Other Reflexes, Motor Hierarchy And Motor Cortex

Question 1

What is the stimulus of GTO reflex?

Answer 1

1. Increase active tension by isometrically contracted muscle
2. Increase passive tension by excessive stretch of muscle beyond physiologic limit

Question 2

GTO is arranged in …. To extrafusal fibers thus act as ….detectors

Answer 2

Series
Tension

Question 3

Afferent of GTO reflex is …..which synpases with …..in the spinal cord

Answer 3

Ib fibers
Inhibitory interneuron

Question 4

Mention function of inverse stretch reflex

Answer 4

1. Protection of muscles & tendons from damage caused by excessive tension
2. Equalize contractile force among muscle fibers. Those fibers that exert excess tension become inhibited by the reflex

Question 5

Golgi tendon organ is ….-synaptic

Answer 5

Bi

Question 6

Afferents of flexor withdrawal reflex

Answer 6

A-delta & C fibers pain afferents

Question 7

GR: Stepping on sharp object can cause hip flexion

Answer 7

Due to discharge of impulses in many afferents that spread excitatory impulses up and down to many segments if the spinal cord, producing greater response. This is known as irradiation

Question 8

…..describes a property which causes prolonged afterdischarge maintain muscle contraction in withdrawal reflex.

Answer 8

Reverberating circuits

Question 9

…..helps unopposed action of agonist muscle in withdrawal reflex

Answer 9

Reciprocal innervation

Question 10

Define extensor reflex

Answer 10

It is reflex contraction and extension of the limb, in response to application of painful stimulus to the opposite limb

Question 11

Afferents of extensor reflex synapses with …..

Answer 11

Intersegmental neuron

Question 12

In contrast to superficial reflexes, deep reflexes do NOT require intact ….

Answer 12

UMN

Question 13

The center for abdominal superficial reflexes is ….. for epigastric reflexes & ….for abdominal ones

Answer 13

T6-9
T9-12

Question 14

Mention the physiological & pathological conditions of +ve Babinski’s sign

Answer 14

Phys: deep sleep, general anesthesia, infants below 1 yr as pyramidal tract is not myelinated yet. Pseudo-positive Babniski sign
Path: deep comma, UMN lesion, leads to fanning of toes (area 6 damage) & dorsifoexion of thumb (area 4 damage)

Question 15

Define motor neuron pool

Answer 15

The group of AHCs that innervate a single muscle & may extend in several spinal segments

Question 16

Mention input sources for alpha motor neurons

Answer 16

1. Nerve endings if sensory neurons in dorsal ganglia
2. Interneurons
3. Projections from higher centers as brain stem

Question 17

The NT of Renshaw cell is …., it is activated by…..

Answer 17

Glycine
Collateral from the active alpha motor neuron which releases Ach to excite Renshaw cell

Question 18

Describe action of Renshaw cells

Answer 18

1. Negative feedback mechanism of active alpha motor neuron to prevent excess activity
2. Inhibit surrounding alpha motor neurons to focus motor activity and sharoen effect of active AMN
3. To localize response and prevent oscillation by inhibition of antagonist muscle

Question 19

Lesion of …. Results in loss of fine movements while that of …..results in weakness of gross movements

Answer 19

Area 4
Area 4 or 6

Question 20

In voluntary movements idea is initiated in ….., and converted into an initial decision in …..

Answer 20

Prefrontal cortex
Limbic association areas

Question 21

……evaluates body position by somatosensory, proproceptive & visual inputs.

Answer 21

Posterior association area (5,7)

Question 22

…..&…. decide which group of muscles will contract and the sequence of contractions

Answer 22

Premotor & supplmentary motor areas

Question 23

……&…..share in planning by sequencing & storage of movements

Answer 23

Basal ganglia
Neocerebellum

Question 24

Mention parts which are bilaterally represented in area 4

Answer 24

Respiratory & abdominal muscles & head muscles with exception of lower face & genioglossus

Question 25

Mention the part which is not inverted in representation

Answer 25

Head

Question 26

List connections of area 4

Answer 26

1. AHCs through corticospinal & corticobulbar tracts, main origin of pyramidal tract 2. Area 6 (premotor) 3. Neocerebellum of opposite side 4. Basal ganglia

Question 27

Compare dynamic & static Betz cells

Answer 27

Dynamic: discharge at start of voluntary movements for initiation & direction Static: discharge all through the voluntary movement for maintenance

Question 28

Functions of area 4

Answer 28

1. Initiate fine motor movements of distal muscles 2. Share in gross movements of proximal muscles with area 6 4. Facilitate stretch reflex 4. Necessary for superficial reflexes & normal plantar reflex

Question 29

Describe area 4 lesion

Answer 29

1. Loss of fine voluntary movement of 1 limb 2. Paresis of gross movement 3. Hypotonia and hyporeflexia 4. Loss of superficial reflexes 5. Partial +ve babniski sign (toe dorsiflexion)

Question 30

Describe connections of area 6

Answer 30

1. Sensory assocoation area 5,7 2. Primary motor area 3. Basal ganglia 4. Cerebellum 5. Supplementary motor area 6. To AHCs of spinal cord, through extra-pyramidal tract

Question 31

Function of area 6

Answer 31

1. Stores plan for fine skilled motor movements 2. Adjusts body posture to perform fine skilled motor movements 3. Initiate gross movements by proximal muscles esp externally directed ones 4. Inhibit grasp reflex but necessary for plantar reflex 5. Inhibit stretch reflex (muscle tone and tendon jerks) 6. Shares in planning motor movements with area 4 and supplementary motor area. 7. Together with basal ganglia regualted automatic subconscious associated movements.

Question 32

Describe effect of lesion of area 6

Answer 32

1. Paresis 2. Motor apraxia 3. Return of grasp reflex 4. Hypertonia and hyperreflexia 5. +ve babniski sign, fanning of toes 6. Loss of automatic associated movements

Question 33

F&L of area for hand skills

Answer 33

Controls complex skilled hand movements L, agraphia, hand movements become uncoordinated. There is inability to write or draw.

Question 34

F&L of eye movement area

Answer 34

F, gives cortico-nuclear tract of both sides which is responsible for voluntary conjugate deviation of both eyes to opposite side. L, causes loss of voluntary ability to produce conjugate eye movement but later the tectospinal tract compensates

Question 35

F&L of Motor speech area

Answer 35

F, stores complex orders of vocalization L, motor aphasia

Question 36

Describe the body representation of medial area 6

Answer 36

Horizontal amd biltaeral representation of body muscles

Question 37

Describe functions of medial area 6

Answer 37

1. Supplements area 6 in control of voluntary motor movements of proximal muscles esp internal directed movements as background for fine movements 2. It is involved in planning and programming of movememts sepcially complex bilateral movrments before they start

Question 38

Describe effect of lesion of medial area 6

Answer 38

Inability to perform complex movements Inability to direct and coordinate hands properly during bilateral hand movements

Question 39

Cerebral capillaries are ...... ex .....

Answer 39

Non-fenestrated Choroid plexus

Question 40

Blood supply of brain is ..... O2 supply is ....

Answer 40

750ml/min (54 ml/100gm/min) 14% 46 ml/min (3.3 ml/100gm/min) 18%

Question 41

CPP=.......

Answer 41

MAP - ICP

Question 42

Autoregulation if cerebral blood flow keeps it constant at range of .... MAP

Answer 42

50-150 mmHg

Question 43

Mention explanations for autoregulation

Answer 43

1. Myogenic property of cerebral blood vessels 2. Metabolic theory

Question 44

Define Monro-Kellie's doctrine

Answer 44

The volume of blood, spinal fluid and brain in the cranium (closed space in a solid skull) at any time must be relatively constant. So inc in ICP dec CBF amd vice versa.