UIC PSCH 262 Behavioral Neuroscience - Exam II

The Goal of the Sensory System

Physical Stimuli and Psychological Experiences

Physical Stimuli

Wavelengths of light, Sound Waves, Chemicals, and Pressure

Psychological Experiences

Smelling, seeing a painting, or holding someones hand

The Three Somatosensory Systems

Nocioception

Hapsis

Proprioception

Receptors

Refers to individual neurons that control the physical world around us into action potentials

Nocioception

Pain, temperature, itch

Hapsis

Fine touch and pressure

Proprioception

Body Awareness

How does pressure on our skin get translated to a neural signal?

The displacement of skin causes the opening of sodium channels, which leads to depolarization and then ACTION POTENTIAL

How is speed determined?

By myelin and diameter

How does diameter determine speed?

The larger the diameter of the axon, the faster the rate of action potential (A-beta is faster than C fibers that have no myelin and a small diameter)

How does myelin determine speed?

it speeds up the rate in which the AP is sent all the way down the length of the axon

How does information from the surface of the skin get to the spinal chord?

1. Starts at the skin surface which causes an AP in the receptor

2. AP is propagated all the way down to the axon

3. Travels through dorsal pathway and into the spinal chord

Bipolar Neuron

You can see the cell body, and resides in a collection of cell bodies called the DORSAL ROOT GANGLION

The Hapsis System

Responsible for touch and pressure

Topography

Orderly entry of information from dermatomes into the spinal chord

Example of Topography

When touch happens at the foot, enters the spinal chord at very low levels.

Touch to shoulder, enters at a much higher level.

Dermatomes

Large regions of skin. Who's neurons travel in the same peripheral nerve, with cell bodies in the same dorsal root ganglion and enter the spinal chord at the same level

The Thalamus

Is carved into small subregions for specialization in particular types of sensory and motor functions

From the Skin to the Brain

1. Information enters via the Dorsal-root ganglion

2. Information projects to and synapses on to cells of the dorsal column nuclei

3. Contralateral projection to ventral posterior nucleus of the. thalamus

4. primary somatosensory

How does Somatosensory get to the Thalamus?

It travels through the ventral posterior nucleus of the thalamus

Where is the primary somatosensory cortex?

Parietal Lobe

Responsibility of the somatosensory cortex?

Responsible for perceiving touch to the surface of the skin

Central Sulcus

separates frontal and parietal lobes, posterior to it is the PSC

What is the homunculus?

It is a somatosensory map

How does a somatosensory map work?

Left side process right side of body

Right side process left side of body

What are receptive Fields

Region of physical space where it is possible for a physical stimulus to alter the firing rate of the neuron being measured

Center of Receptive Field

increases firing rate

Touching the surround of the receptive field

decreases firing rate

Touching Center and Surround

cancels the responses out

touching the outside of the field

no change - not within its field

Plasticity

Brain Structures can change to better cope with the environment

Motor Cortex Axons

Axons from this do not innervate muscles directly

What do motor cortex axons do if not innervate muscles directly?

Their either directly or indirectly innervate neurons of the ventral horns of the spinal chord

Spinal Motor Neurons

Neural elements that ultimately talk to muscles and gets them to contract

Motor Unit

Single spinal motor neuron and all of the individual muscles fibers it contracts

Muscle Spindle Neurons

Status of a muscle is monitored by receptor systems

When do muscle spindle neurons increase firing rate?

when the muscle is stretched

Where are muscle spindle neurons located?

They are embeded in the muscle itself and report the length of the muscles

Wavelength determines....

Color

Amplitude determines...

Brightness

Sympathetic Activation and the Iris

Sympa. is the activation which leads to pupil dilation

Parasympathetic Activiation at the Iris

Activation of the Parasympa. leads to pupil constriction

Sensitivity (Pupil)

The larger the pupil size, the more light permitted in.

Widening the pupil increases sensitivity

Acuity (Pupil)

In bright light, the pupil constricts.

It improves acuity

Binocular Disparity

Images on the retina are 2D BUT with the image on each retina offset (BD) we construct a 3D psychological image

The Retina

is a 5-layered sense organ for vision

What is on the Back layer of the Retina

Receptors for light (rods and cones)

What is on the front layer of the Retina

Retinal Ganglion Cells

Axons travel out of the eye and to the brain

Two problems with the Retina due to neuron arrangement

1. Light is filtered and distorted on its way through the neuronal cell layers to the receptors

2. Axons of the retinal ganglion cells ultimately have to cross through the retina to make it out of the eye

Solution to light distortion

Fovea

What is the fovea and what does it help solve?

Is a specialized area of the retina with a thinning of the retinal ganglion cell layer.

High acuity (seeing things clearest when looking directly at them), this is due to the image falling on the fovea.

Solution to axons passing the retina?

completion

What is completion?

Where the visual system uses information from the receptors around the blind spot to compete broken images

Receptors for the eye

Rods and Cones

What is a Rod?

Rod-mediated vision dominates in dim light

more sensitive to light than cones

poor acuity

lack of color

What are cones?

Cone-mediated vision dominates in ample light

high acuity

color

How to stop rods from firing action potentials?

the bleaching of rhodopsin

What does stopping action potentials do?

Stopping action potentials, or the inhibition, starts a string of effects on downstream neurons that lead to excitation of retinal ganglion cells

What do retinal ganglion cells do?

They carry information out of the eye and to the brain

How do axons from the retinal ganglion cell travel?

They travel via the optic nerve

Crossing visual information

Information from the left visual world is processed by our right visual cortex and vice versa

Where can we think our retina is divided?

At the fovea!

What are the two hemiretinas?

Nasal and temporal

What does the nasal hemiretina see?

from one eye, it sees a different part of the visual world than the temporal hemiretina from the same eye

Where do nasal hemiretinas cross?

at the midline

Do temporal hemiretinas cross at the midlinee?

NO

Where and how is information from the retina projected?

It projects to the lateral geniculate nucleus which then projects to the primary visual cortex

Retinotopic map maintains...

Order of the parts of the image are maintained due to this

Where is the Retinotopic Map located?

the lateral geniculate nucleus and primary visual cortex

Visual receptive field

an area of visual space where it is possible for light to change the firing rate of a neuron

Doral Stream is where....

information flows to the posterior parietal cortex

Ventral stream is where...

information flows to the inferotemporal cortex

What is the dorsal stream important for?

for determing where the stimuli are in space

What is the ventral stream important for?

for identifying what objects are

What is the physical stimulus for audition?

Vibrations of air molecules (sine waves)

Vibrations into neural signals

sound vibrates the tympanic membrane which vibrates the ossicles which then causes the stapes or stirrup to vibrate the oval window of the cochlea

Organ of Corti

Sense organ for audition

Chock full of hairs

Organ of Corti, the receptors for sound are hair cells

how do ion channels open up in Corti?

the deflection of hair cells in one direction causes ion channels to open

Depolarization of a hair cell causes what?

neurotransmitters to be released from it onto the next neuron and causes Action Potentials to be generated

What causes corti to be stimulated?

tones of different frequencies

Tonotopic Map

regions that respond best to one particular tone are neighbored by regions that respond best to a tone of a slightly different frequency

Where is the tonotopic map preserved to?

the cortex

Which region of the thalamus processes auditory information?

the medial geniculate nucleus of the thalamus

Primary auditory cortex

located within the temporal lobe of the cortex

it is organized in columns

Sense organ of the vestibular system?

Semi-circular Canals (SCS)

Where is the Semi-circular canal (SCS) located?

Located next to the cochlea

What is the SCS important for?

Important for balance

Translates head movement into neural signals by the movement of fluid in the SCS and stimulation of hair cells

Where does information from the hair cells of SCS travel?

travels along the cranial never VIII - the auditory nerve

How is SCS information processssed?

By the brainstem as well as the cerebellum

Which system does the SCS work closely with?

works with the visual system

Top-Down Control

Higher order areas of the nervous system (e.g. the cortext) alter sensorys and motor processing in the peripheral nervous sytems