Lecture 24 Flashcards
What does voluntary movement require
Immensely complex neural interactions.
It involves intricate interactions between various regions of the brain, spinal cord, and peripheral nervous system, coordinating muscles and joints to execute precise actions.
Prefrontal cortex
This is the Neurons involved in decision making and planning the desired movement outcome
Permotor cortex
This is the neurons involved in organising movement sequences to achieve the octcome,
For example, walk to the stairs, climb 10 stairs down
So this is all about organising movement
Primary motor cortex
- this is made of cell bodies of upper motor neurons
- this is the neurons involved in directing voluntary movement
so for example: activate knee and hip flexors to step up…. And ect
How do you plan movement and initiating movement
- prefrontal cortex - plan
- pre motor cortex - move
- motor cortex - telling the bones what to do
Modifying movement: Basal Nuclei
- influences posture and automatic movements
- regulates muscle tone
- refines movements - selects which to allow and witch to inhabit, how they do this is they alter sensitivity of neurons projecting into the corticospinal or other pathways
Modifying movement: cerebellum
- this stores and facillstes learning, planning and execution of motor programs ( eg: walking program )
- monitors and compares sensory inputs to compare actual movement to planned movement
- organises timing of muscle contractions and modifies ongoing activity
Pathway from brain to muscle: Corticospinal pathway
So the upper motor neurons in the primary motor cortex fire action potentials that propagate along axons extending down the spinal cord to activate lower motor neurons in spinal cord, to fire action potentials that propagate along axons withen peripheral nerves to skeletal muscle
What is a motor unit made out of
Single lower motor neuron plus all the skeletal muscle fibres in innervates
Small motor unit
- a motor neuron plus the few muscle fibres it activates
- can produce more precise movement ( eg; hands lips, tounge )
Large motor unit
- a motor neuron plus the many muscle fibres it activates
- can produce more forceful movements ( eg: of limbs )
Voluntary movement: - response time
Voluntary responses to touch:
This includes complex neural processes that include the transmission of sensory information from the point of touch to the brain and the subsequent generation of motor response
- 100+ ms latency ( the point at how long it takes for the sensory signal to travel to the brain )
- high variable
- path : from foot to brain, then ti quadreps muscles
- focus and training can reduce response time as it reduces the number of neural connections involved
Strech reflex - response time
Reflex response to tendon tap
- 30 - 40ma latency
- very consistent
- protects muscles from tearing
- path : from stretched muscle spindles to spinal cord to stretched muscle
- cannot be changed with training
Strech reflex response - how it happens
- tendon tap causes sudden, fast stretch of quadriceps muscles
- muscle spindles ( proprioceptors/strech receptors withen the muscle ) gets stretched
- mechanically gated Na+ channels open in membrane and dendritic endings of the sensory neuron of the muscle spindle
- Na+ entry causes depolarisation that leads to an action potential which propagates along sensory axon to spinal cord
- synaptic transmission from sensory axon terminal causes depolarisation in motor neuron cell body
- AP fires and propagates along motor axon to NMJ of quadriceps
- stimulating quadriceps to contract, causing the foot to kick out
Reflex response to painful stimuli
- Nociceptors activated
- sensory neuron depolarises and action potential fires and propagates to spinal cord
- sensory neurons stimulates inter neurons, leading to excitation of motor neurons that stimulate flexors and inhibition of motor neurons that stimulate extensors, enabling withdrawal of the affected limb
