midbrain

Question 1

How long is the midbrain?

Answer 1

The midbrain is about 2 cm (0.8 in) in length.

Question 2

2. What does the midbrain connect?

Answer 2

The midbrain connects the pons and cerebellum to the forebrain.

Question 3

3. What is the cerebral aqueduct?

Answer 3

The cerebral aqueduct is a narrow fluid-filled channel running through the midbrain.

Question 4

4. What are the four colliculi called together?

Answer 4

The four colliculi are called the corpora quadrigemina.

Question 5

5. What is the function of the superior colliculi?

Answer 5

The superior colliculi control visual reflexes.

Question 6

6. What is the function of the inferior colliculi?

Answer 6

The inferior colliculi control auditory reflexes.

Question 7

7. Where does the trochlear nerve (CN IV) emerge?

Answer 7

The trochlear nerve emerges below the inferior colliculi.

Question 8

8. How does the trochlear nerve travel after emerging?

Answer 8

The trochlear nerve wraps around the midbrain to the cavernous sinus.

Question 9

9. What does the superior brachium connect?

Answer 9

The superior brachium connects the superior colliculus to the lateral geniculate body and optic tract.

Question 10

10. What does the inferior brachium connect?

Answer 10

The inferior brachium connects the inferior colliculus to the medial geniculate body.

Question 11

11. What is the interpeduncular fossa?

Answer 11

The interpeduncular fossa is a deep depression between the crus cerebri.

Question 12

12. What is the posterior perforated substance?

Answer 12

The posterior perforated substance is a region with many small blood vessels.

Question 13

13. Where does the oculomotor nerve (CN III) emerge?

Answer 13

The oculomotor nerve emerges from the medial side of the crus cerebri.

Question 14

14. What are the two parts of the cerebral peduncles?

Answer 14

The two parts of the cerebral peduncles are the crus cerebri (front) and the tegmentum (back).

Question 15

15. What does the crus cerebri contain?

Answer 15

The crus cerebri contains descending tracts.

Question 16

16. What does the tegmentum contain?

Answer 16

The tegmentum contains nuclei and pathways.

Question 17

17. Where is the substantia nigra located?

Answer 17

The substantia nigra is between the crus cerebri and tegmentum.

Question 18

18. What is the function of the substantia nigra?

Answer 18

The substantia nigra controls muscle tone and connects with the cortex, spinal cord, and basal nuclei.

Question 19

19. What is the function of the cerebral aqueduct?

Answer 19

The cerebral aqueduct connects the third and fourth ventricles.

Question 20

20. What lines the cerebral aqueduct?

Answer 20

The cerebral aqueduct is lined with ependymal cells.

Question 21

21. What is the tectum?

Answer 21

The tectum is the part of the midbrain posterior to the cerebral aqueduct.

Question 22

22. What does the tectum contain?

Answer 22

The tectum contains the superior and inferior colliculi for visual and auditory processing.

Question 23

23. What is located in the inferior colliculus?

Answer 23

The inferior colliculus contains a gray matter nucleus.

Question 24

24. What pathway is the inferior colliculus a part of?

Answer 24

The inferior colliculus is part of the auditory pathway.

Question 25

25. Where does the inferior colliculus receive fibers from?

Answer 25

The inferior colliculus receives fibers from the lateral lemniscus.

Question 26

26. Where does the inferior colliculus send fibers?

Answer 26

The inferior colliculus connects to the medial geniculate body via the inferior brachium.

Question 27

27. Where is the trochlear nucleus located?

Answer 27

The trochlear nucleus is located in the central gray matter.

Question 28

28. How do trochlear nerve fibers exit?

Answer 28

The trochlear nerve fibers exit below the inferior colliculi and cross completely in the superior medullary velum.

Question 29

29. Where is the mesencephalic nucleus of the trigeminal nerve found?

Answer 29

The mesencephalic nucleus of the trigeminal nerve is found next to the cerebral aqueduct.

Question 30

30. Where does the superior cerebellar peduncle decussate?

Answer 30

The superior cerebellar peduncle decussates in the central part of the tegmentum before the cerebral aqueduct.

Question 31

31. Where is the reticular formation in the midbrain?

Answer 31

The reticular formation is located laterally in the midbrain tegmentum.

Question 32

32. Where is the medial lemniscus in the midbrain?

Answer 32

The medial lemniscus is located behind the substantia nigra.

Question 33

33. Where are the spinal and trigeminal lemnisci in the midbrain?

Answer 33

The spinal and trigeminal lemnisci are lateral to the medial lemniscus.

Question 34

34. Where is the lateral lemniscus in the midbrain?

Answer 34

The lateral lemniscus is behind the trigeminal lemniscus.

Question 35

35. What are the three descending tracts in the crus cerebri?

Answer 35

The descending tracts in the crus cerebri are corticospinal, corticonuclear, and corticopontine fibers.

Question 36

36. Where are corticospinal and corticonuclear fibers located in the crus cerebri?

Answer 36

Corticospinal and corticonuclear fibers are in the middle part of the crus cerebri.

Question 37

37. Where are frontopontine fibers located in the crus cerebri?

Answer 37

Frontopontine fibers are in the medial part of the crus cerebri.

Question 38

38. Where are temporopontine fibers located in the crus cerebri?

Answer 38

Temporopontine fibers are in the lateral part of the crus cerebri.

Question 39

39. What is the function of the superior colliculus?

Answer 39

The superior colliculus controls visual reflexes.

Question 40

40. What are the three main inputs to the superior colliculus?

Answer 40

The superior colliculus receives input from the optic nerve, visual cortex, and spinotectal tract.

Question 41

41. What are the two major outputs of the superior colliculus?

Answer 41

The superior colliculus sends output via the tectospinal and tectobulbar tracts.

Question 42

42. What reflexes does the superior colliculus control?

Answer 42

The superior colliculus controls reflex movements of the eyes, head, and neck.

Question 43

43. Where does the light reflex pathway end?

Answer 43

The light reflex pathway ends in the pretectal nucleus.

Question 44

44. How does the light reflex pathway reach the eye muscles?

Answer 44

The pathway relays to the Edinger-Westphal nucleus → oculomotor nerve → eye muscles.

Question 45

45. Where is the red nucleus located?

Answer 45

The red nucleus is located between the cerebral aqueduct and the substantia nigra.

Question 46

46. Why does the red nucleus appear reddish?

Answer 46

The red nucleus appears reddish due to iron pigment and rich blood supply.

Question 47

47. What are the three major afferent (input) connections of the red nucleus?

Answer 47

The red nucleus receives input from the cerebral cortex, cerebellum, and basal nuclei.

Question 48

48. How does the cerebral cortex connect to the red nucleus?

Answer 48

The cerebral cortex connects to the red nucleus via corticospinal fibers.

Question 49

49. How does the cerebellum connect to the red nucleus?

Answer 49

The cerebellum connects to the red nucleus via the superior cerebellar peduncle.

Question 50

50. What are the four major efferent (output) pathways from the red nucleus?

Answer 50

The red nucleus sends output to the spinal cord (rubrospinal tract), reticular formation (rubroreticular tract), thalamus, and substantia nigra.

Question 51

51. Where is the reticular formation located in the midbrain?

Answer 51

The reticular formation is in the tegmentum, lateral and posterior to the red nucleus.

Question 52

52. What is the function of the midbrain reticular formation?

Answer 52

The midbrain reticular formation plays a role in arousal and motor control.

Question 53

53. What are the main functions of the midbrain?

Answer 53

The midbrain relays sensory and motor information, controls vision and hearing reflexes, and contains important pathways for movement and coordination.