Muscle Types and Movement Control

Movement

• Three categories of muscles: Smooth, Skeletal/Striated, and Cardiac.
• Smooth muscles control digestive and internal organs.
• Skeletal muscles control voluntary movements.
• Cardiac muscles control the heart.
• Muscle fibers receive information from a motor neuron axon.
• A neuromuscular junction is a synapse between a motor neuron axon and a muscle fiber.
• Acetylcholine causes muscle contraction.
• Antagonistic muscles work in pairs to produce movement.
• Flexors bend a joint; Extensors straighten a joint.
• Fast-twitch muscle fibers contract quickly but fatigue rapidly.
• Slow-twitch muscle fibers contract more slowly but do not fatigue easily.
• Proprioceptors are receptors that detect the position and movement of body parts.
• Muscle spindles and Golgi tendon organs are types of proprioceptors.

Reflexes and Movement Control

• Reflexes are involuntary, consistent, and automatic responses to stimuli.
• Monosynaptic reflexes involve one synapse.
• Movements can be reflexive or voluntary.
• A central pattern generator generates rhythmic movement patterns.
• A motor program is a learned or built-in sequence of movements.
• A brain-computer interface uses brain signals to control devices.
• Major components of motor system include the Cerebrum (forebrain), brainstem, and spinal cord.
• The cerebral cortex plans and executes complex behaviors.
• The prefrontal cortex plans movements.
• The premotor cortex produces movement sequences.
• The primary motor cortex controls specific areas of the body.

The Brain and Movement

• The primary motor cortex is involved in movement.
• The somatosensory cortex plays a role in the primary motor cortex.
• The posterior parietal cortex plans movements.
• Anti-saccade tasks inhibit movements.
• Mirror neurons may be involved in imitation and understanding of actions.

Spinal Cord and Tracts

• The corticospinal tracts are pathways between the brain and spinal cord.
• The lateral corticospinal tract controls peripheral areas like hands and feet..
• The medial corticospinal tract controls trunk and neck muscles.
• The red nucleus and vestibular nucleus are involved in motor control.

Brain Stem and Movement

• The brainstem helps maintain posture and coordinates bilateral body movements.
• The brainstem is involved in movement, posture, and balance.

Disorders

• Locked-in syndrome: a condition of complete paralysis except for eye movements.
• Spinal cord damage can result in quadriplegia or paraplegia, causing paralysis and loss of sensation.
• Spinal reflexes are still possible after spinal cord injury.
• Various disorders such as Paralysis, Quadriplegia, Hemiplegia, Tabes Dorsalis, Poliomyelitis or Amyotrophic lateral sclerosis affect movement.

Huntington's Disease

• Huntington's disease is a neurological disorder characterized by motor symptoms, cognitive decline, and emotional disturbances.
• It affects approximately 1 in 7000 individuals in Canada and typically emerges between ages 30 to 50.
• Symptoms involve involuntary movements (chorea), cognitive problems, and emotional changes.
• Presymptomatic testing and genetic screening can identify those at risk of acquiring Huntington's.
• The disease is hereditary and is linked to a specific genetic mutation.
• It is progressive and ultimately fatal.

The Cerebellum

• The cerebellum plays a crucial role in balance, coordination, and precise control of movement.
• Damage to the cerebellum results in problems with rapid movements, timing, and coordination.
• The cerebellum receives information about intended movements and actual movements to calculate errors and correct movement sequences.
• The finger-to-nose test can be used to assess cerebellar function.

Basal Ganglia

• The basal ganglia are a group of subcortical structures involved in initiating and coordinating movement.
• Damage to the basal ganglia can cause involuntary movements or difficulties with initiating voluntary movements.
• Basal ganglia are responsible for selecting and initiating voluntary movements and inhibiting unwanted movements.

Parkinson's Disease

• Parkinson's is a movement disorder characterized by difficulties initiating, controlling, and coordinating movement.
• It's caused by neuronal death in the substantia nigra, which normally produces dopamine.
• Dopamine is critical for smooth, uncontrolled movements,
• Parkinsons symptoms include tremors, rigidity, slowness of movement, balance and posture problems.
• Treatments include medication such as L-dopa and other therapies.