Bio exam 3

• Anatomy of a muscle fiber all the way down to an individual sarcomere

  -Myofibrils squish together to form a muscle fiber which are your actual muscle cells that have mitochondria, multiple nuclei, and a cellular membrane called a sarcolemma.

  -muscle fibers them form a large string-like bundle called fascicles, which combine together within an overall muscle

  -myofibrils are divided lengthwise into sarcomeres and have two proteins: Actin & myosin. Sarcomeres are separated by z-lines and striated (dark and light bands)
• Anatomy of muscle fibers (skeletal muscle)

  -the epimysium wraps around the entire muscle, the fascicles are wrapped around perimysium, the endomysium wraps around every muscle fiber to help the muscle from bursting.

  -striations (thick and thin): I bands- only thin filaments, A bands- contain thick filaments with some thin filament overlap, H bands at the center of A bands w/ no overlap, Z disc are found in the center of each I band.
• Biomechanics of skeletal muscle (force/velocity/motor units/recruitments)

  -force and velocity are inversely related. As you increase force, you reduce velocity.

  -you slow velocity down you can create more force. slower velocity higher force in the muscles

  -create more for force than the opposing force which is gravity. for example when your biceps have to create more force, than the forces of gravity that is being applied on a barbell and when you let it down you are still applying force and your muscles lengthen when applying force.
• Biomechanics of skeletal muscle (force/velocity/motor units/recruitments)

  -the force applied does not exceed the forces being exerted on the object

  -Motor unit recruitment refers to the number of motor units activated during a contraction. The type of overall muscle movement produced will depend on the recruitment of different size units, different strength of units, and the quantity of the units.

  -if you want to have very fine control over a body part what we need to have is lots of motor units, and each muscle unit has fewer muscle fibers it controls.
• How do motor units vary in size and what does it mean for the function of different muscles

  Small motor units produce smaller amount of force, whereas large motor units generate greater force (Figure 11). Smaller and more delicate muscles such as the eye muscles have smaller motor units (a dozen fibers), while powerful leg muscles possess large motor units that contain over 1000 fibers.

  -23 muscle fibers contract in your eye muscle

  -1,000 muscle fibers contract at the same time in your calf muscle

  -if you want to apply maximal force you need to slow it down
• Factors influencing relative strength of muscle contraction like length tension relationship

  -number of fibers recruited

  -Frequency of stimulation

  -Thickness of each muscle fiber

  -Initial length of fiber at rest

  -Muscle lengthens as it maintains tension. Muscle contracts but there is no movement, muscle stays the same length. A muscle contraction that pulls on the bones and produces movement of body parts. The force generated by the muscle is always less than the muscle's maximum.
• What are the different sources of energy utilized

  -At rest and for mild exercise: aerobic respiration of fatty acids

  -For moderate exercise: glycogen stores

  -For heavy exercise: blood glucose

  -the muscle requires a majority of it's energy to create power strokes

  -as the intensity starts to increase over the length of time you're exercising you start to dip into more glucose and glycogen storages.
• How does this vary based on muscle fiber type

  -Type 1 (“slow twitch”) fibers contain more mitochondria, which means they can produce more energy and are better for long, aerobic activities. Type 2 (“fast twitch”) fibers, on the other hand, are suited for short, fast bursts of activity that don't require as much oxygen.

  -VO2 max: the overall amount of oxygen you can take from the air, transport to the blood stream, and use during exercise. Determines intensity level for a given person.
• understand the different factors that lead to muscle fatigue

  -Accumulation of extracellular K+: High levels of potassium cause abnormal heart and skeletal muscle function by lowering cell-resting action potential and preventing repolarization, leading to muscle paralysis.

  -Reducing membrane potential has to do with K+ gradient

  -Depletion of stored glycogen: When muscle glycogen stores are low, muscle cells cannot produce ATP rapidly enough to maintain exercise intensity

  Fatigue of upper motor neurons (CNS), called central fatigue- your brain getting tired of doing the same thing.
• understand the different factors that lead to muscle fatigue

  -Reduced SR calcium release: If Calcium does not get released the muscle can't contract

  -Lactic acid accumulation: Muscle ache, burning, rapid breathing, nausea, stomach pain due to lactic acid build up in the muscles after an intense workout.

  -Lack of ATP/buildup of ADP: during anerobic exertion you blow through ATP your muscles will have less energy and has to be replenished, but ATP does not get replenished fast enough while you work out.
• muscle contraction(sliding filament theory)

  1. Neurotransmitters move along the axon of a somatic motor neuron

  2. ACH is released

  3. ACH binds to receptors

  4. Na+ channels open (leading to an action potential in the sarcolemma)

  5. Depolarizes

  6. Action potential travels along T-Tubules

  7. Ca2+ channels in SR open

  8. Calcium rushes out

  9. Calcium binds to troponin

  10. Tropomyosin moves out of the way

  11. Cross bridges form

  12. ATP will split(ADP/Pi)

  13. Myosin will cock back

  14. grabs onto actin

  15. spits out phosphate & ADP

  16. Myosin pulls Actin toward the center

  18. releases actin/new ATP
• This process of muscle contraction is repeated until the muscle contracts as far as we decide; basically the sliding filament theory
• Muscle relaxation

  -Relaxing skeletal muscle fibers, and ultimately, the skeletal muscle, begins with the motor neuron, which stops releasing its chemical signal, ACH. The muscle fiber will repolarize, which closes the gates in the SR where Ca++ was being released. ATP-driven pumps will move Ca++ out of the sarcoplasm back into the SR. This results in the “reshielding” of the actin-binding sites on the thin filaments. Without the ability to form cross-bridges between the thin and thick filaments, the muscle fiber loses its tension and relaxes.
• muscle contraction and relaxation

  
• Basic anatomy of the system (conducting vs respiratory zones)

  -The Respiratory system is the structural make up of the body that is going to supply the blood with oxygen and dispose of carbon dioxide.

  -the conduction zone makes up the vast majority of structural volume of the Respiratory system. Moves air from your nose and your mouth down into your lungs. it also filters, humidify, and warm the air as it moves into the lungs.

  -the respiratory zone is the deepest portion of your lungs where gas exchange occurs. gas exchange happens in the alveoli.
• Modifying volume of thoracic cavity and subsequent changes in pressure

  -During inspiration, the diaphragm contracts and the thoracic cavity increases in volume. This decreases the interalveolar pressure so that air flows into the lungs.

  -This increases the size of the thoracic cavity and decreases the pressure inside. As a result, air rushes in and fills the lungs. The second phase is called expiration, or exhaling. When the lungs exhale, the diaphragm relaxes, and the volume of the thoracic cavity decreases, while the pressure within it increases.
• modifying volume of thoracic cavity

  This increase in the volume of the thoracic cavity lowers pressure compared to the atmosphere, so air rushes into the lungs, thus increasing its volume.
• Review all the different types of pressure involved. How each one influences the process of breathing

  -Atmospheric pressure: air outside body. When you inhale, your diaphragm contracts, creating a pressure difference between the inside of your lungs and the atmosphere. The higher atmospheric pressure pushes air into your lungs, allowing you to breathe.

  -Intrapulmonary pressure: within the lungs. with inspiration the the pressure becomes lower than atmospheric and air comes rushing in. With expiration the pressure becomes greater than atmospheric pressure and air leaves.
• the third type of pressure is

  Intrapleural pressure: within intrapleural space. Lower than intrapulmonary and atmospheric pressure. Keeps lungs against thoracic wall and allows lungs to expand during inspiration.

  -the pressure in the intrapulmonary and atmospheric have to be higher while interpleural has to be lower so that our lungs don't collapse.

  -if the lungs do collapse it's b/c the pressure became higher than the atmosphere
• 3 Properties of lung tissue as they relate to physiology

  -Compliance: how stretchy something is. Compliance of the respiratory system describes the expandability of the lungs and thoracic wall.

  -Elasticity: if stretchy how can it return to it's original size.

  -Surface tension: the tension created on a surface of a liquid. water creates cohesion(tends to stick together) water at the top creates downward force to bind to the water below it b/c there is not water at the top to stick to. Surfactant to keep alveoli from collapsing.

  -high surface tension = low compliance
• Restrictive vs Obstructive

  Restrictive: having trouble getting air into the lungs and transferring that oxygen to the blood(lung tissue being damaged).

  Obstructive: perfectly healthy lungs but the passage way of air into the lungs is restricted.

  -Restrictive is damage to the Respiratory zone, obstructive is damage to the conducting zone
• Restrictive vs obstructive lung disorders

  -Obstructive lung diseases include conditions that make it hard to exhale all the air in the lungs. People with restrictive lung disease have difficulty fully expanding their lungs with air.

  
• Be prepared to explain how involuntary (automatic) breathing is modified and managed(Systems/sensors used)

  -The medulla, located nearest the spinal cord, directs the spinal cord to maintain breathing, and the pons, a part of the brain very near the medulla, provides further smoothing of the respiration pattern. This control is automatic, involuntary and continuous. You do not have to consciously think about it.

  -Automatic control of breathing influenced by feedback from chemoreceptors, pH of fluids in brain and pH, PCO2,PO2 of the blood
• Different forms of hemoglobin

  -Oxyhemoglobin/reduced (deoxyhemoglobin) hemoglobin: Iron reduced form (Fe2+) and can bind with O2.

  -Methemoglobin: Oxidized iron (Fe3+) can’t bind to O2. methemoglobinemia, the hemoglobin can carry oxygen, but is not able to release it effectively to body tissues.

  -Carboxyhemoglobin: Hemoglobin is bound to carbon monoxide
• motor units and how they very in size and number: motor units are made up of a single motor neuron and a single muscle fiber