Chapter 8; Bio 210 (Muscles) Flashcards
Muscular System
responsible for movement of the body (Only skeletal muscle)
Skeletal Muscle 6 functions
1- produce movement 2-maintain posture 3-functioning of internal organs 4-guard entrances and exits in body 5-body temperature 6-nutrient reserves
Myofibrils
contractile level of muscle contraction
-made of smaller units called myofilaments
Actin (thin) and Myosin (thick) are
protein filaments (myofilaments) that form Sacromeres
Sacromeres
join end to end to form Myofibrils
Z lines
boundaries of a sacramere [_____]
A band
dark band inside Z lines [_____
I band
light band between z line and a band [{}____{}]
H Zone
where the myofilaments don’t over lap (in the middle)
[{}___ H zone ___{}]
Phases of Contraction
Resting
Excitation (action potential down t tubule excites it)
Excitation/ Contraction Coupling (Ca ions binds with tropin and removes tropamyosin exposing active site)
Contraction (thin slides past thick)
Resting
NMJ
junction between an axon and a motor neuron and a muscle fiber is nueromuscular junction
Motor Neurons
nerve cells with axons that connect nervous system to muscular system
T Tubule (Transverse tubule)
at each junction of A and I bands the sacrolemma indents (tube that holds in multiple myofibrils)
Sacrolemma
plasma membrane of skeletal muscle
Terminal cisterns of the SR
where the T tube runs between then branches off into tubules of SR
SR
sacroplasmic reticulum
Triad
region where cisterns border a T tube
Endomysium
areolar connective tissue surrounds EACH muscle fiber (
Perinysium
wraps several sheather muscle fibers (surrounds fascicles)
Epimysium
bounds together fascicles and sheaths the ENTIRE muscle (dense irregular connective tissue)
Tendon
provides durability and space to the muscles (pass over a joint and provide protection from bone)`
NMJ Process
- Axons branch off to the muscle with Terminal Branches
- Together the neuron and all stimulated muscle fibers make up a ‘Motor Unit’
- The neuron and muscle fibers don’t touch (synaptic cleft)
- Action Potential is released from axon terminals into the cleft
- The ACh diffisues and binds with recpetors on the sacrolemma
- Once joined with ACh, the permeability of sacrolemma changes
- Ion channels open depolarizing the sacrolemma and contraction occurs
Neuron and Muscle Cell
only TWO kinds of cells in body that can propagate action potentials
Motor Unit
ALL stimulated fibers and axons (can be more than one neuromuscular junction)
Synaptic Cleft
space between muscle fibers and the neuromuscular junction
ACh
acetylcholine => a neurotransmitter within many mitochondria and axon terminals
Action Potential
ACh ( K+ or Na+)
Sliding Filament Theory
- Calcium ions diffuse from the sacroplasmic reticulum (inside of the T tubule) into the sacroplasm.
- Calcium ions released from SR bind to troponin molecules
- Troponin molecules bind to G actin molecules are released
- Topomyosin moves and exposes the active sites on G actin
- Active sites are exposed on G actin molecules, heads of myosin bind to them forming cross bridges (EXPOSURE OF ACTIVE SITES)
- Initiates (POWER STROKE) which slides the actin past the myosin filament
- ATP binds to the myosin head causing it to detach from actin (CROSS BRIDGE RELEASE)
- Myosin head splits ATP into ADP and P which Phosphate remains attached to myosin head (BREAKDOWN OF ATP)
- Myosin head returns to resting position and energy is stored in head (RECOVERY STROKE)
Order of Filament Theory
EXPOSURE OF ACTIVE SITES HINGE STROKE (once myosin binds) POWER STROKE CROSS BRIDGE RELEASE BREAKDOWN OF ATP RECOVERY STROKE
Prime Mover (agonist)
the prime mover is the muscle used to accomplish a stimuli
Antagonist
the tricep brachii when extending after flexion of the bicep brachii
Synergist
aid the action of the agonist
Fixator
hold a skeletal place in position when using muscle
Origin of muscle
point of attachment of a muscle when NO movement occurs when the muscle contracts
Insertion Point of muscle
point of attachment of a muscle where movement DOES occur when the muscle contracts (towards the origin point)
Points
medial origin and lateral insertion
non appendenges
Twitch Contraction
single muscle fiber to single stimulus
4 Factors of Muscle Contraction
Motor Unit Recruitment
Frequency of Stimulus
Muscle Tone
Lenght Tension
Isotonic Contraction
muscle tension changes muscle length
- cocentric- muscle lengthens picking up
- eccentric- muscle tension remains the same while muscle lengthens
Isometric Contraction
muscle prevented from changing length even though tension is increasing
Atrophy
muscles lack of activity (cast on)
Hypertrophy
building muscle
