Flashcards in Muscle Morphology and Mechanics Deck (21):
What shape is the pectoralis major?
What shape is the deltoid?
What shape is the biceps brachii?
Describe fasciculation and a disease where it becomes pathological.
Muscle twitching. Normal to have it slightly.
Pathological when excessive e.g. motor neuron disease
Describe isotonic muscle contraction
Equal force, muscle changes in length to move the load.
Can be concentric: muscle shortens, e.g. to lift the load in the hand.
Or eccentric: muscle exerts force while being extended e.g. walking downhill. Linked to delayed onset muscle soreness.
Describe isomeric muscle contraction
Constant length, variable extention.
e.g. hand grip
Has a profound effect on blood pressure
Describe the difference between slow and fast twitch muscle fibres.
Slow - many mitochondria so not fatigueable
Fast - fewer mitochondria
What is proprioception? Give a drug that can interfere with it.
Feedback control of movement, awareness of self.
Muscle spindles tell the brain about force and stretch. They are specialised muscle fibres with associated nerve endings, enclosed in a capsule.
Alcohol interferes with it.
What is one motor unit?
A muscle fibre and the fibre it innervates. Signal molecules.
Give an example of signal molecules used between the nerve end and muscle which is not a neurotransmitter.
Neurotropins e.g. neurotropin 3
Cytokines e.g. cardiotrophin-1
Insulin-like growth factor e.g. ILGF-1
Where in the brain are motor control centres for the muscles found?
Describe hypotonia and give a disease which can cause it.
Loss of muscle tone.
Cerebral/spinal neural shock
Lesions of the cerebellum
Motor nerve lesions: polyneuritis
Primary degeneration of muscles: myopathy
Describe excitation-contraction coupling
Action potential travels down t-tubules, activating the sarcoplasmic reticulum to release calcium ions.
Describe spatial summation
More motor neurons are activated so more muscle fibres are recruited to develop an increased force.
Reflex pathway from muscle spindles, joint receptors and golgi tendon organs. Have a role in recruitment.
Describe temporal summation
Contraction depends on the frequency of stimuli.
What is electromyography used for?
In diagnosis of diseases disrupting muscle contraction, such as motor neuron disease.
Electrodes are places above or in the muscle to see if contraction and electrical signals match.
What happens to calcium in muscle cells after contraction?
Most is pumped back into the sarcoplasmic reticulum, some binds calmodulin.
State sources of energy for ATP that allows myosin head detachment from actin.
Stores, creatine phosphate, glycolysis, oxidative phosphorylation
What causes muscle cramp?
Lactate build up
What is peripheral fatigue?
A depletion of muscle glycogen which occurs within one minute if there is interrupted blood flow.