CNS Organisation Flashcards
What does the CNS include?
the brain and spinal cord
How many pairs of spinal nerves and cranial nerves are there respectively?
- 31 spinal
- 12 cranial
Where is the brain located?
in the cranial cavity protected by the skull and meninges
What is the meninges?
the tough connective tissue that covers and surrounds the brain
What is the brain divided into?
- forebrain
- midbrain
- hindbrain
What does the forebrain include?
the cerebrum and the diencephalon
What does the hindbrain include?
the medulla oblongata, pons and cerebellum
What does the brainstem include?
the midbrain, pons and medulla oblongata
What makes up the vertebral column?
gaps between vertebrae of the spine
How is the CNS different to the PNS?
- the CNS has little to no capacity to regenerate after injury
- the CNS contains myelin that is inhibitory to neuro-regeneration
Where does the spinal cord end?
the tailbone (coccyx)
What is the retina?
essentially an outgrowth of the brain that is part of the CNS
What nerve is the optic nerve?
cranial nerve 2
What are the 31 spinal nerves?
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
What is the largest part of the brain?
the cerebrum
What does the cerebrum consist of?
2 cerebral hemispheres separated by the longitudinal fissure
What is on the surface of the cerebral hemispheres?
a thin 5mm layer of grey matter
What is grey matter?
a collection of neuronal cell bodies called the cerebral cortex
What are gyri?
the folds and bumps in the brain
What are sulci?
the grooves of the brain
What does the central sulcus form?
the boundary between the frontal and parietal lobes on the lateral and medial surfaces of the cerebral hemispheres
Where is the occipital lobe?
the very back of the brain
What is somatosensation?
sensation from the body surface e.g. pain, temperature, pressure, proprioception
What is proprioception?
position sense i.e. knowing where your body parts are without looking
What is required for sensation to reach consciousness?
the primary somatosensory cortex
What are the ascending and descending tracts respectively?
- ascending = sensory signals
- descending = motor signals
What is responsible for initiating all voluntary movement?
the primary motor cortex in the frontal lobe
What are the 4 lobes of the brain and where are they?
- frontal lobe - anterior to central sulcus and superior to lateral fissure
- parietal lobe - posterior to central sulcus and superior to lateral fissure
- temporal lobe - inferior to lateral fissure
- occipital lobe - posterior to parietal and temporal lobes
Where is the hippocampus?
rolled in part of the cerebral cortex
What is the hippocampus essential for?
the formation of new memories
What is the most vulnerable part of the brain?
the hippocampus, especially during global ischaemia and early stages of Alzheimer’s
What does the hippocampus contain?
neurons and glial cells
What does a neuron consist of?
a cell body, axon and dendrite
What is the most common excitatory and inhibitory neurotransmitter respectively?
- excitatory = glutamate
- inhibitory = GABA
What do glutamate and GABA receptors do respectively?
- glutamate opens sodium channels and excites the postsynaptic neuron
- GABA opens chloride channels and inhibits the postsynaptic neuron
Where do glutamate and GABA synapse respectively?
- glutamate = spines of neurons
- GABA = shafts of dendrites
What are the most common neurotransmitters in the PNS?
ACh and noradrenaline
Where are dopamine and ACh important respectively?
- dopamine = Parkinson’s disease
- ACh = Alzheimer’s disease
Where does the longest axon travel?
from the toe to the brain
What do APs cause?
the release of a neurotransmitter from the axon terminal which then diffuses rapidly across the synaptic cleft and binds to the receptors on the dendrite of the next neuron
What do glial cells do?
support the function of neurons
Give examples of glial cells
- astrocytes
- oligodendrites
- microglia (macrophages)
Give examples of neuronal membrane proteins
- Na+/K+ ATPase
- glucose transporter
Give examples of glial membrane proteins
glutamate transporter
Where is white matter found?
in the deeper tissues of the brain containing axons covered in lipid material myelin
What is the largest white structure of the brain?
the corpus callosum
What is the internal capsule?
a white matter structure where a large number of motor and sensory fibres travel to and from the cortex
What are nuclei?
collections of neuronal cell bodies in the CNS
Where is the diencephalon and what does it consist of?
between the two hemispheres and consists of the dorsal thalamus and the hypothalamus which are separated by the hypothalamic sulcus
What is the last relay station before the signal is sent to the cerebral cortex?
the thalamus
What is the diencephalon important for?
the regulation of movement and relay of sensory information
What is homeostasis?
the maintenance of the internal balance of the body e.g. osmolarity/temperature/hormone levels of the blood
What does the hypothalamus do?
- influence the pituitary gland
- control the secretion of hormones
- alter homeostasis by direct neuronal projection
What does the ANS control?
the internal organs of the body
What is the thalamus?
a large mass of grey matter (nuclei) on either side of the third ventricle
What is the third ventricle?
a narrow funnel-shaped structure in the centre of the brain
What does the hypothalamus form?
the lower part of the lateral wall and floor of the third ventricle
What does the midbrain connect?
the forebrain to the hindbrain
What are the muscles of the eye controlled by the cranial nerves?
the ciliary body and iris
Which brain structures have ascending and descending tracts?
- midbrain
- forebrain
- pons
- medulla oblongata
What are the cranial nerves of the midbrain?
III and IV
What are the nuclei of the midbrain associated with?
cranial nerves III, IV and V and visual and auditory pathways
Where is the pons?
inferior to the midbrain and superior to the medulla oblongata
What are the cranial nerves of the pons?
V, VI, VII and VIII
What is the most inferior portion of the brain?
medulla oblongata
What are the cranial nerves of the medulla oblongata?
IX, X, XI and XII
What are the nuclei of the medulla oblongata associated with?
cranial nerves V, IX, X, XI, XII and cardiovascular and respiratory function
Where is the cerebellum located?
posterior to the pons and the medulla oblongata
What is the cerebellum involved in?
the regulation of balance and coordinated movement
What does the cerebellum consist of?
a midline portion (vermis) and 2 hemispheres connected to the brainstem
Where is the spinal cord continuous with the brain?
at the foramen magnum of the skull which tapers off into the conus medullaris
Why is there difference in length between the spinal cord and the vertebral column?
due to the differential growth of the spinal cord
What does a cross section of the spinal cord contain?
- spinal nerves
- grey matter
- fibre tracts
