Chapter 13

Question 1

Hierarchical organization of motor network of spinal cord

Answer 1

Lowest to highest:
Spinal cord
Cerebellum
Basal ganglia
Motor cortex

Question 2

What are reflexes in the spinal cord controlled by

Answer 2

Midbrain

Question 3

What are the midbrain and spinal activity controlled by

Answer 3

Forebrain

Question 4

First level in regulation of sensorimotor functions

Answer 4

Spinal cord

Question 5

Dermatome

Answer 5

Area innervsted by afferent fibers of. Enron in single DRG

Question 6

Myotome

Answer 6

Muscles innervated by axons exiting cord via single ventral root

Question 7

LMN

Answer 7

Final common pathway for muscle activation

Question 8

Motor unit (4 components)

Answer 8

Motor neuron (cell body)
Efferent fibers
Motor end plate
Innervated muscle fibers

Question 9

Damage to LMN

Answer 9

Disruption of entire unit

Damage to axons branches weakening of the muscle

Question 10

Innervation ratio

Answer 10

Number of muscle fibers per axon 1-30 (fine)

1-3000 (gross)

Question 11

Temporal summation

Answer 11

Refers to increasing the rate of firing of individual motor units

Question 12

Spatial summation

Answer 12

Recruiting a greater number of motor units

Question 13

3 major fasciuli of white matter of spinal cord

Answer 13

Dorsal
Lateral
Ventral

Question 14

Dorsal

Answer 14

Ascending sensory

Question 15

Lateral

Answer 15

Ascending sensory and descending motor

Question 16

Ventral

Answer 16

Ascending sensory and descending motor

Question 17

Fasciculi

Answer 17

Bundles of longitudinal axons

Question 18

Descending tracts: corticospinal tracts

Answer 18

Originating from pyramidal cells (betz)

Precentral gyrus (primary motor, broadmann 4)

Premotor cortex (8)

Somesthetic (3,2,1)

Supplementary motor cortex (6)

Question 19

Lateral corticospinal trAct

Answer 19

Cortical control of skeletal muscles during skilled movements

Question 20

Anterior corticospinal tract

Answer 20

I crossed corticospinal eventually crossing before synapse for on motor neurons

Question 21

Extrapyramidal tracts

Answer 21

Tectospinal
Rubrospinal
Vestibulospinal

Question 22

Tectospinal

Answer 22

Regulation of neck and body movements for startle reflexes

Question 23

Rubrospinal

Answer 23

Regulation of muscle tone for limb extension against gravity

Originates in red nucleus

Fibers cross midline after leaving red nucleus and continue down spinal cord

May assist pyramidal system in controlling voluntary movements

Inhibits extensively alpha and gamma motor neurons

Facilitates flexor muscles and inhibits extensor muscles

Question 24

Vestibulospinal

Answer 24

Regulation of body adjustment to stabilize head

Originates in vestibular apparatus in ear

Courses through pins, medulla

Terminates at spinal cord

Helps body maintain posture and balance

Facilitates activity of extensor muscles

Inhibits activity of flexor muscles

Question 25

Reticulospinal tract

Answer 25

Reticular formation Fibers terminate on gamma motor neurons Influences on spinal nerves Maintains upright posture Allows some voluntary and gross motor movements Reticular formations and reticulospinal tract dontakl built in reflective motor patterns

Question 26

Fasciculi gracious and cuneatus

Answer 26

Ascending Discrimitive touch and vibration from lower and upper halves Of body

Question 27

Lateral sponothalamic tract

Answer 27

Mediation of pain and temperature

Question 28

Spinocerebellar tract

Answer 28

Ascending Unconscious propriception from muscles of extremities and limbs

Question 29

Alph motor neurons

Answer 29

9-16um 1 alpha neuron for about 200 muscle fibers Rapid impulse conduction Innervation of extrafusal fibers of muscles Voluntary and reflexive movements of head, trunk, and extremities

Question 30

Extrafusal fibers

Answer 30

Contractile elements of skeletal muscles

Question 31

Gamma motor neurons

Answer 31

Greater in number with small diameter Slow impulse conduction Regulation of spindle fibers length modulating excitation of annulospiral sensory primary endings Regulation of stretch reflex muscle tone

Question 32

Firing of gamma motor neuron (efferent)

Answer 32

1. Shortening is detected by sensory receptors 2. Detection is directed back to spinal cord and synapses with alpha motor neuron 3. Alpha motor neuron directs impulses back to extrafusal fibers 4. Extrafusal fibers contract until they are the same length as the muscle spindles

Question 33

Internuerons

Answer 33

Numerous specialized cells Integration of sensory and motor functions of CNS

Question 34

Renshaw cells

Answer 34

Capable of inhibiting alpha motor neurons Produces a negative feedback response Turns off alpha motor neuron after it fires and prepares to fire again 30x as many interneurons and motoneurons

Question 35

Reflex response

Answer 35

Stereotypes movement to sensory stimulation

Question 36

Neuronal circuitry

Answer 36

``` Muscle spindles Afferebt fibers Alpha motor fibers Efferent fibers Reflexive contraction of muscle fibers ```

Question 37

Gamma motor neurons

Answer 37

Innervate muscle spindles (intrafiaal fibers) Slower conduction than alpha Primary role is to regulate length of spindle fibers Controlled by brainstorm, Rec formation, and vestibular system Gamma efferent leave through ventral nerve root, contract end portions of intrafusal fibers, attach central part of muscle spindles

Question 38

Muscle spindles

Answer 38

Specialized receptors to detect degree and rate of muscle length change Consists of intrafusal fibers (3-5 specialized) If stretched, sends impulses in the afferent fiber from the spindle Afferent pulses travel to alpha-motor neurons via large diameter Result is contraction of muscles

Question 39

Golgi tendon organs

Answer 39

Sensitive to degree of muscle tension during contraction Reflexive inhibitor for preventing muscle damage Prevent excessive contractions Regulate motor neurons via interneurons

Question 40

Two types of afferent spindles

Answer 40

Type IA: fast conduction fibers Type II: slow conducting fibers

Question 41

Intrafusal fibers are divided into

Answer 41

Nuclear bag: Many nuclei Central portion innervsted by IA fibers Mediate dynamic responses Nuclear chain: Fewer nuclei Central portion innervated by IA, end portions by II fibers Mediate static responses