Development of the Nervous System (Prof Price) Flashcards
What are the 3 main functions of the nervous system ?
Sensation, integration and initiation of motor activity.
What is the role of the CNS (brain + spinal chord) ?
- Receives sensory information Integrates
- Generates motor activity
- Controls consciousness and perception
What is the role of the PNS (all nerves and ganglia outside brain and spinal chord) ?
Carries sensory information to CNS from periphery (via afferent nerves)
Carries motor information from CNS to periphery (via efferent nerves)
Wha are ganglia ?
Ganglia are collections of nerve cell bodies.
How many spinal nerves supply the trunk and limbs ?
32 pairs:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
How many cranial nerves are there ?
What do they control ?
The 12 cranial nerves control many neck and head functions (but not only e.g. X (vagus) controls intestines).
How do white and get matter proportions vary in the spinal chord ?
At the top of the spinal chord (cervical level), white matter is more abundant because the fibers innervating the whole body progressively join up until they reach C1 (so the axons add up).
What does the diencephalon contain ?
The thalamus and the hypothalamus.
What does the brainstem contain ?
The midbrain, the pons and the medulla.
How does the brain change during development ?
The CNS develops initially as a simple hollow tube.
The cerebral hemispheres develop as outgrowths on either side from the cranial end of this tube.
As they grow they sweep back over the surface of the tube “hiding” the central core of the developing brain.
What did Samuel Taylor Coleridge say about developmental biology in 1803 ?
“The history of man for the nine months preceding his
birth would be far more interesting and contain events of greater moment than all threescore and ten years that follow it.”
What did comparative embryologists, such as Pander (1794-1865), von Baer (1792-1876), and Rathke (1793-1860), recognize concerning embryonic development ?
That different species undergo similar stages of development.
What are the steps between fertilization and formation of a larva.
Fertilization is followed by cleavage divisions that break up the large egg into smaller cells, creating a fluid filled sphere called the blastula. The multilayered structure of the larva is created by a coordinated series of cell movements called gastrulation. At this point the three germ layers (ectoderm, mesoderm and endoderm) become apparent, which subsequently form the tissues..
Which scientist discovered germ layers ?
Christian Pander (1794-1865) while studying chick embryos.
What are the characteristics of germ layers ?
They are found in all triploblastic embryos and each germ layer forms similar tissue types in all animals. Some phyla, such as porifera (sponges), cnidarians (sea anemones, hydra, jellyfish) and ctenophors (comb jellies) lack true mesoderm and are considered diploblastic animals. Germ cells (future gametes) are classified separately.
What is differentiation ?
The process whereby cells acquire their functional characteristics.
Quote a scientist that illustrates the physical similarity of certain embryos.
“I have two small embryos preserved in alcohol, that I forgot to label. At present I am unable to determine the genus to which they belong. They may be lizards, small birds, or even mammals.” Karl Ernst von Baer (1828)
What experiment did Hans Spemann (1869-1941) & Hilde Mangold (1898-1924) carry out in 1924 that revealed the principle of neural induction ?
Shaman and Mangold transplanted the prospective
notochord of a newt gastrula into the opposite side of a similarly staged host. They used newt species with different levels of pigmentation so that they could follow the transplanted cells. Remarkably, a conjoined twin was formed in which the transplant formed the notochord and parts of the nervous system. However, most of the nervous system was formed by host cells that would otherwise have formed epidermis. Thus the transplant has changed the fate of host cells from epidermis to neural. Only the propsective notochord could induce a conjoined twin and Spemann coined the term “organizer” to describe this region of the amphibian gastrula.
How does the dorsal mesoderm migrate during gastrulation ?
During gastrulation the dorsal mesoderm (notochord) migrates anteriorly beneath the dorsal ectoderm, releasing “signals” that induce the nervous system. In the absence of these signals the dorsal ectoderm will form epidermis. In Spemann & Mangolds experiment, dorsal mesoderm was introduced on the ventral side of the embryo, inducing a second nervous system in the ventral ectoderm.
What is induction ?
The process whereby a cell or tissue signals to another cell or tissue in the embryo, thereby affecting the development of the responding cell or tissue.
What is competence ?
The ability of a cell or tissue to respond to an inducing signal - embryonic tissues only remain competent for a limited period of time.
From what germ layer does the NS derive ?
The ectoderm.
What is neurulation ?
The process of how the ectoderm begins to give rise to the Nervous System. It happens when the notochord instructs the ectoderm to form the rural tube.
Are the CNS and PNS formed together ?
No, they are formed separately.
