Muscular Tissue Flashcards
What are the 3 types of muscle tissue?
Skeletal
Cardiac
Smooth
what is the location of skeletal muscle?
On the bones
What is the function of skeletal tissue?
Move Bones
what is the appearance of muscular tissue?
Multi-nucleated and striated
what is the control of skeletal muscle?
voluntary
what is the location of cardiac muscle?
Heart
what is the function of cardiac tissue?
pump blood
What is the appearance of cardiac tissue
one nucleus striated and intercalated discs
what is the control of cardiac tissue
involuntary
what is the location of (visceral) Smooth muscle tissue?
various organs, GI tract
what is the function of smooth tissue?
various, peristalsis
what is the appearance of smooth tissue?
one nucleus and no striations
what is the control of smooth tissue?
involuntary
what is the overall function of muscular tissue?
producing body movements
stabilizing body positions
storing and mobilizing substance within the body
generating heat
what are the properties of muscular tissue?
Electrical excitability
contractility
extensibility
elasticity
how are muscles formed?
the fusion of myoblasts into skeletal muscle fibre
what are the components of a Sarcomere?
Z discs
A band
I band
H zone
M line
describe the Z discs
Narrow plate-shaped regions of dense material that separate one sarcomere from the next
describe A band
dark middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments
describe I band
Lighter less dense area of sarcomere that contains remainder of thin filament but no thick filaments , A Z disc passes through centre of each I band
describe H zone
narrow region in centre of each A band that contains thick filaments but not thin filaments
describe M line
region in centre if H zone that contains proteins that hold thick filaments together at centre of sacromere
what are the contractile muscle proteins?
Myosin
Actin
what are the regulatory muscle proteins?
Troponin
Tropomyosin
what are the structural muscle proteins?
Titin
Nebulin
Alpha-Actin
Myomesin
Dystrophin
what do the contractile proteins do?
Generate force during muscle contractions
describe Myosin
Contractile protein that makes up thick filament, consist of a tail and 2 myosin heads
describe Actin
Contractile protein that is the main component of thin filament, each actin molecule has a myosin binding site where myosin head of thick filament binds during muscle contraction
what do Regulatory Proteins do?
Proteins that help switch muscle contraction on and off
describe Tropomyosin
reg protein that is a component of thin filament, when skeletal muscle fibre is relaxed, tropomyosin covers myosin binding sites on actin molecules, thereby preventing myosin from binding to actin
describe Troponin
Reg protein that is a component of thin filament, when calcium ions bind to troponin, it changes shape, this moves tropomyosin away from myosin binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin
What do Structural Proteins do?
Proteins that keep thick and thin filaments of myofibrils in proper alignment, give myofibrils elasticity and extensibility and link myofibrils to sarcolemma and extracellular matrix
describe Titin
Structural protein that connects Z disc to M line of sarcomere, thereby helping to stabilize thick filament positions, can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils.
Describe Alpha-Actinin
Structural Protein of Z discs that attaches to actin molecules of thin filaments and to titan molecules
Describe Myomesin
Structural Protein that forms M line of sarcomere, binds to titan molecules and connects adjacent thick filaments to one another
Describe Dystrophin
Structural protein that links thin filament of sarcomere to integral membrane proteins in sarcolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers, thought to help reinforce sarcolemma and help transit tension generated by sarcomeres to tendons
what are thin filaments?
Actin
What are thick filaments?
Myosin
what are the levels of organization of skeletal muscle? (Outside-Inside)
Skeletal Muscle
Fascicle
Muscle Fiber
Myofibril
Filament
Describe Skeletal Muscle
organ made up of fascicles that contain muscle fibres, blood vessels and nerves, wrapped in epimysium
Describe Fascicle
Bundle of muscle fibres wrapped in perimysium
Describe Muscle Fiber
Long cylindrical cell covered by endomysium and scarolemma, contains sarcoplasm myofibrils, many peripherally located nuclei, mitochondria, transverse tubules, SR and terminal cisterns, the fibre has a striated appearance
describe Myofibril
Threadlike contractile elements within Sarcoplasm of muscle fiber that extends entire length of fibre, composed of filaments
Describe Filaments
contractile proteins within myofibrils that are of 2 types, thick filaments composed of myosin and thin filaments composed of actin, tropomyosin and troponin, sliding of thin filaments past thick filaments produces muscle shortening
what produces muscle shortening?
Sliding of thin filaments past thick filaments
what is the length tension relationship?
The force of a muscle contraction depends on the length of the sarcomeres in a muscle prior to contraction
How do muscles derive the ATP necessary to power the contraction cycle?
Creatine phospate
Anaerobic glycolysis
Cellular Respiration
describe Creatine Phosphate
creatine kinase catalyzes the transfer of a phosphate group from CP to ADP to rapidly yield ATP
describe Anaerobic Glycolysis`
When CP stores are depleted, glucose is converted into pyretic acid to generate ATP
describe cellular respiration
under aerobic conditions, pyretic acid can enter the mitochondria and undergo a series of O2 requiring reactions to generate large amounts of ATP
how long does the energy from CP last?
15 seconds
how long does energy last from Anaerobic Glycolysis
2 minutes
how long does energy last from cellular respiration?
several minutes to hours
what is muscle fatigue?
is the inability to maintain force of contraction after prolonged activity
what causes the onset of muscle fatigue?
Inadequate release of Ca2+ from SR
Depletion of CP, O2 and nutrients
Build up of lactic acid and ADP
Insufficiant release of ACh at NMJ
what is central fatigue?
occurs due to changes in the central nervous system and generally results in cessation of exercise
what does extra O2 go to after exercise?
Replenishing CP stores
Converting lactic acid to pyruvate
Reloading O2 onto myoglobin
what does the strength of a muscle contraction depend on?
how many motor units are activated
what does a motor unit consist of?
a somatic motor neuron and the muscle fibres it innervates
what is motor unit recruitment?
is the process in which the number of active motor units increases
what is a twitch contraction
The brief contraction of all muscle fibres in a motor unit response to a single action potential.
what are the steps of the twitch contraction?
latent period
contraction period
relaxation period
refractory period
what is isotonic contractions?
tension is constant while muscle length changes (moves)
concentric
eccentric
what is isometric contractions?
muscle contracts but does not change length (Doesn’t Move)
what are intercalated discs?
part of cardiac muscle, the contain desmosomes and gap junctions that allow muscle action potentials to spread from one muscle fibre to another
what does cardiac muscle have more of than skeletal muscle?
Mitochondria, their contractions last up to 10-15 times longer than skeletal.
Describe Electrical Exciteablility
The ability to respond to certain stimuli by producing electrical signals called action potentials
Describe Contractility
Ability of muscular tissue to contract forcefully which stimulated by nerve impulses
Describe extensibility
Ability of muscular tissue to stretch within limits without being damaged
What limits the muscles range of stretch?
Connective tissue
Describe elasticity
Ability of muscular tissue to return to its original length and shape after contraction
What is the hypodermic composed of?
Areolar connective tissue and adipose tissue
What does the hypodermis provide?
Pathway for nerves blood vessels and lymph vessels to enter and exit muscles
What does the adipose tissue store
Tryglycerides
What does the adipose tissue serve as?
Insulating layer, reduces heat loss and protects muscles from physical trauma
What is fascia
Dense sheet of connective tissue that lines the body wall and limbs and supposed and surrounds muscles and other organs
What is the epimysium
Outer layer encircling the entire muscle, consists of dense irregular connective tissue
What is the perimysium
Layer of dense irregular connective tissue, surrounds groups of 10-100 muscle fibers, making bundles called muscle fascicles
What is the endomysium
Penetrates the interior of each muscle fascicle and separates individual muscle fibers from one another
What neurons stimulate skeletal muscle to contract
Somatic motor neurons
Which proteins connect into Z disc?
Titian and nebulin
Which proteins are present in the A band?
Myosin
What protein is present in I Band
Actin
What happens to the I band and the H zone as muscles contract
They get shorter
