Principles of Physical Training Chapter 1

what are the three types of muscle?

skeletal, cardiac, smooth

cardiac muscle

striated but smaller, branches, and uninucleated

smooth muscle

lines the walls of blood vessels, stomach, ureters, and intestines

skeletal muscle

attaches to bones for movement, striped, and multinucleated

how much of the total body mass is muscular?

35-45%

tendons

attach muscle to bone allowing transfer of energy for movement

what is the primary constituent for tendons?

collagen

ligaments

Connect bone to bone

what is the primary constituent for ligaments?

collagen

what is the secondary constituent for ligamentd?

elastin

muscle organization

myofilaments → sacromere → myofibril → muscle fiber (cell) → fascicle → skeletal muscle (organ)

epimysium

covers the entire skeletal muscle

perimysium

Connective tissue surrounding a fascicle

endomysium

Connective tissue surrounding a muscle fiber

fascicle

bundle of muscle fibers, can be up to 150 fibers

muscle fiber

cylindrical cell containing hundreds of nuclei encased in endomysium

t tubules

tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side

sarcoplasmic reticulum

myofibril

contractile element of skeletal muscle

sarcomere

functional unit of muscle extending from one Z line to another

what are the 2 primary myofilaments?

actin (thin) and myosin ( thick)

A band

determines by the width of a myosin filament, anchored to the z line via titin

- provides the dark striation of skeletal muscle

I band

spans distance between ends of adjacent myosin filaments

- gives skeletal muscles its light striation

H zone

area of an A band that contains myosin not actin

M line

dark line in the middle of the H zone

- helps align adjacent myosin filaments

how is myosin filament formed?

aggregation of myosin molecules

how are actin filaments formed?

globular proteins

tropomyosin

rod like protein that covers the myosin binding sites when at rest

troponin

at the end of each tropomyosin

- accepts Ca2+

- reveal the active binding sites

sliding filament theory

theory that actin filaments slide toward each other during muscle contraction, while the myosin filaments are still

step 1 of sliding filament theory

1. Action Potential (AP) moves down neuron, releases Acetylcholine (ACh) into the synaptic cleft from where it is stored in synaptic vesicles of the axon terminal

step 2 of sliding filament theory

ACh crosses synaptic cleft, binds to ACh receptors on motor endplate of muscle fiber

step 3 of sliding filament theory

Ca2+ migrates to the sarcoplasm and binds to troponin

step 4 of sliding filament theory

binding results in conformation changes in troponin which results in the exposure of myosin head binding sites on actin

step 5 of sliding filament theory

myosin head attach to the binding sites on the actine filament forming a cross bridge. ADP and PI dissociate from the myosin head resulting in a power stroke action

step 6 of sliding filament theory

ATP binds to the myosin head and is quickly hydrolyzed dissociating myosin and actin filaments ( restroke)

step 7 of sliding filament theory

the process occurs in a cycle until CA2+ is actively pumped back into the SR

concentric muscle action

When a muscle is exerting force greater than the resistive force, resulting in shortening of the muscle.

eccentric muscle action

when a muscular force is less then the external force, resulting in lengthening of the muscle

isometric muscle action

When a muscle is exerting force equal to the force being placed on it leading to no visible change in the muscle length

Type 1 muscle fibers

slow-twitch, smaller and slower to produce maximal tension, more resistant to fatigue.

how do type 1 muscle fibers generate ATP?

aerobic means

what are the features of type 1 muscle fibers?

- high oxidative capacity

- lots of mitochondria

- very dense vasculature

- contains myoglobin

type 2 muscle fibers

fast-twitch, larger in size, quick to produce maximal tension and fatigue more quickly

what are some features of type 2 muscle fibers?

- fast oxidative glycolytoc and fast glycolytic

- high ATPase activity = fast contractions

how do type 2 muscle fibers generate ATP?

through anaerobic means

type IIx

purely anaerobic and highly fatigable

type IIa

hybrid, have an increased aerobic capacity, slight resistance to fatigue

what neurotransmitter is associated with initiating muscle contraction?

acetocholin

where is the cell body and dendrites of motor neurons located?

anterior grey horn

motor units

a single motor neuron and all muscle fibers innervated by it

what are the 2 neural mechanisms responsible for force gradation?

motor unit recruitment and rate coding

motor recruitment

increasing the force of contraction of a muscle by progressively increasing the number of motor units activated

rate coding

rate at which the motor units are fired

what neural mechanism do smaller muscles use?

rate coding up to 50%

what neural mechanism do larger muscles use?

motor unit recruitment up to 80%

muscle spindles

receptors sensitive to change in length of the muscle and the rate of that change, sense stretch

golgi tendon organs

Receptors sensitive to change in tension of the muscle and the rate of that change

why are muscle spindles and golgi tendons important?

they monitor posture and balance for safety

osseous tissue

dynamic, living bone tissue

compact (cortical) bone

compact, hard, dense bone 80-90% calcified

- contain haversian system

cancellous (trabecular) bone

spongy bone

- synthesis red blood cells

- no haversian system

wolff's law

A bone grows or remodels in response to forces or demands placed upon it

osteoclasts

bone cutters, resorb bone

when are osteoclasts activated?

when calcium levels are low

osteoblasts

bone forming cells

osteocytes

mature bone cells

what are the three most common fracture sites?

hip, spine, wrist

when is peak bone mass?

around 20