Ch. 5: The Muscular System

Muscular System

• The muscular system is composed of muscles and tendons

• Muscular system's functions:

  • Movement

  • Stability

  • Control of body openings and passages (mouth, eyes, ears, anus)

  • Communication

  • Heat production 

Flexion

Action that bends a part of the body anteriorly, such as flexing the elbow

• The exception is the knee

• Flexion of the knee moves the lower leg posteriorly

Extension

Action that bends a part of the body posteriorly, such as straightening the arm at the elbow

• As with flexion, the exception is the knee

• Extending the knee straightens the lower leg

Abduction

Movement of a part of the body away from the midline

Adduction

Movement of a part of the body toward the midline

Protraction

Movement that brings part of the body forward

Retraction

Movement that brings part of the body backward

Dorsiflexion

Position of standing on the heels with the toes pointing up off the floor

• “Door” holding the door open with your foot

Plantar Flexion

Position of standing on tiptoes with the heels off the floor

Inversion

Position in which the soles of the feet are together, facing each other

Eversion

Position in which the soles of the feet point away from each other

Rotation

The act of spinning on an axis

• Lateral rotation: away from the midline

• Medial rotation: back to midline

Circumduction

The act of making a circle with part of the body

Supination

Rotation that turns the palms up

• “Holding a bowl of soup”

Pronation

Rotation that turns the palms down

Opposition

The act of bringing the thumb to the palm

Reposition

The act of taking the thumb away from the palm

Elevation

The act of closing the jaw or raising the shoulders

Depression

The act of opening the jaw or lowering the shoulders

Skeletal Muscle

The connective tissues of the muscle come together at the end of the muscle cell, or fiber, to form a tendon

Epimysium

A muscle that has fibrous covering

Fascicles

A muscle composed of a bundle

Perimysium

Surrounds each fascicle

Endomysium

Surrounds fascicles composed of muscle fibers

Sarcolemma

Plasma membrane

Sarcoplasmic reticulum

Smooth endoplasmic reticulum in a muscle cell

• Stores calcium

Myofibril

Bundle of thick and thin myofilaments arranged in sarcomeres

• Thick and thin myofilaments are composed of protein molecules

Thick myofilament

• Myosin subunits look like a doubleheader golf club

• Branches off into myosin heads

Thin myofilament

• Actin subunits make up a double chain of beads twisted together

• Tropomyosin is a thread that holds the actin chained together

• Troponin is a calcium regulatory molecule

  • Binds to calcium after a contraction

Sarcomeres

• Each myofibril consists of repeating contractile units called sarcomeres

  • Sarcomere extends from Z line to Z line

  • Actin/thin filaments are attached to Z lines and extend towards center of sarcomere but do not meet 

  • Myosin/thick filaments reside in the A band and do not contact the Z lines

Neuromuscular Junction

• Stimulation of a muscle cell by a nerve happens at a neuromuscular junction

  •  Generically referred to as a synapse

• Nerve cell releases the transmitter acetylcholine to the muscle cell

• Acetylcholine binds to receptors on the muscle cell to stimulate it to contract

Sliding Filament Model

• Muscle contraction involves thick myofilaments grabbing thin myofilaments and pulling them toward the center of the sarcomere

• All the sarcomeres are shortened which shortens (contracts) the muscle cell

Twitch

A contraction of a muscle cell in response to a single nerve stimulus

• A twitch has a latent phase, contraction phase, relaxation phase, and refractory phase

  • Latent- no contraction

  • Refractory- back to normal

Tetany

A sustained contraction due to repetitive nerve signals

• The frequency (amount per second) of the nerve impulses that determines whether the contraction will be a twitch or tetany

Skeletal Muscle Tissue

Long, striated cells with multiple nuclei

• under voluntary control, aerobic or anaerobic respiration for energy production, and are associated with bones, skin, and body openings

Cardiac Muscle Tissue

Branched, striated cells with a single nucleus and Junctions between cells called intercalated disks

• autorhythmic, rely on aerobic respiration for energy production, located in the heart

• Involuntary

Smooth Muscle Tissue

Spindle-shaped cells with a single nucleus, non-striated

• involuntary control, rely on aerobic respiration for energy production, located in the walls of blood vessels and hollow organs

Aerobic Respiration

• Produces lots of ATP (36) per glucose

• Requires oxygen

• Muscle cells can do either aerobic or anaerobic respiration to process energy

Anaerobic Respiration

• Produces only 2 ATP

• Does not need oxygen

• Produces lactic acid

Orbicularis oris

• Surrounds the mouth

• Opening and closing the mouth

Orbicularis oculi

• Surrounds the eyes 

• Opening and closing the eyes

Frontalis

• Forehead/ frontal bone

Occipitalis

• Back of head/ occipital bone 

Temporalis

• Muscle covering temporal bone on each side

Buccinator

• Found underneath masseter

Masseter

• Major jaw muscle/ open and close jaw

Platysma

• Most superficial muscle in the neck/ sides not back

• “When your scared or frowning”

• Pulling the mouth downwards

Sternocleidomastoid

• Has 3 attachment points

  • Sterno- sternum 

  • Cleido- clavicle

  • Mastoid- mastoid process

Zygomaticus major

• Attached to zygomatic bone/arch

• Cheek bone area

Hyoid bone

Only floating bone

• Found in the throat area/ above thyroid cartilage- voice box

Suprahyoid muscles

Toward mouth/chin

• Geniohyoid 

  • Chin area

• Digastric

  • Anterior and posterior belly 

  • Lateral to geniohyoid

  • Anterior belly then wraps around to the back: posterior belly 

• Mylohyoid 

  • Mouth/mandible

    • Floor of mouth

• Stylohoid

  • Styloid process of temporal

• Mnemonic: My Grandma Sews Dresses or Go Down My Street

Infrahyoid muscle

Toward clavicle, sternum, thyroid (inferior) 

• Thyrohyoid

• Omohyoid 

  • Shoulder/ travels to shoulder

    • One on each side

• Sternohyoid 

  • Attaches to sternum 

• Sternothyroid

  • Attaches to sternum on one end and thyroid on another end 

• Mnemonic: TOSS

Pectoralis major

Superficial

Pectoralis minor

Deep

Serratus anterior

• Looks like serrated knife

• Branching of different muscles

• Covers/surrounds ribs

• Wraps around part of the back

Diaphragm

External intercostals

Superficial

Internal intercostals

Deeper

External abdominal obliques

Superficial of all abdominal muscles

Internal abdominal obliques

Deeper than external 

Rectus abdominis

Straight up and down or vertical 

Transverse abdominal

Transverse- horizontally 

• Linea alba, rectus sheath, rectus abdominis all give that 6 pack figure

Trapezius

Main muscle for extending the head 

Latissimus dorsi

• Middle/lower back region aka lats 

• Also attaches to the humerus

Erector spinae

Vertical straight up and down of the spinal column 

Gluteus maximus

Gluteus medius

Superior than the maximus 

Deltoid

Main shoulder muscle 

Biceps brachii 

• Anterior portion of the arm 

• Biceps have 2 heads

Triceps brachii

• Posterior portion of the arm

• Triceps have 3 heads

Brachialis

• In between triceps and biceps in lateral view

• Prime mover of flexing the elbow

Brachioradialis

• Lower part of the arm down to the radius to the thumb

• Major forearm muscle of the proximal

Extensor carpi radialis

Posterior

Extensor carpi ulnaris

Posterior

Palmaris longus

• touch pinky to thumb and a muscle shows in the carpal region

• Not everyone has this muscle

Flexor carpi radialis

Anterior

Flexor carpi ulnaris

Anterior

Extensor digitorum (extends fingers)

Posterior

Flexor digitorum

Anterior

Tensor fasciae latae

Gracilis (adductor muscle)

Most medial

Adductor longus (adductor muscle)

Pectineus (adductor muscle)

Most lateral

Iliacus (pelvic muscle)

Attaches to ilium

Iliopsoas (pelvic muscle)

Beneath iliascus

Psoas major (pelvic muscle)

• Attaches to lumbar region on one end and down to femur on another end 

• Helps lift leg when running or stepping

Sartorius

“S curved shaped”

Quadriceps Femoris

• rectus femoris (on top of femur) 

• vastus lateralis (lateral side)

• vastus medialis (medial side) 

• vastus intermedius

  • Deeper to rectus femoris

Hamstrings

• biceps femoris (most lateral)  

• semitendinosus (

• semimembranosus (most medial)

Gastrocnemius

Superficial calf muscle 

Soleus

• Makes up two main calf muscles 

• Deeper than gastrocnemius

Peroneus/fibularis

Closer to fibula

Tibialis anterior

• Closer to the tibia

• Outside of the shinbone

Calcaneal tendon (achilles tendon)

Carpal Tunnel Syndrome

• Inflammation of the tendons traveling under the carpal ligament

• Caused by prolonged repetitive motions of the fingers and hands, such as typing on a computer keyboard or regularly working with hand tools, can cause

• Gradual numbness, tingling, burning, and weakness in your hand and fingers