Functions Of Reticular Formation

Question 1

PRF is located in…….

Answer 1

Midbrain & pons

Question 2

Describe functions of ascending & descending fibers of PRF

Answer 2

A, go first to thalamus (intralaminar & reticular nuclei) which, in turn, project diffusely & non-specifically to almost all parts of cerebral cortex, responsible for arousal
D, increasing antigravity muscle tone

Question 3

The activity of reticukar excitatory area is inhibited by…….

Answer 3

Reticular inhibitory area, inhibitory areas of cerebral cortex, paleocerebellum, basal ganglia (the same activate inhibitory reticulat formation)

Question 4

Functions of medullary reticular nuclei

Answer 4

Decrease brain activity (inhibits PRF)
Decreasing antigravity muscle tone

Question 5

Mention factors stimulating RAS

Answer 5

Sensory signals that enter the brain from periphery esp pain
Signals from cerebral cortex
Analeptic & symoathomimetic
Stress
Caffeine
Thyroid hormone

Question 6

Mention factors inhibiting RAS

Answer 6

Lack of sensory input signals
Signals from sleep centers
General anesthesia
Damage by tumour/vascular lesion

Question 7

Enumerate functions of reticular formation

Answer 7

1. It is a vital link between higher centers in brain & lower centers in spinal cord
2. Maintain posture & equilibrium and muscle tone (cont. facilitatory impulses from reticular formation & vestibular nuclei)
3. Arousal & consciousness
4. RF contains vital centers for heart rate, blood pressure, respiration & many digestive activities
5. Pain modulation (raphe magnus nucleus)
6. REM sleep

Question 8

Compare 1ry & 2ry evoked potential

Answer 8

1ry, in the form of a +ve wave followed by a -ve wave, recorded from specific area of the brain (localised)
2ry, follows the 1ry evoked potentials & consists of large prolonged +ve wave, not localised, due to activation of cortical neurons by impulses arriving from non-specific thalamic nuclei

Question 9

Mention uses of evoked potentials

Answer 9

Mapping of brain areas
Diagnosis of diseases

Question 10

EEG is a measure of……

Answer 10

The summation of polysynaptic potentials of neurons in cerebral cortex

Question 11

Describe conditions of performing EEG

Answer 11

In a calm room with comfortable temperature & the person should be in complete physical & mental rest

Question 12

Compare alpha and beta waves

Answer 12

A, waves of adult, awake, relaxed person with closed eyes, recorder from occipital, parietal and frontal regions, amp 50 um, Frq 8-13 cycles/sec.
B, waves of awake person with open eyes, recorded from parietal and fronta regions, amp 25 um, frq 13-30 cycles/sec.

Question 13

Compare theta and delta waves

Answer 13

T, It is wave of children and adults during light sleep and emotional stress, recorded from temporal and parietal regions, amp 100 um, frq 4-7 cycles/sec.
D, it is the wave of deep sleep, infants and in cases of brain damage and surgical anesthesia, recorded from all cortical areas, amp 100 um, frq 3.5 cycles/sec

Question 14

Describe gamma waves

Answer 14

It is the wave of hyperaroused, higher mental activity and processing of complex tasks, it is recorded from all cortical areas, amp 0.5-2 uv, frq 30-80 Hz

Question 15

Value of EEG

Answer 15

Non invasive test for brain func
Localization of tumours
Monitor sleep stages and diagnose disorders
Diagnose epilepsy
Indicates brain death

Question 16

GR, occurrence of alpha block

Answer 16

Stimulation of ascending reticular activating system

Question 17

Mention functions of sleep

Answer 17

1. Provides brain with time to restore biochemical & physiological processes that have progressively decreased during wakefulness? Congition, metabolic-caloric balance, thermal equilibrium, immune competence
2. Facilitation of learning & memory
3. Neural maturation

Question 18

Importance of NREM sleep is….., …..is released during it & ….activity is increased.

Answer 18

Physical rest
Growth hormone
Parasympathetic

Question 19

In NREM, threshold for arousal is….., while in REM it is….

Answer 19

Low
High

Question 20

REM is important for……, with increased…..activitu

Answer 20

Mental rest
Sympathetic

Question 21

Mention two phenomena occuring in REM & another 2 in NREM

Answer 21

R, teeth gringing & penile erection
N, sleep walking & talking

Question 22

Mention type of wave in REM

Answer 22

Rapid irregular low voltage B waves (desynchronized beta rhythm)

Question 23

Describe waves of Stage 2

Answer 23

Sleep spindles (bursts of large alpha waves 12-24 Hz) and K complexes (large & slow potetial) are seen within theta waves

Question 24

First NREM sleep lasts for……, there is less……and more…..towards the morning

Answer 24

Average 90 min
stage 3 & 4 sleep
REM

Question 25

Compare passive & active theories of sleep

Answer 25

P, The RAS is simply fatigued during waking day and become inactive as a result
A, sleep is caused by stimulation of several specific areas of the brain (sleep centers)

Question 26

Mention centers that lead to REM & NREM

Answer 26

NREM, Anterior hypothalamus &adjacent basal forebrain area
REM, reticular formation in upper part of brain stem contains acetylcholine secreting neurons.

Question 27

……..synchronizes sleep/wakefulness rhythm with dark light cycle.

Answer 27

Suprachiasmatic nucleus of hypothalamus

Question 28

Generally, …….produce arousal. …..induce sleep.

Answer 28

RAS & posterior hypothalamus
Anterior hypothalamus & adjacent basal forebrain region

Question 29

Locus cerulus secretes……, raphe nuclei ……., PRF……

Answer 29

NE
Serotonin
Ach

Question 30

…..is produced by hypothalamic neurons

Answer 30

Orexin

Question 31

Inc NE & SE with dec Ach produce…..while opposite produces…..while a balance produces……

Answer 31

Wakefulness & arousal
REM sleep
NREM

Question 32

Wakefulness occurs when……increase & …..decrease

Answer 32

GABA
histamine

Question 33

…….peptide may induce sleep metabolically.

Answer 33

Muramyl