VBMS 212 Neurology Quiz 3

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5 FUNCTIONS THAT REQUIRE CEREBRAL CORTEX: Voluntary Movements

Conscious Sensory Perceptions
- localization via somatopic map

Conscious Proprioception

Conscious Pain Perception

Conscious Visual Perception
BLIND SIGHT: Cortical Blindness

Functionally Blind

Retina and midbrain cortex are functional
- tf subconscious visual awareness
- tf visual processing below level of cortex
5 AFFECTS OF LESIONS OF CEREBRAL CORTEX: UMN Signs

Sensory Deficits

Consciousness

Behavior

Learning
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
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
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
SUBCORTICAL STRUCTURES OF CEREBRUM FOUR: Olfactory System

Basal Nuclei

Hippocampus

Amygdala

All involved in behaviour
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
LIMBIC SYSTEM TARGETED BY WHICH DISEASE: Rabies
AMYGDALA: Recognition of Emotions
- ie recognizing and producing fear reaction
HIPPOCAMPUS: Creating NEW memory
- memories before lesion are intact
OLFACTORY SYSTEM: Odours Stimulate
- memories
- emotions
PSHYCOMOTOR SEIZURES: Abnormal Activity in Limbic System
- sudden unusual behavior
- sudden fear for no reason
- sudden aggesion
- snapping at phantom flies

Rare
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
SEIZURE 3 STAGES: Preictal Stage

Period of Ictus

Post Ictal Stage
- animal may be
~~ depressed
~~ disoriented
~~ sleep
- lasts hours to days
GENERALIZED MOTOR SEIZURES: 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
OPISTHOTINUS: 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
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
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
MOTOR CONTROL: Involves many regions of Brain
- Cerebral Cortex
- Brainstem
- Spinal Cord
- Thalamus
- Basal Ganglia
- Cerebellum
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
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
RED NUCLEUS: Flexors and Extensors

Net Exitatory effect on FLEXORS

Larger effect on DISTAL limbs

Effects are CONTRALATERAL
VESTIBULAR NUCLEI: Net excitatory effect on EXTENSOR MUSCLES

Larger effect on PROXIMAL limbs

Effects are IPSOLATERAL
RETICULAR NUCLEI: Diffusely Distributed

Effects both EXTENSOR AND FLEXORS

Net excitatory effect on EXTENSORS

Effects are BILATERAL
SPINAL REFLEX CIRCUITRY: 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
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
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
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
THREE STRUCTURES INVOLVED IN MOTOR CONTROL NOT UMN: Basal Nuclei
- Cerebral cortex

Subcortical Structures
- diencephalon
-
-
- thalamus
- midbrain

Cerebellum
BASAL NUCLEI: 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
SUBCORTICAL STRUCTURES: 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
CEREBELLUM: 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
CAUDAL CEREBELLAR PEDUNCLE: Proprioceptive Afferent Input
- unconscious proprioceptive input
~~ spinocerobellar tract
~~ Front limb
~~-- cuneocerobellar
~~ Hind limb
~~-- Dorsal and ventral lateral
MIDDLE CEREBELLAR PEDUNCLE: 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
ROSTRAL CEREBELLAR PEDUNCLE: Mainly contains output from cerebellum to
- Brain Stem UMN
- Cerebral Cortex UMN
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
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
CONTROL OF POSTURE: 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
EXTENSOR RIGIDITY: Caused by Lesion that disrupts Inhibitory Pathway from Cerebral Cortex
- increased muscle tone
~~ pronounced in Extensor muscles
- Subsides after one week
DECEREBRATE RIGIDITY: 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
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
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
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
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
MICTURATION COMPLETE LESION: Anywhere along detrusor reflex arc
- Inability to contract detrussor muscle

Anywhere along sphinter spinal reflex arc
- leakage
~~ relaxation of sphincter
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
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
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
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
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
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
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
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
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
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
CHOROID PLEXUS: Produce CSF

Two in Lateral Ventricles
- one in each

One in Third Ventricle

One in Fourth Ventricle
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
CSF COMPOSITION: Compared to Blood

99% H2O
- hypotonic to blood

Acellular

Very Low Protein

Lower Glucose

Lower pH

Same Osmolarity
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
CSF THREE FUNCTIONS: Act as lymphatic system to releive brain pressure

Nutrition

Cushion Brain
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
EDEMA DEFINITION 3 TYPES: Accumulation of fluid in Extra Cellular Space
- significant in CNS because enclosed space

Vasegenic

Interstitial

Cytogenic
EDEMA VASOGENIC: Breakdown of BBB

Increased capillary permeability
- increased flow into extra cellular space

Tumors

Infection
EDEMA INTERSTITIAL: Increase water flow into CSF

Flow of CSF into sub aracnoid space blocked
- blockage of ventricular system
- blockage of Lateral Aperatures

Tumors
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
EDEMA TREATMENT: Mannitol
- not excreted
- increases plasma osmolarity
- pulls water from CSF
- one time treatment

Steroids
- stabilize cell membranes
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

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