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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
Left coronary artery
supplies interventricular septum, anterior ventricular walls, left atrium, and posterior wall of left ventricle; has two branches: - Anterior interventricular artery - Circumflex artery
26
Right coronary artery
supplies right atrium and most of right ventricle; has two branches: Right marginal artery Posterior interventricular artery
27
Coronary veins Cardiac veins collect blood from Coronary sinus empties into formed by merging
- 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
Angina pectoris
Thoracic pain caused by fleeting deficiency in blood delivery to myocardium Cells are weakened
29
Myocardial infarction Prolonged Areas of cell death repaired with
(heart attack) - Prolonged coronary blockage - Areas of cell death are repaired with noncontractile scar tissue
30
Microscopic Anatomy | Cardiac muscle cells
- 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
Microscopic Anatomy | Intercalated discs
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
How Does the Physiology of Skeletal and Cardiac Muscle Differ? Similarities with skeletal muscle
- 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
Differences between cardiac and skeletal muscle
- 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
functional syncytium
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
Tetanic contractions
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
The heart relies almost exclusively on _____ respiration
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
18.5 Electrical Events of the Heart
Heart depolarizes and contracts without nervous system stimulation, although rhythm can be altered by autonomic nervous system ---Sympathetic and parasympathetic
38
Coordinated heartbeat is a function of:
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
Action potential initiation by pacemaker cells
- 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
Sequence of excitation
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
1. Sinoatrial (SA) node
- 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
2.Atrioventricular (AV) node
- 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 SA node input
43
3.Atrioventricular (AV) bundle (bundle of His)
- In superior interventricular septum - Only electrical connection between atria and ventricles - -Atria and ventricles not connected via gap junctions
44
4.Right and left bundle branches
Two pathways in interventricular septum | Carry impulses toward apex of heart
45
Defects in intrinsic conduction system may cause: - arrhythmias - fibrillation
-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
To reach ventricles, impulse must pass through AV node | If AV node is defective, may cause 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
Heartbeat modified by ANS via cardiac centers in medulla oblongata Cardioacceleratory center Cardioinhibitory center:
-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
Electrocardiograph
can detect electrical currents generated by heart
49
Electrocardiogram
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
``` main features p wave qrs complex t wave p-r wave s-t segment q-t interval ```
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
enlarged r waves elevated or depressed S-T waves prolonged q-t interval
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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