Nervous System 💘 Flashcards
Somatic vs visceral
Somatic is voluntary control (PNS)
Visceral is involuntary control (PNS &CNS)
Cell bodies and axons
Found in grey matter (cns) and form connections with ganglia (pns)
Axons found in tracts within white matter (cns) bungle together to form nerves (PNS)
Main sulci and gyri
The central sulcus divides frontal and parietal lobes a lateral fissure separates temporal lobe from frontal and parietal lobe
anterior to central sulcus is precentral gyrus which is motor cortex
posterion is postcentral gyrus which is sensory cortex
Plexus formation
Rootless Root Spinal nerve Rami ramus Plexus
Dermatomes and myatomes
Derma is area of skin supplied by nerves
Myo is muscles
Lesion
A region in an organ or tissue which had suffered damage through injury or disease
Neurulation
Notochord induces differentiation of overlying ectoderm forming nerurectoderm and neural plate
Proliferation and somite formation from paraxial mesoderm
Neural plate then folds over and closes forming neural tube
Notochord becomes nucleus pulposus
Neurulation pt2
Somite zips up and there’s caudal and cranial neuropore
Cranial close on day 25 and become laminate terminalis
Causal closes day 27
Rostral becomes brain
Causal becomes spinal cord
Lumen becomes ventricular system of cns
Three primary brain vesicles
Forebrain prosenCephalon midbrain mesenCephalon hindbrain rhombencephalon for brain splits into telencephalon > cerebral hemispheres and diencephalon becomes the thalami
Mesencephalon becomes midbrain
hindbrain becomes metencephalon which becomes pons and Cerebellum
Myelencephalon beckmes medulla
So 5 secondary vesicles
The cavities and what they form
Central hemisphere> lateral ventricles
Thalami etc >third ventricle
Midbrain >cerebral aqueduct
Pons and cerebellum >superior part of fourth ventricle medulla is inferior part
Spinal cord formation
Neural tube thickens
Three zones matrix mantle and marginal
Matrix zone produces pluripotent epithelial cells
Neuroblasts surrounding this layer is mantle zone (future grey matter)
Neuroblast axons project to marginal zone (future white matter)
Spinal cord formation pt2
Sulcus limitans separates alar and basal plates
Alar plate does doros lateral thickening,sensory function,receives axons from dorsal root ganglion and becomes dorsal horn
Basal plate does ventrolateral thickening, motor function, motor neuroblasts of ventral and lateral horns and becomes central horn
Autonomic zone between two plates
Cranial nerve development
Neural crest cells differentiate from neurectoderm
Migrate through embryo
Further differentiate into pharyngeal arch connective tissue bones of neurocranium etc
Nerves of pharyngeal arches
1=trigeminal
2=facial
3=glossopharyngeal
4 and 6 is vagus nerve
Resting state
-70mv
Voltage gated na+ and k+ channels are closed
Depolarizing state
-55mv
Threshold at axon hillock
Voltage gated na channels open so na flows in cell
Repolarisation
Absolute refractory period
40mv
K+ channels open so k flows out
Inactivation na gate closes
After hyperopolarizatjon
Relative refractory period
-80mv
K channels stay open and na channels still closed
Conduction in unmyelimated Axon
Sodium enters axon Hillock locally depolarizes adjacent regions opening more sodium channels causing action potential. Previous gates closed so current only flows in one direction
Conduction in myelinated axon
Sodium enters axon hillock depolarizes Myelin sheath insulates preventing ion leakage
sodium and potassium channels concentrated only at notes of Ranvier they refresh action potential causing it to jump from one oat to another and this is called saltatory conduction
Resting potential and why
-70mv
Outside of cell more positive inside more negative
Due to low negative protein permeability
Sodium potassium pump (3na out 2k in)
And high potassium permeability so passive transport and also k leak channels
Axon conduction velocity depends on
Axon diameter and myelination
Unmyelinated better for small axons velocity is square root diameter
Myelinated better for larger diameter as velocity is linear with diameter
Carbamazepine effect
Prolongs inactive state of na channel and absolute refractory period
tDCS transcranial direct current stimulation
Affects cortical excitability
anodal and cathodal
Tetrodoxin effect
Sodium channel blocker
An aesthetic
Block voltage gated sodium channels
Esters more commonly used
Affects small diameter neurons
Primary afferent fivres
Large diameter
Rapidly conducting
Alpha and beta fibres
Low threshold mechanoreceptors eg touch
Small diamete are slow conduction
Alpha delta and c fibres
Associated with nociceptors and thermoreceptors (polymodal is c rest is other )
Layer of meninges
Dura mater arachnoid mater and pia mater
Cerebrospinal fluid runs in su arachnoid space
Ventral white commissure
Bundle of fibres that cross midline of spinal cord
Funiculi
Bundle of tracts (axons) within white matter of spinal cord
Ipsilateral and contralateral
Same side of body
Opposite side of body
Dorsal column pathway
Senses discriminative touch
Primary neuron: sensory receptors > gracile or cuneate nucleus in medulla
Secondary neuron:medulla >decussate to form the medial lemniscus pathway >thalamus
Tertiary neuron: thalamus>somatosensory cortex
Spinothalamic tract
Crude touch
First neuron: sensory receptors >rise one to two segments in dorsolateral fasiculus
Second neuron : df> decussate to contra lateral ventrolateral fasiculus> thalamus
Third neuron: thalamus > somatosensory cortex
Dorsal and spino difference
Lemniscal decussation in medulla
Spinothalamic at every spinal level
Dorsolateral and ventromedial supplies
Dorsal is distal muscles elbow and knee down
Ventrolateral supplies elbows and knees up and trunk muscles and controls posture and movement correction
Ventromedial pathways
Reticulospinal tract
Tectospinal tract
Vestibulospinal tract
Dorsolateral pathways
Rubrospinal tract
Corticospinal tract
Reticulospinal tract
Primary neurons arise from pons and medullary reticular formation
Remain ipsilateral and polysegmental
Synapse with LMN in medial aspect of ventral horn.
Tectospinal tract
Primary neurons arise from superior colliculi
Desiccate in midbrain
synapse with the lower motor neurons in the cervical spinal cord
Vestibulospinal tract
Primary neurons arise from vestibular nuclei
Remains ipsilateral medial
Stops at cervical
Lateral at all spinal segments
Synapse with lmn in medial aspect of ventral horn
Runrospinal tract
Originates in red nucleus of midbrain and dessucates in midbrain
Corticospinal tracts
Primary neurons arise from primary motor pre motor and sensory cortex
Most drssucate below pyramids rest ipsilateral
Synapse with lmn in ventral horn at all spinal segments
Stretch reflex
Single synapses between muscle sensory fibre and alpha motor neuron sensory fibre activation quickly activates the alpha motor neuron contracting muscle fibres
Muscle neurons
Muscle spindle runs parallel with muscle
la sensory neurons and Y motor neuron innervates the muscle fibres
Stretching muscle spindle causes increase in la afferebt activity
Gamma Y neuron accommodates length of muscle
Knee jerk reflex
Tap patella tendon
Activates la muscle spindle causing (intrafusal muscle detect the signal)
(Extrafusal contract) impulses to travel to spinal cord release ach and cause contraction
Stretch reflex
When agonist contracts antagonist muscle inhibited so relaxed
Inverse stretch reflex
Golgi tendon had lb afferent and sends sensory info to spinal cord in dorsal horn
Synapses with inhibitory inter neuron which inhibits alpha motor neuron relaxing muscle
Umn lesions
Muscle weakness
Increased tone
Exaggerated reflexes
Babinski sign
Lmn lesions
Muscle weakness Reduces tone Absent reflexes Muscle atrophy Muscle fasiculation
Cerebellum
Coordinates ongoing movements
Detects motor error
Stores learned movements
Improve accuracy of movement
Basal ganglia
Selection/initiation of voluntary movements
Improve accuracy of movement
Cerebellum divisions
Cerebrocerbellum (inputs from cerebral cortex) regulates high skill movement
Spinocerebellum (inputs from spinal cord) lateral part for distal muscle movement central part (vermis) for proximal muscle movement
Vestibulocerebellum (inputs from vestibular nuclei) includes nodulus and floculus involved in movements underlying posture and balance
Peduncles and the pathway
Superior is efferent
Middle is afferent
Inferior is both
Motor and sensory sides
Motor is from opposite side sensory is same side
The nuclei in cerebellar divisions
Cerebro is dentate nucleus
Spinal is interposed and fastigal
Vestibulo is fastigal or direct nucleus
Deep cerebellar nuclei
Major output structures
Relay info to motor cortex and brainstem for corrections in movement
Direct pathway
Globulus pallidus inhibits thalamus reducing excitation of motor cortex command from cerebral cortex
excite straitum inhibits GP
allow thalamus to excite motor cortex initiating movement substantia nigra facilitatesdirect pathway via D1 receptors in striatum
Indirect pathway
Excite striatum
Inhibits gp external
Subthalamic nucleus inhibited so excites gp internal which inhibits the thalamus
Less excitation of motor cortex inhibiting movement
SN directs pathway via d2 receptors in striatum
Parkinson’s disease
Degeneration of neurons is substantia nigra that project to striatum
Decrease on dopamine
Decreased direct and increased indirect pathway
Treated with l dopa and dopamine agonists
TRAP Parkinson’s
Tremor
Rigidity
Akinesia ( reduced movement)
Postural problems
Spinocerebellar pathway
Travels from lateral spinal cord to cerebellum
Primary neuron from muscle/joint receptors
Synapses in dorsal horn with secondary neuron ascends ipsilaterally and enters cerebellum via inferior cerebellar peduncle
For unconscious proprioception and coordination of movements
Dentatothalamic pathway
Travel from dentate nucleus in the cerebellum to the thalamus while providing collateral branches to the red nucleus
Fibres terminate in cortex
Cordinates and controls movement while communicating with motor cortex
Disruption to arterial cerebral supply
Anterior cerebral: contra lateral limb weakness eg paralysis
Contralateral sensory deficit
Lower limbs impacted more than upper
Middle: as above but sensory LOSS and lower limbs affected more
Posterior: contralateral problems with vision severe blockages may cause hemiparesis and sensory deficits
Blood supply to brain
Internal carotid gives off a middle anterior and posterior cerebral artery
Posterior communicating joins them together
Middle cerebral supplies lateral sides anterior supplies medial and superior posterior supplies posterior
Sinuses in brain
Sinuses drain into internal jugular vein Posteriorly: Superior and inferior Sagittal sinus Straight sinus A confluence of sinuses Transverse and sigmoid sinus Anywriorly there is Superior and inferior petrosal and covernous
Lesion in primary motor cortex
Contralateral flaccid paralysis
Partial recovery
Babinskis
Supplementary motor cortex lesion
Contralateral splasticity and deep tendon reflexes
Lesion in frontal eye field
Difficulty moving eyes to opposite side
Primary and secondary somato sensory cortex lesion
Lose touch pressure and proprioception in secondary area there is decreased pain
Supranational gyrus lesion
Tactile and proprioceptive Agnosia
Decreased left right discrimination contralateral hemi- neglect and apraxia
Angular gyrus lesion
Dyslexia
alexia
agraphia
Motor dorsolateral pathways
Lateral corticospinal
Rubrospinal
Ventromedial pathways
Anterior corticospinal
Reticulospinal
Tectospinal
Vestibulospinal
Conscious pathways sensory
DCP
Spinothalamic tract
Unconscious pathways
Spinocerebellar
Spinotectal
Spinoreticular
Spino olivary
Climbing fibres
Inferior olive
