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Systems Neuroscience > Brainstem > Flashcards

Brainstem Flashcards

1
Q

Brainstem

  • contains
  • What makes it up (midbrain structures and so on)
A
  • In humans, includes the midbrain, pons, and medulla
  • Midbrain includes substantia nigra, colliculi, red nucleus, VTA…
  • “the midbrain and stuff”
  • contains 10 pairs of cranial nerves

*Much of the core of the brainstem consists of “reticular formation”

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2
Q

Medulla

A

Where spinal cord magically turns into brain around the level of the foramen magnum
Emergence of the pyramids and pyramidal decussation
*The “upper” end of the medulla is about in line with the cerebellar peduncles, where it becomes physically continuous with the pons

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3
Q

cranial nerves of the medulla**

A

XII, IX, X

Cranial Nerves: hypoglossal (XII, motor), vagus (X, mixed), and glossopharyngeal (IX, mixed)
Also accessory nerve if you want to lump it in there…
Maybe a touch of the facial (solitary nucleus) and trigeminal

*The abducens (VI, motor), facial (VII, mixed), and vestibulocochlear (VIII, sensory) nerves exit at the pons-medulla junction

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4
Q

Solitary nucleus:

A

sensory neurons from 3 different cranial nerves
VII, IX, X

-part of the medulla

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5
Q

Spinal Trigeminal nucleus:

A

*part of the medulla

shared by multiple cranial nerves; crude temperature/touch from trigeminal and pain from all 4

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6
Q

found in the pons

A

Portions of the TRIGEMINAL nuclei and the VESTIBULAR(COCHLEAR) nuclei

Right at the pons-medulla border: FACIAL motor nucleus, superior salivatory nucleus (facial nerve), and ABDUCENS nucleus.

Trigeminal nerve (V, mixed) emerges from the lateral aspect of the pons
Abducens (VI, motor), facial (VII, mixed), and vestibulocochlear (VIII, sensory) nerves exit at the pons-medulla junction
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7
Q

Right at the pons-medulla border:

A

Right at the pons-medulla border: facial motor nucleus, superior salivatory nucleus (facial nerve), and abducens nucleus.

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8
Q

midbrain***

A

*Extends from pons to roughly the thalamus on the dorsal-ventral axis
Extends from the caudal end of the mammillary bodies to the posterior commissure on the anterior-posterior axis

  • Posterior aspect: characterized by the superior and inferior colliculi, and their respective nuclei
  • Anterior aspect: characterized by the crus cerebri and interpeduncular fossa.

Interpeduncular fossa: houses oculomotor nucleus
*Fun fact: exists in primates, but does not appear to exist in rodents

Cranial Nerves: oculomotor nerve (III, motor) exits the anterior aspect and the trochlear nerve (IV, motor) exits its posterior aspect

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9
Q

Crus cerebri ***

A

*anterior part of the cerebral peduncle *contains motor tracts coming from the cortex

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10
Q

Interpeduncular fossa***

A

Interpeduncular fossa: houses oculomotor nucleus

Fun fact: exists in primates, but does not appear to exist in rodents

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11
Q

cranial nerves of the midbrain

A
  • oculomotor nerve (III, motor) exits the anterior aspect

* the trochlear nerve (IV, motor) exits its posterior aspect

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12
Q

Tegmentum and Basilar Areas

A

*Part of the midbrain, pons, and medulla

so um like the brainstem? thinking alex

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13
Q

Pons:

A

Pons: relay station; REM sleep

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14
Q

Crus cerebri***

A

motor tracts; anterior portion of cerebral peduncle; link brainstem to thalamus (cortex)

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15
Q

Red nucleus

A

Red nucleus: motor coordination via inferior olivary nucleus

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16
Q

Substantia nigra:

A

Substantia nigra: reward, addiction, movement; Parkinson’s; dopaminergic neurons have lots of neuromelanin

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17
Q

Descending Tracts

A

The descending tracts are the pathways by which MOTOR SIGNALSare sent from the brain to lower motor neurons.
The lower motor neurons then directly innervate muscles to produce movement.
No synapses* within the descending pathways
At the termination of the descending tracts, the neurons synapse with a lower motor neuron.
All neurons within the descending motor system are classed asupper motor neurons.
-Their cell bodies are found in the cerebral cortex or the brain stem, with their axons remaining within the CNS

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18
Q

upper motor neurons

A

All neurons within the descending motor system are classed asupper motor neurons.

Their cell bodies are found in the cerebral cortex or the brain stem, with their axons remaining within the CNS

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19
Q

Brainstem Motor Tracts **

-in general, can be functionally divided into what major groups

A

The motor tracts, in general, can be functionally divided into two major groups: Pyramidal tracts and Extrapyramidal tracts

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20
Q
  • *Pyramidal tracts
  • originiate
  • responsibilities
A

These tracts originate in the CEREBRAL CORTEX, carrying motor fibers to the spinal cord and brain stem.
They are responsible for the VOLUNTARY control of the musculature of the body and face.

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21
Q
  • *Extrapyramidal tracts
  • originate
  • responsibilities
A

*These tracts originate in the BRAIN STEM, carrying motor fibers to the spinal cord.
They are responsible for the INVOLUNTARY and automatic control of all musculature, such as muscle tone, balance, posture and locomotion

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22
Q
  • Pyramidal Tracts
  • pass through the …
  • responsibilities
A

Named after themedullary pyramids of the medulla oblongata, which they pass through.
Responsible for the voluntary control of the musculature of thebodyandface.

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23
Q

Corticospinal Tracts**

  • begins in the :
  • receives inputs from:**
A
  • begin in the cerebral cortex
    *Corticospinal Tracts receivesa range of inputs: Primary motor cortex, Premotor cortex, Supplementary motor area
    They also receive nerve fibers from thesomatosensory area
    Somatosensory area plays a role in regulating the activity of the tracts.
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24
Q

Corticobulbar Tract**

  • begins/arises from
  • inputs
A

*Arise from the lateral aspect of the primary motor cortex.
*Corticobulbar Tract receivesa range of inputs: Primary motor cortex, Premotor cortex, Supplementary motor area, They also receive nerve fibers from thesomatosensory area
Somatosensory area plays a role in regulating the activity of the tracts.(Receive the same inputs as the corticospinal tracts.)

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25
Q

exceptions to the rule that many of the Corticobulbar fibers innervate the motor neurons BILATERALLY

A

There are a few exceptions to this rule:
Upper motor neurons for thefacial nerve(CN VII) have a contralateral innervation.
This only affects the muscles in the lower quadrant of the face – below the eyes
Upper motor neurons for thehypoglossal(CN XII) nerve only providecontralateralinnervation.

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26
Q
  • *Extrapyramidal Tracts
  • originate
  • responsibilities
  • modulated by:
A

*Originate in thebrainstem, carrying motor fibers to thespinal cord.
Responsible for theinvoluntaryandautomaticcontrol of all musculature, such as muscle tone, balance, posture and locomotion.

Four tracts: Vestibulospinal Tracts:

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27
Q

*how many of the extrapyramidal tracts stay ipsilateral? and what are they?

A

2 of the 4 extrapyramidal tracts stay ipsilateral

1) Vestibulospinal Tracts: divided into 2 pathways (medial and lateral)
2) Reticulospinal Tracts:

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28
Q
  • Vestibulospinal Tracts:
  • arise from:
  • information:
A

-one of the two ipslateral extrapyramidal tract
*divided into 2 pathways (medial and lateral)
Arise from thevestibular nuclei
Convey this balance information to the spinal cord
ControlBALANCEandPOSTUREby innervating the ‘anti-gravity’ muscles (flexors of the arm, and extensors of the leg), via lower motor neurons.

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29
Q

*Reticulospinal Tracts:

A

-one of the two ipslateral extrapyramidal tract

  • divided into 2 pathways (medial and lateral)
    Medial reticulospinal tract-arises from thepons; facilitates voluntary movements and increases muscle tone.
    Lateral reticulospinal tract-arises from themedulla; inhibits voluntary movements and reduces muscle tone.
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30
Q

Medial reticulospinal tract-

A

arises from thepons; facilitates voluntary movements and increases muscle tone.

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31
Q

Lateral reticulospinal tract-

A

Lateral reticulospinal tract-arises from themedulla; inhibits voluntary movements and reduces muscle tone.

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32
Q

*how many of the extrapyramidal tracts decussate? and what are they?

A

2 of the 4 extrapyramidal tracts decussate (cross)
1) Rubrospinal Tract:
2) Tectospinal Tract:
Colliculospinal

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33
Q

*Rubrospinal Tract

A

*1 of the 2 extrapyramidal tracts that decussate (cross)
*Originates from thered nucleus, a midbrain structure involved in motor coordination
Fibers decussate as they emerge
Exact function is unclear, but it is thought to play a role in the fine control of hand movements

34
Q

*Tectospinal Tract:

Colliculospinal

A

*1 of the 2 extrapyramidal tracts that decussate (cross)

*Originates at superior colliculusof the midbrain.
Optic nerve input
Neurons quickly decussate and enter the spinal cord.
Terminate at the cervical levels of the spinal cord.

35
Q

Damage: Corticospinal Tracts*

A

*Pyramidal tracts are susceptible to damage, because they extend almost the whole length of the CNS
Particularly vulnerable as they pass through the internal capsule – a common site of cerebrovascular accidents

*If there is only a unilateral lesion of the left or right corticospinal tract, symptoms will appear on the contralateral side of the body.
Hypertonia – an increased muscle tone
Hyperreflexia – increased muscle reflexes
Clonus – involuntary, rhythmic muscle contractions
Babinski sign – extension of the hallux (big toe) in response to blunt stimulation of the sole of the foot
Muscle weakness

36
Q

Damage: Corticobulbar Tracts*

A
  • Bilateral nature of the majority of the corticobulbar tracts means a unilateral lesion usually results in mild muscle weakness.
  • Not all the cranial nerves receive bilateral input, and so there are a few exceptions:
  • Hypoglossal nerve : a lesion to the upper motor neurons –> spastic paralysis of the contralateral side/deviation of the tongue
  • Facial nerve : a lesion to the upper motor neurons –> spastic paralysis of the muscles in the contralateral lower quadrant of the face
37
Q

Damage: Extrapyramidal Tracts*

A
  • descending tract
    *Lesions are commonly seen in degenerative diseases, encephalitis, and tumors.
    They result in various types of dyskinesias (disorders of involuntary movement
38
Q

*Reticular Formation

A
  • part of the brainstem
  • Much of the core of the brain stem consists of “reticular formation”
  • Small neurons that perform an integrating function and coordinate motor actions of cranial nerve motor nuclei
  • Large neurons with axons that ramify extensively with collateral branches that distribute throughout the brain stem
  • Also ascending to the thalamus and descending to the spinal cord
39
Q

the reicular formation has small or large neurons?

A

trick question

40
Q

what is the reticular foramtion doing**

A 
Modulatory
Premotor
Keeps you alert
Consciousness
Alarm system
Initiates threat responses
Dry mouth, increased heart rate
Connected to the thalamus
Not to be confused with the reticular nucleus of the thalamus
41
Q

Reticular Activating System**

A

*Bulboreticular facilitory area (Another name for it)
*Ignition system
*Prepares your brain for higher level of activity
Neurons project upward and synapse on neurons in “non-specific” or “diffuse” thalamic nuclei.
These nuclei send projections to all areas of the cerebral cortex.

*Continuous with regions of the thalamus and hypothalamus: Reticular nucleus of the thalamus and Lateral hypothalamic area

  • Same region that gives rise to the ascending fibers also gives rise to fibers that DESCEND AND TERMINATE ON THE SPINAL CORD
  • Provide faciliatory signals which maintain tone of the “anti-gravity” or “postural” muscles.
  • Maintain appropriate excitability of the neurons that form the spinal reflex arcs.
42
Q

Reticular nucleus of the thalamus*

A

GABAergic neurons
Does not project to cortex directly
Modulates the rest of the thalamus and information flowing through it
May help the organism respond to novel stimuli

43
Q

where does _______ XXX

eeek confused!

A

descend and terminate on the spinal cord.

44
Q

Reticular Activating System- Sleep*

A

Alternately releases the cortex then paradoxically strongly facilitates the cortex while the subject remains asleep.
The initial sleep form is termed slow wave or delta wave sleep. This is a deep and restorative form of sleep when the cortex is not being facilitated and the EEG would of course be dominated by delta waves.
After approximately 90 minutes of delta wave activity, the brain wave pattern changes dramatically from the delta wave to the beta wave pattern.
REM sleep
During this REM or “paradoxical” sleep, there is a high incidence of dreaming accompanied by strong inhibition of skeletal muscle tone throughout the body.

45
Q

Reticular Activating System- Waking State*

A

Consciousness itself appears to be self-promoting.
Two important mechanisms that excite and facilitate the RAS.
*Activity in the sensory pathways that ascends through the brainstem
These somatosensory pathways have collaterals that terminate on the brainstem component of the RAS.
An important source of stimulation to the RAS.
Activity in the sensory pathways to the cortex helps activate the RAS, which in turn facilitates the cortex which allows processing of the sensory input.
There are extensive bidirectional connections between the cortex and the thalamus.
Once the cortex is facilitated, it reciprocates by facilitating the thalamus.
Positive feedback mechanism promotes wakefulness
*Acts as a filter
Weed out repetitive, unimportant stimuli
*Also helps you re-attend to important stimuli
Cat food
Your name

46
Q

how to wake up the reticular activating system

A 
Pinching yourself
Turning up the AC
Humming
Listening to music
Watching TV
Tapping your feet
47
Q

damage to the Reticular Activating System

A 
Damage- coma
Altered activity levels
Narcolepsy (also not enough orexin)
Chronic Fatigue?
Attention Deficit Disorder
48
Q

Brainstem- Reticular Formation: 3 main divisions***

A

*Median column (raphe nuclei)
Located next to the midline
Serotonergic neurons

*Medial column

*Lateral column (parvocellular reticular nucleus)
Lateral to the medial column
Visceral function
Small cells

49
Q

Ascending Tracts

A

The pathways by which sensory information is transmitted from the periphery to the cortex
Also known as somatosensory tracts
Therefore, we will only briefly address them here
Functionally, the ascending tracts can be divided into the type of information they transmit: Conscious tractsand
Unconscious tracts

50
Q

Brainstem roles (general)

A
  • motor and sensory information highway

- cardiac and respiratory function

51
Q

Basilar Area *

A

Basilar Area: descending fibers of the crus cerebri, basilar pons, and pyramids and “specific populations of neurons in the midbrain and pons that originate from the alar plate of the embryonic brain”

52
Q

*** which part of the brainstem is characterized by the crus cerebri and interpeduncular fossa.

(bes specific)

A

midbrain: Anterior aspect

53
Q

** Tegmental Area: is made up of…

A
  • contains ascending and descending tracts; many relay nuclei, and the nuclei of cranial nerves III to X, and XII
  • Includes the “tegmentum”- red nucleus and substantia nigra
54
Q
  • Pyramidal tracts

- subdivisions and functions

A

Functionally, these tracts can be subdivided into two:
Corticospinal tracts– supplies the musculature of the body.
Corticobulbar tracts– supplies the musculature of the head and neck.

55
Q

Corticospinal tracts

  • converging point:
  • after converging point:
A
  • Neurons converge and descend through theINTERNAL CAPSULE

* After the internal capsule, the neurons pass through thecrus cerebriof the midbrain, theponsand into the medulla.

56
Q

Internal capsule

A
  • converging point for the corticospinal tract
  • the fibers of the corticobulbar tract pass through the internal capsul (to the brainstem)
  • a white matter pathway, located between the thalamus and the basal ganglia
  • white matter road; both motor and sensory
57
Q

Clinical importance of Internal capsule

A

Clinical importance: internal capsule is particularly susceptible to compression fromhaemorrhagic bleeds, known as a ‘capsular stroke‘.
Can result in a lesion of the descending tracts.

58
Q

Corticospinal tracts- where does the tract divide*

A

*In the most inferior (caudal) part of the medulla, the tract divides into two:
Lateral corticospinal tract: mostly limb control
Anterior corticospinal tract: mostly trunk and shoulders

59
Q

*the lateral corticospinal tract fibers: (after the ___)

A

-the lateral corticospinal tract is one of the divisions after the corticospinal tract divides in the caudal part of the medulla

-the lateral corticospinal tract fibers mostly cross over to the other side of the CNS.
Descend into the spinal cord, terminating in the ventral horn (at all segmental levels).
From the ventral horn,the lower motor neurons go on to supply the muscles of the body.

60
Q

-Theanterior corticospinal tract(after the ___)

A

-one of the divisions after the corticospinal tract divides in the caudal part of the medulla

*Theanterior corticospinal tractremains ipsilateral, descending into the spinal cord.
They then decussate and terminate in the ventral horn of thecervical andupperthoracicsegmental levels.

61
Q

T or F: both the corticospinal tractand Corticobulbar Tract receive the same inputs

A

TRUE

62
Q

Corticobulbar Tract**

  • after originating in primary motor cortex (lateral aspect) the fibers pass through the ____ to the _____
  • termination point
  • after termination point
A

*Fibers pass through the internal capsule to thebrainstem.
*The neurons terminate on the motor nuclei of thecranial nerves.
*Here, they synapse with lower motor neurons, which carry the motor signals to the muscles of thefaceandneck.
Many of these fibers innervate the motor neuronsbilaterally.
Example: fibers from the left primary motor cortex act as upper motor neurons for the right and left trochlear nerves.

There are a few exceptions to this rule:
Upper motor neurons for thefacial nerve(CN VII) have a contralateral innervation.
This only affects the muscles in the lower quadrant of the face – below the eyes
Upper motor neurons for thehypoglossal(CN XII) nerve only providecontralateralinnervation.

63
Q

a common site of cerebrovascular accidents

A

internal capsule

64
Q

reticular formation functions**

A 
Modulatory
Premotor
Keeps you alert
Consciousness
Alarm system
Initiates threat responses
Dry mouth, increased heart rate
*Connected to the thalamus- Not to be confused with the reticular nucleus of the thalamus
65
Q

reticular activating system: what structures participate *

not complete list thinks alex

A

Lateral hypothalamic area (lateral hypothalamus, ventrolateral preoptic area)

66
Q

Lateral hypothalamic area of the reticular activating system *

A

Includes lateral hypothalamus, ventrolateral preoptic area
Orexin system- arousal, wakefulness, appetite

-the reticular activating system is continuous with regions of the thalamus and hypothalamus

67
Q

Spinocerebellar Tracts**

A
  • Unconscious sensation
  • The tracts that carryunconscious proprioceptiveinformation are collectively known as thespinocerebellar tracts.
  • Although we cannot physically acknowledge these signals, Spinocerebellar Tracts help our brain coordinate and refine motor movements.
  • Spinocerebellar Tracts transmit information from the muscles to the cerebellum.
68
Q

Spinocerebellar Tracts pathways (name them)**

A 
There are four individual pathways:
Posterior spinocerebellar tract
Cuneocerebellar tract
Anterior spinocerebellar tract
Rostral spinocerebellar tract
69
Q

Posterior spinocerebellar tract**

A

– Carries proprioceptive information from the lower limbs to the ipsilateral cerebellum.

(a Spinocerebellar Tract)

70
Q

Cuneocerebellar tract**

A

– Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.
(a Spinocerebellar Tract)

71
Q

Anterior spinocerebellar tract**

A

– Carries proprioceptive information from the lower limbs.
Fibers decussate twice – and so terminate in the ipsilateral cerebellum.
(a Spinocerebellar Tract)

72
Q

Rostral spinocerebellar tract**

A

– Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.
(a Spinocerebellar Tract)

73
Q

Cochlear nucleus:

A

Cochlear nucleus: sort of sits on the fence between pons and medulla

74
Q

how many CN are on the brainstem

A

*contains 10 pairs of cranial nerves

75
Q

**Extrapyramidal tracts: modulators

A

*Modulated by various parts, including thevestibular nuclei, cerebellum, nigrostriatal pathway, basal ganglia, and cortex
Modulators considered part of the extrapyramidal system because they modulate motor activity without directly innervating motor neurons.

76
Q

found in the medulla

A

Solitary nucleus:
Spinal Trigeminal nucleus:
Cochlear nucleus:

77
Q

Tectospinal tract function

A

Coordinates movements of the head in relation toVISION STIMULI

78
Q

*Corticospinal Tracts inputs

A

*Corticospinal Tracts receivesa range of inputs: Primary motor cortex, Premotor cortex, Supplementary motor area
They also receive nerve fibers from theSOMATOSENSORY AREA

Somatosensory area plays a role in regulating the activity of the tracts.

79
Q

ascending tracts division

A

Conscious tracts– Comprised of the dorsal column-medial lemniscal pathway, and the anterolateral system.
Unconscious tracts– Comprises of the spinocerebellar tracts

80
Q

*Medial column (division of the brainstem)

A

*Medial column (magnocellular red nucleus)
Large cells
Made of gigantocellular nucleus, pontine tegmental reticular nucleus, cuneiform and subcuneiform nuclei (tegmental nuclei)

Systems Neuroscience (24 decks)

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