Other Reflexes, Motor Hierarchy And Motor Cortex Flashcards
What is the stimulus of GTO reflex?
- Increase active tension by isometrically contracted muscle
- Increase passive tension by excessive stretch of muscle beyond physiologic limit
GTO is arranged in …. To extrafusal fibers thus act as ….detectors
Series
Tension
Afferent of GTO reflex is …..which synpases with …..in the spinal cord
Ib fibers
Inhibitory interneuron
Mention function of inverse stretch reflex
- Protection of muscles & tendons from damage caused by excessive tension
- Equalize contractile force among muscle fibers. Those fibers that exert excess tension become inhibited by the reflex
Golgi tendon organ is ….-synaptic
Bi
Afferents of flexor withdrawal reflex
A-delta & C fibers pain afferents
GR: Stepping on sharp object can cause hip flexion
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
…..describes a property which causes prolonged afterdischarge maintain muscle contraction in withdrawal reflex.
Reverberating circuits
…..helps unopposed action of agonist muscle in withdrawal reflex
Reciprocal innervation
Define extensor reflex
It is reflex contraction and extension of the limb, in response to application of painful stimulus to the opposite limb
Afferents of extensor reflex synapses with …..
Intersegmental neuron
In contrast to superficial reflexes, deep reflexes do NOT require intact ….
UMN
The center for abdominal superficial reflexes is ….. for epigastric reflexes & ….for abdominal ones
T6-9
T9-12
Mention the physiological & pathological conditions of +ve Babinski’s sign
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)
Define motor neuron pool
The group of AHCs that innervate a single muscle & may extend in several spinal segments
Mention input sources for alpha motor neurons
- Nerve endings if sensory neurons in dorsal ganglia
- Interneurons
- Projections from higher centers as brain stem
The NT of Renshaw cell is …., it is activated by…..
Glycine
Collateral from the active alpha motor neuron which releases Ach to excite Renshaw cell
Describe action of Renshaw cells
- Negative feedback mechanism of active alpha motor neuron to prevent excess activity
- Inhibit surrounding alpha motor neurons to focus motor activity and sharoen effect of active AMN
- To localize response and prevent oscillation by inhibition of antagonist muscle
Lesion of …. Results in loss of fine movements while that of …..results in weakness of gross movements
Area 4
Area 4 or 6
In voluntary movements idea is initiated in ….., and converted into an initial decision in …..
Prefrontal cortex
Limbic association areas
……evaluates body position by somatosensory, proproceptive & visual inputs.
Posterior association area (5,7)
…..&…. decide which group of muscles will contract and the sequence of contractions
Premotor & supplmentary motor areas
……&…..share in planning by sequencing & storage of movements
Basal ganglia
Neocerebellum
Mention parts which are bilaterally represented in area 4
Respiratory & abdominal muscles & head muscles with exception of lower face & genioglossus
Mention the part which is not inverted in representation
Head
List connections of area 4
- AHCs through corticospinal & corticobulbar tracts, main origin of pyramidal tract
- Area 6 (premotor)
- Neocerebellum of opposite side
- Basal ganglia
Compare dynamic & static Betz cells
Dynamic: discharge at start of voluntary movements for initiation & direction
Static: discharge all through the voluntary movement for maintenance
Functions of area 4
- Initiate fine motor movements of distal muscles
- Share in gross movements of proximal muscles with area 6
- Facilitate stretch reflex
- Necessary for superficial reflexes & normal plantar reflex
Describe area 4 lesion
- Loss of fine voluntary movement of 1 limb
- Paresis of gross movement
- Hypotonia and hyporeflexia
- Loss of superficial reflexes
- Partial +ve babniski sign (toe dorsiflexion)
Describe connections of area 6
- Sensory assocoation area 5,7
- Primary motor area
- Basal ganglia
- Cerebellum
- Supplementary motor area
- To AHCs of spinal cord, through extra-pyramidal tract
Function of area 6
- Stores plan for fine skilled motor movements
- Adjusts body posture to perform fine skilled motor movements
- Initiate gross movements by proximal muscles esp externally directed ones
- Inhibit grasp reflex but necessary for plantar reflex
- Inhibit stretch reflex (muscle tone and tendon jerks)
- Shares in planning motor movements with area 4 and supplementary motor area.
- Together with basal ganglia regualted automatic subconscious associated movements.
Describe effect of lesion of area 6
- Paresis
- Motor apraxia
- Return of grasp reflex
- Hypertonia and hyperreflexia
- +ve babniski sign, fanning of toes
- Loss of automatic associated movements
F&L of area for hand skills
Controls complex skilled hand movements
L, agraphia, hand movements become uncoordinated. There is inability to write or draw.
F&L of eye movement area
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
F&L of Motor speech area
F, stores complex orders of vocalization
L, motor aphasia
Describe the body representation of medial area 6
Horizontal amd biltaeral representation of body muscles
Describe functions of medial area 6
- Supplements area 6 in control of voluntary motor movements of proximal muscles esp internal directed movements as background for fine movements
- It is involved in planning and programming of movememts sepcially complex bilateral movrments before they start
Describe effect of lesion of medial area 6
Inability to perform complex movements
Inability to direct and coordinate hands properly during bilateral hand movements
Cerebral capillaries are …… ex …..
Non-fenestrated
Choroid plexus
Blood supply of brain is …..
O2 supply is ….
750ml/min (54 ml/100gm/min) 14%
46 ml/min (3.3 ml/100gm/min) 18%
CPP=…….
MAP - ICP
Autoregulation if cerebral blood flow keeps it constant at range of …. MAP
50-150 mmHg
Mention explanations for autoregulation
- Myogenic property of cerebral blood vessels
- Metabolic theory
Define Monro-Kellie’s doctrine
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.
