1. 2 Lecture 11 Outline (Ch. 42) I. Circulatory Systems II.Human Heart III. Blood & Vessels...

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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

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

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

Hemolymph in sinusessurrounding organs

Interstitialfluid

Small branch vesselsIn each organ

Dorsal vessel(main heart)

Auxiliary hearts Ventral vessels

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

Tubular heart

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

Arteries – away from heart, Veins – toward heart

• 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)

Gillcapillaries

Bodycapillaries

Oxygen-rich blood

Oxygen-poor blood

Bony fishes, rays, sharks

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

Lungcapillaries

Pulmonary circuit

Oxygen-rich blood

Oxygen-poor blood

Amphibians, reptiles, mammals

Double circulation – pulmonary circuit and systemic circuit

4-chambered heart: A closer look

• 2 pumps• Right:

deoxygenated blood

• Left: oxygenated blood

Pulmonary artery

Rightatrium

Semilunarvalve

Atrioventricularvalve

Rightventricle

Leftventricle

Atrioventricularvalve

Semilunarvalve

Leftatrium

Pulmonaryartery

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

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

Oxygenated blood pumped to body through aorta

Pumps into left ventricle

Keeping blood moving• Heart valves maintain

one-way flow• Atrioventricular valves

– Between atria & ventricles

• Semilunar valves– Between ventricles &

arteries

The Cardiac Cycle

Atrial andventricular diastole

0.4sec

Atrial systole and ventricular diastole

0.1sec

Ventricular systole and atrialdiastole

0.3 sec

The Cardiac Cycle & Blood Pressure

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

Cardiac muscle contracts

• Present only in the heart

Cells linked by intercalated discs

Prevents strong contractions from tearing muscle

Allows rapid spread of electrical signal for

simultaneous regional

contraction

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)

Plasma • Primarily water• Dissolved proteins and electrolytes

Blood • Plasma fluid• Cells

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

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

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

White blood cells: leukocytes

• Less than 1% of blood cells• Disease defense

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

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 is carried in vessels

Artery Vein

SEM100 µm

Endothelium

Artery

Smoothmuscle

Connectivetissue Capillary

Basal lamina

Endothelium

Smoothmuscle

Connectivetissue

Arteriole Venule

Red blood cell

Capillary

Arteries Arterioles

Capillaries

VenulesVeins

• Carry blood away from heart

• Thick-walled:

• Smooth muscle/elastic fibers

• Withstand high pressure

Arteries

Blood Vessels

Arteries Arterioles

Capillaries

VenulesVeins

• Control distribution of blood flow

• Smooth muscle expands / contracts

• Under hormone / NS control

Arterioles

Blood Vessels

• 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

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

Arteries Arterioles

Capillaries

VenulesVeins

• Carry blood towards the heart

• Thin-walled; large diameter

• One-way to prevent backflow

Venules & Veins

Blood Vessels

Skeletal Muscle Pump:

Vein Valve:

Blood Vessels

Varicose veins occur if the vein valves become inefficient

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

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

Thought Question:

Living things process energy

• They need oxygen for this - Why?

Overview

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

Gills• Aquatic gas exchange

• Elaborately folded ( surface area)

• Contain capillary beds

• Gill size inversely related to [O2]

• Large gills = low [O2]

Gas Exchange SystemsFish Efficiency

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

• Countercurrent exchange increases efficiency

Reptiles & Mammals use lungs exclusively

• Lack permeable skin• Lungs are more efficient

– Especially birds!

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

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

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

SystemiccapillariesCO2 O2

Body tissue

CO2 O2

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

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

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.

Diaphragm

Breathing is involuntary

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

sensory input– Maintain a constant concentration of

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.

1. 2 Lecture 11 Outline (Ch. 42) I. Circulatory Systems II.Human Heart III. Blood & Vessels...

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