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the entire process of coordinated, voluntary muscle contraction is summed up as excitation-contraction coupling. Why are these two things coupled. and what,specifically, is responsible for bring education and contraction together in the muscle cell? in other words,what physically connects, or bridges,the two parts?

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Casey Durgan
Casey DurganLv2
28 Sep 2019

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Related questions

The molecular process that makes muscle contraction possible is that ATP binds to myosin, which releases the energy needed to make the muscle contract. In this problem, we will examine the quantities of energy involved in this process.

**NEED HELP WITH PARTS C, D & E, but all input is appreaciated**


Part 1

The reaction of ATP hydrolysis catalyzed by myosin (M) occurs in several steps*:

M + ATP → M·ATP

M·ATP → M·ADP·Pi

M·ADP·Pi → M·ADP + Pi (aq)

M·ADP → M + ADP

* T. Kodama & R.C. Woledge, "Enthalpy Changes for Intermediate Steps of the ATP Hydrolysis Catalyzed by Myosin Subfragment-1", J. Biol. Chem. 254(14), 6382-6836

According to experimental data, the heats of reaction for these four reactions are -90 kJ/mol, +83 kJ/mol, -88 kJ/mol, and +72 kJ/mol.

a) Based on what you know about chemical bonding (from this class, from chemistry, and from anywhere else), explain the positive and negative signs for each of these four reactions. What does a positive and a negative sign mean, and why is a positive (or negative) sign expected in each case?




b) Find the total energy released (in kJ/mol) in the overall ATP hydrolysis reaction.




Part 2

The energy released by this reaction in each muscle fiber, multiplied by a huge number of muscle fibers, results in the kinetic energy of your muscles moving.

c) Estimate the kinetic energy of your leg when you are walking at a normal pace.




d) Using the data from Part 1, estimate the total energy released by ATP-myosin reactions throughout your entire leg. Explain how you arrived at this estimate.




Some possibly useful information: Muscle fibers (cells) are composed of many myofibrils, tubular components measuring 1-2 micrometers in diameter. Each myofibril is divided along its length into sarcomeres (the basic unit of a muscle, with a single myosin filament), each of which is about 2 micrometers long. Remember that "kJ/mol" means kilojoules for every 6.02×1023 myosin molecules.

e) Are the results from parts c and d similar? If not, what are some possible ways to account for the discrepancy?

1)What type of cell allows the immune system to respond morequickly if the same antigen is encountered a second time?

A)leukocytes

B)memory cells

C)macrophages

D)neutrophils

E)natual killer cells

2)why is the heart divided funtionally into two separate pumpsthat work in series?

A)because arteries carry blood away from the pump and veinsbring blood back to the pump

B)because blood decreases in pressure as it travels throughcirculation

C)because vessles in the vasculature keep blood moving in onedirection'

D)because there are four chambers to the heart

E)none of the above-the heart contracts in unison and is notdivided into two pumps

3)which of the following statements is correct?

A)Na+,K+, Ca2+ and Cl- are all more concentrated in theEXTRACELLULAR fluid

B)Na+, K+, Ca2+ and Cl- are all more concentrated in theEXTRACELLULAR fluid

C)Na+, Ca2+, and Cl- are all more concentrated in theEXTRACELLULAR fluid

D)K+, ca2+ are more concentrated in the EXTRACELLULAR fluid

E)K+, Ca2+ are more concentrated in the EXTRACELLULAR fluid

3)During skeletal muscle contraction:

A)the width of the H-zone decreases

B)the actin heads bind to myosin chain

C)ATP hydrolysis requires Ca2+ as a cofactor

D)tropomyosin changes conformation when Ca2+ binds

E)all of the above occur during skeletal muscle contraction

4)The rapid depolarization phase of myocardial contratile cellaction potential is due to the movement of which ion(s)?

A)Ca2+ flows into the cytosol

B)K+ flow out of the cytosol

C)Na+ flow into the cytosol

D)Ca2+ flow out of the cytosol

E)K+ flow into the cytosol

5)You are a physiology graduate student asked to study theeffect of ion permeability on the initiation of action potentials.You have isolated a cell with resting membrane potential of -70mVand have determined that the cell's threshold voltage is -55mV. Youthen change the cell to make it less permeable to K+ ions(Eions=-90mV)

With all ther condition staying the same, has cell's restingmembrane potential been DEPOLARIZED or HYPERPOLARIZED; and will thecell require a greater or smaller stimulus to reach threshold?

A)hyperpolarize; smaller

B)depolarize;greater

C)hyperpolarize;greater

D)depolarized; smaller

E)none of the above answers are possibe

6)Skeletal muscle cells are UNUSUAL in that they :

A)lack smooth endoplasmic reticulum

B)have no mitochondria

C)depend entirley on anaerobic respiration

D)have MULTIPLE nuclei

E)none of the baove are found in the skeletal muscle cells

7)What is the name for the autonomic nervous system synapses atthe neuroeffector?

A)electrical synapses

B)axon viscosities

C)bidirectional synapses

D)axon varicosities

E)light bulb synapse

8)Which cytokines are involvedin making cells resistant toviruses?

A)colony-stimulating actors

B)interferons

C)erythrpoietin

D)major histocompatibility complex

E)none of the above can make a cell resistant to a virus

9)If a person switiches from normal breathing to more shallowbreathing, whcih statement is true

A)tidal volume decreases

B)alveolar PO2 decreases

C)alveolar ventilation decreases

D)"a" and "b"

E)"a", "b', and "c"

10)Which scenerio supports hyperpolarization of pre-synapticcell?

A)allowing Cl- ions into the cell

B)allowing K+ ions to leave the cell

C)allowing Ca2+ ions into the cell

D)"a" and "b"

E)"a", "b", and "c"

11)The gap junctions in cardia muscle are part of specializedcell junctions that are localized to the__________.

A)transverse tubules

B)intercalated discs

C)Interdigitated fingers

D)desmosomes

E)high-end shppoinf malls

12)What role does myosin light chain kinase (MLCK) play insmooth muscle cell contraction?

A)dephosphorylates myosin

B)phosphorylates actin

C)phosphoylates myosin

D)dephosphorylates actin

E)both "a" and "c"Given that your forearm is 30cm long and yourbiceps inserts 2 cm away from your elbow joint, how much force mustyour biceps exert to hold up a 10kg weight?

A)0.67kg

B)6.0kg

C)20kg

d)150kg

e)600kg

Reflex Lab Procedures for Reflex Lab In this lab we will test muscle stretch reflexes and cutaneous reflexes. A partner is needed to be the subject for this lab. Purpose: To test and observe normal muscle stretch and cutaneous reflexes. Equipment: Reflex hammer, Background: In the most narrow sense, a reflex is an involuntary, unpremeditated response by the body to an external stimulus. Reflexes allow reaction to a stimulus more quickly than would be possible if conscious thought were involved. A reflex can be described as a stimulus-response cycle. Most reflexes involve the brainstem or the spinal cord and do not require interaction from higher brain centers. The muscle stretch reflexes are the simplest reflexes. They involve the sensory neuron synapsing directly upon the motor neuron. They are sometimes called monosynaptic reflexes. They are also called spinal reflexes because the reflexive action does not require input from the brain. The other reflexes we will be testing in this lab are the cutaneous reflexes. They are also called superficial reflexes because the receptors are in the superficial areas of the body. They are more complex and require the message to go up the spinal cord to the brain and then back down to elicit the response. These can be used to test for CNS injury. There are five components to a reflex; these components together are called the reflex arc. The components are as follows: sensory receptor – receives the stimulus and generates an impulse (is usually a nerve ending) afferent pathway – a neuron that carries the impulse from the receptor to a central integrating center integrating center –this is where the afferent component connects to the efferent component- this is in the CNS. One or more synapses must occur here. Interneurons are not involved in stretch reflexes but are always found in all other types of reflexes. efferent pathway - a neuron that carries the impulse from the integrating center to an effector. effector -receives the impulse and responds. The effector may by skeletal muscle, smooth muscle, or glands.

Part I. Stretch reflexes.

First do muscle stretch reflexes which are also called deep tendon reflexes.

It is important the subject relax the muscle being tested. Tell the subject to let the muscle go limp.

Rate each response according to the following scale:

+4 very brisk, hyperactive, large movement at joint.

+3 brisker than average, medium movement at joint

+2 average, small movement at joint

+1 somewhat diminished, very small or no movement at joint

0 no response

A. Patellar (also called the knee jerk reflex) – activation of femoral nerve. The receptor is located in the quadriceps muscle, the effector is the quadriceps muscle. The nerve ending is responding to the stretch of the muscle caused by striking the tendon.

1. A subject is allowed to sit comfortably on a table with knees dangling over the edge.

2. Using a reflex hammer (or substitute as described above) strike the patellar tendon just below the kneecap.

3. Observe the action caused by the reflex.

4. Record your results using the graded scale above.

B. Biceps Reflex – activation of the musculocutaneous nerve

1. Rest subject’s left forearm along your left forearm.

2. Subject’s hand should rest in or near the bend of your elbow.

3. Press your left thumb on the subject’s biceps tendon, apply a little pressure.

4. Strike your thumb with the reflex hammer, this will transfer the pressure to the biceps tendon.

5. Watch carefully for twitching of the biceps muscle. Usually, the forearm will not move.

6. Record your results using the graded scale above.

C. Triceps reflex – activation of the radial nerve.

This is a difficult reflex to observe, but give it a try.

1. The subject should have the arm relaxed and elbow bent.

2. Support the entire weight of the arm with your left hand.

3. Strike the triceps tendons, just above the elbow.

4. Watch carefully for twitching of the biceps muscle.

5. Record your results using the graded scale above.

Both B and C show up best on someone who doesn’t have a lot of subcutaneous fat and who has good muscle definition.

D. Achilles reflex (also called ankle-jerk reflex) – activation of the poplitealnerve. The principle is similar to the knee-jerk reflex. Here the stretch receptors are located in the gastrocnemius muscle.

1. Have the subject take her/his shoes and socks off, exposing the Achilles tendon on the back of the ankle.

2. Strike the Achilles with the reflex hammer (or substitute) and observe the extension of the foot downward.

3. Record the results using the graded scale above.

Part II. Cutaneous reflexes

A. Plantar reflex

This reflex differs from the four muscle stretch reflexes. In this reflex, receptors are stimulated in the sole of the foot (cutaneous receptors). The reflex pathway travels up the leg to the integrating center. While in the integrating center, the reflex travels up the spinal cord through the pyramidal tracts, which are nerve pathways between the spinal cord and brain.

1. The subject needs to lie on his or her back, with shoes and socks off.

2. Using the end of the handle of the reflex hammer, trace a path along the lateral side from heel to the little toe to the big toe.

3. Observe for the flexion (toe curling) which is recorded as a normal plantar reflex.

4. If the toes curl, this is called a Negative Babinski response and is normal. If the toes flare, then an abnormal response is recorded and is called a Positive Babinski response and indicates CNS damage.

5. Record the results.

B. Ciliospinal reflex – This reflexive pathway is from the skin to the thoracic spinal cord, through the sympathetic trunk, then to the dilator pupillae muscle of the eye. This is another test of the CNS.

1. Pinch the back of the subject’s neck,

2. Watch pupils for a response.

3. A normal response is dilation of the pupil.

4. Record your results.

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