Nervous system Flashcards
How does segmental organisation of somatic nerves arises
Somatic nerves arise segmentally along developing CNS associated with somites
Developing nerve cells in neural tube extend processes into somite (motor) and neural crest cells migrate and form neurones (sensory)
What means that peripheral nerves have segmental organisation
Caudal half of each somite contians inhibtory molecules preventing nerve fibre outgrowth
What happens in neurulation?
Closure of neural plate (ectoderm) into neural tube
What happens in spina bifida?
Failure of neural tube closure from cervical region (caudally) - some levels of neural tube exposed outside embryo
What is anencephaly?
Rostral failure of neural tube to close in cranial region (brain outside body)
What do neural crest cells form in heart?
Septum between aorta and pulmonary artery
What structure is involved in segmentation of PNS?
Somites
How does neurulation occur?
Neural plate forms from the ectoderm its lateral edges become more elevated, the mid-region becomes depressed
Neural folds approach eachother in the midline where they fuse
What direction does the neural tube close in?
It begins cervically then moves rostally and caudally.
Where do neural crest cells arise from?
Neural crest cells lie on the peak of the neural fold
When do NC begin to dissociate?
When the fold is complete
What do the NC cells transition from?
The cells transition from epithelial back to mesenchymal and go on to form many cell types.
What do dorsally migrating NC cells become?
If they migrate dorsally they form melanocytes in the skin
What do ventrally migrating NC cells become?
If they migrate ventrally they become part of the nervous system (glial cells, Schwann cells, ganglia, adrenal medulla).
What does the layer of ectoderm overlying the neural tube become?
The skin/epidermis
