Cardiovascular System Part 3 - Heart Conductivity and Blood Vessels Flashcards
in order to contract our heart, we have a group called?
self-excitable cardiac muscle cells
- very specially designed so that they can initiate the signal to tell the heart muscle to contract
- they do not need the nervous system to tell them to do anything (self-excitable)
the first clump of the self-excitable cardiac muscle cells are found where?
at the sinoatrial (SA) node (right at the top near the right atrium, close to where the superior vena cava enters)
what is the SA node often referred to as?
the pacemaker of the heart
what is the SA node made of?
modified cardiac muscle cells that are capable of generating an electrical signal that causes heart contractions
the SA node in semi-controlled by?
the sympathetic and parasympathetic nervous system
what does the parasympathetic and sympathetic nervous system control in the SA node?
speeding up or slowing down the electrical signal of the heart beat
what generates the electrical signal of the SA node that controls the heart beating?
the SA node
how often does the SA node on its own send a signal for the heart to beat?
100 times in a minute at rest
the SA node on its own at rest produces 100bpm, however at rest, average is 70bpm. how is that?
there is a parasympathetic signal which travels down the vagus nerve to the SA node that slows it down from 100 to 70
what is it called when the parasympathetic nervous system calms down the SA node and its 100bpm?
vagal tone
what happens when we need our heart rate to increase?
the sympathetic nervous system is going to send then opposite signal as the parasympathetic through the vagus nerve to the SA node to increase the heart rate
what sends the original electrical signal of the heart beat all over the atria, causing it to contract and fill up the ventricle?
the SA node
once the signal is sent from the SA node, where does it go?
another clump of modified cardiac muscle cells on the floor of the right atrium called the atrioventricular (AV) node
what happens when the AV node picks up the signal from the SA node?
it transfers the signal down to the atrioventricular (AV) bundle (Bundle of His)
after the signal is given to the bundle of His, what happens?
the bundle splits to give right and left bundle branches
what happens to the right and left bundle branches?
they each branch around each of the ventricles into purkinje fibers
what do the purkinje fibers do?
deliver the signal throughout the ventricles and then a coordinated contraction happens at both of the ventricles and then the papillary muscles within the ventricle
what happens when blood leaves the heart?
it goes into very large arteries which is called elastic arteries
why are all the arteries that are closest to the heart very large?
because they have to handle a lot of blood at once
are arteries more elastic if they are closer to the heart or farther from the heart?
arteries are more elastic is there are closer to the heart because the pressure closer to the left ventricle is very high so they have to withstand the pressure of the huge force of blood coming into them
why do the arteries become smaller and smaller as we move further from the heart?
because there is so much branching and each one has less and less blood in it
- blood gets really spread out around the body
what are our muscular arteries?
our smaller arteries and have less elasticity than our elastic arteries
what are our arterioles?
our smallest artery
what is smaller than our arterioles?
our capillaries
what are all of our arteries called from largest to smallest?
largest: elastic artery
- muscular artery
- arteriole
- capillary
what are all of our veins called from smallest to largest?
smallest: capillary
- venule
- medium-sized vein
- large vein
where does gas exchange occur between the blood circulation and the cells of the body?
capillaries
how thin are capillary walls?
a single cell in width
what is allowed because of the very thin walls of arteries?
allows oxygen and nutrients to move out into the cells and carbon dioxide and waste products to move into the blood
what are capillaries typically organized into?
a capillary bed
how many main layers of the blood vessels are there (not capillaries)?
three
what is the innermost layer of the blood vessels (not capillaries)?
the tunica interna/intima
what is the middle layer of the blood vessels (not capillaries)?
tunica media (muscular layer)
what is the external layer of the blood vessels (not capillaries)?
tunica externa
what is the tunica interna made of?
simple squamous epithelial cells
does the tunica interna contain areolar connective tissue?
yes, only in the arteries and veins
is the tunica media thicker in arteries or veins?
arteries
what is the tunica media made of?
smooth muscle cells
in arteries and arterioles, what is the thickest layer of the wall?
the tunica media
why is the tunica media thicker on the arterial side?
because this is where we control blood distribution
- when we send blood where it is needed
- sympathetic signal will be sent to the tunica media to contract or dilate to supply blood where we need it
what happens when we vasoconstrict?
all the smooth muscle in the tunica media contracts and that will cause the lumen (inside of the artery) to become much smaller so less blood can get into all the the vessels
what is vasoconstriction?
when a sympathetic signal is sent to the tunica media and the smooth muscle contracts to make the diameter of the blood vessel smaller
what is it called when a sympathetic signal stops and the smooth muscle in the tunica media relaxes and the diameter opens back up?
vasodilation
does vasodilation happen because of the parasympathetic nervous system?
no
what is the tunica externa made mostly of?
areolar connective tissue
what is the purpose of the tunica externa?
its going to provide a little more solid structure to the blood vessels and help anchor the blood vessel to nearby structures so that they are not moving around
what is the thickest layer of a vein or venule?
tunica externa
how do we control blood flow in the veins?
we don’t. if a capillary has blood to send, the vein will take it
- all the decisions are made on the arterial side
where is the blood before it gets delivered to a cell?
arterial side
what are capillaries composed of?
- tunica interna
- basement membrane
- thin layer of simple squamous epithelial cells for gas exchange
are valves found in veins?
yes
- NOT always in venules
- NEVER in arteries
what is the purpose of the venous valves?
to help return the blood to the heart because veins cannot contract to push blood back to the heart
why cant veins contract?
because they do not have a lot of smooth muscle (very thin layer of tunica media)
- so they cannot contract to push blood back to the heart
what are the venous valves made up of?
tunica interna
how does the venous valves move the blood towards the heart?
once blood passes a valve, it will slosh and fill the cusps and then the valve will close. that prevents blood from going backwards. it only moves forward because they are one way valves
what is the #1 way that we keep venous blood moving towards the heart?
the one-way venous valves
what is the second way that we keep venous blood moving towards the heart?
through the massaging action of muscles
- called the musculovenous pump
any muscle contraction that occurs in the skeletal muscles near a vein will do what to the vein?
squish the vein which helps to push the blood back to the heart
- veins have very squashy walls because they do not have a lot of muscle
in what areas do we have the musculovenous pump?
lower limbs and diaphragm
what is the last push we need on the veins to get blood back into the heart?
the diaphragm contracting with every breath we take
