lower motor neurons

Question 1

where are LMN located

Answer 1

ventral horn

Question 2

how is skeletal muscle contraction initiated

Answer 2

by LMN in spinal cord

Question 3

where do LMN send axon

Answer 3

skeletal muscle

Question 4

What is the LMN known as

Answer 4

final common pathway for transmitting into to skeletal muscle

Question 5

medial part spinal cord controls what

Answer 5

posture and locomotion
-interneurons cover segments vertically
- bilateral

Question 6

what does basal ganglia do

Answer 6

prevent from initiating unwanted movement, prepare motor circuits for initiation of movements, and reg transition between patterns of diff movement

Question 7

disorders of basal ganglia

Answer 7

huntingtons and parkinsons

Question 8

characteristics of LMN

Answer 8

-Each lower motor neuron innervates muscle
fibers in a single muscle
-Grouped together in motor neuron pool
- Columnar organization
-LMNs in ipsilateral ventral horn

Question 9

lateral spinal cord controls what

Answer 9

fine movement in distal extremities
- interneurons in in lateral part-strictly local
- bilateral

Question 10

what does cerebellum do

Answer 10

• detects difference between intended movement and movement preformed
• real time and long-tern reduction in motor errors

Question 11

what does damage to cerebellum

Answer 11

incoordination with errors and no control like ataxia

Question 12

two types of LMNs

Answer 12

a motor neuron and y motor neuron

Question 13

what is a (alpha) motor neuron

Answer 13

• innervates extrafusal muscle
  -force-producing muscle fibers that generate force for posture and movement

Question 14

what is y(gamma) motor neuron

Answer 14

innervate intrafusal muscle fibers( spindles)

Question 15

characteristics of a motor neuron

Answer 15

• single a motor neuron innervates multiple muscle fiber
• spread across evenly across muscle to reduce chance of one a motor neuron results in loss of muscle function
• AP generates contration

Question 16

what are three types od a motor neuron

Answer 16

*slow (S) (e.g. posture)
* fast fatigue-resistant (FR) (walking)
* fast fatigable (FF) (jumping)

Question 17

characteristics of fast fatigable

Answer 17

big size threshold, force and fast conduction and fatigue

Question 18

characteristics of fast fatigue-resistant (FR)

Answer 18

medium size, threshold, conduction, fatigue, and force

Question 19

slow

Answer 19

small size threshold, conduction, force and fatigue

Question 20

Group Ia & Group II afferents

Answer 20

Largest axons in peripheral nerves → fast

Question 21

characteristics of group 1a

Answer 21

fastest and biggest, coiled around middle region, sensitive to movements and fast changes, respond quick to small rapid stretch

Question 22

characteristics of group II afferents

Answer 22

signal level of sustained stretch and fire continuously at rate proportional to the degree of stretch,

Question 23

Ia afferent activity is dominated by what

Answer 23

signals transduced by
the dynamic subtype of nuclear bag fiber,

Question 24

group II afferents innervate what

Answer 24

static nuclear bag fibers and the nuclear chain
fibers

Question 25

explain what happens when you are holding cup and a drink is added

Answer 25

1. group II sustains the stretch of holding the cup 2. Adding the drink activates 1a afferents bc there is change in stretch quickly 3. a motor neuron inhibits antagonist muscle to get it back to where it started

Question 26

Explain the myotatic reflex( knee jerk response)

Answer 26

1. hammer stretches tendon which stretch sensory receptors in leg extensor muscles trigger 1a afferents 2. motor neurons get excited which excites interneurons and then inhibits flexor muscle 3. leg extends

Question 27

what does the myotatic reflex do

Answer 27

helps maintain posture and balance, allowing one to walk without consciously thinking about each step

Question 28

what do y- motor neurons do

Answer 28

γ-motor neurons modulate the excitability of muscle spindles - for more precise movements like threading a needle - for more general movements like standing/walking it doesn't fire as much

Question 29

where is golgi tendon organ located

Answer 29

between a muscle and a tendon

Question 30

how is each GTO innervates

Answer 30

by a single group Ib sensory axon