Myology Flashcards
All types of muscle tissue share these 4 characteristics:
1) Electrical Excitability
2) Contractility
3) Extensibility
4) Elasticity
Another word for striated muscle
Skeletal muscle
Alternating light and dark bands that are characteristic of this Skeletal muscle
Striations
If a muscle is a pack of spaghetti, these are like individual servings.
Fascicle
If a muscle is a pack of spaghetti, these are like single piece of spaghetti.
Muscle fibres (cells)
the cell (plasma) membrane of the muscle cell
sarcolemma
tiny invaginations tunnel in from the sarcolemma towards the centre of the muscle fibre
transverse tubules
the cytoplasm of the muscle fibres – contains lots of glycogen
sarcoplasm
a protein that binds oxygen that has diffused into the muscle fibre and delivers it to the mitochondria
myoglobin
specialized contractile organelles of the muscle cell
myofibrils
fluid filled tubes and sacs running along and surrounding each myofibril– they store and release calcium into the cell (when it’s needed)
sarcoplasmic reticulum
the functional unit of a myofibril (of contraction)
sarcomeres
makes up the thin filaments of a sarcomere
actin
the thick filaments of a sarcomere
myosin
What gives gives skeletal muscle its striated
appearance?
Thick and thin myofilaments overlapping during contraction.
What do skeletal muscle cells need to generate tension?
Stimulated by a nerve signal from a motor neuron
What is the name for the junction between the axon terminal of a motor neuron and the sarcolemma of muscle cells?
Neuromuscular junction (NMJ)
What is the name for the gap between an axon terminal and a motor neuron?
A synaptic cleft
Which neurotransmitter is released
across the synaptic cleft when the signal reaches the NMJ?
acetylcholine (ACh)
True or false: muscles can create their own action potentials.
False: they must come from the nervous system
When the signal crosses the synaptic cleft it stimulates the _____________
Sarcolemma
The ability to respond to certain stimuli by producing electrical signals is called _____________
Electrical excitability
When an action potential travels down the transverse tubules and stimulates the sarcoplasmic reticulum, it releases ___________
Calcium
What is the effect of the release of calcium within a muscle fibre?
It allows the myosin (of the thick filament) to connect with the actin (of the thin filament)
What is the result of repeated ‘ratcheting’ of the muscle filament?
shortening of the sarcomere, the myofibril, the muscle fibre, the muscle
What causes the thick filaments to stop ratcheting of the thin filaments, resulting in a stoppage of tension generation?
Insufficient calcium
True or false: skeletal muscle fibres consume ATP at the same rate
False: skeletal muscle fibres need to vary the levels at which they consume ATP
Muscle fibres store enough ATP to last for what duration of activity?
Three seconds
______________ is a molecule that stores high amounts of energy in its chemical bonds
Creatine Phosphate (PCr_
How is the energy from PCr released used to reform ATP?
It’s split by an enzyme
Why is PCr is first source of energy used when muscle
contraction begins?
It releases energy very quickly
The breakdown of PCr provides energy for - seconds.
3-15
What does it mean that the process of breaking down PCr into ATP is anaerobic and alactic
no oxygen is needed and no lactic acid is produced
In the context of muscles: when muscle activity continues and PCr is depleted, ___________ is used to make ATP
Glucose
Where do cells store the glucose used to make ATP?
glycogen stored in their cytoplasm/sarcoplasm or glucose from the blood
the process of making ATP from glucose occurs in the cell cytoplasm and is called __________
glycosis
through glycolysis, a molecule of glucose is broken into _ molecules of pyruvic acid and -
ATP
2 molecules of pyruvic acid
2-3 ATP
normally, pyruvic acid enters the mitochondria where it undergoes and series of reactions
(that require oxygen) called ________________
Aerobic cellular respiration
n the absence of oxygen, as during heavy excercise/demand, pyruvic acid does not go into the mitochondria – it is converted into ___________
lactic acid/lactate
What happens to the lactic acid when glucose is broken down into ATP?
It diffuses out of the cell into the blood
Anaerobic glycolysis supplies energy for how long?
30-40 seconds
How is lactic acid converted back into to glucose/glycogen in the liver?
Via the Cori cycle
How does the body stop lactic acid from accumulating?
It is consumed by other muscle fibres, less
active nearby muscles, and the heart
Lactic acid has a 1⁄2 life of _________.
15-25 minutes (usually cleared in a matter of hours)
When is Aerobic Cellular Respiration the body’s active pathway for ATP regeneration?
When the body is able to get oxygen in to the cells (e.g. at rest or at low-moderate intensity exercise)
How is oxygen delivered to the cells during Aerobic Cellular Respiration?
By myoglobin or from oxygen diffusing from the blood
How is ATP produced during Aerobic Cellular Respiration?
Pyruvic acid enters the mitochondria and in a series of reactions that require oxygen are able to occur
Which three energy substrates can be used to make ATP during Aerobic Cellular Respiration, and rank them from most to least effective in ATP production.
- Fats
- Carbohydrates
- Proteins
What are three main differences found in skeletal muscle fibres?
▪ the speed at which they generate tension
▪ how they use different energy substrates
▪ how they fatigue
This type of muscle fibre is also called slow-twitch fibres or type 1 because they’re recruited first
Slow Oxidative (SO) Fibres
What makes Slow Oxidative (SO) Fibres so fatigue resistant and used in endurance-type functions (e.g. maintaining posture, running a marathon)?
They have lots of mitochondria, myoglobin, capillaries, and they generate ATP via aerobic cellular respiration (i.e. oxygen is available)
True or false, SO fibres are also resistant to atrophy with immobilization.
False, with immobilization, they atrophy faster (than type II fibres)
This type of muscle fibre is also called type IIa because they’re recruited second
Fast Oxidative-Glycolytic (FOG) Fibres
What makes Fast Oxidative-Glycolytic (FOG) Fibres slightly less fatigue resistant and used in endurance (e.g. walking) and shorter-duration functions (e.g. sprinting)?
They have intermediate amounts of mitochondria, myoglobin, capillaries, and generate ATP via aerobic and anaerobic energy pathways
This type of muscle fibre is also called type IIx and is recruited third
Fast Glycolytic (FG) Fibres
Which type of muscle fibre is used in high intensity, short duration activities (e.g. weight lifting, slap shot) and shorter-duration functions (e.g. sprinting)?
Fast Glycolytic (FG) Fibres
True or false: within a motor unit, there is usually a mix of are a mix of SO, FOG, FG fibres
False: although most muscles are a mix of SO, FOG, FG fibres, within a given motor unit, all fibre types are the same type.
Since precise movements require small changes in muscle contraction, muscles that perform fine movements will be made up of ______ motor units.
small motor units (few m. fibres/motor unit)
:arge (imprecise) movements don’t require small changes in muscle contraction – they typically
require large amounts of tension. Therefore, muscles that perform gross movements will be made up of __________
large motor units (many m. fibres/motor unit)
What are two ways for a muscle to increase the amount of force generated?
1) increase the number of motor units recruited
2) increase the frequency of neuronal AP firing (wave summation)
the forcefulness of contraction (the ability to generate force) depends on the _____________ within a muscle before the contraction begins
length of the sarcomeres
Between optimal overlap, minimal overlap, and excessive overlap, which has the best ability to generate tension?
Optimal overlap (resting length)
muscle contraction through a range against a resistance that is not changing is called ___________
isotonic
a shortening contraction is called ____________
concentric
a lengthening contraction is called __________
eccentric
a muscle contraction in which the length of the muscle does not visibly change
isometric
muscle contraction through a range in which the equipment varies the resistance to match the strength curve
variable resistance
muscle contraction through a range in which the equipment keeps the velocity of movement constant
isokinetic
a small amount of tension being generated in the muscle
not strong enough to produce movement
muscle resting tone
a brief contraction of all the muscle fibres in a motor unit in response to a single AP in its motor neuron
twitch contraction
a lack of tone from the nerve being damaged or cut
flacidity
increase in muscle size
hypertrophy
decrease in muscle size
atrophy
the inability of a muscle to function at the required level due to energy substrate depletion, metabolic by-products, neurological fatigue, or central nervous system fatigue
fatigue
CT that surrounds the entire muscle
epimysium
CT that surrounds the fascicles
perimysium
CT that surrounds the muscle fibres
endomysium
Place where the epimysium, perimysium, and endomysium extend beyond the muscle fibres to connect the muscle to the periosteum
tendon
the transition from muscle tissue to tendon
musculotendinous junction
the transition from tendon to periosteum
tendoperiosteal junction
a broad, flat, tendon
aponeurosis
a tube that surrounds a tendon to protect it
tendon sheath
undifferentiated muscle cells actively involved in muscle repair and regeneration
satellite cells
specialized cells within the heart that can generate their own electrical signals (they act as a pacemaker)
Autorhythmicity
What type of muscle does this describe: found in the walls of hollow tubes, spindle shaped, have gap junctions, involuntary, contractions start slowly and last longer
smooth muscle
capacity for skeletal strength progressively decreases after approximately age ____
25
a greater proportion is lost after approximately age ___
50
