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PMP101 - Health, Disease and Patient > The somatosensory nervous system > Flashcards

The somatosensory nervous system Flashcards

1
Q

What are the general senses divided into and where?

A

*somatic - in skin, muscles + joints
*visceral - in internal organs

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2
Q

What are some examples of somatic senses?

A

*touch
*temperature
*pain
*pressure
*proreception

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3
Q

What are some examples of visceral senses?

A

*pain
*pressure

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4
Q

What do mechanoreceptors respond to?

A

ear, muscle and joints, skin and viscera,
cardiovascular

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5
Q

What do chemoreceptors respond to?

A

tongue, nose, skin and viscera

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6
Q

What do photoreceptors respond to?

A

eye

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7
Q

What do thermoreceptors respond to?

A

skin and CNS

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8
Q

What do notice receptors respond to?

A

respond to stimuli that result in
sensation of pain

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9
Q

Where are exoreceptors located and what do they respond to?

A

Exteroreceptors = body surface
* (pain, touch, pressure, temperature) and
special senses (vision, hearing, equilibrium ,
taste, smell)

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10
Q

Where are interoreceptors located and what do they respond to?

A

Interoreceptors (visceroreceptors) = within
the body,
* viscera and blood vessels (stretch,
temperature)

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11
Q

Where are propireceptors located and what do they respond to?

A
  • Proprioreceptors = respond to internal
    stimuli.
  • Skeletal muscle, joints, tendons,
    ligaments and connective tissue.
    Advise brain of body movements
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12
Q

What is a sensory unit?

A

A sensory unit is a single
afferent neuron and all of its
receptor endings

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13
Q

What might a sensory unit contain?

A
  • Sensory receptors may be
  • Neuron with free nerve
    endings
  • Neuron with
    encapsulated ending
  • Specialised receptor
    cells closely associated
    with neuron
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14
Q

Describe the process of a sensory response to the environment changing

A
  • Environmental changes cause a change in membrane potential in
    receptor
  • Receptor or generator potential : graded
  • If this reaches threshold it will trigger an action potential, sensory
    transduction
  • This information goes to the brain via
    ascending fibres, primary then secondary
    afferent nerve fibres
  • Each nerve may receive information from a
    number of receptors in a particular area =
    receptive field
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15
Q

How does stimulus intensity change threshold/ effect?

A
  • The stronger the
    stimulus, the larger
    the graded receptor
    potential, the more
    frequent the action
    potentials of the
    afferent neuron, the
    more
    neurotransmitter is
    released at the
    synapse
  • AP is not graded
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16
Q

Describe what a receptive field is and how it differs + brain recgnition

A
  • Region of space where the presence of a
    stimulus will induce the production of a
    signal in that neuron
  • Several sensory neurons may have
    overlapping receptive fields
  • The smaller the receptive fields, the more
    accurate a representation of the stimulus is
    signaled to the brain
  • Brain cannot differentiate between two
    stimuli acting on the same receptive field
  • Tested clinically to test for damage : Two
    point discrimination task
17
Q

Briefly summarise the somatosensory pathways

A
  • Somatic nervous system - linked to skeletal muscles
  • Gives us perception of touch, temperature, body position, pain
  • Process stimuli received from receptors within the skin, muscles, and joints
  • Mostly mechano, thermo- and chemoreceptors
  • Responses voluntary AND involuntary
  • Reflexes, breathing
  • Pathways for Somatic Perception Project to the Cortex and Cerebellum
18
Q

What are the sensory receptors in skin?

A

*free nerve endings
*merkel corpuscle
*meissners corpuscle
*pacinian corpuscle
*ruffini corpuscle

19
Q

What do free nerve endings detect?

A
  • Temperature, noxious
    stimuli, hair movement
  • Dermis
20
Q

What do the corpuscles detect?

A
  • Merkel corpuscle
  • Steady Pressure,
    texture
  • Epidermal – dermal
    junction
  • Meissners corpuscle
  • Flutter, light pressure
  • Dermis (papillary)
  • Pacinian Corpuscles
  • Vibrations
  • Deep dermis/
    subcutaneous
  • Ruffini corpuscles
  • Stretch
  • Dermis
21
Q

Where do the somatosensory pathways take the signal?

A

Somatosensory pathways take the message
to the spinal cord and brain – somatosensory
cortex

22
Q
A
  • 2 Afferent pathways to the
    brain
  • Sensory input enters the
    spinal cord through the
    dorsal horn
  • Dorsal column lemniscal for
    fine touch, vibration and
    position
  • Spinothalamic for crude
    touch temperature, and
    pain
  • Three neurons which
    synapse in the spinal cord
    (1) and in the thalamus (2)
  • Cross the midline in the
    CNS/spinal cord
  • Terminate in the
    somatosensory cortex
  • Somatotopic representation
23
Q

How does the sensory homunculus work?

A
  • The amount of space on the somatosensory cortex devoted to each body part is proportional to the
    sensitivity of that part
  • Face fingertips tongue hands genitalia
24
Q
A

2 Efferent pathways to the muscles
* Dorsolateral corticospinal tract
* To periphery (toes, hands):
* Ventromedial corticospinal tract
* To shoulders/neck/truck
* 2 neurons which synapse with each
other in the spinal cord
* Cross the midline in the spinal cord
* Terminate at the neuromuscular
junction with skeletal muscle
* Somatotopic representation in the
motor cortex

25
Q
A
  • A reflex pathway is commonly known as a reflex
  • Simple somatic reflexes do not include the higher centres discussed for
    conscious or voluntary aspects of movement.
  • An automatic, involuntary, consistent response
  • Reflexes can be spinal or cranial, depending on the nerves and central
    components that are involved.
  • Sensors detect external stimuli and sensory neurons sends an impulse to the
    spinal cord.
  • Interneurons relay the information immediately back to the motor neurons
    which causes movement.
  • No thought is involve
26
Q

What are the five components to the sensory reflex arc?

A

*receptor
*afferent neurone
*integration centre
*efferent neurone
*effector organ

27
Q

What is an example of a withdrawl reflex?

A
  • ipsilateral (excites muscles on same side)

PMP101 - Health, Disease and Patient (25 decks)

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