Sensory mechanisms

Question 1

What are the five basic types of sensory receptors?

Answer 1

Mechanoreceptors 
Thermoreceptors
Nociceptors 
Electromagnetic receptors
Chemoreceptors

Question 2

Mechanoreceptors

Answer 2

Skin tactile sensibilities: free and encapsulated nerve endings
-merkel’s disc: expanded tip
Meissner’s corpuscles: encapsulated
Kraus’ corpucsles: encapsulated

Deep tissue sensibilities-expanded tip and free endings
Ruffini’s corpuscles: spray endings
Pacinian corpuscles: encapsulated

Hearing - in cochlea
Equilibrium - vestibular receptors
Arterial pressure - baroreceptors

Question 3

Nociceptors

Answer 3

Free nerve endings responding to pain

Question 4

Electromagnetic receptors

Answer 4

Ex. Rods and cones of the eye for vision

Question 5

Chemoreceptors

Answer 5

Examples: taste, smell, asterial oxygen, osmolarity, blood carbon dioxide, blood glucose, A.A and FA’s

Question 6

Differential sensitivity

Answer 6

Each type of receptor is highly sensitive to one type of stimulus and almost nonresponsive to other types

Question 7

Modality

Answer 7

The type of sensation, there are certain principle types

Question 8

Labeled line principle

Answer 8

Specificity of nerve fibers for transmitting only one modality of sensation

Question 9

Adaptation of receptors

Answer 9

Adapt partially or completely to any constant stimulus after a period of time, by adapt meaning the receptor stops firing or responding to the stimuli. Some adapt more or less than others.

Question 10

What are the mechanism of stimulation of receptors?

Answer 10

mechanical deformation
Application of a chemical
Temp change
Electromagnetic radiation

Question 11

Receptor potential - how is a receptor without a cell body, like a pacinian corpusle, fire?

Answer 11

Ex in pacinian rreceptor

Modality gated channel opened (modality being specified sensation) in response to touch or pressure (membrane deformation)

Local potential is generated by the receptor

If strong enough through summation an action potential can be generated in the first node of ranvier

Question 12

Tonic vs Phasic receptors

Answer 12

Tonic receptors

• slow adapting
• detect continuous stimulus strength
• transmit impulses as long as the stimulus is present
• examples: muscle spindles, golgi tendon organs, macula and vestibular receptors, baroreceptors and chemoreceptors

Phasic Receptors:

• rapidly adapting
• do not transmit a continuous signal
• stimulated only when stimulus strength changes
• transmit info regarding rate of change

Question 13

What are the major types of nerve fibers?

Answer 13

Type A

• alpha, beta, gamma and delta subtypes
• large and medium sized, myeliated fiber of spinal nerves

Type B

• small, unmyelinated fibers
• slow conductance
• many sensory fibers are these, most peripheral nerves and all postganglionic autonomic fibers

Question 14

Group Ia - Type A-alpha fibers

Answer 14

Fibers from annulospiral endings of muscle spindles

Question 15

Group Ib - Type A-alpha fibers

Answer 15

Fibers from glogi tendon organs

Question 16

Group II - Type A-beta and gamme fibers

Answer 16

Cutaneous tactile receptors and flower-spray

Question 17

Group III - Type A-delta fibers

Answer 17

Temperature, crude touch and prickling pain

Question 18

Group IV- Type C fibers

Answer 18

Pain, itch, temp and crude touch

Question 19

Differentiate spatial and temporal summation

Answer 19

Spatial summation - increaced number of fibers being activated at one time

temporal summation - signal strength is increased by increased the frequency of nerve impulses in each fiber

Question 20

What’s the basic organization of a specified neuronal pool?

Answer 20

Stimulatory feild: area in the pool stimulated by each incoming nerve fiber, so where the incoming fibers synapse with outgoing fibers ??

Discharge zone: includes all output fibers stimulated by an incoming fiber

Facilitated/inhibition zones: neurons further from the discharge zone that are facilitated but not excited. The connections in the pool between a incoming and outgoing fiber are not enough alone to excite or inhibit, so they are facilitators. (In tandem with other neurons)
Can be inhibitoy or excitatory

Question 21

What are the three types of physiological senses?

Answer 21

Mechanoreceptive

Thermoreceptive

pain

Question 22

Reverberatory circuit

Answer 22

Oscillatory, caused by positive feedback within a neuronal circuit and once stimulated may discharge for a long time

Question 23

Difference between converging pathways and converging pathways?

Answer 23

Diverging - amplification of a single/initial signal (an axon branching into many outputs)

Converging - multiple input fibers on one output neuron (can be from a single or multiple sources)