Chapter 7 The Muscular System

Types of Muscle Smooth Cardiac Skeletal

Smooth Muscle Makes up walls of hollow body organs, respiratory passageways Involuntary movement Cell structure Tapered ends Single, central nucleus No visible bands (striations) Stimulated by nerve impulses, hormones, stretching

Cardiac Muscle Makes up wall of heart Involuntary movement Cell structure Branching interconnections Single, central nucleus Striated Membranes are intercalated disks Stimulated by electrical impulses, nervous stimuli, hormones

Skeletal Muscle Attached to bones, muscles, or skin Voluntary movement Cell structure Long and cylindrical Multiple nuclei per cell Heavily striated Stimulated by nervous system

Checkpoint 7-1: What are the three types of muscle? Smooth Cardiac skeletal

The Muscular System Skeletal muscle has three primary functions Skeletal movement Posture maintenance Heat generation

Checkpoint 7-2: What are the three main functions of skeletal muscle? Skeletal movement Posture maintenance Heat generation

Structure of a Muscle Connective tissue layers Tendon Endomysium Around individual fibers Perimysium Around fascicles (bundles of muscle fibers) Epimysium Over entire muscle Part of deep fascia Tendon Attaches muscle to bone

Structure of a skeletal muscle. ZOOMING  IN • What is the innermost layer of connective tissue in a muscle? The endomysium What layer of connctive tissue surrounds a fascicle of muscle fibers? The perimysium

Muscle Cells in Action Motor unit is a single neuron and all the muscle fibers it stimulates Neuromuscular junction (NMJ) Neurotransmitter Synaptic cleft Receptors Motor end plate

Nervous stimulation of skeletal muscle.

Neuromuscular junction (NMJ).

Checkpoint 7-3: Muscles are activated by the nervous system Checkpoint 7-3: Muscles are activated by the nervous system. What is the name of the special synapse where a nerve cell makes contact with a muscle cell? The neuromuscular junction Checkpoint 7-4: What neurotransmitter is involved in the stimulation of skeletal muscle cells? Acetylcholine

Properties of Muscle Tissue Excitability Action potential Contractility Actin Myosin Sarcomere ATP

Electron microscope photograph of skeletal muscle cell (x6500).

Sliding filament mechanism of skeletal muscle contraction. ZOOMING  IN • Do the actin or myosin filaments change in length as contraction proceeds? They do not change in length, they overlap more

Checkpoint 7-5: What are two properties of muscle cells that are needed for response to a stimulus? Excitability and contractility Checkpoint 7-6: What are the filaments that interact to produce muscle contraction? Actin and myosin

The Role of Calcium Stored in endoplasmic reticulum (ER) Is released when nerve fiber stimulates muscle cell Attaches to proteins blocking receptor sites Allows cross-bridges to form between actin and myosin Returns to endoplasmic reticulum

Role of calcium in muscle contraction.

Energy Sources Muscle contraction requires energy (ATP) Generated by oxidation of glucose or other usable nutrient Compounds stored in muscle cells for energy production Myoglobin Stores reserves of oxygen Glycogen Storage form of glucose Creatine phosphate Stores energy

Checkpoint 7-7: What mineral is needed to allow actin and myosin to interact? Calcium Checkpoint 7-8: Muscle cells obtain energy for contraction from the oxidation of nutrients. What compound is formed in oxidation that supplies the energy for contraction? ATP

Oxygen Consumption Aerobic metabolism Anaerobic metabolism Requires oxygen Used during normal activities Anaerobic metabolism Does not require oxygen Used during strenuous activity Less ATP produced Lactic acid accumulates Oxygen debt develops Recovery oxygen consumption needed

Checkpoint 7-9: When muscles work without oxygen, a compound is produced that causes muscle fatigue. What is the name of this compound? Lactic acid

Effects of Exercise Improved balance, joint flexibility Increase in muscle size (hypertrophy) Improvements in muscle tissue Vasodilation Strengthened heart muscle Improved breathing and respiratory efficiency Weight control Stronger bones

Types of Muscle Contractions Partial (muscle tone or tonus) Isotonic No change in tension Muscle length shortens Movement Isometric Great increase in tension Muscle length unchanged No movement

The Mechanics of Muscle Movement Tendons attach muscles to bones Origin—attached to more fixed part of skeleton Insertion—attached to more moveable part of skeleton

Muscle attachments to bones. ZOOMING  IN • Does contraction of the biceps brachii produce flexion or extension at the elbow? Flexion

Checkpoint 7-10: Muscles are attached to bones by means of tendons: one attached to a less movable part of the skeleton and one attached to a movable part. What are the names of these two attachment points? The less movable part is the origin. The more movable part is the insertion.

Muscles Work Together Many muscles function in pairs Prime movers Produce given movement Synergists Assist prime movers Antagonists Oppose a given movement

Checkpoint 7-11: Muscles work together to produce movement Checkpoint 7-11: Muscles work together to produce movement. What is the name of the muscle that produces a movement as compared with the muscle that produces an opposite movement? The prime mover produces a movement and the antagonist produces the opposite movement

Levers and Body Mechanics Musculoskeletal system as a lever system Lever—bone Fulcrum—joint Force—applied by muscle Three classes of levers First class Second class Third class—most body movements

Levers

Checkpoint 7-12: Muscles and bones work together as lever systems Checkpoint 7-12: Muscles and bones work together as lever systems. Of the three classes of levers, which one represents the action of most muscles? Third class – the fulcrum is behind the point of effort and the weight

Skeletal Muscle Groups Characteristics for naming muscles (often combined) Location Biceps brachii Size Gluteus maximus Shape Trapezoid Direction of fibers Transversus abdominus Number of heads (attachment points) Triceps brachii Action Extensor carpi ulnaris

Superficial muscles, anterior view

Superficial muscles, posterior view

Muscles of the Head Facial expression (orbicularis) muscles Orbicularis oculi Orbicularis oris Levator palpebrae superioris Buccinator Mastication (chewing) muscles Temporalis Masseter Tongue Intrinsic Extrinsic

Muscles of the head ZOOMING IN • Which of the muscles in this illustration is named for a bone it is near? Frontalis, nasalis, mentalis and temporalis

Muscles of the Neck Are ribbonlike Extend up, down, or obliquely Extend in several layers in a complex manner Main one is sternocleidomastoid

Muscles of the Upper Extremities Position the shoulder Move the arm Move the forearm and hand

Muscles That Move the Shoulder and Arm Trapezius Latissimus dorsi Pectoralis major Serratus anterior Deltoid Rotator cuff Supraspinatus Infraspinatus Teres minor Subscapularis

Muscles That Move the Forearm and Hand Biceps brachii Brachioradialis Triceps brachii Flexor carpi Extensor carpi Flexor digitorum Extensor digitorum

Muscles that move the forearm and hand

Muscles of the Trunk Breathing muscles Abdominal muscles Pelvic floor muscles Deep back muscles

Muscles of Respiration Diaphragm Intercostal muscles

Muscles of respiration

Checkpoint 8-13: What muscle is most important in breathing? The diaphragm

Muscles of the Abdomen and Pelvis External oblique Internal oblique Transversus abdominis Rectus abdominis Levator ani

Muscles of the abdominal wall

Muscles of the female perineum (pelvic floor)

Checkpoint 7-14: What structural feature gives strength to the muscles of the abdominal wall? The fibers of the muscles of the abdominal wall run in different directions.

Deep Muscles of the Back Erector spinae Deeper muscles in the lumbar area

Muscles of the Lower Extremities Among the longest and strongest in the body Specialized for locomotion and balance

Muscles That Move the Thigh and Leg Gluteus maximus Gluteus medius Site of injection of many medications Iliopsoas Adductors Sartorius Hamstrings

Muscles of the thigh

Muscles That Move the Foot Gastrocnemius Achilles tendon Soleus Tibialis anterior Peroneus longus Flexor and extensor muscles

Muscles that move the foot

Effects of Aging on Muscles Beginning at about age 40 Gradual loss of muscle cells Loss of power Tendency to flex hips and knees Decrease in height