Muscular System Flashcards
What are the 3 results of movement created by muscles?
- Muscles pull bones to initiate movement in the joints
- Muscles pull on soft tissue in the face to create expressions
- Respiratory muscle movements causes breathing
How do muscles relate to blood circulation?
Cardiac muscle helps to pump blood into and out of the heart
What is the benefit of muscles generating heat?
Heat is a waste produce of muscles that helps maintain an internal body temperature
What is the benefit of muscles aiding in support?
Muscles on the body wall help support the internal organs
In what way do muscles protect?
They cushion internal organs from exterior forces
What is myology?
Study of the structure, arrangement, and action of muscles
What are the three types of muscles?
Skeletal, Smooth, Cardiac
What is the structure of skeletal muscle?
Striated (having lines), tubular, and multinucleated
What type of control are skeletal muscles under?
Voluntary control
Where are skeletal muscles usually attached?
To the bone via tendons
Where are skeletal muscles typically found?
Throughout the body, making up most of the muscle in it
What is the structure of smooth muscle?
Non-striated (no lines), spindle-shaped, single nucleated
What type of control are smooth muscles under?
Involuntary control, controlled by the autonomic nervous system
Where are smooth muscles found?
Blood vessels, digestive tracts, respiratory tissue, reproductive tissue
What is the structure of cardiac muscle?
Striated (lines), branched, single nucleated
What kind of control are cardiac muscles under?
Involuntary control
Where is cardiac muscle found?
Only in the heart where it’s found significantly in the walls of the heart
What is muscle contraction?
The tightening, shortening, or lengthening of muscles
What is muscle relaxation?
The passive process of returning to a resting state
How are muscle fibers arranged?
In bundles surrounded by fibrous connective tissue
What is endomysium?
The thin layer of connective tissue covering individual muscle fibers
What is the sarcolemma?
The cell membrane of the muscle fiber
What is the perimysium/muscle fascicle?
The connective tissue surrounding bundles of muscle fibers
What is the epimysium/deep fascia?
The connective tissue surrounding an entire muscle
What is the muscle origin in the limbs?
The more proximal attachment
What is the muscle insertion in the limbs?
The more distal attachment
What is the muscle origin in non-limbs?
The less mobile attachment
What is the muscle insertion in non-limbs?
The more moveable attachment
What does it mean when a muscle has heads?
When a muscle has more than one origin but one insertion, the divisions are called heads
What is a flexor?
A muscle on the side of a joint that bends
What is an extensor?
A muscle on the side of the joint hat extends (increases the joint angle)
What is an adductor?
A muscle that pulls a limb toward the medial plane
What is an abductor?
A muscle that pulls a limb away from the medial plane
What is a sphincter?
A muscle that encircles an opening
What are cutaneous muscles?
Muscles found in the superficial fascia, which is between the skin and the epimysium covering the skeletal muscles
What are the synovial structures of the body and what do they consist of?
Joint capsules, bursae (closed sac), and synovial (tendon) sheaths
The inner layer of each has a connective tissue membrane that secretes synovial fluid to reduce friction
What are extrinsic muscles in the thoracic limb?
Muscles that have one attachment to the neck/trunk and one attachment to the appendicular skeleton
How are pelvic limbs attached to the axial skeleton
By a synovial ball and socket joint known as the coxofemoral, or hip, joint
What type of movement do joints primarily allow below the hip joint?
Flexion and extension
What are muscles of mastication?
Muscles that have one attachment to the mandible and move the jaw to create chewing motions
What are mimetic muscles?
Muscles that move the skin and appendages on the face to produce facial expressions
What are extraocular muscles?
Striated muscles that attach to the eye and move it in many directions
What is delgutition?
The sensation of swallowing, which involves muscles associated with the pharynx and soft palate
What is phonation?
The sensation of vocalizing, which involves muscles associated with the pharynx and soft palate
What are the functions of muscles around the pharynx?
To lift or depress the palate and to constrict or dilate the pharynx
What are the four groups of muscles in the trunk and neck?
- Extensors of the vertebral column
- Flexors of the vertebral column
- Abdominal muscles
- Respiratory muscles
What are muscles cells specialized to do?
Contraction
What is the smallest contractile unit of the muscle?
Sarcomere
What is the interior of a muscle fiber filled with?
Myofibrils, which are bundles of long protein strands
What fills the space between myofibrils?
Sarcoplasmic reticulum, a network of smooth ER, and T tubules, tubular invaginations of sarcolemma
What surrounds individual muscle fibers?
Endomysium
What surrounds bundles of muscle fibers?
Perimysium
What surrounds everything in the muscle and holds it all in place?
Epimysium
What is the sarcolemma?
The outer cell matrix/membrane of the muscle fiber
What do multiple nuclei right below the sarcolemma indicate?
That there was end-to-end fusion of shorter, primitive muscle cells during development
What is a myofibril formed out of?
Many sarcomeres fusing together
What are the two types of filament within a myofibril and what do they consist of?
Thin filament consisting mainly of actin
Thick filament consisting mainly of myosin
What are the two main regions of the sarcomere?
Filaments and Bands, Zones, and Lines
What makes up the filament region of the sarcomere?
Thick and thin filament
What makes up the bands, zones, and lines region of the sarcomere?
I bands, A bands, H zones, M lines, and Z lines/discs
What is an I band?
The region of the sarcomere where only thin filament exists. Crosses over Z discs
What is an A band?
The region of the sarcomere where both thick and thin filament exist. Crosses over the M line
What is an H zone?
The region of the sarcomere where only thick filament exists and becomes smaller during contraction. Crosses over the M line
What is an M line?
A vertical line at the midpoint between the Z lines/discs
What is a Z line/Z disc?
The area between sarcomeres that is heavier to help hold the sarcomere together
What is the approximate composition of muscle?
Water ~75%
Protein ~18%
Fat ~3%
Inorganic minerals ~2.5%
Carbohydrates <1%
What are the three categories of muscle proteins?
- Myofibrillar proteins
- Sarcoplasmic proteins
- Stromal proteins
How do each of the three categories of muscle proteins differ?
In cellular location, function, and solubility
What are myofibrillar proteins?
Structural proteins that make up the myofibril
What are the three subgroups of myofibrilar proteins?
Major contractile proteins, regulatory proteins, cytoskeletal proteins
What is the main purpose of major contractile proteins and what are two examples?
Muscle contraction
Actin and mysoin
What is the main purpose of regulatory proteins and what are two examples?
Initiate, control, and terminate contraction
Troponin and tropomyosin
What is the main purpose of cytoskeletal proteins and what are two examples?
Support and alignment
Titin, Dystrophan, and Nebulin
What protein makes up 45% (the largest proportion) of myofibrillar proteins in muscles?
Myosin
Describe the shape of a myosin protein.
Elongated and rod-shaped with a very high molecular weight.
There are two heavy chains. Each contains a head and an alpha helix tail. Each of the heavy chains is paired with two light chains, which can be separated when certain enzymes are active
Why does myosin play an important role in muscle contraction?
The heads are motor proteins that are responsible for making muscles work
What does actin consist of?
Two chains of F-actin from from individual G-actin molecules
What is the shape of tropomyosin?
Rod-like protein
How does tropomyosin relate to actin’s double helix?
It wraps around actin and inserts itself into the grooves of the helix
What does troponin do?
Wraps itself around actin’s helix like tropomyosin
What are the three types of troponin and what does each do?
Troponin C (TnC)- binds Ca2+
Troponin I (TnI)- inhibits ATP
Troponin T (TnT)- binds tropomyosin
What are sarcoplasmic proteins responsible for?
Metabolism
Where are sarcoplasmic proteins found?
In the sarcoplams or in the fluid surrounding myofibrils
What are sarcoplasmic proteins mostly made of?
Oxidatvie enzymes, heme pigments like myoglobin (responsible for red color of muscle), lysosomal enzymes, and nucleoproteins
What do stromal proteins mainly consist of?
Collagen and elastin
What are the 5 key events of muscle contraction?
- Action potential
- Calcium release
- Calcium exposes binding sites
- Myosin binds to actin
- Contraction is turned off and muscle returns to a relaxed state
What does the action potential signal?
Contraction which is voluntarily triggered by the brain and transmitted to the muscle from reflex activity in the spinal cord
What is the second step of the action potential phase?
Action potential arrives at the neuromuscular junction and brings an influx of Calcium with it
What does the influx of Calcium release and where does it release it?
It releases acetylcholine into the extracellular space between the nerve and the muscle
What does acetylcholine bind with to do?
Binds withr eceptors on the muscle fiber’s cell membrane and opens Ca2+-Na+ channels to help transmit the action potential
What does the action potential travel along within the muscle?
T-tubules
What is a motor unit?
A group of muscle fibers innervated by a singular neuron
Why is there a difference in the number of muscle fibers included in a motor unit?
A muscle that requires more delicate and precise movements will have less fibers in its motor unit so it has better control than something that needs power with a lot of fibers in its motor unit
When the action potential moves through the T-tubules, what is depolarized?
The interior of the muscle fiber
What does depolarizing the muscle fiber do?
Activates voltage gated Calcium channels in the sarcoplasmic reticulum (muscle ER) to release Calcium into the sarcoplasm (muscle cytoplasm)
Once Calcium is released, what does it bond to and where is it found?
Troponin C on the actin thin filaments
What does Calcium binding to troponin C do?
It changes the troponin complex shape, shifting tropomyosin out of the way and exposing the myosin and actin binding sites
What is myosin’s ready position?
Myosin bound with ADP and inorganic phosphate
How is myosin able to attach to actin?
By breaking down ATP into ADP and an inorganic phosphate
What enzyme breaks down the ATP on myosin?
Myosin-ATPase
When myosin bonds with actin, what is formed?
Cross-bridges
What is the power stroke?
When myosin changes shape by releasing an inorganic phosphate and ADP, which allows it to attach to actin and pull it forward
What does the the changing of myosin’s shape in the power stroke do?
It pulls on actin and moves the Z-lines closer together
What causes myosin to release actin?
Binding ATP to myosin
What are the 5 steps of the relaxation phase?
- Nerve signal weakens
- Sarcolemma and T-tubule are repolarized and ready for the next signal
- Cross bridges break and can’t reform
- Tropomyoisn moleceules recover the myosin-actin binding sites
- The sarcomeres and the filaments passively return to their resting state
What molecule is required for muscle contraction?
ATP
What type of energy from ATP is converted to what type of energy during muscle contraction?
Chemical energy converted to electrical energy
What molecule is required to break the actin/myosin bond and end contraction?
ATP
What does a current lack of ATP cause in the muscle?
Muscle cramping
What does a permanent lack of ATP cause in the muscle?
Rigor mortis
What enzyme creates ATP from the ADP and phsophate released by the myosin?
ATP synthase
Where does ATP creation take place in animals?
Mitochondria
What flows into the mitochondria via ATP-synthase that helps convert ADP to ATP
Hydrogen
How does ATP breakdown and reforming work?
It is broken down to a lot of percursors before it can be resynthesized
What are the 3 ATP generating pathways in muscle?
Phosphocreatine, glycolysis, Citric Acid/Krebs/TCA cycle
What is the goal of phosphocreatine?
Phosphocreatine is converted into creatine
What is the goal of glycolysis
Glucose is coverted to pyruvate of lactic acid
Where can glucose originate for glycolysis?
From diet or from glycogen, which is stored glucose within muscles and organs
What is the precursor of the TCA cycle?
Amino acids and glucose/pyruvate are converted to acetyl CoA in the presence of oxygen to enter the cycle
What is the main limitation of the TCA cycle?
Can only happen in aerobic environments
What is the outcome of glycolysis?
Pyruvate, ATP, and NADH
What happens to pyruvate in anaerobic conditions?
It is converted to lactate where it is transported to the liver and metabolized back to glucose through gluconeogenesis
What happens to pyruvate in aerobic conditions?
It enters the TCA cycle to be used to produce ATP along with NADH also producing ATP in the electron transport system
What is the TCA cycle?
A series of chemical reactions that releases stored energy by oxidizing acetyl-CoA
How is acetyl-CoA obtained?
From carbohydrates, fats, and proteins, from pyruvate converted to acetyl CoA, and from fatty acids or amino acids converted to acetyl CoA, which is the starting point of the TCA cycle
What are the advantages of the TCA cycle?
Produces much more ATP than glycolysis alone (36 vs 6)
Allows for production of ATP from several fuel sources (carbs, fatty acids, amino acids), where glycolysis has to start at glucose
What are disadvantages of the TCA cycle?
It’s slower and it requires oxygen, which is in short supply during exercise
What are the three types of ATP generation initiating compounds?
- Phosphocreatine
- Carbohydrates
- Fatty Acids or Amino Acids
How does phosphocreatine produce ATP?
It provides a quick burst of ATP and is used rapidly and exhausted within seconds of exercising
How do carbohydrates produce ATP?
The main carbohydrate thought of here is glucose. This is the second most abundant ATP precursor after phosphocreatine, but can be depleted quickly after exercise
ATP production is limited in anaerobic environments, but carbohydrates are the only choice in an anaerobic environment
How do fatty acids or amino acids produce ATP
They have a higher “staying power” since it’s hard to deplete fat and protein reserves
Needs oxygen to be used
What are muscle fiber/muscle cell types?
Difference between muscle fibers/cells that vary among different muscles and species depending on the work the muscle needs to perform
In what ways can muscle fibers be classified?
By metabolism, speed of contraction, strength/endurance, color, composition, and the myosin heavy chain and which enzymes are on it
What can muscle fibers do depending on their living conditions?
Adapt and change their type
What color fibers are used to aide activity over long periods of time?
Red fibers
What color fibers are used to aide activity in short bursts?
White fibers
What are the two classifications of muscle based on metabolism preference?
Oxidative and glycolytic
Can any muscle type use any type of fuel?
Yes, but muscle types have a greater affinity for certain fuels over others
What type of fuel do oxidative muscles primarily use?
Lipids
What kind of fuel do glycolytic muscles primarily use?
Glucose
What type of muscle classified based on metabolism affinity is better suited for constant use and sustained and constant energy?
Oxidative
What are the two color classifications of muscle?
White/Light and Red/Dark
What is muscle color derived from?
Muscle pigment
What is muscle pigment
The concentration of a sarcoplasmic protein called myoglobin, which transports oxygen
more myoglobin = darker = more oxygen
What color muscle cells are more oxidative and what color are more glycolytic?
Red/dark more oxidative
White/light more glycolytic
What is the rate limiting step of contraction?
The action of myosin-ATPase that converts ATP into ADP and Phosphate
Which muscle classifications based on speed are more oxidative and which are more glycolytic
Fast muscles are oxidative
Slow muscles are glycolytic
Which has more endurance and which has more power/strength- a wild duck and a domestic chicken?
A wild duck has more endurance and a domestic chicken has more power/strength
What are the two things that muscles built for power need?
A quick fuel supply and a rapid contraction pattern
What are the two things that muscles built for endurance need?
A constant fuel supply and an efficient contraction pattern
What three classifications are typically associated with power muscles?
Glycolytic, fast, and white/light
What three classifications are typically associated with endurance muscles?
Oxidative, slow, and red/dark
What four classifications are typically associated with oxidative muscles?
- Red/dark
- Slow
- Endurance
- High fat content
What four classifications are typically associated with glycolytic muscles?
- White/light
- Fast
- Power
- Low fat content
What part of myosin is considered the heavy chain?
Head and alpha-helix tail
What part of myosin is considered the light chain?
The two molecules that bind to the tail right below the head
Where is ATPase found in myosin?
Head
What are the 4 types of myosin heavy chain forms?
Type I, Type IIA, Type IIX, and Type IIB
How are the types of myosin heavy chains classified?
Based on the speed of ATPase in them, which affects the speed of contraction
Rank the speeds of myosin heavy chain types from fastest action to slowest
IIB > IIX > IIA > I
Do all animals have all classifications of myosin heavy chains?
No
How do myosin heavy chains change with different metabolistic needs throughout life?
They can transition to a different type
What are the five classifications associated with Type I MHC?
Oxidative, red/dark, highest fat, slowest, endurance based
What are the five classifications associated with Type IIA MHC?
Oxidative and glycolytic, red (lighter than Type I), high fat, slow, endurance based
What are the five classifications associated with Type IIX MHC?
Glycolytic, white (darker than Type IIB), low fat, fast, power based
What are the five classifications associated with Type IIB MHC?
Glycolytic, white/light, lowest fat, fastest, power based
What are the 5 main functions of muscle?
- Movement
- Blood circulation
- Heat generation
- Support
- Protection
