L10- Mucles Flashcards
What are the 3 types of muscle tissue?
Skeletal, cardiac and smooth muscle
Skeletal muscle location & function
Location = attaches bones across joints
Function = moves joints ➡️moves the body
Smooth muscle function and location
Location = around tubes and sacs
Function = open/ close tubes
Regulate diameter of tubes
Propel material through tubes
Cardiac muscle function and location
Function: create driving pressure to move blood thoughts vessels
Location= heart
What muscle tissues are striated?
Skeletal and cardiac muscle
What muscle types are voluntary and which are involuntary?
Skeletal muscle = voluntary
Cardiac and smooth = involuntary
What is the primary function of skeletal muscle?
Energy transducer
What happens in a skeletal muscle when it is contracted vs relaxed?
Contracted = active
- Motor neuron Ap releases Ach ➡️ binding to Nicotinic receptor ➡️ depolarization = contraction
Relaxation = passive
- no action potentials to motor neuron
Structural hierarchy of skeletal muscle
Muscle ➡️ fascicle ➡️ muscle cell (myofiber) ➡️ myofibril
Fascicle
Bundle of muscle cells
Muscle cell (myofiber)
Muscle fiber
Myofibril
Chain of sarcomeres
What is a sacromere
Made up of thick (myosin) and thin (actin) filaments
Sarcoplasm
Cytoplasm
Sarcolemma
Plasma membrane
Sarcoplasmic reticulum stores
Calcium ca+
What conducts Ap to the sacroplasmic reticulum?
Transverse (t) tubules
What is the flow of an action potential traveling down sarcolemma
Action potential down sarcolemma ➡️ t tubules ➡️ signals saroplasmic reticulum to release ca2+ ➡️ ca2+ bathes myofibers ➡️ initiating contraction
Sarcomere
Z disc to z disc
What are thick and thin filaments made out of?
Thick = myosin
Thin = actin
H zone
Thick filaments only
A band
Thick and thin filaments
I band
Thin filaments only ( from 2 sacromeres)
What causes striations in skeletal muscle?
Overlapping of thin and thick filaments
What happens when the sacromere shorten?
A band - stays the same
H zone- shrinks/ disappears
Z bands - shrink / get closer together
I bands - shrink
What are the binding sites on the thick filament?
Actin binding site & Myosin ATPase site
What is the binding site on thin (actin) filaments?
Myosin binding site
What are the two regulatory proteins found on thin filament?
Tropomyosin - covers myosin binding site
Troponin - holds tropomyosin in place
Cross bridge cycle
Myosin heads attach to thin filament
Mechanism of cross bridge cycle
Cross bridge forms b/w charged myosin head & actin
- Myosin head ratchets pulling actin
- Myosin heads releases from actin
- Myosin head recharged by ATP
How are myosin heads charged?
ATP binds to myosin ATPase site on myosin head ➡️ atp is hydrolyzed ➡️ phosphorylates myosin head charging myosin head
Power stroke
Myosin head ratchets pulling on thin filament
Cross bridge formation
Charged myosin head binds to actin ➡️shape change ➡️ phosphate releases
What is the role of ca2+ in relaxed muscles?
No calcium present therefore tropomyosin covers binding sites
What is the role of ca2+ in contracted muscles?
Ca2+ present therefore it binds to troponin
- troponin then removes tropomyosin allowing myosin head to bind to actin ➡️pulling ( shortening sarcomere)
Action potentials required for ca2+ to be released
True or false
True
Excitation contraction coupling
Turns Ap from motor neuron into Ap in sarcolemma to increase ca2+ concentration allowing for contraction to occur
Neuromuscular junction
Synapse b/w motor neuron and muscle cell
What are the three components in neuromuscular junction?
- Axon terminal (somatic motor neuron)
- Neuromuscular cleft (space)
- Motor end plate (muscle cell)
Activation of neuromuscular junction mechanism
- Motor neuron release actin potential
- Ca2+ enters voltage gated channel (depolarizing)
- Ach releases
- Ach binding opens ion channel
- Na+ enters
- Depolarizing end plate and adjacent muscle plasma membrane
- Muscle fiber action potential initiates
- Propagated action potential in muscle plasma membrane
- Ach is degraded
What is found in the motor end plate?
Nicotinic Ach receptors
What is found in the sarcolemma?
Voltage gated na+ channels
What are found in transverse (t) tubules?
Voltage gated ca2+ channel ➡️triggers ca2+ release channel
What are found in sarcoplasmic reticulum?
Mechanically gated ca2+ release channel
What are the two types of contractions?
Isotonic contraction = same tension; movement
Isometric contraction = same length ; no movement
Muscle twitch
Response to a single electrical stimulus
Summation
Increased frequency of stimulus producing end twitch before 1st can relax
Tetanus
Sustained Maximal contraction
Increased Ap frequency increases contraction strength
True or false
True
Graded contractions
Generating small to large forces for light vs small loads
How are graded contractions created?
- Increase action potentials frequency
- Recruit more motor units
- Optimize muscle length
Motor units (mu)
1 motor neuron + all muscle fibers innervated
Large vs small motor units
Large = gross motor skills
➡️ less precise (back)
Small = fine motor skills ➡️more precise (fingertips)
Less cross bridges = less force
True or false
True
Sustained contractions
Asynchronous activation of motor units
➡️ motor units take turns
What are the three muscle fiber types?
- Fast glycolytic
- Fast oxidative glycolytic
- Slow oxidative
How fast a muscle cell contracts/ twitches depends on….
- rates of cross bridge formation
- ATPase isoenzymes on myosin head
Slow oxidative
Aerobic respiration ( need oxygen)
- dense capillaries, lots of myoglobin, numerous mitochondria
Ex) postural muscles
Fast glycolytic
Anaerobic respiration (lacks oxygen)
- fewer capillaries, less myoglobin, fewer mitochondria, large glycogen stores
1 glucose ➡️2 atp
Ex) sprinting muscles (fatigue quickly)
Fast oxidative glycolytic
Aerobic/ anaerobic
- metabolically intermediate to slow oxidative and fast glycolytic
1 glucose➡️ 36 atp
Ex) endurance muscles
What fibers have more mitochondria
Slow oxidative
atp functions in muscle contraction cause….
- Bind to myosin releasing from actin ( relaxation)
- Phosphorylation of myosin = charged myosin head ( contraction)
- Primary active transport = ca2+ into sarcoplasmic reticulum ( relaxation)
What is used in the first 8 seconds of exercise?
Creatine phosphate
After two minutes of experience what is used?
Glycolysis
What type of exercise promotes weight loss?
Mild exercise
Golgi tendon organ
Senses muscle tension/ contraction
What does the golgi tendon organ protect us from
Prevents dangerous tension on tendon
- muscle tears / avulsion fracture
Muscle spindle
Senses muscle length/ stretch
The sensor for knee jerk reflex is
Muscle spindle organ
What does the muscle spindle organ protect us from doing
Prevents muscle tears
Why during the first two minutes of exercise we are unable to generate atp aerobically?
It takes some time for it to increase its spread for the increased demand of atp
Where is the muscle spindle located?
The belly of muscles
What fuels are stored in the body
Carbohydrates and fats
What form are fuels STORED in the body?
Fats = triglycerides
Carbohydrates = glucose 
What provides proper control of muscle function
A Somatic motor neuron & 2 sensors
