Week 1 Flashcards
What makes up the epimysium?
tough, connective tissue
What is contained within the perimysium?
the arteries, veins, and nerves associated with skeletal muscle fibers
What covers the myofibrils?
the endomysium
What do muscle fascicles contain?
What do those contain?
muscle fibers
sarcolemma with T tubules, sarcoplasmic reticulum, multiple nuclei
What are the functional units of striated muscle and what do they contain?
- sarcomeres
- thin filament (with actin and regulatory troponin and tropomyosin) and thick filaments (myosin)
What are Z discs?
where both actin and myosin bind to for structure
Where is the M line located?
the middle of the sarcomere
What is the I band?
areas of the sarcomere where only thin filaments are present
What is the A band?
where thick and thin filaments overlap, and is responsible for the dark striations on muscle
What is the H-zone?
the ‘bare zone’ where only myosin is located
Explain the process of cross-bridge cycling.
- system in rigor, with myosin head bound to actin
- ATP binds myosin, giving a conformational change and making myosin release from the actin
- ATP hydrolyzed to ADP and myosin head cocks forwards (towards the + end)
- P released and myosin binds to the actin (the power stroke)
- ADP is released and the system returns to rigor
What are the 3 sources of energy for muscle contraction?
- creatine~P
- glycogen
- FA in the presence of O2
What are type I muscle fibers aka?
Which pathway do they use?
What are the relative amounts of myoglobin, mitochondria, and glycogen?
- slow twitch
- aerobic pathways/oxidative
- lots of myoglobin, lots of mitochondria, less glycogen
What are type II muscle fibers aka?
Which pathway do they use?
What are the relative amounts of myoglobin, mitochondria, and glycogen?
- fast twitch
- anaerobic/glycolytic
- fewer mitochondria, abundant glycogen, fewer myoglobin
In an ATPase stain, how do the muscle fibers stain?
- slow twitch are light tan
- fast twitch are dark brown
In an NADH stain, how do the muscle fibers stain?
- slow twitch are darker
- fast twitch are lighter
Which type of muscle fiber has a higher rate of fatigability?
fast twitch/type II
Where does a large majority of the heart’s ATP come from?
free FA and aerobic metabolism
What is the cell membrane in a myocyte aka?
sarcolemma
What is the cytoplasm of a myocyte aka?
sarcoplasm
What is the ER of a myocyte aka?
the sarcoplasmic reticulum
How do cardiac myocytes attach to one another?
What does this contain?
- intercalated discs
- desmosomes and gap junctions
What is the equation for osmolarity?
pi = Cg(RT)
C = molar solute concentration
g = van’t Hoff
add RT and convert to physical pressure
What does effective osmolarity depend on?
What is it?
What is it aka?
- the reflection coefficient theta
- the tendency for something to pass through a membrane and thereby reduce the effective osmotic gradient
- tonicity
What is the reflection coefficient for things that do not permeate the membrane?
What is it for something that is freely permeable?
0
1
What is the equation for tonicity?
pi = theta x Cg(RT)
Where does water move?
a hypotonic solution has a smaller effective osmolarity than a cell, causing water to move into the cell
How do you calculate the clinical estimation of plasma osmolality?
P = 2[Na] + [glucose]/18 + [blood urea nitrogen]/2.8
What is definition of dehydration?
plasma Na levels over 145 mM/L
Where can you see an increase in the osmolal gap?
when there are solutes in the plasma that are usually not there, such as in alcohol poisoning
What are the narrowly controlled variables?
mean arterial pressure/BP, temperature, hematocrit, PO2, PCO2, pH, fasting glucose, osmolarity, [Na], [K], [Ca], [HCO3]
What is the usual comparator in the human body?
What does it do?
What is this an example of?
- the CNS
- it gets fed info from the sensor about controlled variables and figures out what to do to fix it
- a negative feedback loop
What is the general value for hypotension?
90/60
What is the general value for hypertension?
140/90
What is the value for a fever?
100.4
What ion is higher in the extracellular fluids- Na or K?
Na
What ion is higher in the intracellular fluids- Na or K?
K
Where are cell bodies for motor fibers located?
What kind of signals do they send?
- anterior horn of the spinal cord
- efferent signals
Where are cell bodies for sensory fibers located?
Where do they enter the spinal cord?
- the dorsal root ganglion in the PNS
- the posterior root
What nerves do posterior rami give rise to?
nerves that innervate the intrinsic muscles of the back and the skin overlying that region
What nerves do anterior rami give rise to?
nerves that innervate the anterior and lateral trunk, as well as the extremities
What are the dermatomes in the brachial plexus?
C5, C6, C7, C8, and T1
What do free nerve endings mediate?
pain and temperature sensation
Which things cross to the contralateral side just after entering the spinal cord?
pain and temperature
Where is the T4 dermatome?
the level of the nipples
Where is the T10 dermatome?
the level of the belly button
What would a diminished knee jerk reaction tell you?
there is likely a problem with sensory fibers coming from the muscle or motor fibers going to the muscle
What would an increased knee jerk reaction tell you?
likely a problem with the spinal cord or higher descending influences on the associated gamma motor neurons
What are the branches of the aorta?
- brachiocephalic artery
- left common carotid artery
- left subclavian artery
What responds to brain injury by dividing?
What is this aka?
astrocytes
gliosis
What are the functions of astrocytes?
- gliosis
- end feet make barriers
- structural support
- metabolize some neurotransmitters
- buffer electrolytes
What do ependymal cells do?
line the ventricles and central canal in the brain
What do microglia do?
enter the CNS from the vascular system and act as the major mechanism of immune defense
What do oligodendrocytes do?
each one insulates many axons in the CNS
What do Schwann cells do?
each one insulates only a portion of one axon in the PNS
Explain the process of neuromuscular transmission.
- action potential in nerve reaches the end
- action potential triggers voltage-sensitive Ca channels, causing Ca to enter the cell because of the electrochemical graident
- Ca causes the pre-formed synaptic vessicles to exocytose their chemical message
- neurotransmitter reaches the receptor of the next cell, usually a GPCR or ligand-gated ion channel
- ion channel opened and Na flows in while K flows out down gradients
- depolarization of motor end plate and propagation of action potential in muscle
- neurotransmitter in the cleft gets removed, either by degradation or re-uptake
What is NOT present in the motor end plate?
voltage-gated Na channels
Describe skeletal muscle EC coupling.
- depolarization of the membrane
- voltage sensitive Ca channel has a conformational change
- the Ca channel (physically linked to the membrane with a foot protein) causes the SR Ca release channel (ryanodine receptor) to open
- Ca enters the cytoplasm and binds troponin C for cross-bridge cycling
- Ca transported back to the SR via the SR Ca ATPase pumps (Serca)
Describe cardiac EC coupling.
- depolarization of the membrane
- voltage gated Ca channels open allowing influx of Ca
- Ca that entered binds to the SR Ca release channel (ryanodine receptor) [Ca induced Ca release!!!]
- Ca enters the cytoplasm and binds to troponin C for cross-bridge cycling
- Ca transported back to the SR via the SR Ca ATPase pumps (Serca)
What is the difference between skeletal and cardiac EC coupling?
In cardiac muscle, Ca enters thru the channel.
In skeletal muscle, there is a foot protein in between the Ca channel and ryanodine receptor and that initiates Ca release .
How can you remove Ca from the cytoplasm?
- SR Ca ATPase (Serca)
- Na/Ca exchanger
- sarcolemmal Ca ATPase
What are the 2 ways to increase force in skeletal muscle?
- temporal summation of twitches (slowly increases the Ca concentration)
- recruitment of additional motor units
What things do smooth muscles not have that are present in striated muscles?
- no T tubules
- no sarcomeres or striations
- no troponin
- involuntary
In smooth muscle, what happens after intracellular Ca levels increase?
Ca binds to calmodulin. This increases activity of myosin light chain kinase (MLCK), which phosphorylates the myosin light chains. Myosin ATPase activity is increased leading to cross-bridge cycling and development of force
What are the ways smooth muscle can be activated?
- depolarization from neuron at synapse
- hormones/neurotransmitters make IP3 to cause Ca release from SR
- hormones/neurotransmitters open ligand-gated Ca channels
What does the endomysium surround?
the myofiber
What surrounds the fasicle?
perimysium
When you first apply stimulus to a muscle, what happens?
What is this aka?
- there is force development but no change in length
- isometric contraction
What does muscle shortening depend on?
whether you can overcome the tension or not
How long does the isometric phase last?
until you can generate enough force to overcome the resistance
What is muscle preload?
What does it determine?
- the force applied to a relaxed muscle before stimulation
- resting length
What determines passive force in skeletal muscles?
structural proteins associated with Z lines
What determines passive force in cardiac muscles?
elastic forces
Why is passive force in cardiac muscle important?
prevents overfilling or deformation of the heart
What is the inital length of the cardiac muscle fibers synonymous with?
end diastolic volume
What is the tension in cardiac muscle fibers synonymous with?
stroke volume
What is afterload?
the load or resistance a muscle must contract against (the thing you are trying to lift)
What is the aortic pressure?
the primary afterload that the normal heart must contract against to eject blood
What is afterload called in the heart?
How do you calculate it?
-wall stress
P (ventricular pressure) x r (radius of the ventricle)/thickness of ventricular wall
What is another term for contractility when speaking about heart muscles?
ionotropy
Explain the concept of contractility.
In cardiac muscles, the Ca concentration determines the strength of contraction, not the length of the sarcomere
