BSC2085L Practical 3

Functional classification of muscles

Agonists, antagonists, synergists, and fixators

Agonists

prime movers, primarily responsible for producing a particular movement

Antagonists

oppose, restrict, or reverse a movement

Synergists

aid the action of agonists

Fixators

specialized synergists that immobilize the origin of the agonist muscle so all tension is exerted at the insertion

Muscle nomenclature

Muscle fiber direction, relative size, location, number of origins, location of muscle origin/insertion, shape, action

Direction of muscle fiber examples

•Rectus= straight line

•Transverse muscles= right angles

Relative size of muscle examples

•Maximus= largest

•Longus= long

Location of muscle examples

•Frontalis= at frontal bone

Number of origins examples

•Biceps= 2 origins

Location of muscle origin/insertion examples

•Sternocleidomastoid= origins at the sternum (sterno) & clavicle (cleido) with insertion at the mastoid process

Shape of muscle examples

•Deltoid= triangular

Action of muscle examples

•Adductor= adduction action

Patterns of fascicle arrangement in muscles

Circular, convergent, parallel, unipannate, multipennate, fusiform, and bipennate

Circular muscle fibers

Fibers arranged concentrically around an opening.

ex. orbicularis oris

Convergent muscle fibers

Muscle fibers form a broad area but come together at a common point

ex. pectoralis major

Parallel muscle fibers

Muscle fascicles are parallel to the longitudinal axis.

ex. sartorius

Unipennate muscle fibers

Muscle body has one or more tendons.

Fascicles at oblique angle to tendon.

Fibers are on the same side of the tendon.

ex. extensor digitorum longus

Multipennate muscle fibers

Muscle body has one or more tendons.

Fascicles at oblique angle to tendon.

Tendon branches within the muscle.

ex. deltoid

Fusiform muscle fibers

muscle fiber with tendon on either end and gets wider

ex: biceps brachii

Bipennate muscle fibers

Muscle body has one or more tendons.

Fascicles at oblique angle to tendon.

Pulls harder than a

Muscle fibers on both sides of the tendon.

ex. rectus femoris

Muscles of the Head/Neck

Epicranius frontalis, epicranius occipitalis, orbicularis oculi, orbicularis oris, masseter, temporalis, platysma, sternocleidomastoid, digastric anterior/posterior belly, mylohyoid, sternohyoid

Facial Expressions

Epicranius frontalis, epicranius occipitalis, orbicularis oculi, and orbicularis oris

Mastication

Masseter and temporalis

Epicranius frontalis (Epicranius frontal belly)

raise eyebrows

-ori: epicranial aponeurosis

-ins: skin of eyebrows & root of nose

Epicranius occipitalis (Epicranius occipital belly)

pulls scalp posteriorly

-ori: occipital and temporal bones

-ins: epicranial aponeurosis

Orbicularis oculi

close eye/pull eyebrow down

Orbicularis oris

close/protrude lips

Masseter

close jaw

-ori: zygomatic arch & maxilla

ins: angle & ramus of mandible

Temporalis

close jaw

Platysma

open jaw/pull lower lip down

-ori: over pectoral muscles

-ins: lower margin of mandible, skin, muscle at mouth corner

Sternocleidomastoid

neck flexion/head rotation towards shoulder

-ori: manubrium of sternum & medial portion of clavicle

-ins: mastoid process of temporal bone, & superior nuchal line of occipital bone

Digastric anterior/posterior belly

open jaw/elevate hyoid bone

-ori: lower margin of mandible & mastoid process

-ins: connective tissue loop to hyoid bone

Mylohyoid

elevate hyoid bone & base of tongue

Sternohyoid

depress larynx & hyoid bone

Muscles of the Anterior Thorax & Shoulder

Deltoid, pectoralis major, pectoralis minor, and serratus anterior

Deltoid

abduct arm; flex/extend/rotate humerus #10

Pectoralis major

adduct/rotate medially arm;

pulls chest upward (inhalation)

-ori: clavicle, sternum, cartilage of ribs 1-6, & aponeurosis of external obliques

-ins: short tendons into intertubercular sulcus of humerus

Pectoralis minor

move scapula anterior/inferior; raise ribs (inhalation)

Serratus anterior

fixes scapula for arm abduction (essential for raising arm); pulls scapula anterior/inferior

Muscles of the Abdominal Wall

Rectus abdominis, external oblique, internal oblique, and transversus abdominis

Rectus abdominis

flex vertebral column; depress ribs; compress abdomen (exhalation)

-ori: pubic crest & symphysis

-ins: xiphoid process & costal cartilage of ribs 5-7

External oblique

flex vertebral column; depress ribs; rotate trunk, compress abdomen (exhalation)

Internal oblique

flex vertebral column; depress ribs; rotate trunk; compress abdomen (exhalation)

Transversus abdominis

compress abdomen (exhalation)

Muscles of the Posterior Trunk

Trapezius and latissimus dorsi

Trapezius

extend head; adduct scapula & lateral clavicle

Latissimus dorsi

extend, adduct, & medial rotate arm

Muscles of the Upper Arm

Triceps brachii, biceps brachii, brachiradialis, and brachialis

Triceps brachii

extend forearm

(#16 [lateral head], 17 [long head], 18 [medial head])

Biceps brachii

flex forearm

-ori: short head - coracoid process; long head - intertubercular sulcus & within capsule of shoulder joint

-ins: radial tuberosity

(#11-13)

Brachioradialis

flex forearm (#19)

Brachialis

flex forearm (#14)

Muscles of the Forearm

Pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, extensor carpi radialis, extensor digitorum, and extensor carpi ulnaris

Pronator teres

pronate & weakly flex arm (#22)

Flexor carpi radialis

flex & abduct hand at wrist (#23)

Palmaris longus

flex hand at wrist

-ori: medial epicondyle of humerus

-ins: palmar aponeurosis, skin & fascia of palm

(#24)

Flexor carpi ulnaris

flex & adduct hand at wrist (#25)

Extensor carpi radialis

extend & abduct hand at wrist

(longus (#20) & brevis (#21))

Extensor digitorum

extends fingers & hand at wrist

-ori: lateral epicondyle of humerus

-ins: by 4 tendons into distal phalanges of fingers 2-5

(#30)

Extensor carpi ulnaris

extend & adduct hand at wrist

(#32)

Muscles of the Anterior & Medial Thigh

Iliopsoas, sartorius, adductor group, pectineus, gracilis, quadriceps femoris, and tensor fasciae latae

Iliopsoas

flex trunk, thigh at hip (#25)

Sartorius

flex, abduct, & laterally rotate thigh

-ori: anterior superior iliac spine

-ins: by aponeurosis into medial aspect of proximal tibia

(#24)

Adductor group

adduct, flex, & medially rotate thigh

(Adductor magnus (#28), Adductor longus (#26), Adductor brevis)

Pectineus

adduct, flex, and medially rotate thigh

Gracilis

adduct, flex, & medially rotate thigh (#27)

Quadriceps femoris group

extend lower leg at knee & flex thigh

•rectus femoris

•vastus lateralis

•vastus intermedius

•vastus medialis

Rectus femoris

quadriceps femoris

-ori: anterior inferior iliac spine & superior margin of acetabulum

-ins: tibial tuberosity and patella

(#20)

Vastus lateralis

quadriceps femoris (#21)

Vastus intermedius

quadriceps femoris (#22)

Vastus medialis

quadriceps femoris (#23)

Tensor fasciae latae

flex, abduct, & medially rotate thigh (#18)

Muscles of the Hip & Posterior Thigh

Gluteus maximus, gluteus medius, biceps femoris, semitendinosus, and semimembranosus

Gluteus maximus

laterally rotate, abduct, & extend thigh

-ori: dorsal ilium, sacrum, & coccyx

-ins: gluteal tuberosity of femur and iliotibial tract

(#11)

Gluteus medius

abduct & medially rotate thigh (#12)

"Hamstrings"

Biceps femoris, semitendinosus, and semimembranosus

Biceps femoris

extend thigh; laterally rotate leg; flex knee

(#31 [long head], 32 [short head)

Semitendinosus

extend thigh, medially rotates leg; flex knee

(#30)

Semimembranosus

extend thigh, medially rotates leg; flex knee

(#29)

Muscles of the Lower Leg

Fibularis longus, tibialis anterior, extensor digitorum longus, triceps surae, and flexor digitorum longus

Fibularis longus (Peroneus longus)

plantar flex & evert foot

-ori: head and upper portion of fibula

-ins: by long tendon under foot to metatarsal 1 & medial cuneiform

(#35)

Tibialis anterior

dorsiflex & invert foot (#33)

Extensor digitorum longus

dorsiflex foot & extend toes (#34)

Triceps surae

plantar flex foot

•gastrocnemius

•soleus

Gastrocnemius

plantar flex & flex lower leg; triceps surae

-ori: by two heads from medial and lateral condyles of femur

-ins: calcaneus via calcaneal tendon

(#37 [lateral (great head)], 38 [medial head])

Soleus

plantar flex; triceps surae (#39)

Flexor digitorum longus

flexes toes, plantar flexes & inverts foot (#42)

Nervous tissue composition

Neurons and neuroglia

Neurons

nerve cells that function to transmit

electrical impulses

Neuroglia

cells that support the neurons

Main divisions of the NS

CNS and PNS

Central Nervous System (CNS)

composed of

the brain and spinal cord

Peripheral Nervous System (PNS)

composed

of the nerves that leave the CNS

Anatomy of a Neuron

Soma, axon hillock, dendrites, axon, axon/synaptic terminal, synaptic cleft, neuroplasm, neurofibrils, and nissl bodies

Soma

the neuron's cell body

A cluster of cell bodies in the PNS is known as a _____ while in the CNS it is a _____

ganglion; nucleus

Axon hillock

tapered structure between soma and axon (important for producing the AP)

Dendrites

processes that conduct electrical impulses towards the soma (usually receives a signal from another cell)

Axon

process that conduct electrical impulses away from the soma