Anatomy Exam 2

Question 1

Muscle

Answer 1

Bundles of muscle fasciculi- surrounded by epimysium

Question 2

Fasciculi

Answer 2

Bundles of muscle fibers- surrounded by perimysium

Question 3

Muscle fiber

Answer 3

The muscle cell - surrounded by endomysium

Question 4

Myofibrils

Answer 4

Bundles of contractile proteins in muscle cell

Question 5

Myofilaments

Answer 5

The contractile proteins

Question 6

Thick myofilaments

Answer 6

Myosin

Question 7

Thin myofilaments

Answer 7

Actin+ ensheathing proteins troponin and tropomyosin

Question 8

The Sarcomere

Answer 8

The basic contractile unit of the myofiber

Question 9

A bands

Answer 9

anisotropic bands (dark)

Question 10

I bands

Answer 10

isotropic bands (light)

Question 11

H zone

Answer 11

clear zone

Question 12

Z line

Answer 12

connecting points of sarcomere to another

Question 13

General Sequence of Events in Myofiber Contraction

Answer 13

1. Stimulus
2. ACh-gated sodium channels open
3. Na+ initiates action potential along muscle cell membrane
4. action potential passes over cell membrane and enters cell via modified E.R. termed the sarcoplasmic reticulum
5. Action potential stimulates the release of Ca++ from SR
6. Ca++ produces
   a. configuration changes in ensheathing proteins
   b. stimulates ATPase activity of myosin
7. Actin and myosin attract each other (sliding filament theory)
8. Inactivation of ACh by Chase end depolarization (AChase(AChE) breaks down 25,000 molecules of EACh per second)
9. Ca++ actively transported back into SR
10. Filaments release and slide back into resting state- movement aided by elastic nature of connective tissues associated with muscle cells

Question 14

Filament overlap

Answer 14

Skeletal muscle = maximum at resting length
Cardiac muscle = maximum when slightly stretched

Question 15

Energetics of Muscle Contraction

Answer 15

Energy required for :
-activation of myosin
-Ca++ pump
-Na+/K+ pump
Energy sources:
-ATP - 1-2 second supply
-Phosphocreatin- energy transferred to ATP 6 seconds
-Stored glycogen - glycolysis= 2 1/2 times faster than oxidative reaction - 1 minute supply
-Oxidative metabolism - long term contraction, primary fuel source is fat

Question 16

Isometric

Answer 16

no movement, no work

Question 17

Isotonic

Answer 17

movement and work

Question 18

Muscle Twitch Phases

Answer 18

Stimulus
Latent period
Contraction
Relaxation
Refractory

Question 19

All of None principle of muscle contraction

Answer 19

muscle fiver stimulated at threshold level will contract completely

Question 20

Motor unit

Answer 20

motor nerve fiber and all of the muscle cells it controls

Question 21

Variations in strength of contraction due to motor unit structure

Answer 21

Low ratio motor units- fine control
High ratio motor unites - coarse control