Muscle anatomy Flashcards
Why does the size of motor neuron differ from muscle to muscle ?
This is due to the control
Required. E.g in fine control movement , large motor units are not required e.g gastrocnemius and calf. These type of muscle may contain 2,00 0 muscle fibres to generate ballistic contraction like kicking.
What is a motor neuron
A motor neuron consists of the axon , the axon hillock and dendrites that activate the a-motor neuron in the skeletal muscle purves et al 2011 (fig.1) (draw the motor neuron in your head and in exam )
What does a muscle contain ?
Each muscle contains myofibrils that contain myofilaments (actin and myosin) for contraction. Sarrounding fibrils is the t-tubules channels knows as sarcoplasmic reticulum that contain calcium ions
What determines contraction ?
Frequency of stimulation , CSA and length of muscle , and the rate the muscle shorten
What are the 3 fibre types ?
Type 1 - slow oxidative fibres
And fast type 2 fibres (2a and 2b)
What are there characteristics ?
How are fibre types classified ?
Enzyme dehydrogenase , gusto genial staining for myosin heavy chains
What does a contraction form
It forms a sarcomere , that contain myofilaments , h zone , z lines , I bands and a band
What is the process of muscle contraction
AP to neuromuscular junction
Stimulate ACH and trigger AP down axon to a motor neuron
This activate sodium sodium potassium pump as t tubules lead AP to sarcoplasmic reticulum to release calcium ions
So calcium now binds to troponin and uncovers binding site and cause modulation of tropomyosin .
This causes myosin to bind to actin due to power stroke with ATP and this moves z lines together and creating cross bridge cycling of actin an myosin making a contraction.
What are types of force contraction ?
Isometric - produce greatest force
Concentric - max unloading shortening so produces less force but at fastest velocity
Eccentric - the muscle elongates whole under tension due to an opposing force greater than the muscle generates
