Anatomy & Physiology Chapters 9-10

3 Types of Muscle Tissue

Skeletal

Smooth

Cardiac

Characteristics of muscle

excitability

contractility

extensibility

elasticity

Excitability

Muscle's ability to respond to nerve signals

Contractility

The characteristic of muscle that allows for movement

Extensibility

Muscle's ability to stretch without damage

Elasticity

Muscle's ability to return to original shape

Thermogenisis

Muscular generation of heat, usually occurring through shivering.

Functions of muscle

Produce movement

Maintain posture

Stabilize joints

Generate heat (thermogenesis)

Organization of muscle

Muscle (largest)

Fascicles

Muscle cells/fibers

Myofibrils

Myofilaments (thick and thin) (smallest)

Epimysium

Dense connective tissue that wraps around entire muscle.

Perimysium

Connective tissue layer that contains collagen & elastic fibers, blood vessels & nerves. Wraps the fascicles.

Fascicle

Bundle of muscle fibers.

Endomysium

Collagen fibers that wrap each muscle fiber.

Tendon

The epimysium, perimysium, and endomysium extend beyond the muscle to form this structure which connects muscle to bone.

Structure of a muscle cell

Sarcolemma

Sarcoplasmic Reticulum

T-tubule

Mitochondria

Myofibril

Sarcolemma

The plasma membrane of the muscle cell.

T-tubules

Tunnel-like extensions of sarcolemma.

Sarcoplasm

Cytoplasm of the muscle cell; contains numerous mitochondria

Sarcoplasmic Reticulum (SR)

Smooth ER of a muscle cell; membrane enclosed tubules that store calcium required for contraction.

Myoglobin

Reddish pigment similar to hemoglobin which stores O2.

Mitochondria

The energy factory of the muscle cells, which produce ATP.

Myofibrils

Rod-like, densely-packed, structures that run parallel to the length of the muscle fiber. Account for 80% of cellular volume.

Myofilaments

Orderly arrangement of small structures (smaller than the myofibrils) within sarcomeres. Thick filaments = A-band, myosin; Thin filaments = I-band, actin.

I-band

Consists only of the thin filament, actin.

A-band

The entire length of thick filament, myosin.

H-zone

The lighter region at the center/midline of each A-band; does not contain myosin heads.

Z-disc

Attach to myofilaments by the protein, titin. The dark area, midline interruption of the light I-band.

sarcomere

The region of a myofibril between two successive Z discs. The smallest, basic, functional unit of a muscle fiber.

muscle fiber

A muscle cell.

Events at the neuromuscular junction (NMJ)

1. Action potential arrives at axon terminal of motor neuron.

2. Voltage-gated Ca2 channels open. Ca2 enters the axon terminal moving down its electrochemical gradient.

3. Ca2 entry causes ACh to be released by exocytosis.

4. ACh diffuses across the synaptic cleft and binds to its receptors on the sarcolemma.

5. ACH binding opens ion channels in the receptors that allow simultaneous passage of Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter than K+ ions exit, which produces a local change in the membrane potential called the end plate potential.

6. ACh effects are terminated by its breakdown in the synaptic cleft by acetylcholinesterase an diffusion away from the junction.

Excitation-Contraction Coupling

1. The action potential propagates along the sarcolemma and down the T-tubules.

2. Calcium ions are released.

3. Calcium binds to troponin and removes the blocking action of tropomyosin.

4. Contraction begins: Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins. E-C coupling is over.

actin subunits

Kidney shaped, polypeptide subunits, which are active sites for myosin attachment during contraction.

tropomyosin

Polypeptide strands of rod-shaped protein that spiral about the actin and help to stiffen and stabilize. They block myosin-binding sites on the actin so myosin heads cannot bind to the thin filaments.

troponin

The major protein in the thin filaments, a globular three-polypeptide complex. One of the polypeptides binds to calcium ions and exposes the myosin-binding sites on the actin for contraction.

myosin

Found in the thick filament, consists of two heavy and four light polypeptide chains, and a rod-like tail attached by a flexible hinge to two globular heads that link the thick and thin filaments together (cross bridge) during contraction.

anaerobic

Muscular metabolism without O2 respiration, where glycogen converts to glucose which converts to lactic acid, and yields only 2 ATP.

aerobic

Muscular metabolism where O2 can be obtain either from myoglobin or through respiration. Pyruvate and O2 enter the mitochondria and heat, CO2, and H2O are released along with 36 ATP.

Prime mover

A muscle that has the major responsibility for producing a specific movement. The agonist.

Antagonist

Muscles that oppose, or reverse, a particular movement.

Synergist

Muscles that help prime movers by adding a little extra force to the same movement and reduce undesirable or unnecessary movements that might occur as the prime mover contracts.

Fixator

When synergists immobilize a bone, or a muscle's origin so that the prime mover has a stable base on which to act.

Origin

A muscle's fixed or immovable point of attachment.

Insertion

A muscle's attachment on the movable bone.

Neck muscles

Sternocleidomastoid

Trapezius

Sternocleidomastoid

Causes flexion of the neck.

Trapezius

Elevates the shoulder.

temporalis; masseter

Head muscles that elevate the mandible to close the jaw.

Facial muscles

Orbicularis oculi

Zygomaticus

Orbicularis oris

Epicranius

Orbicularis oculi

Closes the eyelids; acts during squinting and blinking.

Zygomaticus

Raises corner of the mouth for smiling

Orbicularis oris

closes and protrudes lips as in speaking, kissing and whistling.

Shoulder muscle

Deltoids

Trapezius

Infraspinatus

Deltoids

Causes flexion, extension, abduction, and adduction of the arm.

Arm muscles

Triceps brachii

Brachialis

Biceps brachii

Triceps brachii

Causes the extension of the forearm.

Brachialis

Causes flexion of forearm.

Biceps brachii

Causes flexion of forearm and arm.

Forearm muscles

Brachioradialis

Flexor carpi radialis

Palmaris longus

Extensor carpi radialis longus

Extensor digitorum

Flexor carpi ulnaris

Extensor carpi ulnaris

Brachioradialis

Causes flexion of forearm.

Flexor carpi radialis

Causes flexion and abduction of wrist.

Palmaris longus

Causes flexion of the wrist.

Flexor carpi ulnaris

Causes flexion and adduction of wrist.

Extensor digitorum

Causes extension of wrist and fingers.

Extensor carpi radialis longus

Causes extension and abduction of wrist.

Thorax/Chest muscles

Pectoralis minor

Pectoralis major

Serratus anterior

Intercostals

Pectoralis minor

Causes depression of scapula

Pectoralis major

Causes flexion and adduction of arm.

Serratus anterior

Holds scapula against thoracic wall.

Intercostals

Elevate ribs during inhalation (external) and depress ribs during exhalation (internal).

Back muscles

Rhomboid major

Latissimus dorsi

Rhomboid major

Elevates the scapula.

Latissimus dorsi

Causes extension and adduction of arm.

Abdomen muscle

Rectus abdominus

External & internal obliques

Transverse abdominus

Rectus abdominus

Causes flexion of vertebral column; stabilizes pelvis during walking.

External and internal obliques

Causes rotation and lateral flexion of trunk.

Pelvis muscles

Gluteus medius

Gluteus maximus

Iliopsoas

Iliotibial tract

Pectineus

Gluteus medius

Causes abduction of thigh; stabilizes pelvis during walking.

Gluteus maximus

Causes extension of thigh.

Iliopsoas

Causes flexion of thigh.

Pectineus

Causes adduction and flexion of thigh.

Thigh

Sartorius

Tensor fasciae latae

Adductor longus

Adductor magnus

Gracilis

Hamstrings

Rectus femoris

Vastus lateralis

Vastus medialis

Sartorius

Causes flexion, abduction of thigh and flexion of leg.

Tensor fasciae latae

Causes flexes and abducts; steadies the trunk on the thigh while standing

Adductor longus

Causes adduction and flexion of thigh.

Gracilis

Causes adduction of thigh and flexion of leg.

Leg muscles

Gastrocnemius

Soleus

Tibialis anterior

Calcaneal (Achilles) tendon

Extensor digitorum longus

Fibularis longus

Hamstrings

Biceps femoris

Semitendinosus

Semimembranosus

acetylcholinesterase

Breaks down ACh into acetyl acid and choline, in the synaptic cleft.