Voluntary Movement Flashcards
Describe voluntary actions
Self-initiated Purposeful - goal directed Learned Improved with practice Adaptable
What are semi-automatic actions
Voluntary - but you don’t have to think about them
Often they are repeated movement sequences
Give examples of semi-automatic actions
Walking, breathing, chewing
What are CPGs
Central pattern generators
Initiate and maintain a specific action
May be synchronised eg - swinging arms and legs
Why are feedback loops important in CGPs
Constant feedback of info ensures that the reaction we have to our environment is appropriate
Describe the corticobulbar pathway
Arises from the primary motor cortex
Fibres converge and pass through the internal capsule to the brain stem
The neurons terminate on the motor nucleu of the cranial nerves where they synapse with lower motor neurons which carry the motor signals to the muscles of the face\
What is an important feature of the corticobulbar pathway
Often axons bifurcate meaning it can recruit muscles on both sides of the body allowing synchronised muscle contraction
Describe the corticospinal pathway
Originate in the motor cortex and axons project right through the brainstem to the pyramids in the medulla oblongata
Here the axons split, 85% cross over to the opposite side and project down the spinal cord to innervates their appropriate lower motor groups
What is the lateral corticospinal pathway
The 85% of the axons that cross over to the other side of the body
What is the anterior corticospinal pathway
The 15% of the axons which do not cross over to the other side of the body
What happens if a descending pathway is damaged
Damage (lesions) to pathway impairs their normal functions
What is a palsy
Paralysis to motor pathways caused by lesions
What are some causes of paralysis in lower motor neurons
Damage to LMN
Nerve injury
Viral infection (polio)
Describe paralysis in upper motor neurons
Damage in corticospinal and corticobulbar tracts
Damage to UMN
CNS injury (stroke)
What are some results of paralysis in lower motor neurons
No reflexes
No voluntary movement
Muscle atrophy
What are some results of paralysis in upper motor neurons
No voluntary movement
Reflexes present but exaggerated
What are additional descending motor projections
Arise from various areas of the cerebrum and brainstem
Basal ganglia, cerebellum and brainstem
What is the function of additional descending motor projections
Serve to co-ordinate movements
Help maintain posture/balance
Help integrate actions of several muscles
What is the basal ganglia
Comprised of several interconnected sub-cortica nuclei
Link to cerebral cortex via feedback loops
Influence/regulate output from the motor cortex
Act to initiate actions and to switch from one action to another
What makes up the basal ganglia
Body of caudate nucleus Putamen Globes Pallidus Thalamus Substantial Nigra Corpus callosum
What is the corpus callosum
Allows the two sides of the Brian to communicate
What are the action selection centres
Corpus striatum
Sub-thalamus nuclei
Substantial nigra
What makes up the corpus striatum
Caudate nucleus
Putamen
Globes pallidus
What does damage/disease to the substantial nigra result in
Parkinson’s disease
What does damage/disease to the corpus striatum result in
Huntington’s disease
Give examples of some basal ganglia disorders
Parkinson’s disease
Huntington’s disease (Chorea)
What do patients with Parkinson’s disease usually present with
Hypokinetic disorder so decreased movements Resting tremor Poverty of movements Mask-like face Difficulty initiating movements Domapine deficiency in substantial nigra
What do patients with Huntington’s disease usually present with
Hyperkinetic disorder so increased movements
Excessive, uncontrolled movements
Imbalance of neurotransmitter
Decreased levels of GABA
What are the functions of the cerebellum
Co-ordinating movements
Regulates actions of antagonistic muscle groups
Important in maintaining balance - receives inputs from proprioceptors
Acts to compare actual performance with what is intended
Describe cerebellum disorders
Characterised by loss of co-ordination
Unsteady gait (ataxia)
Imprecise actions
Inability to co-ordinate altering contractions of antagonistic muscles
Intention tremor (resting tremor in Parkinson’s)
Why are actions usually co-iordinated
To ensure that posture/balance is maintained
Describe how posture is maintained
Forward sway stretches muscles in the back of the leg
Upright posture is maintained by a series of smaller correcting actions
These help keep the position of the head inline with gravity
