1.2 Gross & microscopic anatomy of muscles

functions of muscular tissue

• stabilize joints and maintain positions

• heat generation

• body movement

• storage and movement of substances within the body

properties of muscular tissue

• Electrical excitability –

responds to certain stimuli by producing

action potentials that travel along plasma

membrane. Stimuli:

electrical signals (heart) and

neurotransmitters from neurons.

• Contractility – ability to contract

forcefully when stimulated by an action

potential

• Extensibility – stretch

without being damaged

• Elasticity – return to original

length after contraction or extension

3 types of fascia and what they are

• epimysium- outermost layer, encloses entire layer

• perimysium- surrounds groups of 10-100 muscle fibers (aka fascicles)

• endomysium- innermost, separates individual fibers

What is fascia and hypodermis?

• Fascia- sheet of desne irregular connective tissue, holds muscles w similiar functions 2gether

• hypodermis- separates muscle from skin

the 2 kinds of hypodermis:

• areolar

• adipose (fat)

What is a tendon and its functions

An extension of epimysium, perimysium, & endomysium.

A cord of dense regular connective tissue

Attaches muscle to periosteum (bone)

Aponeurosis

flat, broad tendon

what does it mean that a muscle fiber is multinucleated

(result of fusion of tens of myoblasts); do not divide

Sarcolemma

plasma membrane (silver outermost layer)

Transverse (T) tubules

tunnels from sarcolemma to the center of the cell; filled with interstiitial fluid

Sarcoplasm

cytoplasm; contains glycogen and myoglobin (similar to hemoglobin)

Myofibrils

• contractile organelles

• contain thick and thin filaments (protein molecules)

(in the bottom in the middle-left middle of the image)

Sarcoplasmic reticulum (SR)

endoplasmic reticulum. SR stores and releases Ca 2+ (muscle contraction)

Thick and thin filaments

• bordered by the z-line

• arranged in compartments called sarcomeres

Z discs (line)

separate sarcomeres

H (A) band

thick filaments

H band = H zone

(only thick filaments) + 2 Zones of Overlap with thin filaments

I band

thin filament

M line

middle of the sarcomere

what results in the striation of muscles?

pattern of overlap of thin and thick filaments in a myofibril

What are the three kinds of proteins in myofibrils?

• contractile proteins

• regulatory proteins

• structural proteins

contractile proteins functions and components

• generate force in contractions

• myosin (motor protein)

• actin

regulatory protein functions and components

• switch contractions on/off

• tropomyosin, troponin (parts of thin filaments that change configuration in response to Ca2

structural protein functions and components

• holds filaments in place. Gives elasticity & extensibility

• titin- connects Z disc & M line

• a-actinin- attaches actin to titin molecules