COK #5
which sarcomere shortening is true? select all that apply a. the thick and thin filaments slide past each other b. the length of the A band remains constant c. the length of the I band remains constant d. the H zone almost disappears
a b d
in hyperkalemia, the resting membrane potential of a muscle fiber is ____ negative and ____ likely to depolarize a. less; more b. less; less c. more; more d. more; less
a. less; more
a muscle develops its maximal force at its _____? a. shortest length b. intermediate length c. maximal length
b. intermediate length
table salt is fortified with _____ needed for the synthesis of a _____ a. Na; cortisol b. Cl; growth hormone c. iodine; thyroid hormones d. sulfur; ACTH e. K; calcitriol
c. iodine; thyroid hormones
your patient has been prescribed high doses of cortisol after an organ transplant. You measure CRH and ACTH in your patient and expect to find: a. higher than normal concentrations of CRH and ACTH b. normal concentrations of CRH and ACTH c. lower than normal concentrations of CRH and ACTH d. I cannot determine from the information provided
c. lower than normal concentrations of CRH and ACTH
which of the following ions is the most important for propagation of action potential (muscle or neuron)? a. calcium b. chloride c. sodium
c. sodium
which allows action potentials to move rapidly from the cell surface into the interior? a. terminal cisternae b. fascicles c. t-tubules d. cross-bridges e. sarcoplasmic reticulum
c. t-tubules
how do the skeletal muscle fibers in the legs of a marathon runner differ from those of a sprinter who runs the 100-meter dash? a. longer and thinner muscle fibers b. mostly slow-oxidative fibers c. higher mitochondria content d. less likely to fatigue e. all of the above
e. all of the above
which hormone is NOT required for normal growth and development in children? a. growth hormone b. thyroid hormone c. insulin d. testosterone/estrogen e. cortisol
e. cortisol
what are the steps of a simple reflex arc?
step 1 - stimulation of a receptor step 2 - activation of a sensory neuron step 3 - information processing in the CNS step 4 - activation of a motor neuron step 5 - response of a peripheral effector
what happens to sarcomere during contraction?
- A band stays the same, Z lines move closer together, I band gets smaller
high energy form...
- ADP and P bound to myosin - high affinity for actin
what is crucial for myosin?
- ATP
low energy form...
- ATP bound to myosin - low affinity for actin
for maximum contraction, the optimal overlap will have ALL ______ and _____ engaged
- actin and myosin
what is an autonomic reflex?
- all are polysynaptic, with at least one synapse in the CNS and another in the autonomic ganglion
what are intermediate fibers?
- are mid-sized - little myoglobin - slower to fatigue than fast fibers - faster myosin than slow fibers
peri-
- around (collagen and elastic fibers)
what happens if calcium is present?
- bonds to troponin, causing movement of troponin, causing movement of tropomyosin, exposing binding sites for myosin on actin - cross-bridges form between actin and myosin - cycle occurs and muscle contracts
the cross-bridge can't bind until _____ is present?
- calcium
what is skeletal muscle tissue?
- cells are long, cylindrical, striated, and multinucleate - locations: skeletal muscles - function: moves position of skeleton, guards entrances and exits to the digestive system, generates heat
what is cardiac muscle tissue?
- cells are short, branched, and striated - location: heart - function: circulates blood, maintains blood pressure
what is smooth muscle tissue?
- cells are short, spindle-shaped, and nonstriated - location: walls of blood vessels, and in digestive, respiratory, urinary, and reproductive organs - functions: moves food, urine, and reproductive tract secretions
what happens when all of the troponin is bound by Ca2+ and is the result of increasing the rate of stimulation until the relaxation phase is completely eliminated?
- complete tetanus
force is the result of what?
- cross-bridges and power strokes
what is the cross-bridge cycle?
- cyclical formation of links between actin and myosin, resulting in the sliding of thin filaments toward the M line of a sarcomere
what is the relaxation phase?
- decrease in the force being generated until back at rest - decreased Ca2+ - decreased power strokes - decreased cross-bridges
hypothyroidism
- decreased metabolism - cold intolerant - decreased protein synthesis (growth) - decreased excitability of neurons - decreases heart rate and contraction strength - seen with dietary iodine deficiency
what are t-tubules?
- extensions of the cell membrane (sarcolemma) that associate with the ends (terminal cristae) of the sarcoplasmic reticulum
origin equals...
- fixed portion
what is HGH - ethical dilemma?
- genetically engineered GH/exogenous - can interrupt endocrine pathway
what is a monosynaptic reflex?
- has a single synapse between the afferent and efferent neurons
what is a polysynaptic reflex?
- has two or more synapses - this somatic motor reflex has both synapses in the CNS
what is hypercortisolism?
- hyperglycemia (high blood glucose) - tissue wasting (muscles) - adipose tissues increased - most commonly seen in Cushing's syndrome - caused by adrenal tumors (primary disorder), pituitary tumors (secondary disorder), cortisol therapy
what is gigantism (hyper)?
- hypersecretion of GH - growth stops once epiphyseal plates close - cartilage and soft tissue can continue growing - acromegaly
what is hypocortisolism?
- hypoglycemia (low blood glucose) - weakness - fatigue - zona glomerulosa also typically affected - typically caused by autoimmune disorders - may lead to excess sex steroids and adrenogenital syndrome
what are the effects of the thyroid hormone?
- increase the metabolic rate - stimulate all cells of the body - stimulates skeletal growth
what is hyperthyroidism?
- increased metabolism - increased body temp - muscle weakness - hyperexcitable neurons - increases heart rate and contraction strength - most commonly seen in grave's disease - caused by TSH mimics
endo-
- inside (loose connective tissue)
what is eustress?
- is a positive form of stress, usually related to desirable events in a person's life
what is a cross-bridge?
- link between myosin and actin and shy the filaments slide
what is TRH stimulated by?
- low body temp and low levels of T3/T4
what are fast twitch fibers?
- majority of skeletal muscle fibers - contract very quickly - large diameter: more sarcomeres - greater force - large glycogen reserves; few mitochondria - produce strong contractions, but fatigue quickly
more motor units = more fibers =?
- more force
insertion equals...
- moveable portion
what do thick filaments contain?
- myosin
what is the moving actin component?
- myosin head
what is a power stroke?
- myosin head moves, propelling thin filament toward center of muscle
no ATP = ?
- no cross-bridge cycles (rigor mortis)
the amount of tension produced depends on the _____?
- number of power strokes performed - fibers resting length at the time of stimulation - frequency of stimulation
what are the sources of ATP in cross bridge cycling?
- phosphorylation of ADP by creatine phosphate - anaerobic glycolysis (limited supply of O2) - oxidative phosphorylation of ADP in mitochondria (plenty of O2)
what is a reflex?
- rapid, automatic responses triggered by specific stimuli - a specific reflex produces the same motor response each time
what is dwarfism (hypo)?
- rare - caused by decreased synthesis or defective GH receptors
what leads to generating maximum force?
- recruitment of the motor units and all the motor neurons and all the fibers it controls
what is a contralateral?
- response and stimulus are on the opposite side of the body - example: at the same time, will extend the contralateral side to balance yourself
what is an ipsilateral?
- response and stimulus are on the same side of the body (flexor-withdrawal reflex) - example: step on something hot - you will pull the foot up
what is the contraction phase?
- shortening phase - multiple power strokes
does the sarcomere get longer or shorter during contraction?
- shorter
what are the three types of muscle tissue?
- skeletal muscle tissue - cardiac muscle tissue - smooth muscle tissue
what are slow twitch fibers?
- slow to contract and slow to fatigue - small diameter - numerous mitochondria - high oxygen supply from extensive capillary network - contain myoglobin
during exercise, blood flow shifts from the GI tract to skeletal muscle as a result of increased oxygen demand. which muscle type is mainly responsible for redirecting blood flow?
- smooth muscle tissue
what is the growth hormone (GH)?
- somatostatin - released throughout life - with its peak in teenage years
what is the latent period?
- start from AP - till "shortening" begins
what are the effects of cortisol?
- stress response - accelerate glucose synthesis and glycogen formation, especially in liver - have anti-inflammatory effects
what happens when both ends of a myofibril are free to move (sphincters smooth muscle)?
- the ends move towards the center of the myofibril
what happens when one end of a myofibril is fixed in position during contraction (skeletal)?
- the free end is pulled toward the fixed end
what is distress?
- the most-commonly-referred to type of stress, having negative implications
what happens at muscle contraction to filaments?
- thick and thin filaments overlap - neither shorten - filaments slide past each other
what is the purpose behind muscle contraction?
- to generate force
calcium binds to _____ during the cross-bridge cycle?
- troponin
what do thin filaments contain?
- troponin - actin - tropomyosin
what happens is no calcium is present?
- troponin holds tropomyosin over myosin binding sites on actin - no cross-bridges forms - muscle relaxed
epi-
- upon (dense irregular CT)
what is the order of the contraction cycle/cross-bridge?
1. contraction cycle begins 2. active-site exposure 3. cross-bridge formation (myosin binds to actin) 4. myosin head pivoting (power stroke) 5. cross-bridge detachment 6. myosin reactivation