Transcript Cardiovascular Control During Exercise

Cardiovascular Control
During Exercise
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
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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
The ECG
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
(fig 8.11)
• 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

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
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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

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
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