Lecture 4: General Sensory Mechanisms I

Question 1

What are the 5 basic types of sensory receptors?

Answer 1

• Mechanoreceptors
• Thermoreceptors
• Nociceptors
• Electromagnetic Receptors
• Chemoreceptors

Question 2

What is the definition of “differential sensitivity?

Answer 2

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

Question 3

What does modality refer to?

Answer 3

Refers to each of the prinicipal types of sensation.

**the functions of cranial nerves are called modalities**

Question 4

What does “labeled line principle” refer to?

Answer 4

Refers to the specificity of nerve fibers for transmitting only one modality of sensation.

Question 5

What are nociceptors and what to they respond to?

Answer 5

Free nerve endings responding to pain.

Question 6

What is an example in the human body of an electromagnetic receptor and what does it do?

Answer 6

Rods and Cones of the eye for vision.

Question 7

Give some examples that chemoreceptors respond to in the body.

Answer 7

• taste
• smell
• arterial oxygen
• osmolarity
• blood carbon dioxide
• blood glucose, amino acids, and fatty acids

Question 8

What doe thermoreceptors respond to?

Answer 8

Cold and Warm Receptors

Question 9

True or False:

Mechanoreceptors include both free and incapsulated endings receiving skin tactile sensibilities.

Answer 9

True

Question 10

What is an example of expanded tip endings of mechanoreceptors?

Answer 10

Merkel’s Discs

Question 11

Give three examples of encapsulated endings of mechanoreceptors.

Answer 11

• Meissner’s corpuscles
• Kraus’ corpuscles
• Pacinian corpuscles

Question 12

Which corpuscle is considered a spray ending of a mechanoreceptor?

Answer 12

Ruffini’s corpuscles

Question 13

What mechanoreceptors are associated with hearing, equilibrium, and arterial pressure?

Answer 13

• Hearing
  
  • sound receptors of cochlea
• Equilibrium
  
  • vestibular receptors
• Arterial Pressure
  
  • baroreceptors

Question 14

True or False:

Some sensory receptors adapt either partially or completely to any constant stimulus after a period of time.

Answer 14

False - ALL sensory receptors adapt either partially or completely to any constant stimulus after a period of time.

**some receptors adapt to a far greater extent than others**

Question 15

What the four mechanisms of stimulation for receptors?

Answer 15

• Mechanical Deformation
• Application of a Chemical
• Temperature Change
• Electromagnetic Radiation

Question 16

What are the characteristics of tonic receptors?

Answer 16

• slow adapting
• detect continuous stimulus strength
• transmit impulses as long as stimulus is present

Question 17

Name the different types of tonic receptors.

Answer 17

• muscle spindles
• Golgi tendon organs
• macula and vestibular receptors
• baroreceptors
• chemoreceptors

Question 18

What are the characteristics of phasic receptors?

Answer 18

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

Question 19

What are the two main types of nerve fibers?

Answer 19

• Type A
• Type C

Question 20

What are type A nerve fibers further subdivided into?

Answer 20

• alpha
• beta
• gamma
• delta

Question 21

Is the type A nerve fiber myelinated, and what is its size compared to type C nerve fibers?

Answer 21

• Large and medium in size
• Myelinated fibers of spinal nerves

Question 22

What are the characteristics of Type C nerve fibers?

Answer 22

• small, unmyelinated fibers
• conduct signals at low velocity
• make up more than half of all sensory fibers in most peripheral nerves and all postganglionic autonomic fibers

Question 23

True or False:

Type C nerve fibers make up more than half of all sensory fibers in most peripheral nerves and all postganglionic autonomic fibers.

Question 24

What group and type of nerve fiber does fibers from annulospiral endings of muscle spindles?

Answer 24

Group Ia (Type A-alpha fibers)

Question 25

What nerve fiber group and type do fibers from the Golgi tendon organs arise?

Answer 25

Group Ib (Type A-alpha fibers)

Question 26

What group and type do cutaneous tactile receptors and flower-spray nerve fibers come from?

Answer 26

Group II (Type alpha, beta, and gamma fibers)

Question 27

Which group and type of nerve fibers carry temperature, crude touch, and pricking pain sensations?

Answer 27

Group III (Type alpha and delta fibers)

Question 28

Which group and type of nerve fibers carry pain, itch, temperature, and crude touch? Besides Group III (Type alpha and delta fibers).

Answer 28

Group IV (Type C fibers)

Question 29

What is temporal summation?

Answer 29

Increase signal strength by increasing frequency of nerve impulses in each fiber. \*refer to figure 47-8\*

Question 30

What is spatial summation?

Answer 30

Increasing signal strength is transmitted by using progressively greater number of fibers. * entire cluster of nerve endings from one pain fiber covers an area of skin referred to as the receptor field for that fiber * number of endings is large in center of field but is reduced in periphery * nerve endings from one pain fiber overlap those of other pain fibers

Question 31

List some examples of neurons that are associated with a "neuronal pool".

Answer 31

* cerebral cortex * basal nuclei * thalamic nuclei * cerebellum * mesencephalon * pons * medulla * gray matter of spinal cord

Question 32

What is the stimulatory field of a neuronal pool?

Answer 32

* neuronal area within the pool stimulated by each incoming nerve fiber * terminals for each input fiber lie on the nearest neuron in its field * fewer terminals for each input fiber lie on neurons further away

Question 33

What is the discharge zone of a neuronal pool?

Answer 33

Includes ALL the output fibers stimulated by the incoming fiber.

Question 34

What are the facilitated/inhibition zones of the neuronal pool?

Answer 34

* neurons further from the discharge zone that are facilitated but not excited * may be inhibitory or excitatory depending on the input fiber

Question 35

Name as many of the 9 somatic sensory endings that you can.

Answer 35

* free nerve endings * expanded tip receptor * tactile hair * Pacinian corpuscle * Meissner's corpuscle * Krause's corpuscle * Ruffini's endings * Golgi tendon apparatus * Muscle spindle

Question 36

What are diverging neuronal pathways in the neuronal pool?

Answer 36

* may result in amplification of initial signal * may allow transmission of original signal to separate areas \*\*In divergent circuits one incoming fiber triggers a response in a large number of new neurons which are part of the circuit. These circuits amplify the signal along the path and they are found in the sensory and well as motor system.\*\*

Question 37

What are converging neuronal pathways in the neuronal pool?

Answer 37

* multiple input fibers converge onto a single output neuron * input fibers may be from a single source or from multiple searate sources \*\*Converging circuits work in a manner that is reversed from that of diverging circuits. This circuit causes stimulation and inhibition. They are common in both the sensory as well as motor pathways.\*\*

Question 38

What are reverberatory circuits (oscillatory circuits) caused by?

Answer 38

Caused by positive feedback within neronal circuit.

Question 39

True or False: When a reverberatory circuit is stimulated it may discharge repetitively for a long time.

Answer 39

True