Thalamus Flashcards
what vesicle makes up the thalamus?
the diencephalon
most caudal of the proencehalon (dien and telen)
how many neurons are in the thalamus?
about 10 million neurons in each half
broken into 50-60 nuclei
what are the 4 parts that make up the thalamus?
1- epithalamus
2-subthalamus
3-hypothalamus
4-dorsal thalamus
what are the new positional terms at this level?
anterior= rostral
posterior= posterior
dorsal=superior
ventral=inferior
what is the epithalamus?
what does it constitute?
what structures lie within it?
roof of the 3rd ventricle
structures comprising it constitute a linkage between limbic system components in the forebrain and other parts of the brain
habenular trigone and nuclei
pineal body
striate medularis
what is the pineal body responsible for?
secretion of melatonin which is important in:
- regulating sleep/wakefulness cycle
- sexual maturity (onset of puberty)
- mating season (animals)
what is the habenula?
a nucleus that projects to the midbrain and is thought to be involved in releasing neuromodulators, such as dopamine, norepinephrine, and serotonin
what is the subthalamus?
what is the bulk of the subthalamus made up of?
border between thalamus and midbrain just rostral to substangia nigra
this part of the diencephalon is wedged laterally between the thalamus and the hypothalamus
the bulk of the subthalamus is made up of the sub thalamic nucleus and another gray matter component is the zone incerta. There are also several fiber bundles in the subthalamus:
- subthalamic fasciculus
- lenticular fasciculus
- ansa lenticularis
what is the subthalamus important for?
important for regulating movements produced by skeletal muscles
it is interconnected with other structures important in movement: basal ganglia and substantia nigra
what is the name of a lesion at the subthalamus?
hemiballisums
basically person flails extremities uncontrollably
can be dangerous to work with patient because of this
what is the hypothalamus?
head of autonomic endocrine and limbic system
involved in homeostatic control
does this by means of its neuroendocrine role in conjunction with the pituitary gland as well as by its influence on the autonomic NS, which helps regulate body temperature, the cardiovascular system, and food and water intake
it is an integral component of the limbic system
what is the dorsal thalamus?
robin’s egg
refer to this as the thalamus
general characteristics of the thalamus:
how long?
formed by what plates?
~ 3 cm long (ant-post)
1.5 cm ventral to dorsal
formed by the ALAR plates- primarily sensory but has some motor nuclei
all sensations go to thalamus before cerebrum
what are the 2 regions of the thalamus?
Allothalamus:
- afferents from amygdala
- centre-median parafascicular complex (BG)
- intralaminar region
Isothalamus:
-bulk of the thalamus
what are the functions of the thalamus?
relay and integration of sensory information
effects consciousness and helps with focusing of attention
relay and integration of motor information
what are the motor relay nuclei?
ventral anterior (BG project here??)
ventral lateral (cerebellum projects here??)
what are the sensory relay nuclei?
ventral posterior (VPL- spinothalamic tracts (fast/primary pain; medial lemniscus- discriminative)
arcuate nucleus (VPM- VTTT discrim, P&T face)
lateral geniculate- vision
medial geniculate- hearing
what are the limbic relay nuclei?
anterior
(memory and attention?)
(related to emotion and behavior)
what are the features (characteristics) of the relay nuclei?
convey information to cerebral cortex
receive direct inputs from long ascending tracts (spinothalamic, medial lemniscus, optic tract, auditory)
process info derived from basal ganglia, cerebellum (motor)
anterior- limbic system
all have reciprocal connections (loops) with well defined cortical areas (except reticular thalamic nuclei) (cortex says what it wants and how it wants it)
they undergo degeneration on ablation of the specific cortical area to which they project
what separates the R and L halves of the thalamus?
what forms the roof of the 3rd ventricle?
3rd ventricle
tela choroidea- bears a choroid plexus
what joins the 2 halves of the thalamus?
massa intermedia or interthalamic adhesion
what is the internal medullary lamina?
band of myelinated fibers subdivides the thalamus of each hemisphere into 3 unequal parts :
medial and lateral nuclear groups from the ventral nuclear group and bifurcates at its rostral extent to encompass an anterior nuclear group.
what forms the lateral wall of the thalamus?
a thin sheet of cells called the thalamic reticular nucleus
this group of cels separates the lateral group of nuclei from the posterior limb of the internal capsule
what lies adjacent to the 3rd ventricle on the medial wall of the thalamus ?
narrow band of cells making up the midline nuclei resides on the medial wall of the thalamus
what does the thalamus serve as?
station for processing and relaying neuronal activity from all types of peripheral sensory receptors, from the basal ganglia, and from the cerebellum to the cerebral cortex
with the exception of the reticular nucleus, all the thalamic nuclei project to the :
cerebral cortex (thalamocortical fibers) and receive afferents (corticothalamic fibers) from the same cortical region to which they project