Lectures 9-16 w/ corresponding chapters

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Biological Sciences
Catherine Nash

Physiology Midterm 2 Review Lecture 9 o Central Nervous System = brain & spinal cord (contains neurons that communicate within the CNS and the rest of the body) o Peripheral Nervous System = Autonomic (involuntary) Nervous System (cardiac, smooth muscle(liver), adipose tissue(fat), endocrine system), Enteric Nervous System(digestive) & Somatic Motor Division(skeletal muscles) Evolution of the Brain o Lines of the Jellyfish represent the nervous system; In jelly fish the nerve net functions together to co- ordinate movement o In flat worms, nerve cords represent bundles of nerves in the brain and the primitive brain is a collection of cell bodies within the head; Flat worms = simple nervous system. Nerve cell bodies restricted to the head. o Annelids and segmented worms have clusters of nerve cells (ganglia = swellings where synapse are) through the body o Allows functions equivalent to spinal reflexes(involuntary) in humans to be carried out o In vertebrates the forebrain is more complex e.g structures like cortex and cerebellum o Animals increase in complexity and specialisation as move up phylogenetic tree o The cortex increases in size in higher mammals. Thicker cortexs help us to perform higher processes(awareness, analysis of perception) the cortex decodes information and decides how it will respond Development of the Nervous System o During the developmental stage in the fetus, 2 cells divide and form the neural tube( which ultimately becomes the CNS o Neural Plate: region in the embryo that forms the CNS o On day 20 of the embryonic stage, cells in the neural plate move upwards towards the neural crest and what this does is it causes a neural groove to form o cells migration elevates the neural crest and deepens the neural groove o The neural crest eventually increases in size until it flops over onto each other and makes a neural tube o Lumen forms the central cavity (ventricles or gapsspaces) of the CNS o Lining of lumen becomes gap function cells and neural stem cells o Outer layers become neurons and glia(supportive cells) (central nervous system (CNS)) o Neural crest becomes sensory and motor neurons of (peripheral nervous system (PNS)) o Stem cells are cells that can take on any form that are present or developing through a lifetime o At week 4 cerebrum (cortex) is similar in size to other brain regions and by week 6, 7 major regions of the CNS have formed o By week 11, the CNS look similar to that that we see at birth www.notesolution.com o Week 11: Growth of cerebrum (cortex) accelerates o At birth the cerebrum surrounds the diencephalon, midbrain and pons o Cranial nerves: Carry information to and from brain from entire body o At birth, the cerebrum becomes invaginated which creates a large surface area for neurons etc.. to be maintained in our brain How the Brain is Protected and Maintains its Function 1. Bone protects the Central Nervous System (CNS): CRANIUM protects the brain and VERTICAL COLUMN protects the spinal cord * 3 protective layers surround the brain: Bone Connective tissue Fluid 2. Meniges(connective tissue) support and protect the CNS *3 layers: 1. Dura mater (thickest). Contains veins that drain blood (away from the brain) through sinuses (cavities); forms the outside protective layer 2. Arachnoid mater (loose) 3. Pia mater (thin); Tightly associated with the brain. Contains arteries that supply blood to the brain. Beneath pia matter is EC fluid that bathes neurons 3. Cerebrospinal fluid (CSF) cushions the CNS o Provides physical and chemical protection o Compared to EC and plasma, the CSF has a Lower [K ] and [Ca ], higher [H ], same [Na ] o Little protein; no red blood cells; red blood cells are toxic to neurons because of high Iron concentration o CSF is secreted from the choroid plexus into ventricles o flows through subarachnoid space to cushions brain and spinal cord o CSF and EC communicate through pia mater and ventricle membranes o CSF flows through the subarachnoid space between pia mater and arachnoid membrane o CSF is reabsorbed into blood villi (hair-like structures) on arachnoid membrane o Allows removal of wastes (toxins, metabolites) o Entire volume of CSF (approx 400ml) is replaced 3 times day o To discover any type of illness occurring in the CNS, doctors perform a lumbar puncture: removal of CSF from subarachnoid space at lower end of spinal column 4. Ventricles of the brain www.notesolution.com
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