Chapter 9 Flashcards
CNS protected by
Glial cells
Bone- Skull, Vertebrae column
Connective tissue- meninges
Cerebrospinal fluid
100 billion neurons and 100 trillion synapses in CNS
Glial cells types
Schwann cells
Oligodendrocytes
Microglia
Astrocytes (most abundant)
Release growth factors
90% of CNS
Astrocytes
Form a link between neurons and non nervous tissue and ECF
develop neurons and synapses
regenerate damaged axons
Maintain homeostasis in EC envir (K+ levels)
Remove Glutamate (toxic) and biogenic amines from synapses
Synthesize and store molecules
Protect from toxins with microglia
Protect from oxidative stress and remove cellular debris
Microglia
Protect CNS from foreign matter, bacteria or dead cells using phagocytosis or cytokines
Protect against oxidative stress
Physical support of CNS
Cranium (Skull)
Vertebral column
Meninges
Cerebrospinal fluid
Meninges
3 connective tissue membranes:
Dura Mater- outermost, tough like leather
Arachnoid Mater- middle layer, weblike and joined with dura
Pia Mater-right above neurons, subarachnoid space filled with cerebrospinal fluid
*Subarachnoid space- between pia Mater and arachnoid Mater filled with CSF
Cerebrospinal fluid
Surrounds CNS and fills ventricles within brain and spinal cord, provides nutrients and remove waste, Maintains ionic composition
Total volume: 125-150mL recycled 3x a day
Choroid plexus produces 400-500mL/Day
Reabsorbed into venous blood in the subarachnoid space by arachnoid villi
Brain cavities (4)
Two C shaped lateral ventricles, connected to the third ventricle by inter-ventricular foramen.
The cerebral aqueduct connects the third ventricle to the fourth ventricle
*Ependymal cells line ventricles and central canal to help circulate CSF
Central canal
Long thin cylindrical cavity that runs the length of spinal cord, lined with ependymal cells
Choroid plexus
The choroid plexus is a plexus of cells that produces the cerebrospinal fluid in the ventricles of the brain. The choroid plexus consists of modified ependymal cells, pia Mater, and capillaries
CNS Blood Supply
Receives 15% of the body’s blood
High demand for glucose and oxygen 20%
Accounts for 50% of all glucose consumed
During starvation or diabetes mellitus, Ketones can supply energy
Blood brain barrier
Hydrophobic molecules diffuses easily (alcohol, gases)
Hydrophilic molecules rely on transport proteins (ions, catecholamines, amino acids)
Glucose (blood brain barrier)
Glucose transports across barrier using GLUT-1 Carriers
Receptors for insulin are located on certain CNS neurons to regulate food intake
Cannot penetrate blood brain barrier
Catecholamines Inorganic ions (H+) Several drugs (Antibiotics)
No transport carrier for these molecules
Gray matter (cerebral cortex)
40% of CNS, site of synaptic communication and neural integration
Makes up external surface of brain and beneath spinal cord
White matter
60% of CNS, white due to Myelinated axons
Below cerebral cortex, consist of areas of gray matter called subcritical nuclei
Organized into bundles or tracts that connect different regions of gray matter
Projection fibers
Tracts conncet the cerebral cortex with more levels of the brain or spinal cord
Fibers connect one region of gray to another
Association fibers
Connect one area of cerebral cortex to another on the same side of the brain
Arcuate fasciculus- connects broca and wernicks area
Commissural fibers
Connect cortical regions on one side of the brain with corresponding cortical regions on the other side
Located in bands of tissue called corpus callosum which connects the cerebral hemispheres
Spinal nerves
Nerves that branch of spinal cord, 31 pairs that exits the vertebral column between to adjacent vertebrae
Cervical nerves
There are 8 pair (C1-C8) emerge from neck region
Thoracic nerves
12 pairs (T1-12) emerge from chest region
Lumbar nerves
5 pairs (L1-L5) emerge from lower back
Conus medullaris: terminal end of the spinal cord which ends around L1-L2
Sacral nerves
5 pairs (S1-S5) emerge from tailbone or coccyx