False

Muscles are the largest group of tissues in the body

False

Skeletal muscle is 40% of body by wt.

False

They are voluntary muscles that you consciously control

1. skeletal muscles

2. bones

1. the muscle fiber is a Large cell

2. they are 10-100 micrometers in diameter

3. they are very long and extend the length of hte muscle

4. they are formed by the fusion of smaller cells during embryonic dev.

5. they are multinucleate

6. A single motor neuron innervates one muscle fiber

False

Muscle fibers are made up of myofibrils

* muscle--muscle fiber--myofibril**

The muscle is made up of muscle fiber (muscle cell) and muscle fiber is made up of myofibrils

False

Skeletal muscle is striated

1.Dark band =

2. Light band =

1. myosin and overlap of myosin and actin

2. actin and Z line

a. it is the attachment site for actin

b. made up of filamentous proteins

False

Sacomere is the functional unit of the myofibril

TF thick filament = actin and

thin filament = myosin

False

thick filament = myosin

thin filament = actin

Myosin has __ subunits

Each subunit composes of a_______________ head

1. 2

2. golfclub-shaped

False

It only has 2 active sites

1. actin binding site: binds actin

2. myosin ATPase binding site: binds and cleaves ATP

False

Thin filament includes:

actin

tropomyosin

troponin

a. actin molecules (which are globular proteins)

b. binding site for myosin head

False

it is a thin filament

What are the is the func. of tropomyosin?

a. acts as a regulatory protein for muscle contraction

b. covers binding sites on actin

False

It only wraps around the actin helix

1. Troponin T

2. Troponin I

3. Troponin C

False

Troponin T binds to tropomyosin

False

During muscle relaxation Ca2++ is low

During muscle contraction Ca2++ is high

False

When troponin C binds to calcium, this stimulates the T2 complex to undergo a conformational changes which uncovers the actin binding site

False

When ATP is bound to myosin head, it causes the head to detach from the actin binding site

1. intracellular Ca2++ is high

2. Troponin C binds to Ca2++

3. This causes T2 complex to undergo a conformational change which will uncover the actin binding site

4. myosin head will now bind to the actin binding site

5.This will trigger a conformational change in myosin causing the head to tilt forward (ie power stroke)

6. Tilting of the head releases ADP

7. ATP will now bind to the myosin head

8. It will cause the myosin head to detach from the actin binding site

9. ATP will then be cleaved to ADP by ATpase of the myosin, this will cause the myosin head to return to its orginal (nontilted) form

10. When ATP is cleaved energy is put back into the system which can be used for the next power stroke

False

it can occur if only Ca2++ is present

False

During rigor mortis, existing ATP is used and NOOO new ATP is made

False

Each muscle fiber is innervated by a single motor neuron

TF The neuromuscular junc. is made up of

1. axon terminal of motor neuron

2. motor-end plate of muscle

False

When  Ach is released and it travels thru the synaptic cleft it attaches to  nicotinic receptors

TF The end-plate potential is an AP

False

it is a graded potential

Acholinenesterase

or cholinesterase

TF b.toxin isnt a toxin substance

False

it is a very toxic substance

less than 1 millionth of a gram can be lethal!!

1. paralyzes the muscle, including the diaphragm

2. causes respiratory failure

1. used in a dilute form to relax hyperexcitable muscles (it was injected into the muscle)

2. used cosmetically to get rid of deep wrinkles, aka botox injections

3. used for specific voice disorders

4. can be used to prevent excessive sweating

5. can be used to treat migraines

False

the drug that increases the release of Ach is knwn as black widow spider venom

False

they have opp. effects

a. bws venom causes an explosive release of Ach

b. b. toxin block the release of Ach

False

death from the venom is very rare!!

1. curare

2. alpha-bungaro toxin

curare

nicotinic

 TF most snake venom contains toxins that block nicotinic receptors, thus blocking release of Ach

What are T-tubules?

a. Transverse tubules

b. extention of the membrane and they run perpendicular from teh surface

c. tubules that carry AP deep within the muscle fiber

TF SR is a specialized organelle for the storage of intracellular K+

False,

it stores Ca2++

False

they pump Ca2++ IN

True

Smooth muscle is found in the digestive tract, blood vessels, ureters and uterus

False

Smooth muscle has smaller muscle fibers than skeletal muscle

2-5um diameter

20-500um in length

- has actin and myosin

-doesnt have myofibrils

no striations

no t-tubules

-poorly developed SR

- actin is bound to proteins callled "dense bodies" instead of z line

False

b/c smooth muscle has very little characteristics, it is best used for slow, prolonged muscle contraction

Skeletal muscle is used for the fast and powerful muscle contraction

False

Ca 2++ in smooth muscle enters from ECF

Ca 2++ in skeletal muscle enters from the SR

They form a complex which activates "myosin kinase"

myosin kinase activates myosin head

1. An AP runs down the smooth muscle membrane increasing level of Ca2++

2. Ca2++ enters the ICF from ECF

3. Ca2++ binds to calmodulin

4. Ca2++ and calmodulin form a complex which activates "myosin kinase"

5. myosin kinase activates myosin

6. myosin binds to actin, thus causing a power stroke

TF Smooth muscle can occur with the presence of Na+

False

it occurs with the presence of Ca2++

1. it is when cell membranes of adjacent cells are joined by gap juncs. which allow for flow of ions btwn cells

2. it is where depolarization in one cell causes depolarization in an adjacent cell

cell membranes that connect two indv. cells toge.

they contain:

1. gap juncs.

2. desmosomes

False

Desmosomes mechanically connect two cells toge.

Gap junc. connect to cells toge. for ion flow

False

Cardiac muscles have LONGER duration AP

False

Cardiac muscle DO have a Plateau phase, but in  the plateau phase you have an increased PERMEABILITY of Ca2++ due to the slow opening and closing of Ca2++ channels

False

high permeability = Ca2++

low permeability = K+ and Na+

False!!

Steady flow of Ca2++ occurs into ICF

maintains a (+) potential in ICF

False

prolonged AP =

1. prolonged muscle contraction

2. prolonged REFRACTORY period

1. prevents rapid restimulation of the heart muscle

2. allows for the efficient pumping of the blood and filling of hte heart

False

its the period from the beginning of one heartbeat to the beginning of another heartbeat

False

It is the relaxation phase

False

Normal systolic BP = 120mm of Hg

Normal diastolic BP = 80mm of Hg

heart is relaxed and filling with blood

BP is maintained by the elasticity of major arteries

1. contractile fibers

2. autorhythimic tissue

depolarization

Na+ channels

SA node = 70-80bpm

AV node = 40-60bpm

AV bundle = 15-40bpm

Purkinje fibers = 15-40bpm