Muscle Phyiology 1 & 2 Flashcards
TYPES OF MUSCLES
how many are there?
give 4 characteristics for each (where they are present, functions, structure, voluntary or involuntary?) and how much space do they take up in the body/how much % of them in body?
Skeletal (40% of the body)
a. voluntary muscle, controlled consciously
b. striated muscle
c. attached to skeleton
d. locomotion, posture and body temp.
Smooth (10% of the body)
a. involuntary muscle, controlled unconsciously
b. non-striated muscle
c. in the wall of blood vessels, and internal organs
d. respiration, digestion, blood circulation
Cardiac
a. controls itself with help from nervous and endocrine systems
b. striated muscle
c. only in the heart
d. blood circulation
MUSCLE PROPERTIES
MUSCLES HAVE #? SPECIFIC PROPERTIES THAT ENABLE THEM TO PERFORM THEIR FUNCTIONS EFFECTIVELY and they are?
KEY POINTS (General Characteristics of a Muscle Fiber)
- muscle contraction is essential for many physiological functions including ?, ?, ? etc.
- contractility: the ability to shorten or contract, allowing muscles to generate tension
- extensibility: property of muscles that allows them to be stretched or lengthened beyond their resting length
- elasticity: the ability to return to its original shape after being stretched or contracted
- excitability: the capacity to receive and respond to stimuli (from the motor neuron, neurotransmitters, hormone, etc.)
KEY POINTS (General Characteristics of a Muscle Fiber)
- muscle contraction is essential for many physiological functions including locomotion, respiration, blood and lymph circulation, etc.
Skeletal Muscle
Primary function is to ?
– Attached to the ? of the skeleton
– Skeletal muscles work in coordination with the ? to produce ? movements, such as walking, running, and lifting objects.
– Most segments have #? muscles on both sides either to increase or decrease its ?.
– Is stimulated by a ?
– Under ? (conscious) control
– Attached to the bones of the skeleton
– Skeletal muscles work in coordination with the skeletal system to produce voluntary movements movements, such as walking, running, and lifting objects.
– Most segments have one or more muscles on both sides either to increase or decrease its angle.
– Is stimulated by a motor neurone
– Under voluntary (conscious) control
Skeletal Muscle Structure
EPIMYSIUM – A fascia of ? that surrounds the entire muscle.
FASCICLE - A small bundle or cluster of ?
PERIMYSIUM - Connective tissue extensions from the ? that surround each ?.
ENDOMYSIUM - Connective tissue extensions from the ? that surround the ? and are attached to the sarcolemma.
MYOFIBRILS - Each ?contains several hundred to several thousands myofibrils. Each myofibril is composed by a ?
MYOFILAMENTS - Are responsible for ?. Composed of ? & ? filaments.
TEPFEMM (top/outermost to bottom/innermost)
EPIMYSIUM – A fascia of fibrous connective tissue (like ligament) that surrounds the entire muscle.
FASCICLE - A small bundle or cluster of muscle fibers
PERIMYSIUM - Connective tissue extensions from the epimysium that surround each fascicle.
ENDOMYSIUM - Connective tissue extensions from the perimysium that surround the muscle fibers and are attached to the sarcolemma.
MYOFIBRILS - Each muscle fiber contains several hundred to several thousands myofibrils. Each myofibril is composed by a linear series of repeating sarcomeres
MYOFILAMENTS - Are responsible for muscle contraction. Composed of thin and thick filaments.
LEVELS OF ORGANIZATION IN SKELETAL MUSCLE
SARCOLEMMA
– It is a ? cell membrane enclosing a ? (cell)
– A special feature of the sarcolemma is that it invaginates into the ? of the muscle cell, forming membranous ?
MUSCLE FIBERS
– Bundle of myofibril – elongated shape
– Contain the basic ? (aka ?)
– Divided in ? and ? fibers
SARCOMERE
– Contain the ?, basic contractile unit of striated muscle fibers (Found between ? LINES or ? discs)
– Their arrangement gives the ? pattern.
LEVELS OF ORGANIZATION IN SKELETAL MUSCLE
SARCOLEMMA
– It is a thin cell membrane enclosing a skeletal muscle fiber (cell)
– A special feature of the sarcolemma is that it invaginates into the sarcoplasm of the muscle cell of the muscle cell, forming membranous T-tubules
MUSCLE FIBERS
– Bundle of myofibril – elongated shape
– Contain the basic contractile unit (aka sarcomere)
– Divided in type 1 (red) and type 2 (white) fibers
SARCOMERE
– Contain the myofilaments, basic contractile unit of striated muscle fibers (Found between Z LINES or Z discs)
– Their arrangement gives the striated pattern.
MYOFILAMENTS
Myofilaments are responsible for ?
Thin filament contains:
Thick filament contains:
A Myosin Filament (Thick Filament)
- Are composed of multiple ? molecules
– Myosin molecule contains a ? of intertwined helices and 2 ?
that can bind both ? and ? - Functions as ? – uses ATP as an energy source for ?
– Aproximately 500 myosin heads of a thick myosin filament form ? that interact with actin to shorten the sarcomere
Myofilaments are responsible for muscle contraction
Thin filament contains: actin, troponin complex, tropomyosin
Thick filament contains: myosin
A Myosin Filament (Thick Filament)
- Are composed of multiple myosin molecules
– Myosin molecule contains a TAIL of intertwined helices and 2 globular HEADS
that can bind both actin and ATP - Functions as ATPase enzyme – uses ATP as an energy source for contraction
– Approximately 500 myosin heads of a thick myosin filament form cross bridges that interact with actin to shorten the sarcomere
An Actin Filament (Thin Filament)
composed of ?
– 2 helical strands of ?protein
– 2 helical strands of ? protein
All intertwined together as a large helical complex
– Troponin is a complex of #? globular protein subunits which are T, I C
* TnC – ? binding subunit
* TnI – ? subunit
* TnT – ? binding subunit
Organelles of the Muscle Cell (Fiber)
MITOCHONDRIA
– Power plant of ?
– Provides ? with large amounts of energy allowing muscle ?
– ? fibers (red) have more numbers of mitochondria
SARCOPLASMIC RETICULUM
– Is a specialized ?
– Very important for ?
– Regulates ?
– ? in fast contracting fibers (white)
T-TUBULES
– Tubules arranged ? to the myofibril
– Periodic invaginations of the ?
– Carry the ? to the interior of the fiber.
– Presence of ? (dihydropyridine receptor) attached physically to the ? receptor voltage gated in the sarcoplasmic reticulum.
An Actin Filament (Thin Filament)
composed of actin, troponin complex, tropomyosin
– 2 helical strands of actin protein
– 2 helical strands of tropomyosin protein
All intertwined together as a large helical complex
– Troponin is a complex of 3 globular protein subunits which are T, I C
* TnC – Calcium binding subunit
* TnI – Inhibitory subunit
* TnT – Tropomyosin binding subunit
Organelles of the Muscle Cell (Fiber)
MITOCHONDRIA
– Power plant of ATP
– Provides myofibers with large amounts of energy allowing muscle contraction
– slow-twitch fibers (red) have more numbers of mitochondria
SARCOPLASMIC RETICULUM
– Is a specialized ER
– Very important for muscle contraction
– Regulates calcium uptake, release, and reuptake
– bigger in fast contracting fibers (white)
T-TUBULES
– Tubules arranged transversely to the myofibril
– Periodic invaginations of the sarcolemma
– Carry the depolarization from action potentials to the interior of the fiber.
– Presence of voltage-sensitive receptor (dihydropyridine receptor) attached physically to the ryanodine receptor voltage-gated in the sarcoplasmic reticulum.
The Muscle Fiber KEY POINTS
- The skeletal muscle is surrounded by several layers of connective tissue (epimysium, perimysium, and endomysium) that provide ? and ? to the muscle and prevent it from ?
- ? is enclosed by a plasma membrane called the sarcolemma.
- The sarcoplasmic reticulum (SR) is a specialized organelle responsible for ? and ? and reuptake ion calcium.
- T-tubules allow for ? of the action potential into the ? and play an important role in regulating cellular ?
The Myofibril
- Myofibrils are made up of ?, the ? units of a muscle.
- A sarcomere is composed of filaments of two proteins i.e. ? and ? which are responsible for muscle contraction.
- Myosin is a thick filament with a ? at one end
- An actin filament is composed of 3 things what are they?. Actin is attached to a ?
The Muscle Fiber KEY POINTS
- The skeletal muscle is surrounded by several layers of connective tissue (epimysium, perimysium, and endomysium) that provide strength and stability to the muscle and prevent it from ripping while contracting
- a muscle fiber is enclosed by a plasma membrane called the sarcolemma.
- The sarcoplasmic reticulum (SR) is a specialized organelle responsible for storing, releasing and reuptake of ion calcium.
- T-tubules allow for rapid transmission of the action potential into the cell and play an important role in regulating cellular calcium concentration.
The Myofibril
- Myofibrils are made up of sarcomeres, the smallest functional units of a muscle.
- A sarcomere is composed of filaments of two proteins i.e. actin and myosin which are responsible for muscle contraction.
- Myosin is a thick filament with a globular at one end
- An actin filament is composed of 3 things, they are troponin, tropomyosin and actin. Actin is attached to a Z disk
The Sliding Filament Model
- Proposed in the early 1950s.
- Two British biologists,? and
? - The theory proposes that a muscle
shortens or lengthens because ? and ? filaments slide over each other without changing ?.
SLIDING FILAMENT MODEL OF MUSCLE CONTRACTION
Before muscle contraction begins Myosin heads bind with ? (low energy configuration)
– The ? activity immediatly cleaves the ? in ?
– Cleavage products are kept bound to the ?
– Head becomes energized in a “? position”
When ? bind the troponin-tropomyosin complex, active sites of the actin filaments are ?
– ? bind to these sites
– The ? is formed
– The ? and ? is released
- The cross-bridge causes a ?
– Myosin heads bend toward the center of the sarcomere, causing the actin to slide toward the ? - this is known as **?
– The energy that activates comes from the ?
– Another ATP molecule will take place causing ? to begin a new cycle
- Proposed in the early 1950s.
- Two British biologists Hugh Huxley and
Andrew Huxley - The theory proposes that a muscle
shortens or lengthens because thick and thin filaments slide over each other without changing length
Sliding Filament Model of Muscle Contraction
Before muscle contraction begins Myosin heads bind with ATP (low energy configuration)
– The ATPase activity immediatly cleaves the ATP in ADP and Pi
– Cleavage products are kept bound to the head
– Head becomes energized in a “cocked position”
When calcium ions bind the troponin-tropomyosin complex, active sites of the actin filaments are uncovered
– Myosin heads bind to these sites
– The cross-bridge is formed
– The phosphate ion and ADP is released
- The cross-bridge causes a conformational change in the head
– Myosin heads bend toward the center of the sarcomere, causing the actin to slide toward the M line - this is known as **POWER STROKE
– The energy that activates comes from the stored ADP
– Another ATP molecule will take place causing detachment of the myosin head from the actin filament to begin a new cycle
KEY POINTS
Muscle Fiber Action
w/ Muscle action is initiated by a ?.
If the cell receives the right stimulus, an action potential occurs which releases stored ?
? bind with troponin, which lifts the ? molecules off the active sites on the ?. These open sites allow the ? to bind to them.
Energy for muscle action is provided when the myosin head binds to ?
? on the myosin head splits the ATP into a ?
Muscle Fiber Action
- Once myosin binds with actin, what happens?
- Muscle action ends when calcium is pumped out of the ? to the ? for storage.
KEY POINTS
Muscle Fiber Action
w/ Muscle action is initiated by a nerve impulse
If the cell receives the right stimulus, an action potential occurs which releases stored Calcium ions (Ca 2+ ions)
Calcium ions bind with troponin, which lifts the tropomyosin molecules off the active sites on the actin filament. These open sites allow the myosin heads to bind to them.
Energy for muscle action is provided when the myosin head binds to ATP.
ATPase on the myosin head splits the ATP into a usable energy source (ADP and P)
Muscle Fiber Action
- Once myosin binds with actin, myosin head tilts and pulls the actin filament so they slide across each other.
- Muscle action ends when calcium is pumped out of the sarcoplasm to the sarcoplasmic reticulum for storage.
Types of Muscle Fibers
– Skeletal muscles contain both Type I and Type II fibers.
- Type I (color?)
– Type I fibers have high ? and are suited to ?
activities. - Type II (color?)
– Type II fibers are better for ? or ?
» Type IIa
» Type IIb
MUSCLE FIBERS
TYPE 1 - ? Fiber
– High aerobic capacity and ?
– Rich in ?
– ? speed (110 ms)
– Plentiful in muscles which the main function is ?
– #? fibers per motor neuron
- Type IIa – Are ? fiber
– ? aerobic (oxidative) capacity and ? resistance
– High ? (glycolytic) capacity
– ? contractile speed (50 ms)
– ? developed sarcoplasmic reticulum
– #? fibers per motor neuron - (Type IIb) – Glycolytic Fiber
– ? aerobic (oxidative) capacity and fatigue
resistance
– ? anaerobic (glycolytic) capacity and motor unit strength
– ? contractile speed (50 ms)
– ? developed sarcoplasmic reticulum
– ? fibers per motor neuron
Types of Muscle Fibers
– Skeletal muscles contain both Type I and Type II fibers.
- Type I (Red)
– Type I fibers have high aerobic endurance and are suited to low-intensity endurance activities. - Type II (White)
– Type II fibers are better for anaerobic or explosive activites
» Type IIa
» Type IIb
MUSCLE FIBERS
TYPE 1 - Oxidative Fiber
– High aerobic capacity and fatigue resistence
– Rich in mitochondria
–slow contractile speed (110 ms)
– Plentiful in muscles which the main function is slow prolonged activity like marathon running
– 10-180 fibers per motor neuron
- Type IIa – Are mixed-oxidative glycolytic fiber
– high aerobic (oxidative) capacity and fatigue resistance
– High anaerobic (glycolytic) capacity
– fast contractile speed (50 ms)
– highly developed sarcoplasmic reticulum
– 300-800 fibers per motor neuron
(Type IIb) – Glycolytic Fiber
– Low aerobic (oxidative) capacity and fatigue
resistance
– High anaerobic (glycolytic) capacity and motor unit strength
– Fast contractile speed (50 ms)
– Highly developed sarcoplasmic reticulum
– 300–800 fibers per motor neuron
FUNCTIONAL CLASSIFICATION OF MUSCLES
? — muscle responsible for the movement
? — oppose the agonists to prevent overstretching of them
? — assist the agonists and sometimes fine-tune the direction of movement
TYPES OF MUSCLE ACTION
1. Concentric:
2. Static:
3. Eccentric:
agonist — muscle responsible for the movement
antagonists — oppose the agonists to prevent overstretching of them
synergists — assist the agonists and sometimes fine-tune the direction of movement
TYPES OF MUSCLE ACTION
1. Concentric: muscle shortens
2. Static: muscle length is unchanged
3. Eccentric: muscle lengthens
Satellite Cell Function
- Satellite cells are a type of ? located in ? muscles.
- Are involved in muscle ? and ?.
- Are normally in a ? but become activated when a muscle is ? and multiply to form new muscle fibers or ?
- ? Factor (MGF).
- ? (Interleukin 6 (IL-6) and ? alpha (TNF-α).
MYOSTATIN FUNCTION
Its primary function is to regulate ? and ? by inhibiting the proliferation and differentiation of ?
Produced and secreted by ?
Myostatin has been the subject of intense research in the field of muscle biology and has been identified as a potential therapeutic target for conditions associated with ?, such as ? and ?.
- Satellite cells are a type of stem cell located in skeletal muscles.
- Are involved in muscle growth and repair.
- Are normally in a dormant state but become activated when a muscle is injured and multiply to form new muscle fibers or myofibers
- Mechano Growth Factor (MGF).
- Inflammatory citokines (Interleukin 6 (IL-6) and Tumor necrosis factor alpha (TNF-α).
MYOSTATIN FUNCTION
Its primary function is to regulate muscle growth and development by inhibiting the proliferation and differentiation of muscle cells
Produced and secreted by skeletal muscle cells
Myostatin has been the subject of intense research in the field of muscle biology and has been identified as a potential therapeutic target for conditions associated with muscle wasting, such as muscular dystrophy and sacropenia.
SMOOTH MUSCLE
SMOOTH MUSCLE OF EACH ORGAN IS DISTINCTIVE or SIMILAR?:
- ? to adjust to the organs they are in;
- Organization into ? or ? to enable coordinated contractions for functions like digestion and blood flow regulation.
- ? to ?, including neural, hormonal and local factors (O2, CO2, H2).
- ? from the autonomic nervous system (Sympathetic and Parasympathetic nervous system).
- Smooth muscle has ? depending on the organ it is in, including ?, regulation of ?, and control of ?
SMOOTH MUSCLE
SMOOTH MUSCLE OF EACH ORGAN IS DISTINCTIVE:
- Different physical dimensions to adjust to the organs they are in;
- Organization into bundles or sheets to enable coordinated contractions for functions like digestion and blood flow regulation.
- response to different stimuli, including neural, hormonal and local factors (O2, CO2, H2).
- receives nerve signals from the autonomic nervous system (Sympathetic and Parasympathetic nervous system).
- Smooth muscle has various functions depending on the organ it is in, including peristaltic contraction, regulation of blood flow, and control of airway diameter.
TYPES OF SMOOTH MUSCLE
- Can be generally divided into
– ?
– ?
- Can be generally divided into
– SINGLE-UNIT (VISCERAL) SMOOTH MUSCLE
– MULTI-UNIT SMOOTH MUSCLE
SINGLE-UNIT SMOOTH MUSCLE
– Also called *?, ? or ? smooth muscle
– Fibers are arranged in ? or ?
* Cell membranes are ?
* The force generated in one ? can be transmitted to the next
* Contract ?
– Cell membranes are joined by many ?
* Ions can flow freely from one ? to the ?
* Fibers contract ?
– Locations
* 5 name
- MULTI-UNIT SMOOTH MUSCLE
– ? smooth muscle fibers
– Each muscle fiber contract ? – Inervated by a ?
– Locations name 5
SINGLE-UNIT SMOOTH MUSCLE
– Also called visceral, syncytial or unitary smooth muscle
– Fibers are arranged in bundles or sheets
* Cell membranes are adherent to one another
* The force generated in one muscle fiber can be transmitted to the next
* Contract together as a single unit
– Cell membranes are joined by many gap junctions
* Ions can flow freely from one muslce cell to the next
* Fibers contract together
– Locations (GBUUM)
Gastrointestinal tract, Bile duct, ureter, uterus, many blood vessels
- MULTI-UNIT SMOOTH MUSCLE
– discrete, separate smooth muscle fibers
– Each muscle fiber contracts independently (look at drawing to understand it)
– Innervated by a single nerve ending
– Locations (BWISC)
Base of hair follicles, Walls of large blood vessels, iris muscle of the eyes, smaller airways to lungs, and ciliary muscles of the eyes.
Particularities of SMOOTH Muscle
-Smooth muscle has ? nucleous at the cell’s center.
-Smooth muscle does not contain ?, but it contains ? and ?, and contract via a ?
- Smooth muscle does not have the same ? of actin and myosin filaments
- The actin filaments are attached to ?, which are analogous to the Z-discs in ? muscle sarcomeres.
- Some bodies are attached to ?
- Some bodies are ? inside the cell
Myosin filaments are ? the actin filaments
Myosin filaments have ? cross bridges
– They are arranged so that the bridges on one side ? and those on the other side bend in the ? direction
– This configuration allows the myosin to ? simultaneously in opposite directions
– Smooth muscle can contract as much as #%? of their length but Skeletal muscle #%?
? frequency of cross-bridge cycles
– ? energy to mantain the contraction - 1/? to 1/300 of the energy necessary to contract skeletal muscle.
– Once smooths muscle initiates the contraction, a ? energy is needed to keep the tonic contraction for ?.
– Some smooth muscle has a tonic contracting, that can last for ?.
(side note: TONIC CONTRACTION: the sustained contraction of different groups of fibers within a muscle to maintain continual muscular tension (tonus).
Sarcoplasmic reticulum is ? developed
– It is not the major source of Ca2+ for smooth muscle contraction – ? is!
* are SRs present in all smooth muscles?
– Lies near the ? in some larger smooth muscle cells
– Small invaginations of the cell membrane, called ?, that make contact with the surface of ?.
* ? T-Tubule.
* Is believed to ?
– The more extensive (covering a large area) the SR in the smooth muscle fiber, the more ? it contracts
- Smooth muscle has one nucleus at the cell’s center.
- Smooth muscle does not contain myofibrils or sarcomeres, but it contains thick and thin filaments, and contract via a sliding filament mechanism
- Smooth muscle does not have the same striated arrangment of actin and myosin filaments
- The actin filaments are attached to dens, which are analogous to the Z-discs in striated muscle sarcomeres.
- Some bodies are attached to cell membrane
- Some bodies are dispersed inside the cell
Myosin filaments are inserted among the actin filaments
Myosin filaments have side polar cross bridges
– They are arranged so that the bridges on one side bend in one direction and those on the other side bend in the opposite direction
– This configuration allows the myosin to pull an actin filament simultaneously in opposite directions
– Smooth muscle can contract as much as 80%of their length but Skeletal muscle 30%
Low frequency of cross-bridge cycles
– low energy to mantain the contraction - 1/10 to 1/300 of the energy necessary to contract skeletal muscle.
– Once smooths muscle initiates the contraction, a low energy is needed to keep the tonic contraction for hours.
– Some smooth muscle has a tonic contracting, that can last for hours or days.
(side note: TONIC CONTRACTION: the sustained contraction of different groups of fibers within a muscle to maintain continual muscular tension (tonus).
Sarcoplasmic reticulum is slightly developed
– It is not the major source of Ca2+ for smooth muscle contraction – extracellular fluid is!
* are SRs present in all smooth muscles? NO
– Lies near the cell membrane in some larger smooth muscle cells
– Small invaginations of the cell membrane, called CAVEOLAE, that make contact with the surface of SR.
* rudimentary T-Tubule.
* Is believed to excite the calcium release from the SR.
– The more extensive (covering a large area) the SR in the smooth muscle fiber, the more rapidly it contracts
Smooth Muscle Contraction
Smooth muscle uses ? as a calcium-binding protein to regulate the contraction process instead of ?.
- Calcium-bound calmodulin, resulting in its ?.
- Activated calmodulin then activates an enzyme called A?. A? then ? a specific region of myosin.
- ? binds to actin, forming a cross-bridge between myosin and actin allowing the muscle cell to ?.
- When the ? is reduced, ? removes the phosphate from the myosin light chain, causing muscle ?
Smooth Muscle Contraction
*Smooth muscle uses calmodulin as a calcium-binding protein to regulate the contraction process instead of troponin
- Calcium-bound calmodulin, resulting in its activation
- Activated calmodulin then activates an enzyme called myosin light chain kinase (MLCK). MLCK phosphorylates a specific region of myosin.
- phosphorylated myosin binds to actin, forming a cross-bridge between myosin and actin allowing the muscle cell to contract.
- When the ion calcium concentration is reduced, myosin phosphatase removes the phosphate from the myosin light chain, causing muscle relaxation
keywords: myosin light chain kinase; myosin phosphatase
Cardiac Muscle
(Cardiac muscle tissue is found only in the ?!
Cardiac means “relating to the heart”.)
- Cardiac muscle cells are called ? or ?.
- These cells make up the ? which is the muscle layer of the heart.
- The ? contracts to pump ? throughout the body, supplying organs and tissue with oxygen and nutrients.
- The structure of cardiac muscle share some similarities with ?
– Fibers are ?
– Myofibrils are made up from ? (Similar organization of the ?)
– Contains a ? Sarcoplasmic Reticulum
– T-tubules (also release ?) - But cardiac muscle also differs from skeletal muscle in several ways
– Contraction is ? (controled via ?)
– Fibers are ? and ?
– Usually nucleus? how many (like which muscle type)
– Interconnected by ? (look at pic in answer to understand it better)
– Generates their ? (? fibers)
Cardiac Muscle
(Cardiac muscle tissue is found only in the ?!
Cardiac means “relating to the heart”.)
- Cardiac muscle cells are called cardiomyocytes or cardiocytes
- These cells make up the myocardium which is the muscle layer of the heart.
- The myocardium (muscle layer of heart) contracts to pump blood throughout the body, supplying organs and tissue with oxygen and nutrients.
- The structure of cardiac muscle share some similarities with skeletal muscle
– Fibers are striated
– Myofibrils are made up from actin and myosin filaments (Similar organization of the sarcomere)
– Contains a less developed Sarcoplasmic Reticulum (like smooth too in this case)
– T-tubules (also release ion calcium) - But cardiac muscle also differs from skeletal muscle in several ways
– Contraction is involuntary (controlled via the autonomic nervous system)
– Fibers are short and branched
– Usually uninucleated (like smooth muscle)
– Interconnected by intercalated disks (look at pic in answer to understand it better)
– Generates their own action potential (pacemaker fibers)
Cardiac Muscle
THE CARDIAC ACTION POTENTIAL IS NOT INITIATED BY ?
– It is rather generated by a group of specialized cells known as * x? *.
– These x cells have ? generation capability.
– x cells Are found in the *? in the right atrium.
– They produce roughly ? action potentials every minute.
Cardiac muscle is a *?
– Greek: *Syn = ? + *Kytos = cell
– Do not fuse into a ? during embryonic development like skeletal muscle does (morphological syncytium)
– Cardiac myocytes ? or ? during development and bind to other myocytes
– Fibers remain separated as ? with their respective sarcolemma
* ? connected to each other through ?
The ? is a dark, dense cross-band found in the end of each myocardial cell
– Continuous with the sarcolemma
– Contain important ?
* GAP JUNCTIONS (refer to pic)
– Allow ?
– ? travel easily from one cell to the next
* DESMOSOME
– Provide ? and ?
Cardiac Muscle
THE CARDIAC ACTION POTENTIAL IS NOT INITIATED BY NERVOUS ACTIVITY
– It is rather generated by a group of specialized cells known as * pacemaker cells
– These x cells have automatic action potential generation capability.
– these pacemaker cells are found in the *sino-atrial node in the right atrium.
– They produce roughly 60-100 action potentials every minute.
Cardiac muscle is a FUNCTIONAL SYNCYTIUM (a single cell mass w several nuclei is produced by cell fusion or nuclei division is called as syncitium
– Greek: *Syn = together + *Kytos = cell
– Do not fuse into a single multinucleated fiber during embryonic development like skeletal muscle does (morphological syncytium)
– Cardiac myocytes branch or bifurcate during development and bind to other myocytes
– Fibers remain separated as distinct cells with their respective sarcolemma
* electrically connected to each other through intercalated disks
The INTERCALATED DISK is a dark, dense cross-band found at the end of each myocardial cell
– Continuous with the sarcolemma
– Contain important cell-cell junctions
* GAP JUNCTIONS (refer to pic)
– Allow rapid fusion of ions
– action potential travels easily from one cell to the next
* DESMOSOME
– Provide mechanical strength and stability
- allows transmission of force during contraction
key works: myocardium = muscle layer of heart
- Cardiac muscle consists of elongated cells called cardiomyocytes
- Cardiac muscle contracts involuntarily, but the contraction is controlled via ANS
- Intercalated discs are unique structures found between adjacent cardiac muscle cells. They contain specialized cell-to-cell junctions called desmosomes and gap junctions.
