Week 9 - Sensory Processing

Question 1

What are mechanoreceptors

Answer 1

specialized sensory cells that respond to mechanical forces like pressure, touch, vibration and stretch. They generate nerve impulses when they, or surrounding tissues are deformed by mechanical stress e.g. touch, pressure (including blood pressure), vibration and stretch (also involved in special senses of hearing and balance)

Question 2

What are thermoreceptors

Answer 2

specialized sensory receptor that are sensitive to temperature changes (warm and cold)

Question 3

What are photoreceptors

Answer 3

specialised sensory receptors in the retina of the eye which is sensitive to light energy

Question 4

What are chemoreceptors

Answer 4

sensory receptors that detect chemical changes in the environment. They respond to specific molecules or chemical conditions like taste, smell, - it controls respirator and cardiovascular function.

Question 5

What are nociceptors

Answer 5

receptors that respond to stimuli that detect pain. Their job is to sense anything that could damage your body like extreme heat, sharp objects, strong chemicals or intense pressure and send warning signals to your brain. They have free nerve ending.

Question 6

Define sensation

Answer 6

the raw data input from eyes, ears, skin ect

Question 7

Define perception

Answer 7

Perception determines how we will respond to stimuli – there may also be a learning component as well. Perception is the brain’s interpretation of information it gets from its senses.

Question 8

what are the 3 steps in the traditional view of how pain works

Answer 8

1. Receptors
2. Processing in central pathways
3. Conscious Perception
   *Notes: Pain processing is more complex than this but this is a good template for considering sensory processing and perception

Question 9

what is modality

Answer 9

the type of energy or stimulus a receptor detects e.g. light for vision or sound for hearing

only a particular type of stimulus will stimulate a specific sensory receptor (most of the time)

Question 10

What is receptive field

Answer 10

the specific area where a stimulus has to happen to activate a particular receptor (or sensory neuron)

the stimulus must be within the area that a particular sensory receptor is monitoring

Question 11

What are the steps in receptors when pain is processed

Answer 11

1. noxious (harmful) stimulus (heat, pressure, chemical) activates nociceptors
2. energy of the stimulus is converted into a graded electrical response within the receptor (receptor potential)
3. membrane depolarisation accumulates to form an action potential referred to generator potentials
4. When generator potential reaches the threshold it it opens the voltage gates Na+ ion channels
5. the frequency of action potentials tells the brain how intense the stimulus is - more frequent firing = more intense pain (most sensory receptors can adapt (change sensitivity over time)

Question 12

What are phasic receptors

Answer 12

• receptors what react fast to stimulus
• give bursts of impulses at the beginning and the end of a stimulus

Example: You stop noticing your watch on your wrist after a few minutes

Question 13

What are tonic recptors

Answer 13

• continues to fire steadily as long as the stimulus is present
• provides little to no adaptation

Example: You keep feeling pain from an injury until it’s healed

Question 14

what type of receptor are most proprioceptors

Answer 14

tonic

Question 15

what type of receptor are nociceptors

Answer 15

tonic receptors
nociceptors don’t adapt — they stay active and often become more sensitive over time (this is why pain can worsen or linger).

Question 16

what are the 3 types of sensory nerves on the circuit level

Answer 16

• first order (primary sensory nerves)
• second order sensory nerves
• third order sensory nerves

Question 17

What are first order (primary sensory nerves)

Answer 17

• Runs from the periphery to the dorsal horn
• function to carry information from the sensory receptors to the central nervous system

lie in the dorsal root ganglia, and the central processes enter the dorsal horn of the spinal cord

Some branches of these primary nerves may be involved in local or spinal reflexes whilst other synapse with second order sensory nerves

Question 18

What are second order sensory nerves

Answer 18

associated with the ascending sensory pathways that run to the thalamus
- pass information from the spinal cord up to the thalamus (or cerebellum in some cases)
- extends from dorsal horn to thalamus or cerebellum

Question 19

What are third order sensory nerves

Answer 19

cell bodies reside in the thalamus conduct impulses to the somatosensory cortex for conscious perception

Question 20

What are the steps of pain perception on the circuit level

Answer 20

1. Signals travels along the axon of the nociceptor (primary sensory neuron) toward the spinal cord
2. The sensory neuron enters the dorsal horn of the spinal cord where it synapses with a second order neuron. Here neurotransmitters like substance P and glutamate are released to continue the signal
3. The second order neuron crosses over the opposite side (decussates) and ascends in the spinothalamic tract of the spinal cord
4. A third order sensory neuron carries the signal from the thalamus to the somatosensory cortex which is located in the postcentral gyrus of the parietal lobe
5. The primary somatosensory cortex interprets: location of the pain, intensity of the pain, type of pain and give you conscious awareness of the pain

Question 21

What is the ascending pathway

Answer 21

The ascending pathway refer to the neural routes that carry sensory information from the body to the brain including pain, touch, temperature and proprioception.
- associated with second order sensory nerves

Question 22

What are the 3 main ascending pathways in the spinal cord

Answer 22

1. Nonspecific pathways (anterolateral - anterior and lateral spinothalamic tracts)
2. Specific pathways (medial lemiscal)
3. Spinocerebellar tracts

Question 23

What is the Nonspecific pathways (anterolateral – anterior and lateral spinothalamic tracts)

Answer 23

• Ascending pathway
• Pain, temperature and course touch
• Sensations we have difficulty in precisely localising
• Involved in emotional aspects of perception

Question 24

What are the order of steps in the spinothalamic (AL) pathway

Answer 24

• periphery
• dorsal horn
• immediate decussation
• thalamus
• somatosensory
• sensation

Question 25

What is the Specific pathways (medial lemniscal)

Answer 25

- type of ascending pathway - Mediates precise information from a single type of sensory receptor that can be precisely localised on the body surface - From the thalamus, impulses are relayed to specific areas of the somatosensory cortex

Question 26

What are the order of steps in the specific pathway (medial lemniscal pathway)

Answer 26

- peripheral - medualla - immediate decussates - thalamus - primary somatosensory cortex - sensation

Question 27

What is a spinocerebellar tract

Answer 27

- type of ascending pathway - Convey information about muscle or tendon stretch, as well as proprioceptive information - These pathways do not contribute to conscious sensation - Information used to coordinate skeletal muscle activity

Question 28

What are the order of steps in the spinocerebellar tracts

Answer 28

- periphery - dorsal horn dorsal spinocerebellar tract (ipsilateral - doesn't decussate) Ventral spinocerebellar tract - first decussation in the spinal cord, second decussation in the cerebellum - cerebellum (terminates in the cerebellum not the cortex so no third order neuron or conscious sensation)

Question 29

Interpretation of sensory information occurs where

Answer 29

cerebral cortex

Question 30

What occurs at the perceptual level

Answer 30

- sensory information is interpretated in the cerebral cortex - interpretation relies on where the signal came from not the signal itself (all action potentials are the same) - the nature of the nerve that sent the signal tells us what the message is about (pain, touch, warm ect) - the precise area in the sensory cortex that receives the signal tells you where that signal came from - projection

Question 31

What are features associated with perception

Answer 31

1. Perceptual detection – ability to detect that a stimulus has occurred – will normally only happen when you get the summation of several receptor impulses 2. Magnitude estimation - How intense is the stimulus - Frequency coding 3. Spatial discrimination - Identifying the site or pattern of stimulation - Varies between body areas 4. Feature abstraction - Our ability to build up more complex patterns of sensation - Can combine a mixture of sensations – warm, soft, smooth ect to build more complex patterns of sensation 5. Quality discrimination - The ability to identify the different modalities of a particular sense e.g. with taste, sweet or salty 6. Pattern recognition - Our ability to recognise familiar patterns, novel patterns ect - For example, building up a picture from a series of dots or micro images

Question 32

What is the function of the thalamus in pain perception

Answer 32

- thalamus is the major sensory relay station - afferent (sensory impulses from all senses converge in the thalamus - it sorts, edits and packaged information relaying it to appropriate areas of sensory cortex as well as non cortical structures - when impulses reach the thalamus we have a crude recognition of the sensations - pleasant or unpleasant

Question 33

are nociceptive nerves first order, second order or 3rd order nerves

Answer 33

First order sensory neurons - they are the initial neurons that detect a stimulus - their cell bodies are located in the dorsal root ganglia