Chapter 25 - Muscle Relaxants

Extrapyramidal Tract

- Cells from the Cortex and Subcortical areas including: * Basal Ganglia * Cerebellum - Coordinate unconsciously controlled/involuntary muscle activity - Allows he body to make automatic adjustment in posture or position and balance

Pyramidal Tract

- Located in the Cerebellum - Fibers within the CNS that control precise, intentional movement

Basal Ganglia

- Lower area of the brain - Associated with coordination of unconscious muscle movements that involve movement and position

Cerebellum

- Lower portion of the brain - Associated with coordination of muscle movements including: * Voluntary motion * Extrapyramidal control of unconscious muscle movements

Brain Control

- Many areas within the brain influence the spinal motor nerves * Brainsem * Basal Ganglia * Cerebellum modulate spinal motor nerve activity and help to coordinate activity among various muscle groups, allowing coordinated movement and control of body muscle motions

Spindle Gamma Loop System

- Simple reflex arcs that involve sensory receptors in the periphery that respond to stretch and spinal motor nerves and cause muscle contraction - Responsible for maintaining muscle tone and keeping an upright position against the pull of gravity

Spasticity

- Sustained muscle contractions

Muscle Spasticity

- The result of damage to neurons within the CNS rather than injury to peripheral structures - May result from an increase in excitatory influences or a decrease in inhibitory influences within the CNS

Spinal Reflexes

- The simplest nerve pathways that monitor movement and posture - Can be simple, involving an incoming sensory neuron and an outgoing motor neuron, or more complex, involving interneurons that communicate with the related centers in the brain

Nerves Within The Cerebral Cortex

Allow conscious, or intentional movement

Direct-Acting Skeletal Muscle Relaxants

Enter the muscle to prevent muscle contraction directly Used to relieve the effects of muscle spasm - Botulinum Toxin type A - botulinum Toxin type B - Incobotulinumtoxin A - Dantrolene

Muscle or Skeletal Damage

May send a multitude of stimuli to the spinal cord and result in muscle spasms or extended contraction

Interneuron

Neuron in the CNS that communicates with other neurons, not with the muscles or glands

Muscle Spasms

Often result from injury to the musculoskeletal system i.e. overstretching a muscle, wrenching a joint, tearing a tendon or ligament - Believe they are caused by the flood of sensory impulses coming to the spinal cord from the injured area

Movement and Muscle Control

Regulated by spinal reflexes and the upper CNS, including * Basal Ganglia * Cerebellum * Cerebral Cortex

Nerves Within The Cortex

Send signals down the spinal cord where they cross to the opposite side of the spinal cord before sending out nerve impulses to cause muscle contraction

Hypertonia

State of excessive muscle response and activity

Centrally Acting Skeletal Muscle Relaxants

Work in the CNS to interfere with the reflexes that are causing the muscle spasm They lyse or destroy spasm Referred to as Spasmolytics Cause Central CNS Depression - Baclofen - Carisoprodol - Chlorzoxazone - Cyclobenzaprine - Metaxalone - Methocarbamol - Orphenadrine - Tizanidine