2nd Sem 1 Flashcards
What is the Central canal a remnant of?
Neural Tube
Cell type in Central canal
Ependymal cells
Ciliated Columnar
Lateral Horn contains
PREGANGLIONIC
- T1-L2 Sympathetic neurons
- S2-S4 Parasympathetic neurons
a-Motor Neuron
- Largest Motor Neuron
- Innervates Extrafusal fibers
y-Motor Neuron
Innervates Intrafusal muscle fibers
Extrafusal fibers
Regular skeletal muscle fibers
(Force and Movement)
Intrafusal fibers
Fibers located inside muscle spindles
(detect changes in muscle stretch)
Types of Neurons in Grey matter
- Motor Neurons
- Pre.ggl Neurons (GVM)
- Projection Neurons
- Interneurons
Motor neuron types
a, B, y
alpha / beta / gamma
B-Motor Neuron
Intrafusal & Extrafusal fibers
Dual innervation
Ventral Anterior horn contains
Motor neurons of
Extensors
Dorsal Anterior horn contains
Motor neurons of
Flexors
Lateral Anterior horn contains
Motor neurons of
Distal muscles
Medial Anterior horn contains
Motor neurons of
Proximal / Axial muscles
Projection neuron’s soma located in
Lamina I, III-IV
Types of Interneurons
- Propriospinal (Excitatory)
- Local
- Inhibitory
Short vs Long Propriospinal interneurons
Short: Lamina IX
Long: Deep dorsal horn, Lamina VII, Lamina X
Propriospinal / Intersegmental tracts
- Interfasicular Tract (Comma tract of schultz) [cervical]
- Septomariginal Fasiculus (Oval area of flechsig) [thoracic]
- Cornucomissural Tract (philippe-gombault triangle) [sacral]
Types of Local interneurons
- Commissural Interneuron
- Intercalated Interneuron
Commissural Interneuron
Crosses the midline to the other side without leaving the spinal cord
Intercalated Interneuron
Receives input from sensory neuron and transmits to motor neuron
(do not cross)
Distribution of inhibitory interneurons
- Supf. Dorsal horn in laminae I-III
- Deep Dorsal horn in laminae IV-VI
- Ventral horn in laminae VII-IX
Inhibitory interneurons in Supf. Dorsal horn
Decrease nociceptive signaling to Brain
Inhibitory interneurons in Deep Dorsal horn
Presynaptic inhibition
Inhibitory interneurons in Ventral horn
- Renshaw cells
- Ia inh. interneurons
- Ib inh. interneurons
Renshaw cells
Recurrent inhibition of overactivation of a-motor neurons
Ia inhibitory internurons
Reciprocal inhibition on Antagonist motor neurons
(stretch of one muscle inhibits the activity of the opposing muscle)
Ib inhibitory interneurons
Input from Golgi Tendon Organs (GTOs) on tendon stretch
If too much tension, a-motor neuron of muscle is inhibited
Skin receptors
- Encapsulated
- Non-encapsulated (free)
- Merkel Complexes
Encapsulated skin receptors
- Meissner corpuscle (fine touch)
- Pacinian corpuscle (vibration)
- Ruffini corpuscle (stretch)
Non-encapsulated skin receptors
- Thermoreceptors
- Nociceptors
- Hair follicle receptors
Merkel cells sense
Touch & Pressure
Types of Intrafusal Fibers (Proprioceptors)
- Nuclear chain fiber
- Nuclear bag fiber
Nerve ending types in Muscle spindles
- Flower spray (a-y fiber, stretch)
- Annulospiral (a-a fiber, length & velocity)
Type C nerve fiber
Only unmyelinated fiber
Postganglionic, nociceptor
Type B nerve fiber
Preganglionic autonomic fiber
Type Aa nerve fiber
A-Ia = Annulospiral ending
A-Ib = Golgi tendon organ
Type B nerve fiber
- Skin mechanoceptors
- Flower spray ending
Type Ay nerve fiber
y motorneuron
(Intrafusal fibers)
Type A-delta nerve fiber
- Pain
- Temperature
Monosynaptic reflexes
- Proprioceptive
- Myotactic
- Stretch reflexes
Polysynaptic reflexes
- Nociceptive
- Withdrawal
- Ipsilateral flexor
- Contralateral extensor
- Autonomic reflexes
Patellar reflex
Monosynaptic reflex
Patellar ligament hit, Quad. fem. elongated, triggers reflex to contract
+ Reciprocal inhib. of Hamstring mm. (antagonistic)
y-loop regulation
1) y-motor neuron axon to intrafusal fibers, stretch in muscle
2) Annulospiral sense (Ia) and send to spinal cord
3) a-motor neuron activates extrafusal fibers
4) Full muscle contraction
5) Important for balance, posture, fine motor control
Co-release vs Co-transmission
- Co-release: presynapsis can release different NTs from same vesicle.
- Co-transmission: presynapsis releases different NTs from separate vesicles (different Ca2+ sensitivities)
Main Parts of the Cerebral Cortex
- Allocortex (Older)
- Isocortex (Newer)
Allocortex parts
- Paleocortex (paleopallium, rhinencephalon): 4 layers, olfactory system.
- Archicortex (archipalleum): 3 layers, memory, limbic system
Isocortex parts
Neocortex: 6 layers, 90% of cerebral mantle, higher order brain function
Stellate cells
Interneuron in Neocortex
(GABA)
Glial cell examples
- Astrocytes
- Oligodendrocytes
- Microglia
What forms BBB
Astrocytes
Oligodendrocyte function
Created myelin sheath in CNS
(like Schwann in PNS)
Microglia function
Macrophages of the CNS
Derived from from Mesoderm
(others neuroectoderm)
Staining of Isocortex/Neocortex
- Golgi-impregnation: Whole cell
- Nissl stain: Perikarya & Dendrites (rER of neuron)
- Myelin s. stain: Axons (show direction)
Layers of Neocortex
1) Stratum Moleculare / Zonale / Plexiforme
2) Stratum Granulosum Externum
3) Stratum Pyramidale Externum
4) Stratum Granulosum Internum
5) Stratum Pyramidale Internum
6) Stratum Multiforme
What Layer has small Pyramidal cells
Stratum Pyramidale Externum (III)
What layer has Large Pyramidal cells & their name
Stratum Gangliosum (V)
Betz Cells (only in Motor)
3 Tracts within CNS
- Association Tracts
- Commissural Tracts
- Projection Tracts
Association Tracts
Connect different areas of the same hemisphere
(fasciculi)
Commissural Tracts
Cross the Midline connecting same cortical regions of different hemispheres
(e.g corpus callosum)
Projection Tracts
Connect cortex with other areas of CNS
(Brainstem, Spinal Cord)
Layer III (str. pyramidale ext.)
Connections
Efferent
Cortico-Cortical projections
Can innervate all other layers
Layer IV (str. granulosum int.)
Connections
Afferent
Receives specific Thalamo-Cortical inputs
All sensory info except smell.
Layer V (str. Pyramidale int)
Connections
Efferent
Subcortical projections
Efferent tracts of pyramidal cells towards motor neurons
Layer VI (str. multiforme)
Connections
Efferent
Cortico-Thalamic projections
Projections to the thalamus
Receptors of sensory tracts
- Exteroceptor (pain, temp, touch)
- Proprioceptor (muscle, joint)
Intracerebral Pathway Parts
- Limbic system (emotion, memory)
- Basal ganglia (movements)
2 Methods of Brain Imaging
- FMRI: cortical area stimulation (O2)
- DTI (diffusion tensor imaging)
Functional units of the Cortex, Size, Cell count
Cortical Columns (2 million total)
200-300 μm in diameter, 2.5-3 mm high
~5000 cells per column
Brodmann 4
Primary Motor cortex
(Precentral Gyrus)
Brodmann 6
Secondary Motor area
(front of Precentral Sulcus)
Brodmann 3, 1, 2
Primary Somatosensory cortex
(Postcentral gyrus)
Brodmann 17
Primary Visual Center
(Area striata, both sides of calcarine sulcus) Occipital lobe
Brodmann 18, 19
Secondary & Tertiary Visual centers
(Area parastriata) Occipital lobe
Brodmann 22
Sensory Speach Area / Wernicke’s Area
(superior temporal Gyrus)
Brodmann 41, 42
Primary Hearing Center
(Heschl gyri, lower side of lateral sulcus) Temporal
Brodmann 43
Taste center
(inferior postcentral gyrus, insula)
Brodmann 44, 45
Motor Speach Area / Broca’s Area
(Frontal Lobe)
Brodmann 51
Primary Olfactory center
(temporal Lobe)
Brodmann 28
Secondary Olfactory center
(surface of parahippocampal gyrus)
Multimodal Association Cortices
Receive info from more than one origin:
- Parietal Multimodal Cortex
- Temporal Multimodal Cortex
- Prefrontal Cortex
Parietal Multimodal Association Cortex Parts & Functions
- Lateral: hearing, vision, speach.
- Superior: hand movement
- Posterior: spacial awareness
Temporal Multimodal Association Cortex
Integrates Visual and Auditory Information
(Memory of faces, people)
Prefrontal Cortex Parts & Functions
- Dorsolateral: planning, working memory, motor program.
- Ventrolateral: recognition, understanding.
- Orbitofrontal: emotion, motivation, social behavior
Sympathetic Neurons location
T1 - L2 of Lateral Horn
Sympathetic Ganglia
- Paravertebral Chain (sup. mid. inf cervical ggl)
- Preaortic ggl. (celiac, sup. inf. mesenteric)
Preganglionic Neurotransmitter
Acetylcholine
(Both)
Postganglionic Neurotransmitter
Parasympathetic: Acetylcholine
Sympathetic: NE
Parasympathetic Neurons location
- Brainstem (nuclei)
- S2 - S4
Parasympathetic Ganglia
- Ciliary ggl
- Lacrimal ggl
- Pterygopalatine ggl
- Submandibular ggl
Autonomous Reflex importance
1) Pain signal from an organ travels to the dorsal root ggl.
2) Causes stimulation of Symp/Parasymp stystem.
3) Can cause deferred pain
Reticular Formation
- Network of neurons in the brainstem
- Extends from the spinal cord to the midbrain, subthalamus, hypothalamus, and thalamus
- (arousal & wakefulness)
Biogenic Amines in Brain Stem
- Noradrenergic
- Adrenergic
- Dopaminergic
- Cholinergic
- Ascending reticular activating system
- Histaminergic/Serotoninergic
Noradrenergic Cell groups
- Clusters of Neurons producing NE
- A1 - A7 (medulla to midbrain)
- A6 Locus Cereuolus (pons)
(amygdala, hipocamp, cingulate gyrus)
Adrenergic Cell groups
- C1-C3
- Medulla Oblongata
Dopaminergic Cell groups
- A8-A16 (midbrain)
- A9 (substantia nigra)
- A10 (Ventral Tegmental Area)!!
Serotoninergic Cell groups
- B1-B9 (medulla to midbrain)
- Reaches every part of brain completely (sleep)
Cholinergic Cell groups
- Under inferior frontal lobe
- Memory formation
- Somatomotor nuclei of CN 3,4,6 eye movement
Reticular formation can be classified into 3 groups of Nuclei
- Median Nuclei group
- Paramedian Nuclei group
- Lateral Nuclei
Median Nuclei group
(reticular formation)
Contains Raphe Nuclei (Seretonergic!)
- Nucleus raphe obscurus & magnus (analgesic)
- Pontine & Median raphe nuclei (serotonin)
- Post. raphe nuclei (sleep/wale)
Paramedian Nuclei group
(reticular formation)
- Locus ceruleus (NE)
- Pneumotaxic region
- Dopaminergic part in mesencephalon
Levels of Regulation of Autonomic System
1) Spinal Cord level
2) Supraspinal Level (brainstem) -eg: solitary tract, CNX
3) Central autonomous reg.
Types of Thalamic Nuclei
- Relay
- Reticular
- Intralaminar
Epicritic Sensation
Fine touch, vibration
- Fasiculus Gracilis
- Fasiculus Cuneatus
Protopathic Sensation
Pain, temperature, crude touch, and pressure
- Lateral Spinothalamic tract
- Anterior Spinothalamic tract
Proprioception
Position sense
- Posterior Spinocerebellar t
- Anterior Spinocerebellar t
Somatosensory pathway (medial lem.)
1) Pseudounipolar sensory neuron in DRG
2) Ascend ipsilaterally as Gracile/Cuneate Fascilcles
2) Gracilis & Cuneate nuclei in Medulla Oblongata
3) Axons cross midline (int. Arcuate fibers) and travel as Medial Lemniscus
4) VPL of Thalamus
Lateral Spinothalamic tract sensation
Protopathic sensation
(pain, temp, tickle, itch)
Anterior Spinothalamic tract sensation
Protopathic
Crude touch & Pressure
2 Types of pain impulses to CNS
- Ay fiber fast initial sharp pain
- C fibers prolonged burning aching pain
Spinothalamic tract pathway
1) Skin receptors to DRG
2) Axons can go up or down in tract of Lissauer
3) Terminate on Lamina II (sub. gelatinosa)
4) Axons cross through Anterior White Comissure
5) Fibers form Spinal Lemniscus
6) VPL of Thalamus
Spinocerebellar tracts sensation
Proprioception
Posterior Spinocerebellar Tract pathway
1) DRG to Clarke’s Lamina VII
2) Ascend Ipsilaterally
3) Inferior Cerebellar Peduncle
4) Axons terminate with Mossy fibers at str. granulosim Cerebellar cortex
(Below T6)
Anterior Spinocerebellar Tract pathway
1) DRG to Dorsal Grey Horn (L4-S3)
2) Cross midline at anterior white commissure
3) Ascend Contralaterally
4) Superior Cerebellar Peduncle
5) Many fibers cross back to Ipsilateral side (2nd cross) in cerebellum
(Below L3)
Trigeminal Epicritic Sensation Pathway
1) Trigeminal ggl
2) Principal nucleus (pontine/chief)
3) Crossed and Uncrossed axons in Trigeminothalamic tract
4)VPM of Thalamus
Trigeminal Protopathic Sensation Pathway
1) Trigeminal ggl
2) Spinal Trigeminal nucleus
3) Axons cross and ascend
4) VPM of Thalamus (contralateral)
Trigeminal Proprioception (Trigeminal Lemniscus)
Proprioceptive info from masticatory mm. + Epicritic sens. + Protopathic sens.
Main Autonomic Nucleus of Brainstem
Solitary Tract Nucleus
(NTS)
Spinoreticulothalamic Afferent Pathway
1) DRG
2) Contralateral
3) Lat. Spinothalamic tract
4) Some fibers to R.F - Parabrachial & Periaqueductal nuclei
5) MD & Intralaminar nuc. Thalamus
6) dors. post. insula, ant. cingulate g, secondary sens. cortex.
Subregions of Solitary Nucleus
- Gustatory Nucleus
- Baroreceptor Nucleus
- Dorsal Respiratory Nucleus
- Commissural Nucleus (lat. ala cinerea)
Diencephalic Relay gets info from
- Spinothalamic Tract
- Reticular Formation
Posterior part of Insula is called
Viscerosensory Cortex
Tripartite Model of Pain
1) Sensory-Discriminative aspect
2) Affective-Motivational aspect
3) Cognitive-Evaluative aspect
How to Tricyclic Antidepressants work?
Increase levels of NE and Serotonin by Inhibition of reuptake from the synapses
Where are inhibitory interneurons of Gate-control-theory found?
Lamina II of Dorsal Horn
Neuropathic Pain
Pain from damage to Somatosensory system
Nociplastic pain
Altered pain processing in nervous system without any apparent damage to peripheral nerves
What % of Corticospinal fibers decussate and form the lateral corticospinal tract?
90%
Control Distal limb muscles
What % of Corticospinal fibers continue straight and form the anterior corticospinal tract?
10%
Control Proximal muscles (posture)
Steps of Visceromotor Pathway
1) Type B fibers
2) Autonomic ggl
3) Type C fibers to organ
4) Smooth/Cardiac mm, glands
Spinal reflex Symp vs Parasymp Efferentation
- Parasympathetic: intermediomedial nucleus
- Sympathetic: intermediolateral nucleus
Special Sympathetic innervation of Adrenal Medulla
Only receives Preganglionic fibers for the release of Epinephrine (Adrenaline)
