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Neuroscience MD2 > midbrain ppt > Flashcards

midbrain ppt Flashcards

1
Q

What is the midbrain?

A

The midbrain is the shortest segment of the brainstem, measuring approximately 2cm in length.

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2
Q

Where is the midbrain situated?

A

in the posterior cranial fossa, with its superior part extending above the tentorial notch.

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3
Q

What are the functions of the midbrain?

A

It enables auditory and ocular reflexive movements, controls pain, mood, and breathing, promotes survival instincts, and provides a passageway for pathways between the cerebral cortex and spinal cord.

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4
Q

What structures lie between the midbrain?

A

The midbrain lies between the thalamus (rostrally) and pons (caudally).

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5
Q

What marks the anterior surface of the midbrain?

A

The anterior surface is marked by the two stalks called the cerebral peduncles.

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6
Q

What is the interpeduncular fossa?

A

The interpeduncular fossa is bounded by the cerebral peduncles and contains important vascular and neural structures.

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7
Q

What is the tectum?

A

The posterior surface of the midbrain is called the tectum, which features four tubercles known as the superior and inferior colliculi.

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8
Q

What is the role of the periaqueductal gray matter?

A

The periaqueductal gray modulates pain by releasing endogenous opioids and connects to the somatosensory areas of the cerebral cortex.

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9
Q

What are the major parts of the midbrain?

A

The midbrain consists of two major parts: the cerebral peduncles and the tectum.

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10
Q

What is the function of the red nucleus?

A

The red nucleus adjusts the movements of the upper limbs to maintain body balance.

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11
Q

What pathways does the midbrain provide passage for?

A

The midbrain provides passage for several ascending pathways including the superior cerebellar peduncles and various lemnisci.

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12
Q

What is the substantia nigra?

A

The substantia nigra is a semilunar lamina of heavily pigmented neurons that contributes to the control of movements.

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13
Q

What cranial nerve nuclei are located in the midbrain?

A

The nuclei of the oculomotor (CN III), trochlear (CN IV), and trigeminal nerves (CN V) are located near the periaqueductal gray matter.

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14
Q

What is the function of the oculomotor nerve nucleus?

A

It provides fibers for the innervation of all extraocular muscles except for the superior oblique and lateral rectus muscles.

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15
Q

What is the role of the accessory oculomotor nucleus?

A

It innervates the ciliary and sphincter pupillae muscles, enabling miosis of the pupil.

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16
Q

What is the function of the trochlear nerve nucleus?

A

It innervates the superior oblique muscle.

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17
Q

What is the role of the mesencephalic nucleus of the trigeminal nerve?

A

It receives proprioceptive information from the muscles of the face.

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18
Q

What are the components of the red nucleus?

A

The red nucleus consists of the caudal (magnocellular) and rostral (parvocellular) portions.

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19
Q

What is the rubrospinal tract?

A

The rubrospinal tract originates from the magnocellular part of the red nucleus and adjusts upper limb movements.

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20
Q

What does the medial longitudinal fasciculus connect?

A

It connects the oculomotor, trochlear, abducens, Edinger-Westphal, vestibular, reticular, and spinal accessory nuclei.

21
Q

What sensory information does the medial lemniscus carry?

A

It carries information about vibration, touch, proprioception, and pressure to the thalamus.

22
Q

What is the function of the trigeminal lemniscus?

A

It carries tactile, pain, and temperature sensations from the head to the thalamus.

23
Q

What does the lateral lemniscus convey?

A

It conveys auditory information from the cochlear nucleus to the contralateral inferior colliculus.

24
Q

What is the location of the substantia nigra?

A

The substantia nigra is located between the crus cerebri and the mesencephalic tegmentum.

25
Q

What gives the substantia nigra its distinguishable dark color?

A

The dark color comes from the pigment neuromelanin.

26
Q

What is the function of the substantia nigra?

A

The substantia nigra is part of the extrapyramidal motor system, contributing to the control of movements by connecting with the basal ganglia.

27
Q

What are the two parts of the substantia nigra?

A

The substantia nigra consists of the dorsal pars compacta and the ventral pars reticulata.

28
Q

What is the role of the dorsal pars compacta?

A

It is composed of neurons that produce dopamine and connects with the striatum via the nigrostriatal pathway.

29
Q

What is the significance of the loss of dopaminergic neurons in the pars compacta?

A

The loss plays a central role in the development of Parkinson’s disease and other parkinsonian syndromes.

30
Q

What does the ventral pars reticulata mainly produce?

A

It mainly produces the inhibitory neurotransmitter GABA.

31
Q

What is the function of the tectum?

A

The tectum consists of relay nuclei called the corpora quadrigemina.

32
Q

What is the role of the superior colliculi?

A

The superior colliculi process visual information and facilitate ocular reflexes.

33
Q

What is an example of a function of the superior colliculi?

A

They help cover your eyes upon a sudden onset of brightness.

34
Q

What is the function of the inferior colliculi?

A

The inferior colliculi process auditory information and are involved in reflexive movements.

35
Q

What is an example of a reflexive movement processed by the inferior colliculi?

A

Turning your head towards the source of a sudden and unexpected sound.

36
Q

What arteries supply the midbrain?

A

The midbrain is supplied by the superior cerebellar artery, paramedian branches of the basilar artery, and the posterior cerebral artery.

37
Q

What is Weber’s syndrome?

A

Weber syndrome is a midbrain stroke syndrome involving oculomotor fascicles, causing ipsilateral third nerve palsy with contralateral hemiparesis.

38
Q

What commonly causes Weber’s syndrome?

A

It most commonly results from the occlusion of a branch of the posterior cerebral artery.

39
Q

What are the two main motor nuclei of the oculomotor nerve?

A

The main motor nucleus and the accessory parasympathetic nucleus.

40
Q

Where is the main motor nucleus located?

A

It is located in the tectum portion of the midbrain at the level of the superior colliculus.

41
Q

What does the main motor nucleus supply?

A

It supplies all extraocular muscles except the lateral rectus and superior oblique muscles, and the levator palpebrae superioris.

42
Q

Where is the accessory parasympathetic nucleus located?

A

It is situated posterior to the main motor nucleus.

43
Q

What does the accessory parasympathetic nucleus supply?

A

It supplies the constrictor pupillae of the iris and the ciliary muscles.

44
Q

How do the nerve fascicles travel in the midbrain?

A

They travel forward and lateral through the red nucleus and converge at the interpeduncular fossa before exiting the midbrain.

45
Q

What can lesions in the midbrain present with?

A

Lesions can present with either partial or complete third nerve palsy.

46
Q

What do lesions in the lower midbrain affect?

A

They affect the extraocular muscles but spare the pupils.

47
Q

What is a common cause of Weber syndrome?

A

A lesion in the ventromedial portion of the midbrain.

48
Q

What are common antecedent conditions associated with Weber syndrome?

A

Hypertension, diabetes, and hypercholesterolemia.

Neuroscience MD2 (4 decks)

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