PSIO 201 Exam 3

What are the functions of the muscular system?

• Locomotion

• Posture and body position

• Control of body openings/passages

• Regulation of body temp

• Metabolism and endocrine functions

Is skeletal muscle contraction voluntary or involuntary?

Voluntary; requires nervous system input

*Some skeletal muscles activate automatically (diaphragm)

How do muscles work with bones to move?

Muscles pull on bones

Define origin and insertion

Origin: place where muscle starts on a bone

Insertion: place where muscle ends on a bone

• They must be connected across a joint

Define flexion and extension

Flexion: decreasing angle at a joint

Extension: increasing angle at a joint

Define abduction and adduction (and DO IT!)

Abduction: movement away from midline (you’re getting abducted by aliens!)

Adduction: movement toward the midline (…and you’re being returned :))

Define pronation and supination (DO IT TOO!)

Pronation: Palm facing down

Supination: palm facing up

What is the movement around an axis?

Rotation

What is an agonist?

(aka prime movers)
the principal muscle in movement

What is an antagonist?

Muscle that opposes the movement of the agonist; return to initial position

What is a synergist?

Muscles that assist the agonist; additional force, stability, and control

What is a fixator?

A specific type of synergist; Stabilizer muscle prevents any unwanted movement

• Inability to fixate muscles → limits range of motion

What are the basic fxns of muscle?

Generate tension (via contraction)

What is reverse muscle action?

The ORIGIN moving toward the insertion (i.e. pull ups)

What is mechanical advantage? What is the tradeoff?

The most efficient a muscle can move based on the effort:load ratio

• Greater distance between effort and fulcrum [than load and fulcrum]

Tradeoff: same force across a longer distance

What is the “fulcrum”, “load”, and “effort” in the body?

Fulcrum: joints

Effort: tension in muscle

Load: weight

What is the formula for a first class lever?

Give an example

e F l

• Nodding yes

  • E: neck muscles pulling down

  • F: atlanto-occipital joint

  • L: mass of the head

*Seesaw

What is the formula for a second class lever?

Give an example

f L e

• Standing on tip toes

  • F: ball of toes

  • L: weight of body on foot

  • E: body mass

*Wheelbarrow

What is the formula for a third class lever?
Give an example

f E l

• Biceps curl

  • F: Elbow

  • E: Biceps pulling on radius

  • L: weight of hand

What is hyperplasia and hypertrophy?

Hyperplasia: increase in cell NUMBER

• muscle dev. before birth

Hypertrophy: increase in cell SIZE

• muscle dev. after birth

What do tendons do?

Attach muscle to bone

What is the C.T. surrounding muscles? What is inside the muscle?

Epimysium (collagen CT)

Fasicles

What are fascicles? What C.T. surrounds them?

• Bundles of muscle fibers

• Perimysium (collagen CT

What CT surrounds muscle fibers? What are membrane are muscle fibers covered in? 

• Endomysium

• Sarcolemma

  • (Both collagen CT)

What are myocytes made of?

Myofibrils

• Made up of primarily actin and myosin

What characteristics do perimysium, endomysium, and epimysium have that are important for the muscle?

• Transmits generated force where the muscle attaches

• Spring-like properties aiding in movement efficiency

What is the myotendinous junction?

(White part)

CT that pulls on the bone through which muscle generates force

• repetitive movements = repetitive stressors on these junctions

What separates muscle compartments?

Fascia: a connective tissue border

What is the superficial fascia?

• Network of CT all over the body

• Collagen & elastin

• “Liquid crystal”-like: can change between liquid and solid

• Receptors (pain and mechano)

  • Pain: 5-10x more pain receptors in fascia than in muscle

  • Mechano: body’s location in 3D space

• Provides stability in body movement

True or false: the contraction of skeletal muscle leads to release hormones into the blood stream

True

True or false: flexing the forearm via the biceps brachii is an example of a second class lever

False; that is a third class lever

What are the three units of subcellular organization?

1. Conduction of electrical signals

   1. Via sarcolemma + T-tubules

2. Control

   1. Sarcoplasmic reticulum

3. Contraction

   1. Myofibrils

      1. Actin

      2. Myosin

What is the function of the t-tubules?

Allows for the action potential to reach the interior of the muscle cell

What is the function of the sarcoplasmic reticulum?

Stores Ca+

What makes up the “triad”?

1. T-tubules

2. Sarcoplasmic reticulum

3. terminal cisterns

Label this diagram

*Missing M-line and Zone of Overlap

What effects does contraction have on the sarcomere?

• Z-lines are brought closer together

• H zone is gone

• I band decreases

What part of the sarcomere does nebulin form?

Length of the thin filament

What part of the sarcomere does α-actinin form?

The Z-line; anchors thin filaments

What part of the sarcomere does titin form?

Spring-like protein, connects z-discs to the M line

What part of the sarcomere does myomesin form?

A chain in the middle of the sarcomere; links adjacent thick filaments

What does dystrophin do for the sarcomere?

Connects it to the sarcolemma → CT → tendon → bone

How can myosin bind to actin?

Troponin binds to Ca+ which moves tropomyosin away from actin’s binding site. Myosin heads bind here. 

What are the components of myosin?

• Myosin heavy chain

  • Has a head and tail

• Actin binding site

• ATPase site

What is a crossbridge? Where does it form?

Forms in the Zone of Overlap; where actin and myosin bind

How do neurons and muscle cells generate electrical signals?

Controlling movement of ions across their membranes

What causes depolarization in the myocyte?

Influx of Na+ ions

What neurotransmitter is released inside the sarcolemma? And what enzyme get rids of it?

• Acetylcholine (ACh)

• acetylcholinesterase (AChE) to cease action potentials

What is the specialized region on the sarcolemma for the NMJ?

Motor end plate

What does deep fascia do?

Separates muscle compartments

What does superficial fascia do?

Anchors muscle to skin

What are the steps of crossbridging?

1. Readying of the Myosin Head

   1. ATP hydrolysis separates

   2. Leads to cocking of the head

2. Binding myosin and actin

   1. If calcium is present

3. “Power stroke” - myosin pulls actin

   1. Phosphate pops off the myosin head

4. Detachment - requires ATP (binds to rigor complex)

What causes rigor mortis?

Without ATP generation, you cannot detach myosin and actin

What makes up the neuromuscular junction?

• Axon terminal

• Synaptic cleft

• Motor end plate 

• Sarcolemma

When the action potential reaches the axon terminal, what triggers an influx of calcium?

Calcium voltage gate

What does an influx of calcium do?

Encourages the synaptic vessels to fuse with the axon terminal / release ACh into the synaptic cleft

What does ACh bind to on the motor end plate?

Nicotinic ACh receptors

When the nicotinic ACh receptors bind with ACh, what happens?

Influx of Na+ into the muscle cell

What does an influx of Na trigger?

It triggers the voltage-sensitive protein on the t-tubules

What does the voltage sensitive protein do?

Opens the Ryanodine receptor (cap) of the sarcoplasmic reticulum

When the Ryanodine receptor is ‘opened’, what happens?

The intracellular concentration of Ca+ increases

• ^[Ca]i

What happens when the intracellular concentration of Ca+ increases?

Calcium binds to troponin… moving tropomyosin… myosin binds to actin

What makes up a motor unit?

Motor neuron + muscle fibers it innervates

What is the difference between a large v.s. small motor unit?

The # of fibers a neuron innervates (controls)

What does the calcium pump (on the SR) do?

Cleans up calcium, pumps it back into the sarcoplasmic reticulum

What is the function of the small motor units?

aka slow twitch fibers, fine motor control

What is the function of the intermediate motor units?

fast twitch fibers; moderate force and endurance activities

What is the function of the large motor units?

Fast twitch fibers, contract powerfully and fatigue quickly

What characteristics of muscle contraction do motor units determine?

Size & force

Speed is determined by ___

muscle fiber types

What is temporal summation?

Increasing the frequency of nerve impulses to a muscle; T = time

What is spatial summation?

Allows for more muscle fibers to contract; S = surface area

What is isometric contraction?

Muscle generates tension w/o changing the length

What is isotonic contraction?

Muscle changes size while contraction?

What are the two different types of isotonic contraction?

Eccentric: lengthens under contraction (lowering a dumbbell under control)

Concentric: shortens under contraction (lifting a dumbbell)

What begins the process of relaxation?

• ACh esterase breaks down ACh

• Ca ATPase cleans up all of the Ca

• Allow titin to return to the original length

What does the liver do for muscle energetics?

Chains together glucose to make glycogen: for energy storage

• Gets first dibs on substances

What are the two types of metabolism?

1. Aerobic metabolism

2. Anaerobic metabolism

Describe aerobic metabolism

• Glucose breaks down into two 3-carbon molecules (pyruvate)

• One pyruvate heads to the mitochondria to generate lots of ATP

  • Oxygen is needed in the mitochondria

Describe anaerobic metabolism

• Glucose breaks down into two 3-carbon molecules (pyruvate)

  • The other pyruvate forms lactate → leaves cell, goes into blood

What is the phosphagen system?

Quickest way to make ATP; only lasts 15 seconds

• Creatine phosphate: stores energy within the bonds

• Hydrolysis of ATP

What is the timeline for ATP usage in high intensity activity?

1. ATP-Creatine phosphate (15 seconds)

2. Glycolysis (1-2 min)

3. Anaerobic metabolism (prolonged, lower intensity activity ~40 min)

What are the systems involved in fatigue?

Psychological, nervous system, muscular system

What are some of the possible causes of fatigue?

1. Depletion of ATP & CP

2. Glycogen depletion

3. Metabolic acid production

   1. H+ from hydrolysis

4. Phosphate levels

5. Ion imbalances

What happens when you load your blood with glucose?

The pancreas releases insulin

• Binds to receptors of the skeletal muscle

  • Increases glucose transporters to the sarcoplasm

*Exercise also does this!

What does creatine kinase do?

Takes the phosphate from creatine phosphate and attaches it to ADP → ATP

Pyruvate + ___ = latate

H+ ion from hydrolyzed ATP

What process occurs as a product of oxygen debt?

The Cori Cycle

Briefly describe the Cori Cycle

Glucose undergoes glycolysis in the muscles, resulting in the production of lactate

The liver then takes lactate and forms glucose through gluconeogenesis

What is the purpose of the Cori Cycle?

• Restore glucose/glycogen

• Resynthesize creatine phosphate

• Replace oxygen removed from myoglobin

What is VO2 max?

Max oxygen consumption during exercise; associated with longevity

What are the three types of muscle contraction?

1. Eccentric: muscle lengthening during contraction (more damage)

2. Concentric: muscle shortening during contraction

3. Isometric: No shortening/lengthening

What are the three types of motor units?

1. Slow oxidative fibers (type I)

2. Fast oxidative glycolytic (type IIa)

3. Fast glycolytic fibers (type IIx)

What are the characteristics of slow oxidative fibers?

• Slow speed

• Small amount of force

• High resistance to fatigue

• Posture, marathon, etc.

• High in mitochondria

What are the characteristics of fast oxidative glycolytic fibers?

• Fast speed

• Medium amount of force

• Medium resistance to fatigue

• Walk, high rep strength

What are the characteristics of fast glycolytic fibers?

• Fast speed

• High force

• Low resistance to fatigue

• Sprinting, power lifting

• Low in mitochondria

Temporal Summation

Increase frequency of electrical stimuli

Spatial summation

Recruiting more motor units → more tension

Briefly describe the length-tension relationship

Bigger zone of overlap = more tension

• BUT too much overlap = bad

What is power?

Speed * Force

(that a muscle generates)