Lecture 17 - The Caridac Cycle Flashcards
The cardiac Cycle
- Contraction of atria
- Followed by contraction of ventricles
- Followed by a rest when neither chamber is contracting
contraction
Systole - BP: (120)/80
Relaxation
Diastole - BP: 120/(80)
Pre Load
Initial stretching of the cardiac myocytes prior to contraction
After load
Diastolic Arterial Pressure - the pressure the heart must work against to eject blood during systole
Nodes
- SA (Sinoatrial Node): Heart’s natural peacemaker where electrical impulses are generated
- AV (atrioventricular) node
Nerves
- bundle of His
- Bundle of branches
- Purkinge fibres
Intercalated discs
Gap junctions
- cardiac myocytes connected by intercalated discs to work together as a single function organ
Arrhythmia
irregular heart rate or rythm
Abnormal SA node firing
Can result in tachycardia and bradycardia
Blocks (blockages in the heart)
- Slow down or prevent signal propagation from atria to ventricles
- ventricles can contract independently
Arterial Fibrillation (A-Fib)
Quivering or Irregular Heartbeat
Ventricular Fibrillation (V-fib)
The most serious cardiac rhythm disturbance
- loss of consciousness or death
Neural and Endocrine Signals Control Strength and Rate of Heart Contractions
- Sympathetic innervation (norepinephrine): increases heart rate
- Parasympathetic innervation (acetylcholine): decreases heart rate
- Epinephrine: Increases the strength of each contraction
Hypertrophy
Sign of being “overworked”
- the heart muscle will respond just like when you’re weight-lifting
LV Chamber - Endurance athletes
Increase as they need to increase cardiac output
LV Chamber - Weightlifters
Increased LV wall and septum thickness to accompany for overcome the pressure difference when they hold their breath during lifts
Enlargement of the Heart - Bad
Causes include high blood pressure and narrowing of aortic valve the heart must work harder
Enlargement of the heart - good
Athlete’s Heart
Atherosclerosis
- Narrowinf of arteries due to the calcifies fatty deposits and thickening of the wall
- triggered by damage to the arterial wall
- can lead to heart attack or stroke
Atherosclerosis - factors
- Elevates blood lipids
- Hypertension
- inflammatory mediators
- diet
- smoking, physical inactivity, obesity/diabetes
- age, genetics
Treating Coronary Artery Blockages
- Angioplasty
- Bypass Surgery (saphenous vein is used)
systolic blood pressure
Maximum pressure when the ventricles contract and send blood to the artieries
Diastolic blood pressure
Minimum pressure when the heart relaxes between beats (not zero due to elastic recoils of arterial walls)
Normal Blood Pressure
Systole: Less than 120
Diastole: Less than 80
Elevated Blood Pressure
Systole: 120 - 129
Diastole: Less than 80
high blood pressure- hypertension stage 1
Systole: 130 - 139
Diastole: 80 - 90
High blood pressure - hypertension stage 2
Systole: 140 or higher
Diastole: 90 or higher
hypertensive crisis
Systole: Higher than 180
Diastole: Higher than 120
Vasoconstriction
- Alpha-receptors are located on arteries
- Norepinephrine and epinephrine bind to a2 adrenergic receptors
- increases blood pressure
- ex. During exercise
Vasodilation
- Norepinephrine and epenipherine bind to b2 adrenergic rectors found in arteries of skeletal muscle
- this dialates vessels of the skeletal muscles so they can receive increased blood flow
- during exercise (more blood, more oxygen, more fuel)
Does Blood Pressure Increase during Aerobic Exercise
No
- distribution of blood flow doesn’t not increase proportionally (to working muscles)
- Dilation: vessels to skeletal muscle and heart increases blood flow to muscles
- Constriction: vessels to the gut and kidneys decreases blood flow to these organ
Does Blood Pressure increase during resistance exercise?
Yes
- Holding your breath: increases intra thoracic pressure during the lift
- Temporarily raises blood pressure and slows heart rate
