Joints and the muscular system

The muscular system

The human body has >600 distinct skeletal muscles

The face includes 60 muscles and >40 are used to frown and 20 are used to smile

Functions of muscle tissue

Movement- Walking, running, talking

Stabilising body positions- Standing, sitting, keeping head up

Regulating organ volumes- Sustained contraction of sphicters to prevent outflow from hollow organs

Movement of substances- Contraction/ relaxation of muscles in blood vessels, gastrointestinal tract, reproductive system, cardiac muscles for blood flow​

Heat production – contraction of muscle tissues, involuntary contractions of skeletal muscle (shivering)​

Properties of Muscle Tissue​

• Excitability – respond to chemicals released from nerve cells​

• Conductivity – ability to propagate electrical signals over membrane​

• Contractibility – ability to contract and generate force​

• Extensibility – ability to be stretched without damaging the tissue​

• Elasticity – ability to return to original shape after being stretched ​

Types of Muscle Tissue​

Skeletal muscle tissue – attached to bones of skeleton​

Smooth muscle tissue – forms the walls of hollow internal structures​

Cardiac muscle tissue – forms the wall of the heart​

Skeletal muscle

• Typically attach to bones, skin or fascia​

• Conscious control of muscles (voluntary muscle tissue)​

• Cells are long and threadlike with alternate light and dark cross-markings called striations​

• Cells are multinucleated​

• Skeletal muscles move the head, trunk and limbs​

Smooth muscle

• Shorter than skeletal muscle cells and are spindle shaped​

• Cells do not have striations (unlike skeletal muscle cells) = smooth​

• Cells are mononucleated​

• Found in walls of hollow internal organs (stomach, intestines, urinary bladder, uterus, blood vessels)​

• Involuntary ​

Cardiac muscle

• Found only in the heart & makes up the bulk of the heart​

• Cells are striated and branched, joining end to end and form complex networks​

• Cells are mononucleated​

• Involuntary​

isometric contraction

When there is a muscle contraction without motion. They are used to stabilize a joint, when a weight is held at waist level neither raising nor lowering it. Dynamic contractions are muscle contractions with a fixed amount of weight.

Isotonic contraction

A contraction when a muscle shortens to overcome resistance. When a muscle shortens, at least one joint moves, and body movement occurs. The resistance can come from lifting a weight, pulling up your body, or from some other object such as when you lift a bag of groceries.