CEREBELLUM AND PONS; MEDULLA OBLONGATA

1/11/82, 11 Jan 00, 10 Jan 01, 15 Jan 03, 12 Jan 04, 10 Jan 05, 30Jan08

S&M p 312, Martini’s 4^th: 448-456 (meninges, CSF), 471-474, 6^th: 473-479, 7^th: 453-

PONS: contains two tracts, longitudinal and transverse (p 453-460)

                          longitudinal     communicates between brain stem and cerebrum

                          transverse          between hemispheres of cerebellum

Contains nuclei of four cranial nerves:

             V          trigeminal

             VI        abducens

             VII       facial

             VIII      vestibulocochlear

Pons also contains apneustic and pneumotaxic centers: affects respiration rate.

CEREBELLUM: (p 463) separated from cerebrum by extension of dura mater: tentorium cerebelli

vermis, arbor vitae, 4^th ventricle

Connected to three other portions of brain by peduncles:

             superior cerebellar peduncle       mesencephalon

             middle cerebellar peduncle         pons 

             inferior cerebellar peduncle        medulla oblongata 

Cerebellum can mediate some responses without consciousness

Serves as a coordinating unit

1) initiates voluntary movements

             2) proprioceptors deliver info here

             3) calculates best way to do cerebrum’s will

             4) adjusts motor activity to most accurately perform activity (comparator)

MYELENCEPHALON: same as medulla oblongata. (p 460-461)

             cavity within is lower region of fourth ventricle, continuous with central canal

pyramids on ventral surface of medulla, originate in cerebrum, pass thru peduncles.

these motor tracts go to spinal cord as corticospinal tracts, some cross in medulla

             visible as cross hatching on surface of medulla

MOB FUNCTION: regulates      heart function                                    respiration

                                                       dilation & constriction of vessels      coughing

                                                       swallowing                                        vomiting.

Last four cranial nerves leave fr medulla:

             IX        glossopharyngeal

             X          vagus

             XI        spinal accessory

             XII       hypoglossal

BRAIN STEM:           medulla, pons and mesencephalon 464, 541

Reticular formation:   gray matter within brain stem, info from all sensory tracts. Selects impulses to relay to cortex, raising to consciousness. Responsible for state of arousal. Damage to reticular formation produces coma. (P 555)