EXAM 4: Muscle Control & Energetics Flashcards
(41 cards)
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
What does the starting length of a sarcomere predict
The amount of tension generated
What does skeletal muscle contraction (exercise) require to function
ATP
What is required to prepare myosin (extended conformation) to interact with actin
ATP hydrolysis
Is the ATP supply unlimited?
No, it is limited
The body must have a way to regenerate ATP from ADP
What are the 3 mechanisms used to regenerate ATP from ADP to sustain contractions
Aerobic respiration
Anaerobic respiration
Phosphorylation using creatine phosphate (CP)
What determines what ATP generating mechanism is used
The type of exercise (muscle contraction)
The duration and intensity or the exercise
What is metabolized in Aerobic respiration to convert ADP to ATP
Glucose, fatty acids and proteins in the mitochondria
How many steps does aerobic respiration take? How much time does it take?
Many steps, takes time
