Exam 2 week 6 ppt 1 CN 1,2 Flashcards
How many pairs of CNs are there?
12
What types of functions can CN have? (3-4)
- ~motor
- ~somatosensory
- ~special sensor
- ~automatic components
(*CNs can have a single function or multiple functions)
Cranial nerve nuclei are located (except for 2- which two) *also, Sensory nuclei is more (medial or lateral) and motor is more (medial or lateral)
- Located in the dorsal brainstem (except for CN I and CN II)
- Sensory is lateral
- Motor is medial
What type of function does the olfacotry nerve have?
•Special sensory – sense of smell
What makes the olfactory nerve unique among CNs? (3)
•- It does NOT
- –Synapse in thalamus before reaching cerebral cortex
- –Enter or leave the brainstem directly
- –Have a typical sensory ganglion
- Dr. Lake confirmed that olfactory does NOT have a typcial sensory ganglion, regardless of what he said in the narration. [The powerpoint slide and book says NO typical sensory ganglion, but the text under the slide says it DOES (but this looks added by Dr. Lake maybe by accident?] - Dr. Lake said it DOES in the audio too)
CN number for olfactory nerve:
I
name of cranial nerve I:
olfactory nerve
four steps in the initial portion of the primary pathway that starts with Olfactory mucosa:
- The surface of the olfactory mucosa is covered in mucus
- Sensory cells (bipolar) are imbedded in the mucus
- Axons from the sensory neurons collectively form the olfactory nerve & penetrate the cribriform plate of ethmoid bone
- The axons end on the mitral cells of the olfactory bulb
The receptor surface is the Olfactory mucosa which is Mucus covered. Sensory cells imbedded in mucus. Axons from these sensory cells collectively form olfactory nerve & each penetrates the cribriform plate of ethmoid bone. These axons End on mitral cells of olfactory bulb
Olfactory receptor cells:
how many?
4 things about them
about 40 million olfactory receptor cells in th enasal mucosa
- has ciliated dendrites imbedded in olfactory mucosa
- –Olfactory receptors are G-protein linked
- –Each receptor cell contains only single type of olfactory receptor
- There are many cells with same type
There are about 40 million Olfactory receptor cells in the nasal mucosa. Each receptor cell has Ciliated dendrites imbedded in olfactory mucosa. Olfactory receptors located on the membranes of the cilia have been classified as a complex type of ligand-gated metabotropic channels, that is Olfactory receptors are G-protein linked. Each receptor cell contains only single type of olfactory receptor. Many cells with same type
Olfactory G-protein receptor cells:
receptor activation
- G-protein activates adenylate cyclase and cAMP production
- cAMP 0pens ion channels in the cell membrane, resulting in Na+ & Ca++ influx & Cl- efflux
- This causes depolarization- AP generation
Olfactory Receptor activation produces G-protein activation of adenylate cyclase and cyclic AMP production. The cyclic AMP Opens ion channels in the cell membrane, resulting in Na+ & Ca++ influx & Cl- efflux – the resulting influx of positive ions and efflux of negative ions produces a Depolarization and action potential generation
How many genes code for olfactory receptors?
It is interesting to note that about 1,000 genes code for olfactory receptors – largest gene complex for any single purpose.
Mitral cells
what are they?
what do they form?
where do they end?
–Bipolar neurons within the olfactory bulb
–Axons form the olfactory tract
–Olfactory tract axons end primarily in primary olfactory cortex of medial temporal lobe – pyriform area
Mitral cells are Bipolar neurons within the olfactory bulb and represents the relay ganglion of the olfactory system. Their Axons form the olfactory tract. Olfactory tract axons end primarily in primary olfactory cortex of medial temporal lobe – pyriform area
what is the pyriform area?
primary olfactory cortex of medial temporal lobe – pyriform area
. where the axons of the mitral cells primarily end
where is the primary olfactory cortex located?
what is an alternate name for it?
Primary olfactory cortex is located in the medial temporal lobe – pyriform area.
The pyriform cortex is composed of the:
- Periamygdaloid cortex
- Anterior portion of parahippocampal gyrus
Pyriform cortex is also called the entorhinal area (maybe or maybe it is only the anterior portion of the parahippocalmpal gyrus)
not sure which part the entorhinal cortex is
Book Said: Primary olfactory cortex consists of
- pyriform area - (it is found in anterior part of medial temporal lobe)
- cerebral cortex overlying the amygdala (also called periamygdaloid cortex)
- a restricted area of anterior parahipocampal gyrus (also called entorhinal area)
(in that case it doesn’t have an alternate name as the pyriform area is a seperate part of the primary olfactory cortex)
*I have submitted a question about this to Dr. Lake on the message board and will update the card when we get a response*
His response: “Genreally the term pyriform cortex refers to the periamygdaloid and parahippocampal corticies and entorhinal cortex refers to the area rostral ot the parahippocampal gyrus (ie periamygdaloid). Again an unfortunate mulitple use of terms for the same areas”
Still totally confused about entorhinal. I guess I will just take the hit on the exam for this one.
What is the pyriform cortex composed of?
The pyriform cortex is composed of the:
- Periamygdaloid cortex
- Anterior portion of parahippocampal gyrus ()
it is the primary olfactory cortex and locaed in the medial temporal lobe
There are olfactory tract projections to the following 6 cortical areas:
- Hypothalamus
- Orbitofrontal cortex
- Amygdala
- Hippocampus - (strong memories with odors)
- dorsomedial nucleus of thalamus (not shown)
- Limbic structures - (strong emotional reactions to odors)
what does olfactory projections to the hippocampus do?
Hippocampus – strong memories with odors
