Anatomy: Limbic Lobe, Hippocampus, Amygdala

Question 1

What is the limbic system?

Answer 1

Interconnected structures that form a border/limbus around the brainstem.
* Limbic lobe- It is a rim of the cerebral cortex (GREY matter) adjacent to the corpus callosum and diencephalon
* Limbic system includes the limbic cortex, as well as related subcortical nuclei.

Question 2

Describe the functions of the limbic system

Answer 2

Question 2

James Papez (1937) identified that emotion is not a function of any specific brain center but a circuit involving 4 basic structures.
Describe the REVISED Papez circuit

Answer 2

Question 3

What are the main components of the limbic system?

Answer 3

Limbic cortex; this inc the parahippocampal + cingulate gyrus, medial orbitofrontal cortex
Hippocampal formation: inc dentate gyrus, hippocampus
Amygdala
Olfactory cortex
Diencephalon; incs hypothalamus, thalamus
Basal Ganglia; inc ventral striatum
Basal forebrain
Septal nuclei

Question 4

Label the hidden structures

Answer 4

Question 5

Describe the 3 arcs of the cerebral cortex which are part of the limbic system

Answer 5

Question 6

What is the cingulate gyrus and what happens if it gets damaged?

Answer 6

Mediates emotional responses to pain
Assigns emotion to internal and external stimuli
Enables us to express our emotions out loud
Damage–> autonomic system loses ability to respond to conditioned stimuli, can result in aggression, shyness and reduced affection

Question 7

What is the indusium griseum? Label it on here

Answer 7

• Thin sheet of grey matter
• Along with the medial and lateral longitudinal striae it
  extends from the paraterminal gyrus via the gyrus fasciolaris to the dentate gyrus

Question 8

What is the dentate gyrus? And label this

Answer 8

Notched band of grey matter
Lies between the fimbria of the hippocampus and the
parahippocampal gyrus
* Separated from it by the hippocampal sulcus

Question 9

Label and describe the hippocampus

Answer 9

Situated along the floor of the inferior horn of the lateral ventricle
Situated above the dentate gyrus
Anterior end presents a bulbous extremity marked
by ridges - ‘pes hippocampi’

Question 10

Label the coronal section of the hippocampus.

Answer 10

Question 11

What is the importance of hippocampal function?

Answer 11

Functions:Making new memories & consolidating
information from short term to long term memory

Damage:
* Involved in severe mental illness; Reduced volume in schizophrenia, PTSD, depression
* Affected in Alzeimer’s disease

Question 12

What is the fornix?

Answer 12

Question 13

Using this image, describe the passage of fibres in the fornix

Answer 13

Question 14

Label the hidden structures

Answer 14

Question 15

How does the fornix end?

Answer 15

At its termination the fibres of the fornix split to pre and post commissural fibres
Pre-commissural fibres → septal area
Post-commissural fibres → mamillary body, anterior nucleus of thalamus

Question 16

What is the amygdaloid body?

Answer 16

Question 17

What are the connections of the amygdala?

Answer 17

Receives Input from: from lateral olfactory stria, parahippocampal gyrus (visual, auditory, tactile, taste sensory input)

Output : via stria terminalis into 3 sets of fibres
* Supracommisural –terminate into the septal nuclei
* Commisural- terminate in the ant comissure
* Subcommisural –anterior nuclei of hypothalamus, anterior perforated substance
Commissural fibers connect an area in one hemisphere with an area in the opposite hemisphere.

Question 18

Functions of amygdala?

Answer 18

Electrical stimulation of amygdala can lead to emotional attacks (rage)
Rabies (attacks the temporal lobe) leads to violence
Lesions of the amygdala causes reduced ability to identify
motivational and emotional significance of events

Question 19

What is the olfactory pathway and what does it consit of?

Answer 19

Consists of Olfactory: nerves, bulb, tract, stria, Prepyriform cortex, Primary olfactory cortex
The nerves of the olfacrtory pathway are located in the upper part of the nasal mucosa
Nerve root routes pass superiorly through the cribiform plate of ethmoid and synapse in the olfactory bulb.

Question 20

What is this?

Answer 20

Question 21

Why is the APS important?

Answer 21

The arteries of the anterior perforated substance (APS) are important due to their role in supplying blood to important internal structures such as the internal capsule, putamen and caudate nucleus.

Question 22

What is the medial and lateral olfactory stria?

Answer 22