Week 9 - Chapter 17 Special Senses
Olfactory sensory neurons (bipolar neurons) are responsible for:
Olfaction (sense of smell)
Olfactory sensory neurons are located:
In the nasal epithelium
What do olfactory glands do?
Produce mucus that dissolves odorants
What is triggered in the olfactory receptors when an odor is detected?
A receptor potential, which triggers nerve impulses
The threshold for smell is _____
Low, adaption to odors occurs quickly
What do the axons of olfactory sensory neurons form?
The olfactory (l) nerves
Where do the olfactory nerve signals travel to?
Olfactory bulbs, olfactory tracts, limbic system, and olfactory cortex in the temporal lobe
Where are gustatory receptors located?
Taste buds
What are dissolved chemicals that stimulate taste receptors called?
Tastants
How do tastants stimulate gustatory receptor cells?
By flowing through ion channels or binding to receptors attached to G proteins
What nerves carry taste signals to the brain?
Facial (VII), glossopharyngeal (IX), and vagus (X) nerves
Where do taste signals go after being transmitted by the nerves?
To the medulla oblongata, thalamus, and gustatory cortex in the parietal lobe
After receptor potentials are developed in gustatory cells, what occurs?
The release of a neurotransmitter, generating nerve impulses in sensory neurons
Where are most sensory receptors located in the human body?
In the eyes
What type of light do the eyes detect?
Visible light (wavelengths between 400 and 700 nm)
What are the accessory structures of the eyes?
Eyebrows, eyelids, eyelashes, lacrimal apparatus, and extraocular muscles
What is the function of the lacrimal apparatus?
It produces and drains tears.
What are the three layers of the eye?
Fibrous layer (sclera and cornea), vascular layer (choroid, ciliary body, and iris), inner layer (retina)
What are the two layers of the retina?
Pigmented layer and neural layer
What fluids are found in the anterior and posterior segments of the eye?
Aqueous humor (anterior segment) and vitreous humor (posterior segment)
How is an image formed on the retina?
Light is refracted by the cornea and lens, forming an inverted image on the fovea centralis.
What happens to the lens and pupil when focusing on close objects?
The lens becomes more curved (accommodation) and the pupil constricts.
What is the near point of vision?
The closest distance at which an object can be clearly focused with maximum accommodation
What happens in convergence?
The eyeballs move medially to focus on an object
What is the first step in vision?
Absorption of light by photopigments in rods and cones
What do horizontal cells do in vision?
They transmit inhibitory signals between photoreceptors and bipolar cells
How do nerve impulses travel from the retina to the brain?
From ganglion cells through the optic nerve, optic chiasm, optic tract, thalamus, and visual cortex in the occipital lobe
The parts of the external ear:
Auricle, external acoustic meatus, and tympanic membrane
Parts of the middle ear:
Tympanic cavity, auditory tube, ossicles, vestibular window, and cochlear window
Parts of the inner ear:
Bony labyrinth, membranous labyrinth, spiral organ (hearing), and vestibular system (balance)
How do sound waves travel through the ear?
- They enter the external ear
- Strike the tympanic membrane
- Pass through ossicles,
- Vibrate the vestibular window, setting up waves in perilymph and endolymph, which stimulate hair cells
How do hair cells in the inner ear detect sound?
They convert mechanical vibrations into a receptor potential, releasing neurotransmitter to initiate nerve impulses
Where do auditory signals travel after the cochlear nerve?
To the medulla oblongata, inferior colliculus, thalamus, and primary auditory cortex in the temporal lobe
What do the maculae in the utricle and saccule detect?
Linear acceleration, deceleration, and head tilt
What do the cristae in the semicircular ducts detect?
Rotational acceleration and deceleration
Where do most vestibular axons terminate in the brain?
In the medulla, pons, and cerebellum
What are some common age-related changes in the eyes?
Presbyopia, cataracts, difficulty adjusting to light, macular disease, glaucoma, dry eyes, and decreased sharpness of vision
When do the eyes begin developing during pregnancy?
About 22 days after fertilization from the ectoderm of the forebrain
When do the ears begin developing during pregnancy?
About 22 days after fertilization from the ectoderm of the hindbrain