Ch.13 Flashcards
Motor Endings
Integration for these activities is in the spinal cord, cortex, basal nuclei and cerebellum
Innervating Skeletal Muscle
Motor Endings
Somatic motor neurons release Ach, this
directly opens ion channels and muscle contracts
Innervating Smooth Muscle and Glands
Motor Endings
Autonomic motor neurons release either ACh or NE at varicosities –> indirectly causes ion channels to open and muscles to contract, glands to secrete
Reflex Activity
- rapid, predictable, involuntary, unlearned motor responses to stimuli
- protects body from harm
- important clinically
- reflexes coordinated in the brain (usually
brain stem) OR in the spinal cord - some you are aware of (somatic reflexes) because they involve skeletal muscle contraction – EX: like jerking your hand from a hot stove
OR - you may not be aware of (autonomic reflexes) - like dilation of pupils
Abnormal reflexes
indicate that the
nervous system is damaged
Patellar reflex
tap knee with hammar –> leg will extend
For skeletal muscles to perform normally:
- The Golgi tendon organs (proprioceptors) must constantly inform the brain as to the state of the muscle (gives info on tension)
- Stretch reflexes initiated by muscle spindles must maintain healthy muscle tone (gives info on length)
Muscle spindle
- Lack myofilaments
- Not contractile but receptive
Muscle Spindle Refex
- add load to muscle
- muscle and muscle spindle strech as arm drops
- reflex contraction inated by muscle spindle restores arm position
Golgli tendon relfex
- Keeps muscle from ripping off of bone
1. neuron from golgi tendon organ flies
2. MN inhibited
3. muscle relaxes
4. load released
Crossed extensor reflex
The crossed extensor reflex has two parts:
- The stimulated side is withdrawn –> Noxious stimulus: flexor reflex
- The contralateral side is extended –> Reciprocal activation: extensor muscles activated
Examples:
- Stepping on a piece of glass
- Being grabbed by someone
