Brainstem Part 1 Flashcards

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1
Q

where is the brainstem located

A

Located between the forebrain and spinal cord

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2
Q

what makes up the brainstem

A

Comprised of the midbrain, pons and medulla

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3
Q

what is the oldest part of the brain

A

brainstem

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4
Q

what does the pons do

A
  • it relays sensory information to the cerebellum and thalamus
  • subconscious somatic and visceral motor centres
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5
Q

what does the midbrain do

A
  • it processes visual and auditory data
  • generation of reflexive somatic and motor responses
  • maintenance of consciousness
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6
Q

what does the medulla do

A
  • relays sensory information to the thalamus and other parts of the brainstem
  • autonomic centres for regulation of visceral function such as cardiovascular, respiration and digestive system
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7
Q

what are the 3 functions of the brainstem

A
  1. conduits
  2. Cranial nerve functions
  3. integrative centres in the brainstem
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8
Q

what is the conduit function of the brainstem

A

long tracts to or from the spinal cord pass through the brainstem

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9
Q

what are the cranial nerve functions of the brainstem

A
  • there is the sensory input and motor output for the head plus parasympathetic motor output;
  • cranial nerves also carry special senses
  • the brainstem coordinates reflexes involving them.
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10
Q

what are the integrative centres in the brainstem

A

sensoriomotor integration

brainstem core

  • autonomic control
  • somatic and autonomic modulation
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11
Q

what is sensorimotor integration

A
  • this is connectivity with the cerebellum and where the reflex centres are
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12
Q

what is the brainstem core mediating

A
  • autonomic control of important respiratory and cardiovascular reflexes & other behaviours e.g., swallowing, sneezing.
  • Somatic/ autonomic modulation via descending pathways (reticulospinal tract, descending premotor sympathetic axons from hypothalamus)
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13
Q

different neuromodulatory systems are….

A

important in regulation of conscious states as well as affecting sensory, motor and cognitive functions.

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14
Q

where dot he sensory nucleic that were dorsal in the spaniel cord move when they enter the brainstem

A

they move laterally and ventrally(towards the front and down )

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15
Q

where do the motor nuclei that were ventral in the spinal cord move when they enter the brainstem

A
  • the move more medially
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16
Q

how is the brainstem organised

A

It is divided into..

  • Dorsal part
  • middle part
  • ventral part
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17
Q

what does the dorsal part(tectum) of the brainstem have in it

A
  • cranial nerve nuclei and sensory reflex centres
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18
Q

what does the middle part (tegmentum) of the brainstem have in it

A
  • it contains the ascending pathways and reticular formation (with integrating nuclei; descending sympathetic axons
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19
Q

what does the ventral part of the brain stem have in it

A

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

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20
Q

what do conduit functions of the brainstem allow

A
  • they allow integration of information at subconscious, reflexive level by connectivity with brainstem
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21
Q

how many Paris of cranial nerves are there

A

12 pairs

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22
Q

what do cranial nerves do

A
  • Provide sensorimotor innervation of the skin, muscles and joints of the head & neck.
  • Mediate vision, hearing, taste and olfaction (special senses)
  • Carry autonomic fibres that control visceral functions e.g. gut, breathing, heart rate, and blood pressure regulation.
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23
Q

what are the origin of cranial nerves

A

Cranial nerve nuclei are one origin of preganglionic parasympathetic neurons

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24
Q

what surface of the brainstem can cranial nerves be seen from

A

Cranial nerves can be seen from the ventral surface

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25
Q

where do afferent cranial nerves arise form

A
  • cranial nerves have afferents which arise from ganglia
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26
Q

where do 2nd order sensory nuclei arise from

A

they are located in cranial nuclei

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27
Q

where do motor efferents arise from

A

Motor efferents arise from cranial nerve nuclei. Such nuclei control parasympathetic and somatic motor functions

28
Q

name the cranial nerves and whether they are sensory or motor or both

A
CNI - Sensory 
CNII - sensory 
CNIII - motor 
CNIV- motor
CN V - sensory and motor 
CN VI -  motor
CN VII -  sensory and motor 
CN VIII - sensory 
CN IX -  sensory and motor 
CN X -  sensory and motor 
CN XI - motor
CN XII -  motor
29
Q

what cranial nerves is the midbrain associated with

A

II - IV

- Associated with auditory, visual and pupillary reflexes and with eye movements.

30
Q

what cranial nerves is the pons associated with

A

V-VIII
- Its main functions are mastication (V), eye movement (VI), facial expression, taste, blinking, salivation, lacrimation (VII), and equilibrium and audition (VIII).

31
Q

what cranial nerves is the medulla associated with

A

VIII-XII
- Associated with equilibrium, audition (VIII), deglutition, salivation, taste (IX), respiration & circulation, GI function (X), neck & shoulder movments (XI) tongue movements (XII), coughing and vomiting (RF).

32
Q

where are the sensory nerves located

A

laterally

33
Q

where are the motor nerves located

A

medially

34
Q

describe the general breakdown of cranial nerves in parts of the brainstem

A

In general II-IV are associated with the midbrain, V-VIII pons and IX-XII medulla

35
Q

what are the three types of motor nucleic

A
  • somatic motor nuclei
  • branchial motor nucleic
  • visceral motor nuclei
36
Q

describe the three types o motor nuclei

A

Somatic motor nuclei project to skeletal muscle (eye muscles and tongue)

Branchial motor nuclei project to muscles derived from branchial arches (craniofacial structures)– movement of jaws (V), facial expression (VII), motor to larynx and pharynx (X) and neck and shoulder muscles (XI)

Visceral motor nuclei: pre-ganglionic parasympathetic fibres

37
Q

describe the nuclei from the midline

A
  1. Somatic motor: lower motor neurons (LMNs- somatic and branchial)
  2. Visceral motor i.e. preganglionic parasympathetic
  3. Visceral sensory i.e. from gut, blood vessels, mucosa incl. taste
  4. Somatic sensory – general (V) and special (VIII)
38
Q

what are cranial nerve nuclei

A
  • these are columns of neurones that are associated with cranial nerves
39
Q

what organisation do the cranial nuclei follow

A
  • they follow the rostral-caudal organisation of the structures innervated
40
Q

where does the spinal accessory nerve arise from and describe its pathway

A
  • Arises from branchial motor neurons in the spinal cord.

- Enters cranial cavity via foramen magnum and exits via the jugular foramen.

41
Q

what does the spinal nerve innervated

A

Innervates sternocleidomastoid

&trapezius muscles.

42
Q

where do the motor neurones that give rise to the accessory nerve come from

A

The motor neurons giving rise to the accessory nerve are actually a separated fragment of the long column of the nucleus ambiguus. They arise from C3-C5

43
Q

what are the three nuclei that the vagus can arise from

A

Can arise from 3 nuclei

  • dorsal motor nucleus of vagus
  • nucelus ambiguus
  • nucleus of the solitary tract
44
Q
what does the vagus from 
- dorsal motor nucleus of vagus 
- nucelus ambiguus 
- nucleus of the solitary tract  
arise from and innervate
A
  • The dorsal motor nucleus of the vagus gives rise to Parasympathetic outflow to the heart and digestive system (and parasympathetic part of n. ambiguous
  • the nucleus ambiguus - this is where the brachial motor innervation arises which innervates the palate, pharynx and larynx

The nucleus of the solitary tract gives rise to Afferents from the lungs and gut travel in the vagus nerve mediating parasympathetic reflexes, swallowing, coughing, retching etc… Visceral afferent information is processed in the caudal nucleus of the solitary tract (NTS)

45
Q

what is the role of the glossopharygneal

A
  • Its main function is to detect the taste of things in the back of the mouth and secrete saliva into the mouth.
  • It also contains touch fibres from the back of the mouth and these trigger the gag reflex.
46
Q

what nucleus is involved in the glossopharyngeal

A
  • Taste from posterior part of tongue is detected and conveyed to the rostral nucleus of the solitary tract & stimulates saliva secretion.
  • There are also sensory mechanoreceptors in pharynx for touch travelling in it.
47
Q

what does damage to the vagus lead to

A
  • difficulty swallowing and vocalising due to paralysis of vocal cords on affected site
  • poor secretion of various gut fluids, saliva, stomach acid, etc due to lost vagal parasympathetic control
48
Q

what does damage to the glossophargenal lead to

A

Loss of Gag reflex on affected side.

49
Q

what does the Vestibulocochlear nerve do

A

Cochlear portion: conveys the special senses of audition (hearing)

Vestibular portion: our perception of self motion, head position and spatial orientation relative to gravity

50
Q

describe the pathway of the Vestibulocochlear nerve

A
  • there is vestibular and cochlear nuclei that form a complex that spans from the pons into the rostral medulla
  • the nerve enters the brainstem at the medulla and pons junction
51
Q

where does the facial nerve enter the skull

A
  • via the internal auditory meatus - it can be damaged by an caustic neuroma as it travels with the vestibulocochlear nerve
52
Q

what is the main action of the facial nerve

A

Main action is to provide motor supply to muscles of facial expression

53
Q

what are the 3 jobs of the facial nerve

A

1- motor supply to muscles of facial expression
2 - parasympathetic secretomtoor - controls nasal and lacrimal secretion
3. Taste afferents

54
Q

describe the 3 jobs of the facial nerve

A

Five somatic divisions– mainly branchial motor (some sensory fibres carry touch, pain, temperature sensations via posterior auricular nerve)

Parasympathetic secretomotor– superior petrosal nerve controls nasal secretion and lacrimation

Taste afferents from the anterior 2/3 of the tongue travel from the chorda tympani (with parasympathetic fibres to submandibular and sublingual salivary glands) via the geniculate ganglion to the rostral nucleus of the solitary tract (→ventromedial thalamus → insular cortex)

55
Q

what are the 4 roles of the trigeminal

A

Motor to muscles of mastication in V3

Touch sensation of face

Pain, temperature, crude touch of face

Proprioceptive input-

56
Q

describe the nuclei that are involved in each of the roles of the trigeminal

  • Motor to muscles of mastication in V3
  • Touch sensation of face
  • Pain, temperature, crude touch of face
  • Proprioceptive input
A

Motor to muscles of mastication in V3 : Motor nucleus of trigeminal - upper motor neuron (cortical) innervation is bilateral, so supratentorial stroke will not alter mastication

Touch sensation of face (+ dura…) → this is controlled by the Trigeminal ganglion→ Principal trigeminal nucleus

Pain, temperature, crude touch of face (+) → Trigeminal ganglion → spinal trigeminal nucleus

Proprioceptive input- muscles of mastication– mesencephalic trigeminal nucleus

57
Q

what does the medial longitudinal fascicles do

A

this connects cranial nerve nuclei controlling eye movement and the vestibular nuclei

58
Q

what does damage to the medial longtudinal fascicles do

A

Internuclear ophthalmoplegia occurs with damage to the medial longitudinal fasciculus (MLF).

  • with a MLF lesion when asked to look left normally both eyes look left but with MLF lesion one eye stays central
  • both eyes can still do convergence
59
Q

how can damage to the MLF occur

A
  • can occur due to a stroke - unilateral

- multiple sclerosis - bilateral

60
Q

where is the MLF in the brainstem

A

The MLF extends the length of the brainstem

61
Q

what does the MLF become in the spinal cord

A

The MLF becomes the medial vestibulospinal tract (mVST) in the spinal cord

62
Q

what does the medial vestibulospinal tract (mVST) do

A

Acting on motoneurons for neck muscles, the mVST coordinates reflexive head and neck movements to keep eyes stable in space.

63
Q

what is the input and output for the pupillary light reflex

A

CNII (in) and III (out)

64
Q

describe how the pupillary light reflex works

A
  • Light- sensory input- axons of retinal ganglion cells in CNII- optic nerve
  • Synapse in pretectal nucleus (midbrain)
    Bilateral innervation of
  • Edinger- Westphal nucleus (E-W; parasympathetic div of CNIII)
  • E-W nuclei send output to both ciliary ganglia which cause constriction of pupils via sphincter pupillae muscles
65
Q

what is information sent to the superior colliculus involved in

A

Information sent to the superior colliculus is important in visual fixation and tracking