test questions Flashcards
Name six ways spiral ganglion cells make up the auditory nerve and where they go.
1) the ventral cochlear nucleus and the dorsal cochlear nucleus on THE SAME SIDE (located at the level of the medulla
2) neurons in the ventral cochlear nucleus will send axons to the ipsi and the contra lateral superior olive. The auditory info is being processed ipsilaterally and contralaterally
3) The axons of the neurons in the superior olive then ascend in the lateral lemniscus ( which is just a collection of axons.
4) they will synapse in the inferior colliculus (responsible for the auditory reflexes such as turning your head when you hear a sound.
5) then heads to the thalamus in the medial geneculate nucleus
6) neurons in the MGN will send axons to the primary audiory cortex in the superior olive.
If your hear a sound in the left ear and nothing else what does this mean?
Sound is processed bilaterally however the auditory input is coming in both ears the ipsilateral pathways is being surpressed. Simultaneous sound imput to both ears suppress the ipsilateral pathways.
Explain the different pathways between getting touched and pain.
Long lasting pain is caused by c fibers. C fibers (small diameter nociceptor fibers) actually have their cell bodies in the dorsal root ganglia just like A-beta mechanoreceptor fibers. The c fibers enter the dorsal horn of the spinal cord, once they enter the spinal cord they branch out immediately. They will traval short distances up and down the spinal cord. In a region called ZONE OF LISSAUER. Then the fibers are going to synapse on a group of cells on the outer part of the dorsal horn, which is called the substsantia gelatinosa. PAIN INFORMATION WILL CROSS OVER AT THE POINT OF ENTRY IN THE SPINAL CORD.
Touch information will cross over at the brainsteam.
the neurotransmitter used here are amino acid (glutamate) and peptide neurotransmitter (substance P)
Are the ascending Spinothalamic pain pathway dorsal lemniscal pathway synapsing on the same neurons?
The spinothalamic fibers that make up the spinothalamic tracts are a little different than what we see in the dorsal lemniscal pathway because they synapse over a very wide area of the thalamus. The dorsal medial lemiscal pathway synapse at a very particular part of the thalamus, not this pathway. The axons of this tract when they reach the thalamus have a very wide spread connection inside the thalamus. Some of these fibers will terminate in the ventral posterior nucleus of the thalamus (VPN). The medial lemiscal portion of touch pathway terminates here as well. THEY DO NOT SYNAPSE ON THE SAME NEURONS. They synapse on the same nuclei but the pathways synapse in different regions of he thalamus, they remain separate. The other axons that make up the spinothalamic tract terminate in the interlaminar region of the thalamus.
Explain Thermoreceptors.
The rate of chemical reactions that take place in your body depends on the body temperature. NEURONS SENSITIVE TO TEMPERATURE. Very specific membrane mechanisms. It is actually the thermoreceptors in your skin that contributes to the perception of temperature. You have spots on your body that are sensative to hot or cold but no both. These spots are about 1mm in diameter. Seperate receptors to encode them.
Explain why different areas of your body are sensitive to different temperatures.
Each of these different type of thermorecptive neurons express just one type of channel. There are 6 distinct TPR channels in the thermoreceptorse. Each of these channels has different temperature sensitivities.
Trpm8 is sensitive to NONpainful decreases in temperature dips below 25 celsius.
Trpv1 is sensitive to PAINFUL! increase of temperature above 43 celcius. The exception is that some cold recptor also express trpv 1 channels which means that these cold recptors are also sensitive to increase in temperature of 43 celsius or more.
Adaptation of thermoreceptors
they apapt. Body temperature is 38 celsius. When the temperature drops it will cause your cold receptors to start firing away. At the same time, the warm recptors will be silent. After a few seconds at 32 celsius, your cold recptors start to slow down, and then your warm receptors start to fire. Ex. of november with a coat.
TO TAKE AWAY: The firing rate of warm and cold recptors are greatest during and shortly after temperature changes.
What are the three characteristic of electromagnetic radiation? What is electromagnetic radiation?
WAVELENGTH: Distance between two peaks of waves.
FREQUENCY: number of waves per seconds measured in hertz (Hz)
AMPLITUDE: Size of the waves
High frequencies: very short wavelengths (more waves/seconds) highest energy content
Low frequencies: fewer waves per second, long waves, lenghts, lowest energy content.
What happens when stereolcilia bend? In auditory
A sequence of events results in the release of neurotransmitter.
1) Arrival of pressure wave bends stereocilia.
2) Potassium channels open in response to bending
3) Membrane depolarizes due to influx of K
4) Depolarization triggers inflow of calcium ions
5) CA2+ causes synaptic vesicles to fuse with plasma membrane
6) Neurotransmitter is released and diffuses to afferent neuron.
draw a picture
What neurotransmitter comes in for auditory transduction and why?
Potassium flows in
1) Concentration gradient ( more k+ outside than inside) FORCE DIFFUSION
2) Electrostatic force (inside negative and outside is positive)
How do we recognize sound?
Frequency and localization
1) Interaural time: sound is going to hit one ear before another, the difference is compared at the level of the medulla at the MEDIAL superior olivary nuclei.
2) Sound intensity: The intensity of the sound wave diminishes over time, the distance it has to traval. The magnitude of the sound wave in one ear will be stronger because it has less distance to traval. In terms of intensity it is LATERAL superior olivary nuclei.
What it takes to recognize sounds?
1) The speed at which the sounds are presented
2) the frequency of the sounds (high or low pitch)
Tonotopic maps of the primary auditory cortex
The cells in the ANTERIOR portion responds to lower frequency sounds and the POSTERIOR responds to higher frequency sounds.
Where do we perceive speech and sound?
Left temporal lobe
What is auditory agnosia? Non-verbal agnosia?
Can read and speak normally but cannot recognize words. Recognizing a sound is not the same as comprehending it. Recognition is a perceptual task. Damage to wernicke posterior portion of BA 22. Non-verbal auditory agnosia is when you cant hear sounds ( cat, dogs, siren) can recognize verbal sounds. Damage is not only left temporal lobe but also bilateral interior portions of BA 22.
