Muscle Tissue Histology

Skeletal muscle myocytes are ______ and the nuclei are _______

multinucleated; pushed to the sides

_____ and _____ muscle are striated

skeletal; cardiac

Skeletal muscle cells are called _____

fibers

skeletal muscle cells have morphological and functional _______

syncytium

______ surrounds muscle fibers

endomysium

_______ surrounds fasicles

perimysium

______ surrounds muscles

epimysium

The connective tissue that surrounds muscle fibers and bundles is essential for ______ ______

force transduction

Classification of skeletal muscle is based on what 3 things`

contractile speed, enzymatic activity, metabolic profile

rate of contraction & relaxation

contractile speed

rate of ATP breakdown by myosin ATPase during contraction

enzymatic activity

capacity for ATP production by oxidative phosphorylation or glycolysis

metabolic profile

muscle fiber type adapted for long, slow/sustained contraction needed to maintain posture

Type I

fiber type with small diameter, red color, slow twitch, many mitochondria and myoglobin

Type I

Type I are ____ ____ fibers

slow oxidative

Type IIa fibers are ___ _____, _____ fibers

fast oxidative; glycolytic

fiber type with medium diameter, pink color high glycogen, and capable of anaerobic metabolism

IIa

Type IIb fibers are _____, ____ fibers

fast, glycolytic

fiber type that is large, white, have a fast twitch, high glycogen content, highly anaerobic with less myoglobin and mitochondria

Type IIb

In future classification , type IIb will be referred to as _______

Type IIX

The structural and functional subunit of the myofiber is the ______

myofibril

Myofibrils extend _____-

the full length of the fiber

Myofibrils are arranged into _______ that contain _________

sarcomeres; myofilaments

______ are the functional unit of the myofibril

sarcomeres

The region where thick filaments are found

A band

Region where ONLY thick filaments are found

H band

Area where ONLY thin filaments and a Z line are found

I band

What is found in the M line?

C protein flanking myomesin

A ___________ contains thin filaments from one sarcomere, while an ______ contains thin filaments and a z-disk from two sarcomeres

hemi-I-band; I-band

Morphology of actin

pair of helically entwined polymers of G-actin

Domains of the troponin complex and what they bind

TnI - actin

TnC - Ca2+

TnT - tropomyosin

Myosin II is made of 2 ______ chains and _____ light chains

heavy; 4

The myosin head as ____ activity

ATPase

A very large protein that anchors myosin filaments in the Z lines

titin

short, bipolar actin-binding protein, major component of Z line, anchors actin to Z line

a-actinin

an inelastic protein, lies parallel to actin and assists in stabilizing α-actinin/actin interaction at the Z line

nebulin

associated with the free end of actin, "caps" actin to regulate its length

tropomodulin

myosin binding protein, holds myosin filaments "in register" at the M line

myomesin

also a myosin binding protein, lies adjacent to myomesin, holds myosin filaments "in register" at the M line

C protein

a Z-line associated multi-protein structure that connects the sarcomeres to the extracellular matrix through the cell membrane (sarcolemma).

costamere

links actin to sarcolemma, is dysfunctional in muscular dystrophy

dystrophin

surrounds sarcomere at the Z-line attaching them to each other and to the sarcolemma

Desmin

cell membrane of a muscle fiber invested with an external (basal) lamina

sarcolemma

special form of smooth endoplasmic reticulum of a muscle fiber whos principal role is to sequester calcium during contraction

sarcoplasmic reticulum

SR is rich in _______

calsequestrin

terminal expansions of the SR proper that serve as reservoirs for calcium, enriched with voltage sensitive calcium channels

terminal cisternae

Triad =

1 t-tubule + 2 terminal cisternae

T-tubules align at the ______

A-band

In cardiac muscle, diads are located at the _____

z-bands

A single alpha motor neuron/axon and the skeletal muscle fibers it innervates

the motor unit

In muscles exhibiting fine control, one motor axon innervates ______ fibers compared to a muscle exhibiting coarse control

fewer

each muscle has _____ motor end plate

one

____ ____ contribute to high surface area

junctional folds

Sensory receptor that detects dynamic and static changes in muscle length that contains both afferent and efferent fibers

muscle spindle (fuse)

sensory receptor in the muscle that monitors tension developed in the muscle and contains afferent fibers only

golgi tendon organ

what does the golgi tendon organ prevent?

damage during excessive force generation

response to muscle spindle stimulation

reflex contraction

response to golgi tendon organ

reflex relaxation of muscle via interneuronal inhibition of alpha-motorneurons

type of motor neurons found in a fuse

y

Skeletal muscle develops from the fusion of single cells known as _____

myoblasts

______ originate in the embryo from mesoderm

myoblasts

_______ is another regulatory protein that negatively controls muscle growth and differentiation

myostatin

_____ cells migrate to the site of injury and help repair the muscle

satelite

Regenerating muscle fibers are reactive for _____ _____

embryonic myosin.

Cardiac muscle has ___ ____ regenerative capacity

almost no

cardiac cells to not form a true ____ ____

syncytial network

The sarcoplasm of cardiac muscle contains more ____, _____, and _____ than skeletal muscle

glycogen, lipid, mitochondria

Cardiac cells are joined to each other by _____ _____

intercalated disks

In cardiac muscle, ____ and _____ _____ are especially enriched at the poles of the nucleus in a region referred to as the _____ _____

mitochondria; glycogen granules; sarcoplasmic cone

Cardiac muscle has 1 or 2 nuclei located _____

centrally

intercalated discs have ______ and ______ portions with specific junctional specializations

transverse; lateral

the lateral portion of a intercalated disc =

gap junctions

The two junctional specializations of the transverse portion

fasciae adherens and maculae adherentes (desmosomes)

analogous to the zonulae adherens of epithelia to which actin filaments attach, anchoring sites for the thin filaments in the sarcomeres nearest the end of the cells

fasciae adherentes

bind cells to prevent separation during contraction

maculae adherentes

Cardiac muscle has _______ T tubules than those in skeletal muscle and are lined with an _____ _______

larger; external lamina

The sarcoplasmic reticulum of cardiac muscle is _____developed relative to the SR in skeletal muscle

poorly

Each cardiac cell T tubule is associated with ______ terminal cistern, forming dyads instead of triads

one

Cardiac muscle contains ______ mitochondria than skeletal muscle

more

In cardiac muscle, the SR leaks calcium ions into the sarcoplasm at a _____ and ______ rate which, with the calcium from the T tubules, contributes to an automatic rhythm

slow; constant

Cardiac mitochondria lie _____ relative to myofibrils

parallel

Atrial granules are found in ______ ______ muscle cells

atrial cardiac

Atrial granules contain the hormones _____ ______ ______ and ____ ____ _____, which are both diuretic hormones

atrial natriuretic factor; brain natriuretic factor

There is no _____ on cardiac cells

NMJ

Purkinje fibers are _____ _____ ____ ______ located in the ____________

modified cardiac muscle cells; bundle of His

Purkinje fibers have _____ gap junctions, and ____ content of myofibrils and _____ content of glycogen

more; lower; higher

Smooth muscle cells can _______ and secrete ____ ____

divide; CT matrix

In smooth muscle, most of the sarcoplasm is occupied by thin actin filaments which insert into ____ _____

dense plaques

smooth muscle nuclei exhibit a ____-____ shape and is deeply ____ in longitudinal sections of contracted smooth muscle

cork-screw; indented

T/F smooth muscle contains myosin II

true

in smooth muscle myosin II molecules are oriented _______ on one side and _______ on the other side

in one direction; in the opposite direction

There is no _____ in smooth muscle

troponin

Thin filaments of smooth muscle contain what 4 things?

actin, tropomyosin, caldesmon, calponin

in SM, _______ binds ______. This binds to _______, which phosphorylates ATP, which enables _____

Ca++; calmodulin; MLCK; myosin cross-binding with action and the contractile cycle

_______ ______ are functionally comparable to ______ _____

dense bodies; Z-discs

intermediate filaments of cardiac muscle

desmin and vimentin

in smooth muscle, both actin/myosin and intermediate filaments insert into _____ _____

dense plaques

the slower contractile time of smooth muscle can be attributed in part to slower______

ATP hydrolysis

cells located between epithelium and basal lamina, in ductal portions of certain types of glands

myoepithelial cells

In lacrimal glands, contraction of myoepithelial cells is initiated by _____

Ach