More of an audutory learner? Click the link to listen to a 10 min podcast on this summary - courtesy of Justin!
https://notebooklm.google.com/notebook/9411d152-bd94-4512-995c-19e6a43e977c/audio
I've taken the liberty of making flashcards from this summary.
Here you can find the detailed flashcard deck with most of what you may need to know:
https://quizlet.com/ca/953738023/locomotion-and-voluntary-movement-overview-flash-cards/
Lecture 4 Summary: Locomotion
Lower Motor Neurons (LMN) and Upper Motor Neurons (UMN):
LMNs are located in the spinal cord and brainstem, projecting out of the CNS to muscles. They are responsible for all movements and are the "final common pathway."
Example: In tick paralysis, LMNs are affected by neurotoxins, causing muscle weakness (paresis).
UMNs are confined to the CNS and divided into pyramidal and extrapyramidal systems, which control voluntary movement and posture.
Example: The pyramidal system is important in primates and humans for fine motor control, while the extrapyramidal system is crucial for posture and locomotion in animals.
Motor Unit and Size Principle:
A motor unit consists of a motoneuron and the muscle fibers it innervates. According to the size principle, small motoneurons, which innervate slow Type I muscle fibers, are recruited first, followed by larger motoneurons, which control fast Type II fibers.
Example: In activities requiring endurance, slow Type I fibers are engaged first, while fast Type II fibers are used in short bursts of high-intensity movement like sprinting.
Myotatic (Stretch) Reflex and Golgi Tendon Reflex:
The myotatic reflex is a fast, involuntary muscle contraction in response to muscle stretch. It involves muscle spindles detecting stretch and triggering contraction via alpha motoneurons.
Example: The knee-jerk reflex is a classic demonstration of the myotatic reflex.
The Golgi tendon reflex inhibits motoneurons to protect muscles from excessive force during contraction.
Example: When lifting a heavy object, the Golgi tendon organ prevents muscle injury by inhibiting excessive contraction.
Types of Gait:
Different gaits (patterns of footfalls) are used based on speed and terrain. Common types of gait include:
Walk: A four-beat gait with maximum support.
Trot: A faster two-beat diagonal gait.
Canter: A three-beat gait used at moderate speed.
Gallop: A four-beat gait with variations like transverse and rotary gallops.
Example: A dog switches from a trot to a gallop when chasing after a ball.
Central Pattern Generators (CPGs):
CPGs are neural circuits in the spinal cord capable of producing rhythmic motor patterns like walking without the need for sensory feedback or input from higher brain centers.
Example: Even after the brain is damaged in some animals, CPGs in the spinal cord allow basic locomotor functions, such as walking, to continue.
UMN Tracts and Their Functions:
Several UMN tracts control different aspects of movement:
Rubrospinal Tract: Promotes voluntary movement, especially flexion in large muscles.
Reticulospinal Tract: Controls posture and the initiation of walking.
Vestibulospinal Tract: Maintains balance and posture.
Corticospinal Tract: Facilitates voluntary movements, particularly fine motor control.
Example: A dog with damage to the vestibulospinal tract may struggle to maintain balance, leading to unsteady walking.
Control of Voluntary Movement:
Voluntary movement is controlled by the motor cortex (M1) and integrates inputs from the basal ganglia, which are essential for the planning and execution of movements.
Example: During a precise task like grabbing a toy, the motor cortex coordinates hand-eye movements, while the basal ganglia help ensure smooth execution.
Lecture 5 Summary: Voluntary Movement
Lower Motor Neurons (LMNs) and Upper Motor Neurons (UMNs):
LMNs innervate skeletal muscles and are responsible for motor unit activation, which leads to movement. LMNs form part of the reflex arc that controls reflexive movements.
Example: If a dog steps on a sharp object, the withdrawal reflex involves LMNs that quickly activate the muscles to move the paw away.
UMNs control voluntary movement and posture through tracts like the corticospinal tract. UMNs send signals from the brain to LMNs in the spinal cord.
Example: The rubrospinal tract helps control voluntary movement in large muscles, such as when a cat jumps onto a surface.
Brain Mapping of Motor Areas:
Brain mapping, pioneered by Dr. Penfield, showed that different areas of the motor cortex control different parts of the body. The motor homunculus is a visual representation of this map, showing that the hands and face have larger areas of cortical representation due to the complexity of their movements.
Example: Fine motor control in the hands requires a large area of the motor cortex, as demonstrated in activities like typing or holding surgical instruments.
Motor Sequence and Learning:
Complex movements are broken into simpler sequences. Repetitive practice of these sequences leads to motor memory and automation.
Example: A pianist playing a complex piece of music relies on motor memory to execute sequences of finger movements without conscious thought.
Mental imagery is used by athletes to improve performance. Visualizing movements can enhance both motor skill and psychological factors like confidence.
Example: An Olympic diver may mentally rehearse their routine to improve precision and control.
Cerebral Cortex and Motor Output:
The primary motor cortex (M1) is responsible for simple movements, while more complex tasks (like coordinating multiple joints) involve other brain regions such as the premotor cortex and supplementary motor area.
Example: Catching a ball requires a combination of simple and complex movements, with inputs from M1 and other cortical areas for precise hand-eye coordination.
Basal Ganglia:
The basal ganglia play a critical role in movement control by regulating which movements to facilitate and which to inhibit. Although they do not have direct connections to the spinal cord, they influence movement through the thalamus and cortex.
Example: Disorders of the basal ganglia, such as Parkinson’s disease, lead to movement issues like tremors and difficulty initiating movement, as seen in affected humans.