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Brain and Behaviour > Reticular formation > Flashcards

Reticular formation Flashcards

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1
Q

what is the organisation of the brainstem split into

A

dorsal part
middle part
ventral part

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2
Q

what does the dorsal part have in it

A

cranial nerve nuclei and sensory reflex centers

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3
Q

what does the middle part have in it

A

• Middle part (tegmentum) - ascending pathway and RETICULAR FORMATION (with integrating nuclei); descending sympathetic axons travel with reticulospinal tracts

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4
Q

what does the ventral part have in it

A

descending motor pathways e.g., corticospinal & corticobulbar tracts; rubrospinal, reticulospinal and vestibulospinal tracts arising in brainstem

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5
Q

what is the reticular formation

A
  • It is a network of cells that run through the brainstem, medulla pons and midbrain
  • it performs numerous integrative and modulatory functions.
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6
Q

what does the reticular formation of the brainstem do

A
  • it is the core of the brainstem

- it controls basic functions and autonomic functions

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7
Q

what does the reticular formation consist of

A
  • It consists of scattered clusters of neurons amidst ascending and descending axons of the tegmentum.
  • Usually these clusters cannot be easily recognized as distinct nuclei.
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8
Q

describe the organisation of the reticular formation

A
  • Lateral sensory inputs – sensory and other inputs from ascending and descending systems
  • Motor – outputs – efferent output to midbrain, cerebellum, hypothalamus, thalamus and spinal cord
  • Midline (modulatory- Raphe nuclei – 5HT – faciliatory or inhibitor pain, filtering inputs
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9
Q

what are the 4 principle functions of the reticular formation

A
  1. Arousal responses
  2. Autonomic nervous system control
  3. Control of muscle tone and reflexes
  4. Pain modulation
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10
Q

describe some other functions of the reticular formation

A
  • Somatic reflex regulation – gain facilitation, for example how much tone the muscle has, it gives activity to particular muscle groups over other ones.
  • Visceral regulation via control of autonomic functions – respiratory, cardiovascular, bladder control
  • Maintenance of consciousness, sleep and arousal
  • Sensory filtering and modulation
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11
Q

what are some examples of how somatic reflex regulation happens

A
  • Premotor control, allows eye movements and coordinate movements, reflexes that involve both autonomic and somatic effects,
  • there are somatic regulation of postural reflexes as well- extrapyramidal motor control
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12
Q

what do the reticulopsinal projects do

A
  • Reticulospinal projects controlling postural adjustments and segmental control of motor reflexes that span the length of the brainstem
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13
Q

what does the caudal pontine and medullary reticular formation do

A
  • Caudal pontine and medullary reticular formation – premotor coordination of lower somatic and visceral motor neuronal pools and raphe descending control
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14
Q

what does the mesencephalic and rostral pontine reticular formation do

A
  • Mesencephalic and rostral pontine reticular formation – includes the conscious state
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15
Q

what is the role of the reticulospinal tract

A
  • In the somatic nervous system it has a feedforwards and anticipated postural stability
  • For example when you think to move you have to adjust other musculature, this is mediated by the reticulospinal output pathway
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16
Q

what pathway regulates postural adjustment

A
  • The indirect extrapyramidal motor pathway that regulates postural adjustment
  • If there is posture instability it goes up the pathway as negative feedback
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17
Q

wha are the reticular formation centres involved in control coordinating eye movements

A

paramedian pontine reticular formation (PPRF) and mesencephalic (vertical) gaze centres
- Following frontal eye field excitation the paramedian pontine reticular formation generates horizontal eye movements

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18
Q

what does lesions to the MLF do

A

. Lesions to the medial longitudinal fasciculus disrupt CNIII connectivity and function

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19
Q

what is the nucleus of solitary tract

A

The nucleus of the solitary tract is the main visceral sensory processing site

20
Q

what does the nucleus of solitary tract do

A

– involved in taste, and inform about blood pressure and oxygen concentrations in the blood

21
Q

how does the reticular formation control respiratory control

A
  • The NTS is the sensory processing centre where inputs come about need for oxygen and breathing, this is the dorsal respiratory group
  • The dorsal respiratory group is connected to the ventral respiratory group
  • The ventral respiratory group has the nucleus ambiguous in it which surrounds the reticular formation
  • The medullary pacecentre include the pre botzinger complex which mediates inrpsiationa nd exrpaition and generate the breathing rhythm
22
Q

what happens if you get an lesion to the NTS (nucleus of solitary tract )

A
  • get Cheyenne stokes respiration
23
Q

what nucleus is in control of the dorsal respiratory group

A

nucleus of solitary tract

24
Q

what nucleus is in control of the ventral respiratory group

A

nucleus ambiguous

25
Q

what does the pontine reticular formation do

A
  • Controls the ventral and dorsal medullary centres
  • It fine tunes it
  • Allows us to breath as we talk and do exercise, and sleep
  • contains The pneumotactic and the apneustic centre c
26
Q

what does the pneumotactic centre do

A
  • The pneumotactic centre limits inspiration and facilitates expiration, it stops excessive breathing
27
Q

what does the apenustic centre do

A
  • The apneustic centre prolongs inspiration and reduces expiration
28
Q

where does input come from to the NTS

A
  • They arise from vagal lung mechoreceptor afferents
  • CNIX arterial chemoreceptor (blood PO2) afferents
  • Input also comes from chemoreceptors in the floor of the 4th ventricle that monitor pH of the CSF
29
Q

what happens to breathing if there is a lesion below the medulla

A

Lesions below the medulla it is impcompatible with life and you cannot breath and vnetilaton stops

30
Q

what happens if there is a lesion between pneumotaxic centres and apeneustic centre

A

Apneustic breathing

- with deep and prolonged inspiration followed by short, insufficient expiration

31
Q

what does the NTS do in to terms of the cardiovascular system

A
  • Mechanosensory baroreceptor input on blood pressure as well as chemosensory input on blood PO2 travels to the brainstem NTS in CN X and IX respectively
  • The NTS relays this information to the hypothalamus and brainstem reticular nuclei.
  • Vagal output originating in the dorsal motor nucleus of the vagus and n. ambiguus as well sympathetic n.s. outputs (via reticulospinal hypothalamo-spinal projections) mediate compensatory changes in cardiac function and peripheral vasculature in response to altered afferent input.
32
Q

what does the reticulospinal tract input

A

Reticulospinal tract projects to the preganglionic autonomic neurones (both sympathetic and parasympathetic).

33
Q

what happens if the reticulospinal tract is damaged

A

If the reticulospinal tract is damaged the autonomic output is lost leading to loss of blood pressure, temp regulation (sweating), bladder and bowel control

34
Q

what is the main centre for noradrenaline

A

locous coerculeus

35
Q

Dopamine

  • what is the nucleus involved
  • what does it do - what happens if there is a loss of movement
  • what area is it in
A
  • Substantia Nigra (SN)- nigrostriatal pathway

Control of movement- initiation/ switching
- Loss  Parkinson’s disease
Organising behaviour; focusing & attention; reward & motivation

Ventral tegmental area (VTA)
- Mesolimbic and mesocortical pathways

36
Q

what happens if there is a distribuance in dopamine

A

Schizophrenia; Addiction

37
Q

noradrenaline

  • what is the nucleus involved
  • what does noradrenaline do
A

Locus coeruleus and other nuclei

Sympathetic NS control centre activated by the hypothalamus

  • Descending fibres carried in reticulospinal tract activate preganglionic sympathetics
  • Also activates the motor system so our reflexes are faster.
  • Also inhibition of pain
  • Ascending fibres to the forebrain activate a central sympathetic system  behavioural alertness & arousal (esp. to stress/ stimuli evoking fear)
38
Q

Sertonin

  • what is the nucleus involved
  • what does it do
  • what do deficits produce
A

Raphe nuclei – midline nuclei

  • Rostrally Inhibits basal forebrain cholinergic GABA cells to produce arousal; gate sensory input to cortex; effects on cognition, mood
  • Caudally - modulates pain perception and facilitates muscle activity
  • Numerous receptor types/ complex

Deficits produce OCD, depression, anxiety, aggression

39
Q

what drugs target serotonin

A

Drugs that target 5HT receptors affect mood e.g. anti depressants, also anti-migraine, anxiolytics, hallucinogens, anti-psychotics

40
Q

Acetycholine

  • what is the nucleus involved
  • what does it do
A
  • Involved in Pedunculopontine & lateral dorsal tegmental nuclei of the brainstem
  • Cortical arousal and sensory filtering through thalamic projection and movement
  • Mediates activity of the thalamus
41
Q

what is the sleep promoting system

A
  • Anterior hypothalamus
  • Ventrolateral preoptic (VLPO) area
  • GABA/ galanin
  • Inhibit wake promoting neurons
42
Q

what does a lesion in the sleep promoting system cause

A

Insomnia (anterior hypothalamus

43
Q

what is the ascending arousal (sleep waking system)

A
  • increase firing in anticipation of waking and in arousal
  • Brainstem reticular formation (RF)
  • damage to can lead to coma
    locus coeruleus (NA) and raphe n (5HT) Posterior hypothalamus
  • Tuberomammillary nucleus (TMN) of the hypothalamus – Histamine
44
Q

what does a lesion to the posterior hypothalamus and ascending arousal system lead to

A

hyersommia

45
Q

what does acetylcholine do in ascending arousal systems

A

ACh promotes forebrain activation in both waking and REM sleep (via thalamus + basal forebrain)

Brain and Behaviour (34 decks)

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