6.4.1 Limbic System

Question 1

What makes up the archicortical area of limbic system?

Answer 1

hippocampal formation (hippocampus and dentate gyrus)

Question 2

Olfactory receptors are bound directly to, what happens on binding of odorant?

Answer 2

• Olfactory receptors connect directly to olfactory nerves
• Binding of an odorant initiates a GPCR cascade

Question 3

Olfactory bulb synapses with the Entorhinal Cortex and then does what?

Answer 3

-Synapses with the hippocampus

-Consolidation into LT memory

Question 4

What are the functions of the limbic system?

Answer 4

Homeostasis

Olfaction

Memory

Emotions

Question 5

What is the neurotransmitter for the limbic system?

Answer 5

Question 6

What is the role of the taste receptor cell and where does it signal to?

Answer 6

-receives taste info and provides afferent info to the solitary nucleus

TO THE SOLITARY NUCLEUS OR BUST

Question 7

What is the role of the nucleus accumbens?

Answer 7

Dopaminergic projections included in the “want” system

Question 8

Draw out the pathway of the Papez circuit for memory. (MUST KNOW)

Answer 8

Question 9

Fill this in

Answer 9

Question 10

What are the cortical structures of the limbic system?

Answer 10

Neocortical

Paleocortical

Archicortical

Question 11

The hippocampus is sensitive to?

Answer 11

-Hippocampus is sensitive to anoxia and will show damage in the early stages of Alzheimer’s

Question 12

What is the basic anatomy of the hippocampal formation?

Answer 12

The dentate gyrus forms a C-shaped cap on the end of the hippocamus itself. Within the dentate, both the outermost molecular layer and the innermost polymorphic layer are comprised mostly of neuropil; interposed between them is the granule cell layer. The dendrites of granule cells extend into the molecular layer, where they receive excitatory input from the axons of the perforant path. The perforant path axons arise from pyramidal cells in the nearby entorhinal cortex. Axons of the dentate granule cells project into the hippocampus proper as mossy fibers. Within the hippocampus, three layers are apparent, but instead of granule cells large pyramidal cells are found in the middle layer. These pyramidal cells extend apical dendrites into the hippocampal molecular layer, where they receive two major sources of input. Mossy fiber input from the dentate gyrus synapses toward the base of apical dendrites, while perforant path axons synapse on the distal regions of pyramidal cell apical dendrites. Below the pyramidal cell layer is the polymorphic layer, which contains basal dendrites and axons of pyramidal cells.

Question 13

What is the input, output, and function of the central pathway of amygdala?

Answer 13

-Functions: autonomic responses (gut, HR, etc)

• Input: viscerosensory relay nuclei (e.g. solitary nucleus)
• Output: hypothalamus and brainstem ANS nuclei

Question 14

What types of taste use direct ionic transduction and how?

Answer 14

• For salty (Na+) and sour (H+) molecules
• Na or H binds to the receptor and directly opens ion channel

Question 15

What makes up the neocortical area?

Answer 15

-prefrontal association cortex, cingulate and subcallosal gyri

Question 16

Olfactory nerves synapse on?

Answer 16

• within the olfactory bulb on mitral cells
• Site of synapse is referred to as a “glomeruli”

Question 17

What makes up the subcortical structures?

Answer 17

-Amygdala (septal nuclei, ventral parts of BG)

Question 18

Tufted cells do what?

Answer 18

Collect information from multiple glomeruli

Question 19

Damage to th entorhinal cortex will do what?

Answer 19

-Damage to the entorhinal cortex will prevent new memories from forming, but will not affect retrieval of memories previously moved to long term storage

Question 20

What are the 5 types of taste sensations?

Answer 20

salty

sour

sweet

bitter

umami

Question 21

What is the arrangement of the olfactory epithelium?

Answer 21

• Olfactory epithelium is lined by olfactory receptors in order to receive odorant molecules
• Must be dissolved in liquid in order to be received

Question 22

Describe the central gustatory pathway

Answer 22

• CN VII, IX, X ⇒ Solitary Nucleus (Medulla) ⇒ VPM (Thalamus) ⇒ Lateral Cortex
• Taste is represented both ipsilaterally and contralaterally in the brain

Question 23

What are the diencephalic structures?

Answer 23

• Hypothalamus
• Anterior Nucleus of the Thalamus
• DM Nucleus of the Thalamus

Question 24

What is the input, output, and function of the corticomedian pathway of amygdala?

Answer 24

-Functions: sexual behavior, feeding, appetite

• Input: olfactory bulb and piriform cortex
• Output: septum and hypothalamus

Question 25

What types of taste use second messengers?

Answer 25

• For sweet, bitter, and umami molecules
• Binding of the molecule initiates a GPCR cascade eventually opening a Ca channel

Question 26

What is the role of the basal cell of the tongue in regards to taste?

Answer 26

-stem cell population capable of regenerating both taste receptors and supporting cells

Question 27

The olfactory tract is formed from?

Answer 27

-Olfactory tract is formed from the axons of mitral and tufted cells where afferent information is integrated and sent to the CNS

Question 28

Irritants go through what?

Answer 28

Irritants go through trigeminal pathways (subset of pain) not taste buds

Question 29

What makes up the paleocortical area of the limbic system?

Answer 29

-parahippocampal gyrus (entorhinal and piriform cortex)

Question 30

Olfactory bulb synapses with the piriform cortex and then does what?

Answer 30

-then synapses with DM thalamus and neocortex (orbitofrontal cortex)

-Conscious smell perception

Question 31

Olfactory bulb synapses with the amygdala and then does what?

Answer 31

-Amygdala (via lat olfactory stria), then synapses with septal nuclei & hypothalamus

-Emotional response

Question 32

What is the input, output, and function of the basolateral pathway of amygdala?

Answer 32

-Functions: reaction to sensory information, comparisons to previous memories and information, decision making and conscious response formation

• Input: neocortical sensory association cortex (temporal lobe)
• Output: orbitofrontal cortex, dorsomedial thalamus, nucleus acumbens, hypothalamus

Question 33

Output of the hippocampus goes to where?

Answer 33

-Output of the hippocampus travels to the mammillary bodies via the fornix

Question 34

Olfactory bulb synapses with the olfactory tubercle and then does what?

Answer 34

Then goes to hypothalamus