Question

Choose either the olfactory or taste system and describe its organization. What are the receptors? What nerve or nerves carry information to the CNS and where does it (or they) terminate? What areas of the thalamus and cortex are involved?

Answer 1

OLFACTORY SYSTEM

The olfactory system, or sense of smell, is the sensory system used for smelling (olfaction).

Organization-

1.Peripheral :

The peripheral olfactory system consists mainly of the nostrils, ethmoid bone, nasal cavity, and the olfactory epithelium The primary components of the layers of epithelial tissue are the mucous membranes, olfactory glands, olfactory neurons, and nerve fibers of the olfactory nerves

Odor molecules can enter the peripheral pathway and reach the nasal cavity either through the nostrils when inhaling (olfaction) or through the throat when the tongue pushes air to the back of the nasal cavity while chewing or swallowing

2.Transduction:

Olfactory sensory neurons in the epithelium detect odor molecules dissolved in the mucus and transmit information about the odor to the brain in a process called sensory transduction.[4][5] Olfactory neurons have cilia (tiny hairs) containing Olfactory receptors that bind to odor molecules, causing an electrical response that spreads through the Sensory neuron to the olfactory nerve fibers at the back of the nasal cavity.[2]

Olfactory nerves and fibers transmit information about odors from the peripheral olfactory system to the central olfactory system of the brain

3.Central:

The main olfactory bulb transmits pulses to both mitral and tufted cells, which help determine odor concentration based off the time certain neuron clusters fire.

The uncus houses the olfactory cortex which includes the piriform cortex (posterior orbitofrontal cortex), amygdala, olfactory tubercle, and parahippocampal gyrus.

The olfactory tubercle connects to numerous areas of the amygdala, thalamus, hypothalamus, hippocampus, brain stem, retina, auditory cortex, and olfactory system.The amygdala (in olfaction) processes pheromone, allomone, and kairomone signals

Stria terminalis, specifically bed nuclei (BNST), act as the information pathway between the amygdala and hypothalamus, as well as the hypothalamus and pituitary gland.

The hippocampus receives almost all of its olfactory information via the amygdala (either directly or via the BNST). The hippocampus forms new and reinforces existing memories.

OLFACTORY PATHWAY-

Olfactory Receptor Cells-Olfactory Nerve-Olfactory Bulb-Olfactory Tract-

a)Medial Olfactory Stria-Septal Nuclei-Hypothalamus Limbic System (Primitve Parts)

b)Lateral Olfactory Stria-

1)Pre pyriform Cortex ,Pyriform Cortex-Amygdala-Limbic System(Hippocambus)

2)Thalamus-Orbitofrontal cortex(Newer)

Receptors-Olfactory Receptor

Nerve-Olfactory Nerve(1st cranial Nerve)

Termination of olfactory nerve-Some branches terminate in entorhinal cortex and other regions on the undersurface of the frontal lobe.

Area of Thalamus Involved-Thalamus is bys passed in the Olfactory Pathway(The sense that does not go through the thalamus is smell.)

Area of Cortex Involved-prefrontal cortex, the primary olfactory area consists of the medial and lateral orbitofrontal cortex