IC1- CNS Flashcards
What does the forebrain consist of?
- Cerebrum
- Diencephalon (thalamus and hypothalamus)
What does the hindbrain consist of?
- Medulla oblongata
- Pons
- Cerebellum
What does the brainstem include?
- Midbrain
- Pons
- Medulla oblongata
Midbrain- cranial nerves, nuclei associated with, and fiber tracts?
Cranial nerves
- 3, 4
Nuclei associated with
- 3, 4, 5
- Visual and auditory pathways
Fiber tracts
- Ascending and descending fibers
Hindbrain- cranial nerves, nuclei associated with, and fiber tracts?
Cranial nerves
- 5, 6, 7, 8
Nuclei associated with
- 5, 6, 7, 8
Fiber tracts
- Ascending and descending fibers
What do the fast and slow component of the axon transport?
State how fast/ slow in (mm/day)
- Fast component (50 - 400mm/day) transports the
cytoplasmic proteins and macromolecules that are
required for metabolic and synaptic activity - The slow component (1 - 4mm/day) transports the
cytoskeletal components down the axon
Medulla oblongata- cranial nerves, nuclei associated with, and fiber tracts?
Cranial nerves
- 9, 10, 11, 12
Nuclei associated with
- 5, 9, 10, 11, 12
- Cardiovascular and respiratory function
Fiber tracts
- Ascending and descending fibers
What are the 2 types of cells in the brain? Elaborate on their function.
- Neurons
- Structural and functional
unit of the nervous system
- Generate/ conduct
impulses and are excitable - Non-neuronal cells (glial cells)
- Non-conducting
- Support and protect neurons
- 10x the number of neurons
What cellular components do the axonal cytoplasm lack? (3)
What happens as a result?
- Lack ribosomes, RER and Golgi apparatus
- As the axon terminus lacks components for
synthesizing new proteins or degrading old ones,
materials must be transported back and forth between
the cell body and the terminus
Which normal cell component do dendrites NOT have?
They contain all the cytoplasmic components found in the cell body except the golgi apparatus
What are dendritic spines and their functions?
Little protrusions coming out of dendrites (increased surface area → increase ability of dendrites to receive more information)
Which channel does the presynaptic terminal contain?
Voltage-gated Ca2+ channels
Explain what happens at the excitatory synapse. Include which channel is involved.
Binding of neurotransmitter
to its receptors -> opening of Na+ channels in the
postsynaptic membrane depolarization of the
membrane, action potential in the postsynaptic cell
State the process of what happens upon arrival of an action potential at axon terminal. State which channel is involved.
- Arrival of an action potential at an axon terminal → opening of Ca2+ channels → influx of Ca2+ ions → rise in the cytosolic Ca2+ level
- Triggers exocytosis of the neurotransmitter into the synaptic cleft
Explain what happens at the inihibitory synapse. Include the channel(s) involved.
Neurotransmitter binding → opening of K+ or Cl- channels in the postsynaptic membrane → hyperpolarization of the membrane → no action potential in the postsynaptic neuron
List the 3 types of glial cells in the CNS (list from the most numerous to the least numerous one)
- Oligodendrocytes (60-80%)
- Astrocytes (25%)
- Microglia (5-10%)
State the important functions of oligodendrocytes (1), astrocytes (2) and microglia (2).
The rest just read through
Oligodendrocytes:
- *Myelin sheath formation
Astrocytes:
- *BBB
- *Structural support, scar formation
- Secretion of nerve growth factors
- Water transport
- Excess transport – cerebral edema
Microglia:
- *Brain macrophages
- *Immunocompetent cells of CNS
- Phagocytosis
- Secretion of proinflammatory cytokines (TNF-α and IL1β), chemokines
What is the difference between fibrous and protoplasmic astrocytes?
Fibrous astrocytes:
- Located primarily in the
white matter; long,
spindly processes with
few branches
Protoplasmic astrocytes:
- Located in the gray
matter; thick, lightly
branched processes;
closely apposed to
neuron cell bodies
What are the functions of astrocytes? (4)
- Regulate the composition of the intercellular environment and the entry of substances into it
- Provide structural support to neurons and specifically to synapses
- Metabolize neurotransmitters [e.g. glutamate glutamine
shuttle] - Mediate the exchange of nutrients and metabolites
between the blood and neurons
What different functions do oligodendrocytes have in the white vs grey matter?
White matter:
- Predominant type of neuroglial cell and produce the myelin sheath around myelinated fibers in the white matter
Grey matter:
- Closely associated with
neuron cell bodies,
functioning as satellite
cells
What is the cell marker for oligodendrocytes?
CNPase
What is the name of the cell that forms myelin sheath around neurons in PNS?
Schwann cells
Oligodendroyctes express Nogo-A (myelin-associated neurite outgrowth inhibitor). What is its function?
Inhibition of axonal regeneration following injury and ischemia in the CNS
What are the biomarkers for microglia? (2)
Lectin, OX42 (complement type 3 receptor)
What are some examples of diseases are microglia are implicated in (3)?
Alzheimer’s disease, Parkinson disease, cerebral ischemia (stroke)
What are the 3 connective tissue elements of the peripheral nerve structure?
- Epineurium (outermost) (surrounds entire nerve)
- Perineurium (surrounds each fascicle)
- Endoneurium (innermost) (surrounds each individual nerve fiber, contains Schwann cells)
What do you call a bundle of nerve fibres/ axons in the peripheral nerve structure?
Fascicle
What is the difference in the way the oligodendrocytes and Schwann cells myelinate axons?
In the CNS, individual oligodendrocytes myelinate portions of several axons
In the PNS, individual Schwann cells myelinate portions of only a single axon.
What are the 2 pairs of arteries that supply blood to the brain?
- Left and right internal
carotid arteries - Left and right vertebral
arteries
The 2 vertebral arteries join to form which single artery?
Basilar artery
Where does the vertebral artery originate from?
Subclavian artery
Where does the internal carotid artery originate from?
Common carotid artery in the neck
Which artery supplies most of the lateral surface of the hemisphere?
Middle cerebral artery
What is an advantage of the Circle of Willis?
What does it NOT work for?
May help to supply blood
to the opposite side, in
cases of SLOW occlusion of
an artery on one side (the
communicating arteries
have time to enlarge, to
accommodate the
increased blood flow)
Does NOT work for SUDDEN occlusion
What does the Circle of Willis connect?
An anastomotic
ring is formed between
the vertebral and
internal carotid arteries
Where do haemorrhagic strokes frequently occur?
Circle of Willis is a
frequent site for
aneurysms (hence haemorrhagic strokes)
Where does blood from the brain drain into? Where does it empty into?
Blood from the brain drains into the venous sinuses → internal jugular vein
Where does blood from the superficial aspect of the brain drain into?
Outline the path where the blood from the inferior part of the brain drains into?
- The superior sagittal sinus
- Blood from inferior part of brain → sinus and superficial middle cerebral vein → cavernous sinus
The cavernous sinus are closely related to which cranial nerves and blood vessels?
- Cranial nerves 3, 4, 5, 6
- A part of the internal carotid artery
Outline the pathway the blood from the centre of the brain drains to?
Blood from centre of brain → deep cerebral veins → venous sinus
Outline the path of blood flow from the superficial and deep parts of the brain to the heart
Blood from the superficial and deep parts of the brain→ venous sinus → internal jugular vein → heart
Outline the path of blood flow from the superior sagittal and straight sinuses to the internal jugular vein
Blood from the superior sagittal and straight sinuses → transverse sinus → sigmoid sinus → internal jugular vein
Explain what is a subdural haemorrhage.
What are the SSx and why do they take time to manifest?
Subdural haemorrhage happens when the rupture of a cerebral vein occurs between one of the superior cerebral veins as it drains into the superior sagittal sinus.
- Venous pressure is low, seepage is slow
- Weeks later, hematoma slowly expands and presses on brain → dizziness, headaches, apathy, falling, confusion, and drowsiness
Outline the pathway of CSF flow?
- It flows from the lateral ventricle to 3rd ventricle, and via the cerebral aqueduct to the 4th ventricle
- It then flows out of the 4th ventricle to bathe the whole brain and spinal cord
How is the CSF absorbed?
Into the superior sagittal sinus by arachnoid granulations
