Module 8 Wk 1 Flashcards
What does the CNS develop from?
From the neural plate into the neural tube
What is the neural plate?
A specilised layer of ectoderm (outer layer of cells) tissue in developing embryo
what are the 3 regions of the brain that the neural tube expands and consricts to give rise too?
- prosencephoron (fore)
- mesebcephron (mid)
- rhombencephron (hind)
What are the components of the embryo forebrain?
- telencephalon - forms the cerebral hemispheres and houses lateral ventricle
- diencephalon - forms the thalamus and hypothalamus
what is the component of the embryo midbrain?
- the mesencephalon which includes cerebral peduncles (little feet) which is the connection between the brainstem and herbro hemispheres
what are the components of the embryo hindbrain?
- The metencephron which forms the pons and the cerebellum
- The myelencephalon
what is the function of the cerebrum of the brain?
Cognition and though processing in the left and right hemispheres
What is the function of the cerebellum?
Gate and balance
What is the function of the diencephalon?
Processing information
What is the function of brainstem?
Control of body physiology
What does folding of the cerebral cortex enchance?
- Folding greatly enchances the surface rea and vastli increase the potential for neural networks?
what is a way to desecribe sulci and gyri?
sulci is the valleys and gyri are the hills
How is the cerebrum divided into lobes
Based on cranial bones
What are the boundaries of the cerebrum divisions definedby?
Major fisures and smaller sulci
What seperates Frontal and parental divisions?
The central cruciate
What seperates the temporal from the frontal + parentail?
Lateral sulci
What is the function of the olfactory lobe (bulb)?
Smell
What is the function of the frontal lobe?
Behaviour, Speech, movement, problem solving
What is the function of the parietal lobe?
Associated with movement and orientation and involved in perceiving sensory information
What is the function of the temporal lobe?
Processes sound, vestibular sesations, smells while also being involved in percepion and emotion
What seperates the left and right hemispheres
Longitudinal fissure
what are the cerebrum functions?
- Involved in complex thought processes
- Receives and interprets sensory information
- Initiates voluntary muscle action
- Interacts with the limbic system - Moods, fear, pleasure also modulates memory
What is the function of the olfactory bulb?
transports odour signals to the cerebrum
What is the function of the cerebellum?
- coordinating movement
- Balance and gait
- Monitors position in space AND adjustments
- Also can influence speech
- Smooth muscle movement
What does the brainstem consist of?
- Pons
- medulla oblongata
- midbrain
what are the functions of the brain stem?
- breathing, coughing, sneezing
- Cardiac regulation, vasodilation
- Connection between brain and spinal cord
What does the diencephalon in the forebrain contain?
- epithalamus which forms the roof of the diencephalon and contains the pineal gland
- The thalamus
- Pituatary
- The hypothalamus
What is the bridge of white matter between left of the forebrain called?
The corpus callosum
what is the function of the corpus callosum?
To share infor between both sides of cerebrum
What makes brain so powerful?
- Connections between neurones achieves function
- White matter composed mainly of Axons
- Connections between regions of brain
what are he different connections between the regions of the brain?
- corpus callosum
- internal capsule
- peduncles of the cerebellum
what is the purpose of the internal capsule?
To connec cerebral hemispheres with brain stems
What is the function of the peduncles of the cerebellum?
connects cerebellum with pons and medulla
What is the deep nucle in the cerebrum?
Organised cluster of neurons
come back to this one - slide 20
T/F the thalamus and the hypothalamus also make brain powerful?
True
What is the name of the connection between the bilobe of the thalamus and what does it give rise to?
- Interthalmic adhesion
- Gives rise to the 3rd ventricle
What type of info converges on the thalamus?
Sensory
Describe meinges
A three layered membranous sheet that covers the brain and spinal cord
What are the three memberous layers in meninges?
- Dura mater (outermost)
- Arachonoid mater (middle)
- Pia mater (inner most)
T/F arrangment of meninges is diff between skull and vert column
True same layers but different attachemnts to surrounding structure
What is the spac called betwen pia and arachanoid mater and what does it contain?
- Arachanoid space
- Contains CSF
Describe Dura mater in terms of the spinal cord?
- Dura is a free tube structure - it merges with periosteam at foramen
What is the space between teh dura and forman of vert colum called and its purpose?
- Called epidural space
- Gives spinal cord more protection
List the big differences between spinal cord and skull when it comes to meninges
- The skull dura contributes inner periosteum of calvarium fusinf meninges to the calvarium
- epidural space in the skull is apotentail space vs and anatomical space in the vert colmun
- The dural folds divide in the CNS in skull
What is the cisternae manga?
An enlargement of the subarachanoid space
Where is the cisternae magna?
It is the space between the caudal surface of the cerebellum and the dorsal surface of the brainstem
Where would you take a CSF collection and how?
At the cisternae magna, flexion of the neck, enter at midline between occipital bone and C1
Describe the dural partitions at the op of crainium
- Falx cerebri - logitudibal fissure between hemispheres
- Tentorium cerebelli - transverse fissure between cerebral hemispheres and cerebellum
- Diaphragma sellae - is around the stalk of the pituatary
Describe the caudal fossa of the brain
- The caudal border is the rostral part of the cerebellum
- forebrain - cortex, thalamus, hypothalamus, midbrain (part of)
- crainal nerves - 1 and 2 (optic chaism)
- ventricles - lateral and third ventricles
Descride the caudal foss of the brain
- caudal border is the line between most caudal part of he foramen magnum
- cerebellum
- midbrain (part of)
- medulla oblongata - magoirity of cranial nerves (3-12)
- fourth ventricle
What do CT and MRI’s avoid that radiographs cant?
Superimposition
What is CT images really good for?
Skeleton and lungs
How does Ct work?
- X-ray beam passes through patient and strickes detectors
- X-ray tube and detectors rotate around patient
- cross section image is generated
What is the Cv of a CT image?
100-200Cv
What two things add together to produce back projection?
- Measurement of total beam attenuation along path
- Measurement at multiple angles and computer adds them all together
what is tissue attenuation?
The amplitude and intensity of ultrasound waves decrease as they travel through tissue
What is tissue attenuation measured in?
Hounsfield units
What can you do to hightlight specific tisue in CT?
Can adjust window centre and width
What is MRI really good for?
For soft tissue - CNS
What is the risk with MRI?
No ionising radiation but strong magnet
Describe how MRI works
- Body isplaced in a strong magnetic feild with a reciever coil
- protons align with magnetic field
- Then a transverse eectromagnetic pulse which gives protons energy for them to move from alignment with main feild
- As The protons relax back to main feild there is a change in signal detected by the reciever coil
- Image is then genereated by current going trough coil on detection
What are the two components of relaxation in MRI
T1 and T2
Describe T1 weighted sequence
- Hypointense (dark) tissues are fluid, cortical bone and gas
- isointense (grey) tissues are CNS, muscle and organs
HYperintense (white) tissues are fat
Describe T2 weighted sequences
- hypointense tissues are cortical bone and gas
- Isointense tissues are muscle, organ and CNS
- hyperintense tissues are fat and FLUID
what wil the neuro-ectoderm form?
The CNS
what is the rest of the ectoderm called?
Non-neural ectoderm
in the neural ectoderm what is the thick central part called?
The neural plate
What are the margins of the neural plate called?
Neural folds
What is the neural groove?
The sulcus of the neural plate
What does neuralation start of with?
Starts off with the folding process which includes the transformation of the neural plate into the neural tubule
Where does the notochord appear within?
mesoderm
what are the functions of the notochord?
- Define the embryonic midline
- Cellular inductor
- Vertebral precursor
- Signalling
Where does neural tube appear from?
The neural-ectoderm
Whats is the neural tube the precurser for?
The CNS
Describe the closure of the neural tube?
Formed from neural plate via zipping in caudal and cephalic directions from cervical region
What is the neural crest a precurser for?
For many types of cells
Describe how the cells from neural crest initially lie?
between the dorsal ectoderm and the neural tube but then will migrate to diff locations, settle and differenetaite
Name the three types of layers in neural tube
- initial monolayer
- germinal layer
- marginal layer
Describe the initial monolayer of the neural tube
Initial monolayer of neuroectodermal cells that are mitotically active so the layer will thicken
Describe the germinal layer of the neural tube
Called the mantle layer which includes immature eurons and spongioblastes differentaited
What is a immature neuron?
Precurser of the neuron
What is a spongioblast?
Precurser of the neuroglia
Describe the marginal layer of the neural tube?
It is the external layer formed of growing axonal process of the neural cell bodies in the mantle layer and will go onto form white matter
List the steps in the development of the CNS
- Induction
- Proliferation in germinal layer
- cellular migration
- differentiation
- establish connection
- apoptosis
At the level of the cranial neuropore what is produced?
3 vesicles
What are these three vesicles called?
- Prosencephalon
- mesencephalon
- rhombercephalon
Describe the development from the 3 vesicles to the 5 vesicles
- The prosencephalon splits into the telecephalon and the diencephalon
- the mesencephalon stays the same
- the rhombercephalon splits into the metancephalon and the myelencephalon
Describe the function of these 5 vesicles
- The telencephalon goes on to become cerebral hemisopheres and with diacephalon makes up the forebrain
- The mesencephalon makes up the mid brain
- The metancephalon becomes pons and cerebellum
- myelencephalon beccomes medulla
T/F malformations of the CNS can occur at anytime during development
True
What is the most commen nural tube defect?
Incomplete closure of the neural groove to form a neural tube
What are the two natures of neural tube closure?
- open and closed - open there is exposed neural tissue and leakage of CSF
What is cerebral aplasia?
Failure of telencephalic vesicles to develop causing absent cerbral hemispheres
What is the word used to decribe partial opening of the skull?
Crainochisis
What is meningocele?
Disturbance in seperation of surface ectoderm and neuroectoderm during final phase of neural tube formation
What does the disturbnace in meningocele cause?
Protrucion of brain and or meniges throgh opening in the skull cap
T/F menigocele is not always externally observed
TrueW
hat are some clinical signs of meningocele?
- seizures and or behavioural abnormalties
What is the definition of meningomylocele?
Failure occuring at the vertebral column that causes protrusion of the spinal cord and meninges trjough opening in vert
What is the definition of spinal bifida?
Failure to the closure of the dorsal aspect of the vertebrae - split vert
If many adjacent vertebrae are in volved in splitting what is this called?
rachischisis which is a different process due to failure of the vert arches to develop
what are the clinical signs of meningomyelocele?
- urinary or feaces incontinence
- paraphimosis in males
- paraparesis
what breeds do wee see meningomyelocele in and why?
- genetic factors
- french bull dog as has screwball tail and max cat as has no tail
What are the two types of neuronal migration disorders?
- Lissencephaly
- Polymicrogyria
what is the definition of lissencephaly?
Slow or failed neuronal migration of brain neurons resulting in a lack of development of the surface folding of the cerebrum
What is lissenecephaly characterized by?
A small, smooth-appearing cerebrum with rudimentary or absent gyri and sulci
What are clinical signs of lissencephaly?
- cognitive dysfunction
- abnormal behavoiur
- seizures
What are the causes of lissencephaly?
- suspected inherited condistion
what are the two types of destuctive processes that cause malformation in the CNS
- Hydranencephaly
- Porencephaly
What is the definition of polymicrogyria?
Abnormal neuronal migration of brain neurons causing excess cortical folding
What are the signs of polymicrogyria?
Blindless with or without other neuro deficits
what is the definition of hydrancephaly?
Almost complete loss of one or both cerebral hamispheres which is replaced by CSF
what are the signs of hydranencephaly?
- seizures
- cognitive disfunction
- mild deficits like uni or bi lateral
what is the difference between porencephaly and hydranencephaly?
Same physiopathology but the cavity formed is smaller and the insult occurs later in the developmental stage and effects a smaller region
What do you clinically see with poencephaly?
Usually clinically normal or just seixures in adulthood
What is the congenital amonoramlis of CSF pathway?
hydrocephalus
What is the definition of cogenital hydrocephalus?
Abnormal flow or absorbtion of CSF
What does abnormal flow or absorbtion in the CSF cause?
causing the accumulation of CSF withing the cranial cavity which reduced the thickness of cerebral cortex
When seeing cogenital hydrocephalus what causes the excess CSF?
Due to absent or small size of mesencephalic aquduct, increased CSF production from choriod plexus, abnormal CSF absorbtion due to malformation/ lack of aracanoid villi
what are the signs of congenital hydrocephalus?
- dome shaped head
- persistant fontanelle
- ventralateral strabismus
- abnormal behavoiur
- cognitive dysfunction
- blindless
- ataxia
- death
what is the definition of cerebellar aplasia?
complete or almosy complete absence of cerebellare tissue
What is the cerebellum replaced by when aplasia takes place?
CSF
what are clinical signs of cerebellar aplasia
unable to stand up after birth or even to right themselves in a sternal position
what is the definition of cerebelllar hypoplasia?
Uniform absence of cerebellar tissueha
what are the clinical signs of cerebellar hypoplasia?
cerebellar ataxia from birth or shortly thereafter that do not progress
what cells make up nervous tissue?
- neurons
- neuroglia
- ependymal
what is the function of he cell body of a neuron?
- supply centre of neuron
- contains nuclues and cytoplasmic organelles
- nissl body has concentation of ribosomes for protein syntheisis
what is the function of dendrites to neuron?
- processes that ramify from the cell body
- provide large surface area for contact with other neurons
What is the function of an axon in a neuron?
A prominent dendrite that extends from the cell body
What does it mean if an axon is mylinated?
It means there is a membernaous sheath wrapped around it
What is an axon terminal?
- point of synapse
- contact with other neurons
- commuincation with chemicals
what are the 4 morphologically different neurons?
- multipolar
- Bipolar
- Unipolar
- Pseudounipolar
where would you find multipolar neurons and describe them anatomically?
- Find them throughout the brain and spinal cord
- They have several dendrites witha single axon
Describe a bipolar neuron morphalogically?
They have one main dendrite receiving stimuli and one axon delivering impulse
Describe a unipolar neuron morphalogically?
Has short externsion from cell body, one dendrite and one axon that fuse together
Descrube a pseudonipolar neuron
Begin as bipolar and fuse with development to give the unipolar neuron
what is the function of afferent neurons?
They recieve sensoery input directly from dendrited or from adjacent cells and convey it as an impulse to the CNS
How does the sensory impulse go from affeerent neuron to CNS?
Via cranial nerves or spinal nerves
What is the function of efferent neurons?
To convey impulse from CNS to target via cranial or spinal nerves
Where are interneurons located and what are their functions?
They are found in the CNS and they are the connection between the sensory and motor neurons (afferent and efferent)
What is an example of a cell that has bipolar neurons?
Olfactory cells
Describe how olfactory cells work?
- they detect odour via chemical receptors on bipolar neurons
- then axons from olfactory mucosa synapse at the olfactory bulb conveying impulse to the cerebral cortex
GIve 4 examples of sensory neurons (unipolar)
- meissners corpuscles
- merkel
- pacinian
- nococeptors
describe what kind of receptor meissners corpuscles are?
They are touch receptors mass of dendrite endings
Describe what a kind of receptor a merkel are?
Touch receptor with free nerve endings
Describe what kind of receptor pacinians are?
Pressure receptors that have laminated capsule
Describe what kind of receptors nociceptors are
They are pain receptors that have free nerve endings
What type of neurons are purkinje and pyramidal neurons?
multipolar neurons
what gives dendrites of multipolar neurons a levels of plasticity?
the dendritic spine can alter shape
where are purkinje neurons found and what is function?
cerebellum + controls gait
where are pyramidal neurons found and what is function?
throughout cortex/ spinal cord + thought processing
what are the different types of communication you can have between neurons?
- simple series circuit
- divergent series
- convergent series
- reverberating
- parallel after discharge
Describe simple series communication between neurons
A simple presynaptic stimulates a single postsynaptic
Describe divergent series communication between neurons
Single presynaptic stimulating several postsynaptic
Describe convergent series communication between neurons
Several neurons stimulating a single neuron
Describe reverberating communication between neurons
The circuit feedbacks to stimulate early points in cascade
Describe parallel after discharge communication between neurons
Where different neurons ina cascade converge on a common neuron
Where is grey matter in brain?
Outer rim of the brain and internal nuclei in brain
where is white matter in brain?
in middle
What makes up grey matter?
- neuronal cell bodies
- dendrites
- astrocytes
what make up white matter?
- myelinated axons
- oligodendrocytes - myelinated cells in CNS
- microglia
what is the difference between brain and spinal cord when it comes to grey and white matter?
In spinal cord the white matter is on the outside and grey forming a horn
what 3 layers is the PNS enclosed by?
- epineurium
- perineurium
- endoneurium
if an axon is not mylenated what does not have?
Do not have the same protection as spinal cord or brain
What is neuroglia?
The supporting cells of the CNS
What are the three types of surporting cells of the CNS?
- astrocytes
- oligondendrocytes
- microglia
Describe Astrocytes morphologically and functionality
- star shaped
- involoved in BBB and removal of neurotransmitters from synaptic cleft
Describe oligodendrocytes morphologically and functionality
- found mainly in white matter
- produce myelin around axons
Describe microglia morphologically and functionality
- ovoid shape which changes on activation
- they are resident immune cells that remove debris and bacteria
Qhat are the gaps in myelin along the axon called?
Node of ranvier
what cells myelinate axons in the PNS?
schwann cells
When do astrocytes become reactive?
In many neurodegenerative disorders and extended processes
What do astrocytes produce?
Produce trophic substances and can uptake glutamate and potassium
what can astrocytes form?
scar tissue to block formaion of neuronal tracts
what are the two barriers in the brain and spinal cord microenviroment
- BBB
- Blood - CSF barrier
Describe what makes up Blood-CSF barrier
- choroid plexus produces CSF
- CSF enters subaracacnoid space
- CSF then eneters spinal canal and circulates CNS
What is the function of the Blood-CSF barrier?
Gives a protective layer and acts as a boyance
Describe the ependymal cells of the choroid plexus?
They are cuboidal or columnar epithelial which line the vesicles of the prain and spinal cord
why are the ependymal cells of the choroid plexus cilated?
To regulate CSF movement and turnover
Where and how is CSF absorbtion regulated?
- Aracanoid villi
- They project into the sinus through the dura matter
- when pressure in subarachanoid space is higher than sinus csf will move into sinus
- Higher pressure in sinus will close the tubules of the arachanoid villis
what mediates AP to synaptic cleft?
neurotransmitters
what kind of grandient can neurotransmitters cause on postsynaptic sites?
excitory or inhibitory
what is the main function of myelin
saves energy and makes speedy transfer of info
what does an exitory gradienr do to post synaptic membrane?
It depolarises it so reasting membrane potentail nearer the threshould for AP
what does an inhibitory gradient do to post synaptic membrane?
It hyperpolarises it so resting membrane potentail is further away from threshold
what does excitatory gradient induce and stimulate?
- Induces excitatory postsynaptic potentail
- stimulates influx of positive ions and an efflux of negative ions
what does inhibitory gradient induce and stimulate?
- imduces inhibitory postsynaptic potential
- stimulates and influx of negative ion and efflux of positive ions
what is an inontropic receptor?
- Has a ligand gated ion channel, contains a ligand binding site
- ligand binding modulates opening probability and ion flux
what is a metabotropic receptor?
- Contains a ligand binding site, couples to a G protein then have influence on ion channel
- production of second messanger modulates ion channal
give an example of a neurotransmitter that can be both iontropic and metabotropic?
Acetylcholine
list the events at the synapse during exocytosis of NT
- Nerve impulse travels along axon to the presynaptic terminal.
- Impulse causes depolarisation that activates and opens calcium channels
- Calcium activates a series of protein events on synaptic vesicles leading to synaptic vesicles fussion with the membrane and release the NTs into synaptic cleft
- NTs bind to receptors on postsynaptic membrane ion channels (dendrites)
- Initiates post synaptic depolarisation
- Induces nerve impulse
list the 3 exitatory nurotransmitters
- glutamate
- asparate
- nitric oxide
list the inhibitory neurotransmitters
- glycine
- GABA
- serotonin
- dopamine
what are the two neurotransmitters that can be both excitatory and inhibitroy
Acetylcholine and nor epinephrine
what does glutamate functions as?
an excitatory AA
what is glutamates function?
involoved in the cogition and emotion
what does removal of glutamate from synaptic cleft involve?
astrocytes
what roles does astrocytes play in removal of glutamate from synaptic cleft?
- can remove gluamate by excitory amino acid transporters
- converts most glutamate to glutamine
after astrocytes make glutamine what happens to it?
It can be taken up by neurons and converted to glutamate
Define afferent?
The neurons and pathways they form convey sensory stimuli to the spinal cord and ultimatly the brain
Define efferent?
The neurons and pathways they form convey the motor stimulus to the muscles
what kind of organisation does the spinal cord have?
segmental
what does a spinal cord segment give rise to?
one pair of spinal nerve roots
In relation to spinal nerves what is aresult of 8 cervical cord segments but only 7 cervical vertebrae?
Cervical spinal nerves except C1 and 8 leave the vertebrae canal cranial to vertbrae of the same number and the remaining spinal nervels leave the vert canal caudal to vert of the same number
why does a young embryos neural tube extends the entire length of vert column?
Because the neural tube and vert column develop at a similar rate during their early stages of development
What happens to the rate of growth of neural tube as embryo dvelepos more?
It slows down while the vert column continues so the rate of growth is no longer consistant with one another
What is the group of dorsal and ventral roots of the spinal nerved in the lumbro-sacral vertebral canal called?
cauda equina
what are the three anatomical parts of the caudal equina?
- Conus medullaris - a caudal elongation of the spinal cord
- Filum terminale - a thin cord of fibrous tissue that attaches the conus medullaris to the caudal vertebrae
- lumbar, sacral and caudal nerev roots and nerves
Where are the two Intumescences of the spinal cord?
- cervical intumescences at the level of C5-T1 which involves spinal sements C6 - T2
- Lumbar intumescencesl at the level of L3-L6 which in volves spinal segments L4-S3
what are the two enlargements caused by?
An increasement of white matter and cell bodies that are associated with the innervation of the thoracic and pelvic limbs
what does the cervical intumescences connect too?
The brachial plexus
what does the Lumbar intumescences connect too?
connects to the llumbosacral plexus
what are the three mebranes that cover CNS?
- dura mater
- arachanoid membrane
- pia mater
What is the external layer of meniges?
Dura mater
What is the name of the space surrounding dura matter?
Epidural space
where is the dura matter connected to vertebrae?
At the level of C1-C2 where its is adhered to periosteum of vert
why is the arachanoid matter in close contact with the dura matter?
Due to the pressure of the CSF that occupies the subaracanoid space pushing it outwards
what gives aracanoid its spider like appearance?
lots of fine filaments which blend with pia mater
What does pia matter surround?
spinal cord and roots
Is pia matter thick or thin CT layer?
thin
what is formed from the thickening of the pia mater along the lateral margin of the spinal cord?
denticulate ligaments
Where does the denticulate ligament attach too?
The arachanoid and dura matter laterally
what is the function of the meniges?
- physical support
- encloses CSF circulation
- CSF production
what is the clinical significace of meninges diagnostically?
- CSF collection
- MRI
what diseases can occur within meninges?
- meningitis
- neoplasia
T/F each spinal segament has a dorsal and ventral root on each side?
Trueeeeeee
what do the ventral and dorsal root unite to form?
spinal nerve
Spinal nerve roots have the 3 meniges but what happens at level of spinal nerves?
The dura mater becomes epineurum
At the dorsal root what axons enter and with what?
Afferent axons enter the cord with sensory info
At the ventral root what axons enter and with what?
Efferent axons exit the spinal cord with motor info
what is the spinal cord primarily formed by?
- neurons and their axons
- neuroglia = supporting cells of the cns
what is the central canal filled with?
CSF
How is white matter organised?
- dorsal funiculus - acending sensory
- lateral funiculus - both
- ventral funiculus - decending motor
what spinal nerve at brachail plexus are you testing with flexor withdrawl reflex and what spinal cord segments?
Varies with area stimulated but musculocutaneous, axillary, median, ulnar, radial + C6-T2
what spinal nerve at brachial plexus are you testing with biceps reflex and what spinal cord segments?
musculocutanous + C6-C8
what spinal nerve are you testing with triceps reflex at brachail plexus and what spinal cord segments?
Radial + C7-T1
what spinal nerve at lumbosacral plexus are you testing with flexor withdrawl reflex and what spinal cord segments?
scaitic + L4-S1
what spinal nerve at lumbosacral plexus are you testing with patellar reflex and what spinal cord segments?
femoral nerve + L4-L6
what spinal nerve at lumbosacral plexus are you testing with perineal reflex and what spinal cord segments?
pudendal + S1-Cd5
T/F there is constant interconnection among sensory and motor neurons?
Trueeee
describe a reflex arc?
- receptor collects sensory informaton
- afferent pathway = sensory neurons whihc trnasmit the info from the recepto to the nect neuron at the CNS
- CNS centre = process the info and elaborate an involantary rection
- efferent pathway = motor fibers which trnasmits the reaction
- effector = implements respones (muscles and glands)
In terms of spinal reflexes what is the CNS region?
Spinal cord
In terms of responses what is the CNS region?
forebrain
In terms of cranial reflexes what is the CNS region?
brainstem
are reflexes involuntary or voluntary
involuntary
Describe how you would clinically examine patellar reflex?
- hold patients limb so that stifle is semiflexed
- percussion of paterllar tendon
- the result of thsi reflex is a brisk controlled extension of stifle
Describe how you would clinically examine Pelvic limb withdrawl reflex?
- animal in lateral recombancy
- pinch the digets with fingers to stimulate nociceptors
- the results of this refles is flexion of hip, stifle and tarsus
Describe how you would clinically examine perineal reflex?
- pinch perineum on both sides
- the result of this refles is a contraction of the anus and flexion of the tail
when looking at the perineal reflex what nerves are allocated to tail and anus?
- anus = pudendal
- Tail = caudal
Describe how you would clinically examine Thoracic limb withdrawl reflex?
- lateral recumbancy
- pinch digets with finger to stimulate nocioceptors
- the result of this reflex is the flexion of carpus, elbow and shoulder
Describe how you would clinically examine cutanous trunci reflex?
- pinch skin over dorsum
- the result of this reflex is the bilateral contraction of the cutanous trunci muscle
whats the grading scale for spinal reflexes?
0 - absent
1 - decreased
2 - normal
3 - incresed
4 - clonus - repetitive folowing one single stimulation
what are the 2 motor systems that all motor functions require the interactions between?
LMN and UMN
how does the UMN modulate the LMN?
By inhibition
What connects the CNS with the muscle to be inervated?
LMN
Describe the LMN anatomically?
- cell body at the ventral horn of the spinal grey matter
- its axon leaves the CNS by the ventral nerve root to join a spinal nerve and then synapses with an effector muscle
T/F the LMN is involved in voluntary and involuntary (reflexes) movements and basal muscle tone
Trueeee
what are clinical signs when there is damage to the LMN?
- affection of the voluntary movement = weakness or complete paralysis
- affection of involuntary movement = reflexes reduced or absent
- reduced/ absent basal muscle tone = flaccidity
- denervation of the muscles causing atrophy
T/F the UMN is confined to the CNS?
True
Describe the UMN anatomically?
- its cell body lies within the brain
- its travels through the brain and/or spinal cords white matter and synapses indirectly with an LMN to modulate its activity
what is UMN responsible for?
It is responsible for the initaition and maintenance of normal movements
T/F UMN is involved in initiation and control (by inhibition) of voluntary
movements
Trueee
What are the clinical signs when there is damage to UMN?
- affection of the voluntary movement = weakness or paralysis
- spinal reflexes are intact or increases when LMN is inhibited
- stifness
- atrophy appears very slow and ue to disuse
what is hyperflexia?
A release/ lack of inhibition from UMNs to the LMN which may result in an increase reflex
what is Pseudo-hyper-reflexia?
A reduction in action of antagonistic pair so a lock of aposing forces to the reflex
lesions affecting spinal nerve roots or peripheral nerves are called?
polyradiculopathies or polyneuropathies
what do polyradiculopathies or polyneuropathies induce?
LMN signs in all 4 limbs
what is deep pain perception or nocipeption?
The response to a nocoius stimulus
what does lack of nociception means?
deep pain
why does hypothalamus have the richest blood supply
Due to it being surrounded by circulus arteriosus
What is the cerebral arterial circle?
An elongated arterial rinf on the ventral surface of the brain
What is the cerebral arterial circle formed by?
- Rostral communicating arteries
- These continue as the right and left rostral cerebral arteries
- These continue as the right and left caudal communicating arteries
- circle is then closed bu the basilar artery
what are the 5 pairs of arteries supplying the brain?
Rostral cerebral artery
Middle cerebral artery
Caudal cerebral artery
Rostral cerebellar artery
Caudal cerebellar artery
what arteries arise form the cerebral arterial circle?
Rostral cerebral artery
Middle cerebral artery
Caudal cerebral artery
Rostral cerebellar artery
what artery arises from the basilar artery?
caudal cerebellar artery?
specifically where does the rostral and middle cerebral artery arise from in cerebral arterial circle?
internal carotid artery
specifically where does the caudal cerebral artery arise from in cerebral arterial circle?
The caudal communication artery
specifically where does the rostral cerebellar artery arise from in cerebral arterial circle?
The caudal communicating artery
what are the 4 incoming branches to the cerebral arterial circle?
- internal carotid artery
- basilar artery
- maxillary artery
- vertebral artery
In dogs and horses where is most of the blood supply to brain and arterial circle come from?
Internal artery
In dogs and horses what artery supplies the remianing parts of cortex, medulla and cerabellum?
vertebral artery
T/F In cats and sheep there is no blood coming in from internal carotid artery?
True as it is obliterated after a few weeks to month after birth
Due to channel 1 being absent what is the main supply to cat and sheep brains?
Maxillary artery
only a small bit of the caudal medulla is supplied by what artery in cat and sheep?
vertebral artery
Describe the blood flow to brain in cows?
- main blood supply is maxillary as internal carotid obliterated
- other supply coming from vertebral artery and the segmental spinal arteries
If you compress the axillary artery in cats you will cut off supply to what and what can this cause?
supply to brain and can cause blindness
Describe the ritual slaughter of sheep?
Loss od consciousness withing 2-15secs after both carotid arteries are cut
How long in sheep after the carotid arteries are cut is the corneal reflex lost?
3s
Describe the ritual slaughter in cattle
Time to loose coniousness is more variable than in sheep - a cow will go quicker if calm and a rapid cutting stroke is used
How long does the corneal reflex remain in cow after cut?
15-90s
From the aorta what segmental arteries arise and what part of the spinal cord dpo they supply?
- lumbar arteries supplying the lumbar region
- intercostral ateries supplying thoracic region
- vertebral arteries that are arsie from subclavian artery to supply the cervical spine
From the segmental spinal arteries what two arteries arise?
dorsal and ventral root arteries
From the dorsal and ventral root arteries what arises further up?
The irregular arterial ring which wraps arounf the spinal cord
What is this arterial composed of?
- two dorsolateral spinal arteries
- a single ventral artery
What are the thre vascular zones of the spinal cord and what supplies them?
- inner - supplied by ventral arteries only
- middle - supplied by both vertical and radial arteries
- outer - supplied by the radial arteries
Where specificaly withing these zones does the vertical artery supply?
Supplies most of the grey matter and reach periphrally into the white matter
Where specificaly withing these zones does the radial artery supply?
Supplies the white matter and out region of the grey matter
What is Fibrocartilaginous embolism?
A accute (sudden) onsey of paraparesis ot tetraparesis which is non-painful and regressive
what is Fibrocartilaginous embolism secondary too?
Embolism of spinal cord artery with the intervertebral disc material causing infarction of the rgeion of the sponal cord supplied by that artery
Describe the veins of the CNS?
-They lack tunica media and tunica adventitia
- Lack valves too
Describe the dorsal system of sunuses that aid with venous dranage of the brain
- dosal agital sinus
- straight sinus
- transverse sirus
Describe the ventral system of sunuses that aid with venous dranage of the brain
- cavernous sinus
- dorsl petrosl sinus
- ventral petrosal sinus
what sinus is in the connecting system of the sinuses?
sigmoid sinus
Where does the dorsal sagital sinus line and where does it drain by what?
- Lines the falx cerebri
- Drains dorsal regions of the fore brain via the dorsal cerebral veins
Where does the straight sinus line and where does it drain by what?
- lines the caudal part of the falx cerebri
- drains dorsal regions of the forebrain via draining the great cerebral veins
T/F the trnasverse sinus is a paired
True
When the left and right transeverse sinus join at midleine what does this form?
confluence of the sinuses
What happens at the confluence of the sinuses?
They recieve dorsal sagital sinus and continue laterally and then here divides into temporal and sigmoid sinuses
what does the cavernous sinus surround?
Hypophysis
Describe where cavernous sinus drains from?
From the petrosal sinus which then drains into the ventral region of the brain
Describe the difference in drianage between ventral and dorsal petrosal sinus
- dorsal drains the vebtral region of the brians
- ventral connects cavernous sinus to the sigmoid sinus
T/F the sigmoid sinuas has an S shape
TRueeeeee
Describe what happens at the sigmoid sinus?
- It recieves dorsal system from transverse sinus and ventral system drom the pertrosal sinuses
- Connects directly with the spinal system and draisn into the maxillary vein into the systemic circulation
Describe the venous draniage of teh spinal cord?
ventral spinal vein - vertebral venous sinus - spinal veins
- vertebral veins, azygos ceins, caudal vena cava - systemic circulation
Describe from what segments of spinal cord drains into the vertebral veins, azygos ceins, caudal vena cava
- V- C1- T4
- A - T4-L3
- C - L4-L7
Where does the CSF originate?
From capillaries throughout the CNS
Where is the major production of CSF?
the choroid plexus of lateral, 3rd and 4th ventricle
What are the main function of the CSF?
- Physical support (buoyancy)
- Protection against trauma
- Modulates pressure changes within the skull
- Nutrition (transport of metabolites, nutrients and neurotransmitters)
- Chemical buffer (maintains ionic balance)
What is Hydrocephalus?
- congenital abnormality related to dilation of the ventricular system and abnormal CSF
- frequently with secondary formation of the syrinx (fluid filled cyst) inside spinal cord
What are the three function of neurons in NS?
- sensory input
- integration
- motor output
Define sensation
A physical feeling or perception for something that happens to or comes into contact with body
What is the function of spinal nerve?
A nerve that carries signal between the spinal cord and the body
What is the function of cranial nerve?
A nerve that carries signal between the forebrain or brainstem and mainly the head and neck
Describe the location of exteroreceptors and what are they sensitive to?
Near the surface of the body and sensitive to chnage in external enviro
what are proprioceptors sesnitive too?
To movement of muscle, tendons and joints
Where are interoreceptors located and what are they sensitive too?
They are located within the viscera and are sensitive to change in internal enviro
T/F The sensory portion of the PNS can be classified based on the location of the dendritic zone in the body
true
Where is the dendritic zone of somatic afferent compared to visceral afferent pathway in PNS?
Somatic is on or near the surface of the body whereas in visceral dentritic zone is in the wall of the varous vicera of the body
What can the somatic afferent fibers be subdivided into?
- Genral somatic afferent GSA
- Special somatic afferent SSA
What is the GSA for and what nerves are involed?
- Touch, temp, proprioception and noxious stimulus
- Cranial nerve 5 fro the head and spinal nerves for the rest of the body
What is the SSA and what nerves are involoved?
- For vision cranial nerve 2 and for sound nerve 8 for sound
what can visceral afferent fibers be subdivided into?
- Genral visceral afferent GVA
- Special visceral afferent SVA
What is the GSA and what nerves are assocatied?
- Organ content, distention, chemicals
- Cranial nerves 7,9 and 10 to viscerail structures in heas
- cranial nerve 10 and spinal nerves to the viscera and blood vessels of the rest of the body
what is the SVA and what are the nerves assocaited with it?
- For taste craial nerves 7, 9 and 10
- For olfaction cranial nerve 1
What are the 4 sensory spinal tracts?
- Fasciculus gracilis
- Fasciculus cuneatus
- Dorsal and ventral spinocerebellar tracts
- Spinothalamic tracts
In the fascuculus gracillis tract what infomation is passed and from where?
- proprioceptive information from the pelvic limbs
( rember this as the gracilis muscle in thigh region so hindlimb)
In the fascuculus cuneatus tract what infomation is passed and from where?
- proprioceptive information from thoracic limb
( remember this is as cuneatus meaning wedge shaped like shoulder)
In the Dorsala nd ventral spinocerebellar tract what infomation is passed and from where?
- Information to cerebellum for cooridination
In the Spinothalamic tract what infomation is passed?
- Information to thalamus about pain, itch, touch and temp
Define motor function
Movement involving a muscular component
What is the LMN?
Neurons located in either the ventral horn of the spinal cord or the cranial nerve nuclei of the braistem with motor function
What is the UMN?
Motor neuros that origintae in the motor regeion of the cerebral cortex or the brain stem and carry motor information down to the LMN
T/F The motor portion of the PNS can be classified based on the location of the axon terminals in the body
True
what is the motor portion of the PNS split into?
- Genral somatic efferent GSE
- Genral Visceral efferent GVE
What is the difference of where axon termonals are loacted in the GSE compared to GVE?
In the GSE the axon terminals are in straited muscle throughout the body and in the GVE axon terminals in involuntaru smooth muscle of viscera
what cranial nerves are involoved in the GSE and what supplies the rest of the body?
- All cranial neres apart from 1, 2 and 8
- Vnetral roots and spinal nerves for the rest of the body
what cranial nerves are involoved in the GvE and what supplies the rest of the body?
- cranial nerves 3, 7, 9, 10, and 11
- spinal nerves for the rest of the body
What are the 5 motor spinal tracts?
- corticospinal tracts
- rubrospinal tracts
- reticulospinal tracts
- vestibulospinal tracts
- tectospinal tracts
What information does the corticospinal tracts contain?
Motor information straight from the cerebral cortex
What information does the rubrospinal tracts contain?
Motor information from the red nuclues in the brainstem
What information does the retriculospinal tracts contain?
Motor information from teh reticular formation in the brainstem
What information does the vestibulospinal tracts contain?
Motor information from the vestibular nuclei in the brainstem
What information does the tectospinal tracts contain?
Motor information from the tectal region in the brainstem
How are we going to assess proprioception?
- proprioception placing (knucking response)
- Hopping reaction
- Hemi walking
- wheelbarrowing
- externsor postural thrusting
- hip sway
- visual and tactile placing
how are we going to assess motot function?
- gait analysis
- muscle tone and muscle bulk
- patellar reflex
- withdrawl (flexor) reflex
what is the difference in muscle ton in UMN and LMN?
In a UMN lesion muscle tone should be normal or increased whereas in LMN it will be decreased
what is the difference in spinal reflex in UMN and LMN?
In a UMN lesion the spinal reflexes will be normal or exaggerated where as in LMN they will be dreacresed or absent
what is the difference in muscle atrophy in UMN and LMN?
In a UMN lesion there will be little to late mcucle atrophy and in a LMN lesion mucle atrophy would be early and severe
how do we grade spinal reflexes?
- Normal
- Pain (no neurological deficits)
- Ambulatory paresis
- Non-ambulatory paresis
- Plegia
- Plegia with absent deep pain sensation
T/F the vermis in the cerebellum has hemispheres oneach side of it?
True
what is the function of the cerebellar peduncles?
Axon that connects cerebellum to the brain stem
describe the 3 layers of the grey matter (cerebellar cortex)? (***** insert photo here)
- Molecular cell layer
- purkinje cell layer
- granule cell layer
what can be seen in the purkinje cell layer?
It is a thin layer that has large neurons
What cells do mossy fibers trnasfer excitory input too?
Golgi cells in the granular cell layer
T/F Mossy fibers are less complexed than climbing fibers?
True
where do climbing fibers synapse?
Purkinje cell layer
What is the role of the cerebellum?
To smooth and coordinate motor function for posture and movement
T/F the cerebellar acts as primary initaitor of motor activity?
False - acts as a regulator of motor activity
What doe the cerebellar afferents convey?
- proprioceptive info from limbs, body and head
- Info relevent to the planning and execution of motor activity
where do effernet fibers from the cerebellar cortex come from?
From the Purjinje cells
Are the effent fibers from the purkinje cells inhibitory?
yes
where do most of the efferent fibers from the cerebeller cortex synapse?
in the deep cerebeller nuclei
What bypasses the deep cerebellar nuclie and synapses directly into the vestibular nuclei?
The vestibulocerebellum
T/f the deep cerebellar nuclei neurons are all excitory to nuclei of pyramidal and extrapyramidal systems?
True or silent but never inhibitory
Describe the efferent and afferent pathways at the rostral cerebellar peduncle?
- The afferent is from the ventral spino- cerebellar
- The efferent is to the thalamus and the midbrain
Describe the efferent and afferent pathways at the middle cerebellar peduncle?
- The afferent is from Cortico-ponto-cerebellar pathway
- There is NO efferent
Describe the efferent and afferent pathways at the caudal cerebellar peduncle?
- The afferent is from the dorsal spino-cerebellar, parts of brain stem (reticular formation, olicary nucleus), cuneo-cerebellar and vestibular nuclei
T/F most info comes in via caudal and middle peduncles and most our through rostral peduncle?
True
what are the 3 functional subdivision of the cerebellum?
- Vestibulocerebellum
- spinocerebellum
- cerebrocerebellum
T/F the cerebellum plays a role in the menace response?
True
when you have neurolalisation of the cerebellum, what would you see on neuro examination?
mentation
gait
crainail nerves
proprioception
spinal reflexes
mentation - normal
gait - hypermetria , intention tremors, wide based stance
crainail nerves - bilateral absent menence response
proprioception - hypometric hopping otherwise norm
spinal reflexes, muscle mass and tone - normal and no pain on spinal palpation
when you have neurolalisation of the right cerebellum, what would you see on neuro examination?
mentation
gait
crainail nerves
proprioception
spinal reflexes
mentation - normal
gait - ataxia, unable to walk
crainail nerves - absent menence response on the right and head tilt to the left
proprioception - reduce on the right thoracic and pelvic limb
spinal reflexes - normal and no pain on spinal palpation
what are the three main function of the brainstem?
- Conduction
- cranial nerve functions as nerves 3-12 emerge from here lol
- integrative functions as involved in cardio, resp control, alertness, awareness and consciousness
where is the cardiovascular centre found in brainstem?
medulla oblongata
what is the cardio control role at brainstem?
- regulation of heart rate
- change of blood ph and CO2
- chnage in blood pressure
How does the cardio centre in brainstem act when detects changes?
Acts by sendignnerve impulse to pacemaker via autonomic fibers
Where are the resp centres found in the brainstem?
Medulla oblongata and pons
What is controlled here at the rsp centre in brainstem?
Controls the rate and depth of resp movements
Describe the Cheyne-stokes resp pattern
volume starts shallow and gets deeper then gest shalow again followed by no resp before another one
Describe the Biots resp pattern
clusters of rapid resp of nearly equal depth solloed by regular no resp (apnea)
Describe the Apneustic resp pattern
Long breath in and long breath out so not UDUDUD liek UUUUUpauseDDDD UUUUUpause DDDD
Describe the Ataxia resp pattern
completely irregular - fucked like me for all exams LOL
what is the acending reticular activating system responisble for?
Awak state, level of conscoiusness and sleep
How us the ARAS formed?
collection of neuronal cell bodies that form a ill-defined meshwork in the central core of the brainstem
How do you grade mental status?
- occasional periods of alertness and responsive to enviro
- depression or delierium, reponds but response may be inappropriate
- semicomatose, responsive to visual stimuli
- semicomitose, response to auditory stimuli
- stupor, response only to noxoius stimuli
- coma, unresponsive even to noxious stimuli
when you have neurolalisation of the left brainstem, what would you see on neuro examination?
mentation
gait
crainail nerves
proprioception
spinal reflexes
mentation - obtunded
gait - ataxia, unable to walk
crainail nerves - head tilt to the left, positional abnormal alingment of left eye, vertical nystagmus, reduce facial senstaion on the left side and toungue hypotonia ( low tone)
proprioception - deficets on the left thoracic and pelvic limb
spinal reflexes - normal and no pain on spine palpation
A + B - C - D
Describe what would happen to D is A is stimulated
If A is stimulated it would stimulate B. B inhibits C so D would actually be stimulated as C is not inibiting it
What effect do excitatory neurotrasmitters have on RMP?
Raises RMP so depolarises and increases firing probability
What effect do inhibitory neurotrasmitters have on RMP?
Lowers RMP so hyperpolarise, decreasing firing probability
T/F there is some overlap between senses and stimuli?
True - pain with temp, wyw with pressure applied
What does the stimulus intensity relate too?
The increase in depolarisation
What do sensory feilds cover?
a defined area like skin
Overlap of these sensory felids do what?
- can assist with location of the stimuli
- recognistion of the pattern of stimuli
Describe the organation of feild response good for sensitivity
Primary afferents merge on a single seconday afferent
Describe the organation of feild response good for localistaion
Primaru afferent assocaited with severay secondary afferents
What does lateral inhibition aid with?
sharpening stimuli signal so can imporve localistaion and pattern recognistion
What is a dermatome?
A map of animal to show areas of skin all connected to same dorsal root
What is kinthesia?
Awareneass of position and movement of all body parts
Where would you find freen nerve endings mainly?
in hairy skin
where would encapsulated recepto terminals found?
hairless skin
what kind of receptors mostly have encapsulater terminals?
mechanoreceptors
what are the fibre endings like in thermal receptors?
Free nerve endings and non-ecapsulated
Why does tehre need to be two sensors to differentaite temp?
Same impulse frequency at 15 and 40 degrees
T/F at extreme temps pain receptors will be stimulates?
Truee
what happens to the response if there is continous stimulation?
Response declines over time
What does sensory adaptions prevent?
Information overload
what are the 2 exception of sensory adaption?
- pain does not adapt
- some postural senses do no adapt
What is the most commen cause of adaption in pacinian corpuscle?
Due to an inactivation of ion channals
Describe the pacinian corpuscle adaption?
force mediated through pressure starts to be fluid redistribution to ease pressure and give adaption
T/F there are 4 types of sensory afferent fibers?
Trueee
Where can the sensory inputs be mapped too in cortex?
regions called homunculus
what are the two sytems in the centrally-projecting tracts?
- media leminiscal systems
- extalemniscal is a ventro-lateral system
compare the dorsal colums and vetrolateral sytesms
- dorsal columns are new systems connecting to recent areas of the brain wherease ventrolateral systems are old systems like pain
- doesal columns are accurate and precise whereas ventrolateral system is diffuse and less precise
- dosal columns are fast wheras ventrolateral system are slow
what are the two types of muscle receptors?
- muscle spindles
- golgi tendon organs
Descibe the two receptors in oraientation with muscle fibers?
- Muscle spindles are in parallel with muscle fibers
- golgi tendon organs are in series with muscle fibers
what are irdinary muscle fibers called and what innervates them?
- extrasfusal fibers
- innervated by alpha motor neurons
what are muscle spindle fibers called and what innervates them?
- intrafusal fibers
- gamma motor neurons
why is it important not to have adaptions in the muscle spindle?
As they are important for postural reflexesw
What are the sensory fibers involved in muscle spindle?
- Type Ia fibers
- Type II fibers
T/F type Ia fibers are non adaptive and type II are adaptive
False - other way
what effect does activation og the gamma neurons have on muscle spindle?
Contracts the muscle which leads to stretch of the intrafusal fibers and firing of sensory afferent
During the stretch reflex what does the muscle stretching induce?
Stretch spindle which activates sensory afferent and activated aplah motor neuron
What type of fibre does golgi tendon organ gives rise too?
type 1b sensory fibre
what does the golgi tendon orgna innervate?
CNS
What effect does the golgi tendon organ have on muscle?
It induces relaxion of the muscle and prevents damage too it
T/F both the golgi tendon and the muscle spindle project in the same way to the CNS?
true
where does the GTO and the muscle spindle enter and synapse?
Enter at T1-L3 and synapse at clarkes column nuclei
