6 Myology Flashcards
What’s a general description of muscle tissue, what 3 types of mm tissue are there and what are their general functions?
- specialized cells that use ATP in the generation of force
- 3 types: skeletal, smooth, cardiac
- functions include: body movement, substance movement, control of substance movement, thermogenesis
What are common characteristics of all mm tissue types?
- electrical excitability
- contractility
- extensibility
- esasticity
What’s the hierarchy of skeletal mm organization? i.e. its structures from macro to micro
Muscle
♦
Fascicle
♦
Muscle Fibre (Muscle Cell - [multinucleat)
♦
Myofibril (organelles within mm fibre that help contribute to contractility) (made up of segments called sarcomeres)
♦
Sarcomere
♦
Actin & Myosin protein fibres
What scale of measurement would be used to measure diameter of mm fascicles? (e.g. meter, cm, mm…)
mm
What are mm fascicles made up of?
mm fibres
This is the cell (plasma) membrane of the mm cell:
sarcolemma
What scale of measurement would be used to measure diameter of mm fascicles? (e.g. meter, cm, mm…)
micrometers (millionth) x 100
Tiny invaginations tunnel in from the sarcolemma towards the centre of the mm fibre (allow AP to travel deeper into mm). These are called:
transverse tubules
The cytoplasm of mm fibres (lots of glycogen) is called:
sarcoplasm
A protein that binds oxygen that has diffused into the mm fibre and delivers it to the mitochondria:
myoglobin
Can you increase number of mm cells or myofibrils in the body?
- mm cells: can’t increase number
- myofibriles: can incrase with exercise
What’s a general description of myofibrils?
- specialized contractile organelles of the mm cell
- they extend the length of the mm fibre
- they are held in place by cytoskeletal proteins
- sarcoplasmic reticiulum: fluid filled tubes and sacs running along and surrounding each myofibril – they store and release calcium into the cell (when it’s needed)
- contain a number of sarcomeres arranged in series (end to end)
pp108-9
What’s a general description of the sarcomere?
- the funcitonal unit of a myobiril (of contraction)
- contain 2 contractile proteins: actin and myosin (these show as striations)
- actin: makes up the thin filaments
- myosin: makes up the thick filaments (these pull actin closer together, resulting in contraction)
- thick and thin filaments overlap and their interaction is what generates force/contraction
- their overlap also creases light and dark stripes which gives skeletal mm its striated appearance
The nerve cell that stimulates muscles to contract is called a:
motor neuron
Each motor neuron axon terminal forms a junction called the ___ junction with the ___ of a number of different muscle cells
neuromuscular; sarcolemma
The motor neuron’s axon terminal and the sarcolemma never actually touch – there is a gap between them called the __ __
Synaptic cleft
When the signal arrives at the end of the motor neurons axons, It releases and neurotransmitter called ___ which crosses the ___ ___, stimulates the ___ and the muscle continues the signal
acetylcholine (ACh); synaptic cleft; sarcolemma
Is skeletal muscle activated by chemical potential, electrical potential, or both?
Always chemical; always ACh
The functional unit of a myofibril (of contraction) is the:
sarcomere
The Sarcomere contains two contractile proteins called:
actin and myosin
There are thin and thick filaments in the sarcomere. What are each called?
thin filaments: actin (remember Tiina’s “actinee”)
thick filaments: myosin
A nere cell that stimulates muscles to contract is called a:
motor neuron
The sliding filament mechanism:
- once the signal reaches the mm fibres, it crosses the ___ ___
- the signal is then continued by the mm fibres and spreads out across the ___
- it then travels down the ___ ___ and stimulates the ___ ___ to release calcium
…
- synaptic cleft
- sarcolemma
- transverse tubules; sarcoplasmic reticulum
The sliding filament mechanism:
…
when the signal reaches the sarcomere:
- the calcium allows the ___ (of the thick filament) to connect with the ___ (of the thin filament)
- the ___ pulls (‘slides’) the ___/thin filaments together
- it disengages and starts the cycle again
- this ‘ratcheting’ of the filaments uses ___
- with repitition, it shortens the ___, the myofibril, the muscle fibre, the muscle
…
- myosin; actin
- myosin; actin
- ATP
- sarcomere
The sliding filament mechanism:
…
when the APs stop:
- the sarcoplasmic reticulum pumps ___ back inside (this uses ATP)
- without sufficient ___, the thick filaments cannot continue their ratcheting of the thin filaments
- tension generation stops
- calcium
- calcium
Muscles fibres store enough ATP to last for ~_ seconds
3
What are the three ‘energy pathways’ through which ATP can be generated after its reserves in the muscle have been depleted?
- from creatine phosphate (aka phosphocreatine, ATP-PCr, anaerobic alactic)
- anaerobic glycolysis (aka anaerobic glycolysis)
- aerobic cellular respiration (aka anaerobic lactic)
Read pp 118-119 in notes for more info
The process of making ATP from glucose occurs in the cell cytoplasm and is called ___. Through this process, a molecule of glucose is broken into 2 molecules of ___ ___ and 2-3 ATP.
glycolysis; pyruvic acid
For how long is 1. Creatine Phosphate 2. Anaerobic Glycolysis 3. Aerobic Cellular Repiration capable of supplying energy?
- Creatine Phosphate: 3-15 seconds
- Anaerobic Glycolysis: for 30-40 seconds
- Aerobic Cellular Respiration: continuously when at rest; in activities that last longer than 10 minutes, most (90%) of the ATP generated comes from the aerobic system
What are the 3 main types of skeletal muscle fibres, and in which order are they recruited?
- slow oxidative (aka type I, SO)
- fast oxidative-glycolytic (aka type IIa, FOG)
- fast glycolytic (aka type IIx, FG)
note: these are the reasonably current nomenclatures, but might be called different things in different sources
NB: most muscles are a mix of SO, FOG, FG fibres. Within a given motor unit, all fibre types are the same.
Describe Slow Oxidative (SO) Fibres:
- aka type I, slow-twitch fibres
- recruited 1st (i.e. before type II fibres)
- fatigue resistant
- used inendurance-type functions (e.g. maintaining posture, running a marathon)
- lots of mitochondria, myoglobin, capillaries
- generate ATP via aerobic cellular respiration (i.e. oxygen is available)
- with immobilization, they atrophy faster (than type II fibres)
Describe Fast Oxidatie-Glycolytic (FOG) Fibres:
- aka type IIa fibres
- recruited 2nd
- moderately high resistance to fatigue
- used in endurance (e.g. walking) and shorter-duration functions (e.g. sprinting)
intermediate amount of mitochondria, myoglobin, capillaries - generate ATP via aerobic and anaerobic energy pathways
Describe Fast Glycolytic (FG) Fibres:
- aka type IIx fibres
- recruited 3rd
- low resistance to fatigue
- used in high intensity, short duration activities (e.g. weight lifting, slap shot) and shorter-duration functions (e.g. sprinting)
- relatively low amounts of mitochondria, myoglobin, capillaries
- generate ATP via anaerobic energy pathways (i.e. glycolysis)
What’s the translation for:
- iso
- tonic
- metric
- kinetic
- iso: equal
- tonic: resistance
- metric: measure
- kinetic: movement
What’s isotonic contraction?
mm contraction through a range against a resistance that is not changing
What’s concentric contraction?
a shortening contraction
What’s eccentric contraction?
A lengthening contraction
What’s isometric contraction?
Muscle contraction which the length of the muscle does not visibly change
What’s variable resistance (re: contraction)?
Muscle contractions through a range in which equipment varies the resistance to match the strength curve
What’s isokinetic (re: contraction)?
Muscle contraction through a range in which the equipment keeps the velocity of movement constant
What’s muscle hypertrophy and atrophy?
increase/decrease in muscle size
What are the connective tissue components of muscle?
- epimysium: surrounds the entire muscle
- perimysium: take surrounds the fascicles
- endomysium: surrounds the muscle fibers
What connective tissue components are present in:
- skeletal muscle
- cardiac muscle
- smooth muscle
- skeletal muscle: endomysium, perimysium and epimysium
- cardiac muscle: endomysium and perimysium
- smooth muscle: endomysium
In which types of muscles tissues are contractile proteins organized into sarcomeres?
- skeletal and cardiac: organized into sarcomeres
- smooth muscle: not organized into sarcomeres (also don’t have transverse tubules)
