EXAM 4: Muscle Control & Energetics Flashcards
Can muscle cells excite each other
NO! Each muscle cell must be excited by a branch of a motor neuron
What is a motor unit
All the muscle fibers that ONE motor neuron controls
What does the size of motor units depend on
Muscle function
Many small motor units are used for…
Find control
Ex: muscles that move the eye
One motor unit would contain ~12 muscle cells
Fewer larger motor units are used for…
Powerful but less precise movements
Ex: Deltoid muscle
One motor unit would contain hundreds to thousands of muscle cells
Muscle cells of one motor unit are…
Spread throughout the entire muscle
Are all motor units activated at the same time?
No!
What does progressive activation allow for
Varying strengths of contraction
Contraction of one motor unit
Weak contraction of entire muscle
Contraction of subsequent motor units
Will increase strength of muscle contraction
- Recruitment
How does muscle generate a contraction appropriate for the load?
Somatic sensory neurons (proprioceptors) and inter neurons in the cerebrum inform cerebellum via action potentials if contraction is strong enough. If not… more muscle calls are recruited
Cerebellum function
- Coordinates movements
- Controls posture, balance and fine motor movement
- Involved in motor learning
Picking up a glass of milk:
What occurs in step 1 (plan to pick up the glass of milk)
Interneurons from brain initiate action potentials
- Planning in the motor cortex of the forebrain
- special senses (sight, balance)
Picking up a glass of milk:
What occurs in step 2 (pick up the glass of milk)
Proprioceptors ( somatic sensory neurons ) tell your body where your limbs are
- Also responsible for sense of force and heaviness
Picking up a glass of milk:
What occurs in step 3 (Did you pick up the glass of milk? Do you need more force?)
Proprioceptors tell your body if you have moved the glass of milk
Information from the somatic sensory proprioceptors will integrate with information from the forebrain in the cerebellum (hindbrain) = coordination
What does the amount of force that a muscle can produce depend on
It depends on the length of a sarcomere before contraction occurs
