Chapter 8

The Muscular System

Types of Muscle

• Smooth

• Cardiac

• Skeletal

Types of Muscle

• Smooth muscle– Walls of hollow body organs (digestive,

respiratory, uterus, bladder) & blood vessels– Involuntary– Tapered at ends– Lack striations– Single nucleus– Slow contraction/relaxation

Types of Muscle

• Cardiac muscle– Heart walls– Involuntary– Are striated– Intercalated discs

allow electrical impulses

to rapidly travel

Types of Muscle

• Skeletal muscle– Striated– Multiple nuclei– Voluntary– Mostly attached to bones– Some attached to muscles & skin

Muscular System

• 3 primary functions of Skeletal muscles– Movement of skeleton– Maintenance of posture

• Muscle tone

– Generation of heat• shivers

Muscular System

• Structure– Muscle cell (Muscle fiber/myofibril)

• Wrapped in endomysium

– Fascicle• wrapped in perimysium

– Muscle• Wrapped in epimysium• Part of deep fascia• Merge to form tendons

Muscular System

• Motor impulses travel away from CNS– (sensory impulses travel toward)

• Each single motor neuron carries signal to hundreds of muscle fibers. – Motor unit

• Connects to muscle at neuromuscular junction

• Neuromuscular Junction – Type of synapse– Synaptic cleft– Neuron releases neurotransmitter

(acetylcholine, ACh)– Muscle cells have receptors for ACh.– Motor end plate– Initiates action potential

Muscular System

Muscular System

• Contraction– Numerous filaments in each muscle cell made

of actin and myosin proteins, giving the cell striated appearance

– Sarcomere—subunit of skeletal muscle=band of myosin and actin on either side

Muscular System

• Troponin & Tropomyosin– Calcium binds to troponin & molecules allow

binding of actin & myosin– Calcium stored in the sarcoplasmic reticulum

Muscular System

1. ACh released from neuron2. Binds to motor end plate, action potential3. A P travels to sarcoplasmic reticulum4. Calcium is released5. Attaches to troponin, actin binding sites open6. Myosin heads bind to actin7. Pull actin filaments together8. ATP used to detach myosin heads and move

them back to position9. Muscle relaxes as Ca stored in SR.

Muscular System

• Myoglobin– Stores O2

• Glycogen– Glucose chain for storage

• Creatine phosphate– Makes more ATP when it’s used up

Muscular System

• Muscle tone is the contracted state when not in use– Isotonic contractions—tone remains the

same, length changes – Isometric contractions—length remains the

same, tone changes

Muscular System

• Tendons connect muscle fascia to the periosteum of bones in (generally) two places

• Less movable is the origin

• More movable is the insertion

• Prime movers

• Antagonists

• Synergists

Muscles•Trapezius

•Latissimus dorsi

•External oblique

•Deltoid

•Triceps brachii

Muscles •Sternocleidomastoid

•Pectoralis major

•Pectoralis minor

•Rectus Abdominis

•Deltoid

•Biceps brachii

•Brachioradialis

•Flexor carpi ulnaris

•External/Internal obliques

Muscles•Quadriceps femoris

•Rectus femoris

•Vastus lateralis

•Vastus medials

•Vastus intermedius

•Sartorius

•Gracilis

•Tibialis anterior

•Gluteus maximus

•Hamstrings

•Semimembranosus

•Semitendinosus

•Biceps femoris

•Gastrocnemius

•Diaphragm

•Intercostals

•Internal

•External

Muscular disorders

• Muscular dystrophy– Deterioration of muscles with intact nerve functions– Cardiac muscles failure results in death

• Myasthenia gravis– Muscular fatigue caused by slightest exertion

• Fibromyalgia, fibromyositis– Myalgia-muscle pain– Myositis-muscle inflammation– Fibrositis-inflammation of connective tissue

1. What type of muscle

tissue is characterized

by intercalated discs?

2. What type of muscle tissue is characterized by cells with multiple nuclei and striations?

3. The site where the

axon from a motor neuron

meets the motor end plate

of a muscle cell is called

the __________ junction

4. The neurotransmitter

sent from the neuron to

receptors in the motor

end plate is called what?

5. What is the filament called that causes the appearance of the dark band in the striation pattern?

6. What is the thin filament that causes the appearance of the light band in the striation pattern?

7. What is stored in the sarcoplasmic reticulum that binds to troponin, causing tropomyosin to move and allow myosin to bind to actin?

8. A muscle that works against a prime mover is called an ________.

9. What is this muscle?

10. What is this muscle?