RUSVM Physio Neuro Part 8 Motor System and Reflex Arch

Question 1

What is the spinal cord protected by

Answer 1

The Vertebral column

Question 2

The spinal cord is anatomically divided into what

Answer 2

Peripheral white matter and central grey matter

Question 3

Dorsal root (horn) of the grey matter is related to what system?

Answer 3

The sensory NS

Question 4

The ventral root (horn) of the grey matter is related to what system

Answer 4

The motor NS

Question 5

What are the 5 fundamental components of the arc reflex (Learning objective)

Answer 5

1. A receptor
2. A sensory neuron
3. One or more synapses in the CNS
4. A motor neuron
5. a target organ

Question 6

What is called a reflex in which the reflex arc passes through only a small segment of the spinal cord or a small rostrocaudal region of the brainstem
ex= stretch reflex or pupillary reflex.

Answer 6

Segmental reflex

Question 7

What is called the reflex arc that transverses many segments of the spinal cord or several major brain divisions

Answer 7

Intersegmental reflex

Question 8

What are the two main components of the motor system

Answer 8

Upper Motor Neuron (UMN) and Lower Motor Neuron (LMN)

Question 9

What are the two types of muscle fibers of the motor neurons

Answer 9

Extrafusal fibers and intrafusal fibers

Question 10

Extrafusal fibers are innervated for what neurons

Answer 10

The Alpha Motor Neurons (give rise to A alpha fibers)

Question 11

Intrafusal fibers are innervated by what neurons

Answer 11

by Gamma motor neurons (give rise to alpha gamma fibers)

Question 12

What two important muscle receptors provide the CNS with information

Answer 12

Muscle spindle and Golgi tendon organ.

Question 13

Posture and movement depend on a combination of what

Answer 13

Voluntary actions controlled by higher brain centers and involuntary reflexes coordinated by the spinal cord.

Question 14

What is defined as a single motorneuron and the muscle fibers that it innervates

Answer 14

A motor unit

Question 15

T/F Each motor unit has a unique contractile force determined by the number of muscle fibers it innervates

Answer 15

TRUE

Question 16

T/F The muscle spindle middle part is innervated by sensory neurons and carry action potentials from the spindle to the CNS

Answer 16

True

Question 17

T/F the contractile part of the muscle spindle is not innervated by gamma motor neurons

Answer 17

False- they are innervated by gamma motor neurons

Question 18

What are the motor systems 3 main functions (Learning objective)

Answer 18

1. Maintain posture and provide a stable platform for movement (somatic)
2. Controls vol. movement and locomotion (somatic)
3. Controls visceral motor function (Visceral)

Question 19

Describe Upper Motor Neuron (UMN) (learning objective)

Answer 19

• Completely contained in the CNS (aka central motor neuron)
• Cell body is located in a motor nucleus of the brain stem or the motor cortex of the forebrain
• THEIR AXONS CONNECT TO LOWER MOTOR NEURONS (either synapsing on them directly or indirectly via interneurons) INTERNEURONS ARE BIPOLAR 1 AXON 1 DENDRITE AND THEY INTERCONNECT VARIOUS NEURONS W/ BRAIN AND SPINAL CORD.
• Organize and direct the activity of LMN’s

Question 20

Describe Lower Motor Neurons (LMN) (learning objective)

Answer 20

• They have their cell body in the CNS (brain or spinal cord)
• Their axons project into the PNS via cranial or spinal nerves.
• AKA peripheral neurons
• Autonomous NS have 2 LMN’s in series with the cell body of the second LMN located in a peripheral ganglion
• When stimulated LMNs induce muscle contraction

Question 21

What is an encapsulated group about 3 to 12 small, slender, specialized skeletal muscle fibers.

Answer 21

Muscle Spindle

Question 22

The contractile part of muscle spindles are innervated by what

Answer 22

Gamma Motor neurons

Question 23

What is the purpose of a muscle spindle

Answer 23

Are stretch receptors whose function is to correct for changes in muscle length

Question 24

How are action potentials generated along the spindle sensory neurons

Answer 24

Stretching the middle segment of the intrafusal muscle fibers generate AP’s along the spindle sensory neurons

Question 25

What is the simplest manifestation of muscle spindle function

Answer 25

the Muscle Stretch Reflex

Question 26

What does the golgi tendon organ help control

Answer 26

Helps control muscle tension

Question 27

When is the golgi tendon organ stimulated

Answer 27

stimulated when this small bundle of muscle fibers is tensed by contracting of stretching the muscle.

Question 28

What detects muscle tension reflected by the tension in itself.

Answer 28

Golgi tendon organ

Question 29

What provides the NS with instantaneous information on the degree of tension in each small segment of each muscle

Answer 29

Golgi tendon organ