1. Muscular System
Honors Biology

3. Muscles
From the Latin mus meaning little mouse (Flexing muscles looked like mice scurrying under the skin)
Have ability to transform ATP into mechanical energy
Muscles can only pull, never push, which allows them to exert a force

4. ATP --> ADP + P + Energy
ADP + P + Energy ---> ATP

5. Muscle Types Skeletal - Slow to Fast twitch Cardiac - Fast twitch
Actin
Myosin
Skeletal - Slow to Fast twitch
Cardiac - Fast twitch
Smooth - Slow twitch
Twitch = contraction
Skeletal & smooth muscle cells are elongated & called fibers
All have contractile myofilaments actin & myosin

6. Muscle Fxn’s -Produce movement
Skeletal – locomotion & manipulation in response to the environment
Cardiac – moves blood
Smooth – propels (squeezes) stuff through the digestive, urinary, circulatory, and reproductive systems
-Maintaining posture
-Stabilizing joints
-Generating heat (40% of your body heat)

7. Skeletal Muscle Striated Multinucleate Voluntary muscles
Can generate great power but fatigue quickly
Non-rhythmic contraction

10. Sarcoplasmic Reticulum
Sarcolemma
(Plasma membrane)
Sarcoplasm = (Cytoplasm with lots of glycogen stored)

11. Sarcomere – Contractile Unit of Muscle

14. Nerve & Blood Supply Each muscle is served by: 1 nerve 1 artery
1 or more veins

15. Skeletal Muscle Attachment
Skeletal muscles attach to bones in at least 2 places
When the muscle contracts, the moveable bone (Insertion), moves toward the immovable or less-moveable bone (Origin)

18. Sliding Filament Theory
Hugh Huxley 1954 proposed that during contraction actin will slide past myosin which result in overlapping filaments
Cross bridge attachment
Power stroke (Myosin head pivots pulling actin)
Cross bridge detachment (ATP binds to myosin head loosening the bond to actin)
“Cocking” the myosin head – ATPase hydrolyzes ATP to ADP & Pi returning the myosin head to it’s cocked position

24. Regulation of Contraction
Muscle contraction is stimulated by an action potential from a nerve
The neuromuscular junction in skeletal muscle is regulated by acetylcholine (ACh)
Ach needs to be broken down as soon as it is used; the enzyme acetlycholinesterase serves this function.

26. a. b. c.

30. Generating an Action Potential
Depolarization (Na channels open)
Repolarization (Na channels close K channels open)
Refractory Period (K channels close)
Na/K pump

32. Homeostatic Imbalance
Myasthenia gravis – autoimmune disease where ACh receptors are broken down by ACh antibodies resulting in drooping eyelids and general muscle fatigue
Curare – arrowhead poison used in South America which blocks ACh receptors resulting in respiratory arrest & death
Cobra venom – same as curare
Botulinum toxin prevents ACh release
Black widow spider venom releases all Ach
Nerve gasses inhibit AChase which keeps cleft flooded with ACh

33. ACh destruction
After ACh initiates the action potential the ACh is broken down by acetylcholinesterase
This prevents continued muscle contraction in the absence of additional nerve stimuli

34. Mysostatins control muscle growth
Absence of results in enlarged muscle development