Physiology: Muscles Flashcards
1
Q
What are the 3 Muscle Metabolism Types?
A
- Direct Phosphorylation
- Aerobic Respiration
- Anaerobic Glycolysis
2
Q
Explain Aerobic Respiration (include precursors, location, activity type etc)
A
- Predominate during
- Moderate Activity
- Precursors: Glucose, O2
- occurs in Mitochondria
- requires continuous O2, thus much slower than direct phosphorylation and Anaerobic Glycolysis (most commonly used in slow-twitch muscles)
- Glucose -> CO2 and H20
- high energy released
- via mobilization of acetyl-coA step followed by TCA cycle (citric acid cycle/Krebs Cycle) followed by electron transport and oxidative phosphorylation step
- Fatty acids and amino acids can also be used to generate energy
- Glucose and fatty acids are catabolized
- ATP produced used to power contraction
- Most common in Slow twitch (Slower muscles)
3
Q
Explain Direct Phosphorylation (include precursors, location, activity type etc)
A
- immediate reaction but short-lived
- lasts 20 seconds
- CP depletion
- dependent on Creatine Phosphate (CP)
- high energy molecule
- contained in muscles
- ATP stores
- after ATP depleted, CP transfers energy to ADP to regenerate ATP
- No O2 used
- Resting Muscle
- Fatty Acids are catabolized
- ATP produced used to build energy reserves of ATP, CP and glycogen
4
Q
Explain Anaerobic Glycolysis (include precursors, location, activity type)
A
- Peak activity (High Intensity)
- most ATP produced via glycolysis
- Lactic Acid (LA) byproduct
- only 1/3 of ATP consumption from Mitochondrial Activity
- most ATP produced via glycolysis
- fast process
- replenishes ATP within short time period
- not efficient ATP producer
- breaks down glucose without O2
- Glc->pyruvic acid
- produces minimal ATP
- pyruvic acid->lactic acid
- requires larger amount of glucose
- Causes Muscle Fatigue and prevents muscle contraction
- due to O2 debt and LA accumulation
5
Q
Explain Rigor Mortis
A
- No aerobic respiration
- circulation system stopped
- limited pool of ATP
- generated from Phosphagen and Anaerobic Metabolism (around after death)
- Muscle Contraction caused by
- Ca2+ leaking from extracell fluid and SR into muscle fiber
- lack of ATP prevents relaxation
- myosin head cannot detach from actin
- All M. of body remain contracted
- body becomes rigid
- eventually after days, degeneration of body
- muscle breaks down and appears to relax again
6
Q
Describe Isotonic Contractions
A
- contractions generate force by changing the length of the M. and can be concentric or eccentric contractions
- Myofilaments are able to slide past each other during contractions
- Muscle Shortens
7
Q
Describe Isometric Contraction
A
- generate force without changing the length of the m.
- Tension in Muscle increases
- Muscle unable to shorten
8
Q
What is Muscle Tone
A
- total tension maintained in muscular structure under relaxed condition
- some fibers are contracted even in a relaxed muscle
- different fibers contract at different times to providemuscle tone
- muscle tone stabilizes bones and joints
9
Q
breakdown of muscle tissue causes
A
non-movement, physical tearing, diseases
10
Q
- higher Mitochondrial Content
- rely more heavily on O2 and aerobic metabolism
- oxidative enzymes and mitochondria
A
Slow Twitch Muscle Fibers
11
Q
- rely more on glucose stores than O2
- most ATP derived from glycolosis
- recruited as intensity of activity increases/ reaches peak
A
Fast Fatigable Fibers
12
Q
Describe Muscle Hypertrophy
A
- muscle regeneration and rebuilt of existing muscle cells
- Net Result: muscle protein syth exceeds degradation leading to increased muscle mass
- mainly a result of muscle fibers increasing in size not in quantity
- strength gained from adding more myosin/actin chains per M. fiber
- increase number of cross-bridges -> more force
13
Q
Describe Muscle Atrophy
A
- breakdown of muscle tissue
- Net Result: muscle protein degradation exceeds synthesis leading to degeneration
- use it or lose it (caused by disuse)
14
Q
Describe a “motor unit”
A
- 1 motor neuron and 1+ muscle fibers innervated by same motor neuron
- each motor neuron innervates different group of skeletal m. fibers.
- each motor unit separate from others
- some MU are small
- ex: motor neuron innervates only small # of M. fibers 1 motor neuron -> 3 M. fibers
15
Q
Describe Innervation Ratio (IR)
A
- number of M fibers innervated by a single MU
- small motor unit = small IR
- produces less force than large motor units
- mostly because of number of fibers innervated
16
Q
Describe “Recruitment” in Muscles
A
- Force is Additive
- start with the smaller motor units and then turn on larger motor units to produce more force
- Recruit Slow-twitch (small oxidative) -> Fast-twitch fatigue- resistent -> Fast-twitch fatigable fibers
- as increase need for greater force (increase activity level)
- recruiting more fast-twitch m. fibers:
- oxidative capacity of those muscles decreases as increase speed of activity
- need stronger contractions: so use non-oxidative pathways
- oxidative capacity of those muscles decreases as increase speed of activity
18
Q
Describe Temporal Summation
A
- as increase number of motor units in muscle -> add forces together
- stimulate muscle at higher frequency and does’t allow the force to decay
19
Q
Describe Slow-Twitch Muscles
A
- small cell body and smaller axon diameter
- lower conduction velocity axon
- lower innervation ratio
- recruited early
- long twitch contraction time
- low twitch contraction force
- low tetanic contraction force
- high fatigue resistance
- high oxidative capacity
- high mitochondrial content
20
Q
Describe the length of the sarcomere when a muscle obtains the max force
A
Optimal Length
- maximum overlap between myosin and actin = max cross bridge formation and max force produced
- overly shortened = less cross bridge formation
- overly stretched = less cross bridge formation
24
Q
muscle fibers innervated by single neuron spread out within a muscle
A
