Week 8 - Study Guide Flashcards
What size is the heart?
Fist sized
What is the heart protected by and is double layered?
Pericardium - double sac
What are the two layers of the pericardium?
- Fibrous
- Serous
What is the function of the Fibrous layer of the pericardium?
- Limits overfilling to keep the heart successful in pumping.
(protects and prevents overfilling) - Fibrous CT helps protect the heart from outside sources of infection and irritation
- Protects the heart from overfilling
Under certain physiological conditions - you could have the risk of overstretching/overfilling.
If that happens to the heart - it will reduce the functionality of the pumping of the heart.
What is the function of the serous layer of the pericardium?
It has two layers itself
Serous Pericardium
fluid separates two more layers
in between the two layers is fluid that protects from friction.
2 layers are:
1. Parietal layer
2. Visceral layer
Parietal Layer of the Serous Pericardium
- This layer is more exterior
- Is attached to fibrous sac of the pericardium
Visceral Layer of the Serous Pericardium
AKA epicardium
Internal layer - on surface of the heart
Two layers of the Serous Pericardium
- Parietal
- Visceral
Pericardial Fluid
- Located between the 2 layers of Serous Pericardium.
- There has to be fluid in between the parietal and visceral layers in order to assist the normal movement of the heart.
- Heart is highly mobile organ
- Pumping blood all of the time
- Fills and empties repeatedly
Having two sticky layers (parietal & Visceral) of the membrane
1. the fluid is going to help the two layers slide past each other
2. to avoid friction
3. or inflammation
Pericarditis
- Inflammation, damage, injury, or infection of the pericardium
Negative impact associated with inflammation and infection of the pericardial layers.
That could be damaging because may build-up of fluids, irritations, inflammation on the heart is going to negatively impact its ability to act as an appropriate pump
Name the three layers of the heart:
- Epicardium
- Myocardium
- Endocardium
Epicardium
- The visceral layer of the serous pericardium
- Often fatty in the elderly
- Outer Layer
Myocardium
- muscular part of the heart (cardiac muscle)
- Connective Tissue
Why & where does the myocardium have variable thickness?
- Contractile muscle tissue in the heart - in the ventricles.
Variable thickness Where?
1. Atriums are not very thick
2. Right ventricle is a bit thicker
3. Left ventricle is very thick
Variable thickness WHY?
1. to allow for the pumping of the blood to all the various locations that it needs to go
2. needing different amounts of muscle strength to pump blood out to the lungs vs the systemic circuit
Endocardium
Blood vessels in body all have squamous epithelium and is connected to your heart.
Endocarditis
Inflammation in the heart (endocardium)
Possible causes of endocarditis
- contaminated needles which could cause an infection through the circulatory system - which could result in endocarditis
Endocarditis could lead to
- Valve damage
- emboli
Valve Damage
the pumping of the heart would be impaired
Emboli
could end up with traveling blood clots which could lodge in:
1. the heart - causing a heart attack
2. lungs - causing a pulmonary embolism and pulmonary edema
3. Brain - causing a stroke
Myocardium has a unique set of features within the ventricles:
Papillary Muscles
Function - to help hold the ventricular valves in place and keep them from inverting.
They hold the chordae tendineae which are attached to the AV valves and anchored by the papillary muscles to the myocardium.
Ensuring that the valves do not get pushed backwards into the atria as the ventricles contract
Heart Features
- Atria & Ventricles
- AV valves - tricuspid & bicuspid
- Semilunar valves - pulmonary & aortic
- Interatrial septum
- Atrioventricular Septa
- Interventricular septum
Another name for bicuspid valve
Mitral
How many cusps do the tricuspid have?
Right side = 3 cusps
How many cusps does the bicuspid (mitral) valve have?
Left side = 2 cusps
Names of the AV valves
- tricuspid valve
- bicuspid (mitral) valve
Names of the Semilunar Valves
- Pulmonary semilunar valve (to the lungs)
- Aortic semilunar valve (to the body)
Interatrial septum
a barrier, in between atriums
Atrioventricular septa
(outer heart)
between the atrium and ventricle
Interventricular septum
(inside heart)
in between the ventricles
Do the atrium and ventricles pump at the same time?
yes
Workings of Blood Flow
- Blood enters the right and left atrium at the same time. Because the heart pumps as a circuit.
- Then pushes through the tricuspid or bicuspid valve
- into the right or left ventricle
- The ventricles are filling up with blood
- Ventricles start to contract
- As that happens, it closes the tricuspid or bicuspid valve
- There is a period of intensifying contraction in the ventricle
- Allowing the ventricle to overcome the back pressure on the semilunar valve
- Helping to push blood out into the pulmonary trunk (pulmonary circuit) or Aorta (systemic circuit)
- Once the blood is pushed out of the ventricle –> the whole cycle starts again
Returning to the heart
Filling the Atria
Coronary Circulation -
Heart needs blood supply as well.
Blood cannot enter the heart directly
- Coronary arteries (for the heart) branch off of the Ascending Aorta.
- Deliver the nutrients/pick up waste
- Take the deoxygenated blood to the coronary sinus
- where it will go onto the right atrium to start the cycle again.
Coronary Circulation has. a special protective feature –
Anastomoses
aka - collateral circulation
A component of the circulation that allows blood flow to get to the tissues of the heart through alternate pathways.
These pathways develop slowly as we age
Which could help a person survive a heart attack later in life due to these back up routes to deliver blood to the heart tissue.
Cardiac muscle properties:
Muscle length
Short
Cardiac muscle properties:
Shape of muscle
Branching
Cardiac muscle properties:
What are the functions of these structures:
Intercalated Discs
Holds cells together at these branch points between one cella and the next cell.
In between cells
Connects opposing ends of cardiac muscle
Where the gap junctions are located
Cardiac muscle properties:
What are the functions of these structures:
Desmosomes
- Adhering junctions
- holding the cells together, ensuring the cells will not be pulled apart by contractile strength of the heart
Cardiac muscle properties:
What are the functions of these structures:
Gap Junctions
Ion connection
allowing electrical signaling to pass from one cell to the next cell quickly and efficiently.
Lots of electrical signaling
Cardiac muscle properties:
Do you expect many or few mitochondria?
~25% of cell volume is mitochondria
LOTS of mitochondria
Heart is expensive to run.
Requiring a lot of ATP production
- a constant supply of oxygen to keep the heart tissue pumping
Cardiac muscle properties:
What kinds of nutrients do you predict the heart can use?
Anything it can get to keep the heart pumping!
Very versatile
CHO
Protein
Lipids
Lactic Acid
Heart is made up of individual cells that are held together with
Intercalated discs
Each individual cell of the heart has
striations
the striping pattern
because of the pattern of actin and myosin
Cardiac cells tend to be wider because…
they are branching and interconnecting
Lengthwise, cardiac muscles tend to be relatively
short
Myogenic
- The source of the electrical conduction is internal –*MYOGENIC** originating from the heart tissue
- meaning that the signal that tells the heart to contract does not come from the CNS.
- The NS can influence the heart - Sympathetic & Parasymapthetic
- The actual baseline pace for the heart is internal - within the muscle itself - Myogenic
How does the AP of the cardiac muscle look different?
CARDIAC MUSCLES
1. Muscle origin
2. Small percentage of cells experience slow sodium leaking that cause the membranes to depolarize
3. Threshold - once it hots threshold, it sends an action potential
4. The leak rate of the sodium sets the rhythm (AVG 75 bpm)
Myogenic cells are the ones setting the heart rate
SKELETAL MUSCLE
1. Channels do not leak
Cardiac Muscle contraction
- Automaticity - self-exciting (~1% of all cardiac cells send all of the electrical signals in the heart telling all of the cells to get excited and contrast in unison)
- When one part of cells depolarizes it spreads that signal throughout. SO you can get atria contracting in unison and the ventricles contracting in unison .
- Gap junctions - allowing for the electrical signals to spread quickly
- Long refraction which prevents tetanic contraction
Meaning - when the heart contracts it stays contracted for a longer period of time, helping to ensure the muscle contraction never gets confused.
Refraction
When heart contracts - it stays contracted for a longer period of time - allowing for the ventricles to fill.
Fluid movement takes time
Contract and hold -
1. to ensure electrical signals and muscle contractions occur in the correct directionality - allowing blood to pump out
2. Ensures the blood does not start to flow backwards - because of lack of coordination
Skeletal Muscle contraction
- Stimulated by nerves associated within the CNS
- Do not excite each other
- Recruitment to fit the need/goal to what you are lifting (for example)
- Force = motor units (more force needed more motor units)
- Short refraction & contraction - once you contract the signal goes away and you can relax again
Sarcoplasmic Reticulum
Calcium delivery - to the heart muscle - allowing actin and myosin to interact.
Because the
1. calcium binds to tropin -
2. and pulls the tropomyosin out of the way -
3. so the myosin heads can grab onto the actin sites –
4. allowing the sliding filament
5. to allow a muscle contract to occur
Heart does have T-tubules but does not have…
Triads (terminal cisternae)
General Cardiac Cell Activity
- Depolarization - sodium influx
- Plateau phase - Calcium influx
- Repolarization - Efflux of Potassium
Which comes first?
The contraction or the electrical signal
Electrical signal
Cardiac Muscle Action Potential and Contraction is:
- Fast
- Sodium first
- Long calcium influx
- Potassium efflux - repolarization
What percent of cells do the electrical circuit in the heart that allow for muscle contraction?
1%
4 Major components of the electrical events of the heart
- SA node - Sinoatrial node
- AV node - Atrioventricular Node
- AV bundle - Atrioventricular bundle
- Purkinje fibers
All of the heart cells are
- noncontractile
(Autorhythmic ceclls)
What is the pacemaker?
SA Node - Sinoatrial Node
Top of right atrium
Another name for Atrioventricular Bundle (AV bundle)
Bundle of His
signal goes down
Purkinje Fibers
Bottom - up the signal travels
The Electrical signal circuit
- SA node - pacemaker - sends signal across the top of the atria - then it will hit a second node (AV node)
- AV node - signal pauses here so the atria can contract & eject blood to the ventricles
- Signal descends from AV node to the AV bundle (His) then
- goes up the side of the ventricles through the Purkinje fibers
Autorhythmic cells allow signal to
travel much faster than on their own.
6x faster (conduction) than normal heart muscle
Pacemaker potential
unstable resting potentials due to slow Na+ channels leaking that are associated with the SA node.
By having the slow leaking you never really sit at baseline
1. Threshold - Ca2+ channels open
2. AP = explosive Ca2+ influx produces the rising phase
3. Repolarization = inactivation of Ca2+ channels & opening of voltage-gated K+ channels
Pacemaker cell activity
- Slow Na+ leaks out (pacemaker potential)
- Calcium channels open (depolarization)
- Threshold
- K+ channels open and efflux (Repolarization)
what is avg heart rate
60-100.
(70-75)
Fast heart rate
Tachycardia
Slow heart rate
Bradycardia
Contraction of the heart (pumps out)
Systole
Relaxation phase of the heart (fills up)
Diastole
