Muscule Physiology Flashcards
Tendons
bands of tough, fibrous CT that connect muscle to bone
Fasciculus:
small bundle of muscle fibers
Muscle fiber
long, multinucleated cell that generates force when stimulated
Myofibril
portion of muscle composed of thin & thick myofilaments (actin & myosin)
Actin & myosin
contractile proteins in muscle
Role of connective tissue:
Stabilizes & supports components of skeletal muscle
Surrounds muscle at each organizational level
What are the 3 layers of connective tissue in muscle?
Epimysium:
Perimysium
Endomysium
Epimysium:
covers whole muscle
Perimysium
covers bundles of muscle fibers (fasciculi)
Endomysium
covers individual muscle fibers
Characteristics of Connective Tissue
Sheaths coalesce to form tendons at each end of muscle
Force generated by muscle is transferred to tendon & bone
Epimysium helps prevent spread of signal for muscle activation
Elastic component of CT contributes to
Force & power production (like recoil of rubber band)
Stretch-shortening cycle
Eccentric action
elongation
Concentric action
shortening
Sarcomere
Basic skeletal muscle unit
Capable of force production & shortening
Arrangement of protein filaments gives striated appearance
Components of sarcomere
Z lines H zone I bands A band M line
Z line
at each end of sarcomere
H zone
in middle of sarcomere, contains myosin
I bands
at edges of sarcomere, contain actin
A band
overlapping actin & myosin
M line
middle of H zone, holds myosin in place
What happens as the sarcomere shortens:
Actin filaments slide over myosin
H zone disappears as actin filaments slide into it
I bands shorten as actin & myosin slide over each other
Z lines approach ends of myosin filaments
What happens as sarcomere relaxes:
It returns to original length
H zone & I bands return to original size & appearance
Less overlap between actin & myosin
What makes up myosin filament?
Has globular head, hinged pivot point, & fibrous tail
Head of myosin filament?
made up of enzyme myosin ATPase
Tails of myosin filament?
intertwine to form myosin filament
What is the crossbridge of myosin made up of?
Consists of 2 myosin molecules, with 2 heads
Action of crossbridge:
Interacts with actin
Develops force to pull actin over myosin
Features different isoforms of ATPase
Type I (slow-twitch)
Slow to reach peak force production Low peak force High capacity for oxidative metabolism Fatigue-resistant Endurance performance
Type II (fast-twitch)
Rapidly develop force High peak force Low capacity for oxidative metabolism Fatigue easily Sprint, short-term performance
What is the increase in delivery of oxygen to muscle caused by?
Increase in # of capillaries per muscle fiber
Increase in capillary density
Increase in concentration of myoglobin, which increases rate of oxygen transport from capillaries to mitochondria
What is the enhanced ability for aerobic metabolism caused by?
Increase in size & number of mitochondria in muscle
Increase in ability to produce ATP
What are the effects of resistance training?
hypertrophy
hyperplasia
Hypertrophy
Increase in size of muscle fibers
Results from addition of protein & new myofibrils to existing fibers, making them larger
Requires addition of myonuclei to support increase in muscle fiber size
Hyperplasia
Increase in number of muscle fibers
Occurrence is controversial
