Olfactory and Limbic Systems

Question 1

What does the olfactory system include?

Answer 1

• epithelium in the nose
• nerves
• bulb
• tract
• cortex

Question 2

Where are olfactory neurons located?

Answer 2

in the olfactory mucosa, restricted to the upper part of the nasal cavity

Question 3

What does the olfactory epithelium contain?

Answer 3

olfactory neurons, supporting cells, and basal cells

Question 4

What do basal cells do?

Answer 4

renew the bipolar neurons throughout life

Question 5

Where do olfactory neurons in the olfactory epithelium send their axons?

Answer 5

through the cribriform plate to synapse on mitral cells in the olfactory bulb

Question 6

What do axons of the olfactory neurons constitute?

Answer 6

the olfactory nerve (cranial nerve I)

Question 7

What do axons of the mitral cells constitute?

Answer 7

the olfactory tract

Question 8

What does the olfactory tract split into?

Answer 8

the medial and lateral olfactory striae

Question 9

Where do the medial olfactory stria terminate?

Answer 9

• septal nuclei
• anterior perforated area

Question 10

Where do the lateral olfactory stria terminate?

Answer 10

• cerebral cortex of uncus
• amygdala

Question 11

What is involved in the interpretation of smell?

Answer 11

• septal nuclei
• anterior perforated area
• cortex of the uncus

Question 12

What is the limbic system concerned with?

Answer 12

• feeding behaviour
• control of aggression
• emotion
• sexual arousal
• memory

Question 13

How are structures in the limbic system arranged?

Answer 13

in a ring-like manner, between the diencephalon and the telencephalon

Question 14

What are the 3 gyri associated with the limbic system?

Answer 14

• parahippocampal gyrus
• subcallosal gyrus
• cingulate gyrus

Question 15

Give examples of nuclei in the limbic system

Answer 15

• hippocampal formation
• amygdala
• basal forebrain
• septal nuclei

Question 16

What are many of the nuclei of the limbic system connected to and why?

Answer 16

the hypothalamus for regulation of body homeostasis and autonomic responses

Question 17

What are the 4 components of the hippocampus formation?

Answer 17

• entorhinal cortex
• subiculum
• hippocampus proper
• dentate gyrus

Question 18

What is the hippocampus formation made up of?

Answer 18

a special type of cerebral cortex rolled into the medial aspect of the temporal lobe

Question 19

What is the hippocampus proper?

Answer 19

the actual structure of the hippocampus divided into CA fields 1-3

Question 20

What are the principal cells of the hippocampus?

Answer 20

pyramidal neurons

Question 21

What does the dentate gyrus contain?

Answer 21

dentate granule neurons formed throughout life via neurogenesis

Question 22

What do the dendrites of both granule and pyramidal cells contain?

Answer 22

large numbers of dendritic spines

Question 23

What does the hippocampal formation receive input from?

Answer 23

other association areas of the cortex via the entorhinal cortex

Question 24

Describe the hippocampal trisynaptic circuit

Answer 24

1. entorhinal cortex projects to dentate granule neurons (perforant path)
2. dentate granule neurons project to pyramidal neurons in CA3 (mossy fibres)
3. CA3 pyramidal neurons project to CA1 pyramidal neurons (Shaffer collaterals)

Question 25

What is LTP?

Answer 25

the cellular substrate for learning and memory dependent on calcium entry via the NMDA glutamate receptor

Question 26

What do CA1 pyramidal neurons project to?

Answer 26

the subiculum which projects to the entorhinal cortex which in turn projects to other association areas of the cortex

Question 27

Where do axons sent from the hippocampus that form the fornix terminate?

Answer 27

in the mammillary bodies of the hypothalamus

Question 28

What is the hippocampus essential for?

Answer 28

explicit/declarative memory

Question 29

What does bilateral damage or removal of both hippocampi cause?

Answer 29

anterograde amnesia

Question 30

What is anterograde amnesia?

Answer 30

the absence of conscious recall of newly acquired information for more than a few minutes

Question 31

How can the hippocampus be damaged?

Answer 31

global ischemia, AD and epilepsy

Question 32

How can dentate gyrus neurogenesis be decreased?

Answer 32

stress and depression

Question 33

How can dentate gyrus neurogenesis be increased?

Answer 33

- maternal choline intake (eggs and beef liver) - enriched environment - physical exercise - antidepressant drugs

Question 34

Where is the amygdala located?

Answer 34

in the anterior part of the temporal lobe

Question 35

What inputs does the lateral nucleus of the amygdala receive?

Answer 35

olfactory, visual, auditory, tactile and visceral

Question 36

Where does the central nucleus of the amygdala project?

Answer 36

- hypothalamus - brainstem

Question 37

What do central nuclei of the amygdala projecting to the brainstem do?

Answer 37

activate neurons that influence respiratory rate and autonomic activity to facilitate defensive/evasive activity

Question 38

What is the amygdala concerned with?

Answer 38

mood and emotion; it interprets and recalls emotional content of visual inputs and events

Question 39

What are autonomic responses of the amygdala?

Answer 39

heart rate, respiration, blood pressure, and gastric motility

Question 40

What does removal of the amygdala in monkeys and rats cause?

Answer 40

a greatly increased sexual drive

Question 41

What does damage to the amygdala result in?

Answer 41

- loss of fear and aggression - hyperorality (excessive attention to stimuli with oral tendencies) - hypersexuality

Question 42

What is the basal forebrain?

Answer 42

the grey matter in and around the anterior perforated substance

Question 43

What are the cholinergic nuclei of the basal forebrain?

Answer 43

- nucleus basalis of Meynert, which projects to all parts of the neocortex - septal nucleus, which projects to the hippocampus

Question 44

What does the cholinergic supply from the nucleus basalis in the neocortex contribute to?

Answer 44

the awake pattern on EEG recordings since it is tonically active

Question 45

What are drugs used to treat AD?

Answer 45

acetylcholine esterase inhibitors that prolong the effect of ACh

Question 46

Where are septal nuclei located?

Answer 46

next to the septum pellucidum, separating the lateral ventricles

Question 47

What do septal nuclei receive afferents from?

Answer 47

- medial olfactory stria - hippocampus - amygdala - brainstem monoaminergic neurons

Question 48

What do septal nuclei send efferents to?

Answer 48

- the habenular nucleus to affect the sleep-wake cycle - hippocampus via the septo-hippocampal pathway

Question 49

What do the septal nuclei affect?

Answer 49

rhythm in the hippocampus, which is important for formation of memories

Question 50

What does lesion of the septal nuclei in animals produce?

Answer 50

signs of extreme displeasure

Question 51

What does electrical stimulation of the human septal area produce?

Answer 51

sexual sensations similar to orgasm