Central Nervous System Flashcards
what is the CNS composed of?
brain and spinal cord
what is the PNS composed of?
nerves (cranial and spinal), and ganglia outside of the brain and spinal cord
what are the three main parts of the brain?
forebrain, midbrain and hindbrain
what is the forebrain composed of?
cerebral hemispheres and diencephalon
what is the hindbrain composed of?
pons, medulla and cerebellum
what does the diencephalon consist of?
thalamus and hypothalamus (underneath the thalamus)
where does the pituitary gland sit?
inferior to the hypothalamus (green)
what are the three parts of the brainstem in descending order?
midbrain, pons, medulla
what does the frontal lobe do?
regulate and initiate
- motor function,
- language,
- cognitive functions (executive function [planning] , attention and memory)
what doe the parietal lobe do?
sensation (touch and pain), sensory aspects of language, spatial orientation and self perception
what doe the temporal lobe do?
process auditory information
what does the occipital lobe do?
processesd visual information
where is the central sulcus?
between frontal and parietal lobes
where is the lateral fissure?
along temporal lobe, separating it from frontal and parietal
where is the parieto occipital sulcus?
runs along edge of occipital lobe separating it from parietal and temporal lobes
what does the limbic lobe contain?
what is it concerned with?
amygdala, hippocampus, mamillary body and cingulate gyrus
learning, memory, emotion, motivation and reward
which lobe lies deep to the lateral fissure?
insular cortex
what is the insular cortex concerned with?
visceral sensations, autonomic control, interoception, auditory processing, visual-vestibular integration
what are the three layers of the meninges?
dura, arachnoid, pia mater
which two layers is the dura composed of?
periosteal (layer of periosteum)
meningeal (durable, dense, fibrous membrane)
where is the cerebrospinal fluid in relation to the meninges?
sub arachnoid space
where is cerebrospinal fluid produced?
modified epithelial cells in choroid plexus of lateral, 3rd and 4th ventricles
where is cerebrospinal fluid located?
ventricles and sub arachnoid space
how many mls of cerebrospinal fluid produced per day?
125ml-500ml
where does CSF exit the ventricular system?
The ventricular system contains three small openings: the two lateral foramina of Luschka and the median foramen of Magendie. Through these openings the cerebrospinal fluid enters the subarachnoid space.
what are the bumps called that you find at the surface of the superior sagittal sinus?
arachnoid villi (granulations)
what do the arachnoid villi do?
reabsorb cerebrospinal fluid
where does the sub arachnoid space become continuous with the superior sagittal sinus?
arachnoid villi
describe the appearance of the arachnoid villi
cauliflower-like projections
how does CSF differ to blood plasma?
lower pH
less glucose
less protein
less potassium
from the spinal cord, does the dorsal root contain afferent or efferent nerves?
does the ventral root contain afferent or efferent nerves?
afferent/sensory
efferent/ motor
name these
- dorsal rootlets
- dorsal root
- dorsal root ganglion
- mixed spinal nerve
- dorsal horn
- grey matter
- ventral horn
- white matter
- ventral rootlets
- ventral root
posterior raymus contains what?
large anterior part - goes to most of muscles and skin
small posterior part - muscles down back of spine and skin of spine
many types of fibres but different in number
what is the spinal cord composed of?
segments which give each rise to a pair of mixed spinal nerves
how many nerves are…
cervical?
thoracic?
lumbar?
sacral?
coccygeal?
8
12
5
5
1
where do the nerves emerge?
intervertebral foramina
how do vertebral levels and spinal levels differ
the further down the spinal cord you get, the lower down the vertebrae get from the spinal cord
how does the relationship between nerves and foramina change between cervical and thoracic regions?
nerves C1-C7 emerge above vertebrae
nerves C8 to Co1 emerge below vertebrae
so above C7 vertebra lies C7 nerve and below it lies C8 - there are 8 nerves but only 7 vertebrae
what are the two spinal cord enlargements?
why are they larger?
C5 cervical enlargement (towards top, innervation of upper limbs)
L2 lumbar enlargement (towards bottom, innervation of lower limbs)
huge amount of innervation going in and out
What is the major pathway for voluntary movement?
corticospinal tract, descending pathway
what is the corticospinal tract composed of?
2 neurons
upper motor neurons in primary motor cortex
and
lower motor neurons in brainstem or spinal cord
when does the upper motor neuron synapse the lower motor neuron in the brainstem and not the spinal cord?
facial muscles, muscles of mastication etc. not limbs
what are the major ascending pathways and what do they do?
dorsal column pathway and spinothalamic tract, detect sensation
which pathway is used for fine touch, vibration and proprioception (position) from skin and joints?
dorsal column pathway
which pathway is for pain, temperature and crude touch?
spinothalamic pathway
what are the ascending and descending tracts of the spinal cord?
The spinal cord has numerous groups of nerve fibers going towards and coming from the brain. These have been collectively called the ascending and descending tracts of the spinal cord, respectively. The tracts are responsible for carrying sensory and motor stimuli to and from the periphery (respectively).
do ascending and descending pathways each occupy one side or both occupy both sides?
both occupy both sides
the descending tracts are motor or sensory?
motor
the ascending tracts are motor or sensory?
sensory
name…
these 2 descending tracts
these 3 ascending tracts
lateral corticospinal tract (motor)
ventral corticospinal tract (motor)
dorsal columns (fine touch, proprioception, vibration)
lateral spinothalamic tract (pain, temperature)
ventral spinothalamic tract (crude touch)
why is the dorsal column called this?
sits at the back of the spinal cord
what is the gyrus sitting in front of the central sulcus called?
the one sitting behind?
pre-central gyrus
post-central gyrus
which gyrus does the primary motor cortex occupy?
Which lobe?
pre-central gyrus
in the frontal lobe
in the strip that runs along the central sulcus, as it is stimulated along the strip, what happens?
different areas of the body move
what is somatotopy?
where a region of the body is represented in the brain
coronal
where does the upper motor neuron axon end?
primary motor cortex
where is the lower motor neuron?
goes through ventral root into spinal cord OR straight to brain stem in case of facial muscles, muscles of mastication etc they have their nucleus in the brainstem. The cell nuclei are in the ventral gray horn of the spinal cord for the other muscles of the body.
Take note that the 85% of lower motor neuron decussate in the medulla
the vast majority of corticospinal tract fibres that come from one hemisphere dessucate (cross) to the other side of the body where? What percentage?
in the medulla
85%
what is the tract called where 85% of the motor neurons cross?
15%?
lateral corticospinal tract
anterior corticospinal tract
where does the lateral corticospinal tract tend to innervate?
limbs
where does the anterior corticospinal tract tend to innervate?
the trunk muscles
what is the crossing over of motor neurons in the medulla called?
decussation
what is another word for brainstem?
bulb
the tract that goes from the cortex to spinal cord and out to the limbs is called what?
corticospinal tract
which tract goes from the cortex to the brainstem and then out to the facial muscles or muscles of mastication?
corticobulbar tract - basically doesn’t go out of the head - cranial nerves
axial/transverse/horizontal
which tract provides information about head movement and position and mediates postural adjustments?
vestibulospinal
which tract mediates the orientation of head and neck during eye movements?
tectospinal
which tract mediates the control of breathing and emotional motor function?
reticulospinal
which tract inneravates lower motor neurons of the upper limb?
rubrospinal
which are the 4 involuntary tracts?
vestibulospinal
tectospinal
reticulospinal
rubrospinal
dorsal (posterior) column pathway mediates what?
fine discriminative touch
pressure
vibration
proprioception
spinothalamic pathway mediates what?
crude touch
pain
temperature
dorsal column: sensory receptor axon goes where?
- dorsal root ganglion
- into spinal cord, then up towards the brain on the same side that it comes in on
the sensory pathway has 3 neurons… where are the cell bodies?
- Has its sensory receptors in the skin and its cell body in the dorsal root
- secondary cell body is either in the spinal cord or the medulla, depending on which pathway
- tertiary cell body is in the thalamus
where in the medulla does the dorsal column pathway ascend?
ipsilateral side of medulla, where it synapses with the secondary cell body
the secondary neuron of the dorsal column pathway crosses over where?
wherever its cell body is, in the dorsal pathway, this will be the medulla
how do fibres enter the dorsal column pathway?
via dorsal horn
information conveyed from lower limbs and body (below T6) travel along which tract and how?
gracile tract, ipsilaterally
information conveyed from upper limbs (above T6) travels along which tract of the dorsal column and how?
cuneate tract, ipsilaterally
first synapse of the gracile tract is where?
gracile nucleus located in medulla oblongata
first synapse of the cuneate tract is located where?
cuneate nucleus in the medulla oblongata
where do second order axons decussate?
what do they form?
where do they synapse?
caudal medulla
contralateral medial lemniscus tract
thalamus
3rd order neurons from the thalamus project to where?
somatosensory cortex posterior to central sulcus located in the post-central gyrus
size of somatosensory areas is proportional to what?
density of sensory receptors in that body region (somatosensory homunculus)
where do pain and sensory sensations ascend?
lateral spinothalamic tract
where do crude touch sensation ascend?
anterior spinothalamic tract
where do the primary spinothalamic sensory neurons terminate and the secondary sensory neurons decussate?
spinal cord
what is the upper motor neuron in the corticospinal tract?
it is in the brain and it projects down and synapses with a lower motor neuron which goes out to a muscle. It may synapse in the brainstem if going to the face or it may synapse in the spinal cord if going to the limbs. 85% of the corticospinal axons still cross in the medulla.
85% of corticospinal axons cross in the medulla, and they tend to innervate
a) limbs
or
b) trunk?
what is the corticospinal tract that crosses known as?
what about the one that doesn’t cross / the smaller one ?
a) limbs
lateral corticospinal tract
anterior corticospinal tract - comes from the hemisphere, stays on the same side descending ipsilaterally to the trunk
the two sensory pathways: dorsal column pathway and spinothalamic pathway have how many neurons?
Where are the receptors and cell bodies of the 1st neuron?
2nd cell body and synapse?
3rd cell body and synapse?
3
both - receptors in skin and cell bodies in dorsal root ganglion but don’t forget in it’s a bipolar neuron. Ascends ipsilaterally through medulla only in dorsal column pathway.
dorsal column - secondary cell body and synapse in medulla, with ALL sensory pathways, the secondary neuron decussates at the synapse
spinothalamic tract - secondary cell body and synapse in spinal cord, with ALL sensory pathways, the secondary neuron decussates at the synapse
both - thalamus
the size of somatotopic areas is proportional to what?
density of sensory receptors in that body region
where do the primary cell bodies lie in all sensory neurons?
dorsal root ganglion
where do the primary spinothalamic neurons synapse their secondary neurons? Where are the secondary neurons’ cell bodies?
Both are in the dorsal horn of the spinal cord
where does the lower motor neuron synapse with the upper motor neuron (corticospinal tract)?
ventral gray horns of spinal cord
