Lec 2 exam chapter 7

part 2

myoglobin

red pigment that stores oxygen

sarcoplasmic reticulum (SR)

smooth ER that is filled with and stores Ca²⁺ and when it releases it, it stims muscle contractions

transverse (T) tubules

extensions of sarcolemma that carry impulse into fiber

Protiens

Myosin

1. several hundred myosin myofilaments form thick filaments

a.  have heads that are chemically

Protiens

Actin

2. 2 strands of actin myofilaments form thin filaments

a.  have active sites for myosin heads to attach to

Protiens

Tropomyosin

3. covers actin active sites

Protiens

Troponin

1. holds topomyosin in place over actin active site

the sarcomere anatomy

A (anisotropic) bands

1. contains thick and thin filaments

the sarcomere anatomy

I (isotropic) bands

2. contains only thin filaments

the sarcomere anatomy

Z line

3. line in center of I band that thin filaments attach to

Acetylcholine (ACh)

neurotransmitter released from the synaptic vesicles that stimulate the muscle fiber

Na and K

Sodium ions are more concentrated outside of the cell and Potassium ions are more concentrated inside of the cell.

muscle cells

can conduct electrical impulses

What is the sequence of events that leads to the exposure of actin active sites during muscle contraction?

1. Action potentials travel across the sarcolemma and down the T tubules.

2. This stimulates Ca²⁺ channels in the sarcoplasmic reticulum (SR) to open, releasing Ca²⁺ into the sarcoplasm.

3. Ca²⁺ binds to troponin, causing the troponin-tropomyosin complex to shift and expose the actin active sites.

Tonic contraction

continuous partial contraction of a muscle

Isometric contraction

contraction without a change in length but increase in tension

Isotonic contraction

contraction with a change in length but no change in tension

ATP- is the energy source for cells. workout and eating

a.  Energy is released from ATP when the third phosphate is broken off

b.  This leaves us with ADP (adenosine diphosphate) and a phosphate

c.  ATP can be regenerated when a phosphate is added onto ADP

ATP sources 1

Aerobic respiration

1. using oxygen to breakdown glucose (and other organic compounds) into CO₂ producing ATP

a.  Yields 36 ATP/glucose

ATP sources 2

Anaerobic fermentation

2. breaking down glucose without oxygen to produce ATP

a.  Yields 2 ATP/glucose

b.  By-product is lactic acid which causes muscle fatigue

myokinase

1. transfers a phosphate (Pi) from one ADP to another

Creatine kinase

Slow twitch fibers - dark/migration birds

1. endurance fibers; abundant mitochondria, myoglobin, and blood vessels

Fast twitch fibers - whiter/chicken

1. quick, strong contractions; rich in creatine and glycogen, SR releases Ca²⁺ quickly, few mitochondria and blood vessels, little myoglobin

Muscular conditions

tetanus

Clostridium tetani secretes a toxin that blocks an inhibitory neurotransmitter called glycine resulting in overstimulation of muscles

Muscular conditions

rigor mortis

3-4 hours after death SR deteriorates releasing Ca²⁺ stimulating contraction