• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/40

Click to flip

40 Cards in this Set

  • Front
  • Back
What are the components of a motor unit?
-a single alpha motor neuron
-all its axon terminals
-the skeletal muscle fibers it innervates
Define motor unit.
-contractile group
-the smallest sub-unit of muscle that can individually and willfully be controlled
True or false: Motor neurons do not innervate intrafusal fibers.
True (intrafusal fibers are not part of the motor unit)
True or false: A motorneuron may have a hundred or more axons that innervate different muscle fibers.
True
The smaller the motor unit,:
-the less force it produces
-the more graded the force production of the entire muscle (fine motor control)
-small motor units innervate fewer muscle fibers
The number of muscle fibers served by a single axons varies. What are the 2 types of controls?
-fine control
-gross control
Describe course control.
-gross motor
-1 motor neuron to 300 fibers (leg)
-simplifies motor programming
Describe fine control.
-1 motor neuron to 3 fibers (eye)
-more independent control
How does muscle power increase?
-recruitment of more motor units (population code)
-increased frequency of discharge in each unit (frequency code)
During a "maximal voluntary contraction" all motor units are activated?
-No, some reserve is left
What are the types of muscle action? AND tell what they do.
-phasic (causes movement)
-tonic (causes tension rather than movement)
What is the problem of motor control?
-degrees of freedom in the neuromotor system (each level has a level of control)
-How do we ever achieve control over all these elements to perform simple motor tasks? (we don't know)
True or false: Muscles move.
False: Muscles can only pull bone or change shape.
What are antagonist muscles?
joints must have a pair of muscle with opposite actions, because muscle cannot push the bones but only pull them
What are agonist muscles?
-muscles that help each other
-result of a group of muscles (synergies)
Describe skeletal muscle.
-striated
-voluntary control
-contractions fast
-composed of chains of sarcomeres
Describe smooth muscle.
-slow and sustained contractions
-contracts in waves across entire muscle
-stomach, intestines, blood vessels
-innervated by autonomic nervous system
-responds to neural or hormonal stimulation
What two fiber types are skeletal muscles composed of?
-extrafusal
-intrafusal
What are extrafusal fibers?
-part of skeletal muscle
-innervated by alpha motorneurons from spinal cord
-exert force
What are intrafusal fibers?
-part of skeletal muscles
-muscle spindle
-sensory organ even though its a muscle
-sensory fibers and motor fibers that do not generate force
What do the afferent fibers of intrafusal fibers (muscle spindle) do?
-report length of intrafusal
-when stretched, the fibers stimulates the alpha-neuron that innervates the muscle fiber
-maintains muscle tone
What do the efferent fibers of intrafusal fibers (muscle spindle) do?
contraction adjusts sensitivity of afferent fibers
What are extrafusal muscle fibers made up of?
thousands of myobibrils
What are myofibrils? AND what are myofibrils made up of?
-the contractile apparatus
-made up of strands of sarcomeres, longitudinal array of protein filaments (actin and myosin)
What is a sarcomere?
-a repeating unit of the muscle cell's contraction machine (make up myofibrils)
-chains of sarcomeres give the striated appearance
What is the sarcolemma?
-the covering of muscle fiber (muscle cell membrane)
-conducts the electrical signal that initiates muscle contraction
-includes 'Transverse tubules' or 'T-tubules' that penetrate deep into the interior of the fiber
Describe the sarcoplasmic reticulum.
-smooth endoplasmic reticulum of muscle fibers
-stores calcium
-comes into contact with the T-tubules
-surronds the myofibrils
-upon activation by an electrical signal (by ACh)--releases Ca++ to activate the contractile apparatus
What cause the myofibrils to contract?
the presence of Ca++
What is actin?
-part of a myofibril
-thin protein filament that extends from wall of sarcomere
What is myosin?
-part of myofibril
-thick filament in the middle of the sarcomere
What are transverse tubules?
-carry the AP into the interior of the cell
What does anticholinesterases nerve gas do?
-affects NMJ
-paralyzing drug
-nerve agent binds to part of the AChE molecule
-thus, ACh hangs around and keeps the endplate polarized
What does botulinum toxin do? AND how is it used therapeutically?
-affects NMJ
-blocks release of ACh from the presynaptic terminal (ACh antagonist)
-Therapeutic use: injected into muscles of people with uncontrolled muscle spasms
What is myasthenia gravis? AND how can it be controlled?
-caused by a loss of ACh receptors in the motor endplates of all muscles in the body
-patients become very weak, but can be helped by controlled doses of anti-cholinesterases (allows the ACh to act longer. maximizing the use of the few receptors that are left)
What drugs affect NMJ?
-curare
-anticholinesterases
-botulinum toxin
What is curare?
-affects NMJ
-paralyzing drug
-blocks ACh from binding with receptor
-muscle cell can no longer be depolarized
True or false: ACh's binding with its receptor is not permanent.
True
What destroys ACh when it is released? AND where is it present?
it is destroyed by an enzyme, AChE (AChase), which is present in the synaptic cleft
Why is it essential for AChE to destroy ACh?
-so that the muscle cell membrane can repolarize to its resting potential
-if a muscle cell cannot repolarize (get rid of the e.p.p.), then it cannot generate another AP
What does the bond between actin and myosin create?
muscle tension