MCB 135E Discussion GSI: Jason Lowry September 27- October 1

Blood Flow Fetal –Umbilical Vein  Ductus Venosus  IVC  Right Atria  Foramen Ovale  Left Atria  Left Ventricle  Aorta  Coronar y Arteries, Carotid Arteries –Superior Vena Cava  Right Atria  Right Ventricle  Pulmonary Artery  Ductus Arteriosus  Descending Aorta  Umbilical Arteries Adult –Pulmonary Veins  Left Atria  Left Ventricle  Aorta  Inf erio/Superior Vena Cava  Right Atria  Right Ventricle  Pulmonary Arteries

Nervous System Major Functions –Communication with external/internal environment –Regulation of… Major Components –Neurons –Neuroglia –Mylenated nerve fibers –Microglia –Ground Substance –Blood Vessels and CSF

Development of the Nervous System Morphological Development Biochemical Development Functional Development Sexual Differentiation

Morphological Development Neurulation Cells derived from neuroepithelium Know Handout

Neurulation N.S. – Arises from ectoderm on dorsal portion of embryo 3-4 Weeks – Cells proliferate along middle plate 5-6 Weeks – Plate folds to form neural groove 6-7 Weeks – Groove closes into neural tube –Brain develops from anterior portion –Spinal cord develops from the posterior portion

Neural Epithelium Neuroblast –Neuron Spongioblast –Migratory Spongioblast Oligodendria Astrocytes –Astrocytes –Ependyma

Biochemical Development Neuronal Plasticity Energy Sources Role of thyroid hormone

Energy Sources Carbohydrates –Primarily maternal glucose –Stored as glycogen Under influence of glucocorticoids In fetus –Insulin levels high –Insulin sensitivity high –Hypoglycemic Anaerobic Glycolysis –Glyceraldehyde-P- Dehydrogenase Glycolitic enzyme High in postnatal brain During same period the oxidative enzyme –Succinic Dehydrogenase –Much lower

Thyroid Hormone Functions –Promotion of body growth –Development of CNS through: Promotion of neorogenesis Promotion of myelination Promotion of brain metabolism –Stimulates oxygen consumption in all cells Abnormalities –Hypothyroidism Cretinism Short stature, low metabolic rate, skin changes Treatable if given Thyroxine at an early age

Thyroid Hormones

Functional Development Neuronal Connections Differential Development of N.S. –Neurotransmitter activity in different brain regions Perinatal Behavior –Reflexes Respiratory (17-24 weeks) Gastrointestinal (24 th week) Startle (Presence of excessive activity after birth is an indicator of delayed development of certain brain centers) Suckling - Postnatal Education –Better educated appear to live longer with less disability –Several pieces of evidence discussed for this in class

Sexual Differentiation Steroid hormone action on brain development –Androgen action on sexually dimorphic nucleus of the preoptic area (SDN-POA) Male Rats – After puberty  responsible for male behavior, large SDN-POA present Female Rats (low androgen levels) – After puberty -  Small SDN-POA (reversible with androgen treatment) –No lordosis (arching of back when sexually receptive)