- The spinal cord controls automatic responses through the "stretch reflex", which is the contraction that occurs when muscles flex 
- This occurs through e negative feedback loop, where muscle is stretched, and afferent muscle fibers are excited (stimulate electrical impulse) and (in turn) excite the motor neurons 
- The motor neurons then provide a negative feedback to the muscles to stop stretching, and work against the opposing force causing the muscle stretch 
- The spinal circuit will regulate the input to the muscle spindle

Spinal Cord and Automatic Response 

- Rhythmic movements (ex. beating wings, swinging legs) are described as the more complex movements compared to the automatic response
- The central pattern generator is a type of neural circuitry is responsible for this type of movement
- This circuitry is generated by the spinal cord, and is activated/ regulated by the brain 

Spinal Cord and Rhythmic Movements

Spinal cord injuries disrupt the communication pathway between the brain and the body. When a specific segment of the spinal cord is damaged, all segments below the point of injury are disconnected from the brain, leading to paralysis. The nature of the paralysis and reflex activity can vary; complete severance may cause flaccid paralysis and a loss of reflexes, whereas injuries where the tissue remains intact can lead to abnormally strong reflexes due to the loss of inhibitory signals from the brain.

Spinal Cord Injuries

- Motor neurons control the beginning, end, and organization of muscle movement  
- The spinal cord is involved in motor neuron input
- Therefore, in order to understand how movement is coordinated, the spinal cord's organization (as well as ways in which its disrupted/ how it interacts with the brain) must be understood

Smith College

- Behavioral view of reflexes
- Control systems for accuracy vs speed
- Spinal cord's role in controling body movement
- Motor cortexes
- Extrapyramidal systems role in motor commands
- Brain disorders and motor impairments

Motor Control 

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

- Our motor cortices help to facilitate the movements of our body in different ways
- There are two motor cortices: 
- Primary Motor Cortex (referred to as M1) 
- Nonprimary motor cortex (which contains the premotor cortex and the supplementary motor area), is anterior to M1 

Motor Cortices

- A motor system that goes from the forebrain to the spinal cord and brainstem
- Includes the basal ganglia and cerebellum (structures of the brain)
- These structures send messages to the spinal cord through the reticulospinal tract and the rubrospinal tract

Extrapyramidal System 

Alzheimer's disease is a specific type of dementia characterized as an irreversible, progressive brain disorder, which is understood to have a genetic basis. It gradually destroys memory and cognitive skills, eventually impairing the ability to perform simple tasks like walking, talking, and eating. This severe cognitive decline is associated with the formation of plaques in the brain resulting from cell death.

Alzheimer's Disease

- When thinking about how a behavior is initiated, researchers have questioned whether it is reflexive (meaning it is caused by a chain of events without intentionality) or planned (which is defined by a motor plan)

Sequence of Initiating Behavior 

- Similarly to engineering, in order to control movement, the body must take into account two needs: accuracy and speed 
- Two types of control mechanisms (closed and open loop) are able to prioritize one of these needs when controlling movement 

Control Systems for Movement 

Spinal Cord in Controlling Body Movement

- Movement disorders can be caused by disorders of the brain, including the cerebellum, basal ganglia, and cortex

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