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Sensory Receptors
| Question | Answer |
|---|---|
| What is a free nerve ending? | Bare dendrites |
| What fibers have free nerve endings? | Pain, temperature, tickle, itch, and light touch |
| What are encapsulated nerve endings? | Dendrites enclosed in CT capsule |
| What fibers have encapsulated nerve endings? | Pressure, vibration, and deep touch |
| What are separate sensory cells? | Specialized cells that respond to stimuli - vision, taste, hearing, balance |
| What is the function of encapsulation? | Enhance sensitivity or specificity of receptor |
| Where are proprioceptors located? | Muscle, tendon, joint, and internal ear |
| What do proprioceptors detect? | Senses body position and movement by detecting muscle length and tension |
| What is the destination for impulses from proprioceptors? | Cerebellum and primary somatosensory area |
| When would we want adapting receptors? | When there isn't a change to stimuli that's not painful - like putting clothes on |
| When would we want non-adapting receptors? | Pain, body position |
| Mechanoreceptors detect deformation (pressure or touch), what are the 4 main ones? | Merkel's disks, Meissner's corpuscles, Ruffini endings, and Pacinian corpuscle |
| Where are the mechanoreceptors located, relative to each other? | Merkel's disks and Meissner's corpuscle are smaller and located towards surface. Ruffini endings and Pacinian corpuscle are larger and located deeper. |
| Where are free nerve endings located? | Epidermis interspersed among keratinocytes, papillary layer of dermis, many other tissues |
| Because Merkel's disks and Meissner's corpuscles are located towards the surface, what is a common stimuli? | Touch |
| Because Meissner's corpuscle is stimulated by fine touch and low frequency vibration, what can we infer about its location? | In areas with maximum sensitivity - dermal papillae of thick skin (digits, palmar surface of hands/feet), eyelids, external genitalia, nipples, lips |
| Where are Merkel endings? | Stratum basale with extension of pseudopodia into keratinocyte layer - most numerous in thick skin |
| Where are pacinian corpuscle located? | Dermis and subcutaneous tissue - also in mesenteries, bladder wall, joint capsules, external genitalia |
| How does the adaptation of pacinian corpuscle's differ from the rest of the mechanoreceptors? | Responds to ion channels in nerve membranes which open in response to compression |
| What are Krause end bulbs? | Somatic receptor that responds to pressure and coldness |
| Where are Krause end bulbs located? | Papillary dermis of the conjunctivea, CT of mouth, tongue, pharynx, and external genitalia |
| What are Ruffini corpuscle? | Somato receptor that responds to tension generated in surrounding collagen fibers of CT and heat |
| What is the implication of the stimuli of Ruffini corpuscle? | Because they detect tension, it contributes to proprioception and kinesthesia |
| Where are Ruffini corpuscle located? | Deep in dermis, numerous on plantar surface of feet |
| How do Ruffini corpuscle contribute to proprioception and kinesthesia? | Provides feedback for grabbing objects, controlling finger position, and movement |
| What somatic receptors are rapidly adapting? | Meissner's corpuscle and hair root plexus |
| What are slow adapting somatoreceptors? | Merkel and Ruffini |
| What receptors detect touch? | Meissner's, hair root plexus, Merkel, and Ruffini |
| What receptors detect pressure? | Pacinian, Ruffini, Krause |
| What receptors detect vibration? | Meissner (low), Pacinian (high) |
| What receptors detect itch/tickle? | Free nerve endings |
| What receptors detect temperature? | Cold: free nerve endings in stratum basale, Krause. Warm: free nerve endings in dermis, Ruggini |
| What cold temperatures are detected? | 10-40 celsius |
| What warm temperatures are detectedd=? | 32-48 celsius |
| What temperature produces pain? | Below 10 and over 48 celsius |
| Describe the adaptation for thermal sensation | Rapidly at first but continue to generate impulses at low frequency |
| Where are pain receptors located? | Nearly every tissue except brain |
| What stimulates pain receptors? | Excessive distension, muscle spasm, inadequate blood flow |
| What do tissues release to stimulate nociceptors? | K, kinins, or prostaglandins |
| What is fast pain? | Acute - sharp pain like needle puncture or cut - not felt in deeper tissues |
| What fibers detect fast pain? | Larger A nerve fibers |
| What is slow pain? | Chronic - begins more slowly and increases in intensity - aching, throbbing - in both superficial and deeper tissues |
| What fibers detect slow pain? | Smaller C nerve fibers |
| What is referred pain? | Visceral pain that is felt in surface area far from stimulated organ |
| Visceral sensory nerves travel with what type of fibers? | Sympathetic nerve fibers T1-L2 |
| What is the innervation of the foregut? | Greater splanchnic nerve from sympathetic (T5-T9), vagus from parasympathetic |
| Where would referred pain for the foregut be felt? | Epigastric region |
| What comprises the foregut? | Stomach, spleen, liver, pancreas, kidneys, small intestine |
| What is the innervation of the midgut? | Lesser splanchnic nerve from sympathetic (T10-T12), vagus from parasympathetic |
| Where would referred pain for the midgut be felt? | Umbilical region |
| What comprises the midgut? | Small intestine, proximal colon |
| What is the innervation of the hindgut? | Lumbar (least) splanchnic nerve from sympathetic (Y12-L1), S2/3/4 from parasympathetic |
| Where would referred pain of the hindgut be felt? | Hypogastric region |
| What organs comprises the hindgut | Distal colon, rectum, anal canal |
| What nerve keeps diaphragm alive? | Phrenic nerve - C3/4/5 |
| What does the sensory phrenic nerve supply? | Peritoneum that covers the diaphragm from below |
| How does referred pain travel? | Somatic to somatic, not visceral to somatic |
| How can referred pain be felt through the phrenic nerve | Supplied to peritoneum to dermatome of phrenic nerve |
| Which dorsal branch doesn't have sensory? | C1 |
| Where would liver and gallbladder be felt? | Right shoulder, right lower back, right area underneath scapula |
| Where would gallbladder be felt? | Umbilical and right lumbar |
| Where would stomach be felt? | Epigastric |
| Where would kidneys be felt? | Entire lower abdomen - hypogastric, right/left iliac |
| Where would heart be felt? | Left chest, traveling down ulnar side of left arm |
| What is proprioceptive or kinesthetic sense? | Awareness of body position and movement |
| Where are golgi tendon organs found? | Junction of tendon and muscle |
| What makes up a golgi tendon organ? | Encapsulated bundle of collagen fibers laced with sensory fibers |
| What do golgi tendon organs detect? | When tendon is overly stretched → will send signals to CNS → results in muscle relaxation. Detects force of muscle contraction. |
| Where are joint kinesthetics receptors found? | Around articular capsules of synovial joints |
| What do joint kinesthetic receptors detect? | Detect pressure from free nerve endings and Ruffini corpuscle, acceleration and deceleration of joints during movement from small pacinian corpuscles |
| What do muscle spindles detect? | Amount of stretch or lengthening of muscle |
| What are muscle spindles? | Specialized intrafusal muscle fibers enclosed in a connective tissue capsule, innervated by gamma motor neurons |
| How does the brain regulate muscle tone? | Controlling gamma fibers |
| What two fibers make up a skeletal muscle? | Intrafusal muscle fibers and extrafusal muscle fibers |
| What do extrafusal muscle fibers do? | Job of the muscle - contracting and producing movement |
| What is the relationship between the amount of muscle spindles in a muscle and movement? | More spindles means more awareness of muscle which is needed for fine movements - more would be in hands |
| What muscle does not have muscle spindles? | Middle ear muscles because not in charge of tension control |
| What layer of the grey matter is in charge of conveying pain and temperature? | Laminae 2 - substantia gelatinosa |
| How can pain be modulated by free nerve endings are non-adapting? | Gate pain theory - signals must be allowed through a gate before they can actually make it to the brain |
| What NT carries pain info? | Substance P |
| How can the gate be closed? | Degrade NT, suppressing synapse - rubbing it away or willing it away |
| What does it mean to will it away? | CNS can send inhibitory signals (enkephalins, endorphins) to gate which block action of substance P |
| What are ways to "will it away" for pain modulation? | Meditation, hypnosis, distraction, placebos |
| What does it mean to "rubbing it away"? | Touch fibers enter spinal cord also have collateral synapses with gate - NT being serotonin |
| What class of fibers are temperature carried in? | III and IV |
| What class of fibers are pain carried in? | Sharp - III, Aching - IV |
| What class of fibers are proprioceptive carried in? | I and II |
| What class of fibers are tactile carried in? | II |
| What class of fibers are golgi tendon organs carried in? | I |
| What class of fibers are joint kinesthetic carried in? | II |
| How do we generally sense things? | Receptor is disturbed → membrane permeability changes → generator potential →strong enough generator potential → create an AP in appropriate sensory nerve → AP is propagated and carries info to spinal cord and brain |
| What is a graded response? | Greater stimulus, greater the generator potential, and the higher frequency of the AP |
| How is a generator potential different from the action potential | Amplitude: GP - depends on strength, AP - all or none. Origin: GP - arises in dendrites and cell body, AP - trigger zones and propagate along axon |
| What does not having refractory period mean? | Allows for summation of stimuli - repeated stimuli can create a larger generator and more frequent AP than a single |
| How does signal intensity affect nerve impulses? | Characteristic of each nerve pulse. Different sensory signal intensity can be transmitted either by using increased number of fibers or by sending more AP along a single nerve fiber |
| What is spatial summation | Summation of effects of NTs released from several neurons onto one neuron |
| What is temporal summation? | Summation of effects of NT released from 2 or more firing of the SAME neuron in rapid succession onto a second neuron |
| What is the perception of intensity for temporal summation? | Stronger stimulus translate into more frequent APs |
| What is the perception of intensity for spatial summation? | Stronger stimulus hits more receptors and therefore sends APs along more nerve fibers |
| How do we differentiate a light tough from a firmer tough, in regards to frequency of impulses? | Firm pressure generates impulses at a higher frequency (temporal summation) |
| How do we differentiate a light tough from a firmer tough, in regards to number of sensory neurons activated? | Firm pressure stimulates more neurons than a light tough - spatial summation |
| What summation does firm vs light tough have? | Both summations at the same time |
| What is lateral inhibition? | Capacity of an excited neuron to reduce activity of its neighbors |
| What is the mechanism behind lateral inhibition? | After being touched, sensory neurons in the skin next to another are stimulated. Fired neurons suppress the stimulation of neighboring neurons - most stimulated neuron and least inhibited will fire so firing pattern tends to concentrate at stimulus peaks |
| What is the receptor field? | Region of space in which the presence of a stimulus will alter the firing of that neuron |
| Where are receptor fields located in the somatosensory system? | Skin of internal organs |
| What do large receptor fields allow? | Allows detection of change over a wider area but lead to less precise perception |
| What do smaller receptor fields allow | Detect fine detail - more precise |
| What pathway does lateral inhibition use? | Posterior column of spinal cord |
| What is two point discrimination? | Ability to discern that two nearby objects touching skin are truly two distinct points, not one |
| How does the receptor area relate to two-point discrimination? | Smallest, most dense receptor area have greater cortical representation - able to recognize two separate points at a much smaller distance (more precision) than large receptor areas which has less precision |
| What would happen if there is something wrong with the posterior spinal cord? | Will not have two-point discrimination |
Created by:
nnguyen44
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