Slide set 5 Flashcards
Muscle cell is
Muscle fiber
Cell membrane in muscle is
Sarcolemma
Cytoplasm in muscle is
Sarcoplasm
Modified ER in muscle is
Sarcoplasmic reticulum
Skeletal muscles are usually attached to
Bones and tendons
What are flexor and extensor
Flexor muscles- brings bones together
Extensor- moves bones away
Antagonistic pair: flexor-extensor pair
Properties of skeletal muscles and their function
Responsible for moving the framework of the body
•Can contract rapidly but tires easily
•Remarkably adaptable
•Function: Maintain posture and body position
•Movement of the body as a whole or of its parts
•Stablilizejoints
•Heat production
•Contract only in response to a signal from a motor neuron
Skeletal muscles are surrounded by ___, muscles divide into ___, where you can find individual muscle fibers
Connective tissue
Muscle fascicle
What are epi,peri and endomysium
Epimysium—coarse sheath covering the muscle as a whole
–Perimysium—tough connective tissue binding together fascicles
–Endomysium—connective tissue membrane that covers skeletal muscle fibers
–These three fibrous components are continuous with eachother and with the tendon
Characteristic of muscle fibers to movement
Excitability—ability to be stimulated
Contractility—ability to contract, or shorten, and produce body movement
Extensibility—ability to extend, or stretch, allowing muscles to return to their resting length
What is the role of SR in muscle
Plays a role in Ca+regulation during contraction
What are T tubules
extend across the cell. They are formed from inward extension of the sarcolemma.
–T-tubules chief function is to allow electrical signals traveling along the sarcolemma to move deeper into the cell
–Requirement for contraction
What is the triad
formed from a triplet of tubules made of the sacroplasmic reticulum which surrounds the T-tubule
–This arrangement allows a signal traveling along the T-tubule to stimulate adjacent membranes on the SR
Muscle fibers contain many ____
Mitochondira and multiple nuclei
What is sacromere
Segment of myofibril between two successive Z lines
•Each myofibril consists of many sarcomeres
•Contractile unit of muscle fibers
Sacromerers are a part of
Myofibril
Z lines function
an anchor for the myofibrils
Muscle fibers are made up of smaller units ___, which are made up from _____ that can be thick and thin. Thick is made up from ____ and the thin from ____
Myofibrils, myofilaments, myacin, actin
The bands of sacromere that are made only of thin microfilaments are ___ and thick microfilaments are ___
I band
H zone
What is A band
Where there is an overlap of thick filaments and thin filaments + H zone
Sacroplasm contains
SR
Myofibrils
Mitochodnria
Glycogen granules (energy)
Thin filaments in addition to actin are made up from
troponin
tropomyosin
What microfilamants play regulational role on muscle contraction
Titin
Nebulin
Thick myosin filaments do not attach to ___
Z lines
What are myosin heads
Very important during muscle contraction to create “bridges”
Actin is
globular protein that forms two fibrous strands that twist around each other to form bulk of thin filament
tropomyosin and troponin are
Tropomyosin—protein that blocks the active sites on actin molecules
•Troponin—protein that holds tropomyosin molecules in place
Thin filaments attach to both ___
Z lines
nebulin helps to align
Actin
titin provides
Elasticity and stabalizes myosin
Phase 1 of muscle contraction is
Motor neuron stimulates muscle fiber
Action Potential arrives at axon terminal at neuromuscular junction
Ach released; binds to receptors on sarcolemma
Ion permeability of sarcolemma changes
Local change in membrane voltage (depolarization) occurs
Local depolarization (end plate potential) ignites AP in sarcolemma
Phase 2 of muscle contraction
Excitation-contraction coupling occurs
Action Potential travels across the entire sarcolemma
AP travels along T-tubules
Sarcoplasmic Reticulum releases Ca2+; Ca2+ binds troponin; myosin-binding sites (active sites) on actin exposed
Myosin heads bind to actin; contraction begins
The binding of the mysoin head triggers ATP hydrolysis to ADP and phosphate. Energy of broken bond transferred to the mysoin
•D-the release of stored energy provides the force needed for the head to move back to its original position
What two receptors are involved in sending the signal from T tubule to SR
DHP- dihydropyridine L-type calcium channel
RyR- ryanodine receptor-channel
How signal is transferred from T tubule to SR
Depolarization will cause RyR to open through DHP and it will cause Ca ions to leave SR into cytoplasm and bind to troponin to allow actin-myosin binding
usually what is the position of actin filaments constituents
The troponin complex (Yellow) on the actin filament is positioned so that the threadlike tropomyosin (purple) is blocking the active site on the actin (pink) located underneath it.
what is essential movement for muscle contraction
The myosin heads bend with a strong force when they bind the actin filaments
•This pulls the thin filaments past them
•Each head then release and this pulls again
In what direction pulling of myosin happens
As the myosin heads pull on the thin filaments, the Z lines (Z disks) get closer together—thus shortening the sarcomere.
What happens after the contraction
Immediately after Ca++ions are released, sarcoplasmic reticulum begins actively pumping them back into sacs
•Ca++ions are removed from troponin molecules on thin filament, shutting down contraction
What happens in muscle when they are at rest ( energy)
ATP from metabolism is used to make phosphocreatine from creatine
Muscle store very limited reserves of ATP, so what is the way out
They have phosphocreatine, which is hydrolyzed to creatine and ATP when muscles work, providing quick energy
ATP in muscles are needed for
Myosin ATPase (contraction)
Ca-ATPase (relaxation)
Na-K-ATPase(restores ions that cross cell membrane during action potential to their original compartments)
Type of muscle fibers
Slow-twitch fibers (type I or ST)
Fast twitch oxidative-glycolytic fibers(FOG or type IIA)
Fast-twitch glycolytic fibers (FG or type IIB):
Characteristics of slow-twitch muscles
Use oxidative phosphorylation (have more mitochondria)
-Appear red due to myoglobin ( red oxygen-binding pigment) -> legs
describe fast-twitch muscles
develop tension 2-3x faster than slow
-Pump Ca2+ into SR faster
•Fast twitch oxidative-glycolytic fibers(FOG or type IIA)
- Use oxidative phosphorylation (have more mitochondria
- Appear red due to myoglobin
Fast-twitch glycolytic fibers -eyes (FG or type IIB): rely on anaerobic glycolysis to produce ATP
- Leads to high H+ (acidosis), because of lactate
- Fatigue more easily
- Appear white (lower myoglobin)
- Larger in size
- Fewer blood vessels
- More likely to run out of oxygen after repeated contractions
- In sports like sprinting
Cardiac muscle properties
- Striated
- Branched, have T tubules that are larger than in skeletal and forms diads with and sparse (редкий) SR
- They are held together by intercalated disks that have gap junction, that allow for cytopalsmic connection-> contraction as a unit
- Does not taper like muscle fiber (waste)
What type of muscle is cardiac
Striated involuntary
Difference of cardiac muscle vs skeletal in work
Cardiac muscle sustains each impulse longer than in skeletal muscle
•Cardiac muscle does not run low on ATP and does not experience fatigue (more mitochondria)
•Cardiac muscle is self-stimulating
Smooth muscle characteristics
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 (regulatory protein) instead of troponinto trigger a 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 to smooth muscle when it contracts
During contraction, sliding of the myofilaments causes the fiber to shorten by “balling up.”
Two types of smooth muscle
Single-unit
Multiunit
Characteristics of single-unit smooth muscle
Gap junctionsjoin smooth muscle fibers into large, continuous sheets
–Most common type; forms a muscular layer in the walls of hollow structures such as the digestive, urinary, and reproductive tracts
–Exhibits autorhythmicity, producing peristalsis
Characteristics of multiunit smooth muscle
Does not act as a single unitbut is composed of many independent cell units
–Each fiber responds only to nervous input
What causes release of Ca ions from SR in smooth muscle
Influx of Ca from exta cellular fluid
What happens in smooth muscles after influx of Ca into the cell
Ca binds to calmodulin ( ca modular protein)->
Which converts inactive myosin light chain kinase into an active form of (MLCK)
MLCK activates myosin ATPase by phosphorylaating it
Active myosin crossbridges slide along actin and create muscle tension
Describe relaxation of the muscle
1) Free Ca2+in cytosol decreases when
Ca2+is pumped out of the cell or
back into the sarcoplasmic reticulum (energy dependent)
2) ca unbinds from calmodulin
3) no activation of myosin atpase
4) decreased muscle tension
How fast each muscle tissue reacts to the signal and how long it holds the tension
Skeletal and cardiac muscles within a second (respond and contracts and stop the tension)
When smooth muscle’s peak contracting is after 3 sec and it hold it until 5 sec
Smooth muscles are subdivided into 6 groups
vascular, gastrointestinal, urinary, respiratory, reproductive and eye
Smooth muscles are controlled by ___
Hormones,paracrines, and neurotransmitters
physical characteristics of smooth muscles
Much smaller than skeletal muscle fibers •Has longer actin and myosin filaments •Myosin light chain plays regulatory role •Not arranged in sarcomeres •Has less sarcoplasmic reticulum
What can cause the opening of the receptors on the sarcoplasm in smooth muscles
Signal ligands
Depolarization or stretch (open when pressure or other force distorts cell membrane-MYOGENIC contraction)
What can cause a liberation of Ca from SR as the response of binding a ligand to the receptor
IP3 ( GPCR)
Heart is situated in
The thoracic cavity between lungs ( in mediastinum)
Heart is covered with
the pericardium a tough white fibrous tissue that is lined with moist serous membrane.
4 chambers of the heart and their function
The atriaare the two upper chambers. They receive blood returning to the heart from systemic veins (right atrium) and the pulmonary veins (left atrium).
–Atria transfer blood to the ventricles.
–The ventriclesare the two lower chambers. They pump blood out of the heart
Interventricular septum separates
Interventricular septum separates the low-oxygen blood on the right side of the heart from the high-oxygen blood on the left side
Two blood circuits
Pulmonary and systemic
What part of the heart is pointing to the left
Apex
The major blood vessel is __
Aorta
3 different layers in the heart
–The endocardium is the inner layer of epithelium.
–The myocardium is the middle layer of cardiac muscle tissue.
–The epicardium is the external membrane
Heart is mostly composed of ___ (type of layer)
Myocardium
Within pericardium there is
fluid
What is the name of the vein that brings blood to the right atrium
Superior vena cava
What artery is going from right ventricle and what blood is there
Pulmonary and vein
What separates atrium from ventricle
Cusp of a right AV(tricuspid) valve (right side)
Cusp of the AV(bicuspid) valve (left side)
The name of the valve closing the pulmonary artery
Pulmonary semilunar valve
What is holding valves between atriums and ventrilces connected to the heart
Chordae tendineae. It prevents the valves from being everted
Pressure in pulmonary and systemic circulation
The pulmonary circulation is a low pressure low resistance system-all the blood flows through the lungs
•The systemic circulation is a high pressure high resistance circulation
What vessel brings blood from lungs
Pulmonary veins ( oxygenated blood)
What is peripheral resistance
resistance to blood flow imposed by the force of friction between blood and the walls of its vessels
Factors that influence blood viscosity
Blood viscosity—the thickness of blood as a fluid
–High plasma protein concentration can slightly increase blood viscosity
–High hematocrit (% RBCs) can increase blood viscosity
–Anemia, hemorrhage, or other abnormal conditions may also alter blood viscosity
-Diameter of arterioles
What is vasomotor mechanism
muscles in walls of arteriole may constrict (vasoconstriction) or dilate (vasodilation), thus changing diameter of arteriole
–Small changes in blood vessel diameter cause large changes in resistance, making the vasomotor mechanism ideal for regulating blood pressure and blood flow
Determinants of blood pressure
Muscular layer of arterioles allows them to constrict or dilate and change the amount of resistance to blood flow
•Peripheral resistance helps determine arterial pressure by controlling the amount of blood that runs from the arteries to the arterioles. Increased resistance, decreased arteriole runoff leads to higher arterial pressure
–Can occur locally (in one organ); or the total peripheral resistance (TPR) may increase, thus generally raising systemic arterial pressure
Chordae tendinae are hold by
Papillary muscle
Aorta is closed by
Aortic semilunar valve
Steps in blood flow when heart contracts
- As ventricles fill, atrioventricular valve flaps hang limply into ventricules
- Atria contract, forcing additional blood into ventricles
- Ventricle contract , forcing blood against atrioventricular valve cusps
- Atrioventricular valves close
- papillary muscles contract and chordae tendineae tighten preventing valve flaps from everting into atria
What causes semilunar valves to open and close
These are forced open when the left and right ventricular pressure exceed the pressure in the aortaand the pulmonary arteryduring ventricular contraction and emptying.
- Closure results when pressure in the ventricle falls below the aortic and pulmonary pressure.
- Closure prevents backflow of blood
Two specialized types of cardiac muscle cells and their function
- Contractile cellswhich are 99% of the cardiac muscle cells-these do the pumping but do not initiate their own action potentials
- Autorhythmic cells–specialized for initiating and conducting the action potentials responsible for contraction of the working cells. These cell do not contract
Four of the major structures that compose the conduction system of the heart and contain specialized cells for conduction of AP but not contraction:
Sinoatrialnode (SA node) •Atrioventricularnode (AV node) •AV bundle (bundle of His) •Right and left bundle branches •Purkinje system
Conduction system structures are more ___ than ordinary cardiac muscle tissue and permit _____
highly specialized
only rapid conduction of an action potential through the heart
Who sets the pace of the heartbeat
SA node (sinoatrial)
If something goes wrong with SA nose, who is setting the pace
AV node , because it is the second quickest
What abnormal can happen to Purkinje fiber
Occasionally an area of the heart such as the Purkinje fibers becomes overly excitable and depolarizes faster than the SA-ectopic focus
This overexcitation can occur as a result of heart disease, anxiety, lack of sleep, caffeine, or excess nicotine or caffeine
SA node is located in
Right atrium
Three criteria for coordinated and efficient pumping
Atrial excitation and contraction must be complete before the onset of ventricle contraction-this allows for complete ventricle filling
–Excitation of cardiac muscle fibers must be coordinated to ensure that each heart chamber contracts as a unit to pump all the blood out-basting stick if poke randomly not much water will be squeezed out.
–The pair of atria and ventricles must contract together to permit synchronized pumping of blood into the pulmonary and systemic circulation.
How the signal is spread across the heart
After being generated by the SA node, each impulse travels throughout the muscle fibers of both atria, and the atria begin to contract
- As the action potential enters the AV node from the right atrium, its conduction slows to allow complete contraction of both atrial chambers before the impulse reaches the ventricles- > AV node delay
- After the AV node, conduction velocity increases as the impulse is relayed through the AV bundle into the ventricles
- Right and left branches of the bundle fibers and Purkinje fibers conduct the impulses throughout the muscles of both ventricles, stimulating them to contract almost simultaneously
What is the reason of the bundle of his
it transmits impulses from the atrioventricular node, located at the inferior end of the interatrial septum, to the ventricles of the heart.
Cardiac autorhythmic cells so not have _____, but it is said that they have ____
A resting potential
Pacemaker activity- their membrane potential slowly depolarizes or can be thought of to drift between action potentials until threshold is reached
How the membrane potential slow drift to threshold in pacemaker cells in heart
•The membrane potential’s slow drift to threshold is caused by a cyclical decreasein passive outward flux of K+ and a constant inward leak of Na+ and inward Ca2+
What is minimum voltage level for pacemaker cells
-60 mv
Within the intercalated discs there are two types of junctions ___
desmosomes and gap junctions.
What is a cardiac syncytium
The cardiac syncytium is a network of cardiomyocytes connected to each other by intercalated discs that enable the rapid transmission of electrical impulses through the network, enabling the syncytium to act in a coordinated contraction of the myocardium.
Atria and ventricles form separate ___
Functional syncytium
The action potential of cardiac contractile cells - pathway
Increased permeability of Na ions(fast)-peak of the action
permeability to Na decreases, as well as for K, but permeability to Ca in slowly increases and this causes a decrease of action potential, but looks like plateau. Then Permeability to Ca decreases, and K ions rush out fast bringing back the potential to - 90
The action potential of the cardiac contractile cells is initiated by ___
The nodal pacemaker cells
Threshold for ARC and contractile cells
ARC- -40
Contractile- -70
There is a ___ phase in contractile cells potential
plateau
What is the purpose of plateau phase in action potential
Do not have a sustained muscular contraction, to maximize the capability to pump blood
Excitation-contraction coupling and relaxation in cardiac muscle
- Action potential enters from adjacent cell
- Voltage-gated Ca2+channels open. Ca2+enters cell.
- Ca2+induces Ca2+releasethrough ryanodinereceptor-channels (RyR).
- Local release causesCa2+spark.
- Summed Ca2+sparkscreate a Ca2+signal
- Ca2+ions bind to troponin to initiate contraction.
- Relaxation occurs when Ca2+unbinds from troponin.
- Ca2+is pumped backinto the sarcoplasmicreticulum for storage.
- Ca2+is exchanged withNa+by the NCX antiporter.
10.Na+ gradient is maintainedby the Na+-K+-ATPase.
Cardiac troponins are an indicator for ___
Heart damage ( cell death)
Cardiac troponins in blood is as useful tool for
Indicate that a heart attack has occurred
Like other excitable tissues cardiac muscle has a ____
Refractory period
Heart has longer refractory period because ___ and why does it have it long comparing to skeletal muscles
The long RP is due to Na+ channels that are inactivated until the membrane has repolarized
Heart needs alternate periods of contraction and filling
Heart can beat by itself , why nervous system is needed
it can modify heart rate.
How both the para and sympa NS bring about their affects on the heart
altering the activity of the cAMP second messenger system in the innervated cardiac muscle cells.
How parasympathetic nerves system communicates with heart
The parasympathetic nerve to the heart is the vagus (cranial nerve X) nerve which primarily affects the atrium and the SA and AV nodes
How para NS decrease heart beat
releasing acetycholine which increases the permeability of the K+ channels (more K+ out of cell) which has a hyperpolarization effect.
Para NS acts ___ on blood vessels
Vasodilation
Sympathetic signals to our heart originates from
Cervical -C1-C3, C7,C8
Thoracic spinal nerves T1-T4
Symp NS is a need for ___
Greater blood flow
Symp NS and how it makes the heart beat more quickly
–Stimulates SA node by releasing norepinephrine by accelerating inactivation of K+ channels-less able to leave the cell
–Cell becomes less negative
–Swifter drift to AP
–Heart beats more forcefully and squeezes out more blood.
–Has a vasoconstriction effect on the blood vessels
What are cardiac pressoreflexes
Receptors sensitive to changes in pressure (baroreceptors) are located in two places in the heart
•They send nerve fibers to the cardiac control center in the medullar oblongata
•These stretch receptors located in the aorta and the carotid sinus
•These receptors coordinate with the integrators in the cardiac controls centers in negative feedback loops to oppose changes in blood pressure by adjusting the heart rate. ( if increased blood pressure-> parasymp.; decreased-> sympa)
