Spinal Cord and PNS: Motor Pathways Flashcards Preview

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Flashcards in Spinal Cord and PNS: Motor Pathways Deck (14):
1

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

2

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

3

Explain INDIRECT PATHWAY TO REGULATE MUSCLE TONE

- Starts in MIDBRAIN
- Involuntary control
- One MOTOR NEURON releases Ach
- Maintains SKELETAL MUSCLE tone

4

What do SOMATIC MOTOR NEURONS descend from the BRAIN via?

LATERAL and ANTERIOR WHITE COLUMNS

5

Where do SOMATIC MOTOR NEURONS synapse with MOTOR NEURONS?

The ANTERIOR GREY HORN

6

Where do MOTOR AXONS exit the SPINAL CORD?

First the VENTRAL ROOT, then either the DORSAL RAMUS or the VENTRAL RAMUS

7

If a MOTOR AXON exits through DORSAL RAMUS, where is it going?

To the back muscles

Baby got BACK ;)

8

If a MOTOR AXON exits through the VENTRAL RAMUS, where is it going?

to SKELETAL MUSCLES of ventrolateral body wall and the limbs

9

Can both SYMPATHETIC (S) and PARASYMPATHETIC (PS) divisions excite and inhibit?

Yes, yes they can.

10

Can the *same* NEUROTRANSMITTER excite or inhibit?

Yes, yes it can.

11

Where do most target organs receive info from?

PS and S divisions

12

What is DUAL INNERVATION?

Receiving from PS *and* S

13

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

14

Do the ADRENAL MEDULLA, ARRECTOR PILI MUSCLES, SWEAT GLANDS, B.V. to SKELETAL MUSCLE receive DUAL INNERVATION?

No, they only receive S stimulation