Comparison of muscle types

Question 1

skeletal function and structure

Answer 1

posture
heat
movement
on demand- individual and specific. activation of different subgroups of muscles that are needed for an activity ie. standing vs sitting
cells fuse together to make long, cylindrical multinucleate cells. they all point in the same direction and contract in the same direction. allows for linear movement

Question 2

cardiac function

Answer 2

pumping blood

continuous all at once, build pressure to maintain life.

Question 3

smooth function

Answer 3

smooth muscle forms ring around the tube tract
they control the movement of what is going through the tube by controlling the diameter
relaxed = bigger tube = more flow of liquid in tube
contraction = smaller tube = less flow of liquid in tube and increase in pressure = harder for movement
individual - specific, some go through out your life and some just when needed.
autonomic system

Question 4

Cardiac structure

Answer 4

lots of individual cells that are stuck together by intercalated disks (squiggly lines)
mono-nucleate branching cells, single nucleus.
the cells branch and make connections with other cardiac cells.
desmosomes (mechanical) hold the cells together and for the movement of contraction
gap junctions (electrical) are electrical connectors and this allows one action potential to travel from one myosin to the next one that is connected.
made up of actin, myosin and z disks
not all point in the same direction, the heart is like a ball we need to contract the whole thing to produce force in more than one direction not just linear.

Question 5

Co-ordinated contraction of the heart

Answer 5

Depolarised atria (sinoatrial node to atrioventricular node and the pacemaker)
Depolarised septum (middle bit between chambers)
Depolarised apex (bundle of his)
Depolarised ventricles (purkinie fibres)
Depolarised further then fully depolarised (whole bottom half)
this is a mini nervous system that is all connected with gap junctions and is electrically coupled.

Question 6

Smooth muscle structure

Answer 6

when you contract the muscle all of the cells are in a network that pulls everything together. the mesh tightens and the overall effect isn’t just shortening it is a change in shape as well.
it isn’t a linear contraction it is squeezing the cell down in all directions
these can be sustained for a very long time with large changes in length and sustained tension
mono-nucleate spindle-shaped cells. cells roughly point in the same direction and will generally contract in the same axis like squeezing a tube.

Question 7

single unit smooth muscle

Answer 7

gap junctions allow for the spread of excitation between cells
all under autonomic control
cells form a ring around the digestive tract.all cells are connected electrically through gap junctions.
if one is activated then they are all activated. they move and contract as a single unit
eg. digestive, urinary and reproductive tracts

Question 8

multi-unit smooth muscle

Answer 8

absence of gap junctions allowing for fine control of individual muscle cells
not all contract at the same time
autonomic nervous system
a single neuron innervates each muscle cell and each cell has to be activated individually
eg. pili muscles in the skin, eye muscles and blood vessels

Question 9

smooth muscle excitation - contraction

Answer 9

an action potential on the outside will trigger the opening of the Ca2+ ion channels and this triggers the opening of the Ca2+ ion channels in the sarcoplasmic rectilium to open. the Ca2+ then binds to the calomodium. the ca-caladonium complex activates the MLCK (myosin light chain kinase) which activates the MLC (myosin light chain) which activates the cross bridges between the actin and myosin filaments.
the myosin filament is regulated and controls the cross-bridges

Question 10

striated

Answer 10

sarcomeres

bonds that appear because of the overlap of actin and myosin are the dark lines.

Question 11

skeletal muscle striations

Answer 11

yes
actin and myosin organised along an axis therefore stronger force along the axis
thin actin filaments regulated - calcium and troponin

Question 12

cardiac muscle striations

Answer 12

yes

same as skeletal muscle actin and myosin organised along an axis

Question 13

smooth muscle striations

Answer 13

no
actin and myosin filaments arranged in various directions so exert weaker force but in various directions
thick myosin filament regulated
calcium - calmodulin- MLCK- MLC

Question 14

action potential spread from cell to cell?

skeletal muscle

Answer 14

no
organised into motor units- one fibre activated by one motor neuron and getting input from one neuron
t-tubule allows for near simultaneous contraction

Question 15

action potential spread from cell to cell?

cardiac muscle

Answer 15

yes
via the gap junctions
syncytium - bunch of cells that contract in a co-ordinated way
t-tubuli

Question 16

action potential spread from cell to cell?

smooth muscle

Answer 16

yes/ no
via gap junctions only in single unit smooth muscle
there is a spectrum from gap junctions to multi with a range of how it is spread.
no t-tubuli

Question 17

control - skeletal muscle

Answer 17

voluntary

each cell has one synapse (NMJ) and it is organised into motor units

Question 18

control - cardiac muscle

Answer 18

involuntary
no discrete synapses “spontaneous” depolarisations initiated by pacemaker cells, self exciting
modified by the autonomic nervous system and hormonal inputs

Question 19

control - smooth muscle

Answer 19

involuntary
no discrete synapses can be spontaneous (pacemaker) or initiated by nerve input. some are spontaneously active and some only contract when the nervous system tells them too

Question 20

speed of skeletal muscle contraction

Answer 20

fast

Question 21

speed of cardiac muscle contraction

Answer 21

slow - lasts a very long time

Question 22

speed of smooth muscle contraction

Answer 22

very very slow