3.1.1.2 Cardiovascular system part 4 Flashcards
what are the cardiovascular responses to exercise?
- increase systolic pressure (diastolic = same)
- HR and BP increase
- HR increase to increase rate of delivery of oxygen and fuel to working muscles
- SV & Q respond and change when exercise
what effects size of stroke volume?
vol of blood ejected from each ventricle per beat
- size of ventricle
- venous return
- force of ventricular contraction
- elasticity of cardiac fibres (degree of stretch of cardiac tissue during diastole, more stretch= increase force of contraction = increase ejection fraction (STARLINGS LAW)
what is the definition of End diastolic volume?
EDV: volume of blood left in ventricles just before they contract
adult at rest = 130ml
what is the definition of end systolic volume?
ESV: volume of blood left in ventricles after contraction
adult at rest = 60ml
Stroke volume equation
EDV-ESV
what is the ejection fraction?
% of blood actually pumped out of left ventricle per contraction
55% at rest
85% during exercise
= SV divided by EDV
what is the stroke volume response when exercise begins ?
- SV initially increases linearly as exercise intensity increases
- linear relationship holds up to 40-60% of max exercise intensity
- beyond SV values plateau and fall as exercise intensity increase and HR increases
- max SVs are reached during sub-maximal exercise (40-60%)
-any further increase in cardiac output must be due to a further increase in HR
what is the relationship between EDV and SV?
- EDV determines extent to which cardiac muscles are stretched
- more skeletal muscle fibres = more shortening during contraction = greater vol of blood entering ventricles during diastole more cardiac muscles stretched = greater SV during systole
- these cardiac muscles shorten during contraction = greater force of contraction of heart
- relationship between EDV and force of contraction of heart = Starlings law of heart
During exercise:
- activity skeletal muscles increase(contract more forcefully) = increase VR to heart (blood flow to atria and then ventricles) EDV increases and heart contracts more forcefully sv increase(cardiac muscles stretch to greater extent = more forceful contraction of ventricular muscles during systole = increase SV) , blood flow along veins assisted by contraction of working skeletal muscles
- increased rate and depth of breathing during exercise exerts a sucking action on veins near heart = increase blood flow into heart = further increase EDV and SV
why does SV decline as exercise intensity increases?
- HR (almost) increase directly with increase workload
- SV and Q reach max then decline
- decline = due to rapid heart beat at high workload = no time for complete filling of ventricles during diastole
- decrease in EDV and decrease in SV
- rapid heartbeat = only partial emptying of ventricles during systole = decreasing SV and Q
what is resting heart rate and bradycardia ?
- av resting HR 70-75bpm
- low resting HR = high levels of aerobic/endurance fitness
bradycardia describes slow heart rate below 60bpm
Q is same at rest no matter fitness
-occurs as a consequence of increased SV due to
increased size of heart muscle (hypertrophy)
heart rate and exercise what is the connection?
- Hr increases above resting values prior to exercise
- anticipatory rise due to release of adrenaline from adrenal glands (Acts on SA node increase rate at which cardiac impulses are emitted increase HR and acts on ventricle = more forceful)
- linear relationship between heart rate and exercise intensity until reach high workload and HR increases/decreases accordance with exercise intensity
- HR slows as maximal rates are approached (transfer to anaerobic exercise)
- sub-maximal = HR reaches plateau (optimal steady state for meeting oxygen demand at specific workload)
- HR plateau reached during constant rate of sub-maximal work
- lower steady heart rate more efficient heart
capillaries
- one cell thick
- one RBC at a time
- human body 40,000km of capillaries
- blood in capillaries always moving = steep concentration gradients for oxygen and carbon dioxide and nutrients persist across capillary walls ensuring exchange of materials is efficient
pathway of blood along blood vessels
heart - artery - arteriole - pre capillary sphincters muscle - capillaries (diffuse into muscle and changes from oxygenated to deoxygenated) - venue - vein
oxygen is carried in the blood by ?
- 3% in blood plasma in simple solution (solubility of O2 in water is relatively low = transport in plasma alone couldn’t meet needs of respiring tissue
- 97% in combination with protein haemoglobin = oxyhemoglobin (HbO2) (oxygen carrying capacity of blood = significantly increased by presence of Hb in RBC
haemoglobin
iron-containing pigment found in RBC which combines with O2 to form oxyhaemoglobin
-high affinity for oxygen
-each haemoglobin molecule therefore carries 4 molecules of oxygen when fully loaded
Hb + 4O2 = HbO8
-readily loads with O2 in the lungs and unloads its O2 at the muscle tissues
- 2 alpha chains
- 2 beta chains
-behaviour of Hb within the red cells is key to understanding of how this additional oxygen is supplied to working muscles
plasma
fluid part of blood (mainly water) surrounds blood cells and transports them
gaseous exchange
high to low partial pressure
exchange of gases between lungs, blood and tissue cells = respiration
- oxygen and CO2 are exchanged at tissues (and at alveoli)
- tissues: oxygen diffuses into along a diffusion gradient
- CO2 diffuses = blood capillaries along a diffusion gradient
external respiration
(pulmonary respiration)
-exchange of gases between lungs and blood
partial pressure of O2 is greater in alveolar gases than in blood plasma
- exercise = muscle tissue utilises increase amount of O2 from the blood capillaries = higher levels of CO2
- increase in O2 uptake and CO2 release = consequence of faster rates of cellular respiration = generates energy requires for muscle contraction
- muscle tissue utilises more oxygen and releases greater concentrations of CO2, venous blood returning to the heart and lungs = higher PPCO2 and lower PPO2 compared to at rest
- exercise = steeper pressure/diffusion gradients between alveolar air and blood capillaries are generated = increase rate of gaseous exchange at alveoli
internal respiration
(tissue respiration)
-exchange of gases between blood and cells of the tissues
PP of O2 is greater in blood than in tissue fluids
oxyhemoglobin dissociation
release of oxyhemoglobin to tissues
partial pressure PP
same of oxygen tension
relative pressure of a gas in a mixture of gases
total pressure of gas mixture is the sum of partial pressures of the gases in the mixture
myoglobin
muscle haemoglobin an iron-containing muscle pigment in slow twitch muscle fibres
has a higher affinity for oxygen than haemoglobin, stores oxygen in muscle fibres can be used quickly when exercise begins
in muscle oxygen is stored by myoglobin
oxygen dissociation curve for haemoglobin
graphical representation of behaviour of Hb when subjected to differing partial pressures (concentrations) of oxygen (tells us how much oxygen muscles get)
lungs= 12kPa
tissues=6kPa at rest, 2kPa during exercise
-during exercise we get an increase in a-VO2 diff
-steep part of the curve coincides with the normal working range at the tissues
saturation of Hb
100% of oxygen in Hb in blood in lungs (oxygenated)
fully saturated until capillaries in muscles
dissociation curve description
sigmoidal in shape and displayed % saturation of Hb with oxygen at varying oxygen concentrations (partial pressures)
-during exercise metabolic demands of working muscles increase, increase supply of O2 is required to meet these demands
meaning of the dissociation curve
- rest PO2 in muscles is around 6kPa
- high intensity PO2 = 2kPa - muscles need oxygen = contract
- Hb saturation with oxygen low at around 15% = muscles are being loaded with oxygen
- blood enters capillaries in muscles = low PO2 means 85% of oxygen dissociates from Hb (oxygen is unloaded from the the haemoglobin to the muscles)
- low PO2 = exercise = lower the affinity for oxygen with haemoglobin meaning it is easier for oxygen to unload from the Hb and load the muscles
changes in muscles during exercise
- muscle temp increases
- muscles PO2 decreases
- muscle PCO2 increases
- muscle pH decreases
Bohr shift
- dissociation curve shifts to the right
- lower % saturation of Hb with O2 - more unloading to the muscles - greater O2 to muscles
1. CO2
2. temp
3. pH
this is due to the 4 changes in muscles (can be caused by just 1 )
a-vO2 diff
difference in oxygen content in arterial blood (arriving muscle) & venous blood (leaving muscle)
at rest: a-vO2 diff = 5ml per 100ml blood
during intense exercise: a-vO2 diff = 15ml per 100ml blood
a-vO2 diff during exercise
a-vO2 diff increases with training particularly at maximal workloads
- due to increased oxygen extraction by active tissue caused by:
- more effective blood shunting (vasoconstriction & vasodilation)
- improved capillarisation of trained muscle (no of capillaries in muscle increases)
- more efficient use of existing capillaries
- due to the increased need for energy and in endurance/stamina (aerobic) = quicker recovery and fatigue later
- increased diffusion at lungs/alveoli/muscle - venous blood has less oxygen during exercise
cardiovascular drift
HR increases to meet oxygen demand at working muscle
SV and arterial blood pressure decreases
Q is maintained/slightly increases
-cardiac drift occurs result of reduced plasma volume (liquid part of blood)= reduce venous return and stoke volume = compensated for by an increase in HR which tries to cool body down ad a result of body fluid lost (usually through sweating)
HR increase as there is more viscous blood and increase in temp = radiate from skin
impact of sport and activity on health: positively
- prevent heart disease (improve blood circulation and decrease blood pressure
- reduces high cholesterol reduces weight - reduces amount of low density lipoproteins (LDL) e.g. bad cholesterol in blood
- prevents a stroke (caused by shut off of oxygen to the brain)- reducing high blood pressure and prompting weight loss - promote blood circulation to brain
impact of sport and activity on fitness
- cardiac output- higher due to cardiac hypertrophy & more efficient - pump more blood each beat increase SV = beat less to deliver oxygen = lower resting heart rate = increased cardiac output
- components of fitness meeting demands of environment
- increase in capillary density - muscle and alveoli
