Chapter 13 Flashcards Preview

Neuroanatomy > Chapter 13 > Flashcards

Flashcards in Chapter 13 Deck (41)
Loading flashcards...
1
Q

Hierarchical organization of motor network of spinal cord

A
Lowest to highest:
Spinal cord
Cerebellum
Basal ganglia
Motor cortex
2
Q

What are reflexes in the spinal cord controlled by

A

Midbrain

3
Q

What are the midbrain and spinal activity controlled by

A

Forebrain

4
Q

First level in regulation of sensorimotor functions

A

Spinal cord

5
Q

Dermatome

A

Area innervsted by afferent fibers of. Enron in single DRG

6
Q

Myotome

A

Muscles innervated by axons exiting cord via single ventral root

7
Q

LMN

A

Final common pathway for muscle activation

8
Q

Motor unit (4 components)

A

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

9
Q

Damage to LMN

A

Disruption of entire unit

Damage to axons branches weakening of the muscle

10
Q

Innervation ratio

A

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

1-3000 (gross)

11
Q

Temporal summation

A

Refers to increasing the rate of firing of individual motor units

12
Q

Spatial summation

A

Recruiting a greater number of motor units

13
Q

3 major fasciuli of white matter of spinal cord

A

Dorsal
Lateral
Ventral

14
Q

Dorsal

A

Ascending sensory

15
Q

Lateral

A

Ascending sensory and descending motor

16
Q

Ventral

A

Ascending sensory and descending motor

17
Q

Fasciculi

A

Bundles of longitudinal axons

18
Q

Descending tracts: corticospinal tracts

A

Originating from pyramidal cells (betz)

Precentral gyrus (primary motor, broadmann 4)

Premotor cortex (8)

Somesthetic (3,2,1)

Supplementary motor cortex (6)

19
Q

Lateral corticospinal trAct

A

Cortical control of skeletal muscles during skilled movements

20
Q

Anterior corticospinal tract

A

I crossed corticospinal eventually crossing before synapse for on motor neurons

21
Q

Extrapyramidal tracts

A

Tectospinal
Rubrospinal
Vestibulospinal

22
Q

Tectospinal

A

Regulation of neck and body movements for startle reflexes

23
Q

Rubrospinal

A

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

24
Q

Vestibulospinal

A

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

25
Q

Reticulospinal tract

A

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

26
Q

Fasciculi gracious and cuneatus

A

Ascending

Discrimitive touch and vibration from lower and upper halves
Of body

27
Q

Lateral sponothalamic tract

A

Mediation of pain and temperature

28
Q

Spinocerebellar tract

A

Ascending

Unconscious propriception from muscles of extremities and limbs

29
Q

Alph motor neurons

A

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

30
Q

Extrafusal fibers

A

Contractile elements of skeletal muscles

31
Q

Gamma motor neurons

A

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

32
Q

Firing of gamma motor neuron (efferent)

A
  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
33
Q

Internuerons

A

Numerous specialized cells

Integration of sensory and motor functions of CNS

34
Q

Renshaw cells

A

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

35
Q

Reflex response

A

Stereotypes movement to sensory stimulation

36
Q

Neuronal circuitry

A
Muscle spindles
Afferebt fibers
Alpha motor fibers
Efferent fibers
Reflexive contraction of muscle fibers
37
Q

Gamma motor neurons

A

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

38
Q

Muscle spindles

A

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
39
Q

Golgi tendon organs

A

Sensitive to degree of muscle tension during contraction

Reflexive inhibitor for preventing muscle damage

Prevent excessive contractions

Regulate motor neurons via interneurons

40
Q

Two types of afferent spindles

A

Type IA: fast conduction fibers

Type II: slow conducting fibers

41
Q

Intrafusal fibers are divided into

A

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