PHYS20008 Lecture Notes - Lecture 12: Esophagus, Alpha Motor Neuron, T-Tubule
10 May 2018
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Lecture 12
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- Diaphragm → subtle skeletal muscles, absolute control over these muscles
- Involuntary muscles are usually under control of autonomic nervous system,
sometimes under themselves
- Skeletal muscles: control outside environment
- Autonomic nervous system: control inside environment, controls cardiac and smooth
muscle, automatic functioning and regulation of internal environment
- Striated muscle: cardiac and skeletal muscles; looks stripey (because of way
sarcomeres line up, thick and thin filaments present themselves in slightly different
colours and are all organised in parallel); similarities between cardiac and skeletal
muscles (in terms of structure, crossbridge cycles, similar thick and thin filaments in
those muscle types, overlap the same way)
- Smooth muscle is unstriated → because myosin and actin filaments goes in all sorts
of different directions, no stripey appearance
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find more resources at oneclass.com
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- Two different types of cardiac muscles: cardiac contractile cells (main type, in walls
of ventricles and atria); nodal cells (autorhythmic, pacemaker cells; muscle fibres but
contraction isn’t important, spontaneously depolarise rhythmically, keep contracting
outside body spontaneously, generate heartbeat, cells in body communicate with
nodal cells in order to regulate heartbeat)
find more resources at oneclass.com
find more resources at oneclass.com
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- Cardiac contractile cells (myocytes) → ventricular myocytes (on the walls of heart,
myocardial cells), start AP in pacemaker ⇒ spreads across heart from cell to cell,
spread between cells, spreads through one cell then across intercalated disks into
next cell, AP flows across all the cells in the heart as a conjoined unit (want heart to
squeeze altogether as a unit, all cells contracting as a team, AP starts from bottoms
and works upwards; if individual neurons in individual cells ⇒ can’t coordinate well,
different cells contracting at different times; intercalated disks enables AP to spread
from cell to cell ⇒ so they all contract together)
- Skeletal muscle cells have alpha motor neurons that comes in and activates that
individual muscle fibre, AP spread by individual nerves going into cell
- Calcium ions, which are more concentrated in the ECF, would have a positive
equlibrium potential (cell has negative RMP, open calcium channels → calcium
moves into cell, make it more positive)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Diaphragm subtle skeletal muscles, absolute control over these muscles. Involuntary muscles are usually under control of autonomic nervous system, sometimes under themselves. Autonomic nervous system: control inside environment, controls cardiac and smooth muscle, automatic functioning and regulation of internal environment. Smooth muscle is unstriated because myosin and actin filaments goes in all sorts of different directions, no stripey appearance. Skeletal muscle cells have alpha motor neurons that comes in and activates that individual muscle fibre, ap spread by individual nerves going into cell. Calcium ions, which are more concentrated in the ecf, would have a positive equlibrium potential (cell has negative rmp, open calcium channels calcium moves into cell, make it more positive) Rising phase: through voltage gated sodium channels, sodium influx. Falling phase: through voltage gated potassium channels, potassium efflux. Start with high potassium permeability reduces during ap comes back up for the falling phase.
