Transcript Beating Hearts and Blood Pressure

Regulation of
Blood Flow
Chapter 10
Section 10.3
Cardiac Output
•
•
Cardiac output – the amount
of blood pumped from the
heart each minute.
Two factors affect cardiac
output:
1. Stroke Volume
2. Heart Rate
Stroke Volume and Heart Rate
• Stroke volume – the quantity
of blood pumped with each
beat of the heart.
• Heart rate – is the number of
times the heart beats per
minute.
• Cardiac output =
stroke volume x heart rate
Example of Cardiac Output
Cardiac output =
70 mL/beat x 70 beats/min
Cardiac output =
4900 mL/min
Blood Pressure
• Blood Pressure - The pressure
that is exerted against the vessel
walls when blood passes through
them.
• It can be measured with an
instrument called a
sphygmomanometer.
AKA - a blood pressure cuff
Blood Pressure Cuff
• Measures blood pressure –
usually in arm
• Recorded in millimeters of
mercury (1mmHg = 0.133kPa)
• Systolic pressure
Diastolic pressure
ex)
120
80
Systolic Pressure
• The max pressure during
ventricular contraction
– Pressure increases when the
ventricles contract and force blood
into the pulmonary arteries and
aorta
Diastolic Pressure
• The lowest pressure between
ventricular contraction
– Pressure decreases when the
ventricles relax
Applying What You Already Know
• As HR increases (ie. exercise)
ventricles push more blood out
at one time, so the pressure
also increases
– Affects systolic pressure
Hypertension
• Hypertension or high blood
pressure is cause by increased
resistance to blood flow.
• Increased resistance to blood
flow causes an increase in
blood pressure.
• Resistance can be caused by
the build-up of fat in the arteries.
Regulation of Blood Pressure
• Blood pressure receptors are located in the walls
of the aorta and the carotid arteries (on either side
of the neck).
• When high bp is sensed, a nerve impulse is sent
to the brain.
• Sympathetic (stress) nerve impulses are
decreased and parasympathetic (relaxed) nerve
impulses are increased.
• This causes the arteries to dilate and decreases
blood pressure.
**The opposite occurs when low bp is sensed**
Regulation of Body Temperature
•
Thermoregulation – the maintenance
of body temperature within the ideal
range.
•
To generate heat our bodies increase
cellular respiration.
•
To cool our body down our bodies do
one of two things:
1. Sweat
2. Dilate blood vessels near the skin
Regulation of Body Temperature - Cooling
• The evaporation of sweat off of skin
cools the skin.
• The dilation of blood vessels allows
more blood to the skin.
• Because skin has been cooled and is
now cooler than the blood, the blood
loses heat to the skin.
• The cooler blood then flows back
through the body and cools off the
interior organs.
Regulation of Body Temperature - Warming
• The circulatory system cannot supply
warmth, but it can reduce heat loss.
• Blood vessels constrict and flow to
the skin is reduced.
• Blood flow to the essential organs is
increased.
• This reduces heat loss from the skin.