neuro quiz 1 Tuesday 2/3/14 Flashcards
What causes muscle fatigue?
Lack of neurotransmitters – reduction of Acetylcholine (Ach)
What are the two biggest threats to human performance
Anything that changes the pH or temp of the blood
Name the categories all muscles must have (4)
Excitability (responsiveness or irritability): ability to receive and respond to stimuli
Contractility: ability to shorten when stimulated
Extensibility: ability to be stretched
Elasticity: ability to recoil to resting length
What are the (4) functions of a muscle?
Movement of bones or fluids (e.g.blood, air)
Maintaining posture and body position
Stabilizing joints (alignment)
Heat generation (especially skeletal muscles) – through friction
What is comprised of skeletal muscle; what are they served by?
Each muscle is served by one or more vein, one artery, one nerve
VAN
What is an Action Potential?
stimulus that comes down from the motor neuron to the motor endplates
How does a Muscle Contraction occur?
- A signal moves along the NMG, Ach is released
- ACh transports the message to the muscle
- Electrical activity in the muscle signals calcium to be released from the transverse tubules
- Calcium moves through longitudinal tubule
- Calcium binds to troponin (protein)
- Tropomyosin (inhibitory protein) moves out of the way to allow myosin cross bridge to connect with actin
- Myosin cross bridge connects with actin
- ATP is broken down and releases energy
- Cross bridge moves actin inward causing a shortening of the muscle fiber
- Ratcheting effect continues until contraction is complete
What are the five phases of the Sliding Filament Theory?
Resting Phase – there is no significant muscular tension
Excitation-contraction coupling phase – calcium is released, myosin cross-bridge heads attach to the actin filaments, and cross-bridge heads flex
Contraction phase – myosin cross-bridge heads detach from the actin active sites
Recharge phase – CA, ATP, and ATPase are replenished to allow continued muscle activity
Relaxation Phase – When the motor neuron stops firing, calcium is removed from the myofibril and pumped back into the sarcoplasmic reticulum. This results in tropomyosin moving back to cover and block the active binding sites on actin. Myosin cross-bridges can no longer attach to actin and the muscle relaxes and returns to its resting length.
What is the resting phase of the SFT?
Resting Phase – there is no significant muscular tension
What is the Excitation-Contraction Coupling Phase of the SFT?
Excitation-contraction coupling phase – calcium is released, myosin cross-bridge heads attach to the actin filaments, and cross-bridge heads flex
What happens in the contraction phase of the SFT?
Contraction phase – myosin cross-bridge heads detach from the actin active sites
What happens in the Recharge Phase of the SFT?
Recharge phase – CA, ATP, and ATPase are replenished to allow continued muscle activity
What happens in the Relaxation Phase of the SFT?
When the motor neuron stops firing, calcium is removed from the myofibril and pumped back into the sarcoplasmic reticulum. This results in tropomyosin moving back to cover and block the active binding sites on actin. Myosin cross-bridges can no longer attach to actin and the muscle relaxes and returns to its resting length.
Which protein shields the myosin-binding site, preventing contraction from happening at rest?
tropomyosin
What are the roles of Ca+ and ATP used to assist with muscle actions?
Excitation-contraction coupling
Which is the correct order of events in a contraction?
T-tubule action potential, Ca2+ released, cross-bridging, Ca2+ re-gathered
What is the neurotransmitter used to pass an action potential from nerve to muscle
ACh - Acetylcholine
What are the Different Types of Muscle Cells
Skeletal – attached to bones or some facial muscles) to skin (voluntary)
Cardiac – heart (involuntary)
Smooth – line inside our vessels and stomachs (involuntary)
Which microscopic structures are only found in the cardiac muscle tissue?
Intercalated Discs
Which types of muscle tissue contract when excited by their own autorhythmic muscle fibers?
Cardiac muscle and visceral smooth muscle
Which connective tissue coat surrounds groups of muscle fibers, separating them into fasicles?
Perimysium bundles groups of muscle fibers into fasicles.
Which structure releases calcium ions to trigger muscle contraction?
The sarcoplasmic reticulum releases calcium ions to trigger muscle contraction.
Which of the following is the smallest: muscle fiber, thick filament, or myofibril? Which is largest?
The following are arranged from smallest to largest: thick filament, myofibril, muscle fiber.
Which proteins connect into the Z disc?
Actin and titin anchor into the Z disc.
Which proteins are present in the A band?
In the I band?
A bands contain myosin, actin, troponin, tropomyosin, and titin;
I bands contain actin, troponin, tropomyosin, and titin.
What happens to the I band and H zone as muscle contracts? Do the lengths of the thick and thin filaments change?
The I bands and H zones disappear during muscle contraction; the lengths of the thin and thick filaments do not change.
What would happen if ATP suddenly were not available after the sarcomere had started to shorten?
If ATP were not available, the cross-bridges would not be able to detach from actin. The muscles would remain in a state of rigidity, as occurs in rigor mortis.
What are three functions of ATP in muscle contraction?
(1) Its hydrolysis by an ATPase activates the myosin head so it can bind to actin and rotate;
(2) Its binding to myosin causes detachment from actin after the power stroke;
(3) It powers the pumps that transport calcium ions from the cytosol back into the sarcoplasmic reticulum.
Why is tension maximal at a sarcomere length of 2.2 micrometers?
A sarcomere length of 2.2 micrometers gives a generous zone of overlap between the parts of the thick filaments that have myosin heads and the thin filaments without the overlap’s being so extensive that sarcomere shortening is limited.
What part of the sarcolemma contains acetylcholine receptors?
The part of the sarcolemma that contains acetylcholine receptors is the motor end plate.
Which steps in the contraction and relaxation in skeletal muscle fiber are part of excitation-contraction coupling?
Muscle action potential traveling along transverse tubule opens calcium ion release channels in the sarcoplasmic reticulum membrane, which allows calcium ions to flood into the sarcoplasm.
Calcium ion binds to troponin on the thin filament, exposing the binding sites for myosin.
Contraction; power strokes use ATP; myosin heads bind to actin, swivel, and release; thin filaments are pulled toward center of sarcomere.
Where inside a skeletal muscle fiber does production of ATP for muscle contraction occur?
Glycolysis, exchange of phosphate between creatine phosphate and ADP, and glycogen breakdown occur in the cytosol. Oxidation of pyruvic acid, amino acids, and fatty acids (aerobic cellular respiration) occurs in mitochondria.
What is the effect of the size of a motor unit on its strength of contraction? (Assume that each muscle fiber can generate about the same amount of tension)
Motor units having many muscle fibers are capable of more forceful contractions than those having only a few fibers.
What events occur during the latent period?
During the latent period, the muscle action potential sweeps over the sarcolemma and calcium ions are released from the sarcoplasmic reticulum.
What type of contraction occurs in your neck muscles while you are walking?
Holding your head upright without movement involves mainly isometric contractions.
Which type of smooth muscle is more like cardiac muscle than skeletal muscle, with respect to both its structure and function?
Visceral smooth muscle is more like cardiac muscle; both contain gap junctions, which allow action potentials to spread from each cell to its neighbors.
Which part of a somite differentiates into skeletal muscle?
The myotome of a somite differentiates into skeletal muscle.
What is the functional unit of a skeletal muscle called?
A Sarcomere
What is the role of tropomyosin in skeletal muscles?
Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
The oxygen-binding protein found in muscle cells is ________.
Myoglobin