1. NEURAL CONTROL of Skeletal Muscles

2. KNOW THESE terms

3. Two major descending fiber tracts control skeletal muscle: pyramidal tracts & extrapyramidal tracts
Chapter 8
Pyramidal tracts
voluntary
involuntary

5. Higher Motor Neuron Control of Skeletal Muscles
Black = extrapyramidal- primitive, slower
Red = pyramidal tracts
PARKINSON’S
EVOLVED

6. Somatic Motorneurons
A motor unit consists of a somatic motor neuron and the muscle fibers it innervates Whenever a somatic motor neuron is activated, all of the muscle fibers it innervates are stimulated to contract

7. Muscle Spindle Apparatus
sensory
See next slide for descriptions

8. Alpha motoneurons: innervate extrafusal (contracting) muscle fibers
Gamma motoneurons: innervate intrafusal (active stretch) muscle fibers
Contraction of these fibers results in isometric contraction and enhances the stretch reflex.
Provides enough tension during relaxation to maintain muscle tone.
Both types are stimulated by upper motor neurons at the same time - coactivation

9. Knee-Jerk Reflex
A monosynaptic reflex

10. Golgi Tendon Organ: this is a receptor that detects the amount of tension in the tendon. If tension is too great, the golgi tendon organ sends impulses that cause IPSPs and inhibit activity. This is a reflex.

11. Reciprocal Innervation
Collateral branches
simultaneously inhibit (IPSPs)
an antagonistic muscle.

12. Crossed Extensor Reflex: A type of double reciprocal innervation seen when you step on a tack
This is in the same level in the spinal cord.

13. REFLEXES TESTED IN NEUROLOGICAL EXAMS
--BABINSKI - Fanning of the toes when you stroke the heel. Indicates immaturity of nervous system – normal in newborns --biceps reflex – tapping inner elbow, should flex upward --triceps reflex – opposite
BABINSKI REFLEX
Click here for a video

14. Learned “conditioned” somatic motor reflexes
These are integrated at the level of the cerebral cortex Examples: voluntary control of urination/defacation, tying a shoelace, bicycling, swimming & skiing, driving a car

15. KNOW THESE terms ✪