structure and function of CNS

Question 1

directions of brain

Answer 1

rostral- front of brain
caudal- back of brain
dorsal- posterior and inferior of brain stem and spinal cord
ventral- anterior and inferior of brainstem and spinal cord

Question 2

basic neuron types

Answer 2

bipolar- interneuron
unipolar-sensory neuron
multipolar- motorneuron
multipolar- pyrimidal cell

Question 3

grey vs white matter

Answer 3

grey-more cell bodies, dendrites, axon termini, glial cells, blood vessels
white- more axons (myelinated), glial cells (oligodendrocytes), blood vessels

Question 4

surface structure

Answer 4

• sulci (grooves)
• geri (ridges)
• both define lobes:
  frontal, parietal, temporal, occipital
  deep:limbic lobe
  brains stem- breathing, heart rate
  cerebellum- balance posture

Question 5

brainstem

Answer 5

superior to inferior order
brain stem
midbrain -> pons-> medulla oblongata
- cerebellum is attached to pons and medulla, followed by the spinal cord

Question 6

cerebral cortex

Answer 6

• different types, multiple connections in different directions

Question 7

deep structures of brain

Answer 7

limbic system- emotions/emotional behaviour (amygdala)
learning and memory (hippocampus)
basal ganglia- control of movement
thalamus- sensory relay centre between spinal cord and cerebral cortex
hypothalamus- temperature regulation (fever PBL)

Question 8

corpus callosum

Answer 8

white matter tracts
communication between brain parts

Question 9

spinal cord

Answer 9

direct extension of brainstem downwards
divided into regions, cervical, thoracic, lumbar, sacral.
gives rise to spinal nerves: exit spinal cord between vertebrae

Question 10

spinal nerves

Answer 10

• each level allows input/output to specific parts of the body
  -sensory, motor and autonomic
  eg C1-C5 = breathing
  L3-S1 = knee and foot movement

Question 11

sympathetic and parasympathetic spinal cord regions

Answer 11

t1-12 = sympathetic tone
cranial nerves and S4 = parasympathetic

Question 12

spinal cord end

Answer 12

conus medullaris- ends at L1-L2
cauda equina- horse tail
filum terminale- stretch down to the periosteum cortex

Question 13

spinal cord tracts

Answer 13

bundles of nerves fibres that run up/down spinal cord (rostalcaudal)
- ascending descending
- autonomic, sensory, motor

Question 14

spinal cord tracts function

Answer 14

• spinothalamic- ascending, sensory, pain and temperature
  -corticospinal- descending, motor, voluntary movement
  ipsilateral- same side
  contralateral- opposite side

Question 15

potential spaces in the meninges

Answer 15

• epidural (extradural) potential space
  (middle) meningeal arteries supply dura: rupture > haematoma
• subdural potential space
  bridging veins connecting to venous sinuses: rupture > haematoma
• subarachnoid space
  CSF, cerebral arteries/veins, arachnoid trabecular (connective)

Question 16

meninges at spinal cord

Answer 16

dura mater- 1 layer only
epidural space contains fat, venous plexus

Question 17

meningitis

Answer 17

• inflammation of Pia mater and arachnoid mater, subarachnoid space
• viral/bacterial infection
• brain damage: cerebral oedema; raised intracranial pressure can cause herniation

Question 18

cerebralspinal fluid

Answer 18

• fills ventricles and subarachnoid space of meninges (brain and spinal cord)
• cushions braided against impact/movement and own weight
• provides stable chemical environment for brain
• nutrient and waste exchange between tissue and blood
• aging: reduced CSF turnover, metabolic waste buildup may contribute to neurodegenerative disease

Question 19

cerebrospinal fluid

Answer 19

• most produced by chord plexus in lateral and 4th ventricles
• resorbed into venous system via arachnoid granulations
• circulation- mainly driven by new productions
• excess CSF/flow obstruction- hydrocephalus
• clear, colourless liquid
• very few cells
  -similar to plasma but much lower protein, different electrolyte levels

Question 20

blood brain barrier

Answer 20

not one structure: several features that prevent harmful substances getting into brain and spinal cord from blood
1) capillaries in nervous tissue
- tight junctions beween endothelial cells restrict movement
- think continuous basement membrane
- astrocytes processes cover vessel
2) ependymocytes cells
- line ventricles and spinal canal- tight junctions restrict movement

Question 21

small areas of blood brain barrier

Answer 21

• some have higher permeability
• sensory functions eg. area postrema (medulla)- toxin detection ->vomiting
• secretory functions eg. pituitary gland (secretes hormones)

Question 22

blood brain barrier permeability

Answer 22

• keeps ut toxins, pathogens etc
• stops fluctuations of ions, nutrients, metabolite concentrations in CNS
• permeable to substances that can diffuse across
• active transport for specific substances eg. glucose
• many drugs cannot cross blood brain barrier