Transcript Lecture 32 - People Server at UNCW

REVIEW AND COMPARISON
actin & myosin
sarcomeres (banding)
t-tubules
sarcoplamic reticulum
source of Ca2+
speed of contraction
spontaneous contraction
effect of nerve stimulation
stretch prod. contraction
skeletal
yes
yes
yes
+++
smooth
yes
no
no
+
cardiac
yes
yes
yes
++
SR
SR & ECF
SR & ECF
fast/slow
no
very slow
yes/no
excit.
no
excit./inhib.
yes/no
slow
yes
excit./inhib.
yes
Cardiac Muscle
Autonomic
Myogenic
Slower
contraction
Smooth Muscle
Parts of two muscle cells
Thick and thin filaments
interdigitate, but not
arranged in sarcomeres
Thin filaments anchored to
dense bodies
Muscle fibers connected
by gap junctions
Muscle Energetics
5 µmol•g-1 in fiber
100-1000 µmol•g-1•min-1 needed
muscle fiber
creatine~P
arginine~P
ATP
glycogen
glucose
glycolysis
myosin ATPase
• contraction
• relaxation
SR Ca-ATPase
oxidative metab.
lactate
O2
lipids
(amino acids)
Although it takes a lot more glucose,
ATP can actually be produced faster by
glycolysis than by oxidative phosphorylation:
Rel. rate
Glucose used Lactate prod.
oxidative
metabolism
36-38 ATP
1
0
glycolysis
64 ATP
32
64
Three types of vertebrate skeletal muscle fibers:
Fast glycolytic (white)
(FG)
Fast oxidative-glycolytic
(FOG)
Slow oxidative (red)
(SO)
White and Red Fibers
FG
FOG
SO
Speed of contraction
fast
fast
slow
Source of ATP
glycolysis
mixed
oxid. met.
Myoglobin content
low
intermed.
high
# mitochondria
few
many
many
# capillaries
few
intermed.
many
Glycogen content
high
intermed.
low
Lipid content
low
intermed.
high
Rate of fatigue
fast
intermed.
slow
Skeletal muscles may be a combination of fiber types:
e.g. cat soleus - postural muscle - all SO
cat gastrocnemius -
45% FG, 25% FOG
25% SO, 5% FG/FOG
Different fiber types can be recruited in response
to exercise:
e.g. gastrocnemius of sprinter - high in FG
distance runners - high in FOG + SO
Insect flight muscle:
Time to relaxation in vert. striated muscle is 5 -10 msec.
Some insect wings beat at > 1000 beats • s-1
(midge with wings clipped - 2218 beats • s-1)
Must have contraction/relaxation cycle of
< 0.45 msec !! - surpasses electrical
properties of the membrane
Direct or Synchronous
Indirect or Asynchronous
1. Stretching of muscle induces contraction - no neural activity
or depolarization necessary
2. Resonance of exoskeleton stores energy to stretch
muscles:
notum
wing
pleuron
sternum