What is a primary tissue type?
• muscle tissue
What are the 3 divisions of a muscle tissue?
- Skeletal muscle tissue
- Cardiac muscle tissue
- Smooth muscle tissue
What does skeletal muscle tissue do?
- attaches tithe skeletal system
* allows us to move
What are the 6 functions of skeletal muscle tissue?
- Produce skeletal movement
- Maintain posture and body position.
- Support soft tissues
- Guard entrances and exits
- Maintain body temperature
- Store nutrient reserves
What are the components of skeletal muscle?
- Muscle tissue (connective cells/fiber)
- Connective tissue
- Nerves
- Blood vessels
What are the 3 layers of connective tissue?
- Epimysium
- Perimysium
- Endomysium
What is the Epimysium?
• exterior collagen layer
What is the Epimysium connected to?
• deep fascia
What does the Epimysium do?
• separates muscle from surrounding tissues
What is the Perimysium?
• fibrous connective tissue
What is the Perimysium rich in??
• rich is collagen and elastin
What does the Perimysium surround?
• muscle fiber bundles (fascicles)
What does the Perimysium contain?
• blood vessels and nerve supply for the fascicles
What is the Endomysium?
• delicates connective tissue layer
What does the Endomysium surround?
• individual muscle cells/fiber
What does the Endomysium contain?
- capillaries and nerve fibers contacting muscle cells
* myosatellite cells (stem cells)
What is another name for myosatellite cells?
•Stem cells
What does myosatellite cells do?
• repair damage
What happens when the Epimysium, the Perimysium and Endomysium come together??
• form connective tissue attachment
To what does the connective tissue attach to?
• bone matrix
What is the connective tissue called?
- tendon bundle
* aponeurosis sheet
What does muscles have ?
• extensive vascular systems
What does this vascular system supply to the muscle??
- oxygen
- nutrients
- carry away waste
How are the voluntary skeletal muscles controlled?
- nerves of the central nervous system
* brain and spinal chord
How do skeletal muscle cells develop?
• through the fusion of embryonic cells
How are the embryonic cells called?
• myoblast
How long can skeletal muscle cells be?
- 30 cm
* 12 inch
What does skeletal muscle cells contains?
• hundreds of nuclei
What is the sarcolemma?
• cell membrane of a muscle cell (fiber)
What does the sarcolemma surround?
• the sarcoplasm
What is the sarcoplasm?
• cytoplasm of a muscle cell
What begins contraction of a muscle?
• change in the transmembrane potential
What are the transverse tubules??
• narrow tubes that are continuous with the sarcolemma
What is another name for transverse tubules??
• T tubules
What do the T tubules do??
- transmit action potential through cell
* allow entire muscle to contract simultaneously
What are the properties of T tubules?
• same as sarcolemma
What ate myofibrils??
• lengthwise subdivision w/in muscle fibers
What makes up myofibrils?
• bundles of protein filaments
What are the protein filaments called??
• myofilaments
What are myofilaments responsible for?
• muscle contraction
What are the types of myofilaments?
- thin filaments
* thick filaments
What are thin filaments made up of?
• protein actin
What are thick filaments made up of?
• protein myosin
What is the sarcoplasm if reticulum (SR)?
• membranous structure surrounding each myofibril
What is the structure of Sarcoplasmic Reticulum?
• similar to Smooth ER
What does the sarcoplasmic reticulum do?
• forms chambers attached to T tubules
What are the chambers formed by sarcoplasmic reticulum called?
• terminal cisternae
What is a TRIAD composed of?
- 1 T tubule
* 2 terminal cisternae
What does ciaternae concentrate??
• Ca2+ via ion pumps
Where does the cisternae release the Ca2+?
• onto sarcomeres
Why does the cisternae release the Ca2+?
• to begin muscle contraction
What are sarcomeres??
• contractile units of muscles
How are myofibrils built??
• by 10k sarcomeres attached end to end
What do these sarcomeres form?
- visible patterns (stripes) w/in myofibrils
- dark thick filaments
- light thin filaments
What are the thick filaments called?
• A bands
What are the thin filaments called??
• I bands
Where do thick and thin filaments over lap??
• in the zone of overlap
Where does the M line occur?
• the Middle
What does the Z line mark?
• boundary between adjacent sarcomeres
What are thin filaments made up of?
- F-acting filamentous
- nebulin
- tropomyosin
- troponin
What is F-acting (filamentous)?
• 2 twisted rows of globular G-acting
What does the active (yellow) actin site do?
• Bind to myosin
What does Nebulin do?
• holds F-acting strands together
What does Tropomyosin do?
• prevents actin-myosin interaction
What does Troponin do?
• binds tropomyosin to actin
How is troponin controlled?
• by Ca2+
What does the thick filaments contain?
- about 300 twisted myosin subunits
* titin
What does Titin do?
• recoil after stretching
That does the tail of the myosin molecule do?
• binds to other myosin molecules
What does the head of myosin molecule do?
• teaches the nearest thin filament
What is the head of the myosin made up of?
• 2 globular protein subunits
What happens during contraction to myosin head?
- interact w/ actin filaments
- for cross-bridges
- pivot
How is contraction initiated?
- Ca2+ binds troponin molecule
- Troponin-tropomyosin complex changes shape
- Exposes active site of F-actin
What happens to thin filaments in filament theory?
• slide towards M line
What happens to the dark area of thick filaments in sliding filament theory??
• the width of A zone stays the same
What happens to the end of sarcomeres in sliding filament theory??
• Z line moves closer together
What does the process of contraction involve?
- Neural stimulation of sarcolemma
- Muscle fiber contraction
- Tension production
What happens in neural stimulation if sarcolemma?
• causes excitation-contraction coupling
What happens in over contraction??
• interaction of thick and thin filaments
What is the Neuromuscular Junction?
- NMJ
* special intercellular connection between the. Record system and a skeletal muscle fiber
What does the neuromuscular junction control?
• calcium ion release into the sarcoplasm
What is the synaptic cleft?
• narrow space that separates the axon terminal of the neuron from the opposing motor end plate
Step 1 of neuromuscular junction.
• cytoplasm of axon contains vesicles filled w: molecules of acetylcholine
What is acetylcholine? Stp1
• a neurotransmitter
What is a neurotransmitter? Stp1
• chemical released by a neuron to change the permeability or other properties of the cell’s plasma membrane
What is an action potential? Step2
• sudden change in the membrane potential that travels along the length of axon
What happens when the action potential reaches the neuron’s axon terminal? Step3
• change in the permeability triggers the exocytosis of ACh into the synaptic cleft
When does exocytosis occur? Stp3
• as vesicles fuse with the neuron’s plasma membrane
What is the 1st step of contraction cycle?
- Contraction cycle begins
• arrival of Ca2+
What is the 2nd step of contraction cycle?
- Active-site exposure
What is the 3rd step of contraction cycle?
- Cross-bridge formation
What is the 4th step of contraction cycle?
- Myosin head pivoting
What is the 5th step of contraction cycle?
• Cross-bridge detachment
What is the 6th step of contraction cycle?
- Myosin reactivation
How is tension produced?
- sarcomeres shorten
* muscle pulls together
Where can muscle shortening occur?
- both ends of muscle
* one end of muscle
What determines where the shortening happens?
• the way the muscle is attached at the ends
What does contraction duration depend on?
- neural stimulus
- number of free calcium ions in sarcoplasm
- availability of ATP
What happens when the muscle relaxes.
- Ca2+ concentration falls
- Ca2+ detached from troponin
- active sites are recovered by tropomyosin
Is contraction an active process?
• yes
What does SR release?
• Ca2+
What triggers contraction?
• Ca2+ in the sarcoplasm
What happens as thin filaments slide between thick filaments?
• skeletal muscle shortens
Is relaxation an active or passive process??
• passive
What does tension production depends on?
- number of pivoting cross-bridges
- fibers resting length at time of stimulation
- frequency of neural stimulation
What does a single. Rural stimulation produce?
• single contraction or twitch
How long does a single twitch last?
• 7-100 milliseconds
What does sustain muscular contraction require?
• many stimuli
What are the 3 stages of a twitch?
- latent period
- Contraction phase
- Relaxation phase
How long does latent period last?
• 2 msec
How long does contraction phase last
• 15 Msec
How long does relaxation phase last?
• 25 msec
What is a treppe?
- stair-step increase in twitch tension
* < 50/sec
What is same summation?
- increasing tension or summation of twitches
- repeated stimulation before end of relaxation
- > 50/ sec
What is Incomplete tetanus
• when rapid stimulus continues and muscle is not allowed to relax
What is complete tetanus?
- strings frequency is high enough
* relaxation phase is completely eliminated
What does motor units contain?
• 100s of muscle fibers that contract at the same time
What is isotonic contraction?
• skeletal muscle changes length
What are the 2 types of isotonic contraction?
- Concentric
* Eccentric
What is concentric contraction?
- muscle shortens
* tension is greater than load
What is eccentric contraction?
- muscle lengthens
* muscle tension is lesser than load
What is isometric contraction?
- skeletal muscle does not change in length
* still develops tension
What happens when as the heavier the load?
- longer time for shortening to begin
* less muscle will shorten
What is creating phosphate?
• storage molecule for excess ATO energy in testing muscle
What is aerobic metabolism??
• primary energy source of testing muscles
How many ATP are produced with aerobic metabolism?
• 34
What is anaerobic glycolysis?
• primary energy source of peak muscular activity
How many ATP are produced in anaerobic glycolysis?
• 2 ATP molecules per molecule of glucose
What happens in anaerobic glycolysis?
• breaks down glucose from glycogen stores I skeletal muscles
What happens when skeletal muscles are at rest?
- it metabolizes Fatty acids
* store glycogen, build CP reserves
What happens during moderate activity?
• generate ATO through aerobic breakdown of carb
What happens if glycogen reserves are low during moderate activity?
- uses lipids or amino acids
* ALL ATO is used as
What happens during peak activity?
- energy is provided by anaerobic reactions (glycolysis)
* generate lactic acid as byproduct
What are the results of muscle fatigue??
- depletion of metabolic reserves
- damage to the sarcolemma and sarcoplasmic reticulum
- low PH (lactic acid)
- pain
What happens in recovery period?
- oxygen becomes available
* mitochondrial activity returns
What is the cori cycle?
- removal and recycling of lactic acid
* glucose is released from the liver to recharge muscle
What is the oxygen debt?
Body needs more oxygen than usual to normalize metabolic activities
• heavy breathing
What is another name for oxygen debt?
• excess post exercise oxygen consumption (EPOC)
Up to what percent can be lost in heat?
• 70% of muscle energy
What is the only muscle tissue part of the muscular system?
• skeletal muscle tissue
What are the 4 hormones of muscle metabolism?
- Growth hormone
- Testosterone
- Thyroid hormone
- Epinephrine
What do fast fibers do?
• contract very quickly
Describe fast fibers
- larger in diameter
- large glycogen reserves
- few motors
- strong contraction
- fatigue fast
What do slow fibers do?
• contract slowly and slow to fatigue
Describe slow fibers
- small in diameter
- more mitos
- high oxygen supply
- contain myoglobin
What are intermediate fibers?
• mid sized fibers
Describe intermediate fibers
- resemble fast fibers
* have intermediate capillary network and mitochondrial content
What are white muscles mostly formed by?
• fast fibers
What are red muscles mostly formed by?
• slow fibers
What types of fibers do most humans have
- mixed fibers
* pink appearance
What is hypertrophy?
• muscle growth from heavy training
What happens in hypertrophy?
- increase diameter of muscle fiber
- increase number of myofibrils
- increase mitochondria
- increase glycogen reserves
What is atrophy?
• lack of muscle activity
What happens in atrophy?
- reduced muscle size
* reduce in tone and power
What kind of fibers are used in anaerobic activities?
• fast fibers
What are some examples of anaerobic activities?
- 59 meter dash
* weightlifting
What is aerobic activities?
- prolonged activities
- swimming
- jogging
- aerobic classes
How is aerobic activities supported?
• by mitochondria
How is aerobic endurance improved?
• training fast fibers to be more like intermediate fibers
Where are cardiac muscles found?
- only in the heart
* they are striated
Describe cardiac muscles
- small
- single nucleus
- short, wide T tubules
- no terminal cisternae
- are aerobic
- have intercalated discs
What are intercalated discs?
• specialized contact points between cardio cures
What are the functions of intercalated discs?
- maintain structure
* enhance molecular and connections to potentials
What are the functional characteristics of a cardiac muscle tissue?
- automaticity
- variable contraction tension
- extended contraction time
What is automaticity?
- contraction w/o neural stimulation
* co trolled by pace makers
What is variable contraction tension?
• controlled by nervous system
What is extended contraction time?
• 10x as long as skeletal muscle
Where does smooth muscle form?
- around other tissues
- integumentary
- digestive
- urinary
- reproductive system
What signals the stimulus for ACh release? Stp2
- arrival of an electrical impulse
* action potential at the axon terminal
What are the characteristics of smooth muscle?
- nonstriated tissue
* different internal organization of actin and myosin
Describe smooth muscle
- long and slender
- single central nucleus
- no T tubules myofibrils or sarcomeres
- No tendon or aponeuroses
- scattered myosin fibers
- thin filaments attached to dense bodies
- dense bodies transmit contraction from cell to cell