(CNS) 2- The spinal cord The Central Nervous System (CNS) 2- The spinal cord Physiology -II Physiology -II PHL 226 PHL 226 Dr. Abdulaziz bin saeedan Dr. Abdulaziz bin saeedan Pharmacy College Pharmacy College 1

Spinal Cord  The spinal cord is a long bundle of neurons and support cells.  It extends from the bottom of the brain down to the space between the first and second lumbar vertebrae.  It is protected by the bony vertebral column.  The length of the spinal cord is much shorter than the length of the vertebral column, extending about 45 cm.  The spinal cord is protected by: o Bone “vertebrae ”. o Spinal meninges. o CSF. 2

 Similar to the brain, the spinal meninges are made up of 3 layers of tissues: 1- The dura mater is the outermost layer, and it forms a tough protective coating.  Between the dura mater and the surrounding bone of the vertebrae is a space called the epidural space, which is filled with fatty tissue and a network of blood vessels. 2- The arachnoid mater is the middle protective layer. 3- The pia mater is the innermost protective layer.  The space between the arachnoid and the underlying pia mater is called the subarachnoid space which contains CSF. 3

Function: (ascending pathways) (descending pathways)  It transmits signals from peripheral organs to the brain (ascending pathways) and from the brain to the peripheral organs (descending pathways). 4

Spinal nerves  They are 31 pair of nerves.  They have no special names.  There are: o 8 cervical. o 12 thoracic. o 5 lumbar. o 5 sacral. o 1 coccygeal. 5