PVCC BIO 201 EXAM 3

4 functional characteristics of muscle?

E-CEE

Excitability- responds to stimuli

Contractility- can shorten

Extensibility- can extend

Elasticity- can recoil to resting length

Epimysium

Outermost connective sheath- surrounds bundles of fascicles

Perimysium

Middle connective layer, surrounds individual fascicle

Endomysium

Innermost connective layer, surrounds individual muscle cell

1. Epimysium

2. Perimysium

3. Endomysium

Fascicle

Made of multiple muscle cells

Sarcolemma

Cell membrane of muscle cells

Myofibril

A strand of the muscle cell, has actin and myosin

Muscle fiber

One muscle cell- elongated and multi-nucleate

Advantage of the structure of -mysium and tendons?

All continuous, transfers force more efficiently to bone

How does tendon elasticity convert kinetic energy—> potential energy?

Tendons absorb kinetic energy and store it, turning it into potential energy. This allows for a rapid recoil if needed.

Glycosomes

Granules of stored glycogen, stored in muscle cells to provide fast energy

Glycogen

Made of many glucose molecules- glucose can be converted to ATP

Myoglobin

Carries oxygen

How does the body create large muscle cells?

Many cells fuse during development, creates large cell

How does body coordinate muscles?

The sarcolemma is electrically excitable like a nerve cell, allows for fast communication

How does body distribute gene products in a large cell

Many nuclei = shorter distances for gene products to be distributed

How do muscle cells contract?

Using actin+myosin and ATP

A.

Thick filament (myosin)

B.

Thin filament (actin)

C.

Z disk

D.

H zone

E.

M line

F.

I band (on either side of A band)

G.

A band

A.

Myosin

B.

Elastic filaments

C.

Actin

D.

Sarcomere

Describe how the myosin binding sites are blocked in muscle’s resting state

The troponin complex blocks binding sites on actin, the long tropomyosin protein must be moved by troponin for myosin to bind to actin

What is the neurotransmitter molecule released by motor neuron?

Acetylcholine

What causes the actin and myosin to relax?

The ATP binds to myosin, which releases the myosin from the myosin binding sites (on the actin)

What causes a ligand gated channel to open?

The ligand (acting molecule) binds to the receptor channel and opens it

What causes a voltage gated channel to open?

Voltage of the cell becomes positive, which opens the channel

Describe distribution of Na+ and K+ inside vs outside cell, before and after action potential

The cell has lower Na+ and higher K+, and the outside of the cell has higher Na+ and lower K+. When triggered by an action potential, Na+ flows into the cell and creates a positive charge (Depolarizes). Then K+ leaves the cell to return the cell to negative charge.

Where is acetylcholine contained?

In synaptic vesicles of the nerve cell

Describe the 3 states of the voltage gated sodium channel

1. Rest = closed

2. Open = due to positive voltage

3. Inactivated = after opening, channel closes by itself and recovers, will cycle back to resting

How does calcium affect acetylcholine at neuromuscular junction?

Increase in calcium causes the synaptic vesicles to exocytose ACh onto muscle cell. This calcium enters the nerve cell through voltage gated calcium channels (activated by action potential)

Purpose of acetylcholinesterase

Acetylcholinesterase destroys acetylcholine so that muscle can relax and is not re-triggered.

Effect of acetylcholine on muscle receptors

ACh binds to the ACh receptor (ligand gated) and opens the channel. This allows Na+ to flow into the cell and K+ to flow out of the cell. This starts the process of creating positive charge in the cell, and triggers voltage gated sodium channels to open and initiate action potential.

What is the job of the T tubule?

Relay action potential signal to sarcoplasmic reticulum, causes release of calcium ion into the muscle cell

Job of sarcoplasmic reticulum

Stores and releases calcium

What do the calcium ions in the muscle cell bind to?

Calcium ions bind to troponin, moving tropomyosin, allowing the myosin to bind to actin

Sequence of events that causes muscle contractions

1. Action potential arrives at neuromuscular junction

2. Nerve cell releases acetylcholine, which triggers voltage gated sodium channels, creating action potential along surface of sarcolemma

3. Action potential descends through T tubules into the muscle cell

4. T tubules signal sarcoplasmic reticulum to release calcium ions

5. Calcium binds to troponin complex, which moves tropomyosin from binding sites, allowing actin and myosin to interact (contraction)

6. Calcium is removed from the sarcoplasm and troponin complex blocks binding sites, stops muscle contraction

Motor unit

Consists of all muscles stimulated by a single motor neuron, small motor units allow for finer movements. More motor units allows for larger stronger movements

Isotonic vs isometric contraction

Isotonic= tension develops, load is moved, muscle fibers shorten

Isometric= tension develops but load doesn’t move, muscle fibers stay the same length

What is a muscle twitch?

Response of motor unit to single action potential. Faster twitch = greater accuracy but lesser strength

What occurs during muscle’s latent period?

latent period = delay between action potential and tension observed in muscle

On molecular level, calcium is diffusing out of SR, binding to tropinin complex, and moving tropomyosin

2 ways to change muscle tension response

1. Changing frequency of nerve stimulation, multiple action potential = stronger contraction

2. Changing strength of stimulus, more intense stimulus causes other motor units to contract (recruitment)

Describe recruitment

Over time more/larger motor units are being activated due to stimulus gaining strength. Small motor units are recruited before larger ones

Describe summation

Changing frequency, but not strength, of nerve stimulation. Treppe effect = repeated equal stimuli produce progressive increase in tension generated. Caused by accumulation of calcium ions within muscle fiber. Repeated stimuli = not enough time for cell to move all calcium back to SR

Duration of energy from ATP vs glycogen vs mitochondria+oxygen

ATP= 4 to 6 seconds

Glycogen= broken down into glucose, 30-40 seconds

Mitochondria= if oxygen present, lasts for hours

Job of creatine kinase in muscle cell

Creatine Kinase is an enzyme that transfers phosphate to ADP to create ATP, catalyzes the reaction of creatine phosphate + ADP → creatine + ATP

Slow twitch vs fast twitch muscle fibers

Slow twitch: oxidative, slow contractions but resistant to fatigue. High oxygen demand (<mitochondria), thinner and weaker muscles

Fast twitch: glycolytic, rapid contractions and fatigues easily. No oxygen used (>mitochondria) and primarily anaerobic, larger and stronger muscles

Fast oxidative/glycolytic fibers

Intermediate type of muscle fiber, intermediate properties/strength/size

smooth muscle location and junctions

Smooth muscle lines the body’s hollow organs, excluding the heart

Use gap junctions that allow electrical signals to pass between cells

Purpose of varicosities

Varicosities = nerve endings that secrete hormones onto muscles to control contractions. Hormones are released into diffuse junctions. Effect can be short or long lasting (hours)

Single unit smooth muscle vs multiunit smooth muscle

single unit smooth muscle: waves of contraction in sheets of tissue, muscles connected by gap junctions, contracts as a single unit. In hollow organs

Multiunit smooth muscle: local control of small motor units, fibers act independently, few gap junctions. In iris, arrector pili, airways

In smooth muscle, what do calcium ions released from sarcoplasmic reticulum bind to?

In smooth muscle, calcium ions bind to calmodulin

Process of actin and myosin movement in skeletal muscle

Calcium ions bind to troponin, moved the tropomyosin off of the myosin binding site. Myosin heads bind to site on actin strand and an ADP molecule is released. After pulling the myosin filament, the myosin head releases from actin, binds to ATP, and resets potential energy using ATP. Cycle can now repeat with myosin binding with actin again.

How do muscles move quickly despite short length of sarcomere?

Multiple sarcomeres end to end amplify small movements

How do muscles generate high force despite small sarcomere size?

Multiple sarcomeres stacked top to bottom create stronger forces then an individual sarcomere

Muscles and job of rotator cuff

Supraspinatus

Infraspinatus

Teres minor

Subscapularis

Form a cuff that holds head of humerus in glenoid cavity

describe compartment syndrome

Compartment syndrome = inflammation of the fascia

This inflammation creates pressure and compresses muscles,nerves,bloodvessels

Can cause ischemia (poor blood flow). Treated by cutting the muscle to relieve pressure

Describe ALS

Motor neurons progressively die. Muscles and brain neurons are unaffected. Causes paralysis

Describe myasthenia gravis

Antibodies attack acetylcholine receptors at neuromuscular junction, causes them to be unresponsive to ACh. Presents as muscle weakness, drooping eyelids, and rapid muscle fatigue

Describe Duchenne muscular dystrophy

Caused by defective dystrophin protein. Dystrophin acts as a shock absorber and without proper function the muscle cells destroy their own cell membranes when contracting. Kills muscle cells

Describe flaccid paralysis due to toxins that block calcium channels in motor neurons

If calcium channels in motor neurons are blocked, the trigger to release ACh isn’t reached and muscle won’t comtract

Ryanodine receptor

Opens channel that allows calcium ions out of sarcoplasmic reticulum. Located at junction of T tubule and SR

Describe flaccid paralysis due to failure of choline re-uptake

Without re-uptake of choline into motor neuron, it can’t be recycled back into ACh and nerve terminal runs out of neurotransmitter

Hyper- vs hypo-kalemia

Hyperkalemia= elevated extracellular potassium levels

Hypokalemia= decreased extracellular potassium levels

Both cause poor excitability of T tubule due to charge imbalance

Describe acetylcholinesterase

Inactivates ACh. When defective/destroyed, causes rigid paralysis due to overactivity of ACh

Describe calcium pump SERCA

SERCA=sarcoplasmic reticulum calcium transport ATPase

Found only in skeletal and cardiac muscles, when damaged leads to high calcium events/excessive muscle contractions and eventually rigid paralysis

Describe Parkinson’s disease symptoms

Continuous shaking of the limbs but no muscle fatigue. Also causes specific gait when walking

Describe clonus

Rhythmic pattern of contractions, 3-7 per second, due to alternating stretching-unloading of muscle spindles in spastic muscle

Describe Guillain Barre syndrome

Caused when antibodies attack a virus and myelin is collateral damage. Symptoms include loss of sensation, unsteady walking, difficulty with face/throat movements and difficulty breathing

Muscle insertion point vs muscle origin

Muscle insertion= end that moved when contracting

Muscle origin= end that doesn’t move during contraction

Forearm flexion muscles and opposing muscle

Flexion =Biceps, brachioradialis, brachialis

Opposition =triceps brachii

Muscle action and antagonist of pectoralis major

Flexes the arm

Antagonist = latissimus dorsi

Muscle action and antagonist of the deltoid

Abducts the arm (lifts away from body)

Antagonist = teres major

Agonist

Prime mover in muscle action

Synergist vs antagonist

Synergist =aids prime mover, can modify direction of movement

Antagonist =opposes direction of prime muscle movement

Fixator

Holds bones in place

Which muscles close the jaw?

Temporalis and masseter

Genioglossus vs hypoglossus vs syloglossus muscle

Genioglossus =protracts and retracts tongue

Hypoglossus =depresses tongue

Syloglossus =retracts and elevates tongue

Iliocostalis and longissimus muscle function (same for both)

Extends and laterally flexes vertebral column

Spinalis movement

Extends vertebral column

External intercostals movement

Elevates rib cage during inspiration

Rectus abdominis movement

Compresses abdomen

Levator ani function

Maintains position of pelvic viscera

Which muscles protract the scapula?

serratus anterior, pectoralis minor, pectoralis major (all synergists)

Which muscles retract the scapula?

Trapezius and rhomboids

Describe structure of trapezius

Has 3 heads that can activate independently, acts as its own antagonist, can raise or lower scapula

Afferent vs Efferent signals

Afferent =input,towards the brain

Efferent =output, towards the body

Think cAuse and Effect

How does spinal fluid differ from blood?

Contains no red blood cells and has low protein content

Significance of Louveau finding

Discovered antibodies in brain

Could cause problems with inflammation leading to multiple sclerosis and alzheimers, but knowing the cause creates opportunities for a cure

Job of blood brain barrier

Protects brain from cells, large proteins, and amino acids that would kill neuronal cells

Structures in CNS

Brain and spinal cord

4 types of glial cells in CNS

Astrocytes, microglia, ependymal cells, ogliodendrocytes

AMEO

2 types of glial cells in PNS

Satellite cells, schwann cells