• A perceptual dimension of sound that is determined by/ corresponds with the frequency of vibration.

• Measured in Hertz

• A perceptual dimension of sound that corresponds with intensity

ex: more vigorous vibrations produce more intense sound waves

• Consists of the Pinna (external ear) and the Auditory Canal

• Sound is funneled via the Pinna through the ear canal to the tympanic membrane (eardrum).

• Consists of Tympanic Membrane and Ossicles

• Bones in the Middle ear (3).

1. Malleus
2. Incus
3. Stapes

• Set into vibration by the eardrum

Pinna --> Auditory canal --> Tympanic membrane --> Ossicles --> Oval window --> Cochlea

• Structure of the inner ear that contains the auditory transducing mechanisms.

• Consists of 3 fluid filled canals

1. Cochlear Duct - Endolymph
2. Tympanic Canal - Perilymph
3. Vestibular Canal - Perilymph

• Sensory Receptive organ

• Located in the cochlea on the basilar membrane

• Consists of basilar membrane, hair cells, and tectorial membrane

• A membrane in the cochlea of the inner ear

• Contains the Organ of Corti

• Different frequencies of sound vibrations cause different portions of the membrane to flex (place coding)

-  Base  (Top) :  High  Frequency

- Apex (End/Tip): Low Frequency

• The receptor cells of the auditory apparatus.

• Contains cilia.

• Two types of receptor cells:

1.  Inner Ear:  Responsible for Transduction.

2. Outter Ear: Responsible for Signal Amplification

• A membrane located above the basilar membrane
• Cilia of the auditory hair cells move back and forth against this
• Sound waves cause it to flex up and down

• One of the groups of nuclei in the medulla that receive auditory info from the cochlea

• A group of nuclei in the medulla invloved with auditory functions such as localization of the source of sounds.

1. Cochlea
2. Pons
3. Brainstem
4. Superior Olivary Nucleus
5. Cochlear Nucleus
6. Inferrior Colliculus
7. Medial Geniculate Nucleus
8. Auditory Cortex

• Conduction: usually involves a middle ear problem that blocks sound vibrations from reaching the inner ear.
• Sensorineural: A problem with the structures - especially the cochlea- that convert sound vibrations into neural activity and project to the brain.
• Central: Damage to auditory brain structures that can affect hearing in various ways.

• Used for Sersorineural Deafness

• Uses electrodes to stimulate the basilar membrane.

• Perceives Pitch (frequency).

- Place Encoding

• The tissue of the nasal sinus that covers the cribform plate.

• Consists of receptor cells, supporting cells, basal cells, and cilia.

• Responsible for transduction
• Has only one dendrite
• Unmylinated axon

*Axon located in the cribform plate

*Is the axon for Olfactory nerve

• Regenerates every 1-8 weeks 

• Responsible for producing mucus.

• Contains enzymes that destroy odorant molecules, and this protects receptor cells.

• Replacement receptor cells.

• Replacement receptor cells.

• Receives input from olfactory receptors
• At the end of the olfactory tract

• A neuron located in the olfactory bulb that receives info from olfactory receptors
• Its axons bring info to the rest of the brain

• A bundel of dendrites of mitral cells
• The associated terminal buttons of the axons of olfactory receptors

Steps

1. Sensory Receptors
2. Olfactory Bulb
3. Olfactory Cortex
4. Thalamus & Limbic System
5. Frontal Cortex
6. Thalamus & Limbic System
7. Olfactory Cortex
8. Olfactory Bulb

• Receptors of taste

           ~~ One taste per bud

• Multiple taste cells inside

• Taste cells

~Gustatory Afferent Axons

• Cranial Nerves (CN)

~ CN 9 - Glossopharyngeal

~ CN 7    -   Facial  Nerve

~ CN 10    -   Vagus Nerve

• Pathway is ipsilateral (left to left; right to right)
• Pathway is Insular (consistant; the same path each time; a taste activates the same area of the brain everry time)

• Occurs when an animal associates the taste of a certain food with symptoms caused by a toxic, spoiled, or poisonous substance
• Generally is developed after ingestion of food that causes nausea, sickness, or vomiting.

• Epidermis (outside)
• Dermis (inside)

Types

• Glabrous (hairless skin)
• Hairy skin

• A (touch) sensory neuron that responds to mechanical stimuli
• Stimuli that cause vibration in the skin or changes in pressure against it are detected by these

~movement causes transduction which opens ion channels

Types: free nerve endings, Merkel's disks, Meissner's corpuscle, Pacinian corpuscle, Hair follicle receptor

• A touch receptor (light pressure)
• Important for detection of form, edges, and roughness, especially by fingertips

• A touch receptor (pressure)
• Important in detecting stretching or static force against the skin
• Important in proprioception

• A touch receptor (tap and flutter)
• Important in detecting texture or edge contours, especially by fingertips

• A vibration sensitive touch receptor
• Important in detecting vibration from an object being held

• Alpha fibers
• Proprioceptors (sensory receptor) of the skeletal muscle
• Fastest conduction velocity

• Beta fiber axons
• Mechanoreceptors of the skin
• 2nd fastest conduction velocity

• Delta fiber axons
• Pain and temperature sensory receptors
• 3rd fastest conduction velocity (next to last)

• C fiber axons
• Unmylinated
• Itch, Temperature, and pain sensory receptors
• Slowest conduction velocity

Rapidly Adapts to Stimuli

• Meissner's Corpuscles
• Pacinian Corpuscles

Slowly Adapts to Stimuli

• Ruffini Endings
• Merkel's Disks

• Two-point discrimination depends on activating two separate populations of neurons.
• In order to discriminate two closely placed points, the receptive fields of the neurons must be small.
• This in turn means that the receptors must be densely packed in a sensitive area, so that two points very close together activate different receptors.

1. Touch receptors detect stimululation on the skin and send action potentials along axons that enter the dorsal spinal cord.
2. After entering the spinal cord dorsal horn, the axon joins the dorsal column of white matter and ascends to the brain
3. In the medulla, the axon makes its 1st synapse with a medullary neuron that sends its axon across the midline to the thalamus
4. The thalamus receives its info contralaterally and sends it to the ipsilateral somatosensory cortex

1. Sensory neurons, called nociceptors, are activated by stimuli that causes tissue damage.
2. Injured cells release substances that stimulate nerve endings and cause local inflammation (histamine).
3. Info enters the dorsal root and synapses on dorsal horn neurons
4. Pain fibers, Aδ and C, release glutamate and substance P in the spinal cord. Then dorsal horn cells send info across the midline to the thalamus.

1. Spinal Cord
2. Medulla
3. Pons
4. Midbrain
5. Forebrain
6. Thalamus
7. Somatosensory Cortex

• The action of nerve fibers crossing over to opposite sides of the nervous system (left to right; right to left).

• Touch: Crosses over in the hindbrain.
• Pain: Crosses over in the spinal cord.

• A partial spinal cord lesion; damage to one side of the spinal cord (left or right).
• Loss of motor function, vibration, position, and deep touch on the side with cord damage.
• Loss of pain, temperature, and light touch on opposite side.