Direct attachment?
Indirect attachment?
Direct - Epimysium&periosteum/perichondrium fused
Indirect - ct wrappings extend beyond muscle as a rope like tendon
What are the 3 muscle layers?
Epimysium - dense reg
Perimysium - fibrous ct
Endomysium - areolar
7 things a skeletal muscle contains?
Myofibrils, nuclei, sarcolemma, sarcoplasma, t tubules, sarcoplasmic reticulum, triad
What does sarcoplasm contain?
Mitochondria, glycosomes, myoglobin, myofibrils
Function of tropinin?
Holds tropomysin in place
Function if tropomysin?
Blocks binding site
Control switch for contraction
I band?
Light, z disc in middle, actin
Z disc?
Sheet of alpha actinin the anchors filaments
A bands?
Dark filament between I bands, contains actin and myosin
H zone?
Lighter zone, only myosin, in middle of a
M line?
Dark, middle of h, contains myomesin which anchors myosin filaments
What are elastic filaments made of, where are they located and what is their function?
Protein Titin
Z–>M through myosin
Recoil to original length
When does shortening occur?
When tension generated by cross bridges on actin exceeds forces opposing the shortening.
What is activation?
Neural stimulation at junction
Excitation-contraction coupling?
Generation/ propagation of ap along sarcolemma to the contraction
Where are neuromuscular junctions located ?
Half way along muscle
How does initiation of contraction reach t -tubules?
Nerve is stimulated along axon -> ca channels open and enter axon-> ca triggers vesicles to release ach into cleft->goes to receptors on sarcolemma->action potential initiated in sarcolemma->chem regulated na open and it moves in, slight depolarizers ->triggers voltage na channels to open -> membrane depolarizers to created AP-> after ap passes na shuts, k opens and moves out-> repolarization-> na/k pumps restore balance-> ap travels along sarcolemma and destruction of ach
Sliding filament?
Ap at sarcomere ➡️t tubules➡️voltage sensitive proteins stimulate release of ca from SR➡️ca binds to tropinin➡️changes shape and moves tropomysin away from actin binding sites➡️ ATP binds to head and hydrolisizes to adp and pi➡️ head becomes cocked and form cross bridges➡️head changes shape producing power stroke and actin is pulled inwards➡️adp and pi release and new apt binds and continues
Process with go on till apt or ca ions not available
Refractory period?
When membrane needs to be repolarized before it can be stimulated agAin
3 roles of calcium in contraction?
To be released in axon terminal to release ach into cleft
To bind to tropinin to move tropomysin off actin binding sites
Extra calcium in sarcolemma binds to calmodulin activating kinases which converts glycogen to glucose for ATP production
What is tension?
Force exerted on a load
What is an isometric contraction?
No shortening, muscle tension ⬆️ but doesn’t exceed load
What is isotonic contraction and what are the two types?
Shortening because tension>load
Concentric - shortens
Eccentric - lengthens(balance)
What is a motor unit?
Motor neuron and fibers it supplies Small-fine moving Large- weight bearing movements Weak contraction Asynchronous
What is a muscle twitch and what are it’s three phases?
Response to single stimulus
Latent-e-c coupling
Contraction- cross bridge form, tension⬆️
Relaxation-ca renters SR, tension=0
What are responses graded by?
2
Frequency
strength -⬆️stimulus =⬆️recruitment= ⬆️strength
Threshold stimulus ?
Max stimulus?
Min strength needed to cause first visible contraction
Max contraction occurs
What is muscle tone, and what does it do for us?
Slightly contracted due to spinal reflexes activating motor units in response to input from stretch receptors
Firm healthy excitable
Direct phosphorylation of ADP? Formula?
CreatineP04 ➡️ creatine➕po4
Po4 +adp ➡️ATP
What is anaerobic pathways? What happens and who uses them?
Blood vessels compressed->o2 delivery impaired
Pyruvic acid➡️lactic-> blood
Liver kidney heart
Liver converts it back into Pyruvic acid
Aerobic respiration? What is it used during? and what is used first?
Rest, light and moderate exercise
Glycogen>blood glucose> Pyruvic acid from gylcolysis> fatty acids
What is muscle fatigue and why does it happen?
Inability to contract or respond to stimulus
Ionic Imbalance ca2 depletion lack of ATP
O2 deficit – o2 reserves, myoglobin, glycogen stores, atp/ cp reserves need to be replenished and lactic acid needs to return to pyruvic, glucose and glycogen
What is the force of a muscle contraction affected by?
Recruitment
Size - increases strength
Frequency - time for more effective transfer of tension to non contractile components
Length tension relationship
Velocity and duration of contraction are affected by?
Muscle fiber - speed of contraction, metabolic pathways for ATP
Load -⬆️load➡️⬆️latent➡️⬇️contraction➡️ ⬇️duration
Recruitment - more recruited, faster, longer
3 types of metabolic pathway fibers?
Slow oxidative - slow contracting& fatiguing **endurance
Fast oxidative - middle **sprinting and walking
Fast glycolytic - fast contract/fatigue
** short term high energy activities
What does aerobic exercise lead to?
⬆️muscle capillaries
⬆️mitochondria
⬆️myoglobin synthesis
⬆️endurance, strength, resistance to fatigue
**may convert glycolytic fibers to fast oxidative
Anaerobic exercise results in?
Muscle hypertrophy
⬆️mitochondria, myofilaments, glycogen stores and CT
Structure of smooth muscle?
One nucleus, spindle shaped cells
Endomysium only
Actin and myosin
Where is calcium stored in smooth muscle?
Caveolae which are indentations in membrane
Innervation of smooth muscle?
Autonomic nerve fibers @diffuse junctions
Varicosities of nerve fibers store and release nts
Myofilaments in a smooth muscle?
Fewer myosin compared to actin than in skeletal
Myosin has heads along whole length
Calmodulin binds with ca.. No trop
Spirally arranged, contract like corkscrew
Body proteins anchor intermediate filaments to sarcolemma
Characteristics of a smooth muscle contraction?
Slow, synchronous Cells have gap junctions Rate&intensity modified by stimuli Can divide Pacemaker cells -stimulate whole con Energy efficient, slow, longer lasting
Stress-relaxation response of smooth muscle?
Briefly responds to stretch then adapts
Can still contract on demand
Storage
Neural regulation of a smooth muscle contraction?
⬆️ or ⬇️ in ca in sarcoplasm
Response depends on neurotransmitter released and the type of receptor
What does ach do in neural regulation of smooth muscle contraction?
Contracts bronchioles
What does norepinephrine do in neural regulation of smooth muscles?
Contracts bv walls
Inhibts bronchioles contraction
Single unit smooth muscle?
Rhythmical contractions Gap junctions Spontaneous AP Opposing sheets Stress-relaxation response Most common: hollow orgs
Multi unit smooth muscle?
Large airways, arteries, a rector pilli, iris
Motor units
Graded contractions occur in response to neural stim
Not synchronous