midbrain anatomy

Question 1

MESENCEPHALON-MIDBRAIN

Answer 1

rostral p. of brainstem.
(oblongata, pons, mesencephalon)

-joins pons w. diencephalon and hemispheres
-conn. w cerebellum thru sup. cerebellar penduncles

Question 2

ventral surf

Answer 2

1) crura cerebri:
emerge from hemispheres and enter pons
-anteriorly, crura are crossed by optic tracts

-oculomotor nerve emerge on medial bordar of crura

-crura cerebri borders interpeduncular fossa
marked by minute openings, for passage of central branches of circulus arteriosus

Question 3

dorsal surf

Answer 3

TECTUM

consists of:
sup and inf colliculi
-colliculi conn. to diencephalon by brachium of sup. colliculus and brachium of inf. colliculus,

-Trochlear nerves arise from inf. colliculi

Question 4

internal structure midbrain

Answer 4

on cross section:
1) tectum
2) tegmentum
3) crura cerebri

Question 5

Tectum of midbrain

Answer 5

has visual + audit. reflex centers

1) Superior colliculi:
contained gay matter, center of visual rflxes
(in response to visual stimuli)
Receives aff. fibers from visual retina + cortex. Spinal cord (spinotectal tract)

Sends eff. fibers to:
motor nuclei of cranial nerves (tectonuclear)
motor neurons in s. nerves (tectospinal)

2)Pretectal nucleus:
lies rostral to sup. colliculi
center for pupillary light rflx
-fær aff. fibers frá retina, via optic tract
-sends eff. fibers to Edinger-Wesphal nucleus (parasymt. nucleus of occulomotor nerve)

3) inf. colliculi:
gray matter of it constitutes a p. of aud. pathway.
Represents auditory rflx centers
(control of rflx movem. head/body in response to aud. stimuli)

Afferent fibers:
lateral meniscus (auditory pathway)

Efferent fibers:
-to diencephalon-medial geniculate body(nucleus)
-s. cord (tectospinal tract)
-nuclei of cranial nerves (tectonuclear tracts)