muscle function Flashcards
explain muscle metabolism on terms of creatine phosphate
Creatine phosphate is Rapid changes from very low ATP consumption to high levels of consumption can happen very quickly
Creatine phosphate= a rapidly metabolite in skeletal muscle and brain (high energy store)
Fast & good for ~ 15 sec (so not very long lasting source of energy, but is fast responding)
explain glycolysis in terms of for producing energy for muscle function
Break down 1 molecule of glucose to 2 pyruvates yielding 2 ATP molecules
If insufficient mitochondria or oxygen, pyruvate => lactic acid
Get about 30-40 seconds more at max of energy than from phosphocreatine.
This is not the greatest source of ATP, as for every glucose, 2 ATP produced
which metabolic process provides the greatest ATP abundance
Aerobic Cellular Respiration
explain aerobic cellular respiration in terms of for producing energy for muscle function
Provides greatest abundance of ATP.
This is often called krebs cycle/ citric acid cycle
Production of ATP occurs in mitochondria
Requires oxygen and carbon substrate
Produces CO2 and H2O and heat byproducts.
what is muscle fatigue
Inability to contract forcefully after prolonged activity due to being worked continually
name some factors that can limit muscle contraction such as in muscle fatigue
Ca2+
Creatine Phosphate
Oxygen
Build up of acid
Neuronal failure
explain oxygen use after exercise
Lactic acid converted back to glucose in liver from the muscle, this will be used to once again synthesize glucose
Liver stores glucose for transport to other tissues
Creatine Phosphate and ATP can be resynthesized, and used in tissues to drive contraction and other processes
Oxygen binds to deoxymyoglobin to form myoglobin again to correct some of those deficiencies after long periods of prolonged exercise have depleted the muscle of its oxygen
Diff types of muscle contraction occur depending on what
on the strength of the stimulus that it receives
name the 4 types of muscle contraction
Single Action Potential (AP)
wave summation
unfused tetanus
fused tetanus
(weakest to strongest force of contraction)
describe single Action Potential (AP)
creates a twitch
Contraction that’s Smaller than maximum muscle force
what does Total tension of fibre depend on
on frequency of APs (number/second)(no large or small, but frequ which they receive will dictate the force of contraction that occurs)
- Requires wave summation
- Maximum = tetanus (muscle cannot contact anymore)
what does Total tension of muscle depend on
on number of fibres contracting simultaneously
Increasing numbers = Motor unit recruitment (the more motor units you have, the greater the contraction will be)
what are the 3 parts to a force of contraction
latent period (flat part before the increase in force)
contraction period (increasing part in force)
relaxation period (when force starts to decrease)
name the 3 fibre types
slow oxidative (SO)
fast oxidative - glycolytic (FOG)
fast glycolytic fibres (FG)
explain Slow oxidative (SO) fibres
small diameter & red
large amounts of myoglobin and mitochondria
ATP production is primarily oxidative
Fatigue resistant as effective at carrying oxygen and ATP production
explain Fast oxidative- glycolytic (FOG) fibres
Large diameter = so many myofibrils
Many mitochondria and high glycolytic capacity (so glycolysis will be high in these fibres)
Intermediate level
explain Fast glycolytic fibres (FG)
white, fastest & powerful and fast fatiguing
Used For strong burst of energy, but short term use
describe recruitment in terms of fibres
Muscle contractions only use the fibres for the work required.
explain the order of fibre recruitmnet
- Slow oxidative
- Fast oxidative – glycolytic
- Fast glycolytic
name the 2 types of contraction
isotonic
isometric
explain isotonic contractions
If force is constant and the muscle shortens = Isotonic Contraction (associated with lifting arm or leg)
explain isometric contractions
If length is constant and the force varies = Isometric Contraction
The latter is often a postural muscle activity
in exercise how is the SO/FG fibre ratio determined
genetically
explain high FG fibres in exercise
sprinters (as need strong short burst of energy)
explain high SO fibres in exercise
marathon runners (gradual energy release over long period due to their good oxygen supply)
what fibres are involved in endurance exercise
exercise gives FG => FOG (fast oxidative – glycolytic) (uses both methods combined)
Increased diameter and numbers of mitochondria
what does strength exercise do to FG fibres
increases size & strength of FG fibers
explain cardiac muscle appearance and contraction
Striated, short fibres that are branched
Single central nucleus; Cells joined by gap junctions & desmosomes
Thickened joint area called intercalated discs
Some cardiac muscles generate own action potential- autorhythmicity
Involuntary
No nerve input required - internal pacemaker that can be modified by the autonomic nervous system.
Ca2+- from S.R. and extracellular space, this means that contractions are more prolonged.
separate cells with gap junctions -> electrical connections
describe smooth muscle
Involuntary
Found in internal organs
Filaments not regular so not striated
name the 2 types of smooth muscle
Visceral (single unit) type
Multi-unit type
explain the Visceral (single unit) type of smooth muscle
Form sheets and are autorhythmic e.g walls of viscera
Contract as a unit
explain the Multi-unit type of smooth muscle
Functions independentaly
each has own nerve and can contract independently e.g. arrector pilii of hair
describe the contractions and response of smooth muscle
Graded contractions and slow responses
describe the tone that smooth muscle sustains
long term tone
what are smooth muscle contractions often triggered by
autonomic nerves
what are smooth muscle contractions modulated by
by hormones, local chemical factors , nerves, by mechanical events (stretching) which can all trigger a response to that
briefly compare smooth muscle appearance to cardia and skeletal muscle appearance
Smooth muscle fibre has a very Diff appearance from cardiac and skeletal muscle as not straited and its arrangement is very irregular
explain the effect of ageing on skeletal muscle mass
There is a slow progressive loss of skeletal muscle mass (atrophy) after the age of 30
- Sarcopenia
explain the effect of ageing on the number of slow oxidative (SO) fibres
Relative number of slow oxidative fibres tends to increase, so less ability to carry out fast type
what can slow down the changes occurring from ageing on muscle
Endurance and strength training
