NEU 2 Flashcards
Explain what temporal summation of postsynaptic potentials are
Temporal summation is where one presyanptic neuron releases several vesicles containing NTs over a short period of time (strong stimulus, more frequent action potentials over short period of time)
Explain what spatial summation of postsynaptic potentials are
Spatial summation is where 2 or more presynaptic neurons release one or few pools of vesicles containing NTs over a short period of time
Describe the fine structure of peripheral nerves
- Includes cranial nerves, spinal nerves and ganglia
- A nerve is composed of several bundles of nerve axons (nerve fibres)
- Held together by connective tissue
- Most nerves are mixed (contain both sensory and motor fibres)
Explain the term aetiology in the development of disease
The cause of the disease or condition (bacteria, genetic mutation etc)
Explain the term pathogenesis in the development of disease
The mecahnism and or development of disease (HOW it causes disease)
Describe some of the changes that can occur in nervous system disease
- Chromatolysis after axonal damage or toxicity - swollen, loss of Nissl substance, pale, nucleus pushed to periphery, lose bluish stain
- Hypereosinophilic: shrunken neurons, increased number of eosinophils
- Swollen neurons due to lysosomal storage diseases
- Viral inclusion bodies: appear as pinkish dots in cytoplasm of neurons
- Cytoplasmic neuronal vacuolation: space in nerve cell body
List possible different causes of disease of the nervous system
- Trauma
- Congenital (hypomyelination)
- Hypertension (cerebral oedema)
- Cytotoxic oedema (intracellular fluid, systemic intoxication)
- Inflammation
- Degeneration
- Neoplasia
Describe the difference between encephalitis, meningitis, myelitis
Encephalitis: inflammation of the brain
Meningitis: inflammation of the meninges
Myelitis: inflammation of the spinal cord
What does each of the letters in DAMNITV mean
D: degenerative A: anomalous M: metabolic N: neoplastic nutritional I: inflammatory (infectious or immune mediated), idiopathic T: toxic, trauma V: vascular
Describe the methods of production and drainage of CSF
- Produced in choroid plexus, present in all ventricles
- Ultrafiltration of blood
- Drained by arachnoid villi within sagittal sinus into lymph
- Production and drainage are independent so production will continue even if drainage is not occuring effectively
Describe the flow of CSF through the ventricular system
- Drains into subarachnoid space around the brain
- Produced in all ventricles and flows through all
- Lateral -> IIIrd -> IVth -> subarachnoid space
- Aided by pulsing of choroid plexus
- Some goes around brain, some around spinal cord and then dispersed into peripheries of body
- Also absorbed into venous circulation and lymphatic vessles
- Also into venous sinuses of dura mater
Compare ventriculomegaly and hydrocephalus
Ventriculomegaly: increased ventricle size
Hydrocephaly: the build up of fluid in the brain (can lead to ventriculomegaly)
Explain the 3 vector model of behaviour
- There is an input, processing and an output
- A change in input vector will alter the output vector (e.g. suddenly going blind)
Describe what is meant by an input vector in the 3 vector model of behaviour and give examples
- Sign stimulus or releaser
- Certain stimuli can induce/release a relatively invariable motor response or invariable complex motor behaviour
- Visual cues, chemical cues, sounds
- Usually small parts of the environment
Explain the concept of the ethogram
- Complete inventory of behaviour displayed by a species in a particular environment
- Behaviour is described without explicit intial reference to its purpose
- Described objectively
- Just describes, does not look for a reason why
What are Tinbergen’s 4 levels of behavioural explanation
- Function: what is the behaviour for
- Evolution: where does behaviour come from
- Mechanism: how is he behaviour acheived
- Development: how does the behaviour develop in ontogeny
Describe what is meant by a status vector in the 3 vector model of behaviour and give examples
- The processing of the input vector
- Can be altered by brain tumours
- Motivation, emotion and memory are status variables and affect the way the information is stored and procesed
Describe what is meant by an output vector in the 3 vector model of behaviour and give examples
- The elements of behaviour that are generated by an animal and are accessible through observation
- Birdsong, locomotor behaviour, resting, grooming tc
- Specific to a given species
Describe the clinical neurological signs caused by Toxoplasma in cats
- Does not usually cuase disease in cats
- Often chronically infected with no clinical symptoms
- However in kittens: fading kitten syndrome, weakness, partial or total paralysis
- Clinical symptoms in cats: paralysis, uncoordinated gait, weakness, seizures, progressive rigidity in one or more limbs as a result of myositis and neuritis
Describe the clinical neurological signs caused by Encephalitozoon in rabbits
- Often subclinical
- May see: hindlimb paralysis, urinary incontinence, renal failure, head tilt, paralysis, death
Explain why some individual cats (or certain breeds) are susceptible to Toxoplasmosis
- More often in kittens and cats with a weakened immune system
- Increased susceptibiltiy whenever immunocompromised e.g. FIV, FeLV, FHV
Make observations regarding the epidemiology of Encephalitozoon in UK rabbits
- Often ingested - contaminated food or water
- More common in domesticated rabbits (none seen so far in wild populations)
- Almost half of all domestic rabbits have been exposed
- May be due to contaminating own food and water
Explain the importance of the mammalian immune system in Toxoplasmosis and Encephalitozoonosis
- More likely to have clinical infection when immunocompromised
- The immune response may be what is causing the damage rather than the parasite itself (particularly with Encephalitozoon)
Describe the positioning to obtain a radiography image of the spine
- 2 orthogonal views (right angles to each other)
- Anaesthesia
- Avoid parallax errors - twisting etc
- VD better than DV (area of interest nearer to plate)
- Use foam wedges to ensure spine is straight
- Flexed neck views useful in cases of suspeted instability
Describe what is meant by myelography and explain why it is useful
- Contrast opacification of sub-arachnoid space
- Introduced at the occipital-atlantal junction or caudal lumber region (between L5 and L6)
- Should see 2 contrast columns
- Deviation suggests damage to the spinal cord
What may be seen on a myelograph
- Normal: 2 straight parallel lines
- Extradural lesion: lower line being pushed upwards
- Intradural: lower line being pushed down by lesion between lines
- Intramedullary: both lines distorted due to lesion within lumen of cord
What are FLAIR and STIR MRIs?
FLAIR: supresses CSF, useful for lesions adjacent to ventricular structures
- STIR: supresses fat signal
Why is pain scoring needed?
- Assessing whether analgesics should be used
- Particularly useful in stoical animals such as cats or prey animals as are less likely to be treated with analgesics when they should be
Describe te general architecture of the vascular system of the spinal cord and brain
- 5 main pairs of vessels
- Rostral cerebral arteries, middle cerebral arteries, caudal cerebral arteries, rostral cerebellar arteries, caudal cerebellar arteries
- Originate from ventral spinal cord from circle of Willis
- Blood can go in different directions around the circle (no set direction)
- Sits below the brain
- Circle supplies by the basical artery and internal carotid arteries
What do the rostral cerebral arteries supply?
Medial aspect of the cerebral hemispheres
What do the middle cerebral arteries supply?
The lateral and ventrolateral aspects of the cerebral hemispheres
What do the caudal cerebral arteries supply?
The occipital lobes
What do the rostral cerebellar arteries supply?
Rostral aspects of the cerebellum
What do the caudal cerebellar arteries supply?
The caudal and lateral aspects of the cerebellum
How is the basilar artery supplied?
- At each intervertebral formamina, vertebral artery supplies the ventral spinal artery (basilar artery)
- Vertebral artery is a branch of teh subclavian artery running through the vertebral foramina of C1-C6 and is lateral to the vertebral bodies and reasonably large
What are the 3 groups of sinuses in the brain?
- Dorsal
- Ventral
- Connecting
Describe the pathway of the dorsal sinuses.
- Dorsal sagittal, straight and the transverse sinus
- Dorsal sagittal starts in the bone, runs into the falx
- Transverse sinuses run down within the skull
- Straight sinus drains the great cerebral vein
- The transverse sinuses drain the dorsal sagittal sinus
Describe the ventral sinuses
- Dorsal and ventral petrosal sinuses
- Run rostral to caudal and connect caudally with the transverse sinus
- the cavernous sinus is a fine network of veins and connects pairs of sinuses
Describe the connecting sinuses
- Join things up between the cerebral and spinal sinuses and dorsal and ventral
- Extracranial connection to the maxillary vein
- Connection to ventral venous sinuses
Describe the arterial supply to the spinal cord
- Segmental arteries at every iintervertebral foramina
- Cervical: vertebral artery
- Thoracic: intercostal arteries
- Lumbar: aorta
Describe the structure and physiological role of the blood brain barrier.
- Isolates circulating blood from parenchyma of the brain
- Made up of capillaries surrounded by closed overlapping endothelium, dense basement membrane, processes of astrocytes
- Is a selective barrier for exchange substances (blocks large molecules)
- Mainly active transport across unless lipid soluble
Explain the clinical significance of the blood brain barrier
- Is the separation between the blood and the brain
- Large macromolecules and non-lipid soluble drugs will be excluded from the brain
- Cannot assume that a drug will reach a useful concentration in the brain
- Drugs may become less useful as the blood brain barrier heals due to the action of the drug so higher concentrations may be needed
Describe the structure of the meninges and the spaces between them
- 3 layers
- Goind outside in: dura mater, arachnoid mater, pia mater
- Space between dura mater and arachnoid = subdural space
- Space between arachnoid and pia = subarachnoid space
- Spaces contain CSF
- Are continuous around the brain and spinal cord
- Extend along dorsal and ventral nerve roots into the intervertebral foraminae
What is the function of CSF?
Protection of the brain, support (bouyancy), nutrition
Describe the structure of the dura mater
- Intercranially adherent to the periosteum of the skull
- Spinal: separated from the periosteum by the eidural space which is filled with fat
- Tough layer composed mainly of dense connective tissue
Describe the structure of the pia mater
- Fibres blend with arachnoid mater
- Thin layer which is adherent to underlying brain/spinal cord
Describe the structure of the arachnoid mater
Fine layer pressed up against the dura mater with fine whispy filaments which extend to and blend with pia mater
What are the functions of the meninges?
- Protection
- Containment of CSF
- Maintenance of BBB
- Support
Explain how the meninges provide support to the spinal cord
- Spinal cord is suspended within meninges by denticulate ligaments within dura mater
- Some movement is possible
- Denticulate ligaments have focal fimr atachment between the pia-arachnoid and dura mater
Define the common types of infectious neuronal disease and the types of microorganisms that cause them
Neurotropic: directly infects nervous tissue, spreads cell to cell
Neural abscess: has to be next to nervous tissue, septic focus is site where infection enters nervous tissue
- Haematogeonus: spreads through blood
Can be caused by viruses, bacteria, fungi and prions
Describe indicators of neurological infection
Depression, pyrexia, cervical pain, hyperaesthesia, photophobia, generalised rigidity, seizures, paralysis (local and general), ataxia, papilloedema, possible ophthalmic inflammation, systemic signs (septic shock and brachycardia)
Outline the routes and processes of CNS infection
- Trojan horse invasion
- Transcellular invasion
- Paracellular invasion
Discuss microbial toxins in neurological disease
- Can be ingested or produced during infection
- For toxin to be ingested pathogen does not need to be alive
- Rye grass staggers and algae are examples where thee toxin alone can be ingested
- Tetanus and Botulism are examples of toxins produced by bacteria
Describe the transcellular method of crossing the blood brain barrier
- Pathogen binds to host cell and invades through cell
- Endocytosis
- Can be passive or acivated by pathogen
- Staphylococci, Listeria, Cryptococcus
Describe the paracellular method of crossing the blood brain barrier
- Elicits some form of response that breaks down tight junctions or vascularisation
- Increased pinocytic activity leading to trans-endothelial channel formation or tight junction function being broken down
- Can occur as a result of inflammatory (cytokines, free radical) or microbial factors (adhesion molecules, microbial proteins etc)
- Nipah virus, Lyme disease
Describe the Trojan horse method of crossing the blood brain barrier
- Pathogens already in cell (macrophage)
- Cell can enter as a natural process and pathogen enters with cell
- No antibody interaction
- Requires primary infection, will spread where cell goes, may be refractive to antibdy once established
Describe virulence factors that are used by viruses to cross the blood brain barrier
- Key structural proteins (attachment processes, enzymes to modify host components)
- enveloped proteins (virus has to attach and invade cells)
Describe virulence factors that are used by bacteria to cross the blood brain barrier
- Common surface proteins (Fimbriae) or outer membrane proteins
- Some bacteria have specific invasion mechanisms
- Intracellular survival mechanisms
- Facilitate passage across Gram -ve membranes
Describe the monosynaptic reflex.
- Allows for rapid responses to changes in muscle position
- Most muscles are antagonistic
- Reciprocal inhibition of flexors and extensors of the same joint
Compare monosynaptic and polysynaptic relfex arcs
- Monosynaptic controls one area at a time (flexors and tensors of the same joint)
- Polysynaptic is slow and maintains posture
- Slow fibres allow for subtle control of intrafusal muscle fibre length and tension
Describe the structure and function of the muscle spindle
- Nuclear bag fibres or nuclear chain fibres
- Nuclear bag have nuclei in one place
- Number of different innervations
- 2 types of sensory: 1a (fast) and 2 (slow
- Slow motor fibres
- 1a associated with monosynaptic connections and reflexes
- Slow connected with polysynaptic
- Slow originate from flower spray endings, fast from annular spiral
- Slow give static info, fase give dynamic info
Describe the function of the golgi tendon organ
- Within tendon, series of nerve fibres wrap around and interact with collagen fibres of tendon
- Way to measure tension within tendon
- Act as strain gauge
- Produce reverse myotatic relfexes
- Clasp knife reflex: overload of tension results in release
Describe Schiff Sherrington syndrome
- Inhibitory interneurons located on dorsolateral border of ventral grey column L1-L7
- Ascend contralaterally to cervical intumescence
- If cord severed, hindlimbs paralysed and rigid forelimb extension
- Only when lying on its side, overridden when walking
Describe the monosynaptic reflex in association with myotatic reflexes
- Tendon reflexes
- Myotatic relfexes are monosynaptic
Define proprioception
Positional awareness
Compare the projections in conscious and unconscious proprioception
Projection into cerebellum = unconscious. 2 neurones required
Projection into somesthetic cortex = conscious. 3 neurones required
Describe conscious proprioception
- Cuneate (forelimbs)/gracile (hindlimbs and trunk) tracts
- Run with dorsal funiculus of the spinal cord
- Projects into spinal cord, along cord until caudal medulla, then first synapse
- Synapses into gracile or cuneate, then derfurcates up to thalamus into sensory cortex
- 3 neurons, crosses over midline and projects into contralateral side of the brain
Describe unconscious proprioception
- Spinocerebellar tracts
- Hindlimbs and trunk travel by dorsal and ventral SCT
- Forelimbs travel via spinocerebellar pathway and cranial SCT
- Lateral funiculus
- Difference is that information synapses when enters cord and then again when in cerebellum
Outline the concept proprioception
- Is multimodal - receptors and pathways
- Conscious and unconscious
- Conscious runs in dorsal funiculus, unconscious in lateral funiculus
- Fast fibres (larger) so easier to damage
Explain the concept of a nerve plexus
- Formed as a result of contributions to limb by several somites (body units)
- Each somite associated with one spinal nerve, several spinal nerves to each limb
- Individual muscles in limb formed by contributions from several somites
- Each muscle supplied by several spinal nerves
- Muscles supplied by nerves leaving the limb plexuses
- Individual spinal nerves need to regroup to be able to innervate the muscle together
Describe the differences between a plexus and a spinal nerve
- A plexus is a collection of somites associated with nerves
- A spinal nerve is a collection of nerve fibres that leave the spine to innervate muscles in the limb and trunk
Give the roots, muscles supplied and cutaneous area supplied by the suprascapular nerve
- C6, 7
- Supraspinatus, infraspinatus
- No cutaneous supply
Give the roots, muscles supplied and cutaneous area supplied by the subscapular nerve
- C6, 7
- Subscapularis
- No cutaneous supply
Give the roots, muscles supplied and cutaneous area supplied by the musculocutaneous nerve
- C7, 8
- Flexors of elbow joint
- Medial surface of forearm (and manus in horse)
Give the roots, muscles and cutaneous area supplied by the median nerve
- C8, T1
- Flexors of carpus and digits
- Palmar surface of manus (and dorsum digit in horse)
Give the roots, muscles and cutaneous area supplied by the ulnar nerve
- C8, T1, 2
- Flexors of carpus and digits
- Caudal surface of forearm and lateral surface manus (dorsum digit in horses)
Give the roots, muscles and cutaneous area supplied by the radial nerve
- C7, 8, T1
- Extensors of elbow, carpus and digits
- Craniolateral surface of forearm and dorsum manus (except digit in horse)
Give the roots, muscles and cutaneous area supplied by the axillary nerve
- C7, 8
- Flexors of elbow
- Lateral surface of arm
Describe what is meant by biological rhythms
- A rhythm is a function which oscillates or cycles at a regular frequency
- Biological rhythms are measurable activities generated by some internal oscillator
Give examples of rhythms and explain each.
- Circadian: a daily rhythmical change in behaviour or in a physiological process. Roughly a 24 hour cycle
- Infradian: rhythms with periods longer than the period of a circadian rhyth i.e. with a frequency less than one cycle in 28 hours e.g. reproductive cycles
- Ultradian: rhythms with periods shorter than the period of a circadian rhythm e.g. REM cycle in sleep
- Seasonal (type of infradian) e.g. polyoestrus, seasonal polyoestrus (long day/short day), monoestrus
Describe the function of rhythms
- Synchronisation of the body with the environment
- Maintenance of internal temporal endogenous processes within the body
What are Zeitgeber and give examples
- Any external lcue that entrains the internal time keeping system of organisms
- Strongest is light
- Others include temperature, social interactions, pharmacological manipulation and eating/drinking patterns
- Zeitgeber -> entrainment -> endogenous rhythm
Give the positions of biological clocks
- Retina
- Suprachiasmatic nucleus
- Pineal gland
Describe the retina as a biological clock
- Photopigment present in ganglion cells in retina whose axons transmit information to the SCN, thalamus and olivary pretectal nucleus
- Rods and cones not required
- Melanopsin containing ganglion cells in teh retina
- Melanopsin required to transform light into a nerve impulse
Describe the suprachiasmatic nucleus as a biological clock
- Is part of retinohypthalamic pathway
- Nucleus sitauted atop optic chiasm
- Is the position of the circadian clock
- Retina -> retinohypothalamic pathway -> SCN (in hypothalamus)
Describe the pineal gland as a biological clock
- In diencephalon
- Attached to dorsal tectum and produces melatonin and plays role in circadian and seasonal rhythms
- Located immediately behind the thalamus
- Melatonin is an amino acid derivative from tryptophan
- Responds to light - more melatonin when dark, less when light
- Melatonin induces sleep
- Represses reproduction in long day breeders
- Stimulates reproduction in short day breeders
Explain how biological clocks work
- Process: light enters the eye -> info from retiina to SCN -> SCN sends signal to pineal gland -> meltonin secretion altered
- Primary pacemaker of SCN is entrained to solar time by retinal afferents
- Maintains and synchronises tissue-based clocks in major organ systems by endocrine, autonomic and behavioural cues
- Linked to structures across the body, not just the brain
Describe the function of peripheral clocks and how they work
- Circadian clocks exist in CNS and peripheral tissues
- SCN is master clock (light from retina)
- Peripheral clocks of many organs present, can be entrained by signals from SCN as well as otehr signals such as nutrient availability
Explain what chronopharmacology is and outline its veterinary relevance
- Targeting the clock to treat metabolic diseases
- Reduce toxicity of anti-cancer drugs
- Circadian changes in blood pressure (high bp in early morning becuase high levels of hormones in morning)
- Veterinary relevance:
little except husbandry, welfare, reproduction, depression as a disease of circadian clocks
Describe the location of the lumbosacral plexus and give the nerves forming it
- In and around sublumbar muscles ventral to the lumbar vertebrae
- Ventral rami of L4-S2
Give the roots, muscles and cutaneous area supplied by the femoral nerve (and saphenous) nerves
- Roots: L4-6
- Muscles (femoral): quadriceps femoris
- Muscles (saphenous): sartorius
- Cutaneous supply (femoral): none
- Cutaneous supply (saphenous): medial surface of leg to metatarsus
Give the roots, muscles and cutaneous area supplied by the obturator nerve
- Roots: L4-6
- Muscles: adductor group (OOGAP)
- Cutaneous supply: none
Give the roots, muscles and cutaneous area supplied by the cranial and caudal gluteal nerves
- Roots: L6-S2
- Muscles: guteal muscles
- Cutaneous supply: none
Give the roots, muscles and cutaneous area supplied by the caudal cutaneous femoral nerve
- Roots: S1 -2
- Muscles: none
- Cutaneous supply: caudal aspect of thigh
Give the roots, muscles and cutaneous area supplied by the sciatic nerve (including tibial and common peroneal branches)
- Roots: L6-S2
- Muscles (sciatic): hamstring muscle group, biceps femoris, semitendinosus, semimembranosus
- Muscles (tibial): extensors of hock and flexors of digits
- Muscles (common peroneal): flexors of hock and extensors of digits
- Cutaneous supply (sciactic): none
- Cutaneous supply (tibial): caudomedial aspect of leg, plantar foot (dorsum of digit in horses)
- Cutaneous supply (common peroneal): craniolateral aspect of leg, dorsum of foot (except digit in horses)
Discuss basic neural and neurochemical mechanisms of anxiety-related behaviour
- Stimulation of SNS
- Release of noradrenaline and adrenaline
- Cortisol released due to action of SNS (stress hormone)
- Hypothalamus - pituitary - adrenal axis (HPA axis) has been activated in a stressful situation
Describe the endocrine processes involved in anxiety
- HPA (hypothalamus pituitary adrenal) axis activated in a stressful situation(BY SNS)
- Hypothalamus releases corticotropin-releasing hormone (CRH), carried to anterior pituitary gland via portal system, stimulates ACTH release
- ACTH enters blood stream, acts on adrenal cortex to release glucocorticoids
Describe the brain structures involved in anxiety and explain how they are involved
- Amygdala: almond shaped groups of neurons deepp within medial temporal lobes next to lateral ventricles
- Central nucleus is most important part - sends information to the rest of the body
- Sensory input and input from hypothalamus
- Output to hypothalamis, midbrain, pons and medulla
Explain how pharmacology can be used to treat anxiety
- e.g. Benzodiazepines
- Can also induce sedation
- Bind to receptors in amygdala
- Make it easier for Cl- ions to pass through membrane, change membran potential - hyperpolarised, more difficult to generate action potential
- i.e. Benzodiazepines make amygdala less responsive to stimuli
Explain how the brain, periphery and physiological reactions interact in anxiety
- Make a circle
- All affect each other
- Perception of fear leads to physiological response, which are also affected by feelings of fear, however this also works in reverse
