structure and function of the CNS Flashcards
composition of CNS
brain and spinal cord
function of CNS
receives and integrates info from the rest of the body; coordinates activity of body
composition of PNS
cranial and spinal nerves
(optic nerve = part of the brain)
longitudinal axis of the brain
rostral comes out above eyebrows and caudal just above most posterior portion of the head
i.e. not perpendicular
inferior caudal axis
down brainstem
splits the neck/ head into dorsal and ventral
features of grey matter
more cell bodies, dendrites, axon terminals; glial cells (e.g. astrocytes); blood vessels
features of white matter
more axons (myelinated), glial ells (oligodendrocytes); blood vessels
location of limbic lobe/system
deep to cerebrum
function of prefrontal cortex
high level functions, personality
function of primary motor cortex
voluntary movement
what is the central sulcus
midline between the ears
function of primary somatosensory cortex
sensation
location of visual cortex
occipital lobe
function of temporal lobe
hearing (and others)
locations of language/ speech/ hearing
Broca’s area and Wernicke’s area
Broca’s aphasia
can comprehend speech but their speech is impaired (production)
Wernicke’s aphasia
fluent speech but no meaning; impaired speech comprehension
composition of limbic system
amygdala + hippocampus
function of amygdala
emotions and emotional behaviour
function of hippocampus
learning and memory
function of basal ganglia
control of movement
location of basal ganglia
midbrain, coiled structure
function of hypothalamus
temperature regulation + other homeostasis
function of thalamus
sensory relay centre between spinal cord and cerebral cortex
function of white matter tracts
areas of white matter
communication between brain parts
e.g. the corpus collosum
split brain
cut the corpus collosum in people with severe epilepsy to prevent ‘electrical storm’ that would lead to an epileptic fit
can’t verbally describe (L hemisphere) image shown in LVF (sensed in R hemisphere)
regions of the spinal cord
cervical, thoracic, lumbar and sacral
(doesn’t align with vertebral regions)
how do spinal nerves exit the spinal cord
between vertebrae to PNS
spinal nerves C3,4,5
contribute to diaphragm movement and so are essential for breathing
spinal nerves L3-S1
knee and foot movement
how are vertebrae names
after the spinal nerves that are emerging from them, not where the areas are
which spinal nerves are sympathetic tone
T1-12
spinal cord tracts definition
bundles of nerve fibres that run up and down the spinal cord (rostral/ caudal)
- ascending/ descending
- automatic, sensory, motor
what is the spinothalamic tract
ascending, sensory
pain and temperature
what is the corticospinal tract
descending, motor
voluntary movement
decussate
cross over
ipsilateral
same side
contralateral
opposite side
meninges composition
dura mater (‘hard/tough’)
arachnoid mater (‘spider’)
pia mater (‘gentle’)
dura mater structure
fibrous CT
has 2 layers (they separate to form venous sinuses)
arachnoid mater structure
membrane
pia mater structure
membrane
epidural (extradural) POTENTIAL space
not present in all people (in healthy people with no pathology, no space)
(middle) meningeal arteries supply dura; rupture -> haematoma
subdural POTENTIAL space
not present in all people (in healthy people with no pathology, no space)
bridging veins connecting to venous sinuses; rupture -> haematoma
subarachnoid space
relatively large
CSF
cerebral arteries/ veins
arachnoid trabeculae (connective)
differences between meninges in brain and in spinal cord
dura mater has only 1 layer
epidural space contains fat, venous plexus
meningitis general info
inflammation of pia mater + arachnoid mater
- subarachnoid space
viral or bacterial
brain damage
- cerebral oedema
- raised intracranial pressure can cause herniation (movement of brain tissue due to pressure/ inflammation)
lumbar puncture
sample of CSF
insert needle between the L4+5 vertebrae (spinal cord not intact at this level) - pre-spinal nerves
not puncturing the cord
looking for: increased WBCs in CSF (+/- bacteria)
what is the ventricular system
a series of spaces in the brain, subarachnoid space and meninges (both in the brain and spinal cord_; full of CSF
allows flow of CSF
CSF function
cushions brain against impact/ movement and own weight (floating)
provides stable chemical environment for brain
nutrient and waste exchange between nervous tissue and blood
effect of aging on CSF
reduced CSF turnover, metabolic waste build-up may contribute to neurodegenerative diseases
CSF synthesis
most produced by choroid plexus in lateral and 4th ventricles
reabsorption of CSF
into venous system via arachnoid granulations
what is circulation of CSF driven by
mainly new production
what is hydrocephalus
excess CSF/ flow obstruction
CSF composition
clear, colourless liquid
similar to plasma but much lower protein; different electrolyte levels
very few cells
CSF levels of ions are optomise3d for transmission of impulses across an axon
what is the blood brain barrier
not one structure - series of features that prevent harmful substances getting into brain and spinal cord from blood
how do capillaries in nervous tissue contribute to the blood brain barrier
tight junctions between endothelial cells restrict movement
thick continuous BM
astrocyte’s processes cover vessel (blocks diffusion)
how do ependymocyte cells line ventricles and spinal cord
tight junctions restrict movement
what areas of BBB have higher permeability (CVOs)
sensory functions e.g. area postrema (medulla) - toxin detection immediately causes the vomiting reflex
secretory functions e.g. pituitary gland (secretes hormones)
function of BBB
keeps out toxins, pathogens, etc..
stops fluctuation of ions, nutrient, metabolite concentrations in CNS (e.g. increased K+ levels would affect nerve impulse)
permeable to substances that can diffuse across (water, small lipophilic molecules, gases)
active transport for specific substances e.g. glucose, amino acids
many drugs cannot cross BBB
