Lecture 4 - Cardiovascular System Flashcards
Explain the 4 functions of the heart
Ensuring a one way blood flow
Generating blood pressure - Contractions of the heart generates blood pressure which ensures blood flow
Routing of blood in pulmonary and systemic ways - separation ensures better oxygenation of the blood
Regulating blood supply - changing rate force of each contraction to match the demands set by the muscles
Describe the conduction function of the heart
APs are created by the SA node which travels through to the Av node and through the bundle of Hiss through to the purkinje fibres to the apex (ventricle wall) which generates contraction
What is auto-rhythmicity and how are APs made
Auto rhythmicity is the ability of cardiac muscle to generate its own APs, APs travel to other cardiac cells which open voltage gated Na+ channels
5 stages of sympathetic control
4 stages of parasympathetic control
Dilate bronchioles Increase Heart rate Secrete adrenaline Decrease digestive secretion Decreases motility
Para: Constricts bronchioles Decreases heart rate Increases secretion Increases motility
What are the 2 nerves involved in parasympathetic control and describe it
Preganglionic - brain stem to terminal ganglia within the myocardial wall
Postganglionic - SA node av node coronary blood vessels & atrial myocardium
Has tonic control of heart rate and inhibitory influence at rest with a removal at exercise onset
Little effect on SV acetylcholine causes plasma membrane to become more permeable to k+
What happens during sympathetic control
Increases Hr and contractility with a greater force of contraction whilst decreasing ESV
However it has a limited ability to increase HR
Norepinephrine increases rate and degree of cardiac depolarisation, so frequency and amplitude of APs increase
Define heart rate variability and what it is sensitive to
The analysis of the variety of subsequent RR intervals
High variability is healthy
Gives us an insight into ANS control
What are the typical values for each of the cardiac hemodynamic factors
Q = 5L per min
SV = 70ml per stroke
Heart rate = 70-75bpm
Innate heart rate 90-100bpm
What does increasing HR do to EDV SV Q and VR
Decreases them all
What are the 2 types of chemoreceptors and what do they measure
Peripheral CO2 pH and O2 concentrations
Central CO2
Why does pH decrease when CO2 increases
How do we remove CO2
In what instance is this increased
Decreases because CO2 is transported mainly as carbonic acid
This leads to parasympathetic withdrawal and sympathetic instance therefore increased HR Q
So there is greater blood flow through the lungs and therefore more CO2 is expired
Exercise increases this
Define the Fick equation
How do we calculate SV
What is Starling’s law
Q * arterial and venous 02 difference
EDV- ESV
Starlings law is when EDV increases with VR and ESV decreases with stretch
What exercise intensity does SV increase to
40% of VO2
What is the relationship between heart rate and sub max work and what is the conconi deflection
Heart rate linearly increases proportionally to oxygen consumption
Conconi deflection is when heart rate increases at a decreased rate once past the anaerobic threshold
What happens to systolic and diastolic blood during exercise
Systolic = linearly decreases with dynamic exercise intensity and increases with force of contraction
Diastolic smaller increases with intensity and increases with isometric contraction
What happens to blood pH plasma volume and oxygen content during exercise
Blood pH: lowered due to affect of dissociation of lactic acid and transport of O2
Plasma volume: decreases hemocrit increases from 45to 50, caused by change in blood pressure then later due to sweating
Oxygen content : increased AVO2 difference decreased o2 venous content oxyhemoglobin curve shifts to the right
What is the influence of endurance training on Sv hr and Q
Peak VO2 equation
What is the influence of endurance on morphological aspects
Increased SV at rest and exercise decreased resting HR
Q * AV VO2
Increased left ventricle mass and wall thickness
How do we characterise an athletes heart
Bradycardia
Hypertrophy
Cardiomegaly
If found in non athlete there are issues
Define cardiovascular drift and where it occurs
The upwards drift in heart rate with a progressive decline in SV whilst maintaining the same exercise intensity
Occurs after 10mins of exercise and around 50-75% of VO2 max
What are the effects of hyperthermia
Hyperthermia leads to decreased Sv and therefore Q therefore increased systemic vascular resistance
And vasoconstriction of the CBF
Decreased heat dissipation
What are the % changes in Sv and q due to dehydration
28% in Sv and therefore 18% In Q and and increase in core temperature
What is hypoyvelemia
Dehydration of 3-5% equates to a 3-5% decrease in blood plasma volume
Reduces VR EDV SV
Accounts for 100% decrease in SV when dehydration but not hyperthermic
Accounts for 50% when both d and H
Dehydration alone = 7% decrease in SV
