Slide set 5- Chapter 14 the heart+ smooth muscle Flashcards
True or false the cardiac muscle tissue is only found in the heart
True
What is the other name given to the heart muscle tissue?
Striated involuntary muscle
What is one difference between the cardiac muscle and skeletal muscles CELLS?
- Unlike other muscles, the cardiac muscle fibers are branched and form junctions called INTERCALATED DISKS with adjacent cardiac muscle fibers
- Individual cells also exhibit branching
- Another adaptation for contraction is the LONGER RETENTION of CALCIUM in the SR: results in a long contraction
What is a ressemblance in structure of cells between cardiac muscles and skeletal muscle fibers?
The both have sarcoplasmic reticula and T tubules
BUT these structures are not as highly organized as in skeletal muscle fibers
How contraction of cardiac muscle could be described?
Cardiac muscle fibers form a CONTINUOUS, CONTRACTILE band around the heart chambers that conducts a SINGLE IMPULSE across a virtually continuous sarcolemma
What is a difference in T tubule of cardiac muscle with other muscles?
T tubules are LARGER and form DIADS with a rather SPARSE sarcoplasmic reticulum
- Cardiac muscle sustains EACH IMPULSE LONGER than in skeletal muscle
- Cardiac muscle DOESN’T RUN LOW on ATP, and DOESN’T EXPERIENCE FATIGUE
- Cardiac muscle is SELF-STIMULATING
What is the difference between a smooth muscle cell and a skeletal muscle cell?
- Smooth muscle is composed of small, tapered cells with SINGLE NUCLEI
- No T-tubules are present, and only a LOOSELY ORGANIZED SARCOPLASMIC RETICULUM is present
- Ca++ comes from outside the cell and binds to CALMODULIN INSTEAD OF TROPONIN to trigger contraction
- NO STRIATIONS, because thick and thin myofilaments are arranged differently than in skeletal or cardiac muscle fibers: MYOFILAMENTS ARE NOT ORGANIZED INTO SARCOMERES
What happens during contraction of a smooth muscle cell?
- Sliding of the myofilaments causes the fiber to shorten by “balling up”.
- The micrograph shows that the fiber becomes shorter and thicker and exhibits “dimples” where the myofilament bundles are pulling on the plasma membrane
What are the 2 types of smooth muscle tissue?
- Single-unit (visceral)
- Multiunit
What are characteristics of single-unit (visceral) smooth muscle tissue?
- Gap junctions join smoth muscle fibers into large, continuous sheets
- MOST COMMON TYPE, forms a musclular layer in the walls of hollow structures such as the DIGESTIVE, URINARY, REPRODUCTIVE TRACT
- Exhibits AUTORYTHMICITY, producing PERISTALSIS
What are characteristics of multiunit smooth muscle tissue?
- DOESN’T REACT AS A SINGLE UNIT, but is composed of many independant cell units
- Each fiber responds only to nervous input
What is the difference in impulse between single-unit and multiunit smooth muscle?
- Single-unit: Neurotransmitters released from the nerve fiber trigger impulses in SMOOTH MUSCLE MEMBRANE, an event is TRANSMITTED to ADJACENT MUSCLE FIBER THROUGH GAP JUNCTIONS
- Multiunit: EACH FIBER is triggered INDEPENDANTLY by nerve stimulation
SMOOTH MUSCLE CONTRACTION STEPS
Aller voir schéma et réécrire/déssiner (slide 37 )
RELAXATION IN SMOOTH MUSCLE STEPS
Aller voir schéma et réécrire/déssiner (slide 38)
What is the difference in time of contraction of smooth muscle vs cardiac and skeletal muscle?
Smooth muscle contraction is much longer (5 seconds! )
Shorter is skeletal (less than 1 sec) , after cardiac (1 sec) , than smooth
What are the 6 major groups of smooth muscle?
Vascular, gastrointestinal, urinary, respiratory, reproductive and eye
True or false, smooth muscle can only be stimulated by neurotransmitters?
False, they can be controlled by hormones, paracrines and neurotransmitter
True or false, smooth muscle have in general the same electrical response?
FALSE =>
Variable electrical responses, multiple pathways influence contraction and relaxation
FAIRE UN TABLEAU QUI COMPARE SMOOTH AND SKELETAL MUSCLE
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Was is particular with smooth muscle cells concerning calcium?
Smooth muscle cells contain stretch activated calcium channels:
- Open when pressure or other force distorts cell membrane
- Known as MYOGENIC CONTRACTION
What are 2 substances entering the body, and where do they go?
-OXYGEN: Lungs => all cells
- NUTRIENTS AND WATER:
Intestinal tract => all cells
What material is moved from cell to cell?
- Wastes
- Immune cells, anti-bodies, clotting prots
- Hormones
- Stored nutrients
What is some material leaving the body, and by what organ are they leaving?
- Metabolic waste => kidneys
- Heat => Skin
- Carbon dioxide (CO2) => Lungs
Of what structure is the heart mostly composed?
MYOCARDIUM
- Thickest middle layer of the heart wall
Where does blood enter, and where does it come out?
Enters the right atrium, and qui the heart by the left ventricule
True or false, when blood is returning to the heart b the superior or inferior vena cava, it is at the highest pressure.
False, it is a the lowest pressure
True or false, the blood carried by arteries that quits to heart is always oxygenated
False! The blood carried by the left and right pulmonary arteries is deoxygenated, since it goes to the lungs to come back to the heart oxygenated
True or false, blood that is carried to the heart is done by veins
True! Blood coming to heart=> veins, blood going out=> arteries
Describe the one way flow of the blood in the heart
Blood comes in by right inferior or superior vena cava and enters the RIGHT ATRIUM. It enters the RIGHT VENTRICULE. Goes up in the left and right pulmonary arteries and quits the heart (blood is still deoxygenated). Blood comes back oxygenated, enters the LEFT PULMONARY VEINS, goes down the LEFT ATRIUM , to LEFT VENTRICULE , and quits the heart by the AORTA”
What is particular about portal systems?
Portal systems allow nutrients, things to be transmitted without being lost and released out in the rest of the circulation.
What are the 2 circulation systems?
- Pulmonary circulation
- Systemic circulation
The pulmonary circulation is a ___ ( low or hight) pressure ___ ( low or hight) resistance system.
The pulmonary circulation is a LOW pressure LOW resistance system - ALL the blood flows through the lungs
The systemic circulation is ____ ( low or hight) pressure and ____ (low or hight) resistance circulation.
The pulmonary circulation is a HIGHT pressure HIGHT resistance system
- High pressure so blood can go around and oppose the resistance system of blood flow (resistance= narrow blood vessels )
- if you need to reduce pressure, reduce constriction of blood vessels
By pressure and resistance, what do we mean?
Pressure: the force exerted on the vessel walls
Resistance: the opposition to blood flow
When the blood is highly oxygenated (in the systemic circulation), the pressure is ___-
High
Highest amount of oxygen= highest pressure
What causes peripheral resistance?
Resistance to blood flow is imposed by the force of friction between blood and walls of its vessels
What are factors that can influence peripheral resistance?
- Blood viscosity
- Diameter of arterioles
=>Vasomotor mechanism
How can blood viscosity vary?
- High plasma prots concentration can slightly increase blood viscosity
- High HEMATOCRIT (% of RBCs) can increase blood viscosity
- Anemia, hemorrhage, or other abnormal conditions may also alter blood viscosity
What allows arterioles to constrict or dilate?
Muscular coat of arterioles
True or false, decreased resistance decreased arteriole runoff leads to lower arteriole pressure.
FALSE .
INCREASED resistance, DECREASED arteriole runoff, leads to HIGHER arterial pressure
Explain the case of a dehydrated marathon runner, how his blood pressure can be affected , and what the body does to compensate
If the marathon runner is dehydrated, he/she will have low blood pressure. The body will respond by making heart beat faster and by vasoconstriction.
Which side of the heart performs more work?
Left side performs more work, as it pumps into a longer high resistance system
What part of the heart is responsible for the unidirectional blood flow in the heart?
The 4 one-way valves
What are the 2 valves between the atrium and the valve?
Right and left AV (Atrioventricular) valves.
What are the 2 other valves (not AV valves), and where are they located in the heart?
AORTIC and PULMONARY valves are located at the junction where the major arteries leave the ventricles.
Which valves are bicuspid or tricuspid?
Bicuspid: Left AV valve
Tricuspid: Right AV valve, aortic valve, pulmonary valve
When are the valves from the heart forced open?
Forced open when the LEFT AND RIGHT VENTRICULAR pressure EXCEED the pressure in the AORTA and PULMONARY ARTERY
When are the valves from the heart forced close?
Closure results when pressure in the VENTRICLES falls BELOW the AORTIC and PULMONARY PRESSURE
- Closure prevents backflow
What are the 3 layers of the heart?
- Endocardium ( inner layer of epithelium)
- Myocardium (middle layer of cardiac muscle tissue)
- Epicardium (external membrane)
True or false, in the heart, you have connective tissue, epithelial tissue and muscle.
True!
What are the 2 specialized type of cardiac muscle cells?
- Contractile cells (99% of the cardiac muscle cells)
- Autorhythmic cells
What is the role of the contractile cells of the cardiac muscle? What % of the cardiac muscle cells do they represent?
They do the pumping but do not initiate their own action potentials.
Represent 99% of the cardiac muscle cells
What is the role of the Autorhythmic cells ? Do these cells contract?
They are specialized for initiating the conduction of the action potentials responsible for contraction of the working cells.
These cells DO NOT contract
True or false, the heart needs external nerves to create its action potential.
FALSE
The heart creates its own action potential by using autorhythmic cells
What are the 4 major structures that compose the conduction system of the heart?
- Sinoatrial node (SA node)=> pacemaker of the heart
- Atrioventricular node (AV node)
- AV bundle (Bundle of His)
- Purkinje system
True or false, the 4 major structures that compose the conduction system of the heart ALSO participate in contraction
FALSE
These structures contain specialized cells for conduction of AP, but NOT contraction.
What node in the heart is the most important? What is its role?
The SA node (pacemaker) in the atrial wall.
It initiates each heartbeat and sets its pace.
Specialized pacemaker cells in the node possess an intrinsic rhythm.
In a normal case, how would conduction of AP happen between nodes?
What would happen in an abnormal case?
SA node gives AP of 70 mph, and will be the fastest autorhyhtmic tissue, and set the heart rate.
In an abnormal case, the next fastest tissue autorhythmic tissue , the AV node, qill set the heart rate (50mph)
What are the 3 criteria of AP spread for coordinated and efficient pumping?
- Atrial excitation and contraction must be COMPLETE before the onset of ventricle contraction => allows complete ventricle filling
- Excitation of cardiac muscle fibers must be COORDINATED to ensure that each heart chamber contract as a unit to pump all the blood out
- The pair of atria and ventricules must CONTRACT TOGETHER to permit SYNCHRONIZED PUMPING of blood into the pulmonary and systemic circulation
How is the depolarization of the autorhythmic cells spread to adjacent contractile cells?
It can spread through gap junctions
Aller voir la slide 67 pour toutes la conduction bien expliquée
go
Describe the steps of electrical conduction in parallel with contraction.
- SA node creates a depolarization. Impulse will travel through the muscle fibers of both atria, and the atria will begin to contract.
- The AP enters the AV node. Conductions slows to allow complete contraction of both atria chambers.
- After the AV node, conduction velocity increases as the impulse is relayed through the AV bundle into ventricles.
- Right and left branches of bundle fibers and PURKINJE fibers conduct the impulses throughout the muscle of BOTH VENTRICLES. Stimulates contraction of ventricles.
True or false, cardiac autorhythmic cells have a resting potential
FALSE
Unlike nerve and skeletal muscle cells in which the membrane remains at constant resting potential unless the cell is stimulated, Cardiac ARC cells DO NOT have a RESTING POTENTIAL
What do ARC have instead of a resting potential?
They display pacemaker activity
What ions are involved in cardiac muscle contraction?
Ca 2+, Na + and K+
What is the main difference in ion movement between skeletal and cardiac muscles?
Change in potassium permeability. Depolarization is mainly caused by decreased permeability to potassium, and increase permeability to calcium out / in the cell.
What joins individual cardiac muscle cells?
Intercalated disks
What are the 2 types of connection within the intercalated disks?
Desmosomes and gap junctions
How can impulse spread and pass the gap junctions?
Gap junctions are areas of LOW ELECTRICAL RESISTANCE, and allow electrical impulses to spread from one cardiac cell to the next
What does syncytium mean?
More than one nuclei in a cell…
True or false, the ionic mechanism of the cardiac contractile cells is the same as the one from the AR cells
FALSE
ionic mechanism is not the same
True or false, there is a resting potential in contractile cells
TRUE
The resting potential is at -90mV
How is the threshold reached to create impulse in contractile cells?
Threshold is reached by result of activation of gated Na+ channels (same as other cells…)
What is different with the plateau phase of contractile muscle cells and plateau phase of other cells? And why?
Plateau phase is prolonged.
- The plateau phase is maintained bu ACTIVATION of Ca+ channes and DRECREASE in K+ permeability
- There is a slow inward movement of Ca because Ca+ is greater in the ECF which favors its movement into the cell
- the reduction in movement of K+ out of the cell also maintains the membrane positivity and thus, prolongs the AP-plateau
SEE slide 74 and DESSINE LE SCHEMA
Why is there a longer plateau, and resting potential in cardiac muscle cells?
Because heart needs alternate periods of contraction and filling! Has to totally fill, and totally empty! This is why coordinated and prolonged contraction! (not as long as smooth muscle … but still longer than skeletal muscle)
What other type of muscle cells have a prolonged plateau phase?
Smooth muscle cells
What are some factors that affect heart rate?
Para and sympathethic nervous system bring their effects on the heart by altering activity of the cAMP second messenger system in the innervated cardiac muscle cells.
What is the parasympathetic nerve to the heart? What part does it affect?
The VAGUS nerve. Primarily affects the ATRIUM and SA an AV NODES
What is the effect of VAGUS nerve of parasympathetic control?
DECREASE heart rate -> inhibitory
- By releasing AcH which increases permability to potassium channes, which has a hyperpolarization effect
- ACts on BV (?) to have a vasodilation effect
What is the effect of sympathethic control of heart rate?
- Controls heart rate in emergency response => when need of greater blood flow
- Stimulates SA node by releasing NOREPINEPHRINE by accelerating inactivation of K+ channes- less able to leave the cell
- Cells becomes less negative (K+ stays in…)
- Swift drift to AP
- Heart beats more forcefully and squeezes more blood out
- VASOCONSTRICTION EFFECT ON BLOOD VESSELS
What is the name of receptors that are sensitive to changes in pressure? where are they located?
Baroreceptors
Located in two places in the heart (AORTA and CAROTID SINUS)
What is the role of the baroreceptors of the heart?
- Coordinate with the integrators in the cardiac control centers in negative feedback loops to oppose changes in blood pressure by adjusting the heart rate.
Go check slide 82 and reexplain it
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