Editing 20110105 Lecture 4 notes.txt
From Iusmphysiology
Warning: You are not logged in.
Your IP address will be recorded in this page's edit history.
The edit can be undone.
Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.
Current revision | Your text | ||
Line 127: | Line 127: | ||
*Cones express three other types of opsins that absorb: 419nm (blue), 533nm (green), 564nm (long, yellow / red). | *Cones express three other types of opsins that absorb: 419nm (blue), 533nm (green), 564nm (long, yellow / red). | ||
- | ===Gustation (the sensation of tasting)=== | + | ===Gustation (the sensation of tasting )=== |
*Innervated by facial (CN7), glossopharyngeal nerve (CN9). | *Innervated by facial (CN7), glossopharyngeal nerve (CN9). | ||
**These innervate diferent parts of the tongue. | **These innervate diferent parts of the tongue. | ||
Line 136: | Line 136: | ||
***Transformed epithelial cells, not neuronal cells. | ***Transformed epithelial cells, not neuronal cells. | ||
***Form electrical and chemical synapses. | ***Form electrical and chemical synapses. | ||
- | ***Not all | + | ***Not all form chemical synapses but if they dont' they will have electrical synapses with other receptor cells that do have chemical synapses |
**Supporting cells | **Supporting cells | ||
Line 143: | Line 143: | ||
**Bitter is associated with toxins. | **Bitter is associated with toxins. | ||
**The mechanism is different for each "taste". | **The mechanism is different for each "taste". | ||
- | |||
*Salty comes from activity of epithelium sodium channels: | *Salty comes from activity of epithelium sodium channels: | ||
**Highly expressed in kidney, too, so we know lots about them. | **Highly expressed in kidney, too, so we know lots about them. | ||
- | *** | + | ***IMportant for na reabsorption and water retention. |
**Has three subunits. | **Has three subunits. | ||
- | **Protein is | + | **Protein is constinutively active: always open, allowing Na into the taste cell to cause depolarization. |
- | **Depolarization causes activation of voltage gated | + | **Depolarization causes activation of voltage gated cA channels, then AP, then release of serotonin in synaptic cleft of facial nerve. |
- | + | ||
*Bitter test | *Bitter test | ||
- | ** | + | **detects Acids |
- | + | **Protien senstivie channels | |
- | + | **mechanism is the same: Na permeability, Ca channels open, Ca influx, AP, release of serotonin | |
- | ** | + | |
- | + | ||
*Sweet and Umani and some bitter: | *Sweet and Umani and some bitter: | ||
- | **Occurs through T1 / T2 (for sweet), T1 / R3 (Umani), T2 (bitter) | + | **Occurs through T1 / T2 (for sweet), T1 / R3 (Umani), T2 (bitter). |
- | **These are g-protein | + | **These are through g-protein which activate Phosphorlipase C which cleaves PIP2 to form DAG and IP3. |
***IP3 causes IP3R on the ER to release Ca+. | ***IP3 causes IP3R on the ER to release Ca+. | ||
***DAG cuases opening of Ca+ channels on the outer membrane (TRPM5) to augment Ca influx. | ***DAG cuases opening of Ca+ channels on the outer membrane (TRPM5) to augment Ca influx. | ||
****This channel has similar structure to the others we've seen. | ****This channel has similar structure to the others we've seen. | ||
**Influx of Ca+ causes an AP. | **Influx of Ca+ causes an AP. | ||
- | + | *All these receptors are expressed on all receptors (we think) but it isn't totally clear the distribution and differentiation mechanisms. | |
- | *All these receptors are expressed on all receptors (we think) but it isn't totally clear the distribution and | + | *Type II taste cells don't express any voltage-gated Ca channels so they may not detect...? |
- | + | ||
===Hearing=== | ===Hearing=== | ||
*The cochlea is important for sound sensing. | *The cochlea is important for sound sensing. | ||
- | * | + | *Our low is 20 kHz and high is 200 hz. |
- | + | **The cochlea is importnat for low and the helic? is for high. | |
- | **The | + | *There is a narrow membrane at the base but narrow at the apex (helic?). |
- | *There is a narrow membrane at the base but narrow at the apex ( | + | What? Something about the two membranes being opposite... |
- | + | *Place coding is the specific area of th emembrane that vibrates given the frequency of a sound wave. | |
- | *Place coding is the specific area of | + | |
*There are three important parts: | *There are three important parts: | ||
- | **The | + | **The scalar media contains endolymnph which is rich in K+ (125 miliMolar). This causes a very high positive potential inside because marginal cells move K+ into that area. |
**The high levels of K+ make the potential positive for cells in scalar media. | **The high levels of K+ make the potential positive for cells in scalar media. | ||
- | **Didn't talk about other two areas | + | **Didn't talk about other two areas. |
===Organ of corti=== | ===Organ of corti=== | ||
*There is a basalar membrane which helps determine the coding of place. | *There is a basalar membrane which helps determine the coding of place. | ||
*There are two types of hair cells: | *There are two types of hair cells: | ||
- | **Outer hair cells | + | **Outer hair cells |
***Insures fine tuning of inner hair cell sensitivity. | ***Insures fine tuning of inner hair cell sensitivity. | ||
- | ***Contain | + | ***Contain prestin which is able to contract when depolarized. |
- | ***When | + | ***When depolarziaed, the outer cells contract and the change of physiologicl location fine tunes the inner hair cells. |
- | ** | + | **inner hair cells |
***Important for hearing sound. | ***Important for hearing sound. | ||
- | *The rate of AP in cochlea is proportional to the sound amplitude. | + | *The rate of AP in cochlea is proportional to the sound amplitude. This is called '''rate coding'''. |
- | + | ||
===Mechanotransduction in the hair cells of the inner ear=== | ===Mechanotransduction in the hair cells of the inner ear=== | ||
Line 197: | Line 190: | ||
**This makes sense because the tectorial membrane pushes the villi toward the hair cells and cuases opening of some channel. | **This makes sense because the tectorial membrane pushes the villi toward the hair cells and cuases opening of some channel. | ||
*When Tectorial membrane goes up, the hair cells are caused to open K+ channels such that K+ rushes in. | *When Tectorial membrane goes up, the hair cells are caused to open K+ channels such that K+ rushes in. | ||
- | *This stimulates Ca+ channels which causes the cell to release | + | *This stimulates Ca+ channels which causes the cell to release glutamate at the synapse. |
**We use disks, not ribbons, for release as a mechanism of modulation. | **We use disks, not ribbons, for release as a mechanism of modulation. | ||
- | |||
===Skin=== | ===Skin=== | ||
*We have several types of mechanically sensitive structures in our skin. | *We have several types of mechanically sensitive structures in our skin. | ||
- | |||
- | |||
- | |||
- | |||
- | |||
- | |||
See slide for a nice table | See slide for a nice table | ||
Line 217: | Line 203: | ||
- | *This is a bundle of naked nerve fibers surrounded by an | + | *This is a bundle of naked nerve fibers surrounded by an oniono of schwann cells. |
**Can be thought of as a form of myelination. | **Can be thought of as a form of myelination. | ||
*The schwann cells provide and regulate a viscous solution that moderates the depolarization of the nerve fibers. | *The schwann cells provide and regulate a viscous solution that moderates the depolarization of the nerve fibers. | ||
Line 228: | Line 214: | ||
***one cannot distinguish between two stimuli in the same field so when receptive fields are large, two distinct stimuli must be farther apart than when the receptive field is smaller | ***one cannot distinguish between two stimuli in the same field so when receptive fields are large, two distinct stimuli must be farther apart than when the receptive field is smaller | ||
*Pacinian and ruffini have large receptive fields | *Pacinian and ruffini have large receptive fields | ||
- | ** | + | **And locations of highest sensitivity; near the nerve terminal, presumably. |
**Example: medial half of the hand from the 5'th digits proximal filange to the distal end of the ulna. | **Example: medial half of the hand from the 5'th digits proximal filange to the distal end of the ulna. | ||
*Meissner's corpuscles, Merkel's disks, and free nerve endings have small receptive fields | *Meissner's corpuscles, Merkel's disks, and free nerve endings have small receptive fields | ||
Line 238: | Line 224: | ||
===Pain (stimulus noxious to the body)=== | ===Pain (stimulus noxious to the body)=== | ||
*The major information is that sharp pain is transmitted by a-delta fibers (myelinated) and dull / burning pain is by c-fibers (unmyelinated). | *The major information is that sharp pain is transmitted by a-delta fibers (myelinated) and dull / burning pain is by c-fibers (unmyelinated). | ||
- | *Some NT peptides can sensitize for pain (increase the sensitivity) | + | *Some NT peptides can sensitize for pain (increase the sensitivity). |
- | + | ||
*Mechanisms are as follows: | *Mechanisms are as follows: | ||
**P2x mechanism: | **P2x mechanism: | ||
- | ***An ATP | + | ***An ATP dependent mechanism |
***Nail in a hand causes cell damage. | ***Nail in a hand causes cell damage. | ||
***ATP is released | ***ATP is released | ||
- | ***ATP sensitive p2x | + | ***ATP sensitive p2x anatropic channels are on the neurve terminals and are depolarized |
***This causes opening of voltage gated na channels and the propagation of an AP. | ***This causes opening of voltage gated na channels and the propagation of an AP. | ||
- | **ASIC mechanism | + | **ASIC mechanism |
***Proton-sensitive | ***Proton-sensitive | ||
***Organelles release protons | ***Organelles release protons | ||
***Proton sensitive channels cause depolarization and an AP via T2D channels | ***Proton sensitive channels cause depolarization and an AP via T2D channels | ||
- | **K+ release | + | **K+ release |
***Cells are damaged and release K+ | ***Cells are damaged and release K+ | ||
***Increases the ECF K+ concentration which causes depolarization of the neuron. | ***Increases the ECF K+ concentration which causes depolarization of the neuron. | ||
Line 261: | Line 246: | ||
*TRP channels are crucial for mediating temperature sensing. | *TRP channels are crucial for mediating temperature sensing. | ||
*TRP channels are thought to be mechanically activated, or kind of ligand gated; it's a little unclear, maybe kind of a form of voltage "sensitive". | *TRP channels are thought to be mechanically activated, or kind of ligand gated; it's a little unclear, maybe kind of a form of voltage "sensitive". | ||
- | *These cover the entire range (30 | + | *These cover the entire range (30+C to 60+C). |
*Fibers that express TRP channels at nerve channels are unmyelinated. | *Fibers that express TRP channels at nerve channels are unmyelinated. | ||
**These are the c-fibers we spoke of previously. | **These are the c-fibers we spoke of previously. | ||
Line 290: | Line 275: | ||
***chain fibers (nuclei are found in a chain) | ***chain fibers (nuclei are found in a chain) | ||
****important for static chain | ****important for static chain | ||
- | *** | + | ***back fibers (nuclei are in a specific location) |
- | **have a spiral shaped terminals on the chain or | + | **have a spiral shaped terminals on the chain or back fibers |
**When stretched, non-selective cation channels are activated which causes depolarization, vgna channels, AP | **When stretched, non-selective cation channels are activated which causes depolarization, vgna channels, AP | ||
- | *Muscle spindles are slow | + | *Muscle spindles are slow adopters which allows us to detect our muscle location very precisely. |
*More on intrafusal muscles: | *More on intrafusal muscles: | ||
**Aligned in parallel with extrafusal muscles. | **Aligned in parallel with extrafusal muscles. | ||
**We need them to measure the length and stretch of our extrafusal muscles. | **We need them to measure the length and stretch of our extrafusal muscles. | ||
**Chain fiber intrafusal muscles | **Chain fiber intrafusal muscles | ||
- | ***Receive some motor | + | ***Receive some motor efferten ("exit" the cns) fibers which can induce the contraction of the intrafusals. |
***However, there is no contractile apparatus in the middle of the fiber--only found at the periphery. | ***However, there is no contractile apparatus in the middle of the fiber--only found at the periphery. | ||
***We need this motor stimulation so that the length of the intrafusal muscle will stay the same as the extrafusal muscles. | ***We need this motor stimulation so that the length of the intrafusal muscle will stay the same as the extrafusal muscles. | ||
Line 306: | Line 291: | ||
*In addition to the MuS, we have the golgi-tendon organ. | *In addition to the MuS, we have the golgi-tendon organ. | ||
*It senses the force generated by the muscle and the tension in the tendon. | *It senses the force generated by the muscle and the tension in the tendon. | ||
- | *It is set in series | + | *It is set in series witht he extrafusal muscles. |
- | *There are collagen fibers | + | *There are collagen fibers squish the free nerve endings sucht aht the stretch receptors are activated, vgna channels are activated, and an AP is fired. |
- | ===Primary sensory afferents | + | ===Primary sensory afferents innervatinghuman skin=== |
*There are several different types of afferent ("at" the cns) fibers for communicating sensation back to the CNS. | *There are several different types of afferent ("at" the cns) fibers for communicating sensation back to the CNS. | ||
*a-alpha | *a-alpha | ||
**For proprioceptors | **For proprioceptors | ||
- | |||
*a-beta | *a-beta | ||
**myelinated | **myelinated | ||
- | **for touch or | + | **for touch or mechanosensitive |
**some proprioception | **some proprioception | ||
*a-gamma | *a-gamma | ||
**Motor to intrafusal fibers | **Motor to intrafusal fibers | ||
- | |||
*a-delta | *a-delta | ||
**sensation of sharp pain | **sensation of sharp pain | ||
**called stimuli | **called stimuli | ||
**some touch receptors | **some touch receptors | ||
- | |||
*All a-fibers are myelinated | *All a-fibers are myelinated | ||
*b | *b | ||
Line 334: | Line 316: | ||
**some touch | **some touch | ||
**unmyelinated | **unmyelinated | ||
- | |||
- | |||
- | |||
- | |||
- | |||
- | |||
===References=== | ===References=== |