Transcript lecture slides

Cardiovascular System
-Heart AND Blood Vessels function together
-Bulk Transport vs. Diffusion
-Laws of Chemistry and Physics set limits
-The way evolution builds it is NOT the way
an engineer would build it
Cardiovascular Essential
Questions
• What are the functions of the CV system?
• What are the different types of CV systems
(open; closed)?
• Why are there 2, 3 and 4 chambered hearts?
• How does the body monitor and adjust CV
function?
Surface area to volume ratio
(Large surface area needed wherever diffusion is utilized)
Heart, bronchi and some of the arteries
Arteries of the
systemic circulatory
system
(torso)
Arteries of
the neck
and brain
Functions of the Cardiovascular
System
There is much more blood
flowing to the rabbit’s ears than
is needed to support that
amount of tissue.
Whenever you see a
disproportionately large
amount of blood flowing to a
region you know there must be
more going on than just
delivery of nutrients.
Functions of the Cardiovascular
System
•
•
•
•
•
•
Deliver Nutrients (O2, glucose, fatty acids, water*)
Remove Wastes (CO2, nitrogen compounds, water*)
Heat/Cool (deliver or remove heat)
Deliver Hormones (epinephrine, cortisol)
Movement (spider jump)
Certain aspects of reproduction (erection)
Open
vs.
Closed
Spider Jump
Leg extension in spiders
involves pumping of fluid
into legs to “inflate” them
They do have muscles to
flex their legs.
Types of Closed CV Systems
Two chambers
(one ventricle*)
Three chambers
(one ventricle*)
Four chambers
(two ventricles*)
*Ventricles are responsible for doing all the work
Dual Circulation
Dual Pump
Systemic
*to body
*high oxygen in
arteries
Pulmonary
*to lungs
*low Oxygen in arteries
Left more muscular
Does more work
Electrical Activity Coordinates
Heart Beat
• Pacemaker cells set Heart Rate
• Sympathetic Activation
– Speeds up rate
– Strengthens contraction of muscle
• Parasympathetic Activation
– Slows rate
– Weakens contraction
Physics of Blood Flow
• CV system must provide blood flow
BUT…
• It must also provide pressure
Blood Pressures and Posture
Density of blood is similar
to density of H2O therefore
similar changes in pressure
with posture
1 mmHg = 13.5 mm H2O
(0.53 inches H2O)
44mmHg = 594mm H2O
(23 inches H2O)
~23in
What about other creatures?
100 mmHg
What is the blood
pressure in the head of a
giraffe?
260 mmHg
420 mmHg
14 ft
What about creatures that lie flat?
Ohm’s Law
•
•
•
•
V=IR
Pressure = Flow x Resistance
P = Cardiac Output x Total Peripheral Resistance
C.O. = Heart Rate x Stroke Volume
• P = (H.R. x S.V.) x TPR
Blood Vessels
Blood Vessels
Blood Pressure in CV system
Need pressure for filtration
Where is
the
blood?
Where is the blood?
Do we have more blood than we
need?
• Veins of the systemic circulation act as a
reservoir where blood is allowed to pool
under resting conditions.
• When more Pressure and C.O. is needed,
not only does the heart beat faster and
stronger, the veins squeeze on this
reservoir to push more blood back to the
heart.
• Veins are now aqueducts rather than
reservoir
Nervous System Control of
Cardiovascular System
HEART
1. Heart Rate
Symp↑; Parasymp ↓
2. Strength of Heart contraction
Symp↑; Parasymp ↓
(Both 1 & 2 ↑ ↓ cardiac output – more/less flow)
Blood Vessels
1. Resistance in arterioles
Symp↑
(↑ Pressure & shunt blood away from some tissues & towards other tissues)
2. “Squeezing” of veins
Symp↑
(↑ cardiac output by ↑ effective blood volume by pushing more blood back to
heart)
Symp
also
innervates
arterioles
and veins
How does the brain monitor
Cardiovascular System Function?
• Pressure sensing neurons in the walls of the carotid
artery) monitor pressure in this blood vessel and
send signals to the brainstem which controls heart
and blood vessels
• There are other
pressure sensing
neurons in upper chest
(aortic arch) as well
• Key point - pressure is
measured in vessels
feeding the brain.
CV System Design