Overview of Muscle Tissues

What are the 3 types of cells in muscle tissue?

skeletal, cardiac, and smooth muscle

What function do all three muscle tissue types share in common

generating a force called muscle tension

What are other major functions of muscle tissue?

• Movement - moves skeleton or skin

• Posture maintenance - supports and stabilizes body position

• support of soft tissues - abdominal muscles help maintain organ position/stabilize joints

• thermogenesis - maintain body temp.; heat generation (shivering)

• nutrient storage - regulates flow of materials in hollow organs and can store proteins/calcium

Muscle tissue consists of muscle cells called _

myocytes

What is the ECM called and its function?

Endomysium

• holds muscle cells together within muscle tissue and transmits tension generated by muscle cells to neighboring forms

Endomysium

loose connective tissue surrounding each muscle fiber

• provides structural support and facilitates communication between muscle cells.

Perimysium

connective tissue around fascicles that groups muscle fibers into bundles

• provides support and protection.

Fascicle

a group of muscle fibers surrounded by perimysium

• functions to organize and support bundles of muscle fibers, allowing for efficient force generation.

Epimysium

a loose (areolar) connective tissue surrounding the entire muscle organ

• provides protection and support, as well as serving as a conduit for nerves and blood vessels

What is a fascia?

a strong CT that surrounds muscle groups (organs)

ex: Quadriceps → group of four muscles

What does endomysium contain?

blood vessels and nerves that are located in the perimysium. also contains collagen fibers from CT that connects tendons to muscles, reinforcing strength

The perimysium and epimysium fuse together at the end of the muscle to form a _

tendon

• equal tension produced on the tendons

What muscle tissues are striated?

skeletal & cardiac muscle tissue

What are skeletal muscle cells/muscle fiber characteristics and location?

• multinucleated

• voluntary contraction

• long and striated

• parallel arranged muscle cells

LOCATION: mostly attached to bones of the skeleton by CT

What is the function of skeletal muscle?

produces movement of the body

What are cardiac cells characteristics and its location?

• short and wide

• highly branched

• 1-2 nuclei

• intercalated discs (specialized cell connections that prevent the cell from separating)

• involuntary controlled

• coordinated contractions

LOCATION: the heart

What is the function of cardiac muscle?

produces beating of the heart

What are smooth muscle characteristics?

• no striations

• single central nucleus

• long and flat

• found lining hollow organs, eye, skin, and some glands

• involuntary controlled

LOCATION: walls of hollow organs, as well as in the skin+eyes

What is the function of smooth muscle?

• changes diameter of hollow organs

• causes hairs to stand erect

• adjusts the shape of the lens and the size of the pupil of the eye

What are the 5 properties of muscle cells?

1. contractibility

2. excitability

3. conductivity

4. distensibility

5. elasticity

Define contractibility

the ability to contract. contractions doesn’t necessarily mean it shortens (like sarcomeres)

Define excitability

responsive to various stimuli, including chemical (from nervous or endocrine systems), mechanical (stretch signals), or local (electrical) signals. generates electrical changes across plasma membrane of muscle cell

• graded potential or action potential

What does an excitable tissue/cell mean?

a tissue/cell capable of generating and transmitting an electrical impulse along their membrane in response to a stimulus

Define conductivity

when muscle cells are excited, electrical changes in the plasma membrane do not stay in one place. they are RAPIDLY conducted along the entire plasma membrane (the ability to transmit electrical signals across the membrane)

Define distensibility

the ability for cells to be stretched up to 2-3 times their resting length without rupturing

Define elasticity

the ability for muscle cells to return to their original shape after being stretched. *they don’t stretch*

What are myocytes?

Specialized cells that make up muscle tissue, also known as muscle fibers

What is sarcoplasm?

The cytoplasm of muscle cells

• contains cylindrical organelles called myofibrils (all 3 muscle types have myofibrils; arranged differently)

What is sarcolemma?

The plasma membrane of myocytes (muscle cell)

• plays a key role in muscle contraction and action potential propagation

composed of a phospholipid bilayer with multiple specialized integral and peripheral proteins

What are myofibrils?

cylindrical organelles found in all muscle types. made of bundles of proteins that allow for contraction

What is sarcoplasmic reticulum?

modified smooth ER that forms a web-like network surrounding myofibrils

• stores calcium ions and regulates calcium release during contractions