week of mt 2 Flashcards
Muscle fatigue
a skeletal muscle fiber is repeatedly stimulated, the tension the fiber develops eventually decreases even though the stimulation continues. There is a decline in muscle tension as a result of previous contractile activity
Wont respond the same anymore even with the same stimulant
Characteristic of fatigued muscle
a decreased shortening velocity and a slower rate of relaxation. The onset of fatigue and its rate of development depend on the type of skeletal muscle fiber that is active, the intensity and duration of contrac tile activity, and the degree of an individual’s fitness
[ATP] and fatigue
ATP depletion is mechanism for fatigue
Can rest and get back to full tension but not for same duration
ATP depletion and skeletal muscle
Great amount of breakdown when goes from rest to contracted
If a fiber is to sustain contractile activity
metabolism must produce molecules of ATP as rapidly as they break down during the contractile process.
Creatine phosphate
Supports the first ~15 seconds of contractile activity
Sustained contraction requires
Oxidative phosphorylation and/or glycolysis
Fast and slow fibers contain forms of myosin that differ
in
the maximal rates at which they use ATP, and
corresponding differences in proteins that affect the speed
of membrane excitation, excitation–contraction coupling,
and ATP-production mechanisms.
Slow oxidative fibers (type 1)
combine low myosin-ATPase
activity with high oxidative capacity
Fast oxidative glycolytic fibers
(type 2A) combine high myosin-ATPase activity with high oxidative capacity and intermediate glycolytic capacity.
Fast glycolytic fibers
type 2X) combine high myosin-
ATPase activity with high glycolytic capacity.
Slow-twitch fibers have
low
activation threshold, meaning
they are the first recruited when a
muscle contracts. If they can’t
generate the amount of force
necessary for the specific activity,
the fast-twitch muscle fibers are
engaged.
Interstitial fluid takes on
Same composition of the arterial blood
Bulk flow
-mechanism for maintaining fluid balance between the blood and the extracellular space.
- pores in capillary walls permit the flow of plasma, but not proteins or blood cells.
- bulk flow into the tissues is called ultrafiltration.
- bulk flow into the capillaries is called reabsorption.
Ultrafiltration
Bulk flow into the tissues
Reabsorption
Bulk flow into the capillaries
Veins
serve as a reservoir for blood and a conduit for blood flow back to the heart.
have less smooth muscle and MORE ELASRIN than arteries.
are highly distensible, so they are called capacitance vessels that act as blood reservoirs.
Venous capacity
volume of blood the veins can accommodate.
- depends on the distensibility of the venous walls and
the influence of any externally applied force.
Venous return
Volume of blood entering each atrium per minute
Venous valves
Located within the lumen of large veins and prevent the backflow of venous blood
Without venous valves
contracted skeletal muscle would squeeze blood both towards and away from the heart
Respiratory activity
pressure within the chest cavity transiently decreases during respiration. This increases the pressure gradient between the veins in the lower extremities and the chest.
Baroreceptor reflex
autonomically regulates cardiac output and total peripheral resistance.
- Baroreceptors respond to changes in arterial blood pressure by elevating or reducing their rate of firing.
- These signals alter the ratio of activity in the parasympathetic and sympathetic neurons of the cardiovascular control centers.
Baroreceptors
mechanoreceptors sensitive to changes in both mean arterial pressure and pulse pressure.
- Constantly provide information about blood pressure.
- When arterial pressure increases, the firing rate of their
afferent neuron increases. When arterial pressure decreases, the firing rate of their afferent neuron decreases.
Influence of parasympathetic activity on arterial blood pressure
Heart—— decrease in heart rate only
Influence of sympathetic activity on mean arterial blood pressure
Heart — heart rate and contractile strength
Arterioles— vasoconstriction
Veins—- vasoconstriction
General function of respiration
To obtain O2 for use by the body’s cells and to eliminate the CO2 the body produces
2 separate but related processes of respiration
External respiration
Internal (cellular) respiration
Trachea and larger bronchi
– Fairly rigid, non-muscular tubes
– Rings of cartilage prevent collapse
Bronchioles
– No cartilage to hold them open (control gas exchange; can collapse)
– Walls contain smooth muscle innervated by the autonomic nervous system:
Parasympathetic stimulation constricts
Sympathetic stimulation (weakly) relaxes
Epinephrine relaxes (2 receptors!)
Alveoli
• Thin-walled inflatable sacs
• Function in gas exchange
• Walls consist of a single layer of
flattened Type I alveolar cells
• Type II alveolar cells secrete
pulmonary surfactant
• Alveolar macrophages guard lumen
- pulmonary capillaries encircle each alveolus
Pulmonary surfactant
Surfactant produced by Type II alveolar cells disrupts hydrogen bonding of water lining the alveolar wall (mixture of protein and lipid: acts like a detergent)
Decreases surface tension so groups of little bubbles don’t collapse into a smaller number of bigger ones
Surfactant induced by cortisol just prior to birth; premature infants may need synthetic glucocorticoid treatment to ensure proper lung function
Iron lung
Takes care of gas exchange for you
Best analogy for our lungs inflate
Inflate like a smiths bellows
Expand the ribcage and air flows in