Human Movement Systems: Nervous System Objectives

• After this presentation, the participant will be able to explain: – The Human Movement System – Nervous System Organization – Sensory, integrative and motor functions – Neurons – The role of vision, proprioception & vestibular systems in kinesthesia. – Common sensory receptors and their role in proprioception and movement.

Introduction

Human Movement System: • Movement is accomplished through the functional integration of three systems: the nervous, skeletal, and muscular systems. • These systems work in concert to produce motion (kinetic) or human movement. • All components must work together to produce sound movement; if one component is not working well, it will affect the others and cause kinetic chain impairments. Kinetic Chain

The kinetic chain • Kinetic means related to movement; chain refers to a system that is linked together or connected. • All components work together to manipulate human motion. • If one component of the kinetic chain is not working properly, it will affect the others and ultimately affect the movement.

Kinetic Chain

Nervous System Muscular System Skeletal System

. The nervous system is a communication network within the human body that allows us to gather information about our internal and external environments, process and interpret the information, and respond. . Its three primary functions are: • Sensory • Integrative

. Sensory: The ability of the nervous system to sense changes in either the internal or external environment. . Integrative: The ability of the nervous system to analyze and interpret the sensory information to allow for proper decision making, producing the appropriate response. . Motor: The neuromuscular response to the sensory information. The Nervous System

. Movement is a response to our sensory information and is, therefore, dictated by the nervous system. . This reflects the importance of training in a multisensory environment. . The most effective way to create positive long-term results in a client is to directly affect (properly train) his or her nervous system. Nervous System Organization Central Nervous System

The CNS consists of the brain and the spinal cord.

. Contains 12 cranial nerves and 31 pairs of spinal nerves (that branch out from the brain and spinal cord, respectively) as well as all sensory receptors. . Function: • Provide a connection for the nervous system to activate different bodily organs such as muscles (motor information). • Relay information from the bodily organs back to the brain, providing a constant update of the relation between the body and the environment (sensory information).

Two further subdivisions of the PNS include the somatic and autonomic nervous systems: • The somatic nervous system consists of nerves that serve the outer areas of the body and skeletal muscle and are largely responsible for the voluntary control of movement. • The autonomic nervous system supplies neural input to the involuntary systems of the body. • The autonomic system is further divided into the sympathetic (activity state) and parasympathetic (recovery state).

The Neuron

. The functional unit of the nervous system is known as the neuron. . Neurons are composed of three main parts: • Cell body: Cell organelles (nucleus, mitochondria, lysosomes, and Golgi complex) • Axon: Provides communication from the brain or spinal cord to other parts of the body • Dendrites: Responsible for gathering information from other structures of the body Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins The Neuron

There are three main functional classifications of neurons determined by the direction of their nerve impulses: • Sensory: Transmits afferent nerve impulses from receptors to the brain or spinal cord • Motor: Transmits efferent nerve impulses from the brain or spinal cord to the effector sites, such as muscles or organs • Interneuron: Transmits nerve impulses from one neuron to another

Proprioception

. The body’s ability to sense the relative position of adjacent parts of the body. . Training the body’s proprioceptive abilities will improve balance, coordination, and posture and enable the body to adapt to its surroundings without consciously thinking about movement. . Thus, it becomes important to train the nervous system efficiently to ensure proper movement patterns, which enhances performance and decreases the risk of injury. Sensory Receptors . Specialized structures located throughout the body, designed to transform environmental stimuli (heat, light, sound, taste, and motion) into sensory information that the brain or spinal cord can interpret to produce a response: – Mechanoreceptors respond to mechanical forces (touch and pressure). – Nociceptors respond to pain (pain receptors). – Chemoreceptors respond to chemical interaction (smell and taste). – Photoreceptors respond to light (vision). • For relevance to this course, we will focus attention on the mechanoreceptors. Mechanoreceptors

. Muscle spindle: Sensitive to change in length and rate of length change in muscle. . Golgi tendon organ: Sensitive to changes in muscular tension and rate of tension change. . Joint receptors: Respond to pressure, acceleration, and deceleration of the joint.

Reflexes: Stretch Reflex

Muscle spindles . Sensory receptors (called intrafusal fibers) lie parallel to the muscle fibers. . Receptors responds to change in length and rate of change in length of the muscle. . Reflexive response causes contraction of the agonists. . Causes stretch reflex, generally due to excessive rate of change in muscle length.

17 Reflexes: GTO Golgi tendon organs . Sensory receptors located in the muscle-tendon junction . Responds to muscle tension. . Reflexive action causes inhibition of agonist (a.k.a. autogenic inhibition). . Due to perception that tension puts the tendon at risk (i.e. could rupture the muscle from the bone) 18 Neurological Properties of Stretching Autogenic inhibition: the activation of a Golgi tendon organ (GTO) inhibits muscle spindle response . Initially, a low-force, long-duration (static) stretch stimulates low- grade muscle spindle activity and temporarily increases muscle tension. . Muscle spindles become desensitized as the stretch continues. . After 7 to 10 seconds, the increase in muscle tension activates the GTO response, inhibiting muscle spindle activity and allowing further muscle stretching. . Holding the stretch beyond 10 seconds stresses the collagen fibers, causing plastic deformation and lengthening the tissue (creep). . When the stretch ends, muscle spindles reestablish their threshold. Neurological Properties of Stretching (cont.) Reciprocal inhibition . Active stretching: the muscle on one side of a joint (i.e., the agonist) coincides with neural inhibition of the opposing muscle on the other side of the joint (i.e., the antagonist) to facilitate movement. . Example: While performing a supine hamstring stretch, contraction of the hip flexor muscles on the leg being stretched will produce more active hip flexion, resulting in reciprocal inhibition of the hamstring muscle group, allowing them to be stretched further. Physical Activity and the Nervous System

. Early stage improvements to physical activity are largely due to changes in the way the CNS and PNS coordinate movement. . Unsuccessful activity can be modified with sensory input to improve performance. . Understanding the importance of neural input can also help clients achieve appropriate flexibility by utilizing some general neurological principle so to enhance range of motion.