Lecture 1 - ORGANISATION OF NERVOUS SYSTEM Flashcards
Sponges, jellyfish
nerve net which gives the ability to react to external stimuli
invertebrates cord?
dorsal
vertebrates cord?
ventral
Brain divisions common to all vertebrates
olfactory bulb, cerebral hemispheres, cerebellum, optic tectum, medulla oblongata
Mammals brains
neocortex which is multi-layered, specialised structure not found in the likes of reptiles, shows a development of processing power which changes as you move higher up the animal
forebrain
telencephalon
- cortex
- olfactory bulb
Diencephalon
- thalamus
- hypothalamus
- prosencephalon of forebrain
- telencephalic vesicles
- diencephalon
- optic vesicles
midbrain
brainstem
mesencephalon
- tectum
- tegmentum
hindbrain
brainstem
rhombencephalon
- pons
- medulla
spinal cord
spinal cord
Neural tube
- endoderm – linings of organs; viscera
- mesoderm – bones and muscles
- ectoderm – nervous system and skin
Neural plates
folds and fuses to form the neural tube
- CNA develops walls of the tube
- PNS derives from the neural chest
Spina Bifilda
- Failure of the posterior neural tube to close
- Foetus wont develop a brain
- anterior end doesn’t close, then the spinal cord will stick out of the column – anterior makes up the peripheral end and starts to swell
- Supplementing diet with folic acid in early pregnancy can reduce neural tube defect incidence by 90%
- Some anti-epilepsy/ bipolar drugs interfere with folate metabolism and increase risk of SB
Development differentiation
- Three swellings at the rostral end of the neural tube becomes primary vesicles
- Three primary vesicles: fore, mid, hind brain
Ventricles
- hollow and bathed in CSF
- four fluid filled cavities called ventricles
- Act to cushion brain and have a role maintaining chemical stability and removing waste products
- brain shock absorber
The Spinal Cord:
- protected by spinal column, surrounded by meninges (membranes and connective tissues) and CSF
- primary channel for messages from skin joints and muscles to/from the brain
- dorsal roots (closest to the skin at the back) of spinal cord contain sensory, afferent neurons
- ventral roots contain motor, efferent neurons (signals to the rest of the body)
- grey matter = neuron cell bodies
- white matter = myelinated axons
root route
dorsal root —-> sensory —-> spinal cord —-> motor —->ventral root
The Brainstem
- oldest part of the brain
1. midbrain – movement, sensory, input eyes and ears
2. pons – switchboard connects the cerebellum to the cerebral cortex which swells out from the ventral surface of the brain stem and is important relay between cortex and cerebellum (controls blood pressure and if damaged can result in major life threatening problems)
3. medulla – autonomic functions and is important in control of blood pressure and respiration
4. cerebellum
Brain stem damage
- hydrocephalus (the accumulation of fluid) or haemorrhage
- severe cases can lead to coning which is damage to the medulla causes respiratory arrest
Cerebellum
- movement control centre
- extensive connections to cerebrum and spinal cord
- You can live without a cerebellum
Diencephalon and Mesencephalon
- Midbrain: linkages between components of motor systems (e.g. substantia nigra) and eye movements
Diencephalon: thalamus (relay and gating roles) and hypothalamus (homeostasis and reproduction
Cerebral Cortex
mammals have 6-layer neocortex
- 2 halves along a sagittal fissure
- Controls:
1. Voluntary actions
2. Cognition
3. Perception/ awareness
Cortical folding
- Increase intelligence to increase processing power
- Cortical neurons represent processing power which increase number of cortical neurons
- keeps skull volume and mass to minimum
- big hards are harder to protect
Homunculus
- shows how much neocortex is linked to a function
- proportional to neuronal composition
- important for finger and jaw movement
SUMMARY
- there are major similarities and differences exist between the major brain regions in animals
- development and function of all the major regions of the spine and human brain all derive from the neural tube
