Muscular System 6M

Contractility

Excitability

Extensibility

Elasticity

Tendons

Muscle

Muscle fiber

Fascicles

Myofibril

Bundles of myofilaments

Myofilaments

Has actin and myosin

Epimysium

Covers each skeletal muscle

Perimysium

Separates muscle fascicles from each other

Endomysium

Sarcolemma

T-tubules or transverse tubules

Carry electrical impulses to the cell

Sarcoplasmic reticulum

Stores and release calcium when stimulated

Sarcoplasm

Actin myofilaments

Myosin myofilaments

Sarcomere

basic structural and functional unit of muscle

• i band

• A band

• H zone

• Runs from Z disk to Z disk

I band

Light. Made of actin only

A band

Dark. Actin + Myosin

H zone

Only myosin. Center of each A band

Z line

M line

Muscle contracts

Closure of H zone

Actin

thin. 3 proteins:

1. Actin

2. Tropomyosin

3. Troponin

Myosin

• has myosin heads

• Has 3 properties

Resting Membrane Potential

Charges inside is more negative compared to outside

Action potential

Needed to initiate muscle contraction

Reversal of resting membrane potential

Inside positively charged

Phases:

Depolarization

Repolarization

Depolarization

Sodium enters

Inside befomes positive

Repolarization

Return of membrane to resting value

Sodium channels starting to close

Motor neurons

Generate action potentials

Motor unit

Single motor neuron and all the skeletal muscle fibers it innervates

Presynaptic terminal

Synaptic cleft

Postsynaptic membrane

Acetylcholine

Pre synaptic terminal

Postsynaptic membrane

Voktage gated Ca channels

Ligand gated Sodium channels

Acetylcholinesterase

Acetylcholine

brokendown to choline and acetic acud

Muscle relaxation

Acetylcholine No longer released

Calcium transpoted back to sarcoplasmic reticulum with thr help of ATP

Relaxation takes longer than contraction

2 types muscle contraction

Isotonic

Isometric

Isotonic contraction

Change in muscle length/tension

Isometric contraction

increased tension no change in length

Subtypes of isotonic

• concentric

• Eccentric

Concentric

Shorten muscles

Eccentric

Lengthening of muscle

Slow twich (Type I)

Endurance activities, maintain posture

Abundant myoglobin

Fast twitch (Type II)

Rapid, intense movement of short duration

Aerobic respiration

ATP, CO2, H2O

Anaerobic respiration

• does not require O2

• Breaks down glucose to produce ATP and lactate

Fatigue

Temporary state of reduced work capacity

Acidosis and ATP Depletion

Oxidative

Local inflammatory reactions

Muscle fatigue: physiological contracture

Muscle fatigue: psychological fatigue

Involves CNS

Effects of aging: Sarcopenia (Muscle Atrophy)

Reduction in muscle mass and decrease in its function

Muscle names according to:

1. Location

2. Size

3. Shape

4. Orientation of fascicles

5. Origin and insertion

6. Number of heads

7. Function

Facial muscles

Occipitofrontalis - raise eyebrows

Orbicularis oculi - closes eyelids; cause wrinkles at lateral corner of eye

Kissing muscles

Orbicularis oris - around mouth

Buccinator - blowing or whistling “trumpeter’s muscle

Smiling muscles

Zygomaticus major and minor - typical smile that you have hehehe

Levator labii superioris - elevate one side of upper lip (sneering)

Depressor anguli oris

Depresses the corner of mouth; frowning

Muscles of mastication

Elevating mandible

Temporalis, masseters, medial pterygoid

Depresses the mandible

Lateral pterygoid

Tongue movement

Intrinsic

Extrinsic

tongue muscles

Genioglossus - protrudes tongue

Hyoglossus

Styloglossus

Palatoglossus

Muscles for swallowing

Pharyngeal elevators

PharyngealConstrictors

Neck muscles

• contraction of one - rotate head to opposite side

• Contraction of two - elevate head

Trapezius

Widest muscle in the body

Scalene

Accessory muscle for respiration

Trunk muscles

Muscles moving veryebral column

Superficial only study this

Deep

Superficial muscles

Erector spinae

• iliocostalis

• Longissimus most of muscle mass in the back

• Spinalis

Thoracic muscles

External intecostals - elevate ribs

Internal intercostals - depress ribs

Diaphragm

Responsibke for normal, quiet breathing

Controlled by phrenic nerve

Abdominal wall muscles

Opposite of erector spinae

Example:

rectus abdominis

External abdominal oblique

Internal abdominal oblique

Transversus abdominis

Linea alba (white section)

Tendinous intersection

Pelvic floor muscles

Coccygeus - elevates and supports pelvic organs

Levator ani - elevate anus

Muscles for scapular movement

Serratus anterior

Muscles that move shoulder

Pectoralis major

Latissimus dorsi

Deltoid

Rotator cuff muscles

Stabilize shoukder joints

• supraspinatus

• Infraspinatus

• Teres minor

• Subscapularis

Anterior compartment of arm

Biceps brachii

Brachialis

Posterior compartment of arm

Extensor of elbow

Triceps brachii

Posyerior Muscles of forearm

Supinators and extensors

Flexor of elbow

Anterior compartment of forearm

Pronators

Flexors