Control Lecture 19: The Limbic System

Question 1

What are the functions of the limbic system? Hint: Think HOME

Answer 1

H: Homeostasis via its connection to the hypothalamus e.g. blood pressure, heart rate, body temperature and the release of hormones
O: Olfaction via the para olfactory area
M: Memory - Hippocampus
E: Emotions - Amygdala

Question 2

What type of fibres are the cingulum?

Answer 2

Association fibres

Question 3

What are the anatomical relations of the amygdala?

Answer 3

Almond shaped nuclear (grey matter) complex in the medial temporal lobe. It is found deep to the uncus and is mainly involved in emotions and behaviour.

It is medial to the hypothalamus and adjacent to the hippocampus. The Amygdala is anterior to the hippocampus.

Question 4

What is the Stria terminalis?

Answer 4

Tract connecting the amygdala to the hippocampus.

Question 5

What is the fornix?

Answer 5

A tract connecting to hippocampus to the hypothalamus

Question 6

What are the connections to the amygdala?

Answer 6

• Most of the connections are with the cortex
• Minor direct projections to the olfactory, visual, auditory, somatosensory system
• Nuclei in the ANS to produce an autonomic response e.g. salivating, change in BP and temperature
• Stria terminalis - connection with the hypothalamus

Question 7

How is the hippocampal formation organised?

Answer 7

The hippocampus forms the floor of the inferior horn of the lateral ventricles.

he hippocampal formation is formed for the hippocampus proper and a debate gyrus more medial. In a coronal section they appear as two interlocking C shapes.

Question 8

What is found between the two fornices?

Answer 8

The hippocampal commissure to allow communication between the two.

Question 9

Describe the Circuit of Papaez.

Answer 9

1. In the hippocampus the memory of an event is stored including how we feel, smell, see etc.
2. This information is then transported to the hypothalamus through the fornix to the mammillary bodies. Here we can trigger autonomic responses e.g. changes in BP, HR, temperature etc.
3. The mammillary bodies can then communicate with the thalamus.
4. Thalamocingulate fibres bring information to the cingulum.
5. From the cingulum information can be transported back to the limbic system or projected to the cortex. It can be transported back to the hippocampus so the autonomic responses can be stored. It can project to different areas in the cortex such as the prefrontal lobe, frontal lobes, parietal lobes, visual system etc.

Question 10

What are the different types of memory and where are they located?

Answer 10

• Sensory Memory - located in the different sensory areas of the brain.
• Working Memory - located in the hippocampus. This is of limited capacity.
• Short-term Memory - stored in the hippocampus
• Long-term Memory - disperse around in the neocortex . It is of unlimited capacity and can be stored for a long time.