Test 2

cell membrane

separates inside of the cell from the outside fluid.

cytosol

inside of cells: intraacellula

extracelluar

outside of cell: interstitial

what does the cell membrane do?

olutesallows for the concentration of electrolytes & and to be different inside and outside.

* Ka+ & Na+

what kind permeability is the cell membrane?

selectively permeable

what varies in cells selectively?

different transport mechanisms.

passive transport

no energy needed

active transport

requires energy to move from low to high concentration.

diffusion( across membrane)

random motion of ions and molecules down their concentration gradient. ( Passive ) high → low

carrier mediated transport( across membrane)

bind specific substrate

can be passive or active transport.

requires transport protein.

how do charged ions and molecules diffuse?

diffuse based on electro-chemical gradient. ( all charged particles)

chemical and electrical concentration gradients are separate driving forces.

what are some examples of diffusion of body fluids?

O2: lungs→blood→ interstitial space→ cells

CO2: cells→interstitial space→ blood→ lungs

H2O: across epithelium of digestive tract→ body tissues

what is the lipid bilayer permeable to and not?\`

yes: O2, CO2, most hydrophobic molecules.

not: large and hydrophilic molecules.

Muscle tissue

Specialized for contraction

Skeletal

Cardiac

Smooth

Skeletal

Attached to bone

Striated, voluntary

Cardiac

Striated, involuntary

Smooth

Lines hollow organs

Non striated, involuntary

Where is muscle attached to?

Attached to bone by tendon

Synergistic muscles

Work together

Antagonistic muscles

Flexors and extensors

Endomysium

Covers individual muscle fibers

Perimysium

Sheathes bundles of muscle fibers

Muscle fascicules

Contain blood vessels and nerves

Epimysium

Surrounds a muscle

Contain blood vessels an nerves

Deep fascia

Wraps groups of cooperating muscles together

Muscle cell= muscle fiber

Each muscle is long as the muscle

How a muscle cell if formed

During embryogenesis by end-to-end fusion of uni-nuclear myoblasts

Where new skeletal muscle come from

Stem cells called satellite cells

Function of skeletal muscle tissue

Move/ stabilizes the position of the Skelton

Guards entrances/exits to digestive tract

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Structure of skeletal muscle cell

Myofibrils

Sarcoplasm ( muscle cell cytoplasm)

Sarcolemma( cell membrane)

Sarcoplasmic reticulum

Has large quantities of protein filaments/ myofilaments

* actin
* Myosin

Actin( myofilament)

Thin filaments

Myosin ( myofilament)

Thick filaments

Myofibrils

Thousands of sarcomeres

Bundles of myofilaments

Anchored to inner surface of Sarcolemma at either end of cell

Sarcolemma( muscle cell membrane)

Conducts action potential ( excitable) deep into cell

Tubes extend to cells at 90 degrees to cell surface

T-tubules

Very close with SR

Sarcoplasmic reticulum

Stores a lot Ca+2 needed for muscle contraction

Tubular network

* terminal cisternae form triads w/ t-tubules

Sarcomeres

Repeating units of myofilaments in myofibril

Shorten during contraction

Striated sarcomeres

I bands= LIght = thIn

A bands = dArk= thick mostly, w/ some overlap w/ thin

Z disk= border b/w sarcomeres

Levels of functional organization in skeletal muscle

* skeletal muscle


* Muscle fascicle
* Muscle fiber
* Myofibril
* Sarcomere

Muscle contraction

Interactions b/w thin & thick filaments shortening sarcomere

How do thin & thick filaments slide across each other ?

Short projections form cross bridges which change shape pulling actin past myosin.

How do cross bridges change shape?

They use ATP to change shape and pull actin

Convert chemical energy to mechanical energy

Myosin molecules

Have elongated tails & globular head

Head forms cross bridges during contraction

Prevents interaction b/w myosin head and actin during rest

Tropomyosin

* Strands attach to active site by troponin

What actin is made up of

Twisted strands of 2 rows of individual globular actin molecules w/ active site which can attach to myosin head

What ATP does for myosin head

Provides energy for movement of head

* chemical → mechanical energy

Role of Ca+2

Concentration controls sarcomeres contraction

Low=rest

Action potential= contraction

* voltage gated Ca+2 channel of SR open
* Release Ca+2 into sarcoplasm around sarcomere

How does Ca+2 affect troponin

Causes it to change shape and pull tropomyosin off active sites And Ca+2 falls

Motor neuron (voluntary)

Nerve cell that controls muscle contraction

Neuromuscular junction

Synapse b/w motor neuron & muscle cell

Action potential initiated in moor neuron…

Travels thru motor neuron and arrives at synaptic terminal

ACh

Allows for contraction

What does ACh do when releases from motor neuron

Diffuses across synaptic gap, binds to receptors on chemically gated Na+ channels in muscles membrane

Sodium ions flow into muscles cells and do what?

Depolarize muscle cells membrane and star action potential in muscle cell

Contraction cycle

Ca+2 binds troponin moving tropomyosin

Myosin head attached to actin

Heads pull actin

Myosin head detach when ATP binds

How Ca+2 returns to resting level

AP depolarization ends

Voltages gated Ca+2 channels in SR close( diffusion of Ca+2 stops)

How is Ca+2 transported out of the sarcoplasm

Across Sarcolemma to outside of cell

Across SR membrane into SR( sarcoplasmic reticulum)

Requires ATP for active transport

Duration of stimulation depends on

Continued release of ACh and AP in muscle fibers

The amount of Ca+2- needs to return to resting level

ATP availability- needs ATP to construe contraction

Acetylcholine Esterase (AChE)

Rapidly break down ACh

Located in synaptic gap

Contraction end when

AP stop

ACh is broken down

Na+ ion influx stops

Ca+2 return to resting level

Muscular system disorders

Affect coordination and control of muscle contraction

* blockage/ interference of ACh
* Interference of AChE

Tension

Sliding of actin and myosin fibers, shorten causing the muscle to shorten.

What does tension depend on

Individual tension in muscle cells during contraction

\# of muscle cells that contract.

Fiber shortening

Sarcomeres shorten → muscle cells shorten→ tension

Why does tension vary in individual muscle fibers

Length tension relationship

Frequency of stimulation by motor neuron

Why does tension produced by entire muscle vary

\# of muscle cells receiving nerve stimulation leading to contraction.

What does the amount of tension depend on

\# of cross bridges formed

* degree of overlap of actin and myosin

What is a twitch?

cycle of contraction produced by single AP in muscle cell

Latent phase

AP occurs

No contraction untutored Ca+2 is releases form SR

Contraction phase

Tension rises to peak

* Ca+2 moves tropomyosin off actin active sites
* Cross bridges form

Relaxation phase

Actin active sites covered by tropomyosin

Ca+2 goes back to SR

No cross bridges

Tension phases

Latent phase

Contraction phase

Relaxation phase

What do most muscular activities involve ?

Sustained muscular contraction

What do sustained muscular contraction produce?

High frequency of AP- muscle cell

Response to high frequency - motor neuron

Summation

Summation

Adding more Ca+2 = more cross bridges

Leads to more tension

Tetanus

Sustained contraction (constant tension production )

What does Clostridium tetanus bacteria cause

Tetanus disease

High frequency of actin potential in motor neurons

Complete tetanus

Maximum cross bridges formed = max tension production

No relaxation phase

Treppe

Calcium release and calcium transport equal each other

Wave summation

Successive stimuli occur BEFORE relaxation phase is complete

Incomplete tetanus

Tension production rises to peak and relaxation peridots are short

All muscle fibers reinvented by…

One motor neuron

Amount of tensio produced is determined by

Number of motor units activated

Small motor until

Precise control

* Small amount of muscle fibers innervated

Large motor neuron

Gross movement control

* large number of cells innervated

Muscle tone

Resting tension in skeletal muscle

* some motor neuron are always active

Isotonic

Tension rises, length of muscle changes

* concentric
* Eccentric

Concentric

Muscle tension exceeds resistance and muscle shortens

Eccentric

Peak tension developed is less than the resistances, muscle elongates

Isometric

Tension rises, length of muscle remains of constant

Tension produced doesn’t exceed resistance

What happens in isometric contraction?

Muscle doesn’t shorten but individual muscle fibers shorten

How does a muscle return to resting length

Recoiled in elastic components

Contraction ofc opposing muscle groups

Gravity

Muscle contraction requires large amount of ATP

Muscle cells stores enough ATP until more can be generated

How long does the ATP and CP (creatine phosphate) reserve last?

15 seconds

Where does the extra ATP made go ?

Excess ATP stores glucose in glycogen which creates CP

* Transfers high energy phosphate to creatine for storage

How do CP reserves convert stored energy into ATP?

ADP → ATP

How is ATP generated?

Aerobic cellular respiration in mitochondria: citric acid cycle, ETC

O2 in → CO2 out

What do resting muscle fiber rely on?

Aerobic metabolism of FATTY ACIDS to generate ATP

How not fatty acids make ATP

They are absorbed from circulation

Break down to 2 C of acetylene CoA→ citric acid cycle

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Contracting muscle fiber rely on what?

Aerobic and anaerobic metabolism of glucose which both depend on intensity of muscle contraction.

Pyruvate metabolism- anaerobic

No oxygen= pyruvate converted to lactic acid Which recycles cofactors needed by glycolic enzymes

How much of the ATP can be met by mitochondria

1/3