Lecture 1: Revision of brain, spinal cord and meninges Flashcards
The CNS is the
integrating and command centre
integrating sensory information, command referring to motor output
The PNS is the
communication system linking all parts of the body to the CNS, via nerves
CNS=
brain and spinal cord
PNS =
Peripheral and cranial nerves (cranial nerves are a type of peripheral nerves)
Brain major divisions
Forebrain
Brainstem
Cerebellum
Spinal cord major divisions
None - just spinal cord
Forebrain
Cerebral hemispheres (left and right) - cerebrum is the name that collectively names the hemispheres Diencephalon
Brainstem
Midbrain
Pons
Medulla
(pons + medulla = hindbrain)
Hindbrain
part of the brain stem
pons+medulla = hindbrain
Cerebellum
part of the brain subdivision of the CNS
Brain weighs approx
1.5 kgs
Cerebrum is ____% of brain volume
83%
Cerebellum contains ____% of neurons
50%
What is posterior and inferior to the cerebrum?
cerebellum
Superior also called
dorsal
anterior also called
rostral
posterior also called
caudal
inferior also called
ventral
Midsagittal cut =
through the midline
Nerve tissue contains two basic cell types …
1 - neurons (nerve cells)
2 - support cells (glial cells)
Neurons (nerve cells)
highly specialized, excitable cells
have high metabolic rate
provide rapid (within milliseconds) and specific communication between regions of the body
Support cells (glial cells)
- 4 types
- structural support
- regional metabolism - insulation
What are the 4 types of glial cells?
astrocytes, oligodendrocytes, microglia, ependymal cells
Astrocytes function
support structurally, regional metabolism
Oligodendrocytes function
insulation in the CNS
Microglia function
Immune cells
Ependymal cell function
Line ventricles, move cerebrospinal fluid
Grey matter
(Neuron cell bodies)
Nucleus (CNS)
Ganglion (PNS)
White matter
(Axons)
Lipid material in myelin sheaths gives white appearance
Ganglion is a
collection of neuron cell bodies in the PNS
e.g. the dorsal root ganglion
Grey and white matter location in the brain
Sitting on the outside and also some on the inside and between the two is the white matter
Grey and white matter location in the spinal cord
Spinal cord has grey matter on the inside and white matter on the outside
Why is there grey matter on the outside of the cerebrum?
On outside in cerebrum but not spinal cord because cerebrum is folded to give extra surface area which means that we can put more nerve cells on the edge that has been folded and we need more nerve cells put there because of our capacity to think, move and speak
Dura mater is
the first later of the meninges that you see when you take the skull away
Gyri
Hill tops
Sulci
valleys
Fissure
separates large regions of the brain
deep sulcus
cortex of the brain is
grey matter
Main lobes of the brain
Frontal lobe, temporal lobe, parietal lobe, occipital lobe and the cerebellum
Insula location
- is buried deep within the lateral sulcus & forms part of its floor
- is covered by portions of the temporal, parietal & frontal lobes
Central sulcus
Separates the frontal lobe from the parietal lobe
Lateral sulcus
separates the frontal and parietal lobes from the temporal lobe.
Transverse fissure
separates the cerebrum from the cerebellum
What sulci can you see from superior surface?
central sulcus
What sulci can you see from lateral surface?
transverse fissure
central sulcus
lateral sulcus
What sulci can you see from the medial surface?
Parieto-occipital sulcus
Transverse fissure
Parieto-occipital sulcus
separates the parietal and occipital lobes
Note about the pituitary gland
pituitary gland, inferiorly part of the diencephalon
Spinal cord extends from …. and ends where
Extends from the foramen magnum (base of the skull) to first or second lumbar vertebra
Width and length of spinal cord
About the width of your thumb, approximately 42 cm long
how many pairs of spinal nerves are there?
31 pairs
What does the spinal cord provide?
provides two-way street of information to (afferent/sensory) and from (efferent/motor) the brain
How many enlargements are there on the spinal cord?
two - cervical enlargement and the lumbar enlargement
Enlargements of the spinal cord
where the nerves serving the upper and lower limbs arise , enlarged to house these neurons
more neurons particularly motor neurons for limb movement
Conus medullaris (medullary cone)
The tapered, lower end of the spinal cord. It occurs near lumbar vertebral levels 1 (L1) and 2 (L2), occasionally lower. … After the spinal cord tapers out, the spinal nerves continue to branch out diagonally, forming the cauda equina.
Filum terminale (terminal Filum)
- extends from the conus medullaris to the posterior surface of the coccyx
anchors the spinal cord
The filum terminale is continuous with the pia mater
Cauda equina (pony tail)
- the collection of nerve roots at the inferior end of the vertebral canal
Why?
• After birth the vertebral column grows faster than spinal cord. Nerves have to grow down in order to innervate more inferior structures
Cross section of spinal cord
Grey matter is centrally located, white matter is peripherally located
posterior media sulcus
anterior median fissure - bigger space anteriorly due to blood vessels therefore it is a tissue
dorsal roots = afferent fibres connect to dorsal root fanglion, send sensory impulses to the cord
ventral root = efferent fibres, axons to effector organs
spinal nerve = mixed fibres
Spinal cord injuries
Paralysis - loss of motor function
Paresthesias - sensory loss
•~260 new spinal cord injuries each year in NZ
• 80% SCI are males aged 15-35 years
Paralysis
loss of motor function
Paresthesias
sensory loss
The severity of spinal cord injury depends on
what level the injury occurs at
C1-C4 spinal cord damage
high tetraplegia - cannot move upper and lower limbs
C5-C8 spinal cord damage
low tetraplegia - some movement in upper limbs, no movement in lower limbs
Thoracic, lumbar or sacral injuries
paraplegia = no movement in lower limbs, still movement in the upper limbs
SPinal cord injuries can either be
complete or incomplete
ventral horn damage on spinal cord on the left side causes
motor (paralysis) on the right side of the body
dorsal horn damage on spinal cord on the right side causes
sensory loss on left side
Meninges
Protection of the brain and spinal cord
Membranes that are associated with the brain
prevents the sort tissue of brain damaging itself on the skull which is a hard tissue
3 layers
- dura mater (external)
- arachnoid mater (intermediate)
- pia mater (internal)
• Large subarachnoid space, within which is
cerebrospinal fluid (CSF)
• Form the partitions within the skull (dura)
dura mater
tough mother
• Thick layer of connective tissue surrounding the brain
• Very Tough ( hard to stretch, collagen within it so it has tensile strength)
- providing main
support and protection
Two layers of the dura mater
periosteal layer and meningeal layer
2 layers of dura mater separate and form large dural venous sinuses (between the two layers) e.g. the superior sagittal sinus
Meningeal layer folds
• extends inward to form flat partitions e.g. falx cerebri
- subdivide the cranial cavity
- limit excessive movement of the brain
within the cranium
Falx cerebri seperates….
forms a partition between the two cerebral hemispheres
Tentorium cerebelli seperates…
forms a partition between the cerebellum and cerebrum
Falx cerebelli seperates…
forms a partition between two cerebellar hemispheres
Falx cerebri
sickle shaped
- Lies in median sagittal plane (in longitudinal fissure)
- Partially separates cerebral hemispheres
Attachments of flax cerebri anteriorly and posteriorly
attaches to crista galli, anteriorly
attaches to upper surface of tentorium cerebelli in the midline, posteriorly
Tentorium cerebelli
- more horizontal plane
* separates cerebrum from cerebellum
Falx cerebelli
- Smaller dural fold runs along the vermis (midline of cerebellum) of the cerebellum
- Separates two cerebellar hemispheres
Subdural space
- The space between meningeal dura mater & arachnoid mater
- Very narrow, contains a film of fluid
• May be enlarged by bleeding
(= subdural haemorrhage)
