Neuroanatomy Flashcards
What makes up the cytoskeleton?
Microfilaments, neurofilaments, microtubules and proteins
Properties of microfilaments
- 3-7nm in diameter
- Mostly polymer of actin
- Formed by 2 strands
- Found at the edge of the cell (cell cortex)
- Provides strength and shape, synaptic specialisation and learning and memory
Properties of neurofilaments
- 7-11nm in diameter
- Protein composition varies
- Provides up to 85% of total protein in the neurone
- Largest population in motoneurons
- Stabilises and strengthens axons, organises structure, can cause ALS when things go wrong
- Also known as intermediate filaments
Properties of microtubules
- 20-28nm in diameter
- Polymer of tubulin molecules
- Longitudinal arrangement in axons/dendrites
- Shape altered by polymerization
- They have microtubule-associated proteins (MAPs)
- Provide cell movement and axonal transport
How fast can axonal transport be?
100-400mm/day or 1mm/day
Orthograde vs retrograde axonal transport
Orthograde is from cell body to axonal terminal. Retrograde is from axonal terminal to cell body
Name the 2 molecular motors
Kinesin and dynein
What are the properties of kinesin?
- Orthograde transport
- Has amino terminal for ATP activity
- Divergent tail for movement
- Hydrolyses ATP to carry molecule along microtubules
What is dynein?
The same as kinesin but is used for retrograde transport
Name the glial cells in the CNS
Astrocytes, oligodendrocytes, microglia and ependymal
Name the glial cells in the PNS
Schwann cells and satellite cells
Properties of astrocytes
- Guide neurones during development
- Support neurones and capillaries
- Buffer extracellular ions
- Store and release neurotransmitters
- Allow glia-glia and glia-neurone communication
- Help the formation of the blood-brain barrier (BBB)
What is the blood-brain barrier (BBB)?
Maintains a stable chemical environment and immunological privilege of CNS
Properties of microglia
- Role in CNS immune response to infection or tissue damage
- Increases in numbers
- Releases growth factors
What do ependymal cells do?
Line the ventricles and central canal of spinal cord to help produce and control flow of Cerebrospinal Fluid (CSF)
Properties of oligodendrocytes
Myelination (insulation) of axons
What is the oligodendrocytes equivalent for PNS?
Schwann cells
What is multiple sclerosis?
An autoimmune disease which causes the destruction of myelin in the CNS
What are the symptoms of multiple sclerosis?
Fatigue, numbness, blurred vision and blindness
What is the PNS equivalent of multiple sclerosis?
Guillain Barre syndrome
What are the different sections of the spinal cord?
Dorsal (back), ventral (front), lateral (outside), medial (inside), dorsal horn (back right or left), ventral horn (front right or left) and the intermediolateral horn (middle)
How many different lamina are there?
10
What is Lamina I?
Marginal zone
What is Lamina II?
Substantia gelatinosa
What are Laminae III, IV, V and VI?
Nucleus proprius
What is Lamina VII?
Lateral horn (soma of sympathetic preganglionic neurones)
What is Lamina IX?
Somatic motoneuronal pools
What is the sensor for the spinal cord?
Dorsal root which contains the dorsal root ganglion (DRG)
What is the effector for the spinal cord?
Ventral root
What is in the somatomotor pathway?
Sensory (afferent) fibres from skin and motor (efferent) fibres
What are the processes for sensory fibres?
Cell bodies in dorsal root ganglia, enter SC via dorsal roots and terminate in grey matter of dorsal horn
What are the processes for motor fibres?
Cell body in grey matter of lateral horn, exit via ventral root, terminate in skeletal muscle
What is in the visceromotor pathway?
Sensory fibres from internal organs and motor fibres
How are spinal nerves formed?
Dorsal and ventral roots merge
Head end of the spinal cord
Rostral
Tail end of the spinal cord
Caudal
Endoneurium
Connective tissue layers around individual axons
Perineurium
Encloses bundle of axons
Epineurium
Dense tissue layer enclosing several bundles
What are the 4 interconnecting ventricles?
- Interventricular foramina (lateral to third)
- Cerebral aqueduct (third to fourth)
- 2 lateral apertures and a medial aperture (fourth to subarachnoid space)
How is the CNS protected?
- Outer casting (skull/spinal vertebral column)
- Membranes (meninges)
- Hydraulic buffer (CSF)
- Foreign agents (BBB)
How do nerves enter and exit the CNS?
Via foramen (foramina) in the skull or between spinal vertebrae
3 substances between the brain and the skull
Dura mater, arachnoid mater and pia mater. Separated by epidural space, subdural space and subarachnoid space
Properties of dura mater
Protective, highly vascularised, innervated and is below epidural space in SC but not in skull
Properties of arachnoid mater
Loose fit, avascular, delicate and is above subarachnoid space which contains CSF and is a shock absorber
Properties of pia mater
Thin layer of connective tissue, clings to CNS, below subarachnoid space and contains small blood vessels to supply oxygen and nutrients to CNS
What is Cerebrospinal fluid (CSF)?
- Produced by choroid plexuses (capillary networks) in ventricles
- Capillaries filter blood plasma then secrete CSF to form blood-CSF barrier
- Made of glucose and various ions
Function of CSF
- Inside and surrounding CNS
- Protects CNS
- Gives brain buoyancy
- Provides nutrients and removes waste
Arachnoid villi
Act as one way valves for projections of arachnoid mater through the dura mater
Venous sinuses
Valveless channels supplied by brains venous system (stores arachnoid mater)
What is hydrocephalus?
- Overproduction of CSF
- Blocks flow between ventricles
- Obstructs drainage into circulatory system
- Causes increased pressure in CNS
- Can cause permanent damage
How can you treat hydrocephalus?
Inserting shunts to drain fluid
