Bio 137 : Chapter 11

Excitability

Nervous system

Action potential

Conductivity

Transmitting impulse

Contractility

Stimulated

Extensibility

Flexibility

Elasticity

Stretches back to normal state

Skeletal muscle

Voluntary

Heavily striated

Multiple nuclei

Cardiac muscle

Lightly striated

One nuclei

Autorhythmic

Aerobic

Smooth muscle

Involuntary

No striations

No sarcomeres

Slow/weak contractions

Where is smooth muscle found

Blood vessels

Digestive tract

Muscle in skin

Iris

Crucial for contraction

Calcium

Sarcolemma

Endomysium

Myofibrils

Occupying most of sarcoplasm

Contains protein

Slow twitch muscle

Many mitochondria

Marathon runner

No hypertrophy

Fast twitch muscle

Few mitochondria

Olympic sprinter

Hypertrophy

Sarcoplasmic reticulum and terminal cistern

Calcium storage

Triad

2 terminal cisterns and T Tubule

Transports calcium during action potential to begin contraction

T Tubule

Myosin

Thick filaments

golf club shape

Binds to actin active site

Actin

Thin filaments

Binds to myosin head

Tropomyosin

Guards the active site

Troponin

Calcium binding protein

Dystrophin

Structural stability

Muscular Dystrophy

Born w/o dystrophin protein

Can’t stabilize the muscle

Myasthenia gravis

Destroys ACh receptors on muscle

autoimmune

A band

Both

H band

Myosin

I band

Actin

Sarcomere

Z disc to Z disc

Functional unit of muscle contraction

Sarcomere shortens

Filaments don’t shorten regions do

Skeletal muscles cannot contract unless stimulated by a nerve

Excitability

Somatic motor fibers

Efferent

All muscle fibers innervated by one neuron

Motor unit

Small motor and ex.

Precision

Hand muscles

3-5 muscle fibers each

Large motor and ex

Power

Quadriceps femoris

Hundreds of fibers

Synapse

Space

Neuromuscular junction (NMJ)

Nerve and muscle meet

Transmitter used during skeletal muscle contraction

Acetylcholine (ACh)

Sarcolemma synaptic cleft

Space between neuron and muscle

Presynaptic

Neuron

Postsynaptic

Muscle

ACh receptors

Muscle

Acetylcholinesterase (AChE)

Enzyme

Breaks down ACh

Allowing for relaxation after contraction

Excitation

Action potential

Impulse

Axon terminal

Excitation-contraction coupling

Acetylcholine released

Contraction

Actin & Myosin

Relaxation

Muscle fiber relaxes

Length tension relationship

Cross bridge

Cross bridge

Joining of myosin and actin

Muscle relaxation requires ATP

Myosin head stays connected to active site 

Creates contraction

Rigor mortis

Isometric contraction and Ex.

Same length

Same tension

Plank

Isotonic contraction and Ex.

Same tension

Different length

Weight training

Isotonic

Concentric contraction

Muscle shortens 

More tension

Isotonic

Eccentric contraction

Muscle lengthens

Less tension