muscle tissue

3 types of muscle

• skeletal

• smooth

• cardiac

function of skeletal

• generate force by contraction

• mechanical protection

• thermogenesis

• venous blood flow

• endocrine myokines

function of endocrine myokines

regulate

• fat storage

• bone health

• cognitive functions

• inflammatory state

parts of muscle tissue

1. myofilaments - actin and myosin

2. myofibril

3. muscle fiber

4. fascicle

5. muscle

parts of connective tissue

1. endomysium

2. perimysium

3. epimysium

myosatellite cells

stem cells found in mature muscle

function of satellite cells

proliferate as skeletal myoblasts and undergo myogenic differentiation in response to mechanical strain or pathology

morphology of satellite cells

• small with high nuclear-to-cytoplasmic ratio

endomysium

connective tissue that wraps each individual muscle fiber/myocyte/muscle cell

perimysium

connective tissue that wraps bundles of muscle fibers/fascicles

epimysium

connective tissue that wraps around whole muscle

function of endo-, peri-, and epimysium

protects muscles from friction against other muscles and bones during contraction and transfers those forces to bones

structure of muscle layers

• endomysium is continuous with perimysium

• perimysium is continuous with epimysium

• epimysium is continuous with tendons

tissue of endomysium

loose connective tissue

tissue of perimysium

dense irregular connective tissue

epimysium

dense irregular connective tissue

tendon

dense regular connective tissue

what is the basic unit of muscles

sarcomere

myoglobin

• iron and oxygen binding protein found in sarcoplasm of skeletal and cardiac muscle

• reservoir of oxygen in muscle

what are the two types of muscle cells

1. slow-twitch red type 1

2. fast-twitch white type 2

characteristics of slow twitch red type I

• high concentration of mitochondria and myoglobin

• aerobic metabolism and fatigue resistance

• prolonged submaximal exercise activities

• surrounded by more capillaries

• less force and are slower to produce maximal tension

• stabilization and postural control

characteristics of fast-twitch white type II

• lower concentrations of mitochondria, myoglobin and capillaries

• mor actin and myosin filaments

• quicker to fatigue

• larger sized fibers

• produce greater and quicker force

• used for power activities

smooth muscle characteristics

• involuntary and visceral

• internal organs

• highly regenerative

• can proliferate to regenerate tissue

steps of peristalsis

1. contraction of circular muscles behind food mass

2. contraction of longitudinal muscles ahead of food mass

3. contraction of circular muscle layer forces food mass forward

what controls smooth muscle

• no innervation required

• under influence of autonomic, hormonal, and local metabolite control

structure of smooth muscle

• myocytes - fusiform shape

• single nucleus in center

contractions of smooth muscle

• sustained

• forceful

• greater force for less ATP

where is cardiac muscle located

myocardium of heart wall

characteristics of cardiac muscle

• forceful

• cont. contraction

• controlled by autonomic

• involuntary

• striated muscles

• very limited regeneration

• vascular

• endocrine function

what are contractile waves coordinated by

purkinje fibers

cardiomyocytes features

• central nuclei

• single or bi-nucleated

• striated structure

• fiber ends branch longitudinally

function of intercalated discs

• contractile anchors between adjacent muscle cells

• rapid conduction of depolarization

components of intercalated discs

• fascia adherens

• desmosomes

• gap junctions

function of fasci adherens

• anchoring sites for actin

• connect to closest sarcomere - z line

desmosomes

anchor cells to each other via intermediate filaments

gap junctions

allow action potentials to spread between cardiac cells by permitting passage of Ca+ ions between cells leading to depolarization of heart muscle

lipofusin

red/brown pigment that accumulates in cardiac muscles