Lecture 22 - Brain Evolution and General Structure

Question 1

When does the nervous system formation occur during the embryonic stage?

Answer 1

• End of second week to end of eighth week
• Superior (anterior or cranial) neuropore closes by day 27
• Inferior (posterior or caudal) neuropore closes by day 30.

Question 2

What are the parts of the tripartite brain?

Answer 2

• Prosencephalon
• Mesencephalon
• Rhombencephalon

Question 3

What are the parts of the pentapartite brain?

Answer 3

• Prosencephalon:
  
  • Telencephalon (most anterior)
  • Diencephalon

-Mesencephalon

• Rhombencephalon:
  
  • Metencephalon
  • Myelencephalon

Question 4

In general, what is the brainstem made up of?

Answer 4

• A mixture of long fiber pathways
• 10 of 12 cranial nerves enter and leave through the brainstem.

-Well-organized nuclei:
Most of the nuclei are related directly to:
-Cranial nerve functions
-Motor control pathways

-A network of cells which forms the brainstem reticular formation

Brainstem components:

• Medulla
• Pons
• Midbrain

Question 5

What are the descending tracts in medulla?

Answer 5

• Corticospinal
• Spinal tract V
• Medial longitudinal fasciculus
• Tectospinal
• Rubrospinal

Question 6

What are the ascending tracts in medulla?

Answer 6

• Medial Lemniscus
• Spinothalamic tract
• Spinoreticular tract
• Spinocerebellar tract
• Cuneocerebellar tract

Question 7

What are additional components of the medulla?

Answer 7

• Cranial nerve nuclei VIII-XII

- Inferior cerebellar peduncles

Question 8

What are the vital and non-vital reflex centers found in the medulla?

Answer 8

Vital reflex centers:

• Cardiac center:
  
  • Inhibitory via CN X.
  • Excitatory via T1-T5.
• Medullary rhythmicity center
• Vasomotor center
• Centers for coordination of head movement and swallowing

Non-vital reflex center:

• Swallowing
• Vomiting
• Coughing
• Sneezing
• Hiccuping

Question 9

Where are the inferior olivary nuclei and what are their functions?

Answer 9

-Receive input from most motor areas of the brain and spinal cord

Functions:

• Balance
• Coordination
• Sound impulse modulation

Question 10

What are the cranial nuclei in the pons?

Answer 10

-V, VI, VII, VIII (part)

Question 11

What are the respiratory centers in the pons?

Answer 11

• Pneumotaxic

- Apneustic

Question 12

What are the cranial nuclei in the midbrain?

Answer 12

-CN nuclei III and IV.

Question 13

What is the function of the red nucleus?

Answer 13

-Involved in unconscious regulation and coordination of motor activities

Question 14

What are the locations and functions of the superior and inferior colliculi?

Answer 14

They are both found in the tectum of the midbrain

Functions of the Superior colliculi:

• Visual reflexes
• Receive input form the eyes, inferior colliculi, skin, cerebrum
• Fibers project to cranial nerve nuclei and to superior cervical portion of spinal cord.
  
  • Stimulate motor neurons involved in turning eyes and head
• Involved in visual tracking of moving objects

Functions of the Inferior colliculi:
-Auditory and olfactory reflexes

Question 15

Where is the Periaquaductal gray and what are its functions?

Answer 15

-The gray matter surrounding the cerebral aquaduct

Functions:

• Involved in pain suppression
• Coordinates somatic and autonomic reactions to pain, threats, and emotions.
• Activity results in flight-or-fight reactions and in vocalization during laughing and crying.