CVM Week 9 - Exercise and the ageing heart Flashcards
What does chronotropic mean?
Increases the heart rate and therefore speed of the cardiac cycle
What does dromotropic mean?
Affects the conduction speed of the AV node, which helps increase the rate of the heat
What does inotropic mean?
Increasing the force of the contraction of the heart
What does lustitropic mean?
Refers to the relaxation of the myocardium
What changes occur in the heart during exercise?
Increased SNS vs PNS tone
Increased cardiac output - up to 5x greater than resting
Heart rate increase
Ejection fraction increased ( % of end diastolic volume ejected)
Better venous return to heart via skeletal muscle pump action allows greater greater CO despite shorter time for ventricular filling
What changes occur in the blood vessels during exercise?
30x more flow to into skeletal muscles
100x more consumption of oxygen in skeletal muscles
Vasodilation in vessels supplying muscles
Arterioles dilate and increased surface area of capillary beds
Restriction of blood flow to organs that aren’t essential in exercise
What causes the vasodilation in vessels supplying muscles during exercise?
Decreased pH
Decreased PO2, increased PCO2
Higher temperature
Why is decreased velocity of blood flow thought capillary beds beneficial in exercise?
It allows for better oxygen delivery as the RBCs are moving through the capillaries more slowly and able to release oxygen more efficiently
Which organs is blood most notably directed AWAY from during exercised?
Kidneys and again tract (both going from over 20% blood flow down to 1%)
What happens to fluid movement in interstitial spaces during exercise?
Increases into the interstitium, and lymph flow also increases
What changes occur in the lungs during exercise?
Breathing deeper a and more rapid
Alveolar ventilation increase 20x
Blood flow in lungs increase from 5-25L or more (must accept what the heart pumps)
Why does oxygen delivery to tissues increase with exercise?
Decreased pH and increased CO2 in tissues leads to Hb releasing more oxygen at the tissues as binding of H+ on Hb favours oxygen unloading
What is oxygen debt?
Where short term energy demands are my by anaerobic respiration and lactate builds up. It requires oxygen to restore back to normal pH and is why you breath deeply after a sprint.
What is a stitch in your chest an indicator of? What is it caused by?
Hypoxia to diaphragm, due to a lagging behind of the cardiopulmonary system supply of oxygen, and the demand for oxygen.
What is the major effect of aerobic/dynamic exercise?
Increased cardio respiratory fitness. More ability to provide oxygen rich blood to the tissues over a sustained period
What does flexibility exercise achieve?
Improve full range and motion of muscles and joints
What effects do resistance/static exercise achieve?
Increases muscle strength. Not so much impact on increasing stroke volume as this type of exercise doesn’t greatly increase venous return.
What happens to resting heart rate in someone who performs endurance/aerobic training?
Lower resting heart rate due to increased stroke volume supplying the same cardiac output
What happens to blood volume in aerobic athletes?
Increases
What is physiological hyper Trophy?
The increase muscle thickness of ventricular walls as a result of increased preload as a result of exercise
What cardiac output can be achieved in an elite athlete?
35-40 litres per minunte
On a cellular level, what happens to the mitochondria of skeletal muscle cells in aerobic athletes?
Increase in number to facilitate increased metabolism allowing for better oxygen extraction
What is the lactate threshold?
Maximal rate of oxygen consumption before blood lactic acid levels rise.
If training doesn’t affect heart rate, how does cardiac output increase with training?
CO = SV x HR
So if HR stays the same, stroke volume must increase. This is due to the physiological hyper trophy along with increased SNS tone that has a positive inotropic action. Essentially causes a stronger contraction which ejects more blood from each beat
In what two states does cardiac remodelling occur?
Physiological (exercise) and pathological state
What is remodelling triggered by?
The volume of blood attempting to fill the ventricles, the neurohumoral and local regulatory factors (endothelin, nitric oxide)
Distinguish between eccentric a concentric hypertrophy?
Eccentric is improved compliance and myocardial energetics (exercise)
Concentric is where increased stiffness and energy demand occur (pathological)
What is a major functional difference in the healthy hypertrophy and the pathological hypertrophy?
Presence of fibrosis. Healthy heart has none and the diseased heart will have mild to extensive fibrosis which will affect cardiac output
What factors determine the extent of physiological hypertrophy in exercise?
The type of exercise (mixed aerobic I.e. Rowing is highest)
Age (older than 16 can develop bigger hearts)
Gender (women generally don’t)
Size (bigger body means bigger ability to increase heart size)
Ethnicity
If the baroreceptor reflex gets slower in old age, what effects does this have?
There is postural hypotension (low blood pressure when you get up too quickly)
Spontaneous changes in blood pressure
Why are older people prone to dyspnea during exertion?
Elevated LA and LV pressures are associated with have to pump blood above high afterload. This can lead to ineffective delivery of oxygen rich blood to skeletal muscle.
Why is hypertension common in old age?
Atherosclerosis, loss of arterial elasticity and nicotine induced vascular damage
What effect does fibrosis/calcification have on a heart valve?
Predisposed patient towards stenosis/regurgitation
Causes cardiac workload to increase and predisposed towards heart failure
