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A+P 2 > chp 18 > Flashcards

chp 18 Flashcards

1
Q

The Pulmonary and Systemic Circuits

two side-by-side pumps

A

Pulmonary circuit (right side)
- receives oxygen-poor blood from tissues
Pumps blood to lungs to get rid of CO2, pick up O2

Systemic Circuit (left side)

  • receives oxygenated blood from lungs
  • Pumps blood to body tissues
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2
Q

Receiving chambers of heart

A

-Right atrium
Receives blood returning from systemic circuit

-Left atrium
Receives blood returning from pulmonary circuit

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3
Q

Pumping chambers of heart

A

-Right ventricle
Pumps blood through pulmonary circuit

-Left ventricle
Pumps blood through systemic circuit

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4
Q

Size, Location, and Orientation of Heart

A

Approximately the size of a fist
Weighs less than 1 pound

Location
-In mediastinum between second rib and fifth intercostal space
-Above diaphragm
-Two-thirds of heart to left of midsternal line
Anterior to vertebral column, posterior to sternum

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5
Q

base, apex, apical impulse

A
  • Base (posterior surface) leans toward right shoulder
  • Apex points toward left hip
  • Apical impulse palpated between fifth and sixth ribs, just below left nipple
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6
Q

Coverings of the Heart

A
  • Pericardium: double-walled sac that surrounds heart; made up of two layers
  • Superficial fibrous pericardium: functions to protect, anchor heart to surrounding structures, and prevent overfilling

-Deep two-layered serous pericardium
–Parietal layer lines internal surface of fibrous pericardium
–Visceral layer (epicardium) on external surface of heart
Two layers separated by fluid-filled pericardial cavity
Why fluid?

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7
Q

Pericarditis

Cardiac tamponade

A
  • Inflammation of pericardium
  • Roughens membrane surfaces, causing pericardial friction rub (creaking sound) heard with stethoscope
  • Cardiac tamponade
  • -Excess fluid that leaks into pericardial space
  • -Can compress heart’s pumping ability
  • -Treatment: fluid is drawn out of cavity (usually with syringe)
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8
Q

Three layers of heart wall

A

​​-Epicardium: visceral layer of serous pericardium
-​​Myocardium: circular or spiral bundles of contractile cardiac muscle cells
​​-Endocardium: innermost layer; is continuous with endothelial lining of blood vessels
Lines heart chambers and covers cardiac skeleton of valves

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9
Q

Chambers and Associated Great Vessels
Internal features
Four chambers

A

Two superior atria

Two inferior ventricles

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10
Q

Interatrial septum:

Fossa ovalis

A

separates atria

remnant of foramen ovale of fetal heart

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11
Q

Interventricular septum:

A

separates ventricles

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12
Q

Surface features

  • coronary sulcus
  • Anterior interventricular sulcus
  • Posterior interventricular sulcus
A

(atrioventricular groove)
Encircles junction of atria and ventricles

Anterior position of interventricular septum

Landmark on posteroinferior surface

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13
Q

Atria: the chambers

  • auricles
  • right atrium
  • posterior portion contains
  • posterier and anterior separated by
A

receiving
-Small, thin-walled chambers; contribute little to propulsion of blood
-Auricles: appendages that increase atrial volume
Right atrium: receives deoxygenated blood from body
Anterior portion is smooth-walled
Posterior portion contains ridges formed by pectinate muscles
Posterior and anterior regions are separated by crista terminalis

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14
Q

Three veins empty into right atrium:

A
  • Superior vena cava: returns blood from body regions above the diaphragm
  • Inferior vena cava: returns blood from body regions below the diaphragm
  • Coronary sinus: returns blood from coronary veins
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15
Q

Left atrium

  • pectinate muscles found
  • ____ pulmonary viens
A

-pectinate muscles found only in auricles
receives oxygenated blood from lungs
-Four pulmonary veins return blood from lungs

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16
Q 
Ventricles: 
right
left where are they found
-trabeculae carnea
-paillary muscles
A

the discharging chambers

Make up most of the volume of heart

  • Right ventricle: most of anterior surface
  • Left ventricle: posteroinferior surface
  • Trabeculae carneae: irregular ridges of muscle on ventricular walls
  • Papillary muscles: project into ventricular cavity
  • -Anchor chordae tendineae that are attached to heart valves
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17
Q 
Ventricles:
\_\_\_\_ walls than atria
\_\_\_\_ pumps of heart
right ventricle pumps blood into?
left ventricle pumps blood into?
A

Thicker walls than atria
Actual pumps of heart

-Right ventricle
Pumps blood into pulmonary trunk
Left ventricle
Pumps blood into aorta (largest artery in body)

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18
Q

Heart Valves

  • ensure
  • two major types
  • open and close when
  • location of valves
A

-Ensure unidirectional blood flow through heart
-Open and close in response to pressure changes
-Two major types of valves
Atrioventricular valves located between atria and ventricles
Semilunar valves located between ventricles and major arteries

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19
Q

No valves are found between

A

major veins and atria; not a problem because:

Inertia of incoming blood prevents backflow
Heart contractions compress venous openings

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20
Q

Two atrioventricular (AV) valves prevent backflow into atria when ventricles contract

Chordae tendineae: anchor

A
  • Tricuspid valve (right AV valve): made up of three cusps and lies between right atria and ventricle
  • Mitral valve (left AV valve, bicuspid valve): made up of two cusps and lies between left atria and ventricle

cusps of AV valves to papillary muscles that function to:

Hold valve flaps in closed position
Prevent flaps from everting back into atria

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21
Q

Two conditions severely weaken heart:
Incompetant valve
Valvular stenosis

A

-Incompetent valve
Blood backflows so heart repumps same blood over and over

-Valvular stenosis
Stiff flaps that constrict opening
Heart needs to exert more force to pump blood

Defective valve can be replaced with mechanical, animal, or cadaver valve

22
Q

volumes of blood are pumped to pulmonary and systemic circuits

Pulmonary circuit is___, ____-pressure circulation

Systemic circuit is___,
___-friction circulation

Anatomy of ventricles reflects differences

A

Equal volumes of blood are pumped to pulmonary and systemic circuits

Pulmonary circuit is short, low-pressure circulation

Systemic circuit is long, high-friction circulation

Left ventricle walls are 3× thicker than right
Pumps with greater pressure

23
Q

Coronary circulation
delivered when
___ circulation in body
____ventricle receives ___

A

-Functional blood supply to heart muscle itself
-Shortest circulation in body
-Delivered when heart is relaxed
Left ventricle receives most of coronary blood supply
WHY?-biggest

24
Q

Coronary arteries
heart receives ___ of blood supply

Both left and right coronary arteries arise from

Both _____ heart in coronary sulcus

Arteries contain many

A
  • Both left and right coronary arteries arise from base of aorta and supply arterial blood to heart
  • Both encircle heart in coronary sulcus
  • Branching of coronary arteries varies among individuals
  • Arteries contain many anastomoses (junctions)
  • -Provide additional routes for blood delivery
  • -Cannot compensate for coronary artery occlusion
  • Heart receives 1/20th of body’s blood supply
25
Q

Left coronary artery

A

supplies interventricular septum, anterior ventricular walls, left atrium, and posterior wall of left ventricle; has two branches:

  • Anterior interventricular artery
  • Circumflex artery
26
Q

Right coronary artery

A

supplies right atrium and most of right ventricle; has two branches:
Right marginal artery
Posterior interventricular artery

27
Q

Coronary veins

Cardiac veins collect blood from

Coronary sinus empties into

formed by merging

A
  • Cardiac veins collect blood from capillary beds
  • Coronary sinus empties into right atrium; formed by merging cardiac veins
  • -Great cardiac vein of anterior interventricular sulcus
  • -Middle cardiac vein in posterior interventricular sulcus
  • -Small cardiac vein from inferior margin

-Several anterior cardiac veins empty directly into right atrium anteriorly

28
Q

Angina pectoris

A

Thoracic pain caused by fleeting deficiency in blood delivery to myocardium
Cells are weakened

29
Q

Myocardial infarction
Prolonged
Areas of cell death repaired with

A

(heart attack)

  • Prolonged coronary blockage
  • Areas of cell death are repaired with noncontractile scar tissue
30
Q

Microscopic Anatomy

Cardiac muscle cells

A
  • striated, short, branched, fat, interconnected
  • One central nucleus (at most, 2 nuclei)
  • Contain numerous large mitochondria (25–35% of cell volume)
  • Sarcomeres
  • Z discs, A bands, and I bands all present
  • T tubules are wider, but less numerous
  • -Enter cell only once at Z disc

-SR simpler than in skeletal muscle; no triads

31
Q

Microscopic Anatomy

Intercalated discs

A

are connecting junctions between cardiac cells that contain:

  • Desmosomes: hold cells together; prevent cells from separating during contraction
  • Gap junctions: allow ions to pass from cell to cell; electrically couple adjacent cells
  • -Allows heart to be a functional syncytium, a single coordinated unit
32
Q

How Does the Physiology of Skeletal and Cardiac Muscle Differ? Similarities with skeletal muscle

A
  • Muscle contraction is preceded by depolarizing action potential
  • Depolarization wave travels down T tubules; causes sarcoplasmic reticulum (SR) to release
  • Excitation-contraction coupling occurs
  • – binds troponin causing filaments to slide
33
Q

Differences between cardiac and skeletal muscle

A
  • Some cardiac muscle cells are self-excitable
  • -Two kinds of myocytes
  • Contractile cells: responsible for contraction
  • Pacemaker cells: noncontractile cells that spontaneously depolarize
  • —Initiate depolarization of entire heart
  • —-Do not need nervous system stimulation, in contrast to skeletal muscle fibers
34
Q

functional syncytium

A

Heart contracts as a unit
Contraction of all cardiac myocytes ensures effective pumping action
–Skeletal muscles contract independently

Influx of calcium from extracellular fluids triggers CA release from SR

-Depolarization opens slow CA channels in sarcolemma, allowing CA to enter cell

  • exracellular CA then causes SR to release its intracellular CA
  • skeletal muscles do not use extracellular CA
35
Q

Tetanic contractions

A

cannot occur in cardiac muscles

  • Cardiac muscle fibers have longer absolute refractory period than skeletal muscle fibers
  • –Absolute refractory period is almost as long as contraction itself
  • —Prevents tetanic contractions
  • —Allows heart to relax and fill as needed to be an efficient pump
36
Q

The heart relies almost exclusively on _____ respiration

A

aerobic respiration

  • Cardiac muscle has more mitochondria than skeletal muscle so has greater dependence on oxygen
  • —Cannot function without oxygen

-Skeletal muscle can go through fermentation when oxygen not present
-Both types of tissues can use other fuel sources
Cardiac is more adaptable to other fuels, including lactic acid, but must have oxygen

37
Q

18.5 Electrical Events of the Heart

A

Heart depolarizes and contracts without nervous system stimulation, although rhythm can be altered by autonomic nervous system
—Sympathetic and parasympathetic

38
Q

Coordinated heartbeat is a function of:

A
  1. Presence of gap junctions
  2. Intrinsic cardiac conduction system
    - Network of noncontractile (autorhythmic) cells
    - Initiate and distribute impulses to coordinate depolarization and contraction of heart
39
Q

Action potential initiation by pacemaker cells

A
  • Cardiac pacemaker cells have unstable resting membrane potentials called pacemaker potentials or prepotentials
  • Three parts of action potential

1.​​Pacemaker potential:
K+ channels are close, but slow na+ channels are open, curing interior to become more positive
2.Depolarization Ca channels open allowing huge influx of Ca leading to rising phase of action potential
3. Depolarization K+ channels open, allowing efflux of K+ and cell becomes more negative

40
Q

Sequence of excitation

A

Cardiac pacemaker cells pass impulses, in following order, across heart in ~0.22 seconds
Sinoatrial node →
​​Atrioventricular node →
​​Atrioventricular bundle →
​​Right and left bundle branches →
​​Subendocardial conducting network (Purkinje fibers)

41
Q
  1. Sinoatrial (SA) node
A
  • Pacemaker of heart in right atrial wall
  • -Depolarizes faster than rest of myocardium
  • Generates impulses about 75×/minute (sinus rhythm)
  • -Inherent rate of 100×/minute tempered by extrinsic factors
  • Impulse spreads across atria, and to AV node
42
Q

2.Atrioventricular (AV) node

A
  • In inferior interatrial septum
  • Delays impulses approximately 0.1 second
  • –Because fibers are smaller in diameter, have fewer gap junctions
  • –Allows atrial contraction prior to ventricular contraction
  • Inherent rate of 50×/minute in absence of SAnode input
43
Q

3.Atrioventricular (AV) bundle (bundle of His)

A
  • In superior interventricular septum
  • Only electrical connection between atria and ventricles
  • -Atria and ventricles not connected via gap junctions
44
Q

4.Right and left bundle branches

A

Two pathways in interventricular septum

Carry impulses toward apex of heart

45
Q

Defects in intrinsic conduction system may cause:

  • arrhythmias
  • fibrillation
A

-Arrhythmias: irregular heart rhythms
Uncoordinated atrial and ventricular contractions

-Fibrillation: rapid, irregular contractions
Heart becomes useless for pumping blood, causing circulation to cease; may result in brain death
Treatment: defibrillation interrupts chaotic twitching, giving heart “clean slate” to start regular, normal depolarizations

46
Q

To reach ventricles, impulse must pass through AV node

If AV node is defective, may cause a

A

heart block

-Few impulses (partial block) or no impulses (total block) reach ventricles
-Ventricles beat at their own intrinsic rate
Too slow to maintain adequate circulation
-Treatment: artificial pacemaker, which recouples atria and ventricles

47
Q

Heartbeat modified by ANS via cardiac centers in medulla oblongata
Cardioacceleratory center
Cardioinhibitory center:

A

-Cardioacceleratory center: sends signals through sympathetic trunk to increase both rate and force
Stimulates SA and AV nodes, heart muscle, and coronary arteries
-Cardioinhibitory center: parasympathetic signals via vagus nerve to decrease rate
Inhibits SA and AV nodes via vagus nerves

48
Q

Electrocardiograph

A

can detect electrical currents generated by heart

49
Q

Electrocardiogram

A

ECG or EKG) is a graphic recording of electrical activity
-Composite of all action potentials at given time; not a tracing of a single AP
-Electrodes are placed at various points on body to measure voltage differences
12 lead ECG is most typical

50
Q 
main features
p wave
qrs complex
t wave
p-r wave
s-t segment
q-t interval
A

Main features:
P wave: depolarization of SA node and atria
QRS complex: ventricular depolarization and atrial repolarization
T wave: ventricular repolarization
P-R interval: beginning of atrial excitation to beginning of ventricular excitation
S-T segment: entire ventricular myocardium depolarized
Q-T interval: beginning of ventricular depolarization through ventricular repolarization

51
Q

enlarged r waves
elevated or depressed S-T waves
prolonged q-t interval

A

Enlarged R waves may indicate enlarged ventricles
Elevated or depressed S-T segment indicates cardiac ischemia

Prolonged Q-T interval reveals a repolarization abnormality that increases risk of ventricular arrhythmias
Junctional blocks, blocks, flutters, and fibrillations are also detected on ECG

A+P 2 (13 decks)

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