sports 4
TRANSCRIPT
Cardiovascular Control During Exercise
SEKOLAH TINGGI ILMU KESEHATAN KOTA SUKABUMI
Program Study S1 Keperawatan
https://stikeskotasukabumi.wordpress.com
Cardiovascular Functions
Delivery• Oxygen and nutrients
Removal• CO2 and metabolic wastes
Transport• hormones
Maintenance• Body temperature• Fluid leves and pH
Prevention• infection
The Heart
Blood flow through the heart (fig
8.1)
The myocardium• interconnected cardiac muscle• hypertrophy of left ventrical
The cardiac conduction system (fig 8.3)• Autoconduction: the ability to generate its own
electrical signal rythmically without neural stimuation.
• SA node: (pacemaker) sends the electrical impulse to the atria and reaches the AV node.
• AV node: conducts the impulse from the atria into the ventricals through the ....
• AV bundle and Perkinji fibers where it travels along the septum and to the ventrical walls starting at the Apex.
The Heart
Extrinsic control of heart activity• the parasympathetic nervous system
– decreases H.R. & force of heart contraction
• the sympathetic nervous system – increases H.R. & force of heart
contraction• the endocrine system: release
norepinephrine and epinephrine to increase H.R.
The ECG (fig 8.4)
• records the electrical activity of the heart– the P wave: atrial depolarization
– the QRS complex: ventricular depolarization
– the T wave: ventricular repolarization
Cardiac Arrhythmias
Bradycardia: “slow heart”• Resting H.R. < 60
Tachycardia: “fast heart”• Resting H.R. > 100• Symptoms include– Fatigue–Dizziness– Lightheadedness– Fainting
Premature ventricular contraction: “skipped beat”
Ventricular Fibrillation: “uncoordinated beat”
The Heart
The Cardiac Cycle: includes all of the events between two consecutive cycles
• Diastole: relaxation phase• Systole: contraction phase
Stroke Volume (SV): the amount of blood ejected from the left ventrical (fig 8.5).• SV = EDV - ESV
• end diastolic volume (EDV)• end systolic volume (ESV)• ejection fraction (EF) =
(SV / EDV) X 100%• cardiac output (Q) = HR X SV
The Vascular System Method: Aorta --> Arteries -->
Arterioles --> Capillaries -->Venuoles --> Veins --> Vena Cava
Coronary arteries Return of blood to the heart• breathing increases thoracic
pressure• muscles create a pumping action• valves prevent backflow
The Vascular System
Distribution of blood (fig 8.6)
• autoregulation: the vessels ability to detect the local chemical changes and regulate its own blood flow to meet the needs of the tissues.
• extrensic neural control: regulated largely by the sympathetic nervous system by constricting blood vessels of lesser need.
• redistribution of venous blood: creating more available blood to meet the needs of the body.
During Exercise: blood is redirected to the areas where it is needed most• Muscles receive up to 80%
The Vascular System
Redistribution of Venous Blood• 64% of blood pools in the veins
waiting for the need.
Blood pressure• systolic / diastolic
– Measured sitting and supine/prone
• control: weight loss, diet, exercise, med’s
• Hypertension: 140 / 100• Hypotension: 100 / 60
The Blood Functions• Transportation of nutrients,
hormones, etc.• Temperature regulation• Maintain (pH) balance
Blood volume and composition• Men 5 - 6 L, Women 4 - 5 L• composition (fig 8.8)– 55% plasma• 90% water
– 45% hematocrit• red blood cells: transport
oxygen primarily bound to their hemoglobin (iron).• White blood cells• platelets
The Blood
Blood viscosity: refers to the thickness of the blood.• increased viscosity restricts blood
flow but increases oxygen carrying capacity.
• decreased viscosity increases blood flow but decreases oxygen carrying capacity.
Cardiovascular Response to Exercise
Increased stroke volume
• only up to 40%-60% of maximal capacity & then plateaus (caused by reduced filling time at higher h.r. ?)
• increased volume of venous blood return– increased muscle pumping of venous
blood– increased breathing (thoracic pressure)– supine positions
• increased ventrical enlargement capacity– Frank-Starling law: when the ventricle
stretches more, it will contract with more force.
• increased ventrical contractility• aortic or pulmonary artery pressure
Cardiovascular Response to Exercise
Increased heart rate / cardiac output (fig 8.10)
Anticipatory response (increased heart rate before exercise) • Caused by the release of epinephrine
Steady state heart rate: during steady exercise
Maximum heart rate = 220 - age
Cardiovascular Response to Exercise
Redistribution of blood to the working muscles by reducing blood flow to the kidneys, stomach, liver and intestines.
Redistribution of blood to the skin in order to maintain body temperature.
Increased metabolic rate of working muscles
Autoregulation is triggered by low muscle Po2
Cardiovascular drift: increased H.R. compensates for a decreased S.V. from a decreased total blood volume to maintain Q.• redistribution• decreased blood plasma
Cardiovascular Response to Exercise
Systolic B.P. increases with intensity• valsalva during resistance
exercise• increased use of upper body
musculature Diastolic B. P. does not change
Cardiovascular Responses to Exercise
Increased A-V O2 difference: representing the amount of O2 extracted from the blood to be used by the muscles.
Decreased plasma volume =decreased performance increased blood pressure forces water from the vascular system to the interstitial spaces.• increased intramuscular osmotic
pressure attracts fluid to the muscles.• sweating
Increased blood viscosity• decreasing O2 transport
Decreased blood pH level