Transcript File - Mr. Graff`s Science Room

The circulatory system - Part 2 Let's fill in the details!
1) A few more details about the heart...
Septum
The wall dividing the heart in two, separating
the right atrium and ventricle from the left
atrium and ventricle
Heart valves
There are valves in the heart that prevent blood from flowing
backwards
There are 2 atrioventricular (AV) valves - these separate the atria
and ventricles
-One in between the left atrium and left ventricle, and the other
in between the right atrium and right ventricle
-There are 2 semilunar valves - these separate the ventricles and
the arteries
-One in between the left ventricle and the aorta, the other in
between the right ventricle and the pulmonary artery
Bicuspid valve =
left AV valve
Tricuspid valve =
right AV valve
Heart valves
The lubb dubb sound of your heart beat is caused by valves
closing
Lubb - AV valve closes
Dubb - semilunar valve closes
Other sounds?
Heart murmur -when blood in the heart flows back from a
ventricle to an atrium
-caused by AV valves not closing properly
Some dark humor…
Note: Mr. Graff does not support domestic violence
Coronary arteries
The heart has special coronary arteries. The heart, just like every
other organ, requires oxygen. Coronary arteries provide the
heart with oxygenated blood. Yes, the heart pumps blood to
itself.
Tempo of the heart
There are special tissues in the heart that set the tempo that the
heart beats at
-The sinoatrial (SA) node - is the primary pacemaker of the
heart. It sends nerve signals to the atrioventricular (AV) node
-The AV node sends signals to Purkinje fibres
-Purkinje fibres - send nerve impulses throughout heart, so the
heart beats synchronously
Signals are sent from the brain to the SA node to speed up or
slow down the heart
Animation:
https://en.wikipedia.org/wiki/File:ECG_Principle_fast.gif
2) Blood pressure
The beating of the heart can be described in two ways
Systole - when the heart contracts, pushing blood out
Diastole - when the heart relaxes, allowing the atria to fill with
blood
Systolic blood pressure - how much pressure the blood is under
when the heart contracts
Diastolic blood pressure - how much pressure the blood is under
when the heart relaxes
Normal systolic blood
pressure is 120 mmHg,
normal diastolic blood
pressure is 80 mmHg
(written 120/80)
Hypertension - high blood
pressure, caused by more
resistance to the flow of
blood
Arteries are always under
much higher blood
pressure than veins
3) A few more details on blood vessels...
Arteries
Have thick walls to accommodate
the high blood pressure they face
Arteries expand following a heart
contraction (systole) then recoil
back
Veins
Since veins are under very low
blood pressure, they rely on
skeletal muscles to push the blood
back to the heart
There are also valves in veins that
prevent blood from flowing
backwards
Diagrams of veins
Selectivity
Blood cannot be pumped to all
areas of the body at once
Vasoconstriction - When the body
selectively constricts certain blood
vessels to encourage blood to flow
elsewhere
For example, when stressed the
blood vessels leading to the
kidney, stomach and intestines
constrict, so blood is sent to
muscles, brain, heart instead
Similarly, the body can expand
certain blood vessels to encourage
the flow of blood
Health Problems
Atherosclerosis - accumulation of
fat deposits on the walls of the
artery
These fat deposits can get so big it
bursts through the artery
These fat deposits also narrow the
arteries. If coronary arteries have
extensive fat deposits, a heart
attack can occur
Aneurysm - bulge that forms in the
wall of a weakened blood vessel
(often due to atherosclerosis).
Eventually the bulge ruptures.
Cells around the bulge don't get
blood and therefore die of oxygen
starvation
4) Thermoregulation
When the body is too hot, the skin starts sweating. This makes the skin
colder than the rest of the body.
Blood vessels near the skin expand, so more blood goes to the skin.
This cools off the blood. When the blood returns to the body, it helps
cool off your core
Similarly, when the body is cold, blood vessels near skin constrict,
limiting blood flow, so blood doesn't lose heat to the environment (so
your core stays warm)
5) Lymphatic system
-Small amounts of protein leak from capillaries into tissue space
-The lymphatic system allows these proteins to be recycled
-Lymph - the fluid that the lymphatic system transports
-The lymphatic system is a series of open-ended vessels that are
similar to veins; muscles push the lymph through the vessels, and
various valves prevent backflow
-Eventually the lymph rejoins the blood at the subclavian veins