____ Chapter 49 ~ Sensory and Motor Mechanisms

(Just focusing on motor

mechanisms) Motor Mechanisms

Vertebrate Skeletal Muscle Contract/relax: antagonistic

pairs w/skeleton Muscles: bundle of….

Muscle fibers: single cell w/ many nuclei consisting of…. Myofibrils: longitudinal bundles

composed of…. Myofilaments:

Thin~ 2 strands of actin protein and one strand of a regulatory protein

Thick~ staggerd arrays of myosin protein

http://entochem.tamu.edu/MuscleStrucContractswf/index.html

Vertebrate Skeletal Muscle

Sarcomere: repeating unit of muscle tissue, composed of….

Z lines~sarcomere border I band~only actin protein A band~actin & myosin protein overlap H zone~central sarcomere; only myosin

http://www.sumanasinc.com/webcontent/animations/content/muscle.html

Sliding-filament model Theory of muscle contraction Sarcomere length reduced Z line length becomes shorter Actin and myosin slide past each other (overlap increases)

http://www.blackwellpublishing.com/matthews/myosin.html

Actin-myosin interaction 1- Myosin head hydrolyzes ATP to ADP and inorganic

phosphate (Pi); termed the “high energy configuration” 2- Myosin head binds to actin; termed a “cross bridge” 3- Releasing ADP and (Pi), myosin relaxes sliding actin;

“low energy configuration” 4- Binding of new ATP releases myosin head Creatine phosphate~ supplier of phosphate to ADP

Muscle contraction regulation, I

Relaxation: tropomyosin blocks myosin binding sites on actin

Contraction: calcium binds to toponin complex; tropomyosin changes shape, exposing myosin binding sites

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__action_potentials_and_muscle_contraction.html

Muscle contraction regulation, II

Calcium (Ca+)~ concentration regulated by the….

Sarcoplasmic reticulum~ a specialized endoplasmic reticulum

Stimulated by action potential in a motor neuron

T (transverse) tubules~ travel channels in plasma membrane for action potential

Ca+ then binds to troponin

Materials Muscle model/chicken wing The following is needed for each student: 4

red/black licorice strands (the thick twisted type)

10 red licorice strands (the thin type) a paper towel; toothpicks one raw chicken wing one dissection tray; dissection tools, gloves.

Muscle cell simulation: contraction/relaxation

Procedure: Two thin pieces of licorice intertwined to

represent thin actin filaments Thick licorice to represent thick myosin

fibers Toothpicks represent the Z lines where thin

filaments attach