L05 - Thalamus and Cortex Flashcards
Shape and location of the Thalamus in relation to the brainstem?
Shape = Large ovoid mass of gray matter. Anterior end is narrow and rounded and posterior end is expended to form the pulvinar
Location: Major part of diencephalon, both sides of 3rd ventricle joined by Interthalamic adhesion
Topographic location of the thalamus - Anterior and Posterior?
Anterior: interventricular foramen
Posterior: pulvinar (+ Pineal gland)
Topographic location of the thalamus - Superior and inferior?
Superior: stratum zonale (White mater) & strita terminalis
Inferior: tegmentum of midbrain
Topographic location of the thalamus - Medial and lateral?
Medial: lateral wall of 3rd ventricle
Lateral: nerve fibers of internal capsules
What internal structures are destroyed in a lateral dissection of the thalamus?
Caudate nucleus and putamen
Lentiform nucleus = Putamen + Globus pallidus. Inside basal ganglia
4 parts of the diencephalon?
Epithalamus
Thalamus
Subthalamus
Hypothalamus
(Hypothalamic sulus divides thalamus from hypothalamus)
List some structures that lie inferior to the hypothalamus?
Oculomotor nerve
Mammillary body
Infundibulum
Optic nerve and chiasm
Function of epithalamus?
pineal gland secretes melatonin
Control circadian rhythm
Function of thalamus?
1) Relays all sensory input to the cortex (esp. frontal motor region)
2) Controls the perception of touch, pressure, temperature
3) Involved in movement control
Function of Subthalamus?
Connects subthalamic nuclei and basal ganglia
Controls body movement, emotion
Function of Hypothalamus?
Controls body temperature
Regulates feeding behavior
Regulates emotion, circadian rhythms, pattern of wake/sleep
Releases hormones to regulate pituitary gland (vs. reticular formation = nerve control)
Function of the Anterior group of thalamic nuclei?
part of limbic system: memory, emotion:
Hippocampus, Mammilary body input
Cingulate cortex output
Function of the Ventral (antero-lateral) group of thalamic nuclei?
Signals from cerebellum, basal nuclei, globus pallidus to motor areas of cortex
Somesthetic output to postcentral gyrus
Function of the Lateral group of thalamic nuclei?
Somesthetic output to cortical association areas
Contributes to emotional function of limbic system
Function of the Posterior group of thalamic nuclei?
Visual signals to occipital lobe / primary visual cortex (via lateral geniculate nucleus)
Auditory signals to temporal lobe / primary auditory cortex (from inner ear > inferior olivary nucleus > medial geniculate nucleus)
What separates the thalamic nuclei into groups?
Lamina
i.e. internal medullary lamina separates lateral and medial thalamus
External medullary lamina enclose Lateral thalamus
Describe the division of the ventral thalamic nuclei
From antero- lateral to postero- lateral:
- Ventral anterior (VA)
- Ventral lateral (VL)
- Ventral posterior (VP)
VP subdivided into:
V. Intermedial (VI),
V. posteromedial (VPM),
V. posterolateral (VPL)
Input and output flow of:
Ventral lateral thalamus?
Input: Globus pallidus + Cerebellum
Output: Motor cortex
Input and output flow of: Ventral posterior (VPL and VPM included) thalamus?
Input: Medial, spinal and trigeminal lemnisci (sensory from lower and upper extremities + head and neck)
Output: Somatosensory cortex
Input and output flow of:
Ventral anterior thalamus?
Input: Globus pallidus/ basal ganglia
Output: Premotor cortex
Input and output flow of:
Lateral geniculate body?
Input: Optic tract
Output: Primary visual cortex
Input and output flow of:
Medial geniculate body?
Input: Inferior branchium (inner ear)
Output: Primary auditory cortex
Input and output flow of:
medial thalamus?
Input: substantia nigra, Amygdala, Olfactory cortex
Output: Prefrontal cortex
(Emotional signals, Awareness of emotions)
Difference in the input of VPL and VPM?
VPL = sensory from lower and upper extremities
VPM = sensory from Head and neck
Pain at dorsum of the foot: trace the neural pathway to the CNS?
Nociceptor in skin > dorsal horn spinal cord > spinothalamic tract > medulla oblongata > VPL > Somatosensory cortex
Descending motor pathway passes through thalamus for processing. True or False?
False
Motor never passes through thalamus, only bypasses to brainstem/ spinal cord/ Diencephalon/ Cerebellum
List the components of the Basal Ganglion circuit?
- Striatum
- Globus pallidus (internal and external segments)
- Subthalamic nucleus
- Substantia nigra (pas compacta + pars reticulata)
Go through the direct pathway in Basal ganglion circuit to increase motor output?
Cortex release Glutamate
> > Stimulate striatum to increase more GABA/ Substance P
> > Inhibit globus pallidus Internal** + Substantia nigra pars reticulata, less GABA released
> > Thalamus less inhibited by GABA, release more Glu.
> > Increase stimulation of Supplementary motor area, increase motor output
Go through the indirect pathway in Basal ganglion circuit to decrease motor output?
Cortex releases Glutamate
> > Striatum stimulated, Increase GABA/ Enkephalin release to Globus Pallidus External**
> > G.P. external more inhibited, released less GABA to Subthalamic nucleus
> > Subthalamic nucleus less inhibited, releases more Glutamate to G.P. Internal**
> > G.P. Internal releases more GABA to Thalamus
> > Thalamus more inhibited, releases less Glutamate to supplementary motor area
> > Decrease motor output
What is the role of substantia nigra in the basal ganglion circuit?
Cortex releases glutamate
> > Striatum releases GABA to Substantia nigra pars compacta
> > Inhibit S.N, less dopamine released back to Striatum
> > Fine tune motor control
List the lobes in the cerebral cortex.
Frontal, Parietal, Occipital, Temporal
How to locate frontal and parietal lobes?
Central sulcus
Anterior to Parietal lobe (i.e. primary somatosensory cortex)
Posterior to frontal lobe (i.e. primary motor cortex)
List the areas of the frontal lobe of cortex?
Primary motor cortex Motor association area Broca area Prefrontal cortex Olfactory association cortex
List the areas of the Parietal lobe of cortex?
Primary somatosensory cortex
Somatosensory association cortex
List the areas of the temporal lobe of cortex?
Wenicke area
Primary auditory cortex
Auditory association area
List the areas of the occipital lobe of cortex?
Primary visual cortex
Visual association cortex
Which cortex areas are involved in language?
Broca’s area in frontal lobe = Generate and use of language
Wenicke’s area in temporal lobe = Comprehension of language
Connected by Arcuate fasciculus
3 types of fibers in the cortex and their functions?
1) Association fibers: interconnect cortical areas within the same hemisphere
2) Arcuate fibers: interconnect gyri within a lobe
3) Longitudinal fasciculi (e.g. superior longitudinal fasciculus): interconnect frontal lobe with other cerebral lobes
Failure of the Broca’s/ Wernicke’s area produces what symptoms?
Broca’s = speaks vocabulary but not sentence, expressive aphasia
Wernicke’s = speaks sentence but no comprehension, receptive aphasia
List the layers of the cortex from superior to inferior.
Molecular layer
External granular layer
External pyramidal layer
Internal granular layer
Internal pyramidal layer
Multiform layer
List the sequence of brain areas involved in the Limbic system, starting with Parahippocampal gyrus.
Parahippocampal gyrus
> > Hippocampus
> > Fimbria
> > Fornix
> > Mamillary body
> > Anterior Thalamus
> > Posterior cingulate gyrus
> > Cortex/ back to Parahippocampal gyrus
List the sequence of brain areas involved in the Papez circuit, starting with the Hippocampus.
Hippocampus
> > fornix
> > mammillary body + mammillothalamic tract
> > anterior nucleus of thalamus
> > anterior cingulate gyrus / area and prefrontal association area of cortex (layer 5)
> > cingulum
> > entorhinal cortex of parahippocampus gyrus
> > hippocampus
What is the function of the Hippocampal formation?
Learning, recent memory, perception of time, navigation and emotion
Function of the Amygdaloid complex?
Amygdala complex connected to Stria terminalis above thalamus:
Involved in defense and attack, fear, rage
Influences endocrine functions of hypothalamus
Function of Entorhinal cortex?
Inside parahippocampus at medial temporal lobe
Interface between hippocampus and neocortex: memory, navigation and the perception of time
List the components of the Hippocampal formation?
Parahippocampus
Dentate gyrus
Hippocampus
Fimbria
If a SPECT scan reveals isolated frontal lobe shrinkage, is it Alzheimer’s disease or Frontotemperol lobe dementia?
Not alzheimer’s»_space; temoral lobe degeneration mostly + diffuse involvement
Histological change seen in CJD?
Creutzfeldt-Jakob Disease (CJD) = prion disease
Spongiform cortex: formation of vacuoles (empty space), tau
Rapidly affects mental acuity, memory
Parts of brain involved in explicit memory?
Includes episodic and semantic memory:
Hippocampus, Nucleus Basalis, Medial temporal lobe
Divide Implicit memory into subcategories and their related brain areas.
1) Skill and habit»_space; Striatum, Motor areas of cortex, cerebellum
2) Emotional association»_space; Amygdala, Insula
3) Conditioned reflexes»_space; Cerebellum
Part of brain involved in Working memory?
Prefrontal cortex
> > Ventrolateral prefrontal cortex for non-spatial memory e.g. color & shape
> > Dorsolateral prefrontal cortex for Spatial memory
