Sensory (1)

Question 1

What is the basic organization of the sensory system?

Answer 1

stimulus->filter->modified stimulus-> transducer-> receptor potential-> encoder -> AP-> to CNS-> sensory systems-> association systems-> effector systems (motor)-> to periphery effectors-> response

Question 2

What is the filter?

Answer 2

first functional element of sensory receptor, usually non-neuronal, only a portion conveyed to transducer, conditions the stimulus making receptor function with relative specificity of modality; limits access and changes stimulus parameters

Question 3

What is the transducer?

Answer 3

converts stimulus energy to change in the voltage across the membrane of sensory receptor with minimal loss of information; creates the receptor potential(generator or local potential); doesn’t respond to electrical stimulus

Question 4

How is the receptor potential generated?

Answer 4

simultaneous change in membrane permeability of Na and K ions; it is a graded potential (increases in magnitude as stimulus gets stronger); travels short distance doesn’t propagate

Question 5

What is the encoder?

Answer 5

converts the magnitude of a receptor potential into a frequency code that is carried by AP along an axon (aka trigger zone)

Question 6

What is the filter, transducer and encoder for a pacinian corpuscle?

Answer 6

F: CT, T: unmyelinated free nerve ending, produces receptor potential when deformed, E: trigger zone, first node of Ranvier

Question 7

What are the different types of sensory receptors? examples.

Answer 7

mechanical- touch, proprioception, joint position, hearing and balance; chemical- pain, itch, taste, smell, pH and osmolarity; thermal- body temperature, temperature of ambient air and objects we touch; electromagnetic- vision; and poly-modal- nociceptors respond to 2 or more stimuli (mechanical or thermal)

Question 8

What is a sensory unit?

Answer 8

connected to sensory receptors of all the same kind

Question 9

What is a receptive field?

Answer 9

fraction of the total energy of a particular modality that initiates a response in a sensory receptor or sensory unit; sensory unit with the most sensory receptors has the largest receptive field

Question 10

What are the four basic attributes of a stimulus?

Answer 10

modality, location, intensity, and timing

Question 11

What does the modality tell the body?

Answer 11

along with submodality is codes for what is present

Question 12

What are examples of submodalities and their corresponding modalities?

Answer 12

vision- color, shape movement; hearing- pitch; taste- sweet, sour, salty; smell- pungent, musk, floral, putrid; somesthesis- temperature, texture and rigidity

Question 13

What is the place theory?

Answer 13

modality coding in labeled lines- an anatomical grouping of receptors of pathways devoted to the particular modality

Question 14

How are sub-modalities coded?

Answer 14

by pattern coding; pattern activity within the system of labeled lines

Question 15

How is location coded?

Answer 15

anatomical sorting or organization of pathways and their central projections; i.e. homunculus

Question 16

How is intensity coded?

Answer 16

by total number of impulses per second coming from receptor population; rate, recruitment, adaptation, threshold and saturation

Question 17

What is recruitment? How does it code for intensity?

Answer 17

number of units that get activated by stimulus increase with stimulus intensity; higher frequency is found in unit closest to the stimuli

Question 18

What is adaptation and how does it code for intensity?

Answer 18

measure of how well a sensory receptor maintains its response to a constant stimulus; slowly adapting receptors keep producing membrane potentials as long as stimulus is applied; rapid adapting sensory receptors stop even with stimulus still present

Question 19

What is saturation and how is it used to code for intensity?

Answer 19

as intensity increases eventually nerve fiber reaches upper limit for carrying impulses; further increases in stimulus do not produce a corresponding increase in response

Question 20

What types of stimuli is the somatosensory system sensitive to?

Answer 20

pressure, joint position, muscle position, temperature of limbs and pain

Question 21

how is the somatosensory system different than other systems?

Answer 21

receptors spread throughout rather than concentrated at small specialized locations; it is a group of at least 4 senses rather than just one- touch temperature, body position, pain and various subdivisions

Question 22

What are the different sub modalities of touch?

Answer 22

itch/tickle- indiscriminate; discriminate touch- touch, pressure, flutter, and vibration

Question 23

What are the sub-modalities of pain?

Answer 23

sharp cutting pain, dull burning pain, and deep aching pain

Question 24

What are the sub modalities of proprioception?

Answer 24

position (static forces)- muscle length and tension; movement (dynamic)- muscle length and tension, joint position, pressure and angle

Question 25

Primary afferent axons come in different sizes, order them from big to small. What sense do they correspond with?

Answer 25

Aalpha- proprioceptors of muscles, Abeta- mechanoreceptors of skin, Asigma- pain and temperature, and C- temperature, pain

Question 26

What are the parallel pathways of somatic sensation? Fibers in them and sensation associated with it?

Answer 26

Dorsal column-medial lemniscal pathway; A alpha beta and sigma; touch, vibration, two point discrimination and proprioception; or spinothalamic- A sigma and C; pain, temperature, some touch

Question 27

What are the different types of mechanoreceptors? what do they sense?

Answer 27

Hair, Pacinian corpuscle, Ruffini ending, Meissner’s corpuscle and Merkel disk receptor

Question 28

What are the relative sizes of mechanoreceptor receptive fields?

Answer 28

Meissner’s very small- pen, Pacinian very large, Merkel’s small and Ruffini’s large

Question 29

Which mechanoreceptors are fast or slow adapting?

Answer 29

fast- Meissner’s, Pacinian, hair folicle; slow- Merkles and Ruffini’s

Question 30

How does the Pacinian corpuscle work?

Answer 30

capsule with fluid between the layers and free nerve ending in the center; layers are distended in and put pressure initially on the nerve then fluid spreads around so nerve isn’t pinched; esp sensitive to vibrating and high frequency stimuli

Question 31

Characterize the Meissner corpuscle by type and sensation.

Answer 31

encapsulated and layered; touch; flutter movement

Question 32

Characterize the Ruffini corpuscle by type and sensation.

Answer 32

encapsulated collagen, touch: stretch of skin

Question 33

Characterize the hair follicle by type and sensation.

Answer 33

unencapsulated; touch and movement; rapid

Question 34

Characterize the Merkel complex by type and sensation.

Answer 34

specialized epithelial cell; touch, pressure, form

Question 35

Characterize the free nerve ending by type and sensation.

Answer 35

unencapsulated; pain, touch or temperature; adaptation depends

Question 36

Over what range to warm receptors sense?

Answer 36

30-45 degrees celsius

Question 37

Over what range to cold receptors sense?

Answer 37

30 down to -10 degrees Celsius

Question 38

What effects the rate of firing in thermoreceptors?

Answer 38

cold fires faster during decreases in temperature and warm faster during increases

Question 39

What are the four categories of nociceptors and their stimuli?

Answer 39

mechanoreceptor- intense mechanical (pinching, sutting and stretching), Thermal- burning heat or extreme cold (>45 tissue damage), Chemically sensitive (mechanically insensitive)- variety of agents, K, pH, histamine, bradykinin, and polymodal- high intensity combo of mechanical, thermal and chemical

Question 40

What are the characteristics of slow pain? examples

Answer 40

burning or soreness, transmitted by thin fibers, poorly localized, all internal organs except brain, body wants to be immobile so see guarding, rigidity and spasm, diffuse slower onset,; labor pain, chemical burn, pain after fast pain in response to injury

Question 41

What are the characteristics of fast pain? examples

Answer 41

prickling, faster conducting because fibers are thicker, A-delta fibers, well localized, mainly skin, mouth and anus, immediate withdrawl on stimulation to avoid damage, pain does not radiate, short duration; surgical incision

Question 42

What is phantom pain?

Answer 42

pain of missing limb

Question 43

What are the causes of intracranial headache?

Answer 43

alcohol- toxicity irritates meninges and constipation- from absorbed toxic products or changes in circulatory system resulting from loss of fluid in the gut

Question 44

What are the causes of external headache?

Answer 44

muscle spasm- emotion/tension causes muscles of head to become spastic, pain referred to head; sinus- pain from mucus membranes, referred to behind the eyes or forehead or face; eye disorders- difficulty focusing stresses cilliary muscles and can cause spasms in facial and extra ocular muscles, excessive irradiation by light esp. UV causes irritation of the membranes around the eyes

Question 45

What substances activate nociceptors?

Answer 45

globulin and protein kinases, arachidonic acid, histamine, nerve growth factor, substance P and calcitonin gene related peptide, K, serotonin, ACh, low pH, ATP, muscle spasm, and lactic acid

Question 46

What is the gate theory of pain?

Answer 46

pain can be modified by nonpainful sensory input and neural activity from various nuclei within the brain (simultaneous activation of low threshold mechanoreceptors A-alpha and beta fibers- excites inhibitory interneuron in spinal cord lessoning signal sent to the brain)