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71 Cards in this Set

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How many subdivisions of the thalamus are there?
5
What are the Thalamic subdivisions?
1. Epithalamus
2. Dorsal thalamus(The Thalamus)
3. Ventral thalamus
4. Subthalamus
5. Hypothalamus
3 components of the epithalamus:
-Habenular nuclear complex
-Pineal gland
-Posterior commisure
Habenula involved in:
limbic system
Pineal gland function:
-Synthesizes serotonin and converts it to melatonin
-Regulates sleep/wake cycle
what does the Posterior commissure link?
-Pretectal and other nuclei of the brain.
3 features of the Thalamus (dorsal)
-Thalamic nuclei
-External medullary lamina
-Internal medullary lamina
Function of the Thalamic nuclei?
A strong link to the cerebral cortex
What does the internal medullary lamina do?
Slices the thalamus into 3 parts; Medial, lateral and anterior.
What does the external medullary lamina do?
Surrounds the thalamus
What are the external and internal medullary lamina made of?
Myelinated fibers
What does the Thalamus surround?
The 3rd ventricle
What is the thalamus located medially to?
The posterior limb of the internal capsule.
What is the function of the thalamus?
MAJOR GATEWAY TO THE CORTEX
Why is the thalamus considered the major gateway to the cortex?
-Relays all sensory info
-Relays motor info from the cerebellum, spinal cord, and brainstem
-Relays emotional info
What does the thalamus do in addition to relaying information?
Integrates it
How is the Thalamus involved in emotion?
It is part of the Papez circuit of the Limbic system that projects to the limbic cortex.
What sensory information is NOT relayed via the thalamus?
Olfactory input to the thalamus
Where does olfactory input to the thalamus come from?
The piriform cortex.
What process is the thalamus intimately involved in?
The control of alertness, arousal and sleep - via the Reticular Activating System.
Does the thalamus only relay input to the cortex?
No; it also recieves cortical input to allow reciprocal communication and feedback.
What does the Ventral Thalamus subdivision consist of? (2 things)
1. Reticular nucleus of thal
2. Ventral Lateral geniculate nucleus (LGN)
2 components of the Subthalamus:
-Subthalamic nucleus
-Zona incerta
Where is the subthalamus located?
Between the hypothalamus and the dorsal thalamus
What is the Subthalamus involved in?
The basal ganglia and extrapyramidal activity.
What is the Hypothalamus?
The controlling center of the ANS.
What is the Hypothalamus involved in?
-Neurobehavioral functions
-Regulation of hormone release by the hypophysis
4 Components of the Hypothalamus:
-Hypothalamic nuclei
-Infundibulum
-Hypophysis
-Hypophyseal portal system
What is the hypophysis?
The pituitary gland
What supplies blood to the diencephalon?
Mainly PCA
Anterior nuclear group of thal:
Limbic
2 nuclei involved in the limbic cortex:
-Anterior nuclear group
-Medial dorsal nucleus
Ventral anterior nucleus:
motor
Ventral lateral nucleus:
motor
VPL
ventral posterior lateral
Somatic sensation of contralateral body
VPM
ventral posterior medial nucleus
Somatic sensation of face
LGN
Vision
(lateral geniculate nucleus)
MGN
Audition
Lateral dorsal nucleus
Emotional expression
Lateral posterior nucleus
Sensory integration
Pulvinar
Primary integrator of sensory information
Medial dorsal nucleus
Limbic
General nature of the Lateral-Ventral tier:
Simple relays
(auditory, somatic sensation)
General nature of the Lateral dorsal tier:
Complex relays
(emotion, sensory info integration)
3 diffuse projection nuclei located in the thalamus:
1. Midline
2. Intralaminar
3. Reticular nuclei
Function of the diffuse midline nuclei:
Limbic
Function of the diffuse Intralaminar nuclei:
Pain, sleep, wakefulness
Function of the diffuse Reticular nuclei:
Modulation of thalamic activity
Which nuclei are involved in the Reticular Activating System?
All diffuse projection nuclei:
-Midline
-Intralaminar
-Reticular
Which diffuse projection nuclei have a limbic function?
Just the Midline
2 Types of Thalamic neuronal circuits:
-Direct
-Indirect
Direct Thalamic circuit:
1. Afferent input
2. Thalamic relay neurons
3. Cerebral cortex
4. Back to thalamus
Indirect Thalamic circuit:
1. Afferent input
2. Thalamic INTERNEURONS
3. Thalamic relay neurons
4. Cerebral cortex
etc.
How common is Thalamic syndrome, and what are 2 common causes?
It is rare, but caused by:
-Vascular lesions (ischemia)
-Tumors
What nucleus of the thalamus is most often affected by Thalamic Syndrome?
VPL
What is the initial result of damage to the VPL?
Transitory Hemialgesia - loss of sensation from the contralateral side.
What happens to the patient after the initial transitory period of sensation loss?
Painful sensations with noxious stimuli
What can result from progression of Thalamic syndrome?
Constant or recurrent pain on the contralateral side to the lesion, not caused by any stimulus.
What is it called when pain is felt without a stimulus?
Dyesthesia.
How does the sensory system respond to Thalamic syndrome?
By increasing the threshold of response to stimuli for pain, temp, and tactile stimulus.
How is pain sensation changed by Thalamic syndrome?
Though higher, once the threshold is reached the pain felt has a strong emotional overtone to it.
What is the Non-specific System of the thalamus?
A system that projects to a wide area of the cortex.
What is the Nonspecific system activated by?
Repetitive, low frequency stimulation (like biochem lectures).
2 types of connections in the non-specific system:
-Interconnections with each other
-Reciprocal connections with specific thalamic nuclei
What is the effect of repetitive stimulation of the Nonspecific System?
Waxing and waning activity in the cortex
What does the Nonspecific system control?
The level of neuron excitability over wide areas of the cortex.
The HYPOTHALAMUS is located where?
Ventral diencephalon - in the walls and floor of the 3rd ventricle.
What is the hypothalamus connected to, and by what?
Hypophysis (pituitary) via the Infundibulum
How is the hypophysis connected to the
-Anterior pituitary
-Posterior pituitary
Anterior: via the portal system
Posterior: via neural projections
What is the hypothalamus essential for controlling? What is it called?
ANS - the HEAD GANGLION OF THE ANS
What is the hypothalamus concerned with?
-Homeostatic regulation
-Survival of the individual and THE SPECIES!!!