martin chapter 2 Flashcards
what is the decussation of a pathway?
nerve fibers from one side of the CNS cross over with nerve fibers from the opposite side, allowing signals from one side of the body to be processed by the other side of the brain
limb position sense
our ability to detect the position and the orientation of our limbs without lookin at them
principal pathway for touch and limb position sense is
dorsal column-medial lemniscal system
key pathway for voluntary movements is
corticospinal tract
dorsal column-medial lemniscal system is ascending or descending pathway?
ascending, from the periphery to the brain stem (lower CNS) and the thalamus and the cortex (higher CNS)
corticospinal tract is ascending or descending pathway?
descending, from the cortex to the spinal cord
what is a relay nucleus?
it process incoming signals and transmit the infos to the next component of the circuit
what is the name of the white matter underlying the cortex?
internal capsule
the pyramid
is in the medulla and is formed by the corticospinal axons
each sensory system has multiple cortical areas
a primary cortical area which processes basic sensory info and higher order ones that participate in the elaboration of sensory processing leading to perception
what we mean by saying basal forebrain
the base of the cerebral hemispheres
diffused projecting systems
systems with more widespread projections
the cell bodies are located in the diencephalon, brain stem and basal forebrain. they are either located in nuclei or sparse.
these systems usually result in more generalized functions
where are dopaminergic neurons mostly located?
in the midbrain: in the substantial nigra and in the ventral tegmental area.
also the hypothalamus contains dopaminergic neurons
what is the name of the brain stem nucleus with the most widespread projections of noradrenergic neurons?
the locus ceruleus
neurons of the raphe nuclei use which neurotransmitter?
serotonin
which is the receptive portion of the grey matter of the spinal cord?
dorsal horn
which is the motor portion of the grey matter of the spinal cord?
ventral horn
the white matter of the spinal cord is composed of 3 rostrocaudally oriented columns in which axons can ascend or descend:
dorsal, lateral, ventral column
what is present between the two parts of the grey matter?
the central canal
where do the dorsal root ganglion neurons for touch and limb position enter in the spinal cord?
they enter the dorsal column and ascend to the brain stem for perception
what does wallerian degeneration mean?
after a stroke/a physical injury , the part of the axon distal to the cut will degenerate because it won’t be connected to the cell body anymore and won’t receive nutrients
what does the term afferent mean?
axons transmit informations towards a specific structure
what does the term efferent mean?
axons transmit info away from a specific structure
what are the fibers that are called primary afferent fibers?
dorsal root ganglion neurons, transmit sensory info from the periphery to the CNS
motor neurons transmit info from where to where?
from the CNS to the periphery
colliculi
4 bumps located on the dorsal surface of the midbrain.
2 rostral->superior colliculi, for eye movements
2 caudal->inferior colliculi, for the processing of sounds
neurons in the olives and in the base of the pons are the main sources of informations for?
the cerebellum
axons of the corticospinal tract are located?
in the pyramids and in the basis pedunculi
where are cranial nerves located? how many pairs? do they differ from spinal nerves?
in the brain stem
12 pairs
as the spinal nerves mediate sensory and motor functions but of cranial structures
where is the pyramidal decussation?
in the pyramids, at the level of the caudal medulla ( which is at the junction between the medulla and the spinal cord)
the inferior olivary nucleus is at the level of?
the olive, later to the pyramid
the dorsal column nuclei bulge to form?
the dorsal column tubercles
pontine nuclei
located within the base of the pons
transmit info from the cerebral cortex to the cerebellum
the midbrain, from dorsal to ventral, can be divided in 3 regions:
tectum, that comprises the colliculi
tegmentum
basis pedunculi
basis pedunculi+tegmentum=
cerebral peduncle
whats the structure that surrounds the aqueduct of sylvius and what does it contain?
periaqueductal gray
it contains neurons involved in endogenous pain suppression (when pain is perceived as less intense during very emotional events)
in which part of the midbrain we can find the medial lemniscus?
in the tegmentum
where is the substantial nigra located?
between the tegmentum and the basis pedunculi
it separates the corticospinal fibers (in the basis pedunculi) from the medial lemniscus (in the tegmentum)
in which portion of the midbrain can we find the corticospinal tract?
in the basis pedunculi
neurons in each half of the thalamus projects to which side of the cerebral cortex?
to the ipsilateral (same) side
internal medullary laminae
bands of myelinated axons in the thalamus.
How are the 4 major groups of neurons in the thalamus named? according to what?
they are named based on their position respect to internal medullary laminae
1. anterior nuclei
2. lateral nuclei
3. intralaminar nuclei
4. medial nuclei
name of the other 2 nuclei in the thalamus (other than the main 4 )
midline nuclei
reticular nuclei
the thalamic nuclei can be divided in 2 classes
-relay nuclei
transmit informations from a particular subcortical input to a specific cortical area
-diffuse projecting nuclei
regulate the excitability of wide regions of the cerebral cortex
NB: for each sensory modality there is a different relay nucleus
each sensory modality has a primary area that receives infos from what?
from the thalamic relay nucleus for that specific modality
ventral lateral nucleus transmit info from where to where?
from the cerebellum to the motor cortex.
the primary area of this thalamic relay nucleus is the motor cortex.
this nucleus gives rise to the corticospinal tract
association cortex, what is it?
cortical regions that lie outsider the motor and sensory areas
the association cortex is divided in 3 major regions
- parietal temporal occipital association cortex, crucial for perception and sensory guidance of movements
- prefrontal cortex, crucial for cognitive functions and organizing behaviors
- limbic association cortex crucial for emotions and memory
the 3 regions of association cortex receives inputs from which relay nuclei?
-parietal temporal occipital AC receives inputs mainly from the pulvinar nucleus
-pre frontal AC receives inputs majorly from the medial dorsal nucleus, minor input also from the pulvinar nucleus
-limbic AC receives inputs from anterior nucleus, medial dorsal nucleus and pulvinar nucleus
internal capsule
contains condensed ascending and descending axons
it is a two-way pathway that connects the thalamus with the cerebral cortex and the cerebral cortex with subcortical structures
the basis pedunculi in the midbrain are formed by?
the descending fibers of the internal capsule that project into the brain stem or further into the spinal cord
the internal capsule is divided in 3 portions
anterior limb
genu
posterior limb
axons in the internal capsule have different functions!!
neocortex
95% of the cortex
cotains 6 cell layers
comprise sensory and motor cortical areas
allocortex
5% of the cortex
different morphology
involved in olfaction and aspects of learning and memory
input layer of the cortex
-layer IV, thickest in sensory areas.
-neurons in the thalamus that project into the cortex project their axons in this layer.
There they synapse with dendrites of neurons in layer IV or neurons with their cell body in other layers but that have dendrites in layer IV.
neurons in layer IV distribute incoming informations to all the other layers
output layers of cortex
layer II, III, V and VI
layer I doesn’t contain many neurons in the mature brain
3 classes of pyramidal neurons
-corticocortical association neurons
located in layers II and III, project to cortical areas on the same side
connect other structures within the same hemisphere
-callosal neurons
located in layers II and III
project their axons to the controlateral cortex via the corpus callosum
project their axons often on the same layer of the opposite hemisphere.
-descending projection neurons
their axons descend to the brain stem, spinal cord, striatum (these neurons that descend in these regions are located in layer V) and thalamus (the neurons that descend in the thalamus are located in layer VI)
broddman’s areas
over 50 different divisions of the cortex with a different cytoarchitecture (differ In neuronal architecture: such as difference in density of neurons, difference in shape and size of neurons…)
