Muscular System

Sagittal Plane - Flexion

Decreases the angles of two body parts (e.g. bending elbows)

Sagittal Plane - Extension

Increases the angles of two body parts (e.g. straightening elbows)

Sagittal plane - Dorsiflexion

Ankle flexion - bring toes toward shin (toward up of the body)

Sagittal plane - Plantar flexion

Ankle (toes) pointing toward the ground.

Frontal Plane - Abduction

Move away from the midline

Frontal Plane - Adduction

Move toward the midline

Frontal Plane - Elevation

move upward, superior (e.g. closing mouth - mandible goes up)

Frontal Plane - Depression

move downward, inferior (e.g. shoulder shrug)

Frontal plane - Inversion

lifting medial border of the foot (put weight inside the foot)

Front plane - Eversion

lifting lateral border of the foot (put weight outside of foot)

Transverse plane - Pronation

palm face down to floor; rotate inward/ medially 向內

Transverse plane - Supination

palm and wrist face up; rotate outward/ laterally 向外

Transverse plane - Horizontal Adduction

Angle between two joints decreases

Transverse plane - Rotation

Pivoting on the axis (rotating head, thighs)

Skeletal Muscle structures

Multi-nucleated; Striated; somatic voluntary control; tubular and cylinder shaped

Smooth muscle

Autonomic control; can use myogenic mechanism to contract; non-striated; uninucleate; spindle-shaped

Cardiac msucle

Autonomic control; myogenic; striated and branched; uninucleate BUT may have two nuclei; connected by intercalated discs with gap junctions

Myogenic mechanism

muscle can contract on its own without nerve signals

Label the t-tubule system from the top

1. Sarcolemma

2. Sarcoplasmic Reticulum

3. Terminal cisternae (two chambers that sandwich T-tubules)

4. Transverse (T) Tubules

5. Triad (the sandwich structure of T-tubules and terminal cisternae)

Where is the AP impulse going in skeletal muscle fibers for contraction?

AP propagated to sarcolemma, AP impulse send to the t-tubles and depolarize to SR, Ca2+ channels on SR open to release Ca2+ ions. Muscle contraction. ATP-Calcium pumps within the SR membrane pump Ca2+ back into SR and muscle relax.

Sarcomere

Functional contractile unit of muscle between two Z-lines

What forms myofibril?

Many sarcomere lie end to end.

How does sarcomere contract?

Myosin head attach to actin binding site and form cross bridges. Pulling actin toward the mid line of sarcomere, and myosin is close to Z-line (power stroke).

Thin filament structure

Actin molecules form double helical strands.

Troponin complex (the one inside - connect to G-actin; middle - hold tropomyosin in place; top one - link to calcium)

Tropomyosin - block actin binding site for link up myosin when Ca2+ is not presented.

Thick filament structure

Two myosin molecules (looooonggg) form double strands.

Myosin head have Actin-binding site and ATPase site

What is the role of ATP in slide filament contraction?

ATP binds to the myosin head ATPase site; ATP is hydrolyzed into ADP + Pi. This breakdown causes myosin to release from actin and reset myosin to bind to another actin site.

Three types of skeletal muscle fibers

1. Slow Oxidative (SO Type I); Red

2. Fast Oxidative (FOG Type IIa); Red

3. Fast Glycolytic (FG Type IIb); White

The characteristics of Slow Oxidative Type I Fibers

Small diameter, high myoglobin = Red, high capillary density, many mitochondria, rely primarily on aerobic oxidative phosphorylation (low glycolytic enzyme content)

For prolonged, low-intensity aerobic activities, maintain posture

The characteristics of Fast Glycolytic Type II Fibers

Fast twitch, Larger diameter, low myoglobin and low capillary density = White, few mitochondria = forced to rely on glycolysis, high glycolytic enzyme content

For short bursts, e.g. sprinting/ heavy lifting

Fast Oxidative Type IIa Fibers’ characteristics are all moderate/ between type I and IIb

For moderate intensity activities, running

Pacemaker cell pathways

1. Sinoatrial (SA) node

2. Atrioventricular (AV) node