7. Fine structure of the spinal cord. Spinal reflexes, receptors and effectors Flashcards
The role of Nervous system
- Receives information from the periphery (receptor)
- Conveys it to the center (afferent path)
- Processes the received pieces of information and determines an answer (central switching part)
- Transmits the answer to the place of action (efferent path)
- Action (effector)
The simplest examples of the reactions of the working nervous system are the __
reflexes
The basic place, where these reflexes can be easily described is (1)____, but they also occur on the level of (2)___
- the spinal cord
- the cranial nerves
Identify types of nucleus
Name of these ganglia
Name of this corpuscle
Paccinian corpuscule
Name of this corpuscle
Meissner’s corpuscule
Name 3 major Exteroceptors
- Naked nerve terminal in the skin (pain, heat)
- Meissner’s corpuscule (touch)
- Vater-Paccini’s lamellar body (pressure)
What is Ruffini’s ending? What is its role?
An exteroceptor responsible for feeling pressure
What is Krause end bulb? What is its role?
An exteroceptor responsible for touch
What is Merkel’s cell and disc? What is its role?
An exteroceptor responsible for touch
Name 5 majors interoreceptors
- Golgi-Mazzoni-corpuscule (tendons, joints)
- Vasoceptors
- Internal nociceptors
- Chemoreceptors (carotid body)
- Stretch receptors (carotid sinus)
Identify (left side)
Identify (right side)
What are Effectors?
effects of neurons on other cells
Examples of neurosecretory nucleus
supraoptic, paraventricular nucleus
What is Vegetative basal „braid”?
axonal swellings (postganglionar fibres) get close to the smooth muscle cell membrane with no specialized structures
What is Neuroglandular synapse?
innervation of glands
This is Motor end plate – neuromuscular junction
-> Identify
The spinal cord
What make up the spinal nerve?
Posterior and anterior radices make up the spinal nerve
The spinal cord
The posterior radix runs close to and is in connection to the spinal ganglion situated in ____
the intervertebral foramen
The spinal cord
___ (2 things) covers the radices
The arachnoid mater and the dura mater
The spinal cord
What compose the spinal cord? (not layers)
White matter and gray matter
Identify
Lissauer-zone
Incoming sensory fibers can projects upwards without entering ____
the gray matter (dorsal ascending tract)
Incoming (sensory) fibers can synapse in ___
dorsal horn
Most of incoming sensory fibers diverge to more segments through (1)____ with (2)_____
- the Lissauer’s zone
- collaterals
Gross anatomy of the spinal cord
What does gray matter contain?
posterior horn- posterior column
Lateral horn – lateral column
Anterior horn – anterior column
Intermediate zone
Gross anatomy of the spinal cord
Identify components of white matter
Identify name of nuclei
- Marginal zone
- Substantia gelatinosa
- Proper nucleus of the dorsal column
- Dorsal nucleus (Clarke-Stilling)
- Intermediolateral nucl.
- Intermediomedial nucl.
The gray matter
Sensory nerve classification
IV or C-type: unmyelinated, mainly heat, pain
III or Aδ-type: thin myelin sheath: mechanoreception, heat, cold, pain
II- or Aβ: thick myelin sheath: mechanoreception, flower-spray in muscle spindle
Ib- or (Aα): thick myelin sheath: Golgi tendon organ
Ia- or (Aα): thick myelin sheath: anulospiral ending
The gray matter - classfication of sensory nerves
Describe IV or C-type fibres
unmyelinated, mainly heat, pain
The gray matter - classfication of sensory nerves
Describe III or Aδ-type fibres
thin myelin sheath: mechanoreception, heat, cold, pain
The gray matter - classfication of sensory nerves
Describe II- or Aβ fibres
thick myelin sheath: mechanoreception, flower-spray in muscle spindle
The gray matter - classfication of sensory nerves
Describe Ib- or (Aα) fibres
thick myelin sheath: Golgi tendon organ
The gray matter - classfication of sensory nerves
Describe Ia- or (Aα) fibres
thick myelin sheath: anulospiral ending
The gray matter
Name of this area
Dorsal horn
The gray matter
The major roles of dorsal horn
- Receive central processes of pseudounipolar neurons in the dorsal root ganglion
- Sensory information is processed and transmitted to higher regions horn
The gray matter
What is the major type of neuron you can find in dorsal horn?
interneurons
The gray matter
Describe Marginal zone (Lamina I)
- Spindle-shaped neurons,
afferentation from the periphery, nociceptive and heat impulse. - Interneurons (reflexes) and funicular neurons (spinothalamic tract)
The gray matter
Describe Substantia gelatinosa (Lamina II) of dorsal horn
- small neurons
- fibres are afferents from the skin, Aδ and C- fibers,
- receive monoaminergic input from the brainstem
- Efferentation mainly in the same lamina
- procession of pain
The gray matter
Describe Proper nucleus of dorsal column (Lamina III-IV)
- mainly Aβ fibres from the skin
- mainly transmitted to the spinothalamic tract
The gray matter
Describe Lamina V-VI
various types of afferents , interneurons and funicular (spinothalamic tract) neurons
What does Gate-control theory (Melzack and Wall, 1965) say?
The pain –carrying C fiber activates the upwards projecting funicular neuron and inhibits the interneuron, which inhibits the latter.
Incoming mechanoreceptor information-carrying Aβ-fiber activates the inhibitor of the projective (funicular) neuron.
=> So the pain information on the funicular neuron is decreased.
Gate-control theory (Melzack and Wall, 1965)
-> The pain –carrying C fiber activates (1)___ and inhibits the (2)____, which inhibits the latter.
- the upwards projecting funicular neuron
- interneuron
Gate-control theory (Melzack and Wall, 1965)
Incoming mechanoreceptor information-carrying Aβ-fiber activates _____
the inhibitor of the projective (funicular) neuron.
What does Gate-control theory (Melzack and Wall, 1965) say?
What type of fiber activates the upwards projecting funicular neuron and inhibits the interneuron, which inhibits the latter?
The pain –carrying C fiber
What does Gate-control theory (Melzack and Wall, 1965) say?
What type of fibres activates the inhibitor of the projective (funicular) neuron?
Incoming mechanoreceptor information-carrying Aβ-fiber
Name of this area (red)
The intermediate zone
Which nucleus are included in intermediate zone?
The intermediate zone
The intermediate zone
Describe Lamina X
central gray matter, several intraspinal connections
The intermediate zone
Describe Lamina VII
It contains Clarke-Stilling nucleus
-> proprioceptive and epicritic information from the lower limb, large neurons project to the cerebellum through the dorsal spinocerebellar tract
The intermediate zone
The role of Clarke-Stilling nucleus
proprioceptive and epicritic information from the lower limb
The intermediate zone
The role of Intermediomedial nucleus
sympathetic and parasympathetic preganglionar neurons
The intermediate zone
The role of Intermediolateral nucleus
sympathetic preganglionar neurons, in the thoracic and upper lumbar levels the lateral horn is formed
Name of this area (red)
The ventral horn
The ventral horn
Describe IX lamina
groups of Aα- and Aγ-motoneurons, innervating the skeletal muscles
Interneurons, e.g: Renshaw-cells: reciprocal inhibition
The ventral horn
Describe lamina VIII
various neurons.
Commissural nucleus of Lenhossék: crossing fibres in the commissura alba
The ventral horn
Motor nerve classification
Aα: extrafusal fibers
Aγ: intrafusal fibers
This is a typical motor neuron in the ventral horn
-> Identify
The white matter
The role of Gracile fascicle and cuneate fascicle
transmit the epicritic information (fine touch, pressure, vibration) and proprioceptive information from the joints and muscles
The white matter
The role of Gracile fascicle and cuneate fascicle
transmit the epicritic information (fine touch, pressure, vibration) and proprioceptive information from the joints and muscles
The white matter
The role of Anterior and posterior spinocerebellar tracts
Transmit proprioceptive (from tendons, mucles, joints) information to the cerebellum via mossy fibres
Posterior (Th9-L3): from the dorsal nucleus (Clarke-Stilling)
Anterior (L4-S3)
The white matter
The role of Anterior and lateral spinothalamic tracts
protopathic sensibility (crude touch (anterior), heat and pain (lateral))
The white matter
The role of Anterior and lateral corticospinal tracts
voluntary movements from the cortex („pyramidal tract”)
The white matter
The role of Extrapyramidal tracts
coordination and processing motor commands at a subconscious level.
The white matter
Identify
Describe motor and descending pathyways (efferent) (somatotopic arrangement)
Describe sensory and ascending pathyways (efferent) (somatotopic arrangement)
Two types of intrafusal fibers innervated by two types of sensory nerves and nerve endings.
-> What are they?
Nuclear bag fibers: afferent „Ia”, anulospiral ending
Nuclear chain fibers: afferent II, flower-spray ending
Which fibres involving in motor innervation of muscle?
Aγ-fibers
Which fibres involving in
innervation of tendons? Sensory or motor?
Ib afferents
-> Sensory
Describe the pathway of Proprioceptive, monosynaptic reflex
- Receptor: anulospiral terminal on the muscle spindle
- Afferent nerve: Aβ (Ia), pseudounipolar
- Central process: 1 synapse on the Iα motor neuron
- Efferent nerve: Aα motor neuron
- Effector: motor end plate → extrafusal muscle fiber
Examples of Proprioceptive, monosynaptic reflex
brachioradial reflex, patella-reflex, masseter-reflex
Some Additional mechanisms of Proprioceptive, monosynaptic reflex
- Reciprocal inhibition (through interneurons of the other side)
- γ-loop (the γ-motor neuron innervates the muscle spindle. By changing the sensitivity of the intrafusal fibers, γ-motor neurons can change the length of the muscle)
Additional mechanisms of Proprioceptive, monosynaptic reflex
-> Describe γ-loop
the γ-motor neuron innervates the muscle spindle. By changing the sensitivity of the intrafusal fibers, γ-motor neurons can change the length of the muscle
Additional mechanisms of Proprioceptive, monosynaptic reflex
-> Describe Reciprocal inhibition
through interneurons of the other side
What are Renshaw-cells?
Inhibitory cells of the ventral horn
Innervation of Renshaw-cells
They are innervated by the collaterals of active α-motor neurons
What do Renshaw’s cell inhibit?
inhibit the neighbouring α-cells
Renshaw-cells
-> When the activity of a motor neuron ___ (decrease/increase), the neighbouring cells are losing their previous inhibition
decreases
Renshaw-cells
-> When the activity of ____ decreases, the neighbouring cells are losing their previous inhibition
a motor neuron
Describe Tendon reflex
- Tendon spindles (of Golgi) sign at deformation (stretch and contraction)
- Disynaptic reflex, inhibits the α- and γ- motor neurons
The role of tendon reflex
decreases the muscle tone
Describe Nociceptive (withdrawal) and crossed extensor-flexor reflexes
- Receptor: skin receptor, probably nociceptive
- Afferent nerve: Aδ or C-fibers, pseudounipolar neuron
- Central process: one or more interneurons; funicular neurons over more segments
- Efferent nerve: Aα motor neuron, minimum the third
- Effector:
motor end plate → extrafusal muscle fiber
=> Flexor muscles ipsilaterally + Extensor muscles contralaterally (crossed)
Examples of Nociceptive (withdrawal) and crossed extensor-flexor reflexes
when you step into a nail (nociceptive and crossed flexor-extensor reflex)
Abdominal reflex, cremaster-reflex, cornea-reflex, cough…
Pathway of Autonomic reflex – viscero-visceral reflex
- Receptor: enteroceptor in the internal organ
- Afferent nerve: Aβ (Ia), or Aδ or C –fibers, pseudounipolar nerves
- Central process: minimum one interneuron, divergence among several segments
- Efferent nerve: B-fiber – preganglionic motor neuron → prevertebral sympathetic or intramural parasympathetic ganglion cell: C-fiber
- Effector: visceral organ: smooth muscle
„Mixed” reflexes
What is Viscerocutan?
From the organs to the skin (sudomotor, vasomotor function)
What is Visceromotor?
from the organs to a skelatal muscle
What is Cutivisceral?
somatosensory input to visceromotor efferent
What are head zones?
Head-zones, „projecting” pain:
-> The viscerosensory and the somatosensory fibres innervate the same interneurons, so, we feel pain and hyperaesthesia on the somatosensory area, although the stimulus comes from the organs.
