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HUBS191 - Module #2 - Nervous > Lecture #28 - More nervous system > Flashcards

Lecture #28 - More nervous system Flashcards

1
Q

What does the CNS and PNS consist of?

A

Central: brain + spinal
Peripheral: Cranial and spinal nerves

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2
Q

Three types of neurons

A
  1. Multipolar (cell body separates the reception going away parts)
  2. Bipolar (hv bipolarity)
  3. (Pseudo)unipolar
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3
Q

Name me the 5 special and 4 somatic & visceral sensations

A

Special:

  1. Vision
  2. Hearing
  3. Taste
  4. Smell (and pheromones)
  5. Vestibular (balance)

Somatic and visceral sensations (physical motion of body surface)

  1. Touch
  2. Pain
  3. Warm & cold
  4. Body position (proprioception - relating to stimuli that are produced and perceived within an organism, especially those connected with the position and movement of the body)
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4
Q

What are the three ways the senses are input-ed to the CNS?

A
  1. Direct (e.g. hypothalamic temp sensing)
  2. Endocrine (e.g. control of food intake) - detect hormone
  3. Nervous
    - Somatic
    - Visceral
    - Special
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5
Q

Sensory receptors

A

Sensory ending of an afferent neutron (to CNS) = SOMATIC SENSATION

Specialised receptor cell (and then afferent neuron to CNS) = SPECIAL SENSES (mostly - nose is an exception and the entire axon goes to brain)

Sensory receptors: highly sensitive to particular stimulus

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6
Q

Conscious sensations (three parts)

A
  1. INTEGRATION CENTRE
    - cerebral cortex
    - conscious sensation and perception (multiple types of sensations brought together)
  2. AFFERENT NEURONS
    - peripheral nerve (PNS)
    - tract or pathway (CNS)
  3. SENSORY RECEPTOR
    -sensory stimulus converted into action potentials
    =TRANSDUCTION
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7
Q

4 types of info that describes a sensory stimulus

A
  1. MODALITY - type of sensory receptor activated (what kinda transduction can the axon do?) type of sensation detected or encoded by sensory nerve
  2. INTENSITY - frequency of action potential firing in afferent neurons (how many AP over time)
  3. DURATION - duration of action potentials firing in afferent neurons
  4. LOCATION - location of sensory receptor(s) activated, “mapped” in brain
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8
Q

Stimulus modality modality: proprioception (body position and posture)

A
  1. Length receptors
    - Muscle spindles (length detectors in muscles)
    - stretch reflex
    - shortening of muscle
    - Posture (of someone shoves you - change in length detected by spindle and response and stay upright)
  2. Tension receptors (under tendon - at ends)
    - Golgi tendon organ
    - tension reflex
    - relaxation
    - Protects from tearing

When tap tendon –> you tug on muscle –> muscle spindle notices change length - part of motor control system

Golgi detects how much tension being generated = how much stretch being applied

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9
Q

Stimulus modality: touch (7 types)

A
  1. Free nerve endings: PAIN
    - chemoreceptors detect changes in environ w/ actual/impending tissue damage
    - in every organ
  2. Krause’s end bulb: TOUCH (textural sensation)
  3. Pacini’s corpuscle: TOUCH (deep pressure/high frequency vibration)
    - texture of surface when you’re pressing on rather hard bc deeply buried so need more pressure
  4. Meissner’s corpuscles: TOUCH (low frequency vibration)
    - detech changes in pressure - stop firing after some time bc duration)
  5. Ruffini’s corpuscle: TOUCH (crude, persistent)
    - detect stretch in different directions esp palm
    - arranged in diff directions
  6. Merkel endings: TOUCH (light pressure)
  7. Sensory axons: can detect movements in air when hair move (cover hair)

NOTE: vibration = actually texture detectors!

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10
Q

Higher stimulus……

A

Increasing stimulus increases action potential frequency

More depolarisation in relative refractory period - can AP if stimulus big enough so can increase frequency of AP

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11
Q

Stimulis duration (2)

A
  1. Sensory receptors are most sensitive to change
  2. Often show adaptation: decreased receptor potential overtime in response to continuous stimulation
Fast:
Touch receptors (e.g. we don't feel clothes on skin after some time bc AP stopped)
Slow:
Pain receptors (free nerve endings) or stretch receptors (muscle spindle) - takes long time to adapt if at all adapt
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12
Q

Stimulus location: receptive field

A

Receptive field

  • Region of space in which a stimulus can be lead to activity in a particular afferent neutron
  • Small fields & dense innervation gives good discrimination
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13
Q

Afferent pathway for touch and posture: MEDIAL LEMNISCAL (dorsal column) PATHWAY

A
  1. Three neurons in relay
  2. “Up and Across”
    e. g. sensory neurons from muscle spindles - fastest neurons in body
  3. Primary sensory neuron - into dorsal root
  4. Secondary sensory neuron - in medial lemiscus
  5. Tertiary sensory neuron - in somatosensory area of cerebral cortex

1st cell body in dorsal root at bottom
2nd cell body in medulla (synapse there - crosses over)
3rd cell body in thalamus (synapse with third neuron)
This goes to primary somatosensory cortex

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14
Q

Somatosensory cortex

A
  1. Sensation
    - conscious identification of “what and where”
    - primary region of cortex
    - POST CENTRAL GYRUS (primary somatic sensory area)
    - first info goes here
  2. Perception
    - meaningful interpretation
    - association (secondary) region of the cortex
    - JUST BEHIND CENTRAL GYRUS (somatic sensory association area)
    - different sensations brought together to be synthesised
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15
Q

Somatotopic organisation

A

Post-central gyrus

Areas of cortex correspond to areas of the body
Densely innervated = large region of cortex

LEFT REPRESENTS RIGHT

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16
Q

Stimulus modality: pain

A

-Sensed by free nerve endings (nociceptors)

  1. Fast (acute) pain
    - small receptive field
    - largish, myelinated afferent axons (A fibres)
    - somatic pain e.g. skin surface
  2. Slow (chronic) pain
    - large receptive feild
    - small, unmyelinated axons (B fibres) (`1m/s)
    - visceral pain e.g. organ
17
Q

Afferent pathway for pain

LATERAL SPINOTHALMIC PATHWAY

A
  1. Minimum of 3 neurons in relay (can have interneurons)
  2. Neurons go “Across and Up”
  3. Primary sensory neuron in dorsal root immediately synapse with another neuron when get to spinal to get to other side (“across”)
  4. Along the way, collateral fibres to reticular formation - arousal - wakes cortex up
  5. Through lateral spinothalmic tract goes the secondary neutron
  6. Connected to limbic system also - emotional component
  7. Another synapse in thalamus (none in medulla)
  8. Teritary sensory neuron to somatic sensory srea of cerebral cortex.

HUBS191 - Module #2 - Nervous (10 decks)

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