cardiovascular response to exercise Flashcards
describe how mean arterial pressure is regulated
- any change is detected by mechanosensors
- set point controlled by medulla
- to restore optimum the heart rate and peripheral resistance is altered
describe baroreceptors
- detect blood pressure on beat to beat basis
- located in cartoid bodies and aortic arch
how do receptors interact with effectors?
- via the medulla oblongata (primary cardiovascular control centre)
- signals sent to control heart
what changes when blood pressure changes?
- baroreceptor firing frequency
^ arterial pressure = ^ firing rate of arterial baroreceptor
when arterial pressure is too high what happens?
- decrease sympathetic outflow to heart, arterioles and veins
- increased parasympathetic outflow to heart
describe what happens when there is a fall in blood pressure
- cartoid/ aortic baroreceptors detect a hypotensive stimuli
- decrease in afferent baroreceptor nerve firing
what happens to the systems when blood pressure falls ?
- reduction in neural input to brainstem
- decrease in parasympathetic nerve activity to heart
- increase in sympathetic outflow to heart and vasculature
what is the mean arterial pressure?
90mmHg
how are blood volume and blood pressure linked?
- if kidney has high urinary loss of sodium and water due to an increased arterial pressure then plasma volume decreases
describe changes during exercise
- ^venous pressure
_ ^ end diastolic volume - ^ stroke volume
- ^ cardiac output
how do you work our mean systemic arterial pressure?
MAP= cardiac output (CO) x total peripheral resistance (TPR)
what factors increase end diastolic volume?
- increase in venous return
- muscle pump
- respiratory pump
- sympathetic stimulation
what is the difference in time taken for cardiovascular responses compared to kidneys?
cardio response in seconds compared to kidneys that take hours
describe neural controls
- vasoconstrictors= sympathetic nerves
- vasodilators= neurons release nitric oxide
describe hormonal control
- vasoconstrictors; epinephrine, angiotensin II+ vasopressin
- vasodilators; epinephrine, atrial natriuretic, peptide
describe local control
- vasoconstrictors = internal blood pressure (myogenic), endothelin- 1
- vasodilators= decreased oxygen, K+, C02, H+, osmolarity, adenosine, nitric oxide
what is a maximum oxygen uptake V02 max testing?
- aerobic endurance or power
what do submaximal tests assess?
- physiological responses to a standardised workload
what is steady state exercise?
- level of exercise at which the physiological responses remain relatively stable for an extended period of time
what are the three factors that govern steady state exercise?
- delivery of adequate oxygen to working muscles
- ability of cells to utilise the oxygen in the aerobic process of energy metabolism
-ability to eliminate heat
why are physiological responses of ventilation, oxygen consumption and cardiac output similar?
- involves four phases
summarise ventilation stages
- initial rapid rise in 1st min
- more gradual rise from min 1-3
- plateau at 3-5 mins
- drift from 1 hour to 4 hours
what is the initial rise in ventilation explained by?
- central command as motor cortex signals respiratory control centre to increase ventilation
what further act during the initial rise?
- mechanoreceptors
- in muscles/ limbs they detect movement and physical deformation
what is the subsequent gradual rise explained by?
- fine- tuning of respiratory neurons in response to central command and feedback control
- from arterial chemoreceptors in carotid/ aortic bodies
what is the initial rise in cardiac output explained by?
- central command, which is also inputted from mechanoreceptors in muscles (feedback control)
what are chemoreceptors responsible for relating to cardiac output?
- secondary gradual rise to steady state
- found in muscles
what is cardiac output secondly explained by?
Starling effect whereby when venous return of blood to heart increases, myofilaments are stretched to a more optimal overlap
- greater strength of contraction occurs
describe metaboreflex
- during exercise muscle metabolism ^ causing metabolites to accumulate in the muscle e.g. lactic acid
- receptors detect this sending afferent info to the brain as a result sympathetic nerve activity decreases
describe nerve activity during exercise
- sympathetic activity increases whilst parasympathetic decreases
what factors change during exercise? what does this result in and affect?
- increases heart rate, dilates arterioles to working muscles and constricts veins (feedback/ feedforward)
- results in blood redistribution
- affects heart rate and venules+ veins
describe redistribution of cardiac output during exercise
- more blood supply to skeletal muscle, skin and heart
- blood flow to digestive system decreases
- blood flow to brain remains constant
why does blood flow to brain remain constant?
- autoregulation ; fixed volume of cranial cavity cannot accommodate large increases in blood flow
why is blood increased to skeletal muscle?
- increase supply of oxygen available and removal of metabolic waste
why is blood increased to the skin?
- increased dissipation of heat
- thermoregulation
why is blood supply to the heart increased?
- more need for 02 supply
describe peripheral resistance during exercise
- combination of vasodilation and vasoconstriction overall reduce total peripheral resistance
- vasoconstriction in rest of body ^ peripheral resistance ^ sympathetic stimulation
why is peripheral resistance decreased?
- vasodilation in muscles, heart and skin
is cardiac output larger in trained people?
- yes
through training does maximal heart rate change?
- yes, trained people have a lower heart rate for a given workload
how does stroke volume change in trained people?
- increases ; only way of producing a higher maximal cardiac output
