Sensation & Pain PDF

+-----------------------------------+-----------------------------------+ | **[QUESTION]** | **[ANSWER]** | +===================================+===================================+ | What is a receptor? | A cell/specialized neuron that | |...

+-----------------------------------+-----------------------------------+ | **[QUESTION]** | **[ANSWER]** | +===================================+===================================+ | What is a receptor? | A cell/specialized neuron that | | | responds to energy **graded | | | potential** | +-----------------------------------+-----------------------------------+ | If the potential of the neuron | **Action potential** | | reaches threshold, they can | | | generate an? | | +-----------------------------------+-----------------------------------+ | What are examples of receptors | Photoreceptors, cochlear hair | | that **cannot** produce AP's? | cells, vestibular hair cells | +-----------------------------------+-----------------------------------+ | How can a neuron convey | 1\) A **SINGLE** neuron change | | intensity? | AP **FREQUENCY** | | | | | | 2\) **MULTIPLE** neurons act in | | | parallel | | | | | | 3\) Multiple different neurons | | | respond to diff. ranges | +-----------------------------------+-----------------------------------+ | What is the phenomenon when | **RANGE FRACTIONATION** | | different cells have different | | | firing thresholds over a range of | | | stimulus intensities? | | +-----------------------------------+-----------------------------------+ | Ian became sick with a virus. He | He has a problem with his | | was unable to move voluntarily, | **PARIETAL LOBE**. There is no | | though he did have muscle | proprioception. He doesn't know | | strength. Why was it that he | where his limbs are. He needs to | | couldn't move unless he watched | actually be able to see his limbs | | where he walked? Why couldn't he | (with the lights on) and look | | move properly when the lights | down while he is walking to be | | were out? | able to move. | +-----------------------------------+-----------------------------------+ | **RECEPTORS FOR SENSATION** | | +-----------------------------------+-----------------------------------+ | What are the five receptors for | Free Nerve Endings, Merkel's | | the somatosensory system? | Disc, Meissner's Corpuscle, | | | Pacinian Corpuscle, and Ruffini's | | | Corpuscle | +-----------------------------------+-----------------------------------+ | What are free nerve endings | Pain, temperature | | involved in? | | +-----------------------------------+-----------------------------------+ | What is Merkel's disc involved | **(PRECISE) sustained** touch | | in? | (**tonic** receptors), **SLOW & | | | SUPERFICIAL** | +-----------------------------------+-----------------------------------+ | What is Meissner's corpuscle | **(PRECISE) burst** touch | | involved in? | (**phasic** receptors), **FAST & | | | SUPERFICIAL (texture)** | +-----------------------------------+-----------------------------------+ | What is Pacinian corpuscle | **(IMPRECISE) VIBRATION** and | | involved in? | **pressure, DEEP** | +-----------------------------------+-----------------------------------+ | What is Ruffini corpuscle | **STRETCH & TENSION in the skin | | involved in? | (SLOW), DEEP** | +-----------------------------------+-----------------------------------+ | What are the characteristics of C | Small, unmyelinated, **slow** | | fibers and what type of pain do | transmission, **dull** pain | | they transmit? | | +-----------------------------------+-----------------------------------+ | What are the characteristics of | Large, myelinated, **fast** | | A-Δ fibers and what type of pain | transmission, **sharp** pain | | do they transmit? | | +-----------------------------------+-----------------------------------+ | What do TRPV1 free nerve endings | Moderate heat | | respond to? | | +-----------------------------------+-----------------------------------+ | What do TRPV2 free nerve endings | High temperature | | respond to? | | +-----------------------------------+-----------------------------------+ | What do TRPM8 & CMR1 free nerve | Low temperature (cool) | | endings respond to? | | +-----------------------------------+-----------------------------------+ | What is the "hot" in chilies and | **Capsaicin (neurotoxic)** | | activates C fibers via TRPV1 free | | | nerve endings? | | +-----------------------------------+-----------------------------------+ | What is the mechanism of Pacinian | You have one neuron (unipolar) | | corpuscles? | connecting the hand to the spinal | | | cord (Dorsal Column), and another | | | neuron (dorsal root ganglion) | | | that leads to the thalamus. This | | | is **MECHANICALLY GATED**. | | | Stimuli stretch the membrane | | | which opens Na^+^ channels graded | | | potential. If threshold potential | | | is exceeded action potential | +-----------------------------------+-----------------------------------+ | What is a receptive field? | The part of the world a sensory | | | neuron responds to | +-----------------------------------+-----------------------------------+ | Where do you have the most | In your **FINGERS** | | precise two-point discrimination? | | +-----------------------------------+-----------------------------------+ | How do tonic receptors perceive | **Slow/no decline in AP frequency | | sensory information? | (continues to fire)** | +-----------------------------------+-----------------------------------+ | How do phasic receptors perceive | **Adapt quickly by decreased AP | | sensory information? | frequency (fires at initiation)** | +-----------------------------------+-----------------------------------+ | What is the effect on an | Center -- max. firing | | on-center, off-surround cell for | | | touch in center, touch in | Surround -- decreased firing | | surround, touch far away? | | | | Far away -- NO effect | +-----------------------------------+-----------------------------------+ | **SENSATION PATHWAYS, PERCEPTION, | | | & PAIN** | | +-----------------------------------+-----------------------------------+ | Which structure do most sensory | **Thalamus** | | pathways pass through? | | +-----------------------------------+-----------------------------------+ | Which tactile system is | **Dorsal column -- medial | | responsible for touch, vibration, | lemniscal** pathway | | and proprioception? | | +-----------------------------------+-----------------------------------+ | Which tactile system is | **Spinothalamic** pathway | | responsible for pain and | | | temperature? | | +-----------------------------------+-----------------------------------+ | What represents the innervation | **Cortical map** | | of a body region? | | +-----------------------------------+-----------------------------------+ | What happens to the somatosensory | It **REORGANIZES**. This might be | | cortex when you amputate a body | a cause of phantom limb pain, | | part, specifically a hand? | because nearby areas of the | | | cortex take over and might tell | | | you that you feel pain on a body | | | part you no longer have. | +-----------------------------------+-----------------------------------+ | What is the definition of pain? | An unpleasant sensory and | | | emotional experience associated | | | with actual or potential tissue | | | damage, or described in terms of | | | such damage | +-----------------------------------+-----------------------------------+ | What are the 3 different systems | **Cognitive** system | | that are integral to pain | | | perception? | **Motivational-affective** system | | | | | | **Sensory-discriminative** system | +-----------------------------------+-----------------------------------+ | What is the name of specialized | **Nociceptors (in free nerve | | receptors that respond to temp. | endings)** | | change, chemicals, and tissue | | | injury? | | +-----------------------------------+-----------------------------------+ | What is the pain process, | The hammer hits your thumb, which | | starting with being hit with the | hurts tissue. These tissues which | | hammer? | contain chemicals like | | | **HISTAMINE, SEROTONIN, K^+^, | | | PROSTAGLANDINS, and | | | LEUKOTRIENES** release the | | | chemicals into local space. If | | | the membranes never ruptured, we | | | wouldn't have pain. But because | | | they did, these chemicals | | | activate the free nerve endings. | | | Once activated, these free nerve | | | endings send an action potential | | | to the spinal cord, specifically | | | to the spinothalamic pathway. | | | | | | Meanwhile, **SUBSTANCE P** | | | stimulates the Mast Cell and acts | | | as a vasodilator. | +-----------------------------------+-----------------------------------+ | What is one of the | **Substance P (important in | | neurotransmitters involved in | brain, spinal cord, & | | pain signaling? | periphery)** | +-----------------------------------+-----------------------------------+ | What leads to congenital | **Inherited mutated Na^+^** | | insensitivity to pain? | channels in pain fibers in dorsal | | | root ganglia -- **loss of | | | function** | +-----------------------------------+-----------------------------------+ | What leads to congenital | **Gain-of-function** of | | hypersensitivity to pain ('Man on | **Na~V~1.7** | | Fire' Syndrome)? | | +-----------------------------------+-----------------------------------+ | Why do we need pain? | Pain is life-saving | +-----------------------------------+-----------------------------------+ | Which structure is involved in | **Periaqueductal gray (PAG)** | | pain perception? | | +-----------------------------------+-----------------------------------+ | Which region of the brain is this | **Midbrain** | | located in? | | +-----------------------------------+-----------------------------------+ | What receptors are located in the | **Opioid receptors** | | structure involved in pain | | | perception? | | +-----------------------------------+-----------------------------------+ | Dr. Livingstone was attacked by a | His emotions were on overdrive. | | lion. Why didn't he feel pain at | Emotions DO make a difference in | | first? | sensation perception. | +-----------------------------------+-----------------------------------+ | How can descending systems reduce | The LIMBIC SYSTEM sends | | pain? | information down to increase the | | | activity in the periaqueductal | | | gray. This is an attempt to limit | | | pain, especially chronic pain. | | | Remember that pain has both a | | | discriminative and an emotional | | | component. In chronic pain, the | | | emotional content grabs your | | | attention and won't let you let | | | go of it | +-----------------------------------+-----------------------------------+ | How can descending systems | Similarly, if you and your limbic | | increase pain? | system decide that something is | | | going to be more painful than it | | | is, then your limbic system is | | | going to send signals down to | | | make pain a lot more painful. It | | | is all about attention and | | | emotional/cognitive factors | +-----------------------------------+-----------------------------------+ | Pain can be blocked in the spinal | **Gate Control Theory of Pain** | | cord according to what theory? | | +-----------------------------------+-----------------------------------+ | What is the mechanism of this | Gate can be closed by increased | | blockage of pain? | activity in A fiber | +-----------------------------------+-----------------------------------+ | What is a TENS unit and how can | TENS stands for **transcutaneous | | it help pain? | electrical nerve stimulation**. | | | The unit delivers electrical | | | pulses to the skin. The low level | | | shocks block the pain of the | | | C-Fibers with A-alpha and A-Beta | | | fibers. A-alpha and A-Beta fibers | | | are inhibitory. This only works | | | if you use it every so often. If | | | you use it too much, as people | | | with chronic pain feel like they | | | need to, your brain gets used to | | | it. **Supports gate control | | | idea** | +-----------------------------------+-----------------------------------+ | What are some examples of | Meditation, prayer, acupuncture, | | non-drug treatments for pain? | massage, and physical activity | +-----------------------------------+-----------------------------------+ | **CHRONIC PAIN** | | +-----------------------------------+-----------------------------------+ | What is chronic pain? | Pain that persists even after an | | | injury has healed. It is | | | pointless and nonhelpful. It | | | occurs in a progressive, vicious | | | cycle | +-----------------------------------+-----------------------------------+ | What are the two different ways | **NEUROGENIC** - pain resulting | | the scientific community | from damage to nerves | | categorizes chronic pain? | | | | **PSYCHOGENIC** - pain not due to | | | disease, injury, or any visible | | | damage | | | | | | It's hard to distinguish because | | | there is no objective measure of | | | pain. We can't measure it from | | | the outside. | +-----------------------------------+-----------------------------------+ | In neurogenic chronic pain, what | Onset of severe pain limited to | | are characteristics of stage I? | the site of injury | | | | | | Increased sensitivity of skin to | | | touch | | | | | | Localized swelling | | | | | | Usually lasts a few weeks then | | | subsides | +-----------------------------------+-----------------------------------+ | In neurogenic chronic pain, what | Pain becomes more severe and more | | are characteristics of stage II? | diffuse | | | | | | Swelling tends to spread | | | | | | Hair and nails become brittle | | | | | | Muscle wasting begins | +-----------------------------------+-----------------------------------+ | What is the term for this disease | **Reflex Sympathetic Dystrophy | | state? | (RSD)** | +-----------------------------------+-----------------------------------+ | How does chronic pain affect the | Chronic pain remodels it. | | spinal cord? | **NEUROGENIC PAIN** is due to | | | **INAPPROPRIATE SIGNALING** of | | | pain by neurons | | | | | | - Spinal cord takes up | | | **SUBSTANCE P**, released | | | during pain, and **REMODELS | | | THEIR DENDRITES** | | | | | | - **OVERACTIVITY OF SYMPATHETIC | | | INPUT** Dorsal horn neurons | | | (for light touch) become | | | ***hyperexcitable***. There | | | is **INCREASED** spontaneous | | | activity and response to ALL | | | touch. (Now, light touch = | | | PAIN) | | | | | | - **GABA inhibitory** | | | interneurons become | | | **EXCITATORY** | | | | | | - \*In other words, new | | | connections cause non-pain | | | receptors to also stimulate | | | the pain system | +-----------------------------------+-----------------------------------+ | What do we know about patients | The somatosensory cortex is | | with chronic pain at rest? | overactive. This is inappropriate | | | activation, because nothing is | | | going on. It causes itself to | | | become more sensitive | | | (upregulating) | +-----------------------------------+-----------------------------------+ | Where does pain become an | In the **CINGULATE CORTEX**. | | emotion? | Activity increases here, but not | | | in the somatosensory cortex, as | | | pain unpleasantness increases. So | | | while your somatosensory cortex | | | localizes the pain, and we see | | | that activity in there does not | | | increase, the activity in the | | | cingulate cortex increases, and | | | things feel overwhelmingly | | | painful | +-----------------------------------+-----------------------------------+ | **SENSORY PROCESSING DISORDERS** | | +-----------------------------------+-----------------------------------+ | What is it called when you have a | **SYNESTHESIA**. Can be caused by | | stimulus in one modality that | LSD, posterior temporal lobe | | creates a sensation in another? | seizures, blindness or deafness, | | What are some possible causes of | or nothing at all. It can occur | | this? | spontaneously | +-----------------------------------+-----------------------------------+ | A woman has a stroke in her right | She had audiotactile synesthesia | | thalamus. Later, certain sounds | as a result of the cortex | | induced intense unpleasant | reorganizing (overlap of auditory | | tingling in her left hand and | and touch cortices) | | arm. Why? | | +-----------------------------------+-----------------------------------+ | What are some theories for | The brain exhibits inappropriate | | phantom limb pain? | sensation, causing signaling of | | | pain system | +-----------------------------------+-----------------------------------+