungs exclusively

• Lack permeable skin• Lungs are more efficient

– Especially birds!

Gas Exchange Systems

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Human Respiration

• Air enters through nose and mouth to pharynx

• Travels through larynx (voice box)

• Epiglottis directs travel

Mammals

Pharynx

Larynx(Esophagus)

Trachea

Right lung

Bronchus

Bronchiole

Diaphragm

(Heart)

Leftlung

Nasalcavity

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On to the lungs

• Trachea • Bronchi • Bronchioles Alveoli

Human Respiration

Air is warmed & cleaned• Dust & bacteria trapped by mucus • Swept up and out by cilia

• provide enormous surface area

• Surfactant keeps surface moist

• Association with capillaries

– Diffusion of gasses Capillaries

Alveoli

Branch ofpulmonary artery

Branch ofpulmonary vein

Terminalbronchiole

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Human Respiration

• Gas exchange is driven by differences in pressures

• Blood from body with low O2, has a partial oxygen pressure (PO2) of ~40 mm Hg

• By contrast, the PO2 in the alveoli is about 100 mm Hg

• Blood leaving lungs, thus, normally contains a PO2 of ~100 mm

Exhaled air Inhaled air

Pulmonaryarteries

Systemicveins

Systemicarteries

Pulmonaryveins

Alveolarcapillaries

AlveolarspacesAlveolar

epithelialcells

Heart

SystemiccapillariesCO2 O2

Body tissue

CO2 O2

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2

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6 4

5

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CO2 Transport

• CO2 binds hemoglobin loosely

• Dissolved in plasma

• Combines with H20 to form bicarbonate (HCO3

-)

– More CO2 = lower pH

Transport of gasses

The Bohr Effect:

Hemoglobin binds more tightly to O2 when pH is increased and loosely when pH is decreased

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O2 Transport

• Binds to hemoglobin

– Removes O2 from plasma solution

– Increases concentration gradient; favors diffusion from air via alveoli

Transport of gasses

CO binds more tightly to hemoglobin than O2

Prevents O2 transport

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Breathing Mechanisms• Inhalation:

Rib muscles contract to expand rib cage

Diaphragm contracts (down) expands the volume of thorax and lungs

• Thoracic cavity expands, produces negative pressure which draws air into the lungs

Rib cageexpands.

Airinhaled.

Airexhaled.

Rib cage getssmaller.

1 2

Lung

Diaphragm

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Breathing is involuntary

• Controlled by respiratory center of the brain• Adjusts breath rate & volume based on

sensory input– Maintain a constant concentration of

CO2

Breathing Mechanisms Homeostasis:Blood pH of about 7.4

CO2 level

decreases. Stimulus:Rising level ofCO2 in tissues

lowers blood pH.Response:Rib musclesand diaphragmincrease rateand depth ofventilation.

Carotidarteries

AortaSensor/control center:Cerebrospinal fluid

Medullaoblongata

Things To Do After Lecture 11…Reading and Preparation:

1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms.

2. Ch. 42 Self-Quiz: #2, 3, 4, 6, 7 (correct answers in back of book)

3. Read chapter 42, focus on material covered in lecture (terms, concepts, and figures!)

4. Skim next lecture.

“HOMEWORK” (NOT COLLECTED – but things to think about for studying):

1. Compare and contrast veins and arteries in terms of structure and function.

2. Diagram the path blood takes from the body, to the heart and lungs, back to the body.

3. Explain in detail how oxygen is carried in the bloodstream and exchanged in the lungs and at cells, from drawing a breath to bulk flow in blood to diffusion at cells. What do cells use this oxygen for?

4. Explain homeostatic control of breathing.