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BIO 353: Advanced Human Physiology > The Somatic Sensory System > Flashcards

The Somatic Sensory System Flashcards

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1
Q

Describe a general pathway of a sensory system.

A

Stimuli –> Selective receptor structures –> intracellular amplification of signal –> neuronal signal to CNS

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2
Q

Where does the CNS receive touch and proprioception information?

A

From sensory nerves

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3
Q

How does the CNS generate movements after receiving external stimuli information?

A

By sending signals to muscles via motor nerves

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4
Q

Describe common features of sensory systems (sensory coding).

A
  1. Sensor organs are filters - highly selective and sensitive
  2. Transduction - stimulus energy transformed into neural electrical activity
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5
Q

How do cells respond to stimuli?

A

They respond to weak stimuli of one particular type (modality) and only respond to small portion of that stimulus.

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6
Q

What is a simple receptor?

A

Neurons with free nerve endings (somatosensory)

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7
Q

What is a complex receptor?

A

Nerve endings enclosed in connective tissue capsules.

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8
Q

What are specialized sense receptors?

A

These are non-neural and release NT onto sensory neurons

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9
Q

How are neurons classified?

A

By structure, location, types of stimuli they respond to

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10
Q

What are graded potentials?

A

These are changes in membrane potential that vary in size, as opposed to all-or-none

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11
Q

Where and how do graded potentials occur? How long do they last?

A
  • Tend to occur in dendrites or soma of neuron
  • Arise from the summation of the individual actions of ligand-gated ion channel proteins and decrease over time and space
  • Size and duration are dependent on size and duration of stimulus
  • Decay with time and distance
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12
Q

What is depolarization in terms of a graded potential?

A

When the graded potential is just underneath or barely meets the threshold

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13
Q

What is an action potential in terms of a graded potential?

A

An action potential is when the graded potentials exceeds a threshold.

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14
Q

What is hyperpolarization in terms of a graded potential?

A

It is when the graded potential fails to meet the threshold.

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15
Q

Action potentials are created when graded potentials exceed a threshold. Describe how graded potentials might also exceed the threshold in order to create an action potential.

A

When graded potentials, such as depolarization and hyperpolarization occur at the same time, sometimes it can be enough to cause a graded potential to exceed the threshold and create an AP.

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16
Q

What is the definition of summation in terms of physiology?

A

The additive effect of several electrical impulses on a neuromuscular junction (junction between a nerve cell and a muscle cell)

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17
Q

Summation can be either…?

A

Temporal or spatial?

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18
Q

Describe spatial summation in three steps.

A
  1. Simultaneous stimulation by several presynaptic neurons
  2. EPSPs spread from several synapses to axon hillock
  3. Postsynaptic neuron fires
19
Q

What is an EPSP?

A

Excitatory post-synaptic potential

Makes it easier for the neuron to fire an AP

20
Q

What is an IPSP?

A

Inhibitory post-synaptic potential

When the resulting change in membrane voltage makes it more difficult for the cell to fire an AP (lowering the firing rate)

21
Q

Describe temporal summation in three steps.

A
  1. High frequency stimulation by one presynaptic neuron
  2. EPSPs spread from one synapse to axon hillock
  3. Postsynaptic neuron fires
22
Q

What are the somatic senses?

A

Touch, proprioception, temperature, and nociception

23
Q

What is proprioception?

A

The sense of body position perceived on both conscious and unconscious levels

24
Q

What is the organ of perception for position sense?

A

The sensory cortex of the brain

25
Q

What is nociception?

A

The normal processing of pain

26
Q

Describe the steps required to reach the somatic sensory cortex of the brain for nociception, temperature and coarse touch.

A
  1. Pain, temperature, and coarse touch cross the midline int he spinal cord
  2. Sensory pathways synapse in the thalamus
  3. Sensations are perceived in the primary somatic sensory cortex.
27
Q

Describe the steps required to reach the somatic sensory cortex of the brain for fine touch, vibration and propioception.

A
  1. Fine touch, vibration and proprioception pathways cross the midline in the medulla
  2. Sensory pathways synapse in the thalamus
  3. Sensations are perceived in the primary somatic sensory cortex
28
Q

What is topographical organization?

A

Point-to-point representation of a sensory surface in the brain.

29
Q

What is adaptation?

A

Reduction in sensitivity due to a constant stimulus

30
Q

What is peripheral adaptation?

A

Receptors respond strongly at first and then decline

31
Q

What is central adaptation?

A

Adaptation within the CNS

-Being consciously aware of a stimulus, which quickly disappears

32
Q

What are examples of somatic senses?

A

Temperature, proprioception, pain, touch

33
Q

How are somatic senses different than other senses?

A

Receptors are widely distributed throughout the body. Receptors respond to different stimuli

34
Q

What are the three sensations detected by skin?

A

Mechanoreception, thermoreception, nociception

35
Q

What is mechanoreception?

A

Vibration, soft touch, pressure

36
Q

What are thermoreceptors?

A

Temperature, nociceptors, pain: mechanical, chemical, thermal

37
Q

What does a smaller receptive field mean?

A

Greater acuity (two-point discrimination)

38
Q

What happens if there is damage to a dorsal root ganglion?

A

Sensation is not lost in that dermatome because of overlapping segments

39
Q

What is Shingles?

A

Herpes zoster virus reactivated in neurons of a single dorsal root ganglion - leads to increased excitability in sensory neurons, spontaneous firing

  • Usually limited to one dermatome
  • Constant pain
40
Q

What is agnosia and why does it occur?

A

Tacticle agnosia is when someone cannot recognize common objects by feeling them. They can recognize by sight and sound but not touch.

Caused by damaged to posterior parietal cortex

41
Q

What is a phantom limb?

A

Sensation that an amputated limb is still attached to the body and is moving appropriately with other body parts

42
Q

What happens to the somatosensory cortex after the loss of a limb?

A

Undergoes substantial reorganization after the loss

43
Q

Why might rubbing your elbow after bumping it reduce your pain?

A

Because another input has been added due to mechanoreceptors. You can actually cancel out the pain.

44
Q

What is referred pain?

A

Multiple nociceptors from different regions converge on the same ascending tract in the spinal cord

BIO 353: Advanced Human Physiology (9 decks)

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