1.1b- Cardiovascular System Flashcards
Cardiovascular system
The transport system of the body responsible for carrying oxygen and nutrients to the body and carrying away carbon dioxide and other wastes; composed of the heart, blood vessels, and blood.
Pathway of blood through the heart
superior vena cava, inferior vena cava, right atrium, tricuspid valve, right ventricle, pulmonary artery, lung capillaries, pulmonary vein, left atrium, mitral valve, left ventricle, aorta
Pulmonary circuit
Carried deoxygenated blood to the lungs and oxygenated blood back to the heart
Systemic circuit
Carries oxygenated blood to the body and deoxygenated blood back to the heart
conduction system
Electrical impulses from nerves that stimulate contraction and relaxation of heart
Cardiac cycle
one complete heartbeat- movement of blood
Myogenic
Describes muscle tissue (heart muscle) that generates its own contractions/electric impulses
How many structures make up the conduction system?
5 structures- they create and transmit an electrical impulse through the cardiac muscle.
SINO-ATRIAL (SA) NODE
located in the right atrial wall. It generates the electrical impulse and fires it through the atria walls, causing them to contract. (AKA the ‘pacemaker’ as the firing rate will determine HR.)
Atrio-ventricular (AV) Node
Collects the impulse and delays it for approx 0.1 seconds to allow the atria to finish contracting. The releases impulses to the bundle of His
Bundle of His
located in the septum of the heart. It separates the impulse in 2, ready to be distributed through each separate ventricle.
Bundle Branches
these carry the impulse to the base of each ventricle.
Purkynje Fibres
these distribute the impulse through the ventricle walls causing them to contract.
The cardiac cycle
The process of cardiac muscle contraction and the movement of the blood through its chambers. Involves both diastole and systole stages
What does 1 complete cardiac cycle represent?
The sequence of events involved in a single heartbeat. Takes around 0.8 secs
2 phases of cardiac cycle
systole (contraction) and diastole (relaxation)
Cardiac diastole
the relaxation of the cardiac muscle, firstly of the atria and then the ventricles
Cardiac systole
the contraction of the cardiac muscle, firstly of the atria and then the ventricles
Diastole phase
Atria and ventricles relax and expand drawing blood in. Pressure in atria increases opening AV valves and allows blood to enter ventricle passively
Atrial systole
Atria contract and blood is forced through the AV valves into the ventricles.
Ventricular systole
Ventricles contract and increase pressure which closes AV valves. SL valves are forced open as blood is ejected from the ventricles
What is blood pressure?
the measure of the force used to pump blood around the body
What do the numbers represent?
Blood pressure is given as 2 figures:
systolic- pressure when blood is pushed out
diastolic- pressure during rest
systolic/diastolic
Healthy blood pressure
90/60 to 120/80
Conduction & Cardiac Cycle- Diastole
No electrical impulse occurs
Conduction & Cardiac Cycle- Atrial Systole
Impulse from SA node to AV node
Conduction & Cardiac Cycle- Ventricular Systole
Impulse moves from the AV node to:
Bundle of His -> Bundle branches -> Purkinje Fibres
Heart rate
The number of cardiac cycles (beats) per minute
Stroke Volume
the volume of blood pumped out by left ventricle with each heartbeat
Cardiac output
The volume of blood ejected from the left side of the heart in one minute.
Untrained performer at rest- HR, SV, CO
Approx 72bpm, 70ml/beat, 5 l/minute
Trained athlete at rest- HR, SV, CO
Lower than 60bpm, 100ml/beat, 5l/minute
Untrained performer maximal- HR, SV, CO
220-(age), 100-120ml, 20-30 l/min
Trained athlete maximal- HR, SV, CO
220-(age), 160-200ml, 30-40l/min
What is generally accepted about heart rate?
The lower the heart rate the more efficient the cardiac muscle is lowered
Bradycardia
slow heart rate (less than 60 bpm)
When does stroke volume occur?
during ventricular systole
What does SV depend on?
Venous return and ventricular elasticity and contractility
Venous Return
The amount of blood returned to the heart by the veins. More blood returned= more blood available for ejecting
ventricular elasticity and contractility
the degree of stretch in the cardiac muscle fibres. Greater stretch= greater force of contraction
When is cardiac output more efficient?
If cardiac hypertrophic occurs. More blood can be ejected and HR can reduce
How does Cardiac output differ between elite and untrained performer?
Over CO is the same but it differs in how it’s broken down into SV AND HR
What happens with demand for oxygen when we exercise?
It rapidly increases. The CV system has to increase O2 blood flow to muscles. Response of cardiac muscles depends on intensity
Sub-maximal exercise
A low-to-moderate intensity of exercise within a performer’s aerobic capacity
Maximal exercise
a high intensity of exercise above a performer’s aerobic capacity that will induce fatigue and exhaustion
Heart rate response to sub maximal exercise
Initial anticipatory rise in HR prior to exercise due to adrenaline release. Rapid increase of HR at start of exercise to increase blood flow in line with exercise intensity.
HR plateau throughout the sustained intensity exercise. As recovery is entered, rapid decrease in HR as muscle pump action reduces
More gradual HR decreases
Heart rate response to maximal intensity exercise
HR doesn’t plateau as exercise intensity continues to increase. Growing demand for O2 and waste remove that HR must strive to meet.
Heart rate response to dynamic sports
HR response fluctuates in line with the demands placed upon it
Stroke volume response to exercise
SV increases in line with exercise intensity up to 40-60% of maximal running speed. After this point SV plateaus, this is due to the continued increase in HR reducing VR and ultimately SV.
Why is stroke volume able to increase
Increased venous return- vol of blood that returns from the body to the heart. Increases during exercise so more blood returns to heart
Starlings Law
The Frank Starling Mechanism (Starling’s Law)
Increased venous return leads to an increased stroke volume, due to an increased stretch of the ventricle walls and therefore force of contraction.
What happens to Stroke volume in sub maximal intensities?
Reaches a plateau because increased heart rate towards maximal intensities does not allow enough time for ventricles to fill completely with blood in the diastolic phase, limiting Starlings Law.
What does stroke volume maintain?
the blood flow and removal of waste products while lowering stress and workload on cardiac muscle.
What is cardiac output the product of?
heart rate and stroke volume
increase of cardiac output in exercise
increases in line with exercise intensity and plateaus during maximal exercise. Recovery- rapid decrease followed by a slower decrease
resting cardiac output in trained and untrained performers
doesn’t differ. how it’s split up is what is different.
cardiac output equation
CO = HR x SV
Cardiac Control Centre
A control centre in the medulla oblongata responsible for HR regulation. Determines the firing rate of the SA node- involuntarily regulates HR. Receives info from sensory nerves and sends direction through motor neurones.
control mechanisms for CCC
Neural control, intrinsic control, hormonal control
Neural control
release of some hormones directly controlled by the nervous system- chemoreceptors, proprioceptors, baroreceptors
intrinsic control
Makes use of chemical signals, operates at the tissue and organ- temperature control and venous return changes
Hormonal control
Release of adrenaline and noradrenaline
Sympathetic nervous system
actioned if an increase in HR is required. Releases adrenaline, noradrenaline and sends stimulation to SA node via accelerator nerve.
Parasympathetic nervous system
actioned when a decrease in HR is required. Actioned via the vagus nerve.
Regulation of HR during Exercise
HR increases during exercise somewhat because of a decrease in the parasympathetic tone, but mainly because of an increase in sympathetic stimulation
Regulation of HR in response to recovery
Parasympathetic nervous system decreases stimulation of the SA node via the vagus nerve to decrease HR. Reduced force of ventricular contraction reduces SV slowly
the vascular system
dense network of blood vessels that reach every corner of the body
what does blood consist of?
plasma, red blood cells, white blood cells, platelets
45% cells and 55% plasma
Functions of blood
transportation, regulation, protection
Arteries
Blood vessels that carry blood away from the heart. Oxygenated blood from heart to organs. Carry at high pressure. Large layer of smooth muscle and elastic tissue to smooth pulsating blood flow.
Arterioles
smallest arteries. Layer of smooth muscle surrounding entry to capillary bed- controlling blow flow.
Vasodilate
Widening of arteries, arterioles and pre-capillary sphincters
vasoconstriction
narrowing of the arteries, arterioles and pre-capillary sphincters
Capillaries
Microscopic vessel through which exchanges take place between the blood and cells of the body. Thin- single layer of cells
Veins
Blood vessels that carry blood back to the heart. Slow moving blood at low pressure. Contains valves.
Venules
small vessels that gather blood from the capillaries into the veins
Venodilation
widening of veins and venules
venoconstriction
narrowing of veins
Mechanisms of venous return
pocket valves, smooth muscle, gravity, muscle and respiratory pump
Pocket valves
prevent back flow of blood
smooth muscle
venoconstricts to create venomotor tone to aid blood movement
gravity
helps upper body blood to return
muscle pump
The rhythmic mechanical compression of the veins that occurs during skeletal muscle contraction in many types of movement and exercise, for example during walking and running, and assists the return of blood to the heart.
respiratory pump
pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
venous return and recovery
CO still high after exercise and there may not be sufficient pressure to return blood, can cause feelings of dizziness and heavy legs. Means active recovery is important.
Cardiac output distribution at rest
75% goes to organs for digestion, filtration and excretion
cardiac output distribution at exercise
more co goes to muscles 88%
blood supply in heart
coronary blood supply
Vascular Shunt mechanism
The redistribution of cardiac output around the body from rest to exercise increasing flow to skeletal muscles. At rest, high CO goes to organs
Vasodilation and constriction during rest
Organ arterioles and pre-capillary sphincters-vasodilate to increase flow
Muscle arterioles and pre-capillary sphincters- vasoconstrict to decrease flow
Vasomotor control centre
The control centre in the medulla oblongata responsible for cardiac output distribution- vascular shunt mechanism
How does the VCC allow the vascular shut mechanism to occur?
Smooth arterial muscles are always in a slight state or contraction. When sensory info is received, VCC alters levels of stimulation sent to arterioles and pre-capillary sphincters at different places. Allows vascular shunt to take place.
Where does the VCC receive information from?
chemoreceptors and baroreceptors
Increase sympathetic stimulation
contract vessel walls -
lumen constricts- vasoconstriction
Limits blood flow
Decreased sympathetic stimulation
decreased sympathetic stimulation-> vasodilation-> increased vessel diameter-> increase blood flow
