Embryo Flashcards
What is segmentation?
Division of brain and spinal cord.
What is mesencephalic flexure?
Bend between the first two parts of the brain in an embryo.
What causes folding at the cranial end of the embryo?
Dramatic growth of the brain
How many divisions are in the early brain and what are they called?
Three. Prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain).
What does the cavity of the neural tube form?
The ventricles and central canal of the spinal cord
When going from 3 to 5 brain vesicles, what are the 5 vesicles?
Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon.
What does the telencephalon form?
Cerebrum, from lateral ventricles.
What does the diencephalon form?
Epithalamus, thalamus, hypothalamus.
What does the mesencephalon form?
Cerebral peduncles, superior colliculi, inferior colliculi
What forms from the metencephalon?
Pons and cerebellum
What forms from the myelencephalon?
Medulla oblongata
What connect the right and left alar (dorsal) plates? What connect the bilateral basal (ventral) plates?
The roof plate, the floor plate.
What is the chemical that signals the ventral part of the neural tube? Dorsal part?
Sonic hedgehog, BMP4.
What chemical does the notochord emit?
Sonic hedgehog (shh)
What surrounds the central canal of the neural tube?
Undifferentiated neuroepithelial cells surrounding the central canal
What are the different types of segmentation?
Longitudinal- brain from spinal cord. Cross sectional- define areas for gray matter (cell bodies of neurons) and white matter (axons).
where is the white and gray matter located in the spinal cord? In the brain?
Spinal cord- white matter (on the outside), gray matter ( on the inside). Brain- white matter (inside), gray matter (outside).
What does the early neural tube consist of?
Pseudostratified columnar (neuro) epithelium. Nuclei appear to be in multiple layers. High degree of mitotic activity. Cell division & maturation result in population of bipotential progenitor cells, which give rise to either neuronal or glial progenitor cells.
What do bipotential progenitor cells in the neural tube lead to?
Either neuronal or glial progenitor cells.
What do neuronal progenitor cells make? Glial progenitor cells?
Neuron. Neuroglia.
What is the function of the neuron?
Transmit electrochemical signals.
What is the function of neuroglia?
Supporting cells of the CNS. Insulate, nourish, support and protect neurons.
What are ependymoblasts? Where are they located?
Cells in the innermost layer of the neural tube. These cells differentiate into ependyma.
What do glial cells give rise to?
Oligodendrocytes, astrocytes, ependymal and special glial cells.
Which zone gives rise to neurons and neuroglia?
Ventricular zone (most medial)
What is in the intermediate mantle (cortical zone)?
Post-mitotic neurons and glioblasts, which will become the inner gray matter (contains neuronal cell bodies and neuroglia).
What makes up the white matter (marginal zone)?
Neuronal processes that surround the developing gray matter
What is in the dorsal plate of the spinal cord? Ventral plate?
Sensory input (afferent). Motor output (efferent)
What are the neural crest derived tissues?
Melanocytes, dorsal root ganglia, spinal nerves, sympathetic ganglia.
What are the neural crest migration pathways?
Lateral and medial pathways, which go on either side of the dermomyotome.
What types of ganglia are formed by the neural crest?
Sensory (dorsal root) ganglia, motor (autonomic, sympathetic chain, parasympathetic)
What is in the central nervous system?
White matter (myelinated axons in tracts), gray matter (neuronal cell bodies and neuroglia)
What is a tract in the CNS?
Bundles of axons originating and ending in CNS
What are neuronal cell bodies located in the CNS called?
Nuclei
What makes up the peripheral nervous system?
12 cranial nerves, 31 spinal nerves, other nerves, nerve endings, and ganglia (cell bodies in PNS)
What are the two parts of the PNS?
Somatic and autonomic nervous systems
What is the somatic nervous system?
Actions carried out voluntarily, sensations are consciously received.
What is the autonomic nervous system?
Actions carried out involuntarily, sensations aren’t consciously perceived (maintains homeostasis)
What are the four types of information to/from the spinal cord?
General somatic afferent, general somatic efferent, general visceral afferent, general visceral efferent
What does a ventral root contain?
General visceral efferent and general somatic efferent (motor)
What do dorsal rami go to?
Epaxial back muscles (deep back), muscle and skin also.
What do ventral rami go to?
Hypaxial muscles, lateral and entrap body wall.
What do afferent nerves do?
Carry signals from the peripheral to the CNS, via dorsal roots. Have receptors for touch, pressure, temperature, pain, proprioception
What do efferent neurons do?
Carry impulses away from CNS to skeletal muscle
Explain a dorsal rhizotomy and why it’s performed.
Nerves separated and identified by electrical stimulation. Some sensory nerve fibers are then cut. Can do this for cerebral palsy or chronic pain (radiofrequency rhizotomy)
What is the condition where a person can’t feel pain?
Congenital insensitivity to pain (CIP). Rare, can be bc of voltage-gated Na+ channel (SCN9A) in dorsal root ganglia. Five different kinds have been identified.
What are characteristics of the autonomic nervous system?
Involuntary and automatic, not consciously perceived, two neurons in path from CNS to effector, one neuron for somatic, the two neurons in the NSR preganglionic and postganglionic.
What muscles do the autonomic nervous system affect efferently?
Smooth and cardiac muscle, also glands.
What are the two branches of the ANS?
Parasympathetic and sympathetic
