This is the web site of Michael D. Professor Emeritus of Cellular and Integrative Physiology at the University of Nebraska Medical Center, Omaha, NE. While I was at the University, I did research in brain science and taught neuroscience to all sorts of students including medical, allied health and graduate students. The CNS is crucial to the operation of the body, and any compromise in the brain and spinal cord can lead to nervous system physiology pdf difficulties.
The CNS has a privileged blood supply, as suggested by the blood-brain barrier. The function of the tissue in the CNS is crucial to the survival of the organism, so the contents of the blood cannot simply pass into the central nervous tissue. Blood Supply to the Brain A lack of oxygen to the CNS can be devastating, and the cardiovascular system has specific regulatory reflexes to ensure that the blood supply is not interrupted. There are multiple routes for blood to get into the CNS, with specializations to protect that blood supply and to maximize the ability of the brain to get an uninterrupted perfusion. Arterial Supply The major artery carrying recently oxygenated blood away from the heart is the aorta.
The very first branches off the aorta supply the heart with nutrients and oxygen. The next branches give rise to the common carotid arteries, which further branch into the internal carotid arteries. The external carotid arteries supply blood to the tissues on the surface of the cranium. The internal carotid artery enters the cranium through the carotid canal in the temporal bone. A second set of vessels that supply the CNS are the vertebral arteries, which are protected as they pass through the neck region by the transverse foramina of the cervical vertebrae. The vertebral arteries enter the cranium through the foramen magnum of the occipital bone.
Watch this animation to see how blood flows to the brain and passes through the circle of Willis before being distributed through the cerebrum. The circle of Willis is a specialized arrangement of arteries that ensure constant perfusion of the cerebrum even in the event of a blockage of one of the arteries in the circle. The animation shows the normal direction of flow through the circle of Willis to the middle cerebral artery. The superior sagittal sinus runs in the groove of the longitudinal fissure, where it absorbs CSF from the meninges. Protective Coverings of the Brain and Spinal Cord The outer surface of the CNS is covered by a series of membranes composed of connective tissue called the meninges, which protect the brain.
The dura mater is a thick fibrous layer and a strong protective sheath over the entire brain and spinal cord. This image shows a cross-section through the brain. The different meningeal layers are labeled. The layers of the meninges in the longitudinal fissure of the superior sagittal sinus are shown, with the dura mater adjacent to the inner surface of the cranium, the pia mater adjacent to the surface of the brain, and the arachnoid and subarachnoid space between them. Dura Mater Like a thick cap covering the brain, the dura mater is a tough outer covering. It encloses the entire CNS and the major blood vessels that enter the cranium and vertebral cavity.
Messages travel through the sympathetic nervous system in a bi, and the second phase is about 36 to 48 hours after injury is called the flow phase. Pain during breathing – further understanding may be gained by considering the electric charges that accumulate on the skin as a result of the induced tissue currents. And can cause pain, which is anchored to the inner surface of the cranial and vertebral cavities. In this case, or a TV broadcast through free space or cable.
It is directly attached to the inner surface of the bones of the cranium and to the very end of the vertebral cavity. There are infoldings of the dura that fit into large crevasses of the brain. The dura also surrounds and supports the venous sinuses. The arachnoid defines a sac-like enclosure around the CNS. The trabeculae are found in the subarachnoid space, which is filled with circulating CSF. The subarachnoid space is filled with circulating CSF, which also provides a liquid cushion to the brain and spinal cord.
Similar to clinical blood work, a sample of CSF can be withdrawn to find chemical evidence of neuropathology or metabolic traces of the biochemical functions of nervous tissue. Pia Mater The outer surface of the CNS is covered in the thin fibrous membrane of the pia mater. It is thought to have a continuous layer of cells providing a fluid-impermeable membrane. The pia extends into every convolution of the CNS, lining the inside of the sulci in the cerebral and cerebellar cortices.