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ANAT242 > Lecture 6- Brain Stem and Cranial Nerves > Flashcards

Lecture 6- Brain Stem and Cranial Nerves Flashcards

1
Q

What are the three major parts of the brain stem?

A

midbrain, pons and medulla

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2
Q

What does the brain stem provide/ what is it’s major purpose?

A

Provides a pathway for axonal tracts running between the forebrain, cerebellum and spinal cord

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3
Q

How many pairs of cranial nerves is the brain stem associated with?

A

10

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4
Q

Are the cranial nerve considered part of the central nervous system or peripheral nervous system?

A

PNS

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5
Q

What are the Cerebral Peduncles (Crus Cerebri) associated with and what are their function?

A
  • Mid brain of the brain stem
  • Includes axons that descend from the cerebral cortex to the brainstem and spinal cord (passing longitudinally on the ventral surface of the midbrain)
  • help to anchor the cerebrum to the brainstem
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6
Q

How many cranial nerves are associated with the mid brain and where are they located?

A
  • III cranial nerves anteriorly

- IV cranial nerves posteriorly

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7
Q

What are colliculi?

A
  • 2 pairs of mounds associated with the midbrain of the brain stem
  • There is the superior colliculus (higher hill) and the inferior colliculus (lower hill)
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8
Q

Label the different elements of the brain stem including the peduncles (both cerebral and cerebellar) and colliculus on a posterior view of the brain stem and then on a midsagittal section… (OneNote)

A

Answers there

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9
Q

What is the role of the superior colliculi?

A

Visual relay + reflex center:

  • receive inputs from the retina/visual cortex & project to vision-related areas in cortex
  • concerned with the detection of movement of objects in the visual field
  • relay vision information to neurons innervating the muscles that control eye movement
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10
Q

What is the role of the inferior colliculi?

A

Auditory relay & reflex nuclei:

  • relaying auditory information from hearing receptors of the ear to the sensory cortex
  • act in reflexive responses to sound (e.g., startle reflex)
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11
Q

What is the substantia nigra?

A
  • located deep to the cerebral peduncle
  • contains melanin pigment (precursor of dopamine) which makes it black in appearance
  • functionally linked to the basal nuclei/ganglia
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12
Q

What does dopamine degeneration in the substantia nigra cause?

A

Parkinson’s disease

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13
Q

What are the two parts of the Substantia Nigra? Which is more ventral?

A
  • pars compacta (SNpc)= cells are close together and where the dopamine neurons are found.
  • pars reticulata (SNpr)= cells are more spread out like a network

Pars reticulata (SNpr)= more ventral. Actually can’t be seen in a standard picture showing the Substania Nigra

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14
Q

What connections does the pars reticular have?

A

SNpr has connections similar to the internal division of the globus pallidus (GPi) = inhibitory input to the thalamus

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15
Q

What is the red nucleus/ what is it’s function?

A
  • lies deep to the substantia nigra
  • rich blood supply & contains iron pigment
  • relay nucleus in some descending motor pathways
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16
Q

To summarize what structures are found within the midbrain of the brainstem?

A
  • Cerebral peduncles
  • Colliculi: superior colliculi, inferior colliculi
  • Substantia nigra
  • Red nucleus
  • Cranial nerves: oculomotor (III), trochlear (IV)
  • Cerebral aqueduct
  • Superior cerebellar peduncle
  • Mammillary bodies
17
Q

What cranial nerves are associated with the pons?

A
  • trigeminal (V)
  • abducens (VI)
  • facial (VII)
  • vestibulocochlear (VIII)
18
Q

What is either side of the mamillary bodies and what view can they be seen in?

A

Mamillary bodies sit in the mid brain and can be seen in a ventral view. The cerebral peduncles are the lines either side.

19
Q

Other than cranial nerves what else is associated with the pons?

A
  • 4th ventricle

- Middle cerebellar peduncle

20
Q

What is the pons composed of + How does this relate to it’s function?

A
  • Composed of conduction tracts - both ascending sensory & descending motor tracts
  • Composed of pontine nuclei (collection of neurons within the pons) e.g. Pneumotaxic Centre (respiratory center). Helps to maintain normal rhythm of breathing (together with medullary center)
21
Q

How does the function of the pons illustrate how a stroke in the brain stem could be fatal?

A

Control of breathing is occurring therefore brain stem stroke could disrupt breathing.

22
Q

What does the medulla consist of?

A 
• Pyramids
• Olives
• Cranial nerves
- glossopharyngeal (IX)
- vagus (X)
- accessory (XI)
- hypoglossal (XII)
• 4th ventricle
• Inferior cerebellar peduncle (connecting the medulla to the cerebellum)
23
Q

What are the pyramids in the medulla?

A

formed by the large pyramidal (corticospinal) tracts descending from the motor cortex

24
Q

What is the Pyramidal Decussation?

A

Axons of pyramidal tracts cross over to the opposite side at the level just above the medulla spinal junction (at the level of the foramen magnum)

25
Q

What are the olives?

A

Containing inferior olivary nuclei, which relay sensory information to the cerebellum

26
Q

Label the diagram on OneNote labelled Revision: Brain stem 2

A

Answers there

27
Q

What are the roles of the medulla?

A

Role in maintaining body homeostasis

-Cardiovascular centre:
Cardiac centre adjusts rate and force of heart beat to meet the body’s needs
Vasomotor centre adjusts blood vessel diameter to regulate blood pressure

-Respiratory centres:
control rate and depth of breathing (together with centre in pons)

-Other reflex centres:
controls activities such as coughing, sneezing, gagging, swallowing, vomiting, sweating

28
Q

What is the medulla functionally associated with?

A

The hypothalamus: The hypothalamus is an important autonomic
control centre. It sends its instructions to the medullary reticular centres, which carry them out by synapsing with the target structure(s)

29
Q

What is the cross- sectional anatomy of the medulla like?

A
  • Segmental arrangement of spinal cord ceases
  • Reorganisation of white and grey matter
  • Columns of white matter become distinct tracts
  • Grey matter arranged into distinct nuclei
30
Q

How many cranial nerves are there?

A

12 pairs (10 associated with brain stem, 2 associated with forebrain)

31
Q

What are the three different ‘types’ of cranial nerves?

A

Sensory and/or Motor Nerves
- some mixed, some pure

Sensory Functions

  • touch, pain for face
  • hearing, vision, smell
  • visceral organs

Motor Functions

  • eye movement
  • jaw & tongue muscles, facial expression
  • visceral organ activity
32
Q

What are the 12 cranial nerves?

A

I. Olfactory VII. Facial
II. Optic VIII. Vestibulocochlear
III. Oculomotor IX. Glossopharyngeal
IV. Trochlear X. Vagus
V. Trigeminal XI. Accessory
VI. Abducens XII. Hypoglossal

Numbered using roman numerals from most rostral to most caudal

33
Q

What is used to remember whether the cranial nerve is motor, sensory or both?

A

Some Say Money Matters But My Brother Says Big Brain Matter Most

34
Q

label the cranial nerves in a diagram also say which are associated with the forebrain, midbrain, pons and medulla?

A

Answers in OneNote

35
Q

What is the first part of cranial nerves? Where do they sit? What is it’s function?

A

I. Olfactory Nerves

  • tiny sensory nerves (filaments)
  • run from the nasal mucosa, pass through cribriform plate of ethmoid bone to synapse with the olfactory bulb (olfactory receptor cells)
  • Provide sense of smell
  • Damage causes impaired sense of smell (anosmia) (e.g., fracture of ethmoid bone
36
Q

Label the diagram on OneNote showing the olfactory projection pathways…

A

Answers there

37
Q

What is the second pair of cranial nerves? Where do they sit? What do they do?

A
  • Axons arising from the retina of the eye to form optic nerve
  • Each optic nerve passes through its optic foramen of the orbit. Nerves converge to form optic chiasm (axons partially cross over) & continue on as optic tracts
  • Enables vision
38
Q

Summarize what each retina sees of the visual world in relation to the optic pathways and what each part of the retina (nasal or temporal sees)…

A
  • Each nasal retina sees a temporal visual field/world.
  • Each temporal retina sees a nasal visual field/world.
  • Left side of each retina sees the right visual field world.
  • Right side of each retina sees the left visual field/world.

ANAT242 (25 decks)

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