ANATOMY EXAM 3 UIOWA

excitability

ability to respond to stimuli

conductivity

The ability to transmit electrical events along the cell membrane

contractility

ability to generate tension and shorten cell length

elasticity

ability to return to resting length after shortening or lengthening

extensibility

ability to be stretched beyond resting length

(skeletal) muscle characteristics

each muscle is considered an organ

- each muscle contains all 4 tissue types: epitheleal, connective, muscle, nervous

- muscles usually attach to bones

- muscles and muscle cells usually vary in shape and size

skeletal muscle functions

- body movement

- maintenance of posture

- protection and support

- regulating elimination of materials

- heat production

skeletal muscle structure hierarchy

- whole muscle

- muscle fascicle

- muscle fiber

- myofibrils

- myofilaments

CT overview

muscles have multiple layers of connective tissue within and around them

- connective tissue layers are made mostly of collagen and elastic fibers

CT functions

- protection

- sites for blood vessel and nerve distribution

- attachment to the skeleton

endomysium

connective tissue surrounding a muscle fiber

perimysium

connective tissue surrounding a fascicle

epimysium

connective tissue covering the entire muscle

tendon

connects muscle to bone

ligment

Connects bone to bone

aponeurosis

strong sheet of tissue that acts as a tendon to attach muscles to bone

muscle attachments

most muscles extend over a joint and attach to bones on either side of the joint

- muscle contraction usually causes one bone to move while the other bone remains fixed

muscle fiber orientation

muscle fibers are organized into fascicles

four patterns of muscle fascicle arrangements:

1) circular

2) parallel

3) convergent

4) pennate (unipennate, bipennate, multipennate)

circular muscle fiber orientation

fibers arranged concentrically around an opening

- functions as a sphincter to close a passageway or opening

- EX: orbits, mouth, anus

parallel muscle fiber orientation

fascicles are parallel to the long axis of the muscle

- body of muscle increases in diameter with contraction

- high endurance, not very strong

convergent muscle fiber orientation

triangular muscle with common attachment site

- direction of pull of muscle can be changed

- does not pull as hard as equal-sized parallel

pennate muscle fiber orientation

muscle body has one or more tendons

- fascicles at oblique angle to tendon

- pulls harder than a parallel muscle of equal size

- unipennate, bipennate, multipennate

unipennate (pennate) muscle fiber orientation

all muscle fibers on the same side of the tendon

bipennate (pennate) muscle fiber orientation

muscle fibers on both sides of the tendon

multipennate (pennate) muscle fiber orientation

tendon branches within the muscle

naming muscle compounds

skeletal muscle fibers have many of the same components of a typical cell, but some are named differently

EX:

- sarcolemma: cell membrane of a skeletal muscle cell

- sarcoplasm: cytoplasm of a skeletal muscle cell

- sarcoplasmic reticulum: endoplasmic reticulum of a skeletal muscle cell

two main structures are unique to muscle fibers

- transverse tubules (T-tubules)

- sarcoplasmic reticulum

transverse tubules (T-tubules)

deep invaginations of the sarcolemma that extend into the sarcoplasm

- carry impulses from sarcolemma to help stimulate muscle contraction

- unique to muscle fibers

sarcoplasmic reticulum

specialized endoplasmic reticulum of muscle cells

- stores calcium

- internal membrane complex

myofibrils

Cylindrical structures within muscle fibers that run the length of the cell

- make up 80% of fiber volume

- have the ability to shorten, resulting in contraction of the muscle fiber

- contain myofilaments: two types (thick and thin)

thick filaments

myosin

- contains many myosin molecules whose heads protrude on opposite ends of the filament

- heads bind to active sites on actin molecules

- heads pull on thin filaments, sliding them over thick filaments toward center of sarcomere

thin filaments

actin

two regulatory proteins are also part of the thin filament:

- Tropomyosin: regulatory protein, covers the binding sites on the actin and prevents myosin cross bridge binding

- Troponin: aids in exposure of the binding sites

sarcomeres

contractile units within myofibrils, the smallest contractile unit of a muscle

- contain overlapping thick and thin filaments

- one sarcomere spans from one Z disc to the next

Z disc (line)

coin-shaped sheet of proteins on midline of light I band that anchors thin filaments and connects myofibrils to one another

- a sarcomere extends from z disc to z disc

M line

middle of sarcomere

- myosin

- dark line in the center of the H band of a sarcomere

- structural proteins that anchor myosin during contraction

I band

thin filaments only (actin)

- bisected by the Z line

A band

dark area; extends length of the thick filaments (myosin)

- made up of H zone and M line

h zone

thick filaments only (myosin)

- the region of a striated muscle fibre that contains only thick (myosin) filaments. the H zone appears as a lighter band in the middle of the dark A band at the centre of a sarcomere

contraction of skeletal muscle fibers

Contracting muscles pull on tendons to produce movement, contraction begins when a motor neuron impulse stimulates an impulse in a muscle fiber

- muscles develop tension as sarcomeres shorten

- for sarcomeres to shorten, thick filaments attach to thin filaments and pull them toward the centers of the sarcomeres

- sliding filament theory

sliding filament theory

During contraction, thin filaments slide past thick filaments

- Z discs move closer together so sarcomeres shorten

- widths of A bands remain constant, but H zones disappear

- I bands narrow

lengths of filaments never change whether muscle is contracted or relaxed, only their relative positions change

sliding filament theory steps

1. Contraction Cycle Begins

2. Active-Site Exposure

3. Cross-Bridge Formation

4. Myosin Head Pivoting

5. Cross-Bridge Detachment

6. Myosin Reactivation

neuromuscular junction (NMJ)

synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal

components of neuromuscular junction (NMJ)

- Synaptic knob: expanded tip of neuron axon

- Synaptic vesicles: membrane sacs in synaptic knob, filled with acetylcholine (ACh)

- Synaptic cleft: narrow space separating synaptic knob and motor end plate

- Motor end plate: region of sarcolemma with many folds (increased surface area) under the synaptic knob

- ACh receptors: proteins that bind Ach on the motor end plate

- Acetylcholinesterase (AChE): enzyme in synaptic cleft that breaks down Ach (prevents continuous stimulation of muscle)

muscle contraction step 1

A nerve impulse causes acetylcholine (Ach) release into the synaptic cleft

- ACh binds to receptors on the motor end plate of sarcolemma, initiating a muscle fiber impulse

muscle contraction step 2

Spread of the impulse down T-tubules causes calcium to leak into the sarcoplasm

muscle contraction step 3

Calcium ions bind to troponin, and troponin changes shape

- Troponin moves tropomyosin, exposing active sites on actin

- Myosin heads bind to actin's active sites and form cross-bridges

muscle contraction step 4

Myosin pulls actin toward center of sarcomere

- Repeating cycle of attach-pivot-detach-return shortens sarcomere

- Requires ATP (energy)

muscle contraction step 5

impulse stops (power stroke)

- Calcium ions are actively transported into the sarcoplasmic reticulum

- Tropomyosin re-covers active sites

- Filaments passively slide back to their relaxed state

motor unit

a motor neuron and all of the muscle fibers it innervates

- a motor unit contains only some of the muscle fibers in an entire muscle

- when a motor unit is stimulated, all muscle fibers within it contract

- movements that require more force recruit more motor units

Skeletal muscles consist of a mixture of 3 fiber types

- Slow oxidative (SO) fibers, Type I

- Fast oxidative (FO) fibers, Type IIa

- Fast glycolytic (FG) fibers, Type IIb

Slow oxidative (SO) muscle fibers, Type I

endurance, maintaining posture → marathon running

- ATP use: slow

- capacity to make ATP: high, aerobic

- concentration of capillaries: extensive

- color of fibers: dark red

- contractile velocity: slow

- resistance to fatigue: highest

- fiber diameter: smallest

- number of mitochondria: many

- amount of myoglobin: large

- muscles with a large abundance of fiber type: trunk and lower libs

Fast oxidative (FO) fibers, Type IIa

medium duration, moderate movement → walking, biking

- ATP use: fast

- capacity to make ATP: moderate, aerobic

- concentration of capillaries: moderately extensive

- color of fibers: lighter red

- contractile velocity: fast

- resistance to fatigue: high

- fiber diameter: intermediate

- number of mitochondria: many

- amount of myoglobin: medium

- muscles with a large abundance of fiber type: lower limbs

Fast glycolytic (FG) fibers, Type IIb

short duration, intense movement → sprinting, lifting weights

- ATP use: fast

- capacity to make ATP: limited, anaerobic

- concentration of capillaries: sparse

- color of fibers: white (pale)

- contractile velocity: fast

- resistance to fatigue: low

- fiber diameter: largest

- number of mitochondria: few

- amount of myoglobin: small

- muscles with a large abundance of fiber type: upper limbs

distribution of fiber types

- skeletal muscle usually contains all three fiber types

- a single motor unit contains only muscle fibers of the same type

- slow fibers dominate postural muscles, such as those in the back and calf, which contract almost continually

- there are no slow muscle fibers in muscles that require swift but brief contractions, such as those in the eye and hand

muscle hypertrophy

muscle growth from heavy training

- building muscle increases fiber size but not number of fibers

- results from repetitive, exhaustive stimulation of muscle

muscle atrophy

loss of muscle size due to muscle disease, nervous system disease, or lack of use; commonly called muscle wasting

- reduced stimulation results in reduced muscle size, tone, and power

muscle tone

the state of balanced muscle tension that makes normal posture, coordination, and movement possible

- Some muscle fibers activated and some in resting state

two types of muscle contraction

Isometric contraction: muscle tension is less than the resistance, although tension is generated, the muscle does not shorten (no movement occurs) → static

Isotonic contraction: muscle tension equals or is greater than the resistance, the muscle shortens, and movement occurs

- concentric (isotonic) contraction: causes muscles to shorten, generating force as the tension in the muscle is great enough to overcome the resistance

- eccentric (isotonic) contraction: cause muscles to elongate in response to a greater opposing force

agonist

the muscle that contracts to cause a movement

- also called the prime mover

- EX: triceps brachii is the agonist for forearm extension

antagonist

the muscle that yields to the agonist yet aides in regulating movement; muscle acts in opposition to the agonist and is responsible for returning the limb to its original position

- EX: biceps brachii is the antagonist for forearm extension; it is antagonistic to the triceps brachii

synergist

muscle that aids a prime mover in a movement and helps prevent rotation

- muscles that contract to stabilize intermediate joints in a system

fibromyalgia

unexplainable chronic muscle pain

- treatment: antidepressants, exercise, pain relievers

musclular dystrophy

inherited disease characterized by progressive deterioration of muscle tissue, usually resulting in winged scapulae and scoliosis

- results in atrophy of the affected muscle

- muscle fibers are replaced by fibrous connective and fatty tissue

- no cure, but experimenting with stem cell treatment

myasthenia gravis

autoimmune disease in which antibodies are produced that attach to the acetylcholine receptors on the sarcolemma, thus blocking or reducing the stimulatory effect of the neurotransmitter

- symptoms: ptosis, muscle weakness, double vision, difficulty swallowing

- treatments: steroids, immunosuppressants, surgery

Amytropic Lateral Sclerosis (ALS)

neurodegenerative disease affecting various motor neurons

- also known as Lou Gehrigs Disease

- ogliodendrocytes

- loss of function leads to muscle weakness, atrophy, and spastic paralysis

- death usually occurs from respiratory failure within 5 years of diagnosis

cramps

involuntary painful, sustained contractions of a muscle

- cause unknown, but may be due to lactic acid build-up, dehydration, or calcium deficiencies

- can also be caused by a severe blow to the muscle

- treatment: stretching

muscle nomenclature

Muscles are named according to several criteria:

- Muscle action

- Specific body regions

- Muscle attachments

- Orientation of muscle fibers

- Muscle shape and size

- Muscle heads/tendons of origin

axial muscle overview

axial muscles have both their attachments on parts of the axial skeleton

- formerly: "origin and insertion"

- currently: "superior and inferior attachments" or "proximal and distal attachments"

axial muscle functions

- support the head and spinal column

- used in facial expression, chewing, and swallowing

- aid in breathing

- support and protect abdominal and pelvic organs

axial muscle groups

organized into five groups based on their location:

- head and neck

- vertebral column

- respiration

- abdominal wall

- pelvic floor

muscles of the head and neck

separated into several groups based on:

- location

- general functions

- most attach to skull or hyoid bone

muscles of facial expression

attach to superficial fascia or to skull bones

- since fascia is connected to skin, contraction moves skin and changes expression

muscles of mastication

muscles involved in chewing

- move mandible at TMJ

- temporalis: Elevates and retracts mandible

- masseter: Elevates and protracts mandible

muscles that move the head and neck

- anterolateral neck muscles: flex the head and/or neck

- posterior neck muscles: extend head and/or neck

- arise from: vertebrae, thoracic cage, pectoral girdle

- attach to: cranial bones

erector spinae

erector spinae muscles help determine posture

- bilateral contraction extends vertebral column

- unilateral contraction flexes vertebral column towards active muscles

- erector spinae organized into three groups of muscles (iliocostalis, longissimus, spinalis)

erector spinae muscles

- iliocostalis: most lateral group; composed of cervical, thoracic, and lumbar parts

- longissimus: composed of capitis, cervical, and thoracic parts

- spinalis: most medial group; attach to spinous processes of vertebrae; composed of cervical and thoracic parts

muscles of respiratoin

muscles involved with inhalation and exhalation

- external intercostals: elevates ribs during inhalation

- internal intercostals: depresses ribs during forced exhalation

- diaphragm: enlarges thoracic cavity during inhalation

diaphagm

the diaphragm is the most important muscle for breathing

- partition between thorax and abdomen

- dome shaped with a central tendon

- contraction pulls central tendon inferiorly, enlarging thorax

diaphragm contraction also increases intra-abdominal pressure

- important effect for urination, defecation, childbirth, movement of venous blood

muscles of abdominal wall

anterolateral wall of abdomen contains sheets of muscles

- hold organs in place

- together they flex and stabilize vertebral column

- unilateral contraction laterally flexes vertebral column

Four pairs of abdominal muscles

- external oblique: superficial, lateral muscle; fibers directed inferomedially

- internal oblique: deep to external oblique; fibers directed superomedially

- transverse abdominis: deepest of lateral muscles; fibers directed horizontally

- rectus abdominis: long, anterior muscle connecting sternum to pubic bone; divided into four muscle segments

posterior muscles

muscles that function to stabilize or move the scapula

- pectoralis minor

- serratus anterior

- subclavius

- trapezius

- levator scapulae

- rhomboid minor

- rhomboid major

Muscles That Move the Glenohumeral Joint/Arm

nine arm muscles attach to the scapula

- biceps brachii

- triceps brachii

- deltoid

- coracobrachialis

- teres major

rotator cuff muscles:

- subscapularis

- supraspinatus

- infraspinatus

- teres minor

muscles that move the elbow

the anterior compartment contains elbow flexors:

- biceps brachii

- brachialis

- brachioradialis

the posterior compartment contains elbow extensors:

- triceps brachii

- anconeus

muscles moving elbow / forearm

some forearm muscle pronate or supinate the forearm

two muscles on the anterior forearm that pronate the forearm are:

- pronator teres

- pronator quadratus

the muscle on the posterior forearm that supinates the forearm is:

- supinator

muscles that move wrist, hand, and fingers

most muscles in forearm move hand and fingers

- called extrinsic muscles of the wrist and hand

most anterior compartment muscles attach to the medial epicondyle of the humerus

- they flex the wrist, hand, and fingers

most posterior compartment muscles attach to the lateral epicondyle of the humerus

- they extend the wrist, hand, and fingers

forearm anterior compartment muscles

superficial layer

- pronator teres

- Flexor carpi radialis

- Palmaris longus

- Flexor carpi ulnaris

intermediate layer

- Flexor digitorum superficialis

Deep layer

- Flexor pollicis longus

- Flexor digitorum profundus

- Pronator quadratus

forearm posterior compartment muscles

Superficial layer

- Extensor carpi radialis longus

- Extensor carpi radialis brevis

- Extensor digitorum

- Extensor digiti minimi

- Extensor carpi ulnaris

Deep layer

- Abductor pollicis longus

- Extensor pollicis brevis

- Extensor pollicis longus

- Extensor indicis

- Supinator

carpal tunnel

tendons of anterior compartment muscles pass over anterior surface of carpal bones

- along with median nerve, they are held in place by flexor retinaculum

- carpal tunnel: space between carpal bones and flexor retinaculum

pelvic girdle and lower limbs

include the largest and most powerful muscles in the body

organized into specific groups:

- muscles that move the hip joint/thigh

- muscles that move the knee joint/leg

muscles of anterior compartment of leg

muscles of anterior compartment of the thigh flex the hip, most of them proximally attach to os coxae and distally attach to femur

thigh (hip) flexors include:

- Iliacus

- Psoas Major

- Sartorius

- Rectus femoris

muscles of medial compartment of leg

six muscles in medial compartment of thigh

- Adductor longus

- Pectineus

- Adductor brevis

- Gracilis

- Adductor magnus

muscles of lateral compartment of leg

Only one muscle in the lateral compartment of the thigh: tensor fasciae latae

- Abducts and medially rotates the thigh

- Attaches to the iliotibial tract (band), which extends from the iliac crest to the lateral condyle of the tibia

gluteal group

Gluteal group and deep muscles of gluteal region extend, abduct, and rotate hip joint/thigh, most of them attach proximally to os coxae and distally to femur

- Gluteus maximus

- Gluteus medius

- Gluteus minimus

- Piriformis

muscles of posterior compartment of thigh

muscles of the posterior compartment of the thigh extend the hip joint/thigh and flex the leg

hamstring muscles

- biceps femoris

- semimembranosus

- semitendinosus

muscles of anterior compartment of knee/leg

contains muscles that extend the knee joint/leg, ollectively called quadriceps femoris and consist of:

- Rectus femoris

- Vastus lateralis

- Vastus medialis

- Vastus intermedius

crural muscles

The muscles that move the ankle, foot, and toes

muscles of anterior compartment of the leg → foot and toes

muscles in the anterior compartment primarily dorsiflex the foot and extend the toes

- Extensor digitorum longus

- Extensor hallucis longus

- Tibialis anterior

- Fibularis tertius

muscles of lateral compartment of the leg → foot and toes

Muscles in the lateral compartment evert and plantar flex the foot

- Fibularis longus

- Fibularis brevis

muscles of posterior compartment of the leg → foot and toes

Muscles in the posterior compartment primarily plantar flex the foot

- Gastrocnemius

- Soleus

- Plantaris

- Flexor digitorum longus

- Flexor hallucis longus

- Tibialis posterior

nervous system organization

nervous system function: whole-body communication

two models to categorize information flow across the body

- Structural Organization

- Functional Organization