A&P Lecture Unit 3: Blood Circulation and Cardio

Cardiopulmonary disease

#1 cause of death in US: heart disease.

Heart location

Middle of mediastinum

Pericaridum

• Fibrous layer

• Parietal layer

• Space/cavity

• Visceral layer (epicardium)

• Myocardium (heart muscle)

• Endocardium (inner layer, wall of heart chamber)

All Patients Take Meds

Aortic: 2nd intercostal

Pulmonic: 2nd intercostal

Tricuspid: 4th intercostal

Mitral: 5th Intercoastal

Erb’s point

3r intercostal space, left sternal border (good for listening to entire heart)

Which valuve is most gets most damaged most often?

Mitral valve because it must pump to the whole body and needs to use the most force. Sometimes valves open again before ventricles can fully drain

Coronary Circulation

• RCA: supplies r atrium, r ventricle, inferior wall L ventricle

• LAD: anterior wall L ventricle

• LCX: L atrium, lat and post walls of L ventricle

One cardiac cycle

• Beginning of contraction to beginning of next contraction

  Divided into..

• Systole

• Diastole

  • Atrial syatole or diastole

  • Ventricular systole or diastole

Atria during Systole

At rest: Atria contract and push the final 25-30% of blood from atrium to ventricle (atrial kick)

During Exercise: Atria assume a greater role b/c blood must be pushed to the ventricles more quickly

• Therefore, problems with atrial function may emerge during increased exercise

Right ventricle

• Only needs to pump blood to lungs

• Resistance in pulmonary artery fairly low (15mmHg)

• Low pressure/force

Left Ventricle

• Must pump blood to entire body

• Resistance in aorta fairly high (~100mmHg)

• High pressure/force, major work of the heart

End diastolic volume

Ventricles are relativey full (110-120 ml per ventricle)

End-systolic volume

Ventricles have just finished contracting & are relatively empty (40-50 ml)

Stroke Volume

How much blood was pumped out during systole

SV = EDV-ESV

SX = approx. 70 ml

Ejection fraction

EF = (SV/EDV) x 100

EX:

• End diastolic volume =115

• Stroke volume = 70

• Ejection fraction = 70/115 = .61 = 61%

  • Normal Ejection fraction ~60%

Ejection fraction levels

High: +70%

Normal: 46-70%

Low: 35-45%

Risk: -35%

Cardiac Output

Amount of blood pumped per min

• Amount leaving either left or right ventricle

Determinants of CO

CO = stroke volume x heart rate

• EX: SV = 70 ml/beat and HR = 72 beats/min

• CO = 70 ml/beat x 72 beats/min = 5040 ml/min or 5,04 liter/min

• Trained heart usually has. lower HR but higher SV

Sympathetic effects on heart

Innervation: SNS neuron innervate entire heart and release norepinerine

Effects:

• ^ HR (positive chronotropic effect)

• ^ Contraction force (Positive inotropic effect)

• ^ Rate of AP conduction (positive dromotropic effect)

Parasympathetic effects on heart

Innervation: Cranial nerve X (vagus) innervates atira and releases acetylcholine

• No effect on contraction force bc ventricle no innervated

Circulating catecholamines

Epinephrine and norepinephrine

• Released from adrenal gland

• Released from adrenal gland

• Powerful cardiac stimulants

Cardiac “preload”

• Volume of blood returning to heart

• ^ blood return stretches ventricles causes increased SV and CO

Cardiac “afterload”

The forced heart must pump against

• ^ after causes v CO

Ionic imbalances

^Plasma potassium: slows HR

^Plasma Calcium: Increases HR

Temperature

^Body temp: increase HR

v Body temp: decreases HR

Systolic value (higher number)

Pressure when the heart contracts

• Tells us what the heart is doing

• S1: lub

• Ventricles contracts

• Open Semilunar valves

• Blood goes to the body

Diastolic value (lower number)

pressure when the heart relaxes

• Tells just what the arteries are doing

• S2: dub

• Ventricles relax

• Open AV valves

• blood to venrticles

Mean (average) BP

Algebraic (weighted) mean of systolic and diastolic values

Mean arterial pressure (MAP) = (2x diastolic +systolic) /3

• Normal MAP ~93.3mmHg

Blood Pressure

BP is a product of..

• Cardiac Output

• Total peripheral resistance (TPR): The sum of all the resistance in the arterial system

  • BP = CO x TPR
    BP = (SV x HR) x TPR

Baroreceptor Reflex

Rapid control of BP (2-3 seconds)

1. Pressure receptors (baroreceptors) located in large arteries; detect sudden changes in arterial pressure

2. Baroreceptors send info to CV control center in brainstem (medulla) if BP high or low

3. CV control alters actives of heart and circulation to bring BP back to normal $

Relatively rapid control of BP (1-2 minutes)

1. Adrenal Catecholamine: Epinephrine, norepinephrine released from adrenal gland if BP is too low

2. Renin-angiotensin system: Renin, enzyme from kidneys and Angiotensin, substance in bloodstream controlled by renin

Slow, long-term control of BP (days and weeks)

• Kidney

• Regulate balance of water and electrolytes (Na+, K+)

• If BP is too high → Release fliud from vascular system

• If BP is too low → retain fluid in body

Orthostatic hypotension

Stand suddenly and blood rushes to feet and stays there.

• SBP >20 mmHg

• DBP > 10 mmHg

Predisposing factors

• CV disease, meds, elderly, systemic disease/infections, many others

BP Response During Exercise

Normal:

• SBP ^ as exercise intensity ^ (^ CO)

• DBP unchanged or slight v

Abnormal Response:

• SBP unchanged or v as ex: intensity ^

• DBP ^ excessively as ex. intensity ^

Resting BP in exercise

Resting BP: SBP > 200 or DBP> 110

Terminate Exercise: SBP > 250 or DBP > 115

P-wave

Atrial depolarization

• 0.08 to 0.11 sec

QRS Complex

Ventricular Depolarization and Contracting, sending blood out of the heart

• <.10 sec

PR segment

0.12 to 0.20 secs

ST Segment

<0.12 sec

T- wave

Ventricle repolarize

< 0.20

QT Interval

<.10sec

Type A

Very common; approximately 41% of US population has this type A

• “Contains Type A antigens

• Contains Anti- B antibodies

Type B

Contains type B anitgens

• Plasma contains anti-A anibodies

Type AB

Contains both A and B antigens

• Contains no antibodies in plasma

Type O

Contain no A or B antigens

• Contains both A and B antibodies

Blood clotting

1. Vasuclar spasm: Allows time for next step to occur

   • When inner wall of vessel is damaged, collagen fiber is exposed

2. Platelet Plug formation: Loosely knit plug

   • Platelets in blood attach to damaged site

   • Attached platelet plug released chemicals that draw more platelets

3. Coagulation

   • Platelets secrete serotonin, causing blood vessels to spasm decreasing blood flow to the area

   • In 15 secs, blood clotting beings

   • Prothrombin (made by liver with vita. K)→ thrombin → fibrinogen → fibrin

   • Fibrin forms a net to catch more blood cells and platelets, within 3-6 mins, a clot is created

Cardiac Control

1. Sinoatrial node: Sets pace for the whole heart at around 70 bpm

2. AV Node: Delays impulse from SA nodes by about 0.1 second.

   a. Allows completion of atrial contraction prior to ventricular contraction

3. AV bundle: only electrical connection from atria to ventricles

4. AV bundle splits into right and left branches

5. Purkinje Fibers: completes the pathway

Circulation

Artery → Arteriole → Capillary → Venule → Vein

Tunica Intima

• Made up of endothelium

• Minimizes friction

Tunica media

Smooth muscle’

Vasoconstriction: decreases in diameter

Vasodilation: increased in diameter

Tunica Externa

Loosely woven collage fibers

• Contains vasa vasorum

Venous Blood Flow

• Openh venous valve

• Contracted skeletal muscle

• Closed venous valve

• Vein

• Direction of blood flow

Anastomosis

ACA

Supplies the medial and superior parts of frontal love and anterior parietal love

MCA

Blood to lateral (side)area of the frontal , temporal, and parietal lobes

PCA

Blood to occipital love, inferior temporal love, deep structures like thalamus and posterior limb of internal capsule.