Flashcards in Spinal Cord and PNS: Motor Pathways Deck (14):
What are the 2 descending pathways for SOMATIC MOTOR NEURONS?
1) DIRECT DESCENDING PATHWAY FOR FINE MOTOR CONTROL
2) INDIRECT PATHWAY TO REGULATE MUSCLE TONE
Explain DIRECT DESCENDING PATHWAY FOR FINE MOTOR CONTROL
- Starts in PRIMARY MOTOR CORTEX
- Voluntary control
- 85% of fibers cross over at MEDULLA OBLONGATA
- 15% cross over in SPINAL CORD
- One MOTOR NEURON releases Acetylcholine (Ach)
- Stimulates SKELETAL MUSCLE
Explain INDIRECT PATHWAY TO REGULATE MUSCLE TONE
- Starts in MIDBRAIN
- Involuntary control
- One MOTOR NEURON releases Ach
- Maintains SKELETAL MUSCLE tone
What do SOMATIC MOTOR NEURONS descend from the BRAIN via?
LATERAL and ANTERIOR WHITE COLUMNS
Where do SOMATIC MOTOR NEURONS synapse with MOTOR NEURONS?
The ANTERIOR GREY HORN
Where do MOTOR AXONS exit the SPINAL CORD?
First the VENTRAL ROOT, then either the DORSAL RAMUS or the VENTRAL RAMUS
If a MOTOR AXON exits through DORSAL RAMUS, where is it going?
To the back muscles
Baby got BACK ;)
If a MOTOR AXON exits through the VENTRAL RAMUS, where is it going?
to SKELETAL MUSCLES of ventrolateral body wall and the limbs
Can both SYMPATHETIC (S) and PARASYMPATHETIC (PS) divisions excite and inhibit?
Yes, yes they can.
Can the *same* NEUROTRANSMITTER excite or inhibit?
Yes, yes it can.
Where do most target organs receive info from?
PS and S divisions
What is DUAL INNERVATION?
Receiving from PS *and* S
What are the effects of DUAL INNERVATION?
- Antagonistic on same cells: e.g. S inc / PS dec. rate of pacemaker cells firing
- On antagonistic muscles: e.g. S stimulates pupillary dilators, PS stimulates pupillary constrictors
- Cooperative, affecting different cells of the same gland: e.g. in salivary gland, S stimulates mucous secretion, PS stimulates watery secretion