Anatomy Exam 2

Equivalent of Sarcolemma

Plasma Membrane

Equivalent of Sarcoplasm

Cytoplasm

Equivalent of Sarcoplasmic Reticulum

Smooth Endoplasmic Reticulum

Equivalent of Sarcosomes

Mitochondria

Myofibrils

Contractile Fibers

Myoblasts

Skeletal Muscle Precursor Cells

3 Major Types of Muscles

Skeletal, Cardiac, Smooth

Classification of Skeletal Muscle

Voluntary

Key Recognition Cue of Skeletal Muscles

Uniformly striated, Multiple peripheral nuclei

Functions of Skeletal Muscle

Locomotion (Moves joints), Posture, Joint stabilization, Thermogenesis

Types of Skeletal Muscle

Type 1, Type 2a, Type 2b

Type 1 Skeletal Muscle

Slow, Oxidative

Type 2a Skeletal Muscle

Fast oxidative glycolytic

Type 2b Skeletal Muscle

Fast glycolytic

Formation Process of Skeletal Muscle

1. Mesenchymal cells differentiate into myoblasts.

2. Myoblasts fuse together to form myotubes.

3. Myotubes fill up with myofibrils to make muscle fibers.

Organization of Skeletal Muscle (Outwards to Inwards)

Epimysium, Perimysium, Endomysium

Epimysium Tissue Type

Dense Irregular Connective Tissue

Epimysium is continuous with…

Tendon, Aponeuroses, Periosteum

Perimysium Tissue Type

Dense Irregular Connective Tissue

Perimysium surrounds…

Fascicle, Blood vessels, Nerve, Lymphatics

Endomysium Tissue Type

Loose Connective Tissue

Endomysium surrounds…

Individual Muscle Fibers, Capillaries, Nerves

Make-up of muscle fibers

Myofibrils

Myofibrils contain…

thousands of sarcomeres

Sarcomeres are made of…

filaments

Types of filaments

Thin, Thick, Elastic supporting

Thin filaments are…

Actin (5-8 nm)

Two types of thin actin filaments

Troponin, Tropomyosin

Action of Troponin

Regulates actin-myosin interaction

Action of Tropomyosin

Troponin attachment and wraps around actin

Thick filaments are…

Myosin (10 nm)

Elastic supporting filaments are…

Titin (1 nm)

Action of Elastic Supporting Filaments

Connects myosin to Z-line

Sarcomeres are defined from…

Z-line to Z-line

When muscles contract…

thin filaments slide past thick filaments

A Band

thick with thin filament overlap

During contraction, A Bands…

stay the same length

I Band

Thin Filament

During contraction, I Bands…

shorten

Z Line

Anchor within I Band

During contraction, Z lines…

moves closer together

H Band

No actin, only myosin

During contraction, H Bands…

narrows/disappears

M Line

Anchor within H Band

Muscular Hypertrophy

Increase in myofibril cross-sectional size, because muscle fibers are not added/made further.

Sarcoplasmic Reticulum

Network that surrounds myofibrils, and has enlargements called terminal cisterna

T-Tubule

Extensions of sarcolemma between myofibrils

Triad

2 Terminal Cisternae + T-Tubule

Action of Triad

Communicates for calcium release

Signaling for Muscle Contraction is influenced by…

motor nerve

Steps of Muscle Contraction Signaling

1. Neuron releases neurotransmitter (Ach) into synaptic cleft at neuromuscular junction.

2. Neurotransmitter (Ach) goes across sarcolemma, attaches to receptors, and down triads.

3. Calcium is released and binds to troponin.

4. Tropomyosin moves and reveals actin binding sites.

5. Myosin binds to actin via cross bridge.

6. Action potential ends and calcium is removed.

7. Tropomyosin moves back and blocks actin active site.

8. Muscle relaxes.

Function of Sensory Proprioception/Afferent

Protects muscle from excessive movements and regulates muscle force

Actions of Spindles

Stretch detectors

Two types of fibers in Spindles

Intrafusal Fibers, Extrafusal Fibers

Intrafusal Fibers

Specialized for stretch detection

Extrafusal Fibers

Ordinary Force-generating

Function of Golgi Tendon Organ

Detects change in tension

Make-up of Golgi Tendon Organ

Sensory axons and collagen bundles near myotendinous junctionR

Repair/Regeneration of Skeletal Muscle

Existing fibers hypertrophy.

Satellite cells allow for some regeneration/new fibers.

Scarring

Classification of Cardiac Muscle

Involuntary

Key Recognition Cues for Cardiac Muscle

Branching, Intercalated discs, Striated actin/myosin

Cell Shapes of Cardiac Muscle

Cylindrical cells with centrally placed one to two nuclei

Intercalated Discs

Interface between adjacent cells

Two types of Linkage in Intercalated Discs

Transverse Portions, Lateral Portions

Locations of Transverse Portions of Linkage in Intercalated Discs

Adherent Junctions and Desmosomes (TAD)

Locations of Lateral Portions of Linkage in Intercalated Discs

Gap Junctions (LG)

Diads

T-Tubules + Sarcoplasmic Reticulum

Sarcoplasmic Reticulum

Smaller and stores less calcium than skeletal - thus needs extracellular calcium

Cardiac Contraction

Autonomic, via Intrinsic/Pacemaker muscle fibers

Steps of Cardiac Muscle Contraction

1. Initiation - Cell membrane depolarizes intrinsically.

2. Purkinje fibers carry depolarization to destination.

3. Voltage gated sodium channels open.

4. Calcium is released.

5. Actin-myosin cross bridge recycling occurs.

6. Cardiac muscle fibers contract.

Repair/Regeneration of Cardiac Muscle

Existing fibers hypertrophy.

Limited capacity of repairing/scarring (Worst at repairing)

Classification of Smooth Muscle

Involuntary

Key Recognition Cue of Smooth Muscle

No striations or sarcomeres, randomly arranged actin/myosin, tapered cells

Cell Shapes of Smooth Muscle

Small fusiform/spindle shaped cells with central nuclei and gap junctions

Contraction/Peristalsis

No T-Tubule system or troponin, and poorly organized sarcoplasmic reticulum

Steps of Contraction/Peristalsis

1. Calcium binds calmodulin.

2. Calcium-calmodulin activated myosin light chain kinase.

3. MLCK phosphorylates myosin, which leads to actin-myosin interaction.

Attachments of Thin Filaments in Smooth Muscle

Alpha-actinin attachment in sarcoplasmic dense bodies.

Sarcolemma attachment via intermediate filaments.

Placement of Thick Filaments in Smooth Muscle

Random assortion throughout sarcoplasm

Repair/Regeneration of Smooth Muscle

Rapid, because small cells are mitotic.

Cell resources are Pericytes

Muscular development happens mostly in…

embryonic period (weeks 3-8)

Components of Axial Skeleton

Skull, Vertebrae, Ribs, Sternum

Skeletal System is made up of 3 “things”

Paraxial Mesoderm, Lateral Plate Mesoderm, Neural Crest

Paraxial System goes to…

Somites

Somites undergo…

somitogenesis

After somitogenesis, somites split into…

Sclerotome (skeleton) and Dermomyotome are formed

Structures formed from Sclerotome

Annulus Fibrosus, Axial Tendons, Ligaments

Structures formed after Dermamyotome

Myotome (muscle) and Dermatome (dermis)

Lateral Plate Mesoderm splits into…

Somatic/Parietal and Splanchnic/Visceral

Structures formed from Somatic/Parietal

Limb buds and bones, Pelvis, Shoulder bones, Sternum, Connective tissue

Structures formed from Splanchnic/Visceral

Smooth Gut Muscles, Cardiac Muscles

Neural crest cells…

migrate and form Craniofacial Skeleton

Arteries are formed from…

Splanchnic/Visceral and Neural Crest

Parts of the skull that are neural crest derived

Frontal Parts of Skull

Parts of skull that are occipital somite derived

Parietal Parts of Skull

Processes that form the Skull

Intramembranous (within membrane) and Endochondral (within cartilage)

Steps of Vertebrae Development

1. Cells migrate around notochord/spinal chord

2. Resegmentation (caudal to cephalic)

3. Two adjacent scelerotome halves (1 caudal and 1 cephalic) join to form one vertebra.

4. Endochondral Ossification (cartilage to bone)

5. 1 nerve per somite (passes through intervertebral foramen.

6. Arteries that are positioned at center of vertebral body and supplies blood passes between somites (intersegmental)

Intervertebral Discs are…

fibrocartilage

Annulus Fibrosus…

Tough outer part of vertebrae

Nucleus Pulposus…

Center/Inside of vertebrae

Primary Vertebral Curvatures

Thoracic, Sacral