1. The Muscular System

3. GET STARTED!
Get out a new sheet of paper – beginning of the Muscular System!
What do you think a muscle is made of? Diagram it!
1 lateral view of a whole muscle
1 transverse cross section of a muscle

4. Skeletal Muscle Organization
Muscle – packaged in epimysium
Fascicle – packaged in perimysium
Muscle Fiber (Muscle Cell) – packaged in Endomysium
Myofibrils – surrounded by sarcoplasmic reticulum
Myofilaments – Thick (myosin) and thin (actin) filaments

5. GET STARTED
Get out a blank piece of paper (half sheet will do). Number your paper from 1-9.

6. Organize these layers from OUTSIDE to INSIDE without using a book or notes
BONUS:
Where is the endoplasmic rheticulum?
These are all the SAME THING:
Myofilaments
Muscle filaments
Thick/thin filaments (TYPES of filaments)
Myosin/actin (protein which makes up the thick/thin filaments
Fascicles
Muscle
Myofibrils
Myofilaments
Sarcolemma
Epimysium
Endomysium
Perimysium
Muscle fiber

7. Neuromuscular Junction
Junction b/t motor neuron and muscle fiber
Motor Neuron: nerve cell which conducts impulses to the muscle
Motor Unit: the motor neuron and the group of muscle fibers a single motor neuron controls

8. Motor end plate: specialized are of the muscle fiber membrane where motor neuron connects
Synaptic knob: enlarged region at the distal end of the motor neuron axon contain synaptic vesicles

9. Synaptic cleft: space in the neuromuscular junction which the neurotransmitter crosses
Synaptic vesicles: membranous sacs of neurotransmitter
Neurotransmitter: biochemical messenger – in this case, acetylcholine

10. Muscle Fibers (Muscle Cell)
Sarcolemma: cell membrane
Sarcoplasm: cytoplasm
Sarcoplasmic Reticulum: endoplasmic reticulum (where proteins are made)
Transverse Tubules: tube connecting the muscle fibers to the sarcoplasmic reticulum and to the outside of the cell

11. The Filaments The thin filament
a strand of actin protein with “active” sites
a strand of tropomyosin protein wrapped around the actin, covering its active sites
troponin proteins attached to the tropomyosin

12. The thick filament several strands of myosin with globular heads
myosin heads have binding sites

13. The Sarcomere: a single unit
Myofibrils
Myosin
Actin
Z Line
M Line
H Zone
A Band
I Band

14. The Sarcomere Sketch, color, and label a diagram of the sarcomere
Filled in (micrograph picture)
Simple diagram
Page 174
Table beneath: describe what structures form each part
Parts to include:
Z Line
M Line
H Zone
A Band
I Band

15. The Sliding Filament Theory
First, the nerve impulse…
Acetylcholine is released at the neuromuscular junction
This causes the Sarcoplasmic reticulum releases calcium ions, which diffuse into the sarcoplasm

16. Now for the contraction: Calcium binds to the troponin
This causes the tropomyosin to shift off of the active sites on the actin
Binding sites on the myosin heads attach to active sites on the actin filament
This forms ‘cross-bridges’
The cross bridges use ADP to pull the actin inward toward the center of the myosin from both directions
ATP binds to the myosin causing the cross-bridges to release
And REPEAT

18. What happens in response:
The Z lines are pulled together
The sarcomere shortens
The I band disappears

19. Threshold Stimulus
The minimal amount of stimulation required to cause a muscle contraction
Normally, an impulse will release enough ACh to cause the fiber to reach its threshold stimulus

20. All-or-None Response
When the threshold stimulus is reached, the fiber contracts to its fullest extent
Normally, there is no partial contraction
This includes the entire motor unit

21. Recruitment
More force means that more motor units are used – not that fibers are contracting more

22. Muscle Tone While at rest the neurons continues to fire
Produces some amount of constant contraction

23. Smooth and Cardiac Muscle
Where are they found?
Voluntary or involuntary?
What is the difference in cellular structure?