Peripheral Sensory and Spinal Cord

Question 1

Proprioception receptors

Answer 1

Muscle spindles (Ia and II)
Imbedded in postural muscles + others
Gamma motor neurons also which contract muscle spindles so they maintain sensitivity
Golgi tendon organs are the other proprioceptor and they have fascicles with connective tissue around them

Question 2

Touch receptors

Answer 2

All are A-beta fibres
Merkel disks: fine touch and pressure
Meissner corpuscles: fine touch, pressure and low frequency vibration
Pacinian corpuscles: pressure and vibration
Ruffini endings: deep pressure

Question 3

Pain/temperature receptors

Answer 3

Free nerve endings (A-delta)

Question 4

Pain/temperature/itch receptors

Answer 4

Unmyelinated free nerve endings (C fibres)

Question 5

Types of nociceptors

Answer 5

1. Thermal nociceptors (>45 or <5) - thinly myelinated A-delta fibres
2. Mechanical nociceptors, mostly A-delta, intensely pressure-sensitive
3. Polymodal nociceptors from intense mechanical/chemical/thermal stimuli with C fibres

Question 6

Taste bud cell types

Answer 6

• Type I (50%) unknown, ?salty
• Type II (30%) bitter, sweet and umami
• Type III (2-20%) sour

Question 7

Tract where spinothalamic tracts decussate

Answer 7

Lissauer’s tract (gives a few spinal levels up or down)

Question 8

Functional organization of the spinal cord

• Dorsal horn
• Lateral horn
• Ventral horn

Answer 8

Dorsal: sensory
Lateral: autonomic
Ventral: motor

Question 9

Medial lemniscus path (senses, decussation, processing and relay)

Answer 9

Light touch, vibration and proprioception
Decussate at medullary pyramids
Processed by ventral thalamic nuclei according to nature/origin
Relayed by thalamic nuclei to the primary sensory cortex

Question 10

Anterolateral pathway (senses, decussation)

Answer 10

Anterior & lateral spinothalamic tracts
Pain, temperature and crude touch
Decussate seems immediately (Lissauer’s tract)

Question 11

Spinocerebellar tracts (parts, senses, decussation)

Answer 11

Anterior and posterior spinocerebellar tracts
Proprioception to the cerebellum
Anterior crosses 2x
Posterior does not cross

Question 12

Neural development:

• Neural plate
• Start of brain

Answer 12

Neural plate at 18 days

Start of brain at 24 days

Question 13

Primary to secondary brain bits (primary are prosencephalon, mesencephalon and rhombencephalon)

Answer 13

Prosencephalon - telencephalon and diencephalon
Rhombencephalon - metencephalon and myelencephalon
Mesencephalon stays the same

Question 14

Brain stem development: neuron migration

Answer 14

Sensory go laterally

Motor go medially

Question 15

Telencephalon structures (2)

Answer 15

Cerebral hemispheres

Basal ganglia

Question 16

Diencephalon structures (2)

Answer 16

Thalamus

Hypothalamus

Question 17

Mesencephalon

Answer 17

Links forebrain and hindbrain

Contains cerebral aqueduct

Question 18

Metencephalon (2)

Myeloncephalon (1)

Answer 18

Metencephalon: cerebellum and pons
Myelencephalon: medulla

Question 19

Lentiform nucleus structures?

Striatum structures?

Answer 19

Putamen and globus pallidus

Caudate and putamen

Question 20

Fibre tract of hemispheres:

• Commissural
• Association
• Projection

Answer 20

Commissural: between hemispheres. Corpus callosum, anterior commissure and posterior commissure
Association: arcuate and longitudinal fasiculi
Projection fibres: internal capsule

Question 21

Dura mater (tissue type, layers, folds, veins, spinal layers)

Answer 21

Dense, fibrous connective tissue (tough and inelastic)
2 layers - periosteal layer connects to inside of cranium, inner meningeal layer invaginates to the folds
Folds: falx cerebri (longitudinal fissure), falx cerebelli (partially separates cerebellar hemispheres), tentorium cerebelli (occipital lobe from cerebellum), diaphragmata sellae above pituitary
Veins drain to sagittal sinuses and eventually the jugular vein
Spinal dura is single-layered as the periostal layer doesn’t go beyond the foramen magnum.

Question 22

Arachnoid mater (material, space, pierces the dura)

Answer 22

Avascular, continuous, fibrous elastic connective tissue
Has cisterns over larger spaces
Has subarachnoid space (CSF and blood) beneath
Sticks through dura at dural sinuses to diffuse CSF into venous blood

Question 23

Pia mater (function)

Answer 23

Helps produce CSF

Encapsulates blood vessels through the subarachnoid space to the cortex

Question 24

Walls of the lateral ventricles

Answer 24

Roof: corpus callosum
Medial wall: septum pellucidum
Lateral wall: parietal lobe

Question 25

Drainage of deep veins Drainage of superficial veins

Answer 25

Deep - inferior sagittal sinus - straight sinus Superficial - superior sagittal sinus Both converge to internal jugular veins

Question 26

Corticospinal AKA pyramidal tract

Answer 26

``` Voluntary controlled skill movements Lateral tract (90%) decussates at pyramids Anterior/ventral tract does not ```

Question 27

Brain stem layers: tectum

Answer 27

Roof (midbrain only) | Superior and inferior colliculi

Question 28

Brain stem layers: tegmentum

Answer 28

Reticular formation Most cranial nerve nuclei Some ascending/descending tracts

Question 29

Brain stem layers: anterior structures

Answer 29

Pyramids Olive Basal pons and cerebellar peduncles Some tracts

Question 30

Structures in the caudal midbrain

Answer 30

Substantia nigra Inferior colliculi/lateral lemniscus Crus cerebri (descending fibres) Decussation of superior cerebellar peduncles

Question 31

Structures in rostral midbrain

Answer 31

Superior colliculi Periaqueductal grey Red nucleus