8: Central Nervous System Flashcards
The Nervous System: Central Nervous System
General anatomy of the central nervous system
- Consist of brain and spinal cord
- soft tissue = vulnerable to damage by physical traumas
- protected by glial cells, bone, connective tissue and CSF
General anatomy of the central nervous system (2)
- Glial cells
- Physical support of the CNS
- Blood supply to the CNS
- The blood-brain barrier
- Gray matter and white matter
- 90% of CNS
- release growth factors involved in the development of nervous system
- communicate with neurons
Glial cells
Five types of glial cells
- Astrocytes
- Ependymal cells
- Microglia
- Oligodendrocytes
- Schwann cells
Type of glial cells that has numerous functions
Astrocytes
Type of glial cells that line cavities
Ependymal cells
Type of glial cells that are phagocytes
Microglia
Type of glial cells that form myelin
Oligodendrocytes
Type of glial cells that is located in the PNS and responsible in forming myelin
Schwann cells
Type of glial cells that is involved in:
- development of neural connections and blood-brain barrier
- modulate synaptic activity (wrapped around synapses)
- remove neurotransmitter from synaptic cleft (glutamate and biogenic amine)
- communicate to neurons through chemical messengers
- maintain normal electrolyte composition of ISF in CNS
- protect neurons against toxic substances
Astrocytes
- protect CNS from foreign matter and oxidative stress
- phagocytosis and release of cytokines
- involved in immune response
Microglia
(3) Physical support of the CNS
- Bone
- Meninges
- Cerebrospinal fluid
- The outermost structure that protect the soft tissues of CNS (i.e cranium or skull)
- Vertebral column that surrounds the spinal cord
Bone
- Connective tissue membranes that separate the soft tissue (brain) from the surrounding bones
- 3 layers (dura, arachnoid and pia mater)
Meninges
(Meninges) outermost layer, very tough, fibrous tissue
Dura mater
(Meninges) web-like structure, no space between this and dura mater
Arachnoid mater
(Meninges) the innermost layer, immediately adjacent to the nervous tissue called subarachnoid space
Pia mater
Serves as the cushion for the brain
Cerebrospinal Fluid
The brain contains how many cavities
4 cavities (=ventricles filled with CSF)
ventricles connected to a midline third ventricle by interventricular foramen
2 C-shaped lateral ventricles
This connects the third ventricle to the fourth ventricle which is continuous with the central canal
Cerebral aqueduct
The lining of the ventricles and central canal is composed of this type of glial cells
Ependymal cells
The lining of the ventricles is vascularized (very small vessels) and forms a tissue called
choroid plexus
- Extracellular fluid of the CNS
- recycled 3 times/day
- secreted by ependymal cells of the choroid plexus
- circulates to subarachnoid space and ventricles
- reabsorbed by arachnoid villi
Cerebrospinal Fluid (CSF)
What’s causing the limited exchange between CSF and blood?
The blood-brain barrier
4 Functions of the Cerebrospinal Fluid (CSF)
- Cushions brain (absorbs shock)
- Maintains stable interstitial fluid environment
- Exchange of material and fluids between cells (low K+, high Na+ outside the cells, few proteins)
- Limited exchange between CSF and blood due to blood-brain barrier
CNS comprises how many % of body weight?
2%
CNS receives how many % of blood that the heart pumps?
15%
Brain uses __% of O2 consumed by body at rest.
20%
Brain uses __% of glucose consumed by body at rest.
50%
True or False. Cells in the CNS have very high glycogen.
False. CNS have very little glycogen.
A highly selective network of specialized capillaries that prevent many substances from entering the brain from the blood
Blood-Brain Barrier (BBB)
What is the BBB and its function?
A highly selective network of specialized capillaries that prevent many substances from entering the brain from the blood
Site of exchange between blood and interstitial fluid
Capillaries
Layers of capillaries surrounded by these two
- Astrocytes
2. Ependymal cells
Protect the brain from blood borne pathogens, toxins and certain hormones
Ependymal cells
Name 5 materials that CAN cross the BBB
- Lipid soluble
- O2
- CO2
- Alcohol
- Water
Name 4 materials that can only cross the BBB with a transporter
- Glucose
- Amino acids (facilitated diffusion)
- Choline
- Aspirin
Name 3 materials that CANNOT cross BBb
- Catecolamines
- Inorganic ions (H+)
- Antibiotics
Which matter contains cell bodies, dendrites and axon terminal?
Gray matter
Which matter contains myelinated axons also called fibers?
White matter
T or F. White matter > Gray matter?
Yes.
White matter - approx. 60%
Gray matter -approx. 40%
External surface of the brain gray matter
Cerebral cortex
White matter is located _____________
beneath cerebral cortex
Embedded within the layer beneath the cerebral cortex are smaller areas of gray matter.
Nuclei or Subcortical nuclei
Axon (fibers) are organized in bundles called _________.
Tracts
Bundles of axons that connect one region of gray matter with another
Tracts