Limbic system

Question 1

What is the role of the Olfactory system?

Answer 1

Responsible for sense of smell.

Question 2

What are the components of the olfactory epothelium?

Answer 2

Bipolar olfactory neurones

Sustentacular cells

Basal cells

Question 3

What is the role of the basal cells?

Answer 3

allow for regeneration.

Question 4

What is the role of the sustentacular cells?

Answer 4

provide metabolic support.

Question 5

Explain the structure of the bipolar olfactory neurones.

Answer 5

2 processes.

External sensory receptor component, and one to the olfactory bulb.

Question 6

Where is the olfactory bulb located?

Answer 6

Sits above the cruciform plate.

Question 7

What is the role of the olfactory bulb?

Answer 7

Receive axons from olfactory epithelial bipolar cells. These synapse at a glomerulus with a second order olfactory neurone

Question 8

What is the role of the olfactory tract? What does it divide into?

Answer 8

Carry second order neurones (olfactory mitral cells).

Splits into medial and lateral olfactory stria.

Question 9

What can damage to the cortices lead to?

Answer 9

Inhibition of normal smell processes

Question 10

Where does higher processing of olfactory sensory input occur?

Answer 10

piriform and orbitofrontal cortices

Question 11

Label diagram showing location of olfactory epithelium + its components

Answer 11

Question 12

Explain the prodromal aura epileptic patients might experience.

Answer 12

Epilepsy often focused in temporal lobe (containing piriform complex). Seizure can be anticipated when smelling something not present.

Question 13

What is anosmia? How can it arise?

Answer 13

Clinical deficity of olfactory system.

mid-face trauma –> fracturing of cribiform plate + shearing of neurones.

Question 14

What disease is a loss of smell a predictor for?

Answer 14

Parkinson’s

Question 15

List some roles of the limbic system.

Answer 15

Memory

Sexual/reproductive behaviour

Defence/attack behaviour

Maintenance of homeostasis by activating visceral effectors, modulating pit hormone release and initiating feeding/drinking

Question 16

What brain structures are involved in the limbic system?

Answer 16

Amygdala anteriorly, hippocampus posteriorly (on floor of inferior horn of lateral ventricle), cingulate cortex, olfactory tracts (?)

Question 17

What happens to the hippocampus in Alzheimer’s?

Answer 17

Shrinkage.

Question 18

What is the primary afferent pathway of the hippocampus?

Answer 18

perforant pathway from the entorhinal cortex. All other cortical regions go via entorhinal cortex.

Question 19

What are the destinations of efferent hippocampal information?

Answer 19

fimbria/fornix (Papez circuit)

Question 20

Where is the fornix located?

Answer 20

Immediately below the corpus callosum.

Question 21

Where are mammillary bodies found?

Answer 21

At the ends of the fornix.

Question 22

What is the main output of the hippocampus?

Answer 22

fornix

Question 23

Broadly outline pathology of Alzheimer’s

Answer 23

cortical atrophy. Loss of neurones + ventricles grossly enlarged. Hippocampal shrinkage + sulci widening.

Question 24

Compare the intracellular and extracellular patholgoy of Alzheimer’s

Answer 24

Intracellular - cytoskeleton compromised. Tau protein build up.

Extracellular - senile plaques of protein develop between cells in neurophil.

Question 25

Broadly outline the clinical progression of Alzheimer’s and the associated anatomical changers.

Answer 25

Early - short term memory issues. Hippocampus and enteroginal cortex.

Moderate - depressing apraxia. Parietaql lobe.

Late - executive skill loss. Frontal lobe.

Question 26

What is the Papezs circuit?

Answer 26

a neural circuit to control emotional expression.

Question 27

What are the components of the Papez ciruit and their roles?

Answer 27

Hippocampus: present on the floor of the inferior horn of the lateral ventricle, outputting to the fornix

Fornix: fibre pathway from the inferior horn, passing under the corpus callosum to synapse in the mamillary bodies (hypothalamus)

Mammillo-thalamic tract: projects to the anterior nucleus of the thalamus

ANT: produces thalamo-cortical projections to the cingulate cortex

Cingulate cortex: allows for emotional colouring from the neocortex

Question 28

What connects the cingulate cortex to the hypothalamus?

Answer 28

Cingulum bundle.

Question 29

What is the role of the amygdala?

Answer 29

Perception of fear, anxiety and fight/flight

Question 30

What structures provide afferent information to the amgydala?

Answer 30

olfactory cortex, septum, temporal neocortex, hippocampus and brainstem

Question 31

Where does the amgydala output to?

Answer 31

stria terminalis.

Question 32

Explain Kluver-Bucy syndrome.

Answer 32

bilateral lesions of anterior temporal lobe –> hyperorality (exploring with mouth), loss of fear, visual agnosia (can’t recognise objects) and hypersexuality

Question 33

What are the main functions of the septum?

Answer 33

reinforcement and reward.

Question 34

What structures provide afferent information to the septum?

Answer 34

amygdala, olfactory tract, hippocampus and brainstem

Question 35

Where does the septum output to?

Answer 35

stria medularis thalami, hippocampus, hypothalamus

Question 36

What areas are associated with aggression?

Answer 36

hypothalamus, brainstem (periaqueductal grey area) and amygdala

Question 37

Explain the route of the mesolimbic pathway.

Answer 37

Ventral tegmental area of midbrain origin –> cortex, amgydala and nucleus accumbens via medial forebrain.

Question 38

What NT does the mesolimbic pathway use?

Answer 38

Dopameme

Question 39

How do opioids and amphetamines increase DA release in the nucleus accumbens?

Answer 39

Stimulating midbrain neurones

Promoting DA release

Inhibiting DA reuptake