Ch. 10 M & P

Visual Transduction of the Retina

* Light passes through the lens & strikes the retina * Rods & Cones become excited & phototransduction occurs * Glutamate is released onto the bipolar cells * Signal is conducted to the ganglion cells * Optic nerve delivers signal to the brain.

Rods

* Specialized visual receptors that play a key role in night vision and peripheral vision. * Retinal receptors that detect black, white, and gray * sensitive to Photons. * group of photoreceptor cells that function best in low light.

Cones

* daylight vision and color vision. * group of photoreceptor cells that function best for color vision.

Sound transmission through the ear

->Outer ear->Tympanic membrane vibrates->Middle ear->Amplification of vibration by middle ear bones->Stapes pushes on Oval window-(generating fluid waves in the Cochlea)-> Vibration of specific region of Cochlear membrane-(dependent on souns frequency)->Inner ear->Activated sensory neurons transmit electrical signals to the brain stem via the Vestibulocochlear nerve->Round window dissipates wave energy in inner ear back to the middle ear

Which nervous system division has parasympathetic and sympathetic branches?

Autonomic division of the efferent nervous system

A layer containing an abundance of blood vessels?

Choroid * Nutrients are delivered to & waste is removed from.

Which of the following structures contains sensory receptors for hearing?

Cochlea

What type of neural circuit is represented by the sensory neurons of the retina?

Converging

The CNS must distinguish four properties of a stimulus. * These properties include location, intensity, modality, and which other property?

Duration

Which of the following would occur if you were to surgically remove the pigmented epithelium of the retina?

Entering light would be scattered across the retina and it would be difficult to obtain a sharp image.

Anatomic pathway for somatic sensations.

Fine touch, vibration, proprioception-> * 1st synapse in the medulla Ipsilateral to the stimulus,-> * 2nd synapse in thalamus, Contralateral to the stimulus,-> * 3rd synapse in Primary Somatic Sensory Cortex, Contralateral to the stimulus. 2. Pain, temperature, course touch-> *1st synapse in spinal cord, Ipsilateral to the stimulus,-> * 2nd synapse in thalamus, Contralateral to the stimulus,-> * 3rd synapse in Primary Somatic Sensory Cortex, Contralateral to the stimulus.

A receptor potential is a type of ________ potential.

Graded

Diverging circuits

In a diverging circuit, you start with a single source of stimulus. This single stimulus source will then stimulate more neurons, which may then stimulate even more neurons.

On which side of the figure is light energy converted into an electrical potential?

In this image, the receptor cells that convert light energy into electric potentials are rods. The rods are located on the right side of the image.

What is the significance of the neuronal circuit setup of the retina?

It allows for a single multipolar neuron to process the signal from hundreds of different photoreceptors.

A neuron that has responded to a stimulus causes decreased activity in neighboring neurons in which process?

Lateral inhibition

Which of the following structures focuses light for clear vision?

Lens

Which receptors are the hair cells of the ear? * Which of the following types of receptors are involved in hearing?

Mechanoreceptors

Does the retina contain fibers?

No. No elastic, collagen, or reticular fibers. * These fibers would interfere with light traveling to the photoreceptors.

A convergence of axons from the retina that leave the eye through the optic disc?

Optic nerve

What is the subjective perception that occurs when nociceptors are stimulated?

Pain

Which of the following can be mediated by nociceptors?

Pain & itch

As light travels through the _________, light waves are directed onto the ________, which is the layer responsible for ___________.

Pupil, Retina, Phototransduction.

What is the role of the photoreceptors?

Recall that a "receptor" is a structure sensitive to a particular environmental variable. The variables that the photoreceptors detect are photons and these cells are responsible for transducing this light energy into an electrical impulse.

The receptor potential is generated at the _______.

Receiving region

A pigmented layer and layers of neuronal cells that together serve for phototransduction? *deepest layer of the eye.

Retina

A layer that contains collagen fibers, forming a thick fibrous protective layer around the eye?

Sclera *white of the eye"- fibrous tunic

Which structure(s) contain(s) receptors that detect rotation of the head?

Semicircular canals

Where do all tertiary somatic sensory neurons terminate?

Somatosensory cortex

Which neurons send the signal through to the brain via the optic nerve?

The light passes through several layers of cells before reaching the photoreceptor cells. Once the light energy is converted to an electrical signal, the signal travels through various neurons to reach the ganglion cells. The axons of the ganglion cells converge to form the optic nerve, which is responsible for conducting the signals formed by the light stimuli to the brain.

Which of the following describes a depolarization?

The membrane becomes less polarized.

Amplifying signals in the eye:

The signals that the neurons of the retina send are only amplified by the intensity of the light. * The more intense the light is, the more intense the signal from the neurons of the retina. * Recall that signal intensity is encoded in the frequency of action potentials and the number of neurons involved.

Why would a drug that enhances the kidney's ability to excrete water be given to someone that suffers from Ménière's disease?

This treatment will decrease the amount of endolymph made.

Which mechanism causes hair cell depolarization as stereocilia bend in response to sound waves?

Tip links open ion channels, which causes membrane depolarization.

Which special sense would be most affected by a vitamin A deficiency?

Vision

How is the signal transduced across the retina?

What you see in this particular image is that six rods stimulate only two bipolar cells, which then stimulate only one ganglion cell.

Which of the following structures is/are found in the retina?

amacrine cells, ganglion cells, horizontal cells, bipolar cells, pigment epithelium, photoreceptors.

The receptor potential _______.

amplitude can vary with the stimulus intensity, requires the appropriate stimulus and can be graded with a stimulus intensity

What are the amacrine & horizontal cells?

both cells are Neuronal cells that aid in the signal transduction.

Photoreceptors

include 2 types- Rods & Cones. * both responsible for phototransduction.

The Fovea

is an area that contains only cones and serves as the eye's point of sharpest vision.

A layer that functions to absorb excess light

pigment epithelium

What is the Pigmented layer?

simple cuboid epithelium with the pigment melanin stored within the cells. Dark pigment absorbs excess light & prevents reflection of light back onto the photoreceptor cells, ensuring focused sharp images.

Sensory transduction is defined as _______.

the conversion of a stimulus to a change in membrane potential

Vision is especially acute in the fovea and surrounding macula. * This is due to a high density of cone cells and which other reason?

there are no blood vessels or neurons covering the cones.

Which of the following describes one of the symptoms associated with Ménière's disease and what sensory system of the body does it afflict?

vertigo; balance and equilibrium by means of the ear