Thalamus

Question 1

What are the components of the Thalamus? 4 plus 3 subpoints

Answer 1

Epithalamus
Includes Pineal Gland
Thalamus
Subthalamus
Hypothalamus
Only part of diencephalon visible from the outside.
The visible part includes the Infundibular stalk and Mammilary bodies.

Question 2

What are the 2 structures of the Epithalamus?

Where does the epithalamus lie in relation to the Thalamus?

Answer 2

Haunula and Pineal Gland

Caudal structures

Question 3

Pineal Gland
Describe the structure.
What did early anatomists think the purpose of the pineal gland was?
What 3 things are caused by tumors of the pineal gland?

Answer 3

Unpaired midline structure superior to the superior colliculi.
Was the seat of the soul (only single midline structure)
Tumors cause:
Hydrocephalus from compression of the aqueduct.
Eye movement defects and pupillary reaction deficits (due to pressure to CN III & IV)
Changes in sexual development in youth.

Question 4

What is the function of the Pineal Gland?

What Phenomenon is this associated with?

Answer 4

Human function is associated with Circadian rhythms (24 hour cycles) such as sleep-wake cycles.
Melatonin is synthesized in the Pineal Gland for hormonal regulation within the sleep cycle.

Question 5

Where does the Subthalamus sit?

What larger system of structures is it a part of?

Answer 5

It is lateral to the hypothalamus, inferior to the thalamus and medial to the basis pedunculi and internal capsule.
Part of the basal ganglia.

Question 6

What are the components of the Subthalamus?

Answer 6

Subthalamic nucleus.
Zona incerta–which sits superiorly to subthalamic nucleus, next to the thalamus. Zona incerta is believed to be a continuation of the reticular formation. Function is unknown. (A continuation of the reticular formation on up into the diencephalon)

Question 7

Describe the physical makeup of the Thalamus.

The thalamus is part of a remarkable number of pathways, these include:

Answer 7

The thalamus is one of a pair of large egg-shaped nuclear masses with a posterior appendage. This makes up 80% of the volume of the diencephalon.

All sensory pathways to the cerebal cortex (except olfactory) relay here.
The cerebelum, basal ganglia, and limbic structures involve relays in the Thalamus.

Question 8

What are the 5 subdivisions of the Thalamus

Answer 8

1. Anterior division
2. Medial division
3. Lateral division
4. Intralaminar Nuclei
5. Reticular nucleus.

Each of the five subdivision contain one or more principle nuclei.

Question 9

What is the internal medullary lamina?

Answer 9

A thin curved sheet of myelinated fibers dividing the thalamus into medial and lateral groups of nuclei. It also superiorly divides around the Anterior nucleus.

Question 10

What is in the Anterior Division of the Thalamus?

Answer 10

The anterior nuclei

Question 11

Where is the Thalamic Reticular Nucleus found?

What is significant about its name?

Answer 11

Lateral division.
The Thalamic Reticular Nucleus is named for its reticulated appearance NOT because of any association with the reticular formation.

Question 12

What is the function of the thalamus?

Answer 12

Site where decisions are made about what information should reach the cerebral cortex for further processing.
For each particular type of information processed by an area of the thalamus, its function is determined by its input and output connections.

Question 13

Describe the Thalamic Nuclei outputs

Answer 13

75% of thalamic neurons are Projection nuclei with outputs from the Thalamus.
Small inhibitory neurons with GABA as a neurotransmitter.

Question 14

What are the Specific and Regulatory inputs of Thalamic Nuclei?

Answer 14

Specific input.–When an input conveys information which a given thalamic nucleus may pass on to the cerebral cortex, it is regarded as a Specific Input

Regulatory Input–When an input is conveying information that will be used to determine if other information is passed on and if so, to which target, it is regarded as regulatory input. aka computational inputs.

Question 15

What are the 5 locations where specific inputs typically come from?

What are the 3 locations where regulatory inputs typically come from?

Answer 15

1. Sensory pathways
2. Basal ganglia
3. Cerebellum
4. Limbic system
5. Cerebral cortex
6. association areas of the Cerebral Cortex
7. Thalamic reticular nucleus
8. Reticular formation. ***the 2 reticular structures are involved in regulatory inputs.

Question 16

Describe Specific Relay Nuclei or Relay Nuclei as a functional classification of thalamic nuclei.

Answer 16

These receive well-defined bundles of specific input from:
Ascending sensory pathways.
Major subcortical nuclei. (brainstem nuclei, cerebellum)
Process this input,
Project to selected FUNCTIONAL AREAS of the cerebral cortex.

Question 17

What are the 4 qualities of Association Nuclei as defined by the functional classification of thalamic nuclei.

Answer 17

1. Primarily have reciprocal connections with the association areas of the cerebral cortex.
2. Receive specific inputs from the cerebral cortex and subcortical areas.
3. and Appear to have a gating and distribution role to association areas of the cortex.
4. Project to the 2 primary association cortex areas:
   Parietal-occipital-temporal cortex
   Prefrontal cortex

Question 18

What are the 4 qualities of Nonspecific Nuclei as defined by the functional classification of Thalamic Nulei?

Answer 18

1. Their axonal branches are widely distributed.
2. They spread influences over large areas of he cerebral cortex.
3. They exert generalized effects.
4. Two of these, the intralaminar and midline nuclei seem to have a special role in the function of the basal ganglia and limbic systems.
   Midline nucleus is at the location of the interthalamic adhesion. (Most medial structure)