Marieb Ch.6 Muscular system

What are the types of muscle tissue?

Smooth, Cardiac, Smooth

What muscle has cylindrical cells, is striated, has multiple, peripheral, voluntary attached to skeleton

Skeletal muscle

Which muscle has branching cells, striated, one or two central nuclei, involuntary and only belongs in the hearts

Cardiac muscle

What muscle has spindle-shaped cells, isn't striated, single, central nucleus, involuntary, located in the walls of hollow organs

Smooth muscle

Functions of skeletal muscle

Produces voluntary movement, stabilizes joints, maintains posture, generates body heat

Characteristics of Skeletal Muscle

Makes up body "flesh

Most "meat" is skeletal muscle

Muscles are organs: Fibers, motor neurons, blood vessels, connective tissue

Attachments of skeletal muscle

Join muscles to: bones, cartilages, or to CT coverings of other muscles

Tendons-cordlike bundles of collagen fibers

Aponeuroses-Sheet like arrangements of collagen fibers

How are skeletal muscles different?

Long, cylindrical, multinucleate

Sarcolemma: cell membrane

T-tubules: Cell membrane extensions deep into the muscle cell

Sarcoplasm: cytoplasm

Smooth E.R

Mysoin heads free, project out from ends

Myosin tails attached, central

Myosin heads can attach actin, forming crossbridges

Thick Myofilaments

Contractile organelles, lie parallel, run entire length of cell, Composed of myofilaments actin for thin and myosin thick

Myofibrils

Actin and regulatory proteins

Tropomyosin covers sections of actin

Troponin attaches to actin and tropomyosin binding site for CA2

Thin Myofilaments

Contractile units of myofibrils, source of fiber's striations, banding caused by overlapping arrangement of myofilaments

Sarcomeres

Correspond to length of myosin filaments

A (Dark) bands

Actin with no myosin

I (Light) bands

Anchor for actin; separate sarcomeres

Z line

Center of A band; no actin

H zone

Narrow region at center of H zone; anchor for myosin

M line

End of motor neuron

Axon terminal

Space between axon terminal and motor end plate

Synaptic cleft

Sarcolemma at NMJ, Invaginated, High SA, ACH receptors

Motor End Plate

Requirements for simulation of fibers

Fibers must be stimulated, Motor Neurons deliver, Point of communication between a motor neuron and a fiber =NMJ

Fibers and motor neurons do not touch

Neurotransmitter molecules bind to and stimulate muscle fibers

Steps in contraction sliding filaments theory

1. Nerve impulse arrives at axon terminal/ Ca2+ enters terminal

2. Exocytosis of synaptic vesicles

3. Neurotransmitter ACh diffuses across cleft

4. ACH binds to receptors on sarcolemma

5. Prior contraction, sarcolemma must be polarized by NA/K pump

6. Sarcolemma now permeable to Na+ and K

7. Sarcolemma depolarizes as more Na diffuse in than K+ diffuses out

8. Action potential spreads along sarcolemma and down t-tubules

9. SR release Ca2+ into sarcoplasm

10. Ca2+ binds to troponin on actin

11. Tropomyosin on actin moves, exposing binding site

12. Myosin heads attach to actin, form cross-bridges and pivot

13. Actin slides towards center of sarcomere

14. ATP provides energy to release and re-cock myosin heads

15. Relaxation occurs form Cholinesterase breaks down ACh at NMJ

At threshold, a fiber will contract to its maximum extent

All or none laws

A muscle is composed of what?

Motor units

All muscle cells in a motor unit respond maximally or what

They don't respond at all

Strength increases as what increases?

Strength increases as number of motor units increases

What are skeletal muscles capable of?

Graded Respones

Types of Muscle Fibers

Red slow, white fast, intermediate

Fewer myofibrils, weaker, lots of myoglobin, mitochondria and capillaries, requires oxygen to make ATP, Contracts slowly and fatigues slowly and recruited first with endurance

Red slow

-Most myofibrils, strongest and widest in diameter

-Low myoglobin, fewer mitochondria and capillaries

-Makes ATP without oxygen

-High glycogen stores

-Contracts rapidly, as well as fatigues

-Short-term powerful movements

-Recruited last

-May hypertrophy in response to training

White fast

-Middle diameter and number of myofibrils

-Lots of myoglobin, mitochondria, capillaries

-Can make ATP w/o oxygen

-Contracts rapidly, moderately resistant to fatigue

-The second fiber type recruited

-Walking, jogging, biking over short to moderate distances

Intermediate

Effects of exercise

-Skeletal muscles have no mitosis

-Doesn't increase number of skeletal muscle cells

- Hypertrophy

Decrease in the size of muscle cells due to lack of use, everything decreases

Atrophy

Body movements from skeletal muscle

Produced by contraction

Shortening results in movement of attachments

Skeletal muscles have at least two attachments one mobile one immobile

Less movable muscle attachment

Origin

More movable muscle attachment

Insertion

What the muscle does

Action

Decreases angle between bones

Flexion

Movement around an axis

Rotation

Moves appendages away from midline

Abduction

Moves appendage too midline

Adduction

Moves appendage in a circle around joint

Circumduction

Muscle primarily responsible for an action

Prime mover

Muscles that resist prime mover, or move opposite

Antagonist

Muscles that assist prime mover

Synergist

Stabilize origin of prime mover or hold the bone still so all tension is used to move insertion

Fixator