FORM AND FUNCTION (Metabolic Demands: Muscle) Flashcards
Key features of the metabolic demands of skeletal muscle:
-adaptability
-rapid ATP production
-fatigue
Adaptability:
-can switch between metabolic pathways based on activity demands
Rapid ATP production:
-skeletal muscle can quickly produce ATP to meet immediate energy needs when switch to intense activities from rest
Fatigue:
-metabolic by-products can lead to muscle fatigue during intense activities
3 main energy pools:
-ATP-Creatine phosphate (immediate)
-glycolytic (fast and short-term)
-oxidative (slow and long-term)
ATP-Creatine phosphate system:
-provides energy for short, high-intensity burst (<10seconds)
-rapid regeneration of ATP from Creatine Phosphate
-Creatine kinase catalyzes the reversible reaction
-Creatinine is by-product of creatine
ATP-Creatine phosphate ‘equation’:
-resting muscle: ATP+creatine=creatine phosphate and ADP
-creatine kinase get=creatine and ATP in active muscle (ATP used for muscle contraction)
Creatinine:
-by-product of creatine
-used as an indicator for kidney function (not functioning properly)
*not directly involved in metabolism but is part of the system
Glycolytic vs. oxidative:
-glycolytic: glycolysis (anaerobic)
-oxidative phosphorylation: TCA cycle and ETC (mitochondria)
Glucose: anaerobic pathway
-get 2 ATPs
-lactate produced can cause muscle fatigue and metabolic acidosis (and death)
Glucose (pyruvate) or FFA (beta oxidation): aerobic pathway
-relies on TCA and the ETC (mitochondria)
-predominantly used in prolonged, low-intensity activities
-requires oxygen
Oxygen for aerobic pathway:
-myoglobin (oxygen-binding protein)
-blood supply
Fiber types:
-type I (slow twitch)
-type IIA (fast twitch, oxidative)
-type IIB (fast twitch, glycolytic)
Fast vs. slow:
-refers to speed of contraction
-related to Vmax (ability of the myosin head)
Type I:
-slow twitch
-aerobic
-high endurance =fatigue resistance
-red (due to heme group in myoglobin)
Type I morphological characteristics:
-high mitochondrial content
-high fat content
-low glycogen content
Type IIA:
-fast twitch
-oxidative
-mix of aerobic and anaerobic
-moderate endurance (fatigue resistant)
Type IIA morphological characteristics:
-intermediate mitochondria
-fat and glycogen content
Type IIB:
-fast-twitch
-glycolytic
-predominantly anaerobic
-low endurance=fatigue sensitive
-white
Type IIB morphological characteristics:
-low mitochondrial and fat content
-high glycogen content
Motor units and fiber type:
-usually only have one fiber type
Force and fatigability of different types of motor units:
-highest: type IIB
-middle/low: type IIA
-low: type I
If continue stimulation: force and fatigability:
-fast twitch (Type IIB): can no longer maintain the force even with continuous stimulation
-Type IIA: maintain force for minutes but not hours
-slow twitch: maintain a 100% force with the continuous stimulation
Percentage of each fiber type:
-varies from muscle to muscle
-varies from species or breeds
Quarter horse vs. Arabian:
-quarter: sprinting, higher Type II fast twitch
-Arabian: endurance, higher Type I slow twitch
Skeletal muscle: adaptation
-sarcomeres increase during growth
-hypertrophy and hyperplasia
Hypertrophy:
-increases actin/myosin in parallel to increase force
*not adding new muscle fibers, but adding sarcomeres in PARALLEL
Hyperplasia:
-rare
-more force is generated form more muscle fibers being made
-requires satellite cells with intact endomysium for successful repair after injury
>satellite cell can make another muscle fiber if endomysium is intact
Type of training:
-learning/coordination
-endurance (submaximal, sustained efforts)
-strength (brief, maximal efforts)
*skeletal muscle show specific adaptations based on type of activity
Learning/coordinated training:
-ex. typing
-increased rate and accuracy of motor skills (CNS)
Endurance training:
-submaximal, sustained efforts
-ex. marathon training
-increased oxidative capacity in all involved motor units with limited cellular hypertrophy
Strength training:
-brief, maximal efforts
-ex. weightlifting
-hypertrophy and enhanced glycolytic capacity (ex. more enzymes) or motor units employed
