Muscle and Tendons Flashcards
1
Q
Describe the gross structure of skeletal muscle. Describe what muscles are made of?
A
Gross structure of skeletal muscle:
-each of body’s skeletal’s muscles contains various wrapping of *fibrous connective tissue
each muscle is made up of thousands of *fibers (cylindrical cells) that lie parallel to each other; with force of action directed along fiber’s long axis
Fiber length varies from few milimeters in eye muscles to nearly 30 cm in large muscles of leg.
2
Q
describe the levels of organization of skeletal muscle? describe each layer of muscle and its role.
A
Levels of organization in skeletal muscle:
- Epimysium surrounds Entire MUSCLE and then blends into the intramuscular tissue sheets to form tendons
- Perimysium- surrounds a bundle of fibers called a FASICULUS
- Endomysium- wraps each MUSCLE FIBER and Separates it form neighboring fibers
- Sarcolemma-surrouinds each muscle fiber sand encloses the fiber’s cellular contents
- Sarcloplasm- contains the NUCLEI that contain genes, mitochondria and other specialized organelles
- Sarcoplasmic reticulum provides STRUCTURAL INTEGRITY to the cell.
order: tendon -> paratendon-> fascicle-> fibril-> subfibril-> microfribil-> tropocollagen
3
Q
Describe the skeletal muscle structure. include role of tendon, and what occurs during muscle action. What is origin of muscle? What is insertion?
A
Tendons connect both ends of muscle to periosteum , the bone’s outermost covering
force of muscle action transmits directly from the connective tissue harness to the tendons, which then pulls on the bone at the point of attachment.
origin of muscle- location where the tendon joins a relatively stable skeletal part, generally the Proximal end
-Insertion of a muscle- point of distal muscle attachment to moving bone
4
Q
Describe the composition of skeletal muscle composition. What are the most abundant muscle proteins?
A
Skeletal muscle composition: Water= 75% Protein= 20% -myosin, actin, and tropomyosin, are the MOST ABUNDANT muscle proteins Salts and other substances= 5%
5
Q
Explain the blood supply to skeletal muscle, including what it comprises of and why it is necessary. Why is this blood supply used during exercise?
A
blood supply to skeletal muscle
-Arteries and veins lie PARALLEL to individual muscle fibers
-these divided into numerous arterioles, capillaries and venues to form a Network in and around the endomysium
This extensive branching ensures Adequate oxygen and rapid removal of Oxygen (and lactic acid).
During intense exercise, the vascular bed delivers large quantities of blood through active tissues to accommodate the increased oxygen need (vascular debt)
Physical activities that require straining elevate intramuscular pressure to occlude (restrict) local blood flow during muscular contractions.
6
Q
Explain the role of Capillarization during exercise and compare this in trained vs untrained individuals.
what stimulates capillary development?
A
Capillarization:
- A trained muscle has an INCREASED capillary-to-muscle fiber ratio (more capillaries per muscle fiber help deliver O2 better)
- This enhanced capillary microcirculation expedites (speeds up) the removal of heat and metabolic byproducts from active tissue in addition to Facilitating delivery of oxygen, nutrients and hormones
-Total number of capillaries per muscle averages 40% higher in ENDURANCE-TRAINED athletes than untrained counterparts.
vascular STRECH and Shear stress on vessel walls from increased blood flow during exercise stimulates capillary development in intense aerobic training
7
Q
discuss the skeletal muscle ultrastructure, including what composes of myofibrils and muscle fibers. What accounts for majority of myofribillar complex?
A
Skeleteal muscle ultrastructure
-a single multinucleated muscle fiber contains MYOFIBRILS that lie parallel to fiber’s long axis
-myofibrils contain smaller subunits called MYOFILAMENTS the that lie parallel to long axis of myofibrils
Myofilaments consist of Actin and Myosin that account for 85% of the myofibrillar complex
-other proteins either Serve a structural function or affect protein filament interaction during muscle action
-tropomyosin, troponin, alpha-actinin, Beta-actinin, M protein, and C protein.
8
Q
Describe the cross-section of sarcoplasmic reticulum and other structures that are composed of it.
A
Cross section of sarcoplasmic reticulum includes:
myofibrils, sarcolemma, mitochondria, nuclei, traverse table and terminal cistern, myofilament (a band, I band, Z line)
9
Q
Describe the components of the sarcomere and well as the kind of pattern a myofibril has.
A
Myofibril has a cross-striation pattern
In Sarcomere:
I band represents the LIGHTER area
A band represents the DARKER area
- the center of the A band contains the H zone
-M band Bisects the H Zone and consists of protein structures that support the arrangement of myosin filaments
Z line Bisects the I band and adheres to Sarcolemma to provide STABILITY
10
Q
What structure is the area of overlap between the thick and thin filaments?
A
A Band
11
Q
what does sarcomere consist of and describe its position with regard to muscle fiber?
A
Sarcomere consists of basic repeating units between two Z Ines, comprising the FUNCTIONAL UNIT of muscle fiber.
Sarcomeres lie in SERIES, and their filaments have. a parallel configuration within a given fiber
12
Q
What determines a muscle’s functional properties?
A
LENGTH of SARCOMERE
13
Q
Describe the affect of muscle fiber alignment on muscle action. What are the main types of muscle forms?
A
Differences in sarcomere ALIGNMENT and LENGTH strongly affect a muscles Force and power-generating capacity
muscle forms:
-Fusiform
-pennate
14
Q
Explain how pennate muscles differ from fusiform fibers
A
Pennate muscles differ from fusiform fibers:
1. They generally contain SHORTER fibers
2, They possess more INDIVIDUAL fibers
3. They exhibit LESS RANGE OF Motion
15
Q
Describe the characteristics and function of fusiform fibers
A
Fusiform, or SPINDLE-SHAPED fibers run PARALELL to muscle’s long axis and taper at the tendinous attachment
- the fibers run parallel to muscle’s long axis, so Fiber length = muscle length
- this arrangement facilitates RAPID muscle SHORTENING
- Rapid muscle contraction (SPEED)
16
Q
What are the characteristics of pennate muscle fibers? Include the different types and its function.
A
Pennate fibers lie at an OBLIQUE PENNATION ANGLE and allow a large number of fibers into a smaller Cross sectional area
- types of pennate fibers: Unipennate, bipinnate, multipennate
- the degree of pennation directly impacts sarcomere number of fibers per cross-sectional muscle.
- allows individual fibers to remain short while the overall muscle may attain considerable length
- pennate muscles tend to generate considerable POWER
- they also are used for strength and power
17
Q
Explain the relationship between muscle fiber length and velocity, or power.
A
As muscle fibers get longer, they INCREASE VELOCITY
as muscle fibers get longer, they DECREASE POWER (and force)
shorter fibers have greater force, and will eventually reach peak force, before plateau (at 100 mm in length)
18
Q
Which type of muscle fibers are in hamstrings, quadriceps, dorsiflexors (shins) and plantar flexors (shins, and foot)?
A
Pennate muscles are seen in these body parts
- hamstrings- unipennate, use for velocity)
- quadricepts- bipennate, use for force)
- Dorsiflexors- unipennate, use for velocity
- Plantar flexors- multipennate, use for Force
19
Q
Explain the components of complex fusiform arrangement
A
Complex fusiform arrangement:
- Features individuals fibers that run parallel to muscles line of pull
- this arrangement features muscle fibers that terminate in the muscle’s mid belly and taper to interact with the connective tissue matrix, and/or adjacent muscle fibers
- this enables parallel packing of relatively short fibers within long muscles.
- this structural specialization creates lateral tension at various points along fiber’s surface.
20
Q
What is role of tedious intersection between muscles?
come back?
A
Tendinous intersection between muscle allows for increased fiber length and maintains power.
Short muscle fibers are in series, collectively forming large muscle fibers.
21
Q
Describe the ratio of fiber length to muscle length and how significance of this.
A
Fiber-length- Muscle length Ratio
- the ratio of individual fiber length to a muscles Total length usually varies between 0.2 and 0.6
- Therefore INDIVIDUAL fibers in longest muscles such as upper and lower limbs remain significantly SHORTER than muscle’s overall length.
22
Q
Describe the actin-myosin orientation. What do myosin and actin filaments structures compose of? how many thick and thin filaments are composed of 1 single fiber?
A
Thousands of myosin filaments lie along the line of actin filaments in a muscle fiber
-myosin filaments consist of bundles of molecules with polypeptide TAILS and GLOBULAR heads
-Actin filaments have two-Twisted chains of. MONOMERS bound by Tropomyosin polypeptide chains
-Six THIN Actin Filaments encircle the THICKER myosin filament
in a single fiber, this arrangement consists of approximately 16 billion thick filaments and 64 billion thin filaments
23
Q
What does thick and thin filaments compose of?
A
Thick filaments- composed of MYOSIN
Thin filaments- composed of Actin, troponin, tropomyosin
24
Q
Explain the role of cross bridges and what its components are and how it works. What is role of tropomyosin and troponin.
A
cross bridges
- globular myosin heads extend perpendicularly to latch onto double-twisted actin strands to create structural and functional links between myofilaments
- ATP hydrolysis activated myosin’s two heads, placing them in an optimal orientation to bind actin’s active sites
- This pulls the thin filaments and Z lines of sarcomere toward the middle
- Tropomysin and troponin regulate the Make and break contacts between myofilaments during muscle action.
25
Discuss the steps that occur in muscle contraction process.
Muscle contraction:
1. sac-like vesicles within terminal axon release Ach (Acetylcholine) , which diffuses across the synaptic cleft and attaches to specialized ACh receptors on the sarcolemma
2. Muscle action potential depolarized transverse tubules at the sarcomeres A-1 junction
3. T-tubule system depolarization causes Calcium release form sarcoplasmic reticulum lateral sacs
4. Calcium binds to troponin-tropomyosin in actin filaments, which releases inhibition of actin combining with myosin
5. Actin joins myosin ATPASE to split ATP with energy release during muscle action. Tension form energy release produces myosin cross bridge movement
6. a muscle shortening occurs after ATP binds to myosin cross bridge, which breaks the actin-myosin bond and allows cross bridge dissociation from actin and sliding of thick and thin filaments to occur
7. Calcium removal restores troponin-tropomyosin inhibitory action. With ATP present, actin and myosin remain in dissociated Relaxed state
8. when muscle stimulation ceases, Calcium moves back into sarcoplasmic reticulum, sacs through actin transport via ATP hydrolysis
9. Crossbridge activation continues when calcium concentration remains high (from membrane depolarization) to inhibit troponin-tropomyosin action.
26
Explain the role of intracellular tubule systems in muscle contraction process. When does muscle action begin? How does a muscle eventually relax?
Intracellular Tubule Systems
- the lateral end of each tubule channel within a muscle fiber terminates in a sac like vesicle that stores CALCIUM
- T-tubule system runs perpendicular to myofibril and functions as a MICROTRANSPORTATION Network by spreading the action potential from the fiber's outer membrane inward
- Calcium is released, which diffuses a short distance to Activate the actin filaments
- muscle action begins when myosin filament cross bridges momentarily attach to active sites on the actin filaments
- when electrical excitation ceases, calcium concentration in cytoplasm decreases and muscle relaxes.
27
What is the sliding-filament model and explain how this model describes muscle action. Explain what makes Crossbridges interact with Actin, and how sarcomere functions .
Sliding filament model:
-proposes that a muscle Shortens or Lengthens because the Thick and Thin filaments slide past each other WITHOUT Changing length
-myosin cross bridges cyclically attach, rotate and detach from actin filaments with Energy from ATP hydrolysis
-this produces a change in relative SIZE within the Sarcomere's Zones and Bands and produces a FORCE at Z bands.
I Band DECREASES as the Z bands are pulled toward CENTER of each sarcomere
28
Compare and contrast the image of a fully relaxed sarcomere, compared to image of fully contracted sarcomere
Fully relaxed sarcomere: normal Z line and I band length
| *Fully contracted sarcomere: Shorter gap between Z lines , reduction in H zone; Z band and I band become SHORTER
29
compare and contrast an isometric and eccentric muscle action and what happens to I and A bands
Isometric muscle action- the fibers length remains UNCHANGED, so the relative spacing of I and A band remains CONSTANT
Eccentric muscle action- the A Band Widens, as fiber LENGTHENS during force generation
30
List the sequence of events in muscle action?
1. generation of action potential in motor neuron causes the terminal axon to release Ach, which diffuses across synaptic cleft and attached to specialized ACh receptors on sarcolemma
2. the muscle action potential depolarizes the transverse tubules at the sarcomere's A-I junction
3. Depolarization of T-tubule system causes calcium to be released from lateral sacs of sarcoplasmic reticulum
4. Calcium binds to troponin-tropomyosin in the actin filaments, releasing the inhibition that prevented actin from combining with myosin
5. Actin combines with Myosin-ATP, as well as activates Myosin ATPASe, which then splits ATP
the reaction's energy produces myosin crossbridge movement and creates tension
6. ATP binds to myosin-crossgbridge; this breaks the actin-myosin bond and allows the crossbridge to dissociate from actin
-the thick and thin filaments slide past each other and muscle shortens
7. crossbridge activation continues when calcium concentration remains high enough to inhibit the troponin-tropomyosin system.
8. When muscle stimulation ceases, intracellular calcium rapidly decreases as calcium moves back into lateral sacs of sarcoplasmic reticulum through active transport that requires ATP hydrolysis.
9. Calcium removal restores the inhibitory action of troponin-tropomyosin
-in the presence of ATP, actin and myosin remain in dissociated, relaxed state.
31
explain how the two main types of fibers in skeletal muscle differ?
How do these fibers vary?
Skeletal muscle contains two main types of fibers (fast-twitch and slow-twitch) that differ in:
-the primary mechanisms that they use to produce ATP
-the type of motor neuron innervation
-the type of myosin heavy chain expressed
The proportions of each type of muscle fiber VARY from muscle to muscle and form person to person
32
What kind of instrument is used in muscle biopsy and how does this procedure work
NEEDLE muscle biopsy- involves the extraction of muscle from person's body through suction, using tool with outer needle, circular guillotine, syringe (generates suction) and plunger.
The muscle extracted will then be fixed and processed.
33
What are the two types of muscle fibers?
Fast twitch and slow-twitch fibers
34
Describe the characteristics of Fast-twitch fibers? Is it a type I or II?
Fast-twtich type fibers (TYPE II)
- 4 characteristics
-HIGH capability for electrochemical transmissions of action potentials
-High myosin ATPase activity
-RAPID Calcium release and uptake by an effecient sarcoplasmic reticulum
-HIGH rate of crossbridge turnover
These factors contribute to this fiber's RAPID, Energy generation for QUICK, powerful muscle actions.
this muscle fiber fatigues quickly, but contracts more quickly.
35
Describe the type of system used for fast twitch- fibers and where these fibers dominate in sports
- the fast-twitch fiber's Intrinsic SPEED of SHORTENING and Tension Development ranges 3 to 5 times FASTER than slow-twitch fibers
- fast-twtich fibers rely on a well, developed, SHORT-TERM GLYCOLYTIC system for energy transfer
- Fast-twitch fiber activation predominates in ANAEROBIC type Sprint activities and other FORCEFUL muscle actions that rely almost entirely on aerobic energy metabolism
- Activation of fast-twitch fibers plays an important role stop and go or change of pace sports such as basketball, soccer, lacrosse, or field hockey.
36
What are the main subtypes of fast-twitch fibers?
Fast-Twitch fibers (Type II fibers) distribute into two primary subtypes:
- Type IIa: represent the FAST-OXDIATIVE-GLYCOLYTIC fibers
- Type IIb: possess the Greatest ANAEROBIC potential and MOST RAPID Shortening velocity; represents the TRUE FAST-glycolytic fiber
37
Describe the characteristics of Slow-twitch fibers ? where do they generate energy from?
Slow Twitch fibers (Type I )
- generate energy fro ATP resynthesis predominantly through AEROBIC system of energy transfer.
- 4 characteristics:
1. Low myosin ATPase activity
- 2. SLOW calcium handling ability (take up and release) and shortening speed
4. Less well-developed glycolytic capacity than Fast-twitch fibers
5. LARGE and NUMEROUS Mitochondria
38
Explain the kind of exercise slow-twitch fibers are suited for and what kind of system it uses.
Slow-twitch fibers are HIGHLY FATIGUE RESISTANT and ideally suited for Prolonged AEROBIC exercise
-are Slow-Oxidative fibers with SLOW SHORTENING Speed and rely on OXIDATIVE metabolism
39
What kind of exercise are both fast and slow twitch muscle fiber types used?
Both Slow and fast muscle fiber types contribute during NEAR-MAXIMUM Aerobic and Anaerobic exercise
40
compare the type of muscle fiber that predominates in sprint swim athletes vs endurance cyclist
In sprint swim athlete= 80 % of muscle fibers are type II (fast-twitch)
in Endurance cyclist - 80% of muscle fibers are type I (Slow-twitch)
41
explain which muscle fiber type dominates in acidic vs alkaline environments
COME BACK TO THIS
acidic environments: fast twitch (type II) fibers predominate
alkaline (pH of 10.4) - mostly type II fibers
42
Describe the fiber type differences that occur in individuals
Men, women and children on average possess 45-55% slow-twitch fibers in their arm and leg muscles
-The fast-twitch fibers probably distribute equally between type II a and type II b subdivisions
- while NO gender differences exist in fiber distribution, LARGE INTERINDIVIDUAL Variation occurs
-Generally, the trend in one's muscle fiber type distribution remains consistent among the body's major muscle groups.
also muscle fiber type varies based on training
43
Explain the fiber type difference that occur among athletic groups. Which athletes have fast-twitch or slow twitch fibers that predominate? What does successful sport performance depend on?
What is gender difference in muscle structure?
Fiber type differences among athletic groups:
-certain patterns of muscle fiber distribution appear in comparisons among highly proficient athletes
ex: Endurance athletes (cross-country, long distance runners) possess predominantly SLOW-twitch fibers; fast-twitch fibers predominate for ELITE SPRINT athletes
-performance success is dependent not only on muscle fiber composition, but on blending of many physiologic, Biochemical, Neurologic and biomechanical Support systems.
LARGER muscle fibers in male athletes and Larger total muscle mass ar the principle gender differences in muscle morphology
44
What is a motor unit comprised of and how does it function?
Motor unit: made of alpha motor neuron and muscle fibers
The motor neuron will innervate muscle fiber
multiple motor neurons will stimulate muscle.
45
What are the two main parts of human nerves system?
Human Nervous system consists of 2 main parts:
1. Central Nervous system (CNS) consisting of brain and spinal cord
2. Peripheral Nervous system (PNS) consisting of nerves that transmit information to and form CNS.
46
what is composed of the brain in central nervous system? What are the six main areas of the brain?
brain cells, spinal neurons, and neural circuits are created throughout life
- The six main areas of the brain:
1. Medulla oblongata
2. Pons
3. Midbrain
4. Cerebellum
5. Diencephalon
6. Telencephalon
47
What is composed of the Brain stem and how are these parts connected?
The brainstem is composed of Medulla, pons, and midbrain
- The medulla extends into the pons and serves as a bridge between two hemispheres of cerebellum
- the midbrain attaches to the cerebellum and forms a connection between the pons and cerebral hemispheres
48
What is structure and function of cerebellum?
Cerebellum consists 2 peach size mounds of folded tissue with lateral hemispheres and central vermis
-functions as the major comparing, evaluating, and integrating center for postural adjustments, locomotion, maintenance of equilibrium, perception of speed of body movement and other diverse reflex-related movement functions.
49
Explain where the diencephalon is located in the brain and what it comprises of
Diencephalon is located immediately above the midbrain and forms part of cereal hemispheres
-major structures of diencephalon include Thalamus, hypothalamus, epithalamus, and subthalamus
50
Explain what comprises of telencephalon? How much does cerebral cortex make up of brain? Describe the lobes that cortex is divided into and its functions.
Telencephalon contains 2 hemispheres of CEREBRAL CORTEX , including the corpus striatum and medulla
- the cerebral cortex makes up approximately 40% of the total brain weight
- It divides into 4 lobes: frontal, temporal, parietal and occipital
- Neurons in the cortex provide specialized SENSORY and MOTOR functions
51
Describe the structure and function of spinal cord. Also list the three types of neurons it has
Spinal cord is encased and protected by bony vertebral column and attaches to the brainstem
-it provides a major CONDUIT for the two-way transmission of information from skin, joints and muscles to the brain
-provides for COMMUNICATION throughout the body via spinal nerves of the PNS (peripheral Nervous System)
-Contains principally three types of neurons:
-motor neurons
-sensory neurons
-interneruons
-
52
What is the role of the ascending nerve tracts in the spinal cord. Also explain the how neurons form the sensory pathway.
Spinal Cord- Ascending Nerve Tracts
- forward sensory information from peripheral receptors to the brain for processing
- Three neurons form the sensory pathway:
- The AXON of the cell body for first neuron relays information into the spinal cord.
- the CELL BODY of the second neuron lies WITHIN Spinal cord
- The AXON of the third neuron passes up to the CENTRAL COMMAND center in the cerebral cortex.
53
Describe the role of the sensory receptors in spinal cord. Distinguish between the two types of receptors
Sensory receptors serves as SPECIALIZED receptors to detect CONSCIOUS and SUBCONSCIOUS sensory information.
-Conscious receptors show sensitivity to body position, temperature, and sensations of light, sound, smell, taste, touch and pain
- Subconscious receptors show changes in the body's INTERNAL environment
- CHEMORECEPTORS that respond to changes in blood gas tension and pH
- BARORECEPTORS that react rapidly to even small changes in Arterial Blood Pressure
54
What is the role and function of descending nerve tracts in the Spinal cord?
Descending Nerve tracts
- allow axons form the brain to move Downward through the spinal cord along two major pathways:
- PYRAMIDAL TRACT activates the skeletal musculature in Voluntary movement under direct cortical control
- EXTRAPYRAMIDAL TRACT- controls posture and muscle tone via the brain stem.
55
What is role of reticular formation in the Central nervous system?
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Reticular Formation (in central nervous system) provides an extensive and intricate neural network though the core of the brainstem that integrates the spinal cord, cerebral cortex, basal ganglia, and cerebellum
-it receives a continuous flow of sensory data and once activated, it either inhibits or facilitates other neurons.
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56
What does the peripheral nervous system contain and what is the function of these nerves?
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Peripheral Nervous System:
-contains 31 pairs of SPINAL nerves and 12 pairs of CRANIAL nerves
-Cranial nerves contain fibers that transmit sensory and/or motor information
Spinal Nerves include:
- 8 pairs of cervical nerves,
-12 pairs of thoracic nerves
-5 pairs of lumbar nerves
-5 pairs of sacral nerves
and 1 pair of coccygeal nerves
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57
What kind of neurons are present in peripheral nervous system and what is their function? compare and contrast somatic nerves and autonomic nerves
peripheral Nervous system includes:
-AFFERENT neurons that relay SENSORY information from receptors in the periphery towards the CNS
-EFFERENT neurons that transmit information AWAY from brain to peripheral tissues
somatic nerves- innervate SKELETAL muscle and produce an EXCITATORY response to activate muscle
-Autonomic Nerves- produce either and Excitatory or Inhibitory effect and activate cardiac muscle, sweat and salivary glands, some endocrine glands, and smooth muscle cells in intestines and walls of blood vessels
also quick reflexes go through internerouns in spinal cord
58
Describe the functions of Sympathetic and parasympathetic fibers of autonomic nervous system. What parts of the brain control the autonomic nervous system?
The Autonomic nervous system subdivides into:
- Sympathetic fibers that supplies the heart, smooth muscle, sweat glands and viscera
- Parasympathetic fibers leave the brain stem and sacral segments of spinal cord to SUPPLY the thorax, abdomen, and pelvic regions.
- Regions of the MEDULLA, PONS, and DIENCEPHALON control the Autonomic nervous system
59
What does the Reflex Arc consist of and what is its role?
Reflex arc consists of:
- AFFERENT neurons that enter the spinal cord through the dorsal root and transmit sensory input from peripheral recpetors
- these neurons synapse in the cord through INTERNEURONS that RELAY information to different cord levels
- The impulse then passes over the motor root pathway via Anterior Motor neurons to the Effector organ.
60
Decribe the process of nerve supply to muscle? how do Motor neurons contribute and what does a motor unit consist of? what contributes to muscle actions?
One nerve or its terminal branches innervate at least One of the body's approximately 250 million muscle fibers
-The number of muscle fibers per motor neuron generally relates to muscle's particular movement function
-The motor unit consist of ANTERIOR Motor neuron and Specific muscle fibers it innervates
-The individual and combined actions of motor units produce specific muscle actions
-
-
61
explain the relationship between muscle fibers and neurons
each muscle fiber generally receives input form only one neuron, yet a motor neuron may innervate Many muscle fibers
62
What does the Anterior Motor neuron consist of and what are the functions of each one? what is the role of anterior motor neuron?
Anterior Motor Neuron:
-consists of CELL BODY, AXON, and DENDRITES
-Anterior motor neuron allows transmission of an electrochemical impulse from the spinal cord to muscle
-Can only conduct impulses DOWN the axon.
Cell body- HOUSES the neuron's Control center
-Axon extends from the cord to DELIVER the impulse to muscle
Dendrites consists of Short Neural Branches that RECEIVE impulses through numerous connections and Conduct them toward cell body.
63
What is the role of myelin sheath, Schwann cell, neurilemma and Nodes of Ranvier in anterior motor neuron?
Anterior Motor Neuron:
1. Myelin sheath- WRAPS around axon and Encases Larger nerve fibers (insulating , propagate signals)
2. Schwann cells- Cover the bare axon and then Spiral around it (wrap around axon to form myelin sheath)
3. Neurilemma- a thinner outermost membrane, that covers myelin sheath
4. Nodes of Ranvier- Interrupts the Schwann cells and myelin every 1 or 2 mm along Axon's length and allows impulses to "jump" from node to node as the Electrical current travels toward terminal branches.
64
List the main nerve fiber groups and explain how they differ
Four Nerve fiber groups differ on : SIZE and Transmission VELOCITY:
- A alpha
- A- beta
- A- delta
- C- nerve fibers
65
What characteristic of nerve fiber determines speed of neural transmission?
The THICKNESS of a Nerve fiber dictates the SPEED of Neural transmission within the fiber
66
What does all muscle action depend on and elaborate on these sources?
All muscle action ultimately depends on 3 primary Sources of INPUT to Motor units
1. Dorsal root ganglion cells with axons that innervate specialized muscle spindle sensory units embedded within muscle
2. Motor neurons in the brain, primarily in cerebral cortex's pre central gyrus
3. Larges input from EXCITATORY and INHIBITORY Spinal cord interneurons.
-
67
What is the Neuromuscular junction?
Neuromuscular junction. (NMJ):
-represents the interface between the end of a myelinated motor neuron and muscle fiber and transmits the nerve impulse to initiate muscle action
68
Describe the 5 common features of Neuromuscular junction
5 common features of NMJ:
1. presence of Schwann cells
2. terminal section of neuron has Acetylcholine (ACh)
3. Basement membrane that lines synaptic space
4. membrane across synaptic space has ACh receptors
5. Connector microtubules at postsynaptic membrane that transmit the electrical signal deep within muscle fiber.
69
What is a Schwann cell?
Schwann cell- a myelinated neuron that maintains peripheral nervous system
70
Where does excitation normally occur and explain the process.
Excitation normally occurs ONLY at the NMJ
process:
1. When an impulse arrives at the NMJ, ACh (acetylcholine) releases from vesicles in terminal axons into synaptic cleft
2. ACh then combines with a transmitter-receptor complex in the postsynaptic membrane
3. The change in electrical properties elicits an Endplate potential that spreads from the Motor endplate to the Extrajunctional sarcolemma of muscle
3. This causes an Action potential to travel the length of the muscle fiber, enter the T-tubule system and spread to inner structures of the muscle fiber to prime the Contractile machinery for excitation.
71
Compare and contrast EPSP and IPSP. what happens to electrochemical potential?
EPSP (excitatory post-synaptic potential)- describes the change in membrane voltage of post-synaptic cell due to influx of positive charged ions (Na+ ions) into cell. This allows the neuron to more likely fire an Action potential
IPSP (inhibitory post-synaptic potential)- describes changes in membrane voltage due to influx of NEGATIVELY charged ions (Cl-) into post-synaptic cell (this hyperpolarization makes it less likely to form AP)
72
What occurs with neural facilitation?
Neural facilitation, or Disinhibition, affects neurons within the CNS (central Nervous System)
-Enhanced facilitation causes full ACTIVATION of muscles during all-out effort and accounts for rapid and Highly Specific Strength increases in early stages of resistance
73
Describe the factors that produce neuronal facilitation
Factors that produce Neuronal facilitation:
1. DECREASED sensitivity of the motor neuron to inhibitory neurotransmitters
2. REDUCED quantity of INHIBITORY neurotransmitter substance transported to motor neuron
3. Combined effect of both mechanisms
74
What occurs during inhibition and how does this affect the neuronal response? why is inhibition important?
Inhibition:
-Some presynaptic terminals produce INHIBITORY impulses that INCREASE the postsynaptic membrane's permeability to Potassium and Chloride ion Efflux, thus increasing the cell's Resting membrane potential to create an INHIBITORY POSTSYNAPTIC Potential (IPSP)
This makes it more difficult to fire Action potentials
- Neural inhibition has PROTECTIVE functions and REDUCES the input of unwanted stimuli to produce a Smooth, purposeful response.
ex: people with ADHD filter distractions
75
What are the functional characteristics of motor unit? What properties are these motor units classified on?
A motor unit contains only ONE specific muscle fiber type (type I or type II) or a subdivision of the type II fiber with same metabolic profile
- Motor units are classified based on 3 physiologic and mechanical properties of muscle fibers they Innervate:
- Twitch characteristics
- Tension characteristics
- Fatigability
76
What are the major twitch characteristics for motor units? how can fast and slow twitch fibers be comparable?
How do motor neurons affect muscle fibers?
Major twitch characteristics for common motor unit categories:
- Fast twitch, High force and FAST Fatigue (type IIb)
- Fast twitch, Moderate force and Fatigue RESISTANT (Type IIa)
- Slow twitch, Low Force, and Fatigue Resistant (type I)
- with PROLONGED AEROBIC Training, fast-twitch muscle fibers become almost as fatigue resistant as Slow-twitch fibers
- Motor neurons have a STIMULATING effect on the muscle fibers they INNERVATE in a way that modulate the fibers' properties and adaptive response to stimuli.
77
describe characteristics of the motor units
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Fast twitch (type IIa) : High force, Fast fatigue
Fast twitch (type IIb) : Moderate force, fatigue resistant
Slow twitch (type I)- LOW force, Fatigue resistant
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78
Describe the major tension characteristic of motor units and what it comprises of
Tension characteristics:
- ALL or- NONE Principle: A stimulus strong enough to trigger an action potential in motor neuron activates ALL of the accompanying muscle fibers in the motor unit to CONTRACT Synchronously
- A motor unit does NOT exert a Force a gradation: Either the impulse Elicits an action or it Does Not
- After the neuron fires and the impulse reaches the NMJ, ALL fiber and motor unit react simultaneously
79
Explain the principle called Gradation of force and discuss its two main components
Gradation of force:
- The force of muscle action VARIES from Slight to Maximal via 2 mechanisms:
1. INCREASED number of motor units recruited
-a muscle generates a considerable force when activated by ALL of its motor units
ex: human hold its neck up
2. INCREASED Frequency of motor unit discharge
-repetitive stimuli that reach a muscle before it relaxes, increases total tension.
-
80
Describe what happens during motor unit recruitment and also discuss the size principle. what happens when muscle force requirements increase?
Motor unit recruitment describes adding motor units to Increase muscle force
-As muscle force requirements increase, motor neurons are recruited progressively Larger axons, according to size principle.
The size principle- orderly recruitment of specific motor units to produce a smooth muscle action by allowing the CNS to fine tune skeletal muscle activity to meet the demands of the motor task.
81
What factor distinguishes skilled from unskilled performances in exercise and athletic acts ?
The DIFFERENTIAL CONTROL of motor unit Firing patterns represents a major factor that distinguishes skilled from unskilled performances and specific athletic acts.
82
compare and contrast the difference in number of motor units needed for different exercise intensities
For light intensity exercise- mostly use slow twitch fibers (type I) and only require small amount
Moderate intensity- requires a little more than light intensity and includes type Iix, type IIb (fast twitch) and type I (slow); a little bit of all muscle fiber types
Intense exercise- requires a great combination of all fibers fast twitch (IIa, Iix) and slow twitch (type I)
83
What occurs during neuromuscular fatigue? List the main components of voluntary muscle actions
Neuromuscular fatigue- DECLINE in muscle tension or force capacity with repeated stimulation or during a given time period
Voluntary muscle actions exhibit 4 main components:
-Central nervous system
-Peripheral nervous system
-Neuromuscular Junction
-Muscle fiber
84
What happens when muscle function changes during prolonged exercise?
As muscle function changes during prolonged exercise, Additional motor unit recruitment maintains force output necessary to maintain a constant level of performance.
85
Explain what proprioreceptors are including what type of receptors they are and their functions
Proprioreceptors:
- Sensory receptors in the muscles and tendons that are sensitive to Stretch, Tension and Pressure
- they almost INSTANTANEOUSLY relay information about muscular dynamics and limb movement to conscious and subconscious portions of CNS
- Allows continual monitoring of the progress of any sequence movements and serves to modify subsequent motor behavior
86
Describe the role of muscle spindles. Also discuss how muscle spindles vary. Discuss which fibers innervate spindles
Muscle spindles:
provide mechano-sensory information about changes in muscle fiber LENGTH and Tension
-Primarily respond to any stretch of muscle and initiate a STRONGER muscle action to counteract this stretch
-The NUMBER of spindles within a quantity of muscle VARIEs depending on muscle group
-2 Sensory Afferent fibers and One motor Efferent fiber innervate the spindles.
87
Explain how muscle spindles help regulate posture?
Muscle spindle Detects, responds to and Modulates changes in Length of extrafusal muscle fibers to provide an important Regulatory function for Movement and maintenance of posture.
88
Describe which components make up stretch reflex?
Three main components that make up stretch reflex:
- Muscle spindle that responds to stretch
- Afferent nerve fiber that carries sensory impulse form the spindle to spinal cord
- Efferent Spinal cord motor neuron that activates stretched muscle fibers.
89
Where are Golgi tendon organs located and what role do they play?
Golgi Tendon Organs
- connect to extrafusal fibers near tendon's junction to muscle
- They detect differences in Tension generated by active muscle to Protect muscle and surrounding connective tissue harness from injury from Sudden or excessive load
- the organs respond as a feedback monitor to discharge from:
- Tension created in the muscle when it SHORTENS
- Tension when the muscle stretches passively
90
what happens when Golgi receptors are stimulated?
When Stimulated, Golgi receptors transmit signals to Spinal cord to elicit reflex inhibition of the muscles they supply
spinal cord has inhibitory interneurons
91
what are pacinian corpuscles? what role o they play in muscle action?
Pacinian corpuscles:
-small, ellipsoidal bodies located close to the Golgi Tendon organs and embedded in single, unmyelinated nerve fiber
-They respond to QUICK movement and Deep PRESSURE
they act as Fast-adpating Mechanical SENSORS that discharge a few impulses at the onset of a steady stimulus and then remains electrically silent, or they discharge a SECOND volley of impulses when the stimulus ceases
-they also detect changes in movement or pressure
92
Compare and contrast atrophy and hypertrophy in terms of muscle growth
in terms of muscle growth:
Atrophy- occurs when muscle mass decreases and you have a SMALLER muscle fiber (occurs due myonuclear loss, decrease in myofibrillar proteins and myofiber CSA )
Hypertrophy- occurs when muscle fiber becomes BIGGER; you have bigger cross sectional area and , my-nuclear addition; you increase myofibrillar proteins and myofiber CSA)
93
Compare and contrast hypertrophy and hyperplasia
cell hypertrophy- Muscle cell increases in SIZE and becomes bigger
cell hyperplasia- Muscle becomes larger due to increases in NUMBER of cells
94
What is the main role of satellite cells and explain the benefit of micro tears in muscle
Satelite (stem cells) cells facilitate Muscle tear repair.
| Mirco tears in muscle allow for muscle to get bigger and is how tissue remains healthy?
95
Explain the process of how satellite cell responds to injury
process:
1. Muscle injury leads to satellite cell activation and proliferation
2. Satellite cell then migrates to damaged region of muscle fiber
3. Satellites cell fuses to damaged myofiber OR aligns and fuses to produce a NEW myofiber
4. either way, this leads to REGENERATION of myofiber or New myofiber created
96
Differentiate between normal health muscle tissue, tissue after injury and improperly healed tissue and their characteristics
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Healthy Tissue (pre-injury)- have Normal function, and NO pain
Injured tissue- Strained tissue, with Decreased function and Increase in Pain; the muscle can be repaid and can function normally again
Improperly healed tissue- leads to SCAR tissue and Decrease in function and Increase Risk of Re-injury. This can lead to Fibrosis (which is dangerous)
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97
Describe the different types of Muscle tears, and what can lead to them.
Muscle Tears
-Grade 1- redness, inflammed
Grade 2- split a piece of muscle
Grade 3- Complete tear of muscle
Muscle tears are seen in many young adults
they can be seen in those with Lack of nutrition or bone breaks in muscle
98
What are knots or trigger points? explain how it affects muscle tissue
Knots or trigger points are- small, bump like areas in the muscle fiber that can be painful
-This continuously contracted knot in muscle fiber STOPS blood flow at the trigger point, Starving tissue of Oxygen and nutrients. Metabolic waste and toxins build in the area causing pain, tension and spasm in muscle
99
Explain what occurs in Acute knots and chronic knots.
Acute knots- One-time STRESS OVERLOAD of muscles (ex; strenuous sports activity; acute trauma accident- sports injury or bad fall)
-Chronic (long-term)- Myofascial pain syndrome- chronic MISUSE of muscles (ex: postural stress- sitting in incorrect position or lifting improperly overt time)
100
Compare and contrast latent and active trigger points
Latent trigger points- Hurt when you put PRESSURE on them (ex; neck)
Active trigger points: Actively refer pain along your neural pathways- causing it in Non-localized areas
101
Where are the most common sites in the body for knots or Trigger points?
Most common sites for knots or trigger points
- Lower back
- Calves
- Neck
- Shoulder
- Shins
- Illiotibial band
102
Explain what occurs in chronic myofacial pain syndrome and the symptoms that occur.
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Myofacial Pain syndrome- a disorder in which pressure on the sensitive parts in the muscles cause pain in seemingly unrelated body parts
-Chronic Painful condition:
-Scar tissue entraps nerves
-Muscle spasms trigger pain
Inflammation irritates the nerves
-Knots in muscle fibers squeeze nerves
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103
Provide an example of where the syndrome can be seen.
Chronic myofacial pain syndrome:
Trigger point area in Right Trapezius (upper back) associated with a hypersensitive palpable nodule in TAUT band
The pain induced by engaging the affected muscle is underlying cause of limited range of movement and reduced muscle strength.
-Prolonged muscle inactivity can lead to Muscle ATROPHY.
(if muscle spams are not relieved, scar tissue can form and entrap nerves, leading to chronic pain)
104
What are the common causes of trigger points?
Common causes of trigger points:
- poor posture due to sedentary lifestyle
- Injuries from repetitive motions or heavy lifting
- Direct injuries such as blunt force trauma, muscle tears, strain or breaking
- Overwhelming amounts of emotional stress.
105
What are Advanced Therapies for trigger points?
advanced therapies for trigger points:
- Electrostimulation
- Therapeutic stretching techniques
- Physical Therapy
- Therapeutic Massage
- Pulsed Ultrasound
- Low-Level Laser Therapy
- Corticosteroid Injections
106
What is tendonitis? Where in the body can tendonitis be seen?
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Tendonitis- Inflammation and irritation of a tendon
common forms of tendinitis are seen in elbow (arm) and Achilles tendon (foot)
Tennis elbow (epicondylitis humeri)- right arm (peripheral)- condition in which forearm muscles becomes damaged from overuse (repetitive wrist and hand motions) , causing pain
-tractive forces of the muscles acting on the tendon insertions may result in microscopic tears, which then become Inflamed and lead to chronic disorder
also micro cracks caused by tensile forces of the muscles occur
-Achilles tendinitis: an overuse injury of the achilles tendon. This occurs in band of tissue that connects the calf muscle to heel bone (seen in runners); heel pain, stiffness, swelling
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107
what is plantar fasciitis? What body part does this occur in?
Plantar fasciitis- INFLAMMATION of the Fascia
this fascia is a thick ligament that connects your heels to your toes.
Plantât fasciitis can be caused when there is too much pressure on your feet that damages or tears ligaments, causing paining heel.
