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A. White- Human Physiology > General Sensory Mechanisms III > Flashcards

General Sensory Mechanisms III Flashcards

1
Q

What type of potential do receptors create?

A

A local, decremental potential that is essentially a local potential.

If the potential is strong enough (through summation), it may generate an action potential at the first node of Ranvier on the primary sensory neuron.

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2
Q

most pathways are made up of three neurons. What are these neurons?

A

Primary neurons

Secondry neurons

Tertiary neurons

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3
Q

Where do primary neurons originate from?

A

Peripheral receptors, such as Merkel’s receptors.

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4
Q

Where do primary neurons enter the spinal cord?

A

Via dorsal roots of the spinal (cranial) nerves.

They synapse in the spinal cord with secondary neurons.

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5
Q

Where do secondary neurons originate?

A

In the spinal cord gray matter.

They travel through the spinal cord in one of the myelinated columns.

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6
Q

Where do secondary neurons synapse?

A

The thalamus.

They synapse with tertiary neurons.

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7
Q

Where do tertiary neurons travel through?

A

The internal capsule.

It is a myelinated pathway between the thalamus and some of the basal nuclei.

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8
Q

Where do tertiary neurons synapse?

A

In the somatosensory cortex.

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9
Q

What is two-point discrimination touch?

A

It refers to the ability to distinguish two separate points as close as 2 millimeters apart.

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10
Q

Where does two-point discrimination touch travel?

A

In the dorsal column-medial lemniscal pathway.

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11
Q

What is the importance of lateral inhibition?

A

It blocks the lateral spread of excitatory signals, thereby increasing the degree of contrast in the cerebral cortex.

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12
Q

Where does lateral inhibition occur?

A

Dorsal column nuclei

Ventrobasal nuclei of thalamus

Somatosensory cortex

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13
Q

What is a pathway that carries two point discrimination touch?

A

Dorsal column-medial lemniscal pathway.

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14
Q

What is the pathway of the dorsal column-medial lemniscal pathway?

A

Peripheral receptors -> spinal nerve -> dorsal root of spinal nerve -> spinal cord

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15
Q

What are two regions that the dorsal column-medial lemniscal system travels through?

A

The thalamus to the somatosensory cortex. This is associated with secondary neurons.

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16
Q

The transmission of a pinpoint stimulus signal to the cerebral cortex requires synapses. Generally, the more synapses, the ___ the stimulus.

A

Stronger

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17
Q

Without lateral inhibition, how would a stimulus be felt?

A

It would be perceived only as one point instead of two.

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18
Q

Where do axons from the lower limbs travel?

A

In the medial portions of the dorsal columns.

Each of these areas of dorsal columns is called the fasciculus gracilis.

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19
Q

Where do axons from the upper limbs travel?

A

In the lateral portions of the two dorsal columns.

Each of these areas of the dorsal columns is called the fasciculus cuneatus.

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20
Q

Where do aons in the fasciculus gracilis synapse?

A

In the lower medulla in the nucleus gracilis.

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21
Q

Where do axons in the fasciculus cuneatus synapse?

A

In the lower medulla in the nucleus cuneatus.

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22
Q

What are the medial lemniscus?

A

Secondary neurons that travel through the brain stem as paired tracts.

23
Q

Where do secondary neurons synapse?

A

In the basolateral nucleus of the thalamus with tertiary neurons.

24
Q

Where do tertiary neurons travel through?

A

The internal capsule to the somatosensory cortex.

25
Q

What neurons decussate?

A

Secondary neurons

26
Q

What is fast pain generally elicited by?

A

Mechanical and thermal stimuli.

It is typically carried by Adelta pain fibers.

27
Q

Where do fast pain fibers terminate?

A

In lamina I of the dorsal horns of the spinal cord.

28
Q

What is slow pain?

A

Aching, slow burning, throbbing, nauseous and chronic.

It may be elicited by mechanical, thermal and chemical stimuli.

29
Q

What type of fibers carry slow chronic pain?

A

Type C fibers.

They mostly terminate in layers II and III of the dorsal horns of the spinal cord.

30
Q

Pain travels through what type of pathways?

A

Anterolateral pathways.

31
Q

Where do primary pain fibers synapse?

A

In the dorsal horns of the spinal cord (layers 1, 2, or 3) with the secondary fibers.

The secondary fibers immediately decussate and make up the anterolatera pathways.

32
Q

Fast pain fibers make up what type of tracts?

A

Neospinothalamic tracts.

They synapse and terminate the ventrobasal nuclei of the thalamus.

33
Q

Where do tertiary fibers ascend to?

A

The somatosensory cortex.

34
Q

What type of pain fibers make up the paleospinothalamic pathway?

A

Slow pain fibers.

35
Q

Where do most of the paleospinothalamic secondary fibers terminate?

A

Throughout the brainstem, although some pass all the way to the thalamus.

36
Q

What neurotransmitter is used by the A delta fibers of the fast-pain pathway?

A

Glutamate

37
Q

What do type C fibers of the slow, chronic-pain path release?

A

Glutamate and substance P.

Glutamate acts instantaneously, but substance P is released more slowly.

38
Q

What does Brown-Sequard syndome occur as a result of?

A

A hemisection of the spinal cord.

All motor functions are blocked on the side of the transection in all segments below the level of the transection.

39
Q

You encounter a patient who has a transection of the right spinal cord. Sensation so f pain, heat and cold are lost on the left side of the body below the transection. They also have a loss of kinesthetic and position sensations, vibration sensation, and two point discrimination. What does the patient most likely have?

A

Brown-Sequard syndrome

40
Q

In Brown Sequard Syndome, dorsal column sensation is lost on the ___ side of transcetion below the level of transection.

A

Same

41
Q

Where do pain fibers synapse?

A

In the reticular formation.

Parts of it go to the thalamus.

42
Q

What are the three major components of the analgesia system?

A

Periaqueductal gray and periventricular regions of the brainstem and third ventricle

Raphe magnus nucleus and reticular nuclei in medulla.

Pain inhibitory complex in dorsal horns of spinal cord.

43
Q

What is the function of the analgesia system?

A

It is a pain control system

44
Q

What is the function of an enkephalin neuron?

A

It suppresses pain by inhibiting synapses of primary and secondary neurons.

45
Q

What are the three types of receptors that discriminate thermal gradations?

A

Cold

Warmth

Pain

46
Q

What are warmth nerve endings mainly transmitted over?

A

C-tyep fibers.

47
Q

What are cold and warmth receptors thought to be stimulated by?

A

Changes in their metabolic rates.

Thermal signals are transmitted in pathways parallel to those for pain signals.

48
Q

What is referred pain?

A

Pain that occurs when visceral pain fibers are stimulated and stimulate some of the pain fibers that conduct pain signals from the skin.

49
Q

What conditions result in severe pain?

A

Severe pain results when there is diffuse stimulation of pain nerve endings throughout the viscera.

Such diffuse pain can result from ischemia.

50
Q

All visceral painf rom the thoracic and abdominal cavities is transmitted via what type of pain fibers?

A

Type C pain fibers.

51
Q

What are headaches the result of?

A

Pain referred to the surface of the head from deep head structures.

52
Q

True or false: the brain itself is almost completely insensitive to pain.

A

True

53
Q

How are receptor potentials created?

A

By opening “modality” gated channls such as sodium channels that are opened in response to membrane deformation caused by the touch or pressure.

A. White- Human Physiology (32 decks)

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