Bio-210: Exam 3 Chapter 7 Muscular System

Explain what is meant by the statement that, "A muscle is never entirely relaxed." Yes, this question is asking you to talk about muscle tone.

A muscle is never entirely relaxed, some fibers react at different times to provide muscle tone, normal tension of a muscle at rest= muscle tone.

Compare and contrast slow twitch and fast twitch muscle fibers.

"Twitch" refers to the contraction, or how quickly and often the muscle moves. Slow-twitch muscle fibers are all about endurance or long-lasting energy. In comparison, fast-twitch muscle fibers give you sudden bursts of energy but get tired quickly.

Define the terms: Agonist and Antagonist

-An agonist is a drug that binds to the receptor, producing a similar response to the intended chemical and receptor. -Whereas an antagonist is a drug that binds to the receptor either on the primary site, or on another site, which all together stops the receptor from producing a response.

Regions of a sarcomere

-I band = Light band -A band = Dark band

What is the function of a Titin protein? What two regions of the sarcomere does it connect?

-One of the protein's main jobs is to provide structure, flexibility, and stability to these cell structures. Titin interacts with other muscle proteins, including actin and myosin, to keep the components of sarcomeres in place as muscles contract and relax. -Z disc: it is the area where two actin filaments connect and transverse the I bands. Similarly, sarcomere can also be described as the structure between the two z discs.

Sketch the length tension curve and use it to describe the optimum length for a forceful muscle contraction. Make sure to explain what arrangement of actin and myosin is responsible for a forceful muscle contraction.

-The isometric length-tension curve represents the force a muscle is capable of generating while held at a series of discrete lengths. -The LT curve describes the maximum isometric force a muscle generates as sarcomere lengths vary. As muscle is stretched from extremely short to extremely long lengths, the force it generates increases over the ascending limb, peaks in the plateau region and decreases over the descending limb

What is a "triad" referring to?

1 T tubule and 2 terminal cisternae

Briefly summarize the four actions necessary for muscle contraction and relaxation

1) Excitation = nerve action potentials lead to action potentials in muscle fiber 2) Excitation-contraction coupling = action potentials on the sarcolemma activate myofilaments 3) Contraction = shortening of muscle fiber 4) Relaxation = return to resting length

What are the three phases of twitch AND what is happening on the molecular and cellular level during each of these phases?

1.Latent period before contraction: •the action potential moves through sarcolemma •causing Ca2+ release 2.Contraction phase: •calcium ions bind to troponin C •tension builds to peak 3. Relaxation phase: •Ca2+ levels fall •active sites are covered •Where? •tension falls to resting levels

Muscle cells are packed full of which structure, which contains myofilaments?

A Sarcomere

Which band of a sarcomere has actin and myosin?

A band

Draw AND describe what twitch would look like on graph.

A single, brief contraction

What protein is the thin filament made of?

Actin: tropomyosin and caldesmon

What is creatine phosphate in terms of a supplement? Specifically, who is it going to benefit? Why?

An amino acid compound that works during the initial minute of walking or a couple seconds of sprinting. It gives you energy and more ATP to be used during workoutIt is going to benefit athletes in order to get more energy

What does Angiotensin II & Vasopressin do to smooth muscle within a blood vessel?

Angiotensin II Induces Vascular Smooth Muscle Cell Replication Independent of Blood Pressure. Affects both contraction and growth of vascular smooth muscle cells through a complex series of intracellular signaling events initiated by the interaction of angiotensin II with the AT1 receptor.

What is DOMS? What exactly causes it?

Delayed onset muscle soreness (DOMS) also known as 'muscle fever'. It is a sore, aching, painful feeling in the muscles after unfamiliar and unaccustomed intense exercise. DOMS is thought to be due to temporary muscle damage and inflammation for which the most common trigger appears to be eccentric exercises.

Explain, in detail, the concept of a motor unit. How would the arrangement of a motor unit differ for Fine control vs. Gross control?

Each motor neuron and all the muscle fibers it innervates = motor unit •A motor neuron and the muscle fibers (myocytes) it innervates -•dispersed throughout the muscle -•when contract together causes weak contraction over wide area -•provides ability to sustain long-term contraction as motor units take turns resting (postural control) •Fine control -•small motor units contain as few as 20 muscle fibers per motor neuron -•i.e. eye muscles •Gross (Power) control -•Larger motor units for power moves -•i.e. gastrocnemius muscle has 1000-2000 fibers per motor neuron

What types of things would an endurance athlete be concerned with? Explain!

Endurance is long term, so they need good supply of glycogen stored in the muscles and to have a rich supply of oxygen (good energy and oxygen)

Describe what is occurring when a muscle goes into "oxygen debt." Make sure to explain EPOC in your response.

Excess Postexercise Oxygen Consumption: oxygen is consumed to bring physiological variables to resting levels, taking oxygen from myoglobin, high metabolism, shoving in oxygen to pay the loan back Ex: Me breathing heavy after taking the stairs

Describe on a molecular and cellular level what is occurring when a muscle becomes fatigued.

Fatigue is when the muscles get tired, the more we use them...We use up our glycogen and it starts to declineATP production slowsNMJ acetylcholene is used upNaK pump - it falls behind and cannot keep up

Which region of a myosin molecule attaches to actin? (Hint: it looks like a golf club head/frog leg).

Globular MYOSIN HEAD bind to actin filaments.

Which zone of a sarcomere has only "bare" myosin?

H zone

Which band of a sarcomere contains only actin?

I bands (or isotropic bands)

Explain the difference between flaccid and spastic paralysis in relation to the ligand-gated channel on the sarcolemma

If there is too much acetylcholine opening up the Na+ ligand gated channels, then sodium continues to rush in causing too many action potentials on the sarcolemma which causes spastic paralysis. If there is not enough acetylcholine to open up the Na+ ligand gated channels, then not much sodium will rush in and there would not be many action potentials on the sarcolemma causing flaccid paralysis.

Compare and contrast, in detail, what is occurring on a molecular and cellular level for immediate, short term, and long term energy needs of a muscle.

Immediate energy needs - 2 ADP, one to ATP, phosphagen system -- need the 2 enzymes, ATPShort term - glycolysisLong term - aerobic, Kreb's Cycle and ETC

What is the difference between a concentric and eccentric isotonic contraction?

In a concentric contraction, the muscle tension rises to meet the resistance then remains stable as the muscle shortens. During eccentric contraction, the muscle lengthens as the resistance becomes greater than the force the muscle is producing.

What is myoglobin? What is its function?

Is part of the sarcoplasm Myoglobin is synthesized inside muscle cells. It "stores" oxygen there for use at times of high metabolic demand.

Compare and contrast isotonic and isometric muscle contraction. Give some examples of each

Isometric muscle contraction: •develops tension without changing length •important in postural muscle function and antagonistic muscle joint stabilization Isotonic muscle contraction: •Same tension while shortening = concentric •Same tension while lengthening = eccentric

What does Nitric Oxide do to smooth muscle within a blood vessel?

It regulates vascular tone and blood flow by activating soluble guanylate cyclase (sGC) in the vascular smooth muscle, AND it controls mitochondrial O2 consumption by inhibiting cytochrome c oxidase.

What does recruitment mean in terms of muscle contraction?

Motor unit recruitment is the process by which different motor units are activated to produce a given level and type of muscle contraction.

Define Hypertrophy and Atrophy.

Muscle atrophy is a loss of muscle mass. Muscle hypertrophy is an increase of your muscle mass. Your muscle fibers get bigger or thicken. Muscle hypertrophy occurs due to an increase in the volume of your muscle cells.

What are two other names for a muscle fiber?

Muscle fiber = Myofiber = Myocyte = Muscle cell

Myofiber vs myofibril

Myofibril is a basic rod-like unit of a muscle fiber. Myofibril is composed of two types of myofilaments called thin and thick filaments.

What exactly is a cross bridge?

Myosin filament heads create cross bridges with actin. A cross-bridge refers to the attachment of myosin with actin within the muscle cell.

What protein is the thick filament made of?

Myosin: myosin binding protein-C, titin, myomesin, and obscurin

What does Norepinephrine do to smooth muscle within a blood vessel?

Norepinephrine (10"9 to 10"7 w/v) increases the duration of the bursts and shortens the interval between bursts after an initial period of continuous spike discharge.

What is another name for the plasma MEMBRANE of a myofiber?

Sarcolemma

What is the name given to the contractile unit of muscle?

Sarcomere

What is another name for the muscle cytoplasm?

Sarcoplasm

Describe, in detail, all the components of a neuromuscular junction (NMJ)

Synaptic knob: -is swollen end of nerve fiber (contains ACh) -It is the site for the transmission of action potential from nerve to the muscle. Junctional folds: -region of sarcolemma -•increases surface area for ACh receptors -•contains acetylcholinesterase that breaks down ACh and causes relaxation -They increase the overall surface of the postsynaptic membrane, and the AChRs clustered at high density on the crest of these folds, juxtaposed to the presynaptic active zones. Acetylcholine: -is used at the neuromuscular junctions, triggering the firing of motor neurons and affecting voluntary movements. -Nerve stimulation ceases and acetylcholinesterase removes ACh from nicotinic acetlycholine receptors (ionotropic). Stimulation of the muscle cell ceases. -Neurotransmitter (acetylcholine/ACh) released from nerve fiber stimulates muscle cell (~3,000 molecules per vesicle) Acetylcholine receptors: -is a neurotransmitter-gated ion channel that has been fine-tuned through evolution to transduce a chemical signal into an electrical signal with maximum efficiency and speed. Acetylcholinesterase: -It immediately breaks down or hydrolyzes acetylcholine (ACh), a naturally occurring neurotransmitter, into acetic acid and choline.

Describe the location of the T tubules, sarcoplasmic reticulum, and terminal cisternae. What is the function of each of these structures?

T tubules: -Located in the space between the two SR cisternae and the assembly of two SR and one T-tubule is called a triad. -maintain the SR calcium store under the tight control of membrane depolarization via the voltage sensor channel DHPR Sarcoplasmic reticulum: -Located within muscle cells -Regulation of excitation-contraction-coupling (ECC) and of intracellular calcium concentrations during contraction and relaxation. Terminal cisternae: -Located in the sarcoplasmic reticulum of a muscle fiber -Stores calcium and releases it when an action potential is generated, leading to muscle contraction

What affect does endurance training have?

These include increases in the mitochondrial content and respiratory capacity of the muscle fibers. Regularly performed endurance exercise induces major adaptations in skeletal muscle.

Explain, in detail, why an individual becomes rigid soon after death, but then days later, becomes floppy. Make sure to include the roles of ATP and calcium in your explanation

This is called Rigor Mortis. The muscles stiffen due to dying cells releasing from SR, promoting myosin binding and no ATP can be produced to detach them, so they stay bound.After multiple days, the proteins break down and die, so they lose their strength.

Compare and contrast the types of graded responses as discussed in class. Make sure to know "treppe".

Twitch: •Single, brief contraction (7-100 msecs .007-.1 seconds) •Not a normal muscle function •Length of twitch depends on type of muscle •Eye muscle fiber - 7.5 msec (fast) •Soleus 100 msec (slow) Treppe: (German for 'staircase') •Repeated stimulations immediately after relaxation phase •Thought: This is due to Calcium ions not being cleared away as quickly Wave summation: (summing of contractions) •The muscle does not completely return to a resting state and the effects are added Unfused (incomplete) tetanus: •Some relaxation occurs between contractions •Sustained, fluttering contractions of motor units •The results are summed into a smooth contraction Fused (complete) tetanus: •No evidence of relaxation before the following contractions •The result is an intense, sustained muscle contraction •Calcium is never reclaimed by the SR

Explain the phenomenon of "all or none" when describing muscle contraction.

When a motor unit receives a stimulus of sufficient intensity to bring forth a response, all the muscle fibres within the unit will contract at the same time, and to the maximum possible extent.

When smooth muscle contracts in blood vessels, what happens to the size of the lumen? What happens to blood pressure at that area?

When smooth muscle contracts in blood vessels what happens to the size of the lumen? Contraction of the smooth muscle cells constricts the lumen of the arteriole, increasing vascular resistance and reducing the flow of blood into capillary beds. The arterioles generate the largest resistance to blood flow in the circulatory system. makes the lumen narrower and increasing blood pressure.

Describe the number and location of nuclei in a skeletal muscle fiber.

With an average diameter of 10 μm, nuclei are normally found at the PERIPHERY of the myofiber, just below the plasma membrane. Skeletal muscle cells are long, cylindrical, and striated. They are multi-nucleated meaning that they have more than one nucleus.

What is an aponeurosis? Where are some regions in the human body might you find one? How does an aponeurosis differ from a tendon?

a. Aponeuroses = sheet-like structure b. Achilles tendon, palm of hands, & skull c. An aponeurosis is made of layers of delicate, thin sheaths. Tendons, in contrast, are tough and rope-like.

Label the 3 connective tissue wrappings of a skeletal muscle

a. Epimysium --> surrounds ALL fascicles i. Exterior collagen layer. ii. Connected to deep fascia. iii. Separates muscle from surrounding tissues. b. Perimysium --> around A fascicle i. Contains blood vessel and nerve supply to fascicles. c. Endomysium --> around INDIVIDUAL muscle fibers i. Contains capillaries and nerve fibers contacting muscle cells. ii. Contains myosatellite cells (stem cells) that repair damage.

List AND describe the functions of skeletal muscles

a. Movement b. Posture c. Supports soft tissue. d. Guards entrances and exits. e. Provides heat/maintains body temperature. f. Storage of minerals

Compare and contrast skeletal muscle, cardiac muscle, and smooth muscle making sure to include the following in your comparison. This question may be more appropriate for the lab portion of this course:

a. Multinucleated: SkeletalOne Nucleus: Cardiac & Smooth b. Skeletal: Under SarcolemmaCardiac: Center of CellSmooth: Center of Cell c. Striated: Cardiac & SkeletalNon-Striated: Smooth d. Voluntary: SkeletalInvoluntary: Cardiac & Smooth e. Division: Smooth & limited Cardiac f. Intercalated Discs: Cardiac g. Skeletal: Movement, Posture, Guard Entrance & Exits, Store Minerals, Support Soft Tissue, & Maintain Body TempCardiac: Pump BloodSmooth: Change Volume of Organ h. Cardiac: HeartSmooth: Hollow OrgansSkeletal: Attached to bones

List AND describe the characteristics of skeletal muscle

a. Responsiveness (excitability) --To chemical signals, stretch and electrical changes across the plasma membrane b. Conductivity i. Local electrical change triggers a wave of excitation that travels along the muscle fiber. c. Contractility --> Shortens when stimulated. d. Extensibility --> Capable of being stretched. e. Elasticity --> Returns to its original resting length after being stretched.