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Figure 17.17 An electrocardiogram (ECG) tracing.

Sinoatrialnode

Atrioventricularnode

QRS complex

Ventriculardepolarization

Atrialdepolarization

Ventricularrepolarization

P-RInterval

S-TSegment

Q-TInterval

0 0.2 0.4 0.6 0.8Time (s)

R

Q

S

P T

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Figure 18.6 Blood pressure in various blood vessels of the systemic circulation.

Systolic pressure

Mean pressure

Diastolicpressure

120

100

80

60

40

20

0

Aorta

Arte

ries

Arte

riole

s

Capi

llarie

s

Venu

les

Vein

s

Vena

e ca

vae

Blo

od p

ress

ure

(m

m H

g)

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Figure 18.5 Relative proportion of blood volume throughout the cardiovascular system.

Pulmonary bloodvessels 12%

Systemic arteriesand arterioles 15% Heart 8%

Capillaries 5%

Systemic veinsand venules 60%

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Figure 18.7 The muscular pump.

Venous valve (open)

Contracted skeletalmuscle

Venous valve(closed)

Vein

Direction of blood flow

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Figure 18.9 Baroreceptor reflexes that help maintain blood pressure homeostasis. (1 of 2)

Baroreceptors in carotid sinuses and aortic arch are stimulated.

Stimulus: Blood pressure (arterial blood pres- sure rises above normal range). Homeostasis: Blood pressure in normal range

CO and R return blood pressure to homeostatic range.

Sympathetic impulses to heartcause HR,

Impulses from baroreceptors stimulate cardioinhibitory center (and inhibit cardioacceleratory center) and inhibit vasomotor center.

Rate of vasomotor impulses allows vasodilation, causing R.

IMBALANCE

3

2

1

4b

5

4a

contractility, and CO.

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The vagus nerve(parasympathetic)decreases heart rate.

Dorsal motor nucleusof vagus

Cardioinhibitorycenter

Cardioaccele-ratory center Medulla oblongata

Sympathetictrunkganglion

Thoracic spinal cordSympathetic trunk

Sympathetic cardiacnerves increase heart rateand force of contraction.

AVnode

SAnode

Parasympathetic fibers Sympathetic fibers Interneurons

Figure 17.16 Autonomic innervation of the heart.

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Figure 17.23 Norepinephrine increases heart contractility via a cyclic AMP secondmessenger system.

a

b c

Norepinephrine

β1-Adrenergicreceptor G protein (Gs)

Adenylate cyclase

GDP

ATP is convertedto cAMP

Ca2+Extracellular fluid

Ca2+

channel

Cytoplasm

Phosphorylates plasmamembrane Ca2+

channels, increasingextracellular Ca2+ entry

Phosphorylates SR Ca2+ pumps, speedingCa2+ removal and relaxation, making moreCa2+ available for release on the next beat

Active proteinkinase

Ca2+

Ca2+ uptake pump

Sarcoplasmicreticulum (SR)

Inactive proteinkinase

Phosphorylates SR Ca2+ channels, increasingintracellular Ca2+ release

Ca2+binds

toTroponin

Enhancedactin-myosininteraction

SR Ca2+

channel Cardiac muscle

force and velocity

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Table 18.2 Effects of Selected Hormones on Blood Pressure

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Figure 18.18 Events and signs of hypovolemic shock.

Acute bleeding (or other events that reduceblood volume) leads to:

1. Inadequate tissue perfusion resulting in O2 and nutrients to cells

2. Anaerobic metabolism by cells, so lactic acid accumulates

3. Movement of interstitial fluid into blood, so tissues dehydrate

Initial stimulus

Physiological response

Signs and symptoms

Result

Chemoreceptors activated(by in blood pH)

Baroreceptor firing reduced(by blood volume and pressure)

Hypothalamus activated(by blood pressure)

Respiratory centersactivated

Cardioacceleratory and vasomotor centers activated

Sympathetic nervoussystem activated

ADHreleased

Neuronsdepressed

by pH

Centralnervous system

depressed

Heart rateIntense vasoconstriction

(only heart and brain spared)

Renal blood flow

Renin released

Angiotensin IIproduced in blood

Aldosteronereleased

Kidneys retainsalt and water

Waterretention

Rate anddepth ofbreathing

Tachycardia;weak, thready

pulse

Skin becomescold, clammy,and cyanotic

Urine output Thirst Restlessness(early sign)

Coma(late sign)

CO2 blownoff; bloodpH rises

Blood pressure maintained;if fluid volume continues to

decrease, BP ultimatelydrops. BP is a late sign.

Major effect Minor effect

Adrenalcortex

Kidneys

Brain

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Figure 18.12 Body sites where the pulse is most easily palpated.

Superficial temporal artery

Facial artery

Common carotid artery

Brachial artery

Radial artery

Femoral artery

Popliteal artery

Posterior tibialartery

Dorsalis pedisartery

Drug Classifications >> Hypertension >> Variable they Affect

Reduce Stroke VolumeDiureticsAldosterone receptor blockersAngiotensin (ACE) inhibitorsAngiotensin II receptor blockersVenodilators

Reduce Systemic Vascular Resistanceα1 blockersCalcium channel blockersDirect-acting arterial dilators

Decrease Heart Rateβ blockers

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Figure 18.13 Distribution of blood flow at rest and during strenuous exercise.

Brain

Heart

Skeletalmuscles

Skin

Kidneys

Abdomen

Other

750

250

1200

500

1100

1400

600

750

750

12,500

1900

600

600

400

Total bloodflow at rest5800 ml/min

Total blood flow duringstrenuous exercise17,500 ml/min

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Figure 18.17 Bulk fluid flow across capillary walls causes continuous mixing of fluid between the plasma and the interstitial fluid compartments, and maintains the interstitial environment. (2 of 5)

The big pictureFluid filters from capillaries at their arteriolar end and flows through the interstitial space. Most is reabsorbed at the venous end.

For all capillary beds, 20 L of fluid is filteredout per day—almost7times the total plasmavolume!

17 L of fluid per day is reabsorbedinto the capillariesat the venous end.

LymphaticcapillaryVenule

About 3 L per day of fluid (and anyleaked proteins) areremoved by thelymphatic system(see Chapter 20).

Arteriole

Fluid moves through the interstitial space.

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Figure 18.16 Capillary transport mechanisms. (2 of 2)

Pinocytoticvesicles

Caveolae

Intercellularcleft

Transportvia vesiclesor caveolae(largesubstances)

Movementthroughfenestrations (water-solublesubstances)

Basementmembrane

Movementthroughintercellularclefts (water-solublesubstances)

Diffusionthroughmembrane(lipid-solublesubstances)

Endothelialfenestration(pore)

Lumen

12

3

4

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Figure 19.1a Distribution and special features of lymphatic capillaries.

Venous system Arterial systemHeart

Lymphatic system:Lymph duct

Lymph node

Collectinglymphaticvessels, withvalves

Bloodcapillaries

Lymphaticcapillary

Tissuefluid

Tissue cell Bloodcapillaries

Lymphaticcapillaries

Lymph trunk

Structural relationship between a capillary bed of the blood vascular system and lymphatic capillaries.

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Figure 19.1b Distribution and special features of lymphatic capillaries.

Filaments anchoredto connective tissue

Endothelial cell

Flaplike minivalve

Fibroblast in looseconnective tissue

Lymphatic capillaries are blind-ended tubes in whichadjacent endothelial cells overlap each other, forming flaplike minivalves.

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Figure 19.2a The lymphatic system.

Internaljugular vein

Entrance ofright lymphaticduct into vein

Entrance of thoracic ductinto veinThoracicduct

Cisternachyli

Collectinglymphaticvessels

Regionallymph nodes:

Cervicalnodes

Axillarynodes

Inguinalnodes

Aorta

Drained by the right lymphatic ductDrained by the thoracic duct

General distribution of collecting lymphaticvessels and regional lymph nodes.

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Figure 19.4a Lymph node.

Afferentlymphaticvessels

Cortex• Lymphoid follicle• Germinal center• Subcapsular sinus

Efferentlymphaticvessels

Trabeculae

• Medullary sinus

• Medullary cord

MedullaHilum

Longitudinal view of the internal structure of a lymphnode and associated lymphatics

Capsule

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Macrophage

Reticular cells onreticular fibers

Lymphocytes

Medullary sinus

Reticular fiber

Figure 19.3 Reticular connective tissue in a human lymph node.

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Diaphragm

Spleen

Adrenalgland

Leftkidney

Splenicartery

Pancreas

Photograph of the spleen in its normal position inthe abdominal cavity, anterior view.

Figure 19.6c The spleen.

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Figure 19.5 Lymphoid organs.

Tonsils (in pharyngealregion)

Thymus (in thorax; most active during youth)

Spleen (curves around left side of stomach)

Peyer’s patches (aggregated lymphoidnodules in smallintestine)

Appendix