Neuroscience Chapter 7: Non visual Sensation and Perception

Know the links between frequency, amplitude/intensity, pitch, and loudness. Which are physical modalities and which are psychological? What are the units of measurement?

Amplitude: height of wavelength (m) - High Amplitude waves are perceived as loud sounds - Low amplitude waves are perceived as soft sounds Frequency: number of cycles per minute (Hz) - Low frequency waves - low pitched sounds - High frequency waves - high pitched sounds Intensity: measured in decibles - Louder sounds = higher intensities Physical - wavelengths - a physical outcome from the movement of objects and molecules Psychological - Perception of sounds

Describe how the bending of hair cells inside the cochlea leads to action potentials.

Bending causes pore-like channels (na channels) to induce depolarization, which are at the tips of the stereo cilia, to open up. When that happens, chemicals rush into the cells, creating an electrical signal, that is eventually sent to the brain and perceived as sound

Be able to distinguish between the characteristics and location of glabrous skin vs. hairy skin. Why is the difference in sensitivity of the skin types evolutionarily advantageous?

Glabrous skin doesn't have as many nerve endings, as hairy skin cells. Hairy skin cells are more sensitive to stimuli. This helps you detect if something small is crawling on your skin. For the hair less cells,

How do the functions of outer hair cells and inner hair cells differ? How do each contribute to the process of hearing?

Inner Hair Cells: They are actual auditory receptors. They are located near the connection between the tectorial membrane and the cochlear duct. They sharpen sound. Outer Hairs Cells Also auditory receptor cells. They are locates near the organ of Corti and they amplify sound.

What are the names of the three small bones in the ear and what are they used for?

They are the Incus, Malus, Stapes (ossicles). They are used for transferring sound energy from the outside air to the fluid in the inner ear without losing too much of it.

What is the ear drum's technical name?

Tympanic Membrane.

What is a homunculus and how does this map on to somatosensory cortex?

Its that ugly man model that shows you what areas of the body that are bigger in the somatosensory cortex.

What endogenous compounds triggers the perception of pain in our body? What is the term given for our bodily reaction to pain that stimulates the free nerve endings?

- Lactic Acid Chemicals - we perceive soreness after a rough workout - Vanilloids, a group that includes capsaicin. Capsaicin is best known as the ingredient found in hot peppers, and it is responsible for the heat sensations we enjoy while eating spicy foods. - Chemicals released when a cell is damaged, such as potassium ions, enzymes, histamine, and adenosine triphosphate (ATP), also stimulate nociceptor activity. - nociceptors. A free nerve ending that responds to painful stimuli.

What are dermatomes, and how are they organized and identified?

- They are areas of the skin innervated by the dorsal roots of one spinal nerve. The flow of sensory info enter the spinal cord via spinal nerves (or brain via cranial nerves), thalamus, Somatosensory cortex, information crosses over from one side of the body to the opposite side of the brain.

What is the range of human hearing?

0-160 db 0 - threshold of hearing 160 - Eardrum bust

Hearing can be disrupted and damaged in many ways; what are some of the methods of hearing loss that we discussed in class, and how do you fix each of these?

1. Age Relate Hearing Loss - poor circulation to the inner; exposure to loud noise 2. Damage to the outer or inner ear - conduction loss due to wax build up , infection and otosclerosis. Tx = hearing aids or antibiotics 3. Damage to inner ear, auditory pathways, or auditory cortex Tx = cochlear implants

Know all of the characteristics of the 4 axon types that convey somatosensory information. Specifically, know the receptors that these axons serve, how quickly those axons convey sensory information, and why the relative size of the axons changes the speed of the neurotransmission.

1. Alpha -Alpha Fibers - they carry they are the largest and fastest fibers that carry information to the muscles 2. The second-largest set, the Aβ (alpha-beta) class, carries information from the Meissner's corpuscles, Merkel's disks, Pacinian corpuscles, and Ruffini's endings toward the central nervous system (CNS). 3. and 4. The smallest two groups, the myelinated Aδ (alpha-delta) fibers and the unmyelinated C fibers, carry information from the free nerve endings regarding pain and skin temperature.

Be very, very familiar with the auditory pathways in the brain from cochlea to cortex. Know what each nucleus in this pathway does when processing auditory information.

1. Hair cell 2. Spiral Ganglion Neuron - bipolar neuron found in the inner ear whose axons form the auditory nerve. Its a bipolar cell, whose cell body is located near the cochlea and the fibers make contact with hair cells while the other fibers make contact with the dorsal and ventral cochlear nuclei of the medulla. 3. Superior Olive - found in the pons (from the ventral cochlear nucleus). then to the lateral lemniscus with the inferior colliculus 4. Medial Geniculate Nucleus - in the thalamas and sends auditory info to higher brain (auditory cortex) 5. Auditory Cortex - processes auditory info and allows us to perceive sound sensations

What are the basic steps in somatosensory/touch processing, from mechanoreceptors to parietal lobe? What function does each of the structures involved do?

1. Mechanoreceptor - a sensory receptor that detects touch. 2. Dorsal root ganglion (column) - found in the spinal cord and is responsible for sending up sensory information to the brain. 3. dorsal root column nuclei - found in the medulla, and sends it up to higher brain organs.Axons from the dorsal column nuclei form a large band of white matter known as the medial lemniscus, which crosses the midline of the medulla. 4. Ventral posterior nucleus - found in the thalamus 5. Parietal lobe - Axons from the VP nucleus travel to the primary somatosensory cortex of the parietal lobe.

What are the 4 types of somatosenses that we discussed in class? What function do each of these senses serve in regard to providing information about the body?

1. Proprioception ( body position and movement) 2. Interoceptive (internal organ sensations) 3. Vestibular System (head position, movement, and balance) 4. Skin Senses (conditions at body surfaces)

Know where sound wave stimuli are converted in the ear, and the stages of conduction.

1. Sound waves enter the outer ear and travel through a narrow passageway called the ear canal, which leads to the eardrum. 2. The eardrum vibrates from the incoming sound waves and sends these vibrations to three tiny bones in the middle ear. These bones are called the malleus, incus, and stapes. The bones in the middle ear amplify, or increase, the sound vibrations and send them to the cochlea, a snail-shaped structure filled with fluid, in the inner ear. An elastic partition runs from the beginning to the end of the cochlea, splitting it into an upper and lower part. This partition is called the basilar membrane because it serves as the base, or ground floor, on which key hearing structures sit. 3. Once the vibrations cause the fluid inside the cochlea to ripple, a traveling wave forms along the basilar membrane. Hair cells—sensory cells sitting on top of the basilar membrane—ride the wave. Hair cells near the wide end of the snail-shaped cochlea detect higher-pitched sounds, such as an infant crying. Those closer to the center detect lower-pitched sounds, such as a large dog barking. 4. As the hair cells move up and down, microscopic hair-like projections (known as stereocilia) that perch on top of the hair cells bump against an overlying structure and bend. 5. Bending causes pore-like channels, which are at the tips of the stereocilia, to open up. When that happens, chemicals rush into the cells, creating an electrical signal. 6. The auditory nerve carries this electrical signal to the brain, which turns it into a sound that we recognize and understand.

Know the difference between A-delta fibers and C fibers; what do they look like and what do they do? What types of pain are associated with each?

A delta fibers - thicker in diameter and contains myelin fiber. Transmits immediate localized sharp pains. The C fiber is unmyelinated and therefor much slower than the A delta fibers. Transmits slow, dull and aching pains

Be able to name and fully discuss the 6 types of receptors found in your skin.

Merkel's Disk Receptor - Detects Touch Pacinian Receptor - Detects Pressure Messiner's Receptor - Detects Vibration Ruffini's Receptor- Detects heat Free Nerve Ending - Detects pain Hair follicle Receptor - Detects light touch

How is the Basilar membrane organized to reflect the sensitivity to different frequencies? How is this similar to the organization of the auditory cortex?

The Basilar Membrane base has a more thick and narrow/stiff opening (this is where you can hear high frequency pitches. At the end or the apex, it begins to open wider and is more flexible. This allows us to perceive lower frequency sounds. Neurons responding to lower frequencies are located in the rostral portions of the auditory cortex. Those responding to higher frequencies are located in the more caudal positions

What is the name for the outer, visible portion of the ear?

The Pinnia.

What structures of the inner ear are responsible for balance and knowing where your head is in space? Know what a utricle, saccule, cupula, and otoliths are. How do each of these function to send vestibular information to the brain?

The Semicircular Canals. Utricle - One of the structures making up the otolith organs. Contains hair cells. Saccule - one of the structures making up the otolith organs. contains hair cells. Cupula - Otoliths - A stone from calcium carbonate that is attached to hair cells in the otolith organs Both the saccule and utricle contain hair cells covered by gelatinous material(endolymph) with otoliths present. So when the head tilts, force is exerted on the cilia in the hair cells, which in turn modify signaling to the auditory nerve.

Which lobe of the brain is responsible for perception of auditory information?

The Temporal Lobe.

Know the pathway of auditory processing throughout the brain.

The action potentials from the stereocillia send action potentials to the dorsal or ventral cochlear nucleus superior olive then to the inferior colliculus, then to the medial geniculate nucleus of the thalamus, to the auditory cortex.

How do the tectorial and basilar membranes aid the hearing process? Be able to fully

The bottom of the hair cells are attached to the basilar membrane, and the stereocilia are in contact with the tectorial membrane. Inside the cochlea, sound waves cause the basilar membrane to vibrate up and down. This creates a shearing force between the basilar membrane and the tectorial membrane, causing the hair cell stereocilia to bend back and forth. This leads to internal changes within the hair cells that creates electrical signals.

When localizing sounds in our environment, which sound orientations are easiest to discern? Which orientations are harder? What is a sound shadow, and what effect does this have on our ability to localize sounds around us?

When we are facing the sound stimulus. It gets harder when the sound stimulus is on one side of the ear and not the other. Sound Shadow - An acoustic shadow or sound shadow is an area through which sound waves fail to propagate, due to topographical obstructions or disruption of the waves via phenomena such as wind currents, buildings, or sound barriers. So we get a quieter signal to the ear thats not facing the sound stimulus.

Know that hair cells fire at the same frequency as sound waves, and how that is done.

location.