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Gross Anatomy II > General Somatosensory Afferents Of The Spinal Cord > Flashcards

General Somatosensory Afferents Of The Spinal Cord Flashcards

1
Q

What is interoreception?

A

Ways that the nervous system receives information about the internal environment eg: broken bones, sensory for pain within body

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2
Q

What is proprioception?

A

Ways that the nervous system receives information about the position and movement of the body ( where the limbs are in space)

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3
Q

What is GVA?

A

General visceral afferent -> sensory from the autonomic nervous system

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4
Q

What is GSA?

A

General sensory afferent: somatosensation

  • sensory from the skin and skeletal muscle
  • senses touch, pain, temperature, position of the body
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5
Q

What are the types of stimulation a receptor can respond to?

A 
Mechanoreception - physical deformation
Thermorecetion - heat and cold
Nocireception - noxious stimuli
Photoreception - vision
Chemoreception - chemical change (taste, smell, O2/CO2 in the blood)
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6
Q

What are the possible destinations for afferents?

A

Cortex
Cerebellum or individual spinal cord segments
ARAS (wakefulness) this is a noxious stimuli that will help keep you awake

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7
Q

What is divergence and parallel processing of afferent information?

A

Divergence - the same sensory information is sent to multiple destinations for different purposes.
Parallel processing - different aspect of the same sensory experience are perceived in different parts of the brain at the same time
In short, divergence happens so that parallel processing can occur

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8
Q

What is a somatosensory pathway?

A

Receptors - transduction of neuronal activity
Action protein trials in first degree neuron - goes from periphery to CNS
First degree to multiple second degree neurons in the CNS
- excitatory or inhibitory
- for reflexes or supra segmental structures
Axons ascend to brain in fiber tracts
- clinical significance of the tract position
- tracts named for their origin (prefix) and termination (suffix) eg spinothalamic, vestibulospinal
- most will de usage at some point

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9
Q

What is the thalamus to the cortex used for/ what does it do?

A
  • relay and processing point for all sensations destined for conscious perception
      • vision, audition, somatosensation
  • projects to the primary sensory cortex involved with that specific sensation
  • somatosensory inputs go to the contralateral thalamus/cortex
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10
Q

How are receptive fields organized and why?

A

They involve both excitatory and inhibitory signals
Top: primary afferents (excitatory neurons) converging on second order neuron
– receptive field is equal to the combined receptive fields of the three primary afferents shown
Bottom: inhibitory neurons surround the receptive field of excitatory neurons. This enhances the contrast of the stimulus
– this helps distinguish where a stimulus is and where it isn’t.

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11
Q

What is somatotophy and what has it?

A

Sensory pathways have somatotophy
– info traveling in the NS retains spatial relationships of the receptors in the periphery
– receptor density in the periphery = the amount of space in the thalamus and cortex dedicated to that sensation -> map gets distorted
Some areas of the body are more sensitive than others
– due to higher density of receptors with smaller receptor fields
– more input = more cortical space devoted to the area for perception

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12
Q

What is exteroreception

A

Ways that the nervous system receives information about the external environment eg: touch
- the body being able to tell what is going on with the outside environment

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13
Q

what is the auditory pathway(s)?

A

cochlear hair cells of CN VIII -> cochlear nuclei -> caudal colliculus (Fibers that terminate here are for startle reflex) -> thalamus (medial geniculate nucleus?)-> auditory cortex for concious perception of sound -> primary auditory pathway

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14
Q

What is the startle reflex?

A
  • Fast motor response elicited if tactile, vestibular or acoustic stimulus has a sudden onset and exceeds certain intensity threshold
  • Descending pathways of this reflex to LMNs of skeletal muscles of the limbs
  • cause flexion of almost all skeletal muscle
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15
Q

Why does the body need a startle reflex?

A
  • Protection from physical impact
  • Interrupt behavioral patterns
  • Facilitate flight response
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16
Q

What are the types of deafness?

A
  • conduction deafness

- Sensorineural deafness

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17
Q

What is conduction deafness?

A

•Sound can’t get from the ear to the vestibular window due to damage, disease or obstruction

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18
Q

What is sensorineural deafness?

A
  • Sounds gets to the vestibular window but can’t transmit the sound to the auditory cortex usually due to damage to the cochlea, cochlear nerves or central pathways or auditory cortex
    • You can have inherited deafness and deafness form old age (presbyscusis) and both are usually irreversible
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19
Q

Why is subtotal loss of hearing in animals difficult to detect?

A

due to contralateral pathways and the redundancy

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20
Q

What does the vestibular system do?

A

•Involved in motor pathways
•Complex and concerned with maintaining a stable orientation in relation to gravity and motion
•Senses balance and acceleration which are varieties of body position (special form of proprioception)
–Position of eyes, neck, trunk and limbs in reference to movement or position of the head
–Rarely are we conscious of the normal operation of the vestibular system

21
Q

What does the vestibular nerve form from?

A

the axons of neurons from the utricle, sacule and semicircular canals

22
Q

The vestibular portions of CN VIII go to the vestibular nuclei in the hindbrain. Information coming in to the vestibular nuclei from both sides are integrated. How does this aid balance/positioning?

A

–The asymmetry of the inputs is what drives the reflexes to re-orient the body (balance the body)
–When one side isn’t transmitting information (a lesion is present), the cortex doesn’t know it is supposed to be responding

23
Q

Information from the vestibular nuclei goes to what motor nuclei for control of eye movements? What is this known as?

A

motor nuclei of CN III, IV, and VI

- known as the vestibulo-occular reflex

24
Q

Why does information from the vestibular nuclei go to the cerebellum?

A

for posture and balance to be modified as needed

•Vestibulo-spinal reflexes (trunk) and vestibulocollic reflexes (head and neck)

25
Q

What are the vestibular pathways and what do they do?

A

–Motor nuclei of III, IV, and VI (control of eye movements)
–The cerebellum for posture and balance to be modified as needed (postural muscles)
–Thalamus (relay center) and then to the cortex (conscious perception of movements)

26
Q

What is “tracking” with regards to the vestibulo-ocular reflex?

A

•Slow movement of the eyes as they are catching up to movement of the head (a type of nystagmus) “tracking”
–This normally happens during head movement
–You are going to have a fast phase and a slow phase

27
Q

What is resting nystagmus or positional nystagmus a sign of?

A

a sign of vestibular problems/disease because it is not normal

28
Q

What is estropia? What can it cause?

A

crossed eyes

- can cause a type of physiological nystagmus in Siamese/Himalayan cats

29
Q

What does a unilateral lesion with regards to the vestibulo-ocular reflex and nystagmus cause?

A

one side fires, the other does not (partial or not at all) = abnormal (resting nystagmus)
–Fast phase is going to be away from the lesion (towards the intact side)
–Fast phase and slow phase (named for the fast phase)
•May be horizontal, rotary, vertical or change position when the patient changes position

30
Q

What is the difference between peripheral and central vestibular lesions

A

–Peripheral
•Nystagmus is either horizontal or rotatory and does NOT change in character when the head position is changed
–Central
•Horizontal, rotatory, verticaland MAY change when the patient is put into dorsal or lateral recumbency (positional)

31
Q

What is the vestibulo-colic reflex?

A

•Produces neck movements and forelimb extension that counteracts the tilt of the head
–It is going to keep the head level with respect to gravity and movement
–Think about being on a boat, your body is trying to keep the plane even

32
Q

What happens if there is a unilateral lesions in the vestibulo-colic reflex?

A

•Unilateral lesion-decreased/absent firing on the side of the lesion, with the other side firing at a normal rate
–The cerebellum only receives signal from the one side that is working and counteracts that signal by moving the head towards the side of decreased firing
–Head tilts TOWARDS the side of the lesion

33
Q

What is the vestibulospinal reflex?

A

•Uses vestibular information to produce limb extension that counteracts the displacement of the head
–Prevents falling when the head shifts in position

34
Q

What happens if there is decreased firing on one side of the vestibulospinal reflex?

A
  • Decreased firing on one side means the patient only senses that there is movement toward the intact side
  • Animals will try to counteract the movement by moving their posture and balance towards the lesioned side. This means that the extensor tone in the limbs on the normal side is increased, which will cause the patient to lean, circle or roll to the side of the lesion
35
Q

What is the progression of the optic tract starting from the eye?

A
  • Light goes in, travels down the optic nerve, through the optic chiasm, towards the lateral geniculate nucleus, and then radiates out to the occipital lobe/visual cortex for perception
  • It can also travel towards the rostral (superior) colliculus
36
Q

How does vision work for animals that have eyes placed so that visual field overlaps?

A

–This creates a binocular field and the visual cortex evaluates information from both fields and creates a 3-D view for depth perception

37
Q

What are the characteristics of vision in animals that have laterally placed eyes?

A

–Increases peripheral vision, but is largely monocular (bad depth perception)
–Increased decussation compared to predators

38
Q

Where do optic nerves go after they penetrate the optic disk?

A 
•RetinogeniculostriatePathway(cortical)
–via lateral geniculate nucleus (LGN)
•RetinopretectalPathway(non-cortical)
–via pretectalnucleii
•RetinotectalPathway(non-cortical)
–via rostral colliculi
•RetinohypothalamicPathway(non-cortical)
–via suprachiasmaticnucleus
39
Q

What is the retinogeniculostriate pathway involved in?

A

–conscious perception of vision

–menace response pathway

40
Q

What is the retinopretectal pathway involved in

A
  • PLR (reflex)

pupilary light reflex -> constriction of pupil

41
Q

What is the retinotectal pathway involved in?

A

ocular fixation (reflex) -> startle reflex

  • for reflex orientations of the eyes and head towards visually interesting stimuli
  • process visual information without conscious awareness (blindsight)
42
Q

What is the retinohypothalamic pathway involved in?

A

circadian rhythms

  • light input for circadian rhythms
  • photoperiods for breeding
43
Q

How do you test the retinogeniculate pathway?

A

–Maze
–Drop a cotton ball, roll a ball, throw a toy across the visual field
–Visual placement test
–Menace response (recognizing the need to blink)

44
Q

What is important to do when performing a papillary light reflex? why is it important?

A
  • When you are performing the PLR, you are going to want to look in BOTH eyes. There should be a consensual response in the indirect eye (the eye where the penlight is not shown). The response won’t be as dramatic, but you will see a response
  • This is important to be able to localize lesions.
45
Q

What are pupillary abnormalities common with?

A

brainstem trauma

46
Q

True or false? The pupillary light reflex will tell you if the animal has visual deficits. Why or why not?

A

False
–Mild response can be extremely difficult to observe in animals
–Intracranial trauma, damage to the ARAS or brainstem
–If the animal is depressed and not aware, it is usually indicative of a poor prognosis

47
Q

What is Anisocoria?

A

when the pupils are uneven in size

48
Q

What is Horner’s?

A
  • Sympathetic denervation
  • Central (CNS) disease, other clinical signs are likely
  • Preganglionic-neck trauma or disc rupture, brachial plexus avulsion, axillary lesion, cranial thoracic disease, neck tumor, traumatic venepuncture
  • Postganglionic most common-otitis, orbital disease
  • Idiopathic is most common

Gross Anatomy II (5 decks)

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