Muscle Histology

Question 1

There are 3 types of human muscle

• Skeletal • Cardiac • Smooth

Answer 1

There are 3 types of human muscle • Skeletal • Cardiac • Smooth

Question 2

Muscle Activity Stength, Speed, Continuity, Voluntary

• Skeletal→___ ____ ____ ____

Cardiac→ ___ ___ ____ ____

• Smooth→ ___ ___ ___

Answer 2

Muscle Activity • Skeletal→ Strong quick discontinuous, voluntary Cardiac→ Strong, quick continuous, involuntary • Smooth→ Weak, slow, involuntary

Question 3

Muscle Striation/Shape

• Skeletal: ____, ___ ___
• Cardiac: ____, __ ___

s • Smooth: ___ ___, ___, ___ ___

Answer 3

Muscle Striation/Shape • Skeletal: Striated, Straght Fibers • Cardiac: Striated, Branched Fibers • Smooth: NOT striated, Spindle, Indiv Cells

Question 4

Fascicle:

The Major Segment of muscle, ___ of muscle ___

Fibers bundled into fascicles

Fascicles are further bundled into the ___ ___ itself, divided up by ___

____–> ____–> ___—> ____

Answer 4

Fascicle: The Major Segment of muscle, bundle of muscle fibers Fibers bundled into fascicles Fascicles are further bundled into the muscle mass itself, divided up by CT. MyofibrilàFiberàFascicleàMuscle

Question 5

Muscle Nuclei

• Centrally located in the fibers and cells of_________ muscle, but on the periphery of _____muscle.

Answer 5

Muscle Nuclei • Centrally located in the fibers and cells of CARDIAC and SMOOTH muscle, but on the periphery of SKELETAL muscle.

Question 6

• Remember, contraction is parallel with ___ ___
• Strength, endurance and fine control is dependent on __ of ___, ___ and __of___

. • Pink-red color of skeletal muscle is due to blood and ____ content.

• Transmission of force is to ___, other muscle via ____ at myotendonal junctions.
• ***The action is voluntary EXCEPT for the ___, which although comprised of skeletal muscle, is involuntary***
• A quick look at the myotendonal junction, where you should eventually be able to recognize striated muscle and ___ ____connective tissue of the tendon. • Easiest start, muscle is striated (see below), tendon is ____

Answer 6

• Remember, contraction is parallel with fiber orientation • Strength, endurance and fine control is dependent on number of fibers, size and type of innervation. • Pink-red color of skeletal muscle is due to blood and myoglobin content. • Transmission of force is to bone, other muscle via tendons at myotendonal junctions. • ***The action is voluntary EXCEPT for the diaphragm, which although comprised of skeletal muscle, is involuntary*** • A quick look at the myotendonal junction, where you should eventually be able to recognize striated muscle and dense, regular connective tissue of the tendon. • Easiest start, muscle is striated (see below), tendon is not

Question 7

White Muscle

• The term “white muscle” refers to ___ ___ muscle tissue lacking in pigment due to the absence of ___ molecules.

o Myoglobin, a unique protein found exclusively in the ___ ___ muscles — which are known as ___ muscles —, attracts and stores ___ and ___

. o Much like in blood, the combination of oxygen and iron in myoglobin imparts a crimson ____ to muscles of regular use.

• Since white muscle tissue is seldom used, it does not require ready stores of ____ and, thus, has little distinguishable myoglobin or its associated pigment.
• White muscles are capable of movement — specifically ___ and __ ___ actions — and are noted for being___ contracting muscles that return to rest ___ ___

; • Red muscles, on the other hand, contract ___

Answer 7

White Muscle • The term “white muscle” refers to seldom-used muscle tissue lacking in pigment due to the absence of myoglobin molecules. o Myoglobin, a unique protein found exclusively in the frequently-used muscles — which are known as red muscles —, attracts and stores iron and oxygen. o Much like in blood, the combination of oxygen and iron in myoglobin imparts a crimson tinge to muscles of regular use. • Since white muscle tissue is seldom used, it does not require ready stores of oxygen and, thus, has little distinguishable myoglobin or its associated pigment. • White muscles are capable of movement — specifically quick and short explosive actions — and are noted for being fast-contracting muscles that return to rest very quickly; • Red muscles, on the other hand, contract slowly.

Question 8

Two types of Skeletal Muscle

___ ___ → White Muscle

___ ___→ Red Muscle

Answer 8

Two types of Skeletal Muscle Fast glycolytic (FG) → White Muscle Slow oxidative (SO) → Red Muscle

Question 9

• The striated appearance muscle is due to ‘registered’____
• That is, they repeat consistently.
• From ___ to ___ is a sarcomere (S), the basic ___ ___ of this muscle and with a length of approximately 2.2:M, a very useful internal ruler

Answer 9

• The striated appearance muscle is due to ‘registered’ myofibrils. • That is, they repeat • consistently. • From Z-line to Z-line is a sarcomere (S), the basic contractile unit of this muscle and with a length of approximately 2.2:M, a very useful internal ruler

Question 10

The bands that form this striated appearance are:

• Z-line. o At the ___ of each sarcomere. o ___ is anchored here by actinin; o It bisects the___ band
• I-band. o Mostly ___ ___filaments here, with regularly spaced regulatory proteins, ____ and ____. o ____ has 3 subunits, Tn_, Tn_ and Tn_ • I = inhibitory, T = Tropomyosin and C = Calcium o Important ! Width ____ in contraction
• A-band. o Mostly ____ but some actin-myosin____. Width _____during contraction!
• H-band. o ___ region of ___ band containing only ___ ___ filaments o Width ____ in contraction (Like the I band)
• M-line. o ___ of the ___ and where ____ is joined ___ to its ____ neighbor

Answer 10

The bands that form this striated appearance are: • Z-line. o At the end of each sarcomere. o Actin is anchored here by actinin; o It bisects the I band • I-band. o Mostly thin actin filaments here, with regularly spaced regulatory proteins, tropomyosin and troponin. o Troponin has 3 subunits, TnI, TnT and TnC • I = inhibitory, T = Tropomyosin and C = Calcium o Important ! Width decreases in contraction • A-band. o Mostly myosin, but some actin-myosin overlap o Width remains constant during contraction! • H-band. o Central region of A band containing only thick myosin filaments o Width decreases in contraction (Like the I band) • M-line. o Middle of the H band and where myosin is joined laterally to its myosin neighbor

Question 11

Because of the regimented arrangement as seen on the previous two slides, when a muscle is cut in cross section, certain patterns emerge that determine where we are in a sarcomere.

This would be the M line. Thick proteins joined laterally to thick proteins.

This would be the A-band: Thick filaments, surrounded by ___ thin filaments

Answer 11

Because of the regimented arrangement as seen on the previous two slides, when a muscle is cut in cross section, certain patterns emerge that determine where we are in a sarcomere. This would be the M line. Thick proteins joined laterally to thick proteins. This would be the A-band: Thick filaments, surrounded by a number (6) of thin filaments

Question 12

Contraction

• The contraction of the muscle is due to the____ proteins we have just seen and ____ and such that drive the interactions but we will concentrate on only 4

o Myosin o actin o tropomyosin o troponin (and its subunits)

• The proteins are put together in such a manner that the contraction-relaxation cycle can occur, and___e and ___ the energy to support that function.
• Here we will deal with the structural aspects of the component proteins and only the very basics of contraction that begins at the ___ ____

Answer 12

Contraction • The contraction of the muscle is due to the component proteins we have just seen and kinases and such that drive the interactions but we will concentrate on only 4 o Myosin o actin o tropomyosin o troponin (and its subunits) • The proteins are put together in such a manner that the contraction-relaxation cycle can occur, and provide and use the energy to support that function. • Here we will deal with the structural aspects of the component proteins and only the very basics of contraction that begins at the neuromuscular junction.

Question 13

THE FOUR PROTEINS ARE:-

MYOSIN • Comprises the bulk of the___ ___• It is shaped like a __ ___ with __ heads on one end. • The head region contains the ‘__ ___’ proteins and the___ ___ machinery that regulate contraction.

ACTIN • Major component of the ___ ___. Formed from ____r ____c actin molecules linked together, much like a ___ ___, to make an actin filament. • Hence _ and _ actin. • ___ ___-strands entwine to become a thin filament.

TROPOMYOSIN • A long protein molecule that lies in the ____ formed by the ___ ___ ___

TROPONIN • Has three subunits

o TnT binds ____

o TnC binds ___

o TnI inhibits the ___ ___ ___

• One troponin complex binds to__ ____molecule, which spans _ _-actin molecules. (More on this in Muscle II)

___ to Fibrils to Fibers to Fascicles to muscle mass

Answer 13

THE FOUR PROTEINS ARE:- MYOSIN • Comprises the bulk of the thick filaments. • It is shaped like a golf club with 2 heads on one end. • The head region contains the ‘light chain’ proteins and the ATP hydrolyzing machinery that regulate contraction. ACTIN • Major component of the thin filaments. Formed from globular monomeric actin molecules linked together, much like a pearl necklace, to make an actin filament. • Hence G and F actin. • Two F-strands entwine to become a thin filament. TROPOMYOSIN • A long protein molecule that lies in the groove formed by the entwined actin strands. TROPONIN • Has three subunits o TnT binds tropomyosin o TnC binds calcium o TnI inhibits the actin-myosin interaction • One troponin complex binds to one tropomyosin molecule, which spans 7 G-actin molecules. (More on this in Muscle II) Filaments to Fibrils to Fibers to Fascicles to muscle mass

Question 14

Sarcolemma •

This is the __ ___of the muscle cells (____).

• It contains many of the___ __, ___s,___s and ___ to regulate ion flow and some aspects of metabolism.
• The SL invaginates to form a __ ___ in both ___ and ___ muscle.

At the ___ band junction in ___, at the ___ in ___.

____ in cardiac muscle.

• ****Forms a ___ in skeletal,____ in cardiac.***
• Brings ____ deep within the muscle cells.
• Specialized region of SL only in skeletal muscle where the nerve ____s at the___ __ __

Answer 14

Sarcolemma • This is the outer covering of the muscle cells (fibers). • It contains many of the ionic pumps, proteins, channels and receptors to regulate ion flow and some aspects of metabolism. • The SL invaginates to form a T-tubule in both skeletal and cardiac muscle. At the A-I band junction in skeletal, at the Z-Line in cardiac. Wider in cardiac muscle. • ****Forms a triad in skeletal, dyad in cardiac.*** • Brings depolarization deep within the muscle cells. • Specialized region of SL only in skeletal muscle where the nerve arrives at the motor end plate

Question 15

Sarcoplasmic Reticulum

• The ___ ____ system, which has no connection with the ___ ___

. • Junctions with the ___ ___ to form the ___ (SM) or ___ (Cardiac)

• Major ___ depot for intracellular____

Answer 15

Sarcoplasmic Reticulum • The internal membrane system, which has no connection with the extracellular space. • Junctions with the t-tubule to form the triad (SM) or dyad (Cardiac) • Major storage depot for intracellular calcium

Question 16

Mitochondria

• Very ___ and ____ extensively ____and ____ the ____
• Produce the ____ for hydrolysis to power contraction and active ionic pumping.
• Small mito are often found ____ the outer _____, and they 0ften exist as a ____ (Extensive complex)

Answer 16

Mitochondria • Very long and branch extensively through and around the myofibrils. • Produce the ATP for hydrolysis to power contraction and active ionic pumping. • Small mito are often found under the outer sarcolemma, and they 0ften exist as a reticulum (Extensive complex)

Question 17

Nuclei

____, often located___ to ___ just under the ___

Answer 17

Nuclei Many, often located end-to-end just under the SL

Question 18

Others

Like all cells, other organelles and structures are present.

____ _____ _____ _____

Answer 18

Others Like all cells, other organelles and structures are present. Golgi, lysosomes, peroxisomes, glycogen Particles, etc

Question 19

A couple of Specialized Structure

To make sure that muscle are not _____, there are a couple of safety structures inserted in the muscle itself (___ ___), and in the ___ portion of the myo-tendonal junction (___ ___ ____).

These structures sense, ___ stance, stress, activity, etc and relay appropriate messages to the ___ ____ and___ ___ ___

Answer 19

A couple of Specialized Structure To make sure that muscle are not overstretched, there are a couple of safety structures inserted in the muscle itself (Muscle Spindle), and in the tendon portion of the myo-tendonal junction (Golgi Tendon Apparatus). These structures sense, tension, stance, stress, activity, etc and relay appropriate messages to the spinal cord and central nervous system.

Question 20

Golgi Tendon Apparatus

This structure collects information about differences in tension among ___ and relays data to the central nervous system, where they are processed and help to ____ fine muscular contractions.

Answer 20

Golgi Tendon Apparatus This structure collects information about differences in tension among tendons and relays data to the central nervous system, where they are processed and help to coordinate fine muscular contractions.

Question 21

CARDIAC MUSCLE

• This is not the ‘___ of ____” construction of skeletal muscle, but a more ____ grouping of ____ fibers, containing specialized ___ -___ junctions, the ____ ____
• The ___ ___ dispersed between the fibers doesn’t divide the muscle up into nice, discrete and distinct fascicles as in skeletal muscle.
• Not directly ____, but ____nerves present in the _____

. • Very ____

• The proteins are basically the ____ as those found in skeletal muscle, with a few specializations.

Answer 21

• This is not the ‘bundle of spaghetti” construction of skeletal muscle, but a more random grouping of branching fibers, containing specialized electro-mechanical junctions, the intercalated discs. • The connective tissue dispersed between the fibers doesn’t divide the muscle up into nice, discrete and distinct fascicles as in skeletal muscle. • Not directly innervated, but autonomic are nerves present in the myocardium. • Very vascular. • The proteins are basically the same as those found in skeletal muscle, with a few specializations.

Question 22

• The nuclei are centrally placed within the cardiac fibers, usually ___ of them in each myocyte between ___ ____
• Fibers are 15-25 micrometers wide and 18-120micrometers long
• Considerable branching.
• ___ components basically same as skeletal muscle, but subtle differences are there as previously mentioned (Important!)
• Striations are ___ apparent as not as rigidly ____ as skeletal muscle
• Large T-tubules that invaginate at ____e (NOT A-I)
• ___ (NOT triads)
• Lots of ___
• Intercalated discs

Answer 22

• The nuclei are centrally placed within the cardiac fibers, usually 1-2 of them in each myocyte between intercalated discs. • Fibers are 15-25 micrometers wide and 18-120micrometers long • Considerable branching. • Organellar components basically same as skeletal muscle, but subtle differences are there as previously mentioned (Important!) • Striations are less apparent as not as rigidly organized as skeletal muscle • Large T-tubules that invaginate at Z-line (NOT A-I) • Dyads (NOT triads) • Lots of mitochondria • Intercalated discs

Question 23

Membrane Specializations in Cardiac Muscle

Intercalated Discs: identifying feature of cardiac muscle.

• These allow, aide and enhance the propagation of the ____ through the ____
• An intercalated disc is an undulating ___ ____ separating adjacen ___ in cardiac muscle___.
• Intercalated discs support___ ____ of cardiac tissue.
• They can easily be visualized by a longitudinal section of the tissue.

Three types of membran____ exist within an intercalated disc:

Has some specializations of the membranes to ___ __ ___ and allow ___ ___

• Macula Adherens, often called a _____. o Usually found in the ____ region of the IC. o ___ separation during ____ by binding ___ ___ joining the cells together
• Fascia Adherens o ____ filaments anchor across the gap into a “___ like” mat to add some structure to the junction o ___ ____ for actin, and connects to the closest ____.
• Gap junction or ____ (neck). o Area of ___ resistance to allow ___ ___between two cardiac cells. This permits the wave of ____ to continue in a “__ fashion”. o Allow action potentials to spread between __ ___ by permitting the passage of ___ between cells, producing depolarization of the heart muscle

Answer 23

Membrane Specializations in Cardiac Muscle Intercalated Discs: identifying feature of cardiac muscle. • These allow, aide and enhance the propagation of the signal through the myocardium • An intercalated disc is an undulating double membrane separating adjacent cells in cardiac muscle fibers. • Intercalated discs support synchronized contraction of cardiac tissue. • They can easily be visualized by a longitudinal section of the tissue. Three types of membrane junctions exist within an intercalated disc: Has some specializations of the membranes to hold things together and allow ion transport • Macula Adherens, often called a Desmosome. o Usually found in the perpendicular region of the IC. o Stop separation during contraction by binding intermediate filaments joining the cells together • Fascia Adherens o Actin filaments anchor across the gap into a “felt like” mat to add some structure to the junction o Anchoring sites for actin, and connects to the closest sarcomere. • Gap junction or nexus (neck). o Area of low resistance to allow electrical coupling between two cardiac cells. This permits the wave of depolarization to continue in a “cable fashion”. o Allow action potentials to spread between cardiac cells by permitting the passage of ions between cells, producing depolarization of the heart muscle

Question 24

SMOOTH MUSCLE

• It is organized as ____ or____

___ vascularization and___ myoglobin content – ___

• ___ shaped cells with ___ ____ (Not fibers) • Cells 1-15µM in diameter, 25-300µM long

• ___ and ___ bundles anchor at ___ ___
• _____ SR
• ___ ___ between cells
• ____nerve endings
• No ___……………..No ____ • NO __ ____

Answer 24

• It is organized as bundles or sheets • Minimal vascularization and low myoglobin content – pale • Spindle shaped cells with gap junctions (Not fibers) • Cells 1-15µM in diameter, 25-300µM long • Actin and myosin bundles anchor at dense bodies • Indistinct SR • Gap junctions between cells • Autonomic nerve endings • No striations……………..No sarcomeres • NO T-TUBULES

Question 25

Smooth muscle cells relaxed and contracted.

Cytoplasmic filaments insert on __ __ located in the __ ___ and deep in the ____. Contraction of these filaments ____ the size of the ___ and promotes the contraction of the __ ___.

During the contraction the cell nucleus is ____.

Cells____ during Contraction due to ___ of ___

Answer 25

Smooth muscle cells relaxed and contracted. Cytoplasmic filaments insert on dense bodies located in the cell membrane and deep in the cytoplasm. Contraction of these filaments decreases the size of the cell and promotes the contraction of the whole muscle. During the contraction the cell nucleus is deformed. Cells twist during Contraction due to Anchoring of fibers

Question 26

Smooth Muscle is found in many locations ‘

____
___
____

Answer 26

Smooth Muscle is found in many locations Hair follicle, GI, Myometrium

Question 27

Skeletal Muscle Contraction

• Each ___ is innervated by a ____ of a ___ ___
• A Motor neuron innervates up to • ___ fibers.
• Neuron plus muscle fiber = • __ __ ___

___ __ ____contraction

• ___, ___ and ____ dependent upon:-

o ___ of ___ ___

o ___ of ___ __ ____

o ___ of ___

Answer 27

Skeletal Muscle Contraction • Each fiber is innervated by a Branch of a motor neuron. • A Motor neuron innervates up to • 100 fibers. • Neuron plus muscle fiber = • A MOTOR UNIT. • ALL OR NONE contraction • Strength, speed and duration dependent upon:- o Type of skeletal muscle o Number of motor units stimulated o Frequency of stimulation

Question 28

Depolarization

• At the motor end plate (arrows) ____ is released from the ___ ___, which fuse with the ___ ___ terminal, then discharged into the cleft, and bind to receptors on the ____ membrane causing depolarization.
• This signal passes along the ___, then deep into the muscle via __ ____

Answer 28

Depolarization • At the motor end plate (arrows) acetylcholine is released from the synaptic vesicles, which fuse with the nerve membrane terminal, then discharged into the cleft, and bind to receptors on the muscle membrane causing depolarization. • This signal passes along the membrane, then deep into the muscle via T-tubules.

Question 29

NOTE JUNCTIONAL FOLDS IN THE MUSCLE TO INCREASE ___ ___ AND AMOUNT OF___ ___.

ALSO NOTE T-TUBULE INVAGINATION FROM SARCOLEMMA

Answer 29

NOTE JUNCTIONAL FOLDS IN THE MUSCLE TO INCREASE SURFACE AREA AND AMOUNT OF ACH BINDING. ALSO NOTE T-TUBULE INVAGINATION FROM SARCOLEMMA

Question 30

The following sequence of events

• Depolarization at the ___ sensed by the ___

. • ____ released from the SR

• Calcium concentration____ (How much?) and binds to ___
• Causing ____change
• ___ ___ ____interacts with ___, myosin is ___, ATP ____
• Myosin ___ ___into _ band via a ratcheting motion
• Z-Z distance ____s, sarcomere shortens, I band ___ in width, A band ____
• Cyclic repeats occur until
• Calcium taken back into the ___ or ____ from the cell and muscle relaxes

Answer 30

The following sequence of events • Depolarization at the triad sensed by the SR. • Calcium released from the SR • Calcium concentration increases (How much?) and binds to TnC • Causing conformational change • Myosin head-ATP interacts with actin, myosin is activated, ATP hydrolyzed • Myosin pulls actin into A band via a ratcheting motion • Z-Z distance decreases, sarcomere shortens, I band decreases in width, A band constant • Cyclic repeats occur until • Calcium taken back into the SR or extruded from the cell and muscle relaxes

Question 31

Cardiac Muscle Contraction

• Heart rate is affected by ____ innervation of the ___ ____
• By stimulation of the ____ nerve
• By ____, adrenaline for example
• Contraction dependent upon __ ____ depolarizations and the integrity of ___ ___ (Cable theory).
• Basically the same ___ ___and ____ as is found in skeletal muscle but…………..
• So remember these points:

o ____ regulation, not necessarily ‘__ or ___’

o Intercalated discs, depolarization __ to ___

o No direct ___ ____(for the most part)

• ____ induced-calcium release. You’ll learn more about this In Physiology, but note that this phenomenon exists.

It is so named as calcium from ____ the cell has to pass into the cardiac ___ to induce calcium release from ___ ___

• Not necessary in Skeletal muscle

Answer 31

Cardiac Muscle Contraction • Heart rate is affected by autonomic innervation of the SA node • By stimulation of the vagus nerve • By hormones, adrenaline for example • Contraction dependent upon neighboring cell depolarizations and the integrity of Intercalated discs (Cable theory). • Basically the same muscle interactions and control as is found in skeletal muscle but………….. • So remember these points: o Troponin regulation, not necessarily ‘all or none’ o Intercalated discs, depolarization cell to cell o No direct nerve stimulation (for the most part) • Calcium induced-calcium release. You’ll learn more about this • In Physiology, but note that this phenomenon exists. It is so named as calcium from outside the cell has to pass into the cardiac fiber to induce calcium release from interior stores. • Not necessary in Skeletal muscle

Question 32

Purkinje Fibers Located in the ____ ventricular walls of the heart, just beneath the ____.

These fibers are specialized ____ fibers that conduct an ___ stimulus or impulse that enables the heart to ___ in a coordinated fas

Answer 32

Purkinje Fibers Located in the inner ventricular walls of the heart, just beneath the endocardium. These fibers are specialized myocardial fibers that conduct an electrical stimulus or impulse that enables the heart to contract in a coordinated fas

Question 33

Smooth Muscle Contraction

• Contraction is regulated by ____innervation (Another similarity to Cardiac muscle)
• Responds to____
• ___ contraction (Imagine the “wave-like” motion in GI peristalsis)
• Depolarization of the ____ causes the usual ____ increases And fluxes BUT the actin-myosin interaction is mediated through ____, so, there is NO ____ REGULATION.

Answer 33

Smooth Muscle Contraction • Contraction is regulated by autonomic innervation (Another similarity to Cardiac muscle) • Responds to hormones • Slow contraction (Imagine the “wave-like” motion in GI peristalsis) • Depolarization of the sarcolemma causes the usual calcium increases And fluxes BUT the actin-myosin interaction is mediated through CALMODULIN, so, there is NO TROPININ REGULATION.

Question 34

Smooth muscle cells relaxed and contracted. Cytoplasmic filaments insert on dense bodies located in the cell membrane and deep in the cytoplasm. Contraction of these filaments decreases the size of the cell and promotes the contraction of the whole muscle. During the contraction the cell nucleus is deformed. Twist during contraction

Answer 34

Smooth muscle cells relaxed and contracted. Cytoplasmic filaments insert on dense bodies located in the cell membrane and deep in the cytoplasm. Contraction of these filaments decreases the size of the cell and promotes the contraction of the whole muscle. During the contraction the cell nucleus is deformed. Twist during contraction