Muscular System Review

Overview of Anatomy and Physiology Functions of the muscular system – Motion – Maintenance of posture and Shape to body – Production of heat – Support-blood vessels, nerves – Protection-organs

Muscular System – Muscle fibers and tendons, innervated by nerves – Various size and shapes-relate to function – Muscle fibers are covered by connective tissue: Epimysium, Perimysium, and Endomysium – 3 coverings join together to form a tendon which attaches the muscle to bone – Agonist pairs – Action: contract or shorten

Muscle Movement Voluntary – Attached to bone – Moved by person Involuntary – Within organs – Not controlled by person

Types of Muscle Smooth muscle – Involuntary, wavelike motions – Not striated, one central nucleus per cell – Makes walls of hollow body organs Blood vessels Respiratory passages – Relaxes slowly, can sustain contraction

Types of Muscle Cardiac muscle – Involuntary, – Makes wall of heart – Striated, one nucleus per cell, branching interconnections – Electrical stimulus is generated within (self- excitatory), but can be modified by nervous stimuli and hormones

Types of Muscle Skeletal muscle – Voluntary control – Heavily striated – Multiple nuclei per cell – Contraction stimulated by nervous system – Contracts and relaxes rapidly – Attached to bones – Act in groups to produce movement

Muscle Groups Head & face Trunk Upper Extremeties Lower Extremeties

Figure 44-5 Anterior view of the body (

Figure 44-6 Posterior view of the body

Overview of Anatomy and Physiology Nerve and blood supply – Blood vessels provide a constant supply of oxygen and nutrition and nerve cells/fibers supply a constant source of information

Overview of Anatomy and Physiology Impulse from nerve cells travels across the synaptic cleft, filled with tissue fluid, as nerve and muscle cells do not directly touch each other. Acetylcholine, a special chemical neurotransmitter, travels through the fluid to stimulate the muscle fiber. Cholinesterase (enzyme) breaks down the acetylcholine after it has transferred the message and allows the muscle cell to relax.

Muscle Stimulation Two properties of muscle needed for response to a stimuli – Excitability – Contractility

Muscle Contraction Muscle contraction – Muscle stimulus—when a muscle cell is adequately stimulated, it will contract – Muscle tone—skeletal muscles are in a constant state of readiness for action – Types of body movements—flexion, extension, abduction, adduction, rotation, supination, pronation, dorsiflexion, and plantar flexion

Muscle Contraction Muscle stimulus “All or none law” Muscle Cell Stimulated or Shocked Muscle Contracts Completely All or None?

Think about muscle tone… No Muscle Tone – Paralyzed muscle – Flaccid—(weak, soft, flabby, & lack normal tone) – Limp – Atrophied—(wasted) –  Cells no longer receive stimuli from nerves

Muscle Excitability Muscles transmit electrical current along cell membrane The spreading electrical current is called action potential (calls muscle into action)

Muscle Contractility Ability to change shape – Shorten – Get thicker

Role of Calcium Nerve stimulation releases calcium into cell to cause contraction When stimulation stops, calcium is returned to the endoplasmic reticulum, and the muscle relaxes

Physiology Muscle Contraction Circulation- brings O 2, glucose, nutrients to cells O 2 is stored in muscle cells as myoglobin Glucose is stored in cells as glycogen for later breakdown into glucose when needed (as in vigorous exercise) Glucose and O 2 oxidize/burn to produce ATP needed for contraction Lactic Acid – Waste product of cellular metabolism – Causes muscle fatigue

Oxygen Debt Glucose & O 2 from circulation used first, then stored glucose & O 2 are used, both operate in an aerobic process (with O 2 ) If can’t breathe fast enough to provide O 2, glucose is burned in an anaerobic process (without O 2 ) causing lactic acid build up, muscle fatigue Exercising stops, breathing continues until oxygen debt is paid

Exercise Causes vasodilation, allowing increased nutrients to be carried to muscles Temporary increases strengthen the heart muscle and improve circulation Regular exercise increases respiratory efficiency through enhanced gas exchange With athletic training oxygen debt is delayed Bones & muscles get stronger, decreased weight, blood pressure, & heart attacks

Types of Movement

Flexion Decreases angle between two adjoining bones Angle decreased

Extension Increases the angle between two adjoining bones If the extension angle is more than 180 degrees - hyperextended

Abduction Extremity away from the midline of the body

Adduction Movement of extremity toward the axis of the body

Dorsiflexion Causes the top of the foot to elevate or tilt upward

Plantar Flexion Bottom of foot directed downward

Supination and Pronation Hand and forearm moves palm upward or downward