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68 Cards in this Set
- Front
- Back
5 FUNCTIONS
THAT REQUIRE CEREBRAL CORTEX |
Voluntary Movements
Conscious Sensory Perceptions - localization via somatopic map Conscious Proprioception Conscious Pain Perception Conscious Visual Perception |
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BLIND SIGHT
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Cortical Blindness
Functionally Blind Retina and midbrain cortex are functional - tf subconscious visual awareness - tf visual processing below level of cortex |
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5 AFFECTS OF
LESIONS OF CEREBRAL CORTEX |
UMN Signs
Sensory Deficits Consciousness Behavior Learning |
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LESIONS OF CEREBRAL CORTEX
UMN SIGNS |
Deficits in Voluntary Movement
- paresis - paralysis Normal to increased muscle tone Deficits in Conscious Proprioception - knuckling - abnormal gait UNILATERAL LESIONS PRODUCE DEFICITS ON CONTRALATERAL SIDE |
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LESIONS OF CEREBRAL CORTEX
SENSORY DEFICITS |
Hypalgesia aka Hypoalgesic
- loss of conscious peception of feeling Domestic Animals - difficult to detect - usually found in head because head represents major portion of somatosensory cortex - ie muzzle Visual Cortex - blindness NOT LOCALIZING - because many other lesions produce the same signs |
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LESIONS OF CEREBRAL CORTEX
CONSCIOUSNESS |
Affects level of consciousness
- depression to coma Consciousness involves - all regions of cortex - brain stem including medulla pons midbrain thalamus ascending reticular activating system - DOES NOT INVOLVE SPINAL CORD |
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SUBCORTICAL STRUCTURES
OF CEREBRUM FOUR |
Olfactory System
Basal Nuclei Hippocampus Amygdala All involved in behaviour |
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LIMBIC SYSTEM
5 COMPONENTS |
Coordinates and controls behaviour Associated with STRONG EMOTIONS
- Fear - Rage - Pleasure - Sexual Drive Olfactory System Hippocampus Amygdala Hypothalamus Parts of Cerebral Cortex |
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LIMBIC SYSTEM
TARGETED BY WHICH DISEASE |
Rabies
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AMYGDALA
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Recognition of Emotions
- ie recognizing and producing fear reaction |
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HIPPOCAMPUS
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Creating NEW memory
- memories before lesion are intact |
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OLFACTORY SYSTEM
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Odours Stimulate
- memories - emotions |
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PSHYCOMOTOR SEIZURES
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Abnormal Activity in Limbic System
- sudden unusual behavior - sudden fear for no reason - sudden aggesion - snapping at phantom flies Rare |
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LESIONS OF CEREBRUM
BEHAVIOR FIVE |
Pacing
Circling - unilateral lesion - circles to side of lesion - larger circles Head Pressing - also lead poisoning Tremors - especially at rest - tf NOT cerebellar intention tremors Seizures - neuronally based - could also be thalamic - Generalized Motor Seizure - Opisthotinus - Partial Motor Seizures ~~ affects heas or specific part of body |
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SEIZURE
3 STAGES |
Preictal Stage
Period of Ictus Post Ictal Stage - animal may be ~~ depressed ~~ disoriented ~~ sleep - lasts hours to days |
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GENERALIZED MOTOR SEIZURES
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Involve whole body
Animal Unconscious Lateral Recumbrancy Limbs Tonically (ridgedly) extended May have CLONIC CONTRACTIONS - ridgid oscillations - antagonistic muscles excite each others stretch recptors - initiate oscillating myotatic reflex |
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OPISTHOTINUS
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Activation of ALL EXTENSOR MUSCLES in body
Pupilary Dilation Salivation Chewing Motions Usually last a few inuctes - depends on cause Behaviour Changes in PreIctal Period - staring - restlessness - run and hide |
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SEIZURES
MECHANISMS |
All seizures due to neurons which become SPONTANEOUSLY ACTIVE
Activity spreads to surrounding meurons Mechanism is unknown Involves large parts of CORTEX - due to extensive connections Spreads between left and right hemispheres via CORPUS CALLOSUM Typically Common Source of Activation - ie epillepsy |
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SEIZURES
CAUSES 3 |
Metabolic
- hyperglycemia - hypoxia - toxins Neurologica - tumors - trauma - inflammation - infection Epilepsy - idiopathic - describes pattern of discrete seizure in the same animal with no known cause - tend to be classic Generalized Seizures ~~ pre and post ictal phases |
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MOTOR CONTROL
|
Involves many regions of Brain
- Cerebral Cortex - Brainstem - Spinal Cord - Thalamus - Basal Ganglia - Cerebellum |
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MOTOR CONTROL
MOTOR CORTEX |
Corticospinal Tract
- aka internal capsule - fibre bound output of motor cortex through brain stem - no synapses ~~ has collaterals - travel directly to spinal cord - Cerbral Peduncles ~~ passage through ventral surface of Midbrain - Pyramids ~~ passage through hind brain |
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MOTOR CONTROL
BRAIN STEM |
Indirect syanpse of UMN
Most important motor path of animals - strong influence onf LMN Red Nucleus - Mid Brain Vestibular Nucleus - Medulla Reticular Nucleus - Pons and Meddula Note - Cerebral Cortex UMN affect LMN of Brain Stem |
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RED NUCLEUS
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Flexors and Extensors
Net Exitatory effect on FLEXORS Larger effect on DISTAL limbs Effects are CONTRALATERAL |
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VESTIBULAR NUCLEI
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Net excitatory effect on EXTENSOR MUSCLES
Larger effect on PROXIMAL limbs Effects are IPSOLATERAL |
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RETICULAR NUCLEI
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Diffusely Distributed
Effects both EXTENSOR AND FLEXORS Net excitatory effect on EXTENSORS Effects are BILATERAL |
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SPINAL REFLEX CIRCUITRY
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Spinal Cord contains circuitry for reflexes
- withdrawal - crossed extensor - locomotion - scratching Cat transected T3-L3 - no motor neurons in this region - initially hypertonic - with training can walk without cerebrum - hip extension important to generate flexion |
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THREE BEHAVIORS
THAT REQUIRE INPUT FROM BRAIN STEM |
Via
- Red nuclei - Vestibular nuclei - Reticular nuclei Initiating Movement Balance Control Changing Direction If cerebral cortex and cerebellum transected - can walk - can right self |
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FOUR BEHAVIORS
THAT REQUIRE INPUT FROM CEREBRAL CORTEX |
voluntary movement
volunatry direction changes fine motor control of movement - navigation - rough terrain reflexes associated with concious proprioception - knucling ~~ UMN tell LNM to invert paw - hopping |
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LATERAL OR VENTRAL
FUNNICULUS WHITE MATTER DAMAGE |
Note that will not see UMN signs if LMN damaged
Note that sensory neurons also run in Lateral Funiculus C1-C5 - UMN for and hind limbs - LMN in neck ~~ hard to detect C6-T2 - UNM Hind Limb - LMN Fore Limb T3-L3 - UMN Hind Limb - LMN Trunk ~~ Paniculus Reflex L4-S2 - LMN Hind Limb - Femoral Nerve ~~ L456 ~~ Quads ~~-- patellar reflex ~~-- weight bearing - Sciatic Nerve ~~ L67S12 ~~ enervates everthing else in hind limb - lesion in L45 ~~ LMN Quad ~~ UNM in rest of hindlimb via sciatic |
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THREE STRUCTURES
INVOLVED IN MOTOR CONTROL NOT UMN |
Basal Nuclei
- Cerebral cortex Subcortical Structures - diencephalon - - - thalamus - midbrain Cerebellum |
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BASAL NUCLEI
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Involved in INITIATION of movement
- Huntingtons Disease - Parkinsons Disease - Terrets - Dystonia ~~ repetitive movements characterized by abnormalities of coordination ~~ star thistle poisoning in horses ~~ Substantia Nigra ~~-- midbrain structure of one of the basal nuclei ~~ unable to initiate muscles of mastication |
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SUBCORTICAL STRUCTURES
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Receive input from cerebral cortex
Feedback to cerebral cortex via thalamus - subcortical feedback loop - no direct influence over LMN Planning and correct execution of complex movements Important in initiation of movement Important in switching between movements |
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CEREBELLUM
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Not directly involved in control of LMN
- tf lesions do not produce paresis and other UMN signs General Functions - coordinates and refines ongoing movement - involved in maintenance of equillibrium and body posture Lesions - Mild ~~ uncoordinated movements ~~ hypermetria - Severe ~~ loss of equlllibrium ~~ abnormal body postures ~~ associated with vestibular system and pathways Receives input from - UMN - Proprioceptive afferents and efferents ~~ compares reality with plan ~~ makes corrections via input to UMN Vermis - Medial and Dorsal - wraps ventrally and longitudinally Lateral Hemisphere Connected to branstem via Cerebellar Peduncles - Rostral - Middle - Caudal - arranged medial lateral |
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CAUDAL CEREBELLAR PEDUNCLE
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Proprioceptive Afferent Input
- unconscious proprioceptive input ~~ spinocerobellar tract ~~ Front limb ~~-- cuneocerobellar ~~ Hind limb ~~-- Dorsal and ventral lateral |
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MIDDLE CEREBELLAR PEDUNCLE
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Continuation of Tranverse Fibres of Pons
- travel laterally then dorsally to form middle cerebellar peduncle Input from UNM in Cerebral Cortex - neurnons first synapse in pons |
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ROSTRAL CEREBELLAR PEDUNCLE
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Mainly contains output from cerebellum to
- Brain Stem UMN - Cerebral Cortex UMN |
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CEREBELLUM
3 FUNCTIONAL DIVISIONS |
Highest Density in CNS
- repeating circuit patterns - tf performs similar functions Vestibulor Cerebellum - flocculo nodylar node - inputs from vestibular nuclei - outputs to vestibular nuclei - equillibrium and postural control - primative part of vestibular system Spinao Cerebellum - vermis and parvermis - inputs from brain stem UMN - outputs to brain stem UMN - posture and limb movement and control Cerebro Cerebellum - Lateral hemispheres - inputs from cerebral cortex via synapes in pons - outputs to cerebral cortex via thalamus - planning movement - motor learning ~~ initially cortex then cerebellum |
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CEREBELLAR DAMAGE
2 TYPES 5 SIGNS |
Diffues Damage
- Bilateral signs - abnormal development - BVD, Toxins, genetic - PRESSURE ~~ herniation through foramen magnum impacts cerebellum Focused Damage Ataxia - most common sign - incoordination ~~ not specific to cerebrum - increased muscle tone but NO PARESIS ~~ especially extensor muscle ~~-- vestibular nucleus strongly inhibitory DYSMETRIA - inability to regulate movement ~~ rate ~~ range ~~ force - Hypermetria most common - produces INTENTION TREMOR ~~ not present at rest ~~ associated with start of movement ~~ undershoot/overshoot ~~ ofene associated with head ~~ SPECIFIC to cerebellum - influences knucling response ~~ delayed then rapid motion TRUNCAL ATAXIA - more severe lesion - vermis and paravermis - broad base stance - sway ~~ lateral or longitudinal - staggering gate - tendency to fall - specific if no other signs VESTIBULAR DISEASE - loss of equillibrium - very diffuse and sever - involvement of Vestibular Cerebellum - Nystagmus - abnormal head tilt OPISTHOTONUS - extremely severe lesions - recumbrancy with ~~ extended limbs ~~ arched spine - usually herniation of cerebellum into foramen magnum - specific if sole sign ~~ usually associated with seizures |
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CONTROL OF POSTURE
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Trunk and Limbs
- head is via vestibular system Posture requires maintenance at Rest and in Motion - tf constant activity in postrual muscles ~~ axial muscles ~~ limbs ~~-- proximal extensors and flexors ~~-- distal extensors Postural control is coordinated by - Red Nuclei ~~ Inhibition of postural muscles - Vestibular Nuclei ~~ Excitation of postural muscles - Reticular Nuclei ~~ Excitation of postural muscles - tf postural control is maintained by brain stem UMN - tf postural control is acheived by balance between Excitation and Inhibition Postural UMN are influenced by - Cerebellum ~~ inhibits vestibular nucleus - Cerebral Cortex ~~ net inhibitory inputs to vestibular and reticular nucleus |
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EXTENSOR RIGIDITY
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Caused by Lesion that disrupts Inhibitory Pathway from Cerebral Cortex
- increased muscle tone ~~ pronounced in Extensor muscles - Subsides after one week |
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DECEREBRATE RIGIDITY
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Transection or Lesion
- experimental - mid brain hemmorahge - caudal to midbrain ~~ tf los of Red Nuclei inhibition - severe extension - can be relieved by activating cerebellum ~~ ie increase inhibition |
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CONTROL OF MICTURATON
DETRUSSOR REFLEX WHAT IS INVOLVED |
Detrussor Reflex
- detrussor muscle ~~ smooth muscle ~~ stretch receptors ~~ parsympathetic cholenergic receptors ~~ sympathetic catecholamine receptors ~~-- Beta Adrenergic body of bladder ~~-- Alpha Adrenergic neck of bladder - S123 ~~ Parasympathetic preganglionic motor ganglion to detrussor muscle - pelvic nerve ~~ S123 ~~ sensory stretch afferents to Pons ~~ conscious stretch afferents - L1-L4 ~~ detrussor stretch afferent inhibitory synapse ~~ Sympathetic trunk chain ganglia - hypogastric nerve ~~ sympathetic ~~-- L1-L4 ~~-- Sympathetic postganglionic motor fibres ~~ conscious stretch afferents - Pons ~~ unknown integration - Cerebellum ~~ inhibits detrussor reflex at level of Pons - Thalamus - Cortex ~~ Conscious active control ~~ must be learned |
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CONTROL OF MICTURATON
SPHINTER REFLEX WHAT IS INVOLVED |
Sphincter Reflex
- Urethralis (sphincter) muscle ~~ skeletal muscle ~~ stretch receptors - S12 ~~ stretch reflex ~~ detrussor stretch afferent inhibitory synapse - voluntary UMN synapse - Pudendal Nerve ~~ S12 ~~ sensory afferent ~~ somatic motor efferent - Cerebral Cortex ~~ voluntary control |
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MICTURATION
BLADDER FILLING |
Sphincter
- Normal state is excitation and contraction via spinal stretch reflex - stretch receptors on relaxed bladder do not inhibit spinal stretch reflex - cerebral cortex conscious control maintains contraction Bladder - SNS excitation facillitates filling via ~~ relaxes wall of bladder via beta adrenergic receptors ~~ contracts neck of bladder via alpha adrenergic receptors - cerebellum inhibits detrusser reflex at level of pons - cerebral cortex inhibits detrusser reflex at level of pons |
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MICTURATION
URINATION |
Sphincter
- cerebral cortex concious UMN releases inhibition to somatic motor efferent - excitation of detrussor muscles stretch afferents inhibit somatic motor efferent Bladder - cerebral cortex releases inhibition of detrussor reflex at level of pons - detrussor stretch afferents inhibit SNS enervation ~~ removes relaxation of bladder wall ~~ removes excitation of bladder neck - detrussor reflex at level of pons contracts detrussor muscle |
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MICTURATION
COMPLETE LESION |
Anywhere along detrusor reflex arc
- Inability to contract detrussor muscle Anywhere along sphinter spinal reflex arc - leakage ~~ relaxation of sphincter |
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MICTURATION
CEREBRAL CORTEX LESION |
Voluntary Control
- Absent Bladder - sustained detrussor reflex ~~ Normal - Tone ~~ Normal - Volume ~~ variable - Residual Urine ~~ none Sphinter - Voluntary Control ~~ Absent - Pernial Reflex ~~ normal to increased - Tone ~~ normal to increased - Synergy with Detrussor ~~ normal |
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MICTURATION
CEREBELLAR LESIONS |
Bladder
- Voluntary Control ~~ normal or increased frequency - Sustained detrussor reflex ~~ Normal or hyperreflexic - Tone ~~ Normal - Volume ~~ decreased - Residual Urine ~~ none Sphincter - Voluntary Control ~~ normal - Pernial Reflex ~~ normal - Tone ~~ normal - Synergy with Detrussor ~~ normal |
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MICTURATION
PONS LESION |
Bladder
- Voluntary Control ~~ absent - Sustained detrussor reflex ~~ absent - Tone ~~ variable - Volume ~~ increased - Residual Urine ~~ increased Sphincter - Voluntary Control ~~ absent - Pernial Reflex ~~ normal to increased - Tone ~~ increased - Synergy with Detrussor ~~ absent |
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MICTURATION
PONS TO SACRAL CORD COMPELTE LESION |
Bladder
- Voluntary Control ~~ absent - Sustained detrussor reflex ~~ absent ie areflexia - Tone ~~ variable - Volume ~~ increased - Residual Urine ~~ increased Sphincter - Voluntary Control ~~ absent - Pernial Reflex ~~ normal to increased - Tone ~~ normal to increased - Synergy with Detrussor ~~ absent |
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MICTURATION
PONS TO SACRAL CORD PARTIAL LESION |
Bladder
- Voluntary Control ~~ absent - Sustained detrussor reflex ~~ absent ie areflexia or increased ie hypereflexia - Tone ~~ variable - Volume ~~ decreased according to Muir - Residual Urine ~~ variable Sphincter - Voluntary Control ~~ may be present - Pernial Reflex ~~ normal to increased - Tone ~~ normal to increased - Synergy with Detrussor ~~ absent |
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MICTURATION
SACRAL SPINAL CORD S123 LESION |
Bladder
- Voluntary Control ~~ absent - Sustained detrussor reflex ~~ absent ie areflexia - Tone ~~ decreased - Volume ~~ increase - Residual Urine ~~ increased Sphincter - Voluntary Control ~~ absent - Pernial Reflex ~~ absent - Tone ~~ decreased - Synergy with Detrussor ~~ absent |
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MICTURATION
PERIPERAL PUDENDAL LESION |
Bladder
- Voluntary Control ~~ normal - Sustained detrussor reflex ~~ normal - Tone ~~ normal - Volume ~~ normal - Residual Urine ~~ none Sphincter - Voluntary Control ~~ absent - Pernial Reflex ~~ absent - Tone ~~ decreased - Synergy with Detrussor ~~ absent |
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MICTURATION
LACK OF SEX HORMONES |
Hormone Sensitive Incontinence
Bladder - Voluntary Control ~~ normal - Sustained detrussor reflex ~~ normal - Tone ~~ normal - Volume ~~ normal - Residual Urine ~~ none Sphincter - Voluntary Control ~~ absent - Pernial Reflex ~~ absent - Tone ~~ decreased - Synergy with Detrussor ~~ absent |
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CEREBROSPINAL FLUID
FACTOIDS |
No connective tissue in CNS
- originates form Neuroectoderm - no lymphatics - tf no typical system to deal with extracellular fluid - limited space tf SUSCEPTABLE TO PRESSURE |
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VENTRICULAR SYSTEM
|
Two Lateral Ventricles
- one in each cerebrum - telencephalon Third Ventricle - diencephalon Mesencephalic Aquaduct - mid brain Fourth Ventricle - pons and medulla Entire ventrical System - lined with Ependymal cells - filled with CSF |
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CHOROID PLEXUS
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Produce CSF
Two in Lateral Ventricles - one in each One in Third Ventricle One in Fourth Ventricle |
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CSF
PRODUCTION |
Produced through Blood-CSF Barrier
- blood vessels in close opposition to emendymal cells - flow of nutrients is ONE WAY into CSF - Ependymal cells have tight junctions in region of Coroid Plexus ~~ tf nutrients are transported via active transport ~~-- high number of glucose transporters ~~ oxygen and CO2 diffuse ~~ tf NOT filtrate of blood Normally continuously produced - turned over 4 to 5 times daily - 150 ml human Rate of Production - regulated by osmolarity of blood - hypertonic blood decreases production ~~ tf Mannitol used to treat increased CSF pressure ~~-- one time treatment - hypotonic blood increases production |
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CSF
COMPOSITION |
Compared to Blood
99% H2O - hypotonic to blood Acellular Very Low Protein Lower Glucose Lower pH Same Osmolarity |
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FLOW OF CSF
|
Cranial to Caudal
- through ventricles to LATERAL APERTURES - connect to SUBARACHNOID SPACE ~~ holds most of CSF volume - fluid absorbed from Subarachnoid space through ARACHNOID VILLI - passes into Venus System ~~ one way flow via pressure differential Brain-CSF Interface - two way flow in majority of ventricular system ~~--leaky junctions of ependymal cells - one way flow in regions of Choroid Plexi ~~-- tight juctions of Ependymal cells Blood CSF Barrier - production of CSF - blood closely apposed to Ependymal cells ~~-- tight juctions ~~-- one way flow into CSF ~~-- diffusion and active transport Blood Brain Barrier - vessels travel along pia and enter brain tissue - Unique Tight Juntions between Endothelial Cells ~~-- main component of BBB ~~-- diffusion or active transport ~~-- very few endocytotic vesicles - material passes BBB into Extra Cellular Matrix ~~-- passes into CSF ~~-- passes into Intra Cellular Space |
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CSF
THREE FUNCTIONS |
Act as lymphatic system to releive brain pressure
Nutrition Cushion Brain |
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BBB
2 REGIONS WITHOUT |
Area Postrema
- Medulla near Chemorceptor Trigger Zone ~~-- vomition Neurohypothesis - transport of substances (hormones) into blood - portal system ~~-- stimulation of Anterior Pituitary Tanycytes - isolate regions without BBB from rest of brain - ie protect from non discriminant movement of material No Tight Junctions in Edothelium |
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EDEMA
DEFINITION 3 TYPES |
Accumulation of fluid in Extra Cellular Space
- significant in CNS because enclosed space Vasegenic Interstitial Cytogenic |
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EDEMA
VASOGENIC |
Breakdown of BBB
Increased capillary permeability - increased flow into extra cellular space Tumors Infection |
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EDEMA
INTERSTITIAL |
Increase water flow into CSF
Flow of CSF into sub aracnoid space blocked - blockage of ventricular system - blockage of Lateral Aperatures Tumors |
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EDEMA
CYTOGENIC |
Hypoxia
- general or ischemic - disrupts cellular metabolism - lowered ATP production - increased intracellular Na ~~-- Na/KATPase - water follows Na ~~-- cells swell Salt Poisoning - deprive of water then drink ad libum - hypoosmotic plasma ~~-- fluid flows into cells Swelling of cells not techically edema but same effect on CNS |
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EDEMA
TREATMENT |
Mannitol
- not excreted - increases plasma osmolarity - pulls water from CSF - one time treatment Steroids - stabilize cell membranes |
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HYDROCEPHALUS
|
Increased Volume of Ventricles
Congenital in dogs - domed headed breeds Any blockage of CSF - tumor - inflammation - may or may not be associated with Edema ~~-- ie if gradual flow pressue will adjust - occurance during development ablates cortex |