Muscle mechanics Flashcards
length-tension relationship
isometric muscle contraction - tension develops at initial length before contraction
initial length-tension relationship curve made by varying muscle length at rest and measure isometric tension when muscle is maximally stimulated at that length
tension depends on muscle length before it is contracted
optimal length
length at which tension development is maximal
skeletal muscle is usually near optimal
what bacteria causes infection tetanus
clostridium tetani
tetanus
uncontrollable spasms of skeletal muscles
how does bacteria cause muscle spasm in tetanus
toxin blocks inhibitory synapses in CNS - increased activity in motor nerves
opisthotonus
a state of severe hyperextension and spasticity in which an individual’s head, neck and spinal column enter into a complete “bridging” or “arching” position
tetanus in relation to action potential
muscle fibre stimulated so rapidly it cannot relax between stimuli - maximal sustained contraction
summation
stimulation closer together do not allow muscle to relax fully
twitches time length
The muscle cell twitch can have a duration of a
few hundred milliseconds and is never refractory
can be activated to contract many times before can relax
summation with tetanus
at high frequencies of activation, there is a build up of tension which, when it reaches a maximum level of tension is called complete tetanus
staircase phenomenom
When a muscle is stimulated repetitively at a frequency below that which causes summation, there is a progressive increase in the tension developed with each twitch until a maximum twitch is reached
classification of muscle by appearance
striated and unstriated
striated muscle
skeletal
cardiac
unstriated muscle
smooth muscle
classification of muscle by innervation
voluntary and involuntary
voluntary muscle
skeletal muscle
involuntary muscle
cardiac muscle
smooth muscle
morphology of skeletal muscle
long cylindrical
morphology of cardiac muscle
branched
morphology of smooth muscle
spindle or fusiform
nuclei of skeletal muscle
multiple located peripherally
nuclei of cardiac muscle
one or 2 located centrally
nuclei of smooth muscle
one located centrally
what muscle has no t tubules
smooth muscle
t tubules of skeletal muscle form
triad with sarcoplasmic reticulum
t tubules of cardiac muscle form
dyad with sarcoplasmic reticulum
which muscles doesn’t have electrical coupling of cells
skeletal muscle
electrical coupling of cells of cardiac muscle
yes - with intercalated disks contain gap junction
electrical coupling of cells of smooth muscle
yes - gap junction
what is skeletal muscle regenerated with
satellite cells
what muscle cannot regeneration
cardiac muscle
what muscle requires Ca2+ for contraction
smooth muscle
what regulates crossbridge formation for contraction
cardiac muscle
skeletal muscle
Ca2+ binding to troponin
what nerves or receptors control contraction of skeletal muscle
motor neurons
what nerves or receptors control contraction of cardiac muscle
autonomic nerves
beta adrenergic agonists
what nerves or receptors control contraction of smooth muscle
autonomic nerves
hormones
2 types of smooth muscle
multiunit
visceral
examples of visceral smooth muscle
- Intestine
- Uterus
- Bladder
- Ureters
- Ducts of exocrine glands
- Precapillary sphincters
- Small blood vessels
examples of multiunit smooth muscle
- Cilliary muscle
- Iris
- Piloerector muscles
- Large arteries and veins
- Arteriovenous shunt vessels
- Bronchial smooth muscle
what regulates contraction of smooth muscle
Ca 2+ -calmodulin activation of myosin kinase and
phosphorylation of myosin
what muscle does NOT cause summation of twitches by increased stimulus frequency
cardiac muscle
