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The Heart Option D.4 U: The Heart Option D.4 U:

The Heart Option D.4 U: - PowerPoint Presentation

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The Heart Option D.4 U: - PPT Presentation

Structure of Cardiac muscle cells allows propagation of stimuli through the heart wall Comparison to skeletal muscle Similarities striated long fibers Differences Shorter amp wider Yshaped cells ID: 785092

blood heart node amp heart blood amp node ventricles cardiac cells valves delay contract contraction systole muscle pressure wave

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Presentation Transcript

Slide1

The Heart

Option D.4

Slide2

U:

Structure of Cardiac muscle cells allows propagation of stimuli through the heart wall

Comparison to skeletal muscle:

Similarities

: striated, long fibersDifferences: Shorter & widerY-shaped cellsone nucleus per cellIntercalated discs = junction between cellsUnder INvoluntary control

Slide3

Cardiac cells contract as if one large cell

Y-shaped cells

and

Intercalated discs

allow physical connectionGap junctions allow electrical connection – (channels of connected cytoplasm between cells)Both allow rapid movement of ions & a wave of depolarization to pass easily from cell to cellBoth allow synchronization of muscle contractionNetwork of cells contract as if it was 1 large cell

Slide4

Identify…

Cardiac muscle fibers

Orange

&

blueMitochondriaRedOne sarcomereBetween narrow dark blue linesIntercalated discWavy dark blue line

Slide5

U: S

ignals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles

Cardiac cycle

= one complete heart beat

Systole = contraction of heartDiastole = relaxation of heart/filling of blood

Slide6

Cardiac Cycle animation

Slide7

The Pacemaker

SA node

= sinoatrial node = “pacemaker”

Collection of cells that spontaneously initiate action potentials without stimulation by other nerves

Gap junctions allow electric charges to flow freely between cells, so spreads rapidly across atriumSA node AV node  AV Bundle  Purkinje fibers

(NOTE

: AV bundle a.k.a. Bundle of

His)

Slide8

SA node

 AV node AV bundle  Purkinje fibers

Slide9

Pressure changes inside heart

Slide10

U: There is a delay between the arrival and passing on of a stimulus at the atrioventricular node.

Delay of ~0.12 s

Features of AV node that cause delay

:

Smaller fibersFewer Na+ channelsFewer gap junctionsMore non-conductive connective tissue

Slide11

U: This delay allows time for atrial systole before the atrioventricular valves close

Delay allows time for atria to empty blood into ventricles before ventricles contract.

Once ventricles contract, AV valves snap shut.

If no delay, AV valves would close too early & not enough blood would go into ventricles!

Slide12

U: Conducting

fibres

ensure coordinated contraction of the entire ventricle wall

Once through AV bundle, signal conducted rapidly to coordinate contraction of ventricles

Contraction of ventricles begins at the apex.Features of Purkinje fibers allowing fast signal:Fewer myofibrilsBigger diameterMore Na+ channelsLots of mitochondria and glycogen storesSignal conduction through heart animation

Slide13

NOS

:

Developments in scientific research followed improvements in apparatus or instrumentation

: invention of stethoscope led to improved knowledge of the workings of the heart.

Stethoscope = tool for listening to heart & lungs, and to check blood pressureInvented by Rene Laennec, 1816History of stethoscopeFirst tool allowing for non-invasive investigation of internal anatomy (e.g. abnormal heartbeats)Why was there a need? Before stethoscopes, doctors placed ear directly on chest…If patient obese, can’t hear heartbeatBathing was not social norm… gross!

Female patients… ‘

nuf

said

Slide14

Evolution of the stethoscope!

Slide15

N

ew Visual Stethoscope

records heart sounds for 10 seconds

Slide16

U:

Normal heart sounds are caused by AV valves and semilunar valves closing, causing changes in blood flow

Normal heart beat = 2 sounds

LUB

= closing of AV valvesDUB = closing of semilunar valves

Slide17

Skill:

Measurement & interpretation of heart rate under different conditions

Variables that can influence heart rate:

Types of exercise

Intensity of exerciseRecovery from exerciseRelaxationBody position Breathing and breath holdingExposure to a cold stimulusFacial immersion in water

Slide18

W

ays to take a pulse

Slide19

DBQ

p688

Cold Exposure & Heart Rate

Answers:

89 beats min-1 83 - 89 /89 × 100% = 6.7% declinedecline is small/data is variable; experiment limited: face or total exposure might have a more profound reduction/greater time of exposure might have an effect; data is inconclusive

Slide20

APP:

Use of artificial pacemakers to regulate heart rate.

Purpose

: maintain rhythm of heart beat

How it maintains rhythm:ConstantlyOnly when heartbeat is missed Why needed?SA node not workingBlock in signal pathwayHow it works? Ventricle stimulated with low voltage pulseAtria and ventricles stimulated

Slide21

Artificial pacemaker

Slide22

SKILL:

Mapping of cardiac cycle to a normal electrocardiogram (ECG) trace

P

wave = atrial systole (contract)

QRS wave = ventricular systole (contract)T wave = ventricular diastole (relax)Analysis of EKGs:Lengths of intervals between wavesHeight of R wave

Overall pattern compared before/after exercise or different positions of body

Slide23

Slide24

APP:

Use of defibrillation to treat life-threatening cardiac conditions.

Ventricle fibrillation

= twitching of ventricles due to rapid and chaotic contraction of individual muscle cells

Consequence: heart can’t pump any blood, cardiac arrestDefibrillator = device that discharges electrical current to restore normal heart rhythmNote: Can begin with ventricle tachycardia (“v-tach”) = fast heart rhythm

Slide25

Slide26

APP:

Causes & consequences of hypertension & thrombosis

Atherosclerosis

= hardening of arteries caused by formation of plaques (

atheromas) on insidePlaque = debris (fat, cholesterol)Clot = thrombosis = RBCs caught up in the plaqueCan lead to hypertension (high BP)

Consequences of thrombosis:

Blockage of blood flow

Myocardial infarction (heart attack)

Consequences of hypertension:

Narrow & stiff arteries

Aneurysm = bulging of weak artery (can burst and cause internal bleeding)

Stroke due to blood vessels in brain narrowing, clotting, rupturing, leaking

Kidney failure due to damage to arteries leading to kidney & damage to glomerulus

Slide27

Risk factors for thrombosis and hypertension

Genetics

Aging

Post-menopause (drop in estrogen) – estrogen may keep blood vessels flexible

Males (low estrogen)Smoking (raises BP)High-salt dietAlcoholStressHigh-saturated fat and cholesterol dietheight

Slide28

SKILL:

Interpretation of systolic & diastolic blood pressure measurements

Blood pressure

= arterial pressure

Ventricular systole/ventricular diastoleNormal = 120/80 mm HgHigh = 140/90 (only one has to be high)Pre-eclampsia = high bp during pregnancy

Slide29

Slide30

SKILL:

Analysis of epidemiological data relating to the incidence of coronary heart disease

Epidemiology

= study of spread of disease through a population

CHD = coronary heart disease = damage to heart as result of reduced blood supply to heart tissueOften caused by narrowing & hardening of coronary arteryGroups that may differ in CHD risk: ethnic, gender, age, physical activity, genetics, medical historyRoger VL, Go, AS, Lloyd-Jones DM, et al. Heart disease and stroke statistics—2012 update: a report from the American Heart Association. Circulation.2012:e2-e220.

Slide31

How to take Blood pressure

Slide32

Epidemiology of CHD

National Health and Nutrition Examination Survey: 2009–2012.