NEU Flashcards
Define:
Ataxia?
Proprioception?
Ataxia= A loss of control of bodily movements Proprioception= perception or awareness of the position and movement of the body
See spinal imaging analysis sheet
Example of spinal imaging
Main components of an intervertebral disc?
Centre: Nucleus pulposus
Around the outside: Fibrous ring
LABEL vertebra: Cranial articular facet? Dorsal spinous process? Caudal articular facet Intervertebral foramen? Nerve root outflow Transverse process? Part removed during facetectomy?
SEE image 1
SEE image 2
Labelled diagram of vertebral column?
SEE image 3
SEE image 4
Schematic of NS?
SEE image 5
Difference between somatic and autonomic NS?
Somatic NS= under voluntary control (cell bodies within CNS)
Autonomic NS= NOT under voluntary control
Components of CNS?
Brain
Spinal cord
Components of PNS?
Cranial nerves
Spinal nerves
Trunks of autonomous nerves
Enteric nervous system
(NOTE: PNS= projections out from CNS, everything that attached onto CNS)
Diagram of CNS and PNS positions?
SEE image 6
Components of nerve tissue?
Nerve cells (neurones) Supporting cells (glia cells/neuroglia)
NOTE: nerve cells produce network of interconnecting fibres which conduct within NS
BRAIN:
Grey and white matter?
GREY MATTER (around periphery, cell bodies):
- Perikarya of neurons (either superficial -> cortex OR embedded in white matter -> nuclei)
- Glial cells (produce myelin in white matter)
- Neuropil (felt of axonic, dendritic and glial processes)
WHITE MATTER (in centre, axons):
- Many myelinated processes
- Glia cells (produce myelin in white matter)
NOTE: perikaryon= neuron cell body
NOTE: glial cells have many processes and may line other structures e.g. blood vessels- SEE IMAGE 10
SEE IMAGE 7
SEE IMAGE 8
SEE IMAGE 9
SPINAL CORD:
Grey and white matter?
GREY MATTER (butterfly-shaped centre)
WHITE MATTER (on outside)
PNS
What are cranial nerves?
12 pairs of nerves Originate from brain, exit from brainstem
Cranium has got in the way of their segmentation
Label: front to back
Arranged in phylogenetic order: e.g. olfaction= c.n.I- reflects evolution of CNS (Olfactory nerve is at front of brain as sense of smell is first useful sense for unicellular organism THEN optic nerve to allow vision (first few nerves are in phylogenetic order) THEN movement of jaw THEN gill flap movement etc.)
SEE IMAGE 12
3 groups of cranial nerves:
- Purely sensory
- Purely motor
- Mixed
PNS
What are spinal nerves?
Nerves emerging from spinal cord
Come out between vertebrae through foramina
Connect CNS and rest of body
Explain fore/hind limb plexus?
Ventral branches of spinal nerves form plexus- innervation of limbs
Forelimb: brachial plexus
Hindlimb: lumbosacral plexus
NOTE:
Radial nerve is made up of components from C7 C8 and T1- mix of nerves which come out of brachial plexus to make up components of the major nerves
SEE IMAGE 13
PNS
Where are perikarya located?
In ganglia (groups of perikarya outside the CNS, inside PNS) In CNS (voluntary control) (in nuclei of cranial nerves or in ventral and lateral horn of the spinal cord)
SEE IMAGE 14
What are ganglia?
> Group of perikarya OUTSIDE of CNS, INSIDE of PNS > Can be site for: - Synapses (GVE - autonomic NS) - Cell bodies (general afferent) - General swapping of nerve fibres
NOTE: Exception= part of Vth cr.n. which has some of its sensory cell bodies in a nucleus rather than a PNS ganglion
OR
> Cyst filled with synovial fluid
SEE IMAGE 15
COMPLETE
27 and 28
Difference between cranial and spinal nerves?
Cranial:
Mostly with specialised functions
(Optic nerve- has only sensory fibres, hypoglossal nerve- only motor)
Spinal:
Mostly mixed fibres (motor AND sensory fibres)
2 parts of autonomous NS?
Complementary systems
1.) Sympathetic NS:
> THORACOLUMBAR= First neuron located in thoracolumbar spinal cord
> Sympathetic ganglia are either paravertebral (sympathetic chain) or prevertebral (celiac ganglion, cran. & caud. mesenteric ganglia, medulla of adrenal glands)
> Functions:
- Vasoconstriction= diverts blood away from GI tract/skin
- Increase blood flow to skeletal muscle
- Bronchiole dilation in lungs= greater oxygen exchange
- Increase HR/cardiac muscle contractility= mechanism for increase blood flow to skeletal muscles
- Pupil dilation/lens relaxation= more light enters eye
2.) Parasympathetic NS:
> CRANIO-SACRAL=
First neuron located in brainstem OR sacral spinal cord
> Nearer effector organ- tends to have ganglia at effector organs
> Functions:
- Blood vessel dilation leading to GI tract= increase bloodflow for digestion as (metabolic demands placed on body by gut) AND accelerates peristalsis
- Constricts bronchiolar diameter when oxygen demand decreases
- Constricts pupil/lens
- Genital erection
Functions of the NS?
1.) Uptake of information=
> From OUTSIDE:
- eyes/nose etc.
> From INSIDE:
- Proprioception (receptors in muscles/tendons)
- Enteroception (intestines etc.)
2.) Transport of information=
> Afferent fibres (periphery -> CNS)
> Efferent fibres (CNS -> periphery)
(NOTE: many different pathways within CNS)
3.) Processing of information
> Simple: reflex
> Most processing is more complex: behaviour
> Storage of info.: memory
NOTE: somatic= go to muscles, visceral= go to visceral (the gut)
Where are perikarya found?
Grey matter
Within ganglia
Functions of the NS?
1.) Uptake of information=
> From OUTSIDE:
- eyes/nose etc.
> From INSIDE:
- Proprioception (receptors in muscles/tendons)
- Enteroception (intestines etc.)
2.) Transport of information=
> Afferent fibres (periphery -> CNS)
> Efferent fibres (CNS -> periphery)
(NOTE: many different pathways within CNS)
3.) Processing of information
> Simple: reflex
> Most processing is more complex: behaviour
> Storage of info.: memory
NOTE: somatic= go to muscles, visceral= go to visceral (the gut)
NOTE: Cranial nerves may have 1/2/3 divisions of information whereas peripheral nerves may have 5/6/7
Structural divisions of the NS?
- PNS
Cranial nerves, spinal nerves - CNS
Brain, spinal cord
SEE IMAGE 16 - ENS
Controls rhythmic activity of GIT
Modified by autonomic NS
What are the groups of spinal nerves?
How are nerves named?
NOTE: in brackets= numbers of pairs in dogs
> Cervical (8)
- Due to C1 roots exiting through the atlas
- Means that C7 vertebra has C8 roots caudally.
> Thoracic (13)
- Labelled by the vertebra cranial to the root
Lumbar (7)
> Sacral (3)
> Caudal (c.4)
Naming:
Nerve is named by vertebra behind it EXCEPT for cervical region as C1 has 2 sets of routes
When do spinal nerves become part of the PNS?
Once spinal nerves have left the vertebral column, they are the PNS
COMPLETE
Typical components of spinal nerves?
Dorsal and ventral rootlets Dorsal and ventral rami Dorsal root ganglion Sympathetic ganglion SEE IMAGE 17
Neuroanatomy intro. SLIDES TO COMPLETE: 27 28 31 33 34 36 37 38 39
COMPLETE
Structural divisions of the NS?
- PNS
Cranial nerves, spinal nerves - CNS
Brain, spinal cord
SEE IMAGE 16 - ENS
Controls rhythmic activity of GIT
Modified by autonomic NS
SEE IMAGE 25
Spinal nerve components:
Explain the roots of spinal nerves?
(Dorsal and ventral- made from several rootlets)
> DORSAL
- Afferent
- Larger
- Contain dorsal root ganglion
> VENTRAL
- Efferent
NOTE: Unite near intervertebral foramen to make spinal nerve
SEE IMAGE 19
Spinal nerve components:
Explain the roots of spinal nerves?
(Dorsal and ventral- made from several rootlets)
> DORSAL
- Afferent
- Larger
- Contain dorsal root ganglion
> VENTRAL
- Efferent
NOTE: Roots unite near intervertebral foramen to make spinal nerve which branches into rami just outside intervertebral foramen
SEE IMAGE 19
Spinal nerve components:
Rami (branches)
Spinal nerve branched into rami just outside intervertebral foramen
DORSAL ramus: to ‘dorsal’ part of body
VENTRAL ramus: to ‘ventral’ part of body incl. limbs
Ventral= larger Both mixed (afferent and efferent)
SEE IMAGE 19
Spinal cord termination: Dog? Cat? Horse? Cattle?
What happens after spinal cord termination?
What is the space around nerves called?
Dog: L6/7
Cat: S3
Horse: S1
Cattle: L7
After this, the cauda equina fills the vertebral canal.
Space around the nerves= epidural space (LINK: epidural anaesthesia)
NOTE: outside spinal cord BUT inside bony spinal section
Where do cervical nerves exit?
How is this different to more caudal nerves?
What is the cauda equina?
What is the filum terminale?
Cervical nn: exit near intervertebral foramina
More caudal nn: have to travel down spinal canal before exiting.
(The bony column grows faster than the spinal cord)
Cauda equina:
Cauda equina region of spinal cord exits AS vertebral column is linger than spinal cord
After spinal cord ends, emergent spinal nerves travel down spinal canal as a group before emerging from their respective intervertebral foraminae
Bony part grows faster than spinal cord and as bone grows, drags nerves with it and so travel down inside of bony canal until they reach their exit through the foramina
e.g. follow 7: comes out earlier where spinal cord stops and then goes back in and exits further down where it should’ve exited= cauda equina forms as lots of nerve are doing this
Filum terminale:
End of meninges, continues into first few caudal vertebrae
Anchors bottom part of spinal cord
(‘Just a membrane part’)
NOTE:
Spinal cord segments are named by the foramen they exit from
SEE IMAGE 20
3 main sections of brain?
Cerebrum
Cerebellum
Brainstem
SEE IMAGE 21
More neurones in cerebellum or cerebrum?
More neurones in cerebellum than in cerebrum- relative size does not necessarily relate to number of neurones contained here
Main structures in brain cross-section?
Corpus callosum (only in mammals) Pituitary gland Inter-thalamic adhesion Pons (this is directly attached to pons) Medulla SEE DIAGRAM 22
Purpose of folds within the brain?
Increase brain SA
Fibre content of cranial nerves?
Mixed fibre content for different cranial nerves:
Motor (III, IV, V3, VI, VII, IX, X, XI, XII)
Sensory (I, II, V1, V2, V3, VII, VIII, IX, X)
Autonomic (PSNS: III, VII, IX, X)
(NOTE: there are variations, so this is a basic list)
Arranged segmentally, but constraints of the skull means the resultant physical pattern masks this
Cranial nerve function?
SEE IMAGE 23
ENS:
What is the smooth muscle of the GIT controlled by?
2 local nerve plexi control smooth muscle of GIT:
Meissner’s plexus: in submucosa
Auerbach’s plexus: between smooth mm layers
Operte autonomously: controls motility, local hormone reflexes
Modified by: autonomic NS
ENS:
Cross-section of gut schema?
SEE IMAGE 24
General neural structure:
Neurons?
Nueoglia?
Insulation?
Neurons= The actual conducting cells (functional units of NS) Neuroglia= Supporting/maintaining cells (outnumber neurons by 10:1) Insulation= Via lipid sheaths around inflow/outflow
Connective tissue in CNS?
No connective tissue in CNS:
- No obvious boundaries
- Blood vessels supported by neuroglia
(NOTE: connective tissue sheaths in PNS)
(NOTE: Nerves in the body are thicker than where they originated)
2 main types of neuroglial cells?
1.) MICROGLIA
> Specialised macrophages
> Mobile
> Control inflammation
2.) MACROGLIA > Oligodendrocytes - Insulators in CNS (learn) > Schwann cells - Insulators in PNS (learn) > Astrocytes - Control local environment of CNS > Satellite cells - Similar role to astrocytes > Ependymal cells - Make CSF and form blood-CSF barrier > Radial glia - Progenitor cells > Enteric glia - Found in GIT ganglia
Oligodendrocytes= 1 big cell and wrap around multiple cells and Schwann cells= long hotdog with multiple pieces of bread with nodes of ranvier being the spaces between these buns
Neurons: general structure?
COMPLETE SLIDE 9 NOTES SECTION
Large cells
Cell body (soma, perikaryon)
Processes (include one axon and one or more dendrites)
SEE IMAGE 26
3 main types of neuronal junctions?
- ) Synapses:
- Neuron-to-neuron
- Excitatory or inhibitory
- Only in grey matter - ) Neuromuscular junctions:
- Neuron-to-muscle cells
- Always excitatory in case of skeletal muscle - ) Neuroglandular junctions:
- Neuron-to-glandular cells
- Most secretory glands
SEE IMAGE 27
Polarity of neurones?
UNIPOLAR neurons
- (Pseudo-) unipolar- 1 process leaves cell body, then splits into 2:
- Structurally: resemble axons
- Functionally: 1 acts as axon, 1 acts as dendrite
- characteristic of general sensory neurons
- Cell bodies often grouped together in ganglia (collection of nerve cell bodies in PNS)
- Sensory neurones
BIPOLAR neurons
- 1 axon, 1 dendrite
- Fairly uncommon, mainly special sensory pathways (vision, taste, hearing, balance)
MULTIPOLAR neurons
- 1 axon, multiple dendrites
- Most numerous type
- Groups of such nerve cell bodies in CNS are termed nuclei
- Motor neurones
- Inter-neurones
Structural types of neurons?
AFFERENT (sensory):
Convey information towards CNS (i.e. info. is coming in)
EFFERENT (motor):
Convey information away from CNS
What are interneurons?
= association neurons
- Connect/associate 1 point with another in CNS BUT never leaves CNS
- Most numerous type of neuron
(e.g. link sensory and motor neurons together)
Divisions of NS 2 SLIDES TO COMPLETE: 5 6 8 10 13 14
COMPLETE
Functional components of PNS:
- ) Sensory?
- ) Motor?
1.) SENSORY: > GENERAL= - Somatic pain, temperature, touch (GSA) - Kinaethesia, proprioception (GSA) - Visceral sensation inc baroreceptors (GVA) > SPECIAL= - Vision & hearing (SSA) - Balance (SSA) - Taste & olfaction (SVA)
2.) MOTOR:
> GENERAL SKELETAL MUSCLES=
- Somatic efferent (GSE) – muscles of “somatic origin”
> GENERAL VISCERAL MUSCLES=
- *Autonomic - smooth muscle, cardiac muscle, glandular tissue (GVE)
> SPECIAL VISCERAL EFFERENT=
- Muscles derived from pharyngeal arches (SVE).
Composition of cranial nerves?
Cranial nerves:
General somatic afferent (GSA)
General visceral afferent (GVA)
Special somatic afferent (SSA)
Special visceral afferent (SVA)
General somatic efferent (GSE)
General visceral efferent (GVE)
Special visceral efferent (SVE)
What is the autonomic nervous system (ANS)?
= part of the PNS supplying efferent (motor) fibres to “visceral structures” i.e. GVE fibres
- Controls: intrinsic rhythms e.g. Cardic, Enteric
- Control centres in the CNS (medulla)
- Sympathetic
- Parasympathetic
(NOTE: Parasympathetic= controlled in different sections (e.g. heartrate and bladder are controlled independently (as organs usually) BUT sympathetic= controlled all as one (body ‘wakes up’)
Neurons: general structure?
COMPLETE SLIDE 9 NOTES SECTION
> Large cells
3 main regions:
a.) Cell body (soma, perikaryon)= receptive area
- Nutritional centre & large molecules production, impulse transmission
b.) 1 axon (process 1)
- Surrounded by Schwann cells
- Conduct impulse away from the cell body to axon terminals (transmission area)
c.) 1 or more dendrites (process 2.)= receptive area
- Receptive area for impulse transmission
SEE IMAGE 26 (2 parts)
What is the autonomic nervous system (ANS)?
= part of the PNS supplying efferent (motor) fibres to “visceral structures” i.e. GVE fibres
> CONTROLS: intrinsic rhythms e.g. Enteric
- Control centres in the CNS (medulla)
> SYMPATHETIC AND PARASYMPATHETIC (Opposite effects, but work in harmony not pure antagonism):
- Sympathetic=
* Spinal outflow T1 to L3
* General increase in alert state: Fear, flee, fright, fun & frolic
* Widespread effects
- Parasympathetic=
* Outflow in cr.n. 3,7,9,10 and sacral nn.
* Local control of action e.g.: Urination, salivary glands, GIT, heart rate.
.
(NOTE: Parasympathetic= controlled in different sections (e.g. heartrate and bladder are controlled independently (as organs usually) BUT sympathetic= controlled all as one (body ‘wakes up’)
SEE IMAGE 29
What 2 principal types of cells are the CNS and PNS composed of?
1.) Neurons
Produce and transmit the nerve impulse Present in the nerves
2.) Supporting cells Aid/assist the function of neurons
5-10 times more abundant than neurons especially in the brain
How are neurons classified by STRUCTURE?
= neurons are classified by structure: based on number of processes that extend from cell body
UNIPOLAR neurons
- (Pseudo-) unipolar- 1 process leaves cell body, then splits into 2 to cell body:
- Structurally: resemble axons
- Functionally: 1 acts as axon, 1 acts as dendrite
- characteristic of general sensory neurons
- Cell bodies often grouped together in ganglia (collection of nerve cell bodies in PNS)
- (Sensory neurons- One of the branched process receive sensory stimuli → nerve impulse delivering the signal to the CNS)
BIPOLAR neurons
- 1 axon, 1 dendrite
- Fairly uncommon, mainly special sensory pathways (vision, taste, hearing, balance)
- Found in retina, inner ear, brain (olfaction area only)
MULTIPOLAR neurons
- 1 axon, multiple dendrites
- Most common type
- Groups of such nerve cell bodies in CNS are termed nuclei
- May have different structure/shape based on their location in either the CNS or the PNS e.g. Pyramidal Cells (Cortex)
- (Motor neurons)
SEE IMAGE 28 (2 parts)
What are interneurons?
= association neurons
- Connect/associate 1 point with another in CNS BUT never leaves CNS
- Most numerous type of neuron
(e.g. link sensory and motor neurons together)
Cellular components in NS: nerve
Composition of nerves?
Composition of nerve fibres?
Nerve is composed of: Several bundles of nerve axons (nerve fibres) held together by connective tissue
Most nerves contain sensory AND motor fibres
Nerve fibre is composed of:
a. ) EPINEURIUM=
- Outermost, protective layer (strength)
- Consists of dense connective tissue, rich in collagen fibres
b. ) PERINEURIUM
- Surrounds each individual fascicle
- It is an epithelial layer that isolates bundle of axons from surrounding connective tissue
- Encloses fluid-filled space between perineurium and underlying nerve axons
- Connective tissue within perineural sheath= endoneurium
c. ) ENDONEURIUM
- Includes seams of loose connective tissue to provide pathways for small arterioles, venules and axons
SEE IMAGE 30
Where are NT’s/proteins proteins synthesised and how are they transported?
> Synthesised in cell body (Nissl bodies)
Transported via:
- Axoplasmic flow= contractions that push cytoplasm from axon hillock to nerve endings
- Axonal forward/retrograde transport= to/from nerve endings (via microtubules and kinesins, viruses & bacteria infecting the CNS take this route)
Neurons:
Axoplasm?
Axolemma?
Neurolemma?
Axoplasm= axon’s cytoplasm
Axolemma= axon’s membrane
Neurolemma= outer most layer of nerves fibres in the PNS. It is a cytoplasmic layer of Schwann cells that surround the multiple wrapping of myelin.
Neurons:
Axoplasm?
Axolemma?
Neurolemma?
Axoplasm= axon’s cytoplasm
Axolemma= axon’s membrane
Neurolemma= outer most layer of nerves fibres in the PNS. It is a cytoplasmic layer of Schwann cells that surround the multiple wrapping of myelin
How are neurons classified by FUNCTION?
SENSORY (AFFERENT) NEURONS:
Conduct impulses from sensory receptors INTO CNS
ASSOCIATION (INTERNEURONS):
Located in the CNS and serve the associative or integrative functions of the nervous system. They bridge sensory & motor neurons.
MOTOR (EFFERENT) NEURONS:
Conduct impulses OUT OF the CNS to effectors smooth m., cardiac m., skeletal m. & glands
How are neurons classified by FUNCTION?
SENSORY (AFFERENT) NEURONS:
- Conduct impulses from sensory receptors INTO CNS
- Mechano/chemo/thermo/ photo/electro/magneto/noci -ceptor (see other flaschard)
- SEE IMAGE 31
ASSOCIATION (INTERNEURONS):
- Located in the CNS
- Associative or integrative functions of the nervous system
- They bridge sensory & motor neurons:
Provide direct (reflex arcs) or indirect (via brain structures) connections between motor and sensory neurons AND between themselves
- Switch on or off the signal that is coming from outside
- SEE IMAGE 32
MOTOR (EFFERENT) NEURONS:
- Conduct impulses OUT OF the CNS to effectors smooth m., cardiac m., skeletal m. & glands
- Somatic motor neurons= reflex and voluntary control of skeletal muscle
- Autonomic motor neurons= innervate involuntary effectors smooth/cardiac m. & glands. The cell bodies are outside the CNS regrouped in ganglia. Autonomic neurons are also subdivided into sympathetic and parasympathetic (= autonomic NS)
Different types of sensory (afferent) neurons?
MECHANORECEPTOR:
Inner ear, muscles, tendons, large blood vessels & heart
CHEMORECEPTOR:
Mouth, nose, large blood vessels, brain
THERMORECEPTOR:
Skin and brain
PHOTORECEPTOR:
Eye
ELECTRORECEPTOR:
Skin (fish)
MAGNETORECEPTOR:
Eye (seems to be a kind of modified photoreceptor)
NOCIRECEPTOR:
Most parts of the body (sense the pain)
Which Supporting (glial) cells are in:
PNS?
CNS?
PNS:
Schwann cells
Satellite cells
CNS: Oligodendrocytes Astrocytes Microglia Ependymal cells
Explain supporting cells in PNS?
> SCHWANN CELLS:
- Schwann cells form myelin sheath around axons
- Each Schwann cell wrap ~1mm along the axon. Ranvier nodes between Schwann cells
- Myelin= electrical insulation and increases speed of impulse conduction (saltation). Allows impulse propagation over large distance without dissipation
> SATELLITE CELLS:
- Support functions (homeostasis) of neurons within the sensory and autonomic ganglia
- Can control the micro-environment of neurons
SEE IMAGE 32
Comparative speed of conduction:
Motor/sensory neurons?
Preganglionic?
Postganglionic?
Preganglionic= Fastest
Motor/sensory neurons= Middle
Postganglionic= Slowest
NOTE: axon diameter increase= increase conduction speed
What are ganglia?
Aggregations of neuron cell bodies outside of the CNS
These cell bodies are associated with pseudo-unipolar (somatic sensory) neurons and are located within dorsal root ganglions
The ganglion cells have centrally-located nuclei and a surrounding capsule, which consists of an inner portion of satellite cells
= Clusters of cells involved in autonomic nervous system
Explain supporting cells in CNS?
> OLIGODENDROCYTES:
- Form myelin sheath around axons
- Oligodendrocytes → white matter
- Cell bodies & dendrites → grey matter
> ASTROCYTES (filter everything travelling into nervous system):
- Help to form junction between capillaries and neurons
- They have processes that terminate in end-feet surrounding the capillaries of the CNS. The feet are involved in the formation of tight junctions between epithelial cells in capillaries
- Maintain ionic environment (have ion channels): buffer blood ionic concentration
- Take up some neurotransmitters released from the axon terminal of neurons and deliver them to neurons for re-use
- Involved in blood-brain barrier (NOTE: capillaries in brain only have tight junctions, NO gaps)
- Transform glucose from blood into lactate (lactic acid) which is released to neurons as energetic source for ATP production
> MICROGLIA:
- Phagocytose pathogens and cellular debris (immune system of brain/spinal cord)
- Relatively small, changing shape, oblong nuclei
- Found in all regions of brain/spinal cord
- Mobile in brain and multiply when brain is damaged
- In healthy CNS: microglia processes constantly sample environment (neurons, other supporting cells and blood vessels)
> EPENDYMAL CELLS:
- Line cavities (ventricles and central canal of spine) of CNS
- Produce CSF in ventricles by filtering blood from capillaries (Ependymal cells regulate glucose, amino acids (Cf. NTs) & ions level)
- Beat their cilia to help circulate the CSF (good circulation of CSF is crucial for nourishment of CNS)
Difference between oligodendrocytes and Schwann cells?
Schwann cells wrap 1 single axon, oligodendrocytes wrap several axons
BUT
They have similar properties with regard to nerve impulse (AP)
Function of CSF?
= liquid surrounding brain and spinal cord and fills spaces in them Supports brain
Lubricant
Maintains pressure in skull
Cushions shocks
Good circulation of CSF = crucial for nourishment of CNS
How is a signal transmitted between 2 neurons?
What is a synapse?
From presynaptic to postsynaptic cell via synaptic junction
Synapses= means the specific cellular areas participating in the nerve impulse transmission
SEE IMAGE 33 (2 parts)
Brain orientation terminology?
SEE IMAGE 34
Features of the brain: Sulcrus? White matter? Grey matter? Cerebral cortex (grey matter)? Gyrus? Fissure?
Gyrus= a ridge or fold between two clefts on the cerebral surface in the brain Sulcus= a shallower groove that surrounds a gyrus Fissure= a large furrow that divides the brain into lobes and also into the two hemispheres as the longitudinal fissure
SEE IMAGE 35
Structures of the brain: Right cerebral hemisphere Venous sinus Arachnoid villus Cerebellum Subarachnoid space Central canal 4th ventricle Aqueduct 3rd ventricle ?
SEE IMAGE 36
Development of the brain?
What are the main sections of the brain?
SEE IMAGE 37
Main sections of the brain=
Fore, mid and hind brain
Anatomical subdivisions of the brain?
SEE IMAGE 38
Are brain stem/hindbrain anatomical/functional divisions?
Brain stem= a functional division
Hindbrain= an anatomical division
What does the brainstem consist of?
Medulla oblongata
Pons
Midbrain/mesencephalon
SEE IMAGE 39
Slide 12
ECHO
Slide 14
COMPLETE
Brainstem- Medulla oblongata and pons:
Functions?
> Location of important regulatory centres:
-Respiratory
-Blood pressure
-Heart rate
Several cranial nerves emerge and have their nuclei here, many functions e.g. hearing, balance, swallowing, mimic musculature, masticatory musculature, salivation, parasympathetic
What does the hindbrain consist of?
Medulla oblongata
Pons
Cerebellum
What does the hindbrain consist of?
Medulla oblongata
Pons
Cerebellum
Brainstem- Mesencephalon/midbrain:
Parts of the midbrain?
- Tectum (four colliculi)
- Tegmentum (several nuclei)
- Crus cerebri (crura cerebri)
- Aqueductus mesencephali
NOTE: Colliculi= important in reflexes
Brainstem- Mesencephalon/midbrain:
Functions?
- Optic reflexes (rostral colliculi)
- Regulation of motor functions (head)
- Eye movement (visual reflexes)
- Arousal
What does the forebrain consist of?
TELENCEPHALON- hemispheres
(Cerebral cortex, basal ganglia, limbic system)
DIENCEPHALON- part of brain between the hemispheres
(Thalamus, hypothalamus, epithalamus)
SEE IMAGE 40
What is the diencephalon made up of?
Thalamus
Epithalamus
Hypothalamus: around 3rd ventricle
SEE IMAGE 41
What is the diencephalon made up of?
Function of these areas?
> Thalamus=
- Relay station for sensory info.
> Epithalamus
> Hypothalamus: around 3rd ventricle=
- Hormonal regulation
- Reproduction
- Appetite
- Flight/Fight
- Stress
SEE IMAGE 41
Interbrain
COMPLETE
Slide 22
What is the telencephalon made up of?
= cortex AND subcortical structures
> Cortex (divides into 3 types of cortex):
- Neocortex
- Archicortex
- Paleocortex
> Subcortical:
- e.g. basal ganglia
NOTE: neocortex= what is seen from the outside, subcortical structures are located much deeper in the brain
SEE IMAGE 42
Telencephalon continued
COMPLETE slide 26
TELENCEPHALON:
Function of the 3 layers of cortex?
> Paleocortex (paleopallium)=
Related to olfactory sense
TELENCEPHALON- 3 main types of cortex:
- ) Paleocortex (Palleopallium):
- What is it made up of?
- What is it’s function? - ) Archicortex
- What is it made up of?
- What is it’s function? - ) Neocortex
- What is it made up of?
- What is it’s function?
1.) Paleocortex (paleopallium)=
- Main areas: Olfactory bulb, olfactory tract
rostral commissure, piriform lobe
NOTE: piriform lobe= pear-shaped lob
SEE IMAGE 43 - Function: Related to olfactory sense
2. ) Archicortex (oldest part of the brain)= - Main areas:
Hippocampus and dentate gyrus
SEE IMAGE 44 - Function:
Memory generation- particularly spatial memory
3.) Neocortex (dominant part of cerebral cortex in mammals)=
- Main areas:
Corpus callosum?- check (corpus callosum= major connection between hemispheres)
SEE IMAGE 45
SEE IMAGE 46 - Function:
(Planning of) movement, perception, learning, memory
Slide 28- image
Slide 29- image and echo
Slide 31- image and echo
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s
s
Structure of the cortex?
Functions of the cortex?
Structure: SEE IMAGE …
Functions: Frontal lobe= motor cortex Parietal lobe= sensory cortex Temporal lobe= hearing Occipital lobe= vision
Summary of function: Principal structures= Cerebral cortex Basal ganglia Limbic system Thalamus Hypothalamus Tectum Tegmentum Cerebellum Pons Medulla oblongata Principal functions of these?
Cerebral cortex=
- (planning of) movement, perception, learning
Basal ganglia=
- coordination of movement
Limbic system=
- emotion, learning and memory
Thalamus=
- “switchboard” for neural input
Hypothalamus=
- appetite, reproduction, autonomic responses
Tectum Tegmentum=
- visual reflexes, audition
- sleep, arousal, pain, part of motor system
Cerebellum=
- integration and control of posture and movement
Pons=
- sleep, arousal
Medulla oblongata=
- heart rate, breathing, blood pressure
Structure of the cortex?
Functions of the cortex?
Structure:
SEE IMAGE 47
SEE IMAGE 48 (primary sensory and motor cortex, association cortex)
Functions: Frontal lobe= motor cortex Parietal lobe= sensory cortex Temporal lobe= hearing Occipital lobe= vision
NOTE: Sensory projections end up in visual cortex area
What is the Limbic System?
Not a ‘system’ as such- areas involved in major processes for survival (system involved in basic survival)
Functionally and anatomically connected but NOT all a system together
Hippocampus- involved in memory
Amygdala- involved in emotion e.g. happiness
Main areas invovled: the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus
SEE IMAGE 49
Gross anatomy and function of the brain SLIDES TO COMPLETE: 12 14 18 22 26 28 29 31
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Gross anatomy and function of the brain SLIDES TO COMPLETE: 12 14 18 22 26 28 29 31
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What is behaviour?
Behavioural level of study?
Behaviour= Behaviour is the interaction between an organism and its environment that is based on the exchange of information between the two
Behavioural level= what you can observe (can also go into the genetic basis of behavior but not necessary yet)
What is ethology?
= Study of animal behaviour, but
also stands for a (sub)discipline in behavioural
sciences
What is anthropromorphism in this context?
Opposing our perception on how an animal works/how animal perceives environment/processors information AND projecting our own interpretation (e.g. how WE would react/think) onto an animal
Apply emotion to an animal
Can be negative BUT could be useful as increasing evidence that animals are cognitive (structures in behaviour which are not too dissimilar to humans)- gives some ideas to then follow up with scientific research
Main components environment can be classified into?
OWN BODY AS ENVIRONMENT
Living and non-living objects
SOCIAL ENVIRONMENT
(CONSPECIFIC)
Input -> Organism -> Output -> Act on environment (all 3 components)
SEE IMAGE 50
What is the three vector model of behaviour?
Input vector -> State vector (organism) -> Output vector
Three vector model of behaviour:
Explain input vector?
INPUT VECTOR=
- Senses and brain work together to interpret information coming from the environment- this complex process= input vector
- E.g. optical illusions: our mind tries to make sense of what we see
Three vector model of behaviour:
INPUT VECTOR: sign stimulus?
How can you predict the sign stimuli?
NOTE: Input is MORE than just light stimulus on retina- it is ALSO the behaviour that modifies the perception
INPUT VECTOR- SIGN STIMULUS=
- Key features of a stimulus that evokes a particular response (usually just small parts of environment- e.g. any trait of animal/plant/object)
- Describes simple features (red feathers) of complex stimulus (male robin) that bring about particular fixed action pattern
- Certain stimuli can induce/release a relatively invariable motor response or a relatively invariable complex motor behaviour
Predicting sign stiumuli: Know what sensory organs are used by an animal and you can predict the sign stimuli: - Visual cues (color, shape, and motion) - Chemical cues (“odor” and taste) - Sounds
EXAMPLE:
A male European robin in breeding condition
will attack a tuft of red feathers
placed in his territory.
NOTE: The fact that some stimuli are „easy“ to be processed („sign stimuli“) is an example how evolution shaped information processing in many species
e.g. larger egg will appear more ‘attractive’ to bird and so it will attempt to brood this instead of its own egg
Three vector model of behaviour:
Explain status vector?
What is neuroethology?
> Relevant status variables:
- Triangle of: Motivation Emotion Memory (Motivation etc..)
> Status variables
- Learning and memory
- Emotion
- Motivation
- Arousal
= processing, storage and modification/alteration of information
(ECHO BEHAVIOUR LECTURE TO UNDERSTAND FURTHER)
> Neuroethology:
Linking behaviour to activity pattern in the brain (e.g. bug detectors in frog are unresponsive to group of dots in field moving but can recognise one dot moving)
Three vector model of behaviour:
Explain output vector?
OUTPUT VECTOR=
- Describes elements of behaviour that are:
- generated by an animal
- accessible through observation
- Expression of particular behaviour can be species-specific
- E.g.: birdsong, locomotor behaviour
Analysing behaviour- Ethogram
Recording methods?
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Slide 51
Slide 52
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Slide 52, 53, 54
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Understanding behaviour:
Tinbergen’s four levels of behavioural explanation (“Four Whys”)?
Why?
Function (what is the behaviour for?)
Evolution (where does the behaviour come from?)
How?
Mechanism (how is the behaviour achieved?)
Development (how does the behaviour develop in ontogeny?)
NOTE: important to answer these questions to fully understand the behaviour
Understanding behaviour:
Different levels of explanation?
- ) Proximate explanations (How?)
- Relate to the mechanisms which bring about the expression of the behaviour:
* Physiology
* Aetiological factors - ) Ultimate explanations (Why?)
- Explain why proximate processes should arise:
* Function
* Adaptiveness
Instinct and drive in behaviour?
Instinct and drive are less relevant
Instinct is more out-dated now
Instinct is not needed and drive is less of a useful explanation
How can behaviour be measured?
Ethogram, spatio-temporal characteristics
Structure of behaviour- time?
Circadian rhythms
Sleep patterns
Structure of behaviour- biological rhythms:
- Definition?
- Chronobiology?
- Example?
Rhythm= a function which oscillates or cycles at a regular frequency
Biological rhythms= overt, measurable activities generated by some internal oscillator (or ‘clock’)
Chronobiology= a field of science that examines periodic (cyclic) phenomena in living organisms and their adaptation to external (environmental) rhythms
Example:
Circadian= A daily rhythmical change in behaviour or in a physiological process, such as sleep (melatonin increases during night-time) (NOTE: usually 24 hour cycle)
Structure of behaviour- biological rhythms:
- Definition?
- Chronobiology?
- Example?
Rhythm= a function which oscillates or cycles at a regular frequency
Biological rhythms= overt, measurable activities generated by some internal oscillator (or ‘clock’)
Chronobiology= a field of science that examines periodic (cyclic) phenomena in living organisms and their adaptation to external (environmental) rhythms
Example:
Circadian= A daily rhythmical change in behaviour or in a physiological process, such as sleep (melatonin increases during night-time) (NOTE: usually 24 hour cycle)
Examples of rhythms:
- Infradian
- Ultradian?
> Infradian:
- Rhythm with a period longer than the period of a circadian rhythm, i.e. with a frequency less than one cycle in 28 hours (cycle with a period which is longer than 24 hours)
- Example: reproduction cycles
- Example: Seasonal- SEE IMAGE 51
> Ultradian:
- Rhythms with period shorter than the period of a circadian rhythm - Example: REM (rapid eye movement) cycle in sleep
Structure of behaviour- time, biological rhythms:
Function of biological rhythms?
Zeitgeber meaning?
Biological clock are internal physical systems that enable organisms to live in harmony with rhythms of nature e.g. day/night/seasonal cycles
= EXTERNAL synchronisation
Circadian systems also maintain temporal organisation of endogenous processes
= INTERNAL synchronisation
Zeitgeber ("time giver", synchronizer)=
any external (exogenous) cue that entrains the internal (endogenous) time keeping system of organisms
Strongest Zeitgeber for plants/animals= light. Other examples= social interactions, pharmacological manipulation and eating/drinking patterns
Zeitgeber -> Entrainment -> Endogenous rhythm
The physiological basis of rhythms: Biological clocks
- Where?
1.) Retina – but no cones and rods required?
A photo pigment present in ganglion cells in the retina whose axons transmit information to the SCN, the thalamus, and the olivary pretectal nucleus
SEE IMAGE 52
2.) Suprachiasmatic nucleus (SCN) A nucleus situated atop the optic chiasm Contains a biological clock that is responsible for organizing many of the body’s circadian rhythms. SEE IMAGE 53 SEE IMAGE 54 (2 parts)
3.) Pineal gland:
Amino acid (tryptophan) derivative
Location= attached to dorsal tectum, immediately behind thalamus
Produces melatonin (hormone) and plays a role in circadian and seasonal rhythms by responding to light:
* More melatonin when dark (night)
* Less melatonin when light (day)
* Melatonin induces sleep (therapy?)- also other mechanisms involved in sleep
SEE IMAGE 55 (2 parts)
Circadian rhythms:
How is melatonin involved in short and long day breeders?
In long day breeders= represses reproduction
e.g. horse, fox, ferret (Spring)
In short day breeders=
stimulates reproduction
e.g. sheep, goat (Autumn)
How does light cause an affect on biological rhythms (i.e. biological clock)?
Light enters eye
Info. (light/dark) transferred from retina to SCN (biological clock)
SCN sends neuronal signals to pineal gland to secrete melatonin (high in dark)
NOTE: Melatonin also appears to be involved in synchronizing circadian rhythms.
Slide 24
ECHO
Summary of circadian rhythms?
Circadian timekeeping is a fundamental property of all higher forms of life
In mammals, the principal circadian mechanism lies in the individual neurones of the suprachiasmatic nucleus
Comparative studies of the clock in mammals and fruit flies have provided a model of autoregulatory feedback to explain its basic properties
The genes encoding this feedback loop, and how they and their protein products respond to synchronising cues, are being characterised
This opens the way for an understanding of how genes regulate a basic aspect of behaviour and what are suitable targets for intervention when this timing mechanism breaks down
Slide 4
EACH SINGLE MUSCLE FIBRE IS INNERVATED BY A SINGLE MOTOR-AXON.
CONTRACTION IS AN ALL OR NOTHING EVENT.
Therefore increased force generation is produced by recruiting more fibres (e.g. more fibres recruited to pick up a table than to pick up a book).
However a single motor-axon can innervate more than one muscle fibre
Axon fires= contraction (ALL OR NOTHING
What is a motor unit
A single α-motor neuron and all of the corresponding muscle fibres it innervates.
Two tissues that inter-dependent
Skeletal muscle MUST have axons going to it to function
SEE IMAGE
Single motorneuron & muscle fibers it innervates
Eye muscles – 1:1 muscle/nerve ratio
Hamstrings – 300:1 muscle/nerve ratio
In some cases thousands of fibres per axon
Most MU’s are quite small which gives gradation- recruit a lot of axons to recruit entire muscle
All fibres in a MU innervated simultaneously,
All same fibre-type.
MU size dictates level of control.
SEE IMAGE
MU properties
IMAGE
Distribution
Glycogen depletion method has shown that fibres belonging to the same MU can extend over a large area
Deep areas of a muscle tend to be redder and superficial areas paler
Can look at MU size by: Innervate specific axons and look at which muscle fibres the glycogen is depleted in
SEE IMAGE
Recruitment
Slow motor units tend to be smaller and during normal exercise tend to be recruited first.
Henneman’s size principle
This can be seen using electromyography (EMGs). During ballistic locomotion (e.g. jumping) faster MUs can be recruited initially (Henneman’s size principle is not used and so all of the fibres can be recruited at the same time) Generally: slow muscle fibres recruited first and then intermediate and then fastest Can look at fibre recruitment using myography
Slide 4
How are muscles innervated?
How is force generation increased?
Each single muscle fibre is innervated by single motor-axon
(However: a single motor-axon can innervate more than one muscle fibre)
Contraction= ALL OR NOTHING EVENT
SO
Recruiting more fibres= increased force generation produced (e.g. more fibres recruited to pick up a table than to pick up a book)
Most MU’s are quite small which gives gradation- recruit a lot of axons to recruit entire muscle
What is a motor unit?
= A single α-motor neuron and all of the corresponding muscle fibres it innervates
Two tissues that inter-dependent
SEE IMAGE 56
(NOTE: Skeletal muscle MUST have axons going to it to function)
All fibres in a MU innervated simultaneously,
All same fibre-type in MU
MU size dictates level of control
SEE IMAGE 57
Eye:
Muscle/nerve ratio?
Hamstrings:
Muscle/nerve ratio?
Eye muscles – 1:1 muscle/nerve ratio
Hamstrings – 300:1 muscle/nerve ratio
NOTE: can be thousands of fibres per axon
Properties of motor units?
SEE IMAGE 58
Explain distribution of MU’s?
How can MU size be examined?
Fibres belonging to the same MU can extend over a large area (Glycogen depletion method has shown this)
Deep areas of a muscle= redder Superficial areas= paler
Can look at MU size by: Innervate specific axons and look at which muscle fibres the glycogen is depleted in
SEE IMAGE 59
How are different motor units recruited during different levels of exercise?
> Slow motor units (usually):
- Smaller
- Recruited first during normal exercise
= Henneman’s size principle (under load, motor units are recruited from smallest to largest)- can see fibre recruitment using EMG’s
> During ballistic locomotion (e.g. jumping):
- Faster MUs can be recruited initially (Henneman’s size principle is not used and so all of the fibres can be recruited at the same time)
Generally: slow muscle fibres recruited first and then intermediate and then fastest
Neuromuscular junction diagram?
Function of calcium in this?
SEE IMAGE 60
SEE IMAGE 63
Level of calcium is usually higher on outside (in extracellular) than on inside SO VGC opens as AP travels down axon, allowing calcium to flood in
In this case it is NOT sarcoplasmic reticulum/sarcolemma. INSTEAD: floods into VGC and into axon and vesicles fuse with presynaptic membrane which releases acetylcholine (through exocytosis) and ach crosses to postsynaptic membrane, causing depolarisation of muscle fibre
SEE IMAGE
Difference between myopathy and neuropathy?
What can be used to distinguish between these? What is this based upon?
Why can it be difficult to distinguish between them?
Difference:
Myopathy= condition which is intrinsic to muscle itself
Neuropathy= intrinsic to nerves supplying the muscle
Used to distinguish between these:
The motor unit action potential (MUAP)
This is based upon size, shape and recruitment pattern.
Can be difficult to distinguish between them because:
they are so inter-connected
(NOTE: Electromyography can be used)
What is Electromyography (EMG)?
How does it work?
What can insertional and spontaneous activity indicate?
= a technique for evaluating properties of muscles at rest and while contracting.
- Electrodes (surface or needle electrodes) detect the electrical potential generated by active muscle cells (activity detected by electrodes as coming from particular muscles)
NOTE: Needle electrode preferable to study MUAPs preferable (goes into muscle tissue itself)
The insertional activity:
provides valuable information about the state of the muscle and its innervating nerve
Abnormal spontaneous activity (e.g. electrical activity being detected even when muscle is not active):
might indicate some nerve or muscle damage
EMGs and disease?
Laryngeal hemiplegia: can be used to detect neuropathy
NOTE: Insertional needle EMG can be used in laryngeal hemiplegia to study state of the myopathy
Cushing’s disease in horses: despite pronounced myopathy there is little change in EMG pattern
Can be used for some condition but not for others
How are muscle length and tension regulated?
How do antagonistic muscles work together?
Animal must be aware of muscle length/tension (automatic process)
Young: muscles and bones can get twisted if they are not aware
Adults: must be aware for coordination
Receptors in muscles:
> Muscle spindle=
- Detect dynamic and static changes in muscle length
- Stretch reflex (stretch on muscle causes reflex contraction)
> Golgi tendon organ (GTO)=
- Monitor tension developed in muscle
- Prevents damage during excessive force generation (stimulation results in reflex relaxation of muscle):
Muscle contraction -> puts tension on tendon -> sends sensory stimulus to spinal cord -> sends signal to muscle -> reduces tension (protects muscle and tendon)
SEE IMAGE 61
NOTE: Awareness of tension= protection mechanism (prevents damage)
SEE IMAGE 32 (relevant again under title ‘receptors in muscle’)
Neural input and output?
SEE IMAGE 62
For 50 muscle spindles, you’ have 100 motor nerve fibres
Muscle spindles are highly innervated compared to extrafusal muscle fibres
Golgi tendon organs have quite strong sensory impact
What is the basic structure of motivated behaviour?
Phase 1- Orientation
Phase II- Oriented
Phase III- Consumption
Flexibility/variability of behaviour decrease from phase I to phase III
Oriented behaviour= have a clue
‘Eating’ is used as an example here but it is not the only one
Travel to New York, hungry, search for cue which indicates a target (flexibility and variability of behaviour is quite high to start with before the cue is found e.g. may swap restaurants before finding mcdonalds BUT these decrease once the cue is found e.g. will go to mcdonalds once you have found it)
Seen in almost any animal
Stuck in hotel room and fixated on mcdonalds, once you get out your flexibility and variability will decrease as this is where you want to go
What is the basic structure of motivated behaviour?
Phase 1- Orientation
Phase II- Oriented
Phase III- Consumption
Flexibility/variability of behaviour decrease from phase I to phase III
EXAMPLE:
Oriented behaviour= have a clue
‘Eating’ is used as an example here but it is not the only one
Travel to New York, hungry, search for cue which indicates a target (flexibility and variability of behaviour is quite high to start with before the cue is found e.g. may swap restaurants before finding mcdonalds BUT these decrease once the cue is found e.g. will go to mcdonalds once you have found it)
Seen in almost any animal
Stuck in hotel room and fixated on mcdonalds, once you get out your flexibility and variability will decrease as this is where you want to go
NOTE:
There is feedback at any stage (feedback used to readjust motivation e.g. something wrong with the food -> go and eat somewhere else)
Motivation definition?
Internal decision-making process by which the animal chooses to perform a particular behaviour
(Chris Barnard)
Drive: Difficulties and Debates?
- No evidence for energy associated with motivational states in the CNS
- Little explanatory power: Saying, an animal feeds because of a hunger drive is circular
- Drives can be subdivided almost endlessly - little explanatory value
- Unitary drives (hunger, thirst) can incorporate a wide range of conditions
- Classical models omit feedback from the consequences of behaviour
- Response to a given drive affect also other aspects of internal state (e.g. feeding – thirst)
Internal stimuli in animal motivation?
Internal stimuli in animal motivation?
Weakness of these explanations?
External cues are particularly important: escape, aggression, predatory responses, exploration
Internal cues are particularly important: reproductive behaviour, ingestive behaviours
HOWEVER: this is a simplification – the contribution of internal and external cues varies: species and motivation dependent with individual differences occurring as well
Wallace Craig: Structure of motivated behaviour?
APPETITIVE:
Various initial motor patterns that bring the animal into a situation where it was likely to encounter a “stimulus”
(As if the animal had an “appetite for the stimulus”)
Phase I: No evidence of “stimulus” (e.g. prey): non-directed
Phase II: Stimulus detected (e.g. sight of prey), eventually capturing prey/ finding food: – directed
Phase III: Consummatory (killing prey, eating)
Phase IV: “Satiation” (=condition of being full to or beyond satisfaction)
CONSUMMATORY:
Stereotyped response to a stimulus
The performance of the behavior satisfies the animal’s “appetite”, the consumption of food satisfies a hunger
SEE IMAGE 64
Benefits of understanding motivation?
> Use motivations when training
> Knowing existing motivations can help
to:
- Facilitate desired behaviour
- Minimise undesired behaviour
Wallace Craig: Structure of motivated behaviour?
APPETITIVE:
Various initial motor patterns that bring the animal into a situation where it was likely to encounter a “stimulus”
(As if the animal had an “appetite for the stimulus”)
Phase I: No evidence of “stimulus” (e.g. prey): non-directed
Phase II: Stimulus detected (e.g. sight of prey), eventually capturing prey/ finding food: – directed
Phase III: Consummatory (killing prey, eating)
Phase IV: “Satiation” (=condition of being full to or beyond satisfaction)
CONSUMMATORY:
Stereotyped response to a stimulus
(The performance of the behaviour satisfies the animal’s “appetite”, e.g. the consumption of food satisfies a hunger)
SEE IMAGE 64
Which theory of motivation replaces previous explanations and why?
Often physiological causes for behaviour BUT precise relationship usually not known- can not assume particular physiological basis for motivation itself
= No direct, linear relationship between motivational state and behaviour
“State-space-approach” as a modern concept of motivation replaces homeostatic model
Homeostasis model of motivation?
Weakness of this model?
Homeostasis (Walter Cannon 1932):
“The coordinated physiological processes which maintain most of the steady states in the organism are so complex and so peculiar to living beings – involving, as they may, the brain and nerves, the heart, lungs, kidneys and spleen, all working cooperatively – that I have suggest a special designation for these states, homeostasis.”
BUT
- Homeostasis is not always a simple feedback process,does not simply imply constancy of the internal environment
- Feeding and drinking occur often in anticipation of physiological changes: Feedforward behaviour occurs, for example, drinking in rats and pigeons before starting to feed or in anticipation of thermally induced dehydration
Motivated behaviour: State space approach (McFarland)?
- Combined physiological and perceptual state (in the brain)= motivational state of the animal (= point in a motivational space)
- Not direct relationship between motivational state and behaviour
- Combines assumptions of homeostatic models with an explicitly functional approach to regulatory systems
Physiological impacts on behaviour BUT the relationship is not known
State-space models (McFarland and Sibly, 1975) represent an animal’s motivational state as an n-dimensional vector resulting from the interaction between internal and external factors (NOTE: motivation is affected by internal and external factors)
SEE IMAGE 65
Hunger as an example for motivational space- The hunger state exists within a
particular motivational space. Can break down hunger into what the hunger is for (i.e. fat/protein etc)
Set-point theory for ingestive behaviour (hunger)?
BUT
How does this explain obesity?
(Body can monitor blood glucose/body fat level)
Set-point theory:
Idea of homeostatic, negative feedback system regulating feeding
Two set points being regulated: Blood glucose (short-term regulation) body fat (long-term regulation)
Weakness of this= how can set point theory explain obesity?
Answer=
A settling point is a stable state caused by a balance of opposing forces, but without any setpoint or error detection (Regulated but at a higher point- set-point changes)
Brain concepts of motivation: The hypothalamic center model of Stellar?
Brain concepts of motivation: Areas involved in stimulating areas for eating in hypothalamus?
Potential consequences of lesion into hypothalamus?
Relationship between homeostatic and reward pathways?
Environment and mind against metabolic homeostasis?
SEE IMAGE 66
SEE IMAGE 67
Lesion into hypothalamus (effectively destroying it)= weight loss
SEE IMAGE 68
Reward pathway- wanting/liking something. In parallel with homeostatic pathway
Homeostatic mechanisms can be over-ridden by other mechanisms (e.g. reward pathway)
SEE IMAGE 69
SEE IMAGE 70
Explanation: Schematic flow diagram showing homeostatic regulatory system on left (dotted lines) and nonhomeostatic factors contributing to food intake and energy balance on right. The homeostatic regulatory system uses various short- and long-term feedback signals (e.g., leptin, CCK, and ghrelin) acting mainly on the brain to initiate adaptive behavioral, autonomic, and endocrine responses.
Labradors and appetite?
A Deletion in the Canine POMC Gene Is Associated with Weight and Appetite in Obesity-Prone Labrador Retriever Dogs
Motivation and emotion:
- ) POSITIVE emotions?
- ) NEGATIVE emotions?
NOTE: emotions can bring a stochastic element to motivated
behaviour
1.) POSITIVE emotions (approach):
> Related to “active” motivation- Facilitation of motivated behaviour
> Unrelated to “active” motivation
Interference with motivated behaviour (–> switch to other motivation?)
- ) NEGATIVE emotions
(aversions) :
> Related to “active” motivation
Interference with motivated behaviour
(–> switch to other motivation?)
> Unrelated to “active” motivation
Interference with motivated behaviour
(–> switch to other motivation?)
SUMMARY:
Positive emotions can facilitate OR interfere with motivational behaviour (e.g. interfere: another positive distraction may stop it from being motivated from the first, such as chasing a cat appearing more desirable than eating their food)
Drive and motivation?
It would seem that there are clear “drives” that motivate an organism to satisfy physiological needs. Such “drives” are referred to as homeostatic motivation. Drive-reduction theory attempted to quantify these drives
However, these do not explain all motivated behaviour. A number of non-homeostatic motivations exist and these may serve the purpose of maintaining arousal levels and filling time
Reflex arc?
SEE IMAGE 71 (2 parts)
Allows for automation of actions (action-reaction)
Basic reflex to maintain limbs in the same/correct posture
If you set muscle at one length then the muscles will try and maintain this length
Innervation of the reflex arc
1.) Type Ia fibres:
- Tend to form:
monosynaptic connection with alpha motor neurones
- (primary) Originate from:
annulospiral endings
-Produce impulses proportional to:
the rate of change of length of the intrafusal muscle fibres
- Produce: dynamic information
1.) Type II fibres:
- Tend to form:
polysynaptic responses
(Polysynaptic responses= more controlled/ coordinated BUT slower)
- (primary) Originate from:
flower spray nerve endings
-Produce impulses proportional to:
the tension within the intrafusal muscle fibres responding to change in length
- Produce: static information
NOTE: Predictable from size and speed of transmission of information
SEE IMAGE 72
What is proprioception?
= perception or awareness of the position and movement of the body
What is proprioception?
= System responsible for detecting changes in the position of the trunk, limbs and head
- Kinaesthesia
- Sense of joint position and movement
General principles of spinal cord organisation?
> Similar fibres arranged in tracts
> Afferent vs efferent regions
- SEE IMAGE 73
> Somatotopic organisation - Spatial orientation from receptor sites retained within fibre orientation within the tracts - Eg gracile and cuneate fasiculi - SEE IMAGE 74 (add in slide 16)
> Fibres run in white matter
- Fibres rarely run for more than 1 segment in grey matter
> Poly-synaptic
- Most pathways are polysynaptic- more than one neurone involved
- No afferent fibres reach the peripheral nerve without synapsing at least once
- Sensory fibres: all sensory information synapses at least once prior to projection into the cerebral cortex or cerebellum
> Decussation
> Sensible nomenclature
Species variations
What is proprioception?
= System responsible for detecting changes in the position of the trunk, limbs and head
- Kinaesthesia
- Sense of joint position and movement
- Can be conscious OR unconscious
General principles of spinal cord organisation?
> Similar fibres arranged in tracts
> Afferent vs efferent regions
- SEE IMAGE 73
> Somatotopic organisation - Spatial orientation from receptor sites retained within fibre orientation within the tracts - Eg gracile and cuneate fasiculi - SEE IMAGE 74 (add in slide 16)
> Fibres run in white matter
- Fibres rarely run for more than 1 segment in grey matter
> Poly-synaptic
- Most pathways are polysynaptic- more than one neurone involved
- No afferent fibres reach the peripheral nerve without synapsing at least once
- Sensory fibres: all sensory information synapses at least once prior to projection into the cerebral cortex or cerebellum
SEE IMAGE 75
> Decussation
> Sensible nomenclature
> Species variations
Reflex arc:
Receptors?
Muscle spindles Golgi tendon organs Joint capsule Ligaments Skin
Impact of cruciate injury/joint replacement on procprioception?
= loss of proprioception
General principles of spinal cord organisation?
> Similar fibres arranged in tracts
> Afferent vs efferent regions
- SEE IMAGE 73
> Somatotopic organisation - Spatial orientation from receptor sites retained within fibre orientation within the tracts - Eg gracile and cuneate fasiculi - SEE IMAGE 74 (add in slide 16)
> Fibres run in white matter
- Fibres rarely run for more than 1 segment in grey matter
> Poly-synaptic
- Most pathways are polysynaptic- more than one neurone involved
- No afferent fibres reach the peripheral nerve without synapsing at least once
- Sensory fibres: all sensory information synapses at least once prior to projection into the cerebral cortex or cerebellum
SEE IMAGE 75
(ALSO see other slides for explanation)
> Decussation
- Tracts passing into the cortex decussate at some stage to project contralaterally (opposite side of body)
- Tracts passing to the cerebellum tend to project ipselaterally (same side of body)
BUT everything that goes to consciousness cross over, things not to consciousness generally don’t
NOTE: some may not follow these roles
> Sensible nomenclature - Examples: * Spinothalamic= spine to thalamus * Spinocerebellar= spine to cerebellum * Rubrospinal= red nucleus (in brain) to spine
> Species variations
- Relative prominence of pyramidal system:
* Man= 30% of total white matter
* Dog= 10% of total white matter
- Sheep pyramidal system does not project beyond C4 segment
- Horse pyramidal system stops at C1
(Pyramidal system allows fine motor control of many muscles at the same time (horse doesn’t really need to move as it only has 1 stump of a digit, dogs have slightly more to be able to move digits))
NOTE: paw placement involves pyramidal AND extrapyramidal
Difference between conscious and unconscious proprioception?
Projection to cerebellum= unconscious
Projection to somesthetic cortex= conscious
Decussation of tracts: everything that goes to consciousness cross over, things not to consciousness generally don’t
Path of signals to coordinate proprioception- conscious and unconscious?
TO COMPLETE slide 29
Explain the Vestibulospinal tract?
> Does not obey all rules:
- Does not decussate
- Projects mainly to alpha motor neurones
- Strongly facilitatory (unlike most things that are inhibitory)
Afferent (sensory) pathways?
Touch, pressure – pass with conscious proprioception in the dorsal funiculus
Pain, temperature and touch – spinothalamic tract
What is the spinothalamic tract?
- Bilateral projection in domestic species
- Primary sensory fibre synapses in multiple segments
- Small fibres (some are unmyelinated)
- Species variation
SEE IMAGE 76
Basic principles of spinal radiography?
- Need atleast 2 orthogonal views
- Need anaesthesia/ at least heavy sedation to allow good positioning
- Need to avoid/consider parallax errors
- Appropriate exposure for region of interest
What are orthogonal views?
2 views at right angles to each other
e.g. Lateral AND ventrodorsal
Spinal cord imaging:
Ventrodorsal or dorsoventral?
Usually VD= better Because: - Vertebrae are closer to imaging plate - No movement blur from movement of chest cavity during respiration - Less magnification
NOTE: always remember marker (Lateral= cranial on left of screen, VD/DV= left of dog on right of screen- e.g. standing up and facing you)
Spinal radiography:
How should the spine be positioned relative to the plate and why?
SHOULD BE:
Straight and parallel to x-ray plate
BECAUSE:
X-rays all parallel to each other and so spine parallel to x-ray plate to allow beams to pass through intervertebral discs parallel to each other (allows comparison of discs)
SHOULD NOT BE:
a.) At oblique angle
BECAUSE:
fewer x-ray beams pass through the intervertebral discs
b.) Kyphosis/scoliosis
BECAUSE:
different information from spine at different points
SEE IMAGE 77 (3 parts)
Basic principles of spinal radiography?
- Need atleast 2 orthogonal views
SEE IMAGE 78 (2 parts) - Need anaesthesia/ at least heavy sedation to allow good positioning
- Need to avoid/consider parallax errors
SEE IMAGE 77 (3 parts) - Appropriate exposure for region of interest
What are orthogonal views?
2 views at right angles to each other
e.g. Lateral AND ventrodorsal
Spinal radiography:
How should the spine be positioned relative to the plate and why?
SHOULD BE:
Straight and parallel to x-ray plate
BECAUSE:
X-rays all parallel to each other and so spine parallel to x-ray plate to allow beams to pass through intervertebral discs parallel to each other (allows comparison of discs)
SHOULD NOT BE:
a.) At oblique angle
BECAUSE:
fewer x-ray beams pass through the intervertebral discs
b.) Kyphosis/scoliosis
BECAUSE:
different information from spine at different points
SEE IMAGE 77 (3 parts)
Spinal imaging:
Padding=
Why and how is padding used?
- Most dogs have wide pelvis/thorax and relatively wide head
- Spine sitting between and usually sags down- SO padding used
- Enables spine to be straightened and line up
- Under head/neck/pelvis/tail (species-variation)
SEE IMAGE 79 (2 parts)
Spinal cord imaging:
Ventrodorsal or dorsoventral?
Usually VD= better Because: - Vertebrae are closer to imaging plate - No movement blur from movement of chest cavity during respiration - Less magnification
NOTE: always remember marker (Lateral= cranial on left on screen, VD/DV= left of dog on right of screen- e.g. standing up and facing you)
Spinal imaging:
Should a radiograph of entire body of small body be taken to investigate the spine?
NOT IDEAL
X-rays generated from tube head as diverging beam (NOT as parallel x-rays)
Means: parallax error at each edge (difficult to interpret spaces between intervertebral discs) so only good quality image at centre of beam
Plate must be centred on x-ray beam and compare information round this centre- may need to take several images
SEE IMAGE 80
SEE IMAGE 81
Spinal radiography:
Axial rotation?
= PREVENT AXIAL ROTATION
Must be perpendicular
Different structures will over-lie each other (oblique view)
NOTE oblique view is sometimes needed
Lateral view: true lateral NOT rotated (difficult to compare 2 sides of vertebrae)
Padding used (stifle and chest- ensure line between sternum an dorsal spinous processes is parallel to x-ray table)
SEE IMAGE 82
What are dynamic views and why are they used?
- Animal must be still (static view) BUT sometimes take dynamic
- May be used in cases of suspected instability
Flexed endotracheal tube on R and head flexed down by 90 degrees
Moving animal creates different imamge
Opening up joint betwee axis and atals (atlantoaxial- peg)
Flexion view shows atlanto-axial instability_ BUT DO NOT force animal too much under anaesthetic as could paralyse the animal
Dynamic views- disarticulation, discolcation, subluxation in atlantoaxial joint in toy breeds
Open up intervertebral foramina between C1 and C2 by using R image (poen up)
BUT care not to traumatise spine using dynamic views (beware of spinal fracture)
Decide if fracture using catogram/dogogram before manipulating
SEE IMAGE 83
Spinal radiography:
Axial rotation?
How to check for axial rotation/lack of?
How to prevent axial rotation?
= PREVENT AXIAL ROTATION
> Checking for lack of axial rotation:
Perpendicular
Truly un-rotated= 2 rib heads overlying and 2 articular facet joints overlying each other (oblique view)
NOTE oblique view is sometimes needed
LOOK FOR: differences in space (e.g. intervertebral discs)- discs vary in size along spine so compare with discs either side of it
Preventing axial rotation:
Padding used- stifle and chest
Ensure line between sternum and dorsal spinous processes is parallel to x-ray table
SEE IMAGE 82
Myelography:
Injection sites for contrast?
1.) CISTERNAL puncture
Flex head down and insert needle between skull and C1 and inject contrast medium which flows down along cord
SEE IMAGE 84
2.) LUMBAR puncture
Inject contrast agent (needle sitting under spinal cord)White= contrast and has highlighted spinal cord9
Between L5 and L6 needle through interarcuate space, contrast mdium injected into subarachnoic space
Medium outlines spinal cord
SEE IMAGE 85
Contrast runs up and down around cord and outlines spinal cord
Can look at shape of spinal cord
Tramlines outline spinal cord to see changes
What are dynamic views?
Why are they used?
Precautions taken when using them?
- Animal must be still (static view) BUT moving animal creates different image
- May be used in cases of suspected instability
Example:
Flexed head downwards by 90 degrees- opens up intervertebral formaina between C1 and C2 (atlantoaxial joint) to show instability of joint
BUT
DO NOT force animal too much under anaesthetic as could paralyse the animal
NOTE: Beware of spinal fractures: use catogram/dogogram to check for fractures before manipulating
Can identify: disarticulation, disclocation, subluxation in atlantoaxial joint (especially in toy breeds)
SEE IMAGE 83 (2 parts)
Spinal imaging:
Explain myelography?
How does it correct a weakness of radiography?
- Contrast opacification of the sub-arachnoid space
- Non-ionic iodinated contrast medium (iodine-based contrast medium used for radiography)
- Put contrast into subarachnoid space (space between dura mater and spinal cord around spinal cord ) at the occipito-atlantal junction or caudal lumbar
Weakness of radiography:
Doesn’t show soft tissue associated with spinal cord and so may not allow diagnosis
Myelography:
Injection sites for contrast?
1.) CISTERNAL puncture
Flex head down and insert needle between skull and C1 and inject contrast medium which flows down along cord
SEE IMAGE 84
2.) LUMBAR puncture Inject contrast agent Between L5 and L6 needle through interarcuate space, contrast mdium injected into subarachnoic space Medium outlines spinal cord SEE IMAGE 85
Contrast runs up/down around cord and outlines spinal cord as tramlines to show shape of it
Myelography;
Sites for lesions (shown by contrast)?
Lesion outside dura mater?
Lesion within CSF space?
How do each of these lesions differ from normal when contrast is injected?
1.) Intramedullary (inside spinal cord)
2.) Extradural (outside dura)
3.) Intradural/ extramedullary (Within dura mater BUT not inside cord)
SEE IMAGE 86
Opacified space around cord so can see lesion within cord make it swell
Lesion outside dura mater= distorts/compresses column
Lesion within CSF space= compress spinal cord AND occlude space around the outside
> Normal= tramlines
Extra-dural (outside dura)= contrast column comes up and deviates around material
Intradural/ extramedullary (within dura but outside spinal cord)= contrast line goes around mass
Intra-medullary (within spinal cord)= spinal cord swells and lose contrast columns around each side (contrast may stop at lesion as it can’t go any further)
SEE IMAGE 87
What is MRI generally used for?
Superior soft tissue detail
MRI best for soft tissue (most of NS)
Alternate contrast studies to myelography?
Weakness of myelography?
What are all of these now generally surpassed by?
1.) Discography=
Direct injection into the intervertebral disc
2.) Epidurography
Opacification of the epidural space
> Weakness of myelography:
- Difficult to do- contrast in right place
- Difficult to interpret
- Abnormal material into subarachnoid space- can be fatal
All now generally surpassed by MRI
What is CT and when is it used?
CT/myelography vs MRI?
= Computed tomography
- Same information as routine radiography but slice detail (can use CT for everything radiography is used for)
- Can be combined with myelography to view details of spinal cord
> CT/myelography vs MRI
+ CT= useful where MRI not feasible (e.g. if metal implants present next to spine)
+ CT= better for viewing osseous structures
- CT and myelography= potentially fatal (unlike MRI)
What can be used in addition to CT to image the spinal cord in more detail?
CT and myelography can be combined= more info about spinal cord than CT by itself
Myelography allows space around spinal cord to be opacified
SEE IMAGE 88 (2 parts)
What is MRI generally used for?
Superior soft tissue detail (most of NS)
MRI conventions?
- Display conventions as for radiography
- Labelling for orientation produced at the time of imaging
MRI:
T1 vs T2?
SEE IMAGE 89
Bone Fat Fluid Soft tissue Gadolinium Pathology SEE IMAGE 90
MRI:
Explain the novel sequences and why they are used?
NOTE: 2 most commonly used outside of T1 and T2
- ) FLAIR=
- Suppresses signal from CSF (think fl is for fluid)
- Useful for lesions adjacent to ventricular structures (suppress signal from fluid within ventricles to see lesions)
- Helps to show up lesions in brain - ) STIR
- Suppresses fat signal
- Nerves in brachial plexus are surrounded by fat so STIR used to suppress fat signals so nerves can be visualised
What positive contrast agent is used in MRI and how does it work?
= Gadolinium
- Effectively high signal (white) on T1 weighted images
- Inject intravenously and goes around venous system (lights up venous blood on T1 images)
- Excluded by the blood brain barrier SO no change in brain)
- High vasculatory= goes white after contrast BUT no change in brain due to blood brain barrier SO if it goes white in brain then shows high vasculatory with no blood brain barrier
NOTE:
Radiography/CT= Looking where there isn’t contrast BUT gadolinium= looking for where there is contrast
What can MRI be used to detail?
DETAIL:
> Site of spinal cord compression
- SEE IMAGE 91
> AND significance of compression
- Spinal cord compressed at 2 sites (2 bulging discs) BUT white over 1 and not the other- T2 and so shows significance of 1 of these compression- oedema within spinal cord where is it white
- SEE IMAGE 92
> Lateralisation (cross-section)
- Need to know which side to make incision for surgery to remove material
- SEE IMAGE 93 (3 parts)
> Fibrocartilagenous embolisation
- High signal predominantly on LHS of spinal cord, discs adjacent to it are fairly normal
- Stroke within spinal cord
- Myelography would only show slight swelling of spinal cord
- SEE IMAGE 94 (2 parts)
> Trauma
- SEE IMAGE 95 (2 parts)
> Neoplasia
- Seen after contrast added, could not see on radiograph
SEE IMAGE 96 (2 parts)
-Tumour on Myelography vs MR (much easier on MR as myelogram is hard to distinguish between tumour and slipped disc in example)
SEE IMAGE 97 (2 parts)
SEE IMAGE 98
> Intraparenchymal neoplasia
- Tumour within spinal cord- MRI allows this to be localised
- Outlined by oedema all around it
- SEE IMAGE 99 (3 parts)
> Discospondylitis
- Infection (abscess) within disc
- Changes within bone also seen (not just soft tissue)
- SEE IMAGE 100 (2 parts)
> Transitional vertebra
- SEE IMAGE 101 (2 parts)
> Midline compression
- Different sites of compression
- Compression of spinal cord- shown by MRI
- SEE IMAGE 102 (4 parts)
> Asymptomatic
- Compression of spinal cord
- SEE IMAGE 103 (2 parts)
Spinal radiography:
What features of vertebrae can be identified on a radiograph?
Intervertebral disc space
Body
Transverse processes/ ribs
Dorsal spinous processes
Articular facettes
Spinal canal
Intervertebral foramina
Area surrounding vertebrae
(NOTE: be SYSTEMATIC= if lame on R forelimb, examine this leg last on a radiograph)
Spinal radiography:
What features of vertebrae can be identified on a radiograph?
Intervertebral disc space
Body
Transverse processes/ ribs
Dorsal spinous processes
Articular facettes
Spinal canal
Intervertebral foramina
Area surrounding vertebrae
(NOTE: be SYSTEMATIC= if lame on R forelimb, examine this leg last on a radiograph)
Ventral spinal/basilar artery?
Ventral spinal artery?
SEE IMAGE 118 (2 parts)
Explain blood supply TO the brain?
> Species variation- clinical relevance e.g. for slaughter
> Ventral
Explain blood supply TO the brain?
> Species variation- clinical relevance e.g. for slaughter
Arterial supply= ventral to brain
> Supplied by 5 main pairs of vessels
1.) ROSTRAL CEREBRAL ARTERIES=
supply the medial aspect of the cerebral hemispheres
2.) MIDDLE CEREBRAL ARTERIES=
supply the lateral and ventrolateral aspects of the cerebral hemispheres
3.) CAUDAL CEREBRAL ARTERIES=
supply the occipital lobes
4.) ROSTRAL CEREBELLAR ARTERIES=
supply the rostral aspects of the cerebellum
5.) CAUDAL CEREBELLAR ARTERIES=
supply the caudal and lateral aspects of the cerebellum
NOTE: all 5 pairs connect by/originate from the circle of WIllis (ventral to brain)
Explain the Circle of Willis?
- Ventral to brain
- Connect arteries supplying brain
- Structure:
- Rostral cerebral artery
- Middle cerebral artery
- Caudal cerebral artery
- Rostral cerebellar A
- Caudal cerebellar A, coming off- Basilar A
SEE IMAGE 119
Explain the Circle of Willis:
- Position?
- Function?
- Structure- blood going away FROM it
- Direction of blood flow?
- Structure- blood SUPPLYING it
- Ventral to brain
- Underneath hypothalamus
- Around pituitary gland
SEE IMAGE 119 - Connect arteries supplying brain
- Structure (blood going away from it):
- Rostral cerebral artery
- Middle cerebral artery
- Caudal cerebral artery
- Rostral cerebellar A
- Caudal cerebellar A, coming off- Basilar A
SEE IMAGE 120 - Direction of blood flow:
- From high to low pressure- either way around the circle
- Different species= different pressures= blood flows in different directions
- NOTE: if high pressure on left and low on right, blood flows on top clockwise, along the bottom anticlockwise
- Structure (blood supplying it):
- Internal carotid A (2)- comes from common carotid, which branches into ext. and int. carotid
- Basilar A- comes from spinal cord, changes name to ventral spinal A as it reach spinal cord
Explain origin of basilar artery?
Basilar artery= supply from spinal cord
As it reaches spinal cord: changes name to ventral spinal artery
Ventral spinal artery: supplied segmentally by vertebral artery- comes up and at every intervertebral foramina, artery comes in and connects to ventral spinal artery
SEE IMAGE 121
Vertebral artery: branch of subclavian artery, runs through vertebral foramina of C1 –C6 (close to bones), dives in at C6/C7 and runs underneath all of these muscles
Clinical implications of species variation of arterial supply to the brain?
Ritual slaughter – transection of external carotid artery and jugular veins
How long does it take for loss of consciousness due to reduced circulation?
May take up to 10 seconds for standing cattle to fall.
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Iliac thrombosis?
Thromboembolic disease affecting the descending aorta/iliac vessels Pain Pallour Paralysis Pulselessness
Clot that occludes descending aorta and … (ECHO)
Easy to diagnose (cold, no pulse and pain in hindlegs)
ECHO
Thrombus (clot) within descending aorta or iliac vessels
Thrombus in descending aorta: Back end of animal= avascular (pain, pallor, paralysis, no pulse in back legs). Back legs normal except no pulse in back legs
Iliac thrombosis (rare In dogs, common in cats)
Fibrocartilagenous embolisation(rare In cats, common in dogs)
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Venous drainage of spinal cord?
Slide 32, 33
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Slide 35
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Slide 39
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Slide 43
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Vasc.
Clinical implications of species variation of arterial supply to the brain?
Ritual slaughter – transection of external carotid artery and jugular veins
May take up to 10 seconds for standing cattle to fall due to reduced circulation
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Fibrocartilagenous embolisation?
SEE IMAGE 131
- Stroke within spinal cord
- Occurs at level of ascending artery OR after it has branched- to 1 side or the other
- Block blood supply to ascending artery= entire centre OR blocked after branching= only 1 side affected (oedema seen in LHS)
- Dog presents: hemiparesis if on one side
- Quick onset
Iliac thrombosis?
- Thromboembolic disease affecting the descending aorta/iliac vessels
- Pain
- Pallour
- Paralysis
- Pulselessness
- Easy to diagnose (cold, no pulse and pain in hindlegs)
- Thrombus (clot) within descending aorta or iliac vessels
- Thrombus in descending aorta: Back end of animal= avascular (pain, pallor, paralysis, no pulse in back legs). Back legs normal except no pulse in back legs
NOTE: Iliac thrombosis (rare In dogs, common in cats) Fibrocartilagenous embolisation (rare In cats, common in dogs)
Venous drainage of brain?
Communicating system of sinuses (instead of veins) > Sinuses: - Thin-walled - Poorly-developed/ absent valves - Bigger than veins
Three groups of sinuses:
Dorsal
Ventral
Connecting
(Connecting sinuses: join the other 2 groups together)
> Brachial plexus:
- Nerves forming the plexus?
- Location of the plexus?
- Nerves leaving the plexus? Nerves to the extrinsic muscles?
SEE IMAGE slide 9
Brachial plexus
Nerve supply from C6 to T2 is generally correct for most animals but natural variation means that this may shift in some people (i.e. may run C5 to T1 in some animals)
Each muscle is composed of series of segments embryologically and so segmental nerve supply (e.g. embryological form of muscle may have 2 segments and so require double innervation- 1 for each segment)- nerve supply to each embryological segment of a muscle
- The nerves forming the plexus=
C6-T2 (ventral rami) - Location=
in axilla
So in close contact with other axillary structures e.g. axillary a. v. and axillary lymph nodes - Main nerves leaving the plexus=
Nerves to extrinsic mm.
Nerves to intrinsic mm.
Extrinsic muscles keep limb attached to thorax
Synsarcosis= purely muscular attachment at a joint
Intrinsic muscles= protractors and retractors
Think of functional group of muscles as this then shows what the nerve supply is
Pectoral nerve supplies:
Pectoral group
Thoracodorsal nerve supplies:
Latissimus dorsi
Long thoracic nerve supplies:
Serratus ventralis thoracis
Lateral thoracic nerve supplies:
Cutaneous trunci
Several pectoral nerves represent several segments
Underlining= to help remember this table
Cutaneous trunci= makes the skin twitch (e.g. to get flies off an animal)- also used neurologically by vets, press gently with ballpoint pen and note reflex response
Suprascapular n. Subscapular nn. Axillary n. Radial n. Musculocutaneous n. Median n. Ulnar n.
Think of medan and ulnar nerves as same nerve, innervate very similar muscles BUT with different origins
(uLna = Lateral)
Venous drainage of the brain:
Describe the dorsal sinuses?
Rostral to caudal=
> Dorsal sagittal sinus:
- In falx cerebri centrally between cerebral cortices then caudally in skull
> Straight sinus:
- Drains great cerebral vein
> 2 transverse sinuses:
- Drains dorsal sagittal sinus
Caudal portion of dorsal sagittal sinus joins up with straight sinus and goes into skull. 2 transverse sinuses run down either side of skull (within skull) at level of junction between cerebellum and cerebral cortices. Caudally= within skull
SEE IMAGE 125
Venous drainage of the brain:
Describe the ventral sinuses?
> Dorsal and ventral petrosal sinuses
- Connect caudally with transverse sinus
> Cavernous sinus - A median connecting pair of sinuses - Sits around pituitary gland - Inside sinus= retus mirabile for arteriole supply, around outside of this= Circle of Willis SEE IMAGE 126
Venous drainage of the brain:
Describe the connecting sinuses?
- Join things up between cerebral and spinal sinuses
- Extracranial connection to maxillary vein- everything drains caudally into maxillary vein
Venous drainage of the brain:
Role of maxillary vein
Dorsal and ventral sinuses run caudally
Join together and drain into maxillary vein
SEE IMAGE 127
How does the venous drainage leave the brain?
- High pressure to low pressure
- Either:
a. ) Connect and leave via maxillary vein
b. ) Go along spinal cord as venous ventral spinal sinuses
Venous drainage of the brain:
Summary diagram?
SEE IMAGE 128
Clinical relevance:
Are you able to ligate the sagittal sinus?
Ligation of sagittal sinus= leads to fatal cerebral oedema
BUT
can ligate 1 transverse sinus (have to operate inside venous sinus and damage in this area could cause large amounts of bleeding)
NOTE: Surgical approach to the pituitary is risky
What is the blood brain barrier?
= selective barrier for exchange of substances between circulating blood (arterial and venous blood) and the parenchyma of the nervous system
Located at capillary level
Not all of brain has intact blood brain barrier
Capillary wall structure of the blood brain barrier?
(Bottom to top) > Lumen of vessel > Endothlium - Tight junctions between endothelial cells (prevent paracellular flux), overlapping endothelium > Basement membrane - Thick > Astrocytes - Put down little processes, astrocytes line whole capillary system within brain > Extracellular space SEE IMAGE 129 SEE IMAGE 132
NOTE: very tight, NOT leaky as elsewhere in body
Which substances are able to/NOT able to cross the blood brain barrier?
Methods of crossing barrier?
> Able to cross:
- Sometimes smaller molecules
- Lipid soluble
> NOT able to cross:
- Large molecules
- Glucose (requires active transport to pass into extracellular fluid/CSF)
> Methods:
- Active transport
- Pinocytosis
- P-glycoprotein pumps actively eject undesired substances.
Which parts of the brain do not have intact blood brain barrier and why?
Not all of the brain has an intact blood brain barrier
- Pituitary gland=
Large organic molecules produced here need to get out into circulation - Choroid Plexus=
Produces CSF
NOTE: both become more white/brighter after staining
SEE IMAGE 130 (6 parts)
Clinical significance of blood brain barrier?
Separation of brain from blood
Large macromolecules and non-lipid soluble drugs will be excluded from the brain
(Barrier to pathogens BUT also barrier to certain drugs used)
Role of the Choroid Plexus?
Produces cerebrospinal fluid
Free
Free
Free
Free
Vascular system SLIDES TO COMPLETE: 13 14 15 16 17 18 19 20 21 22 24 25 26 32 33
Complete these
Neuronal diseases and their causes?
a.) Neuronal diseases:
> Meningitis
= Inflammation of the meninges
> Encephalitis
= Inflammation of the brain
> Meningoencephalitis
= Simultaneous inflammation of the meninges AND the brain
b.) Causes:
Bacteria, viruses, fungi, protozoa, Rickettsia, parasite migrations, chemical agents, and idiopathic or immune-mediated diseases.
What does idiopathic mean?
Disease/condition arising spontaneously or with unknown cause
How can microbial pathogens damage the nervous system?
- ) Invasion and replication in the tissues:
- Direct invasion of peripheral nerves
- From adjacent structures such as from the meninges
- From the blood Haematogenous - ) Inducing an immune response:
- Inflammation of CNS
- Damage caused by local inflammation to the CNS
- Auto-immune response. Human example Guillain–Barré syndrome due to Campylobacter - ) Releasing toxins:
- Block signalling
- Damage specific cells
Neuronal diseases and their causes?
Explain their prevalence?
a.) Neuronal diseases:
> Meningitis
= Inflammation of the meninges
> Encephalitis
= Inflammation of the brain
> Meningoencephalitis
= Simultaneous inflammation of the meninges AND the brain
b.) Causes:
Bacteria, viruses, fungi, protozoa, Rickettsia, parasite migrations, chemical agents, and idiopathic or immune-mediated diseases.
- Prevalence
Fairly uncommon
BBB: nerous tissue is enclosed and CNS is maintained sterile
To cause disease the organisms, toxins need to access the CNS
NOTE: For antibiotics to be effective they need to reach the right concentration in the CNS. Therefore selection on a drug with the relevant destruction can be very important.
Pathogen spread and access to the CNS?
Entry to body -> Spread -> a.) Neurotropic (from peripheral nerves - nerve to nerve)
OR
b.) Neural Abscess
(from a septic focus)
OR
c.) Haematogenous
(via blood)
COMPLETE THIS SLIDE 6
Function of cutaneous trunci?
Cutaneous trunci= Makes the skin twitch (e.g. to get flies off an animal)- also used neurologically by vets, press gently with ballpoint pen and note reflex response
Why does haematogenous spread pose a risk to CNS?
Infectious agents in blood can get deep into tissue
Sticks to blood vessel wall and gets into neurological tissue
How can the blood brain barrier be breached?
NEED TO COMPLETE THIS- ECHO
a. ) Transcellular
- Pathogens bind host cells and invade through the cell (i.e. binds to membrane, uptake into cell)
- Passive or active on the part of the pathogen
- Transcellular common pathogen examples:
* Bacterial= Streptococci, Listeria sp.
* Fungal= Candida (yeast), Cryptococcus (dia-morphihic fungus)
b. ) Paracellular
- Tight junctions dramatically change or new routes open
- Increased pinocytic activity leading to trans-endothlial channels formation or tight junction function can be broken
- Paracellular common pathogen examples:
* Nipah virus (Malaysia-Porcine respiratory and encephalitis syndrome).
* Lyme disease (bacterial) - Borrelia burgodorferi a spirochete.
c.) Intracellular within leucocytes (Torjan horse)
- Requires primary infection
- Spreads where cell goes
- May be refractive to antibody once established (if it spreads cell-to-cell)
- Intracellular transmigration pathogen examples:
Examples intracellular transmigration:
* SIV/ HIV
* Canine distemper
NOTE: In addition to these breaches, overgrowth and necrosis can cause indiscriminate damage to tissue
NOTE: Some organisms can also enter by different routes
SLIDE 13
COMPLETE
Pathogens can trigger inflammation: what are the consequences of this?
NOTE: Non specific inflammation can be caused by attracted leucocytes
Impacts neuronal tissue (can be indirect: pressure from attracted cells)
Clinical signs of CNS infection?
Depression Pyrexia Cervical pain Hyperaesthesia Photophobia Generalized rigidity Seizures Paralysis local and general Ataxia Papilloedema Possible ophthalmic inflammation. Systemic signs. Septic shock and brachycardia.
Try to localise, can be associated with many things
Look at COMBINATION of clinical signs
How can microbiology of CNS be assessed?
Joint-tap- take fluid from joints or CNS
CNS should be maintained sterile- pathogens need to enter CNS to cause dosease
Infection indicators?
Slide 17
Example of pathogens which can infect the CNS?
General specific infection: bacteria in blood impacts across the body
Spread of an organism in blood that starts in sepctic foci in nervous tissue
Example of pathogens which can infect the CNS?
General specific infection: bacteria in blood impacts across the body
Spread of an organism in blood that starts in septic foci in nervous tissue
Examples of pathogens which can infect the CNS?
> Canine distemper
(viraemia/haematogenous/broad infection)
> Listeria
(neurotropic spread-bacterial)
> Rabies
(neurotropic spread-viral)
NOTE: need to know organism, basic details of infection
What is Canine Distemper Virus?
- Infectious disease of dogs and other carnivores
- Pantropic – generalised infection in many organ systems as the receptors are common on many cells
- Spread: close contact or by aerosols infect via URT then go systemic
How is canine distemper virus spread?
- Primary infection site= mucosal surface
- Virus replicates in URT
- Spreads to tonsils and bronchial lymph nodes
- Viral replication leads to lymphocytolysis / leukopenia- Allowing viraemia
- Dissemination to other sites: including GIT, Urinary, and CNS tissue (can cross blood brain barrier)
- NOTE: Can spread neuron to neuron without cytolysis
SEE IMAGE 133
How is Listeria spread?
Listeria attaches to and enters mammalian cells
This attachment induces phagocytosis
Listeria release themselves from the vacuoles with listeriolysin
Move in cells and between cells by nucleating actin
Hence they can spread is neurotropic (nerve cell to nerve cell)
Listeria in ruminants?
Listeria found in the environment.
Outbreaks tend to be seasonal.
They can an replicate in poor quality silages pH above 5.5.
In good quality silage multiplication is inhibited by acid pH
In ruminants may present as encephalitis, abortion, septicaemia, or endophthalmitis
One source of susceptibility is decreased cell-mediated immunity associated with advanced pregnancy
Listeria:
Clinical signs?
Treatment?
Prevention?
Clinical signs (cattle from ocular infection)
Incubation period of neural Listeriosis ranges from 14 to 40 days.
Dullness, circling and tilting of head facial paralysis.
Unilateral facial paralysis can result in drooling and dropping of eyelids and ears.
Treatment
In early stages with antibiotics
Prevention
Do Not feed poor silage to pregnant ruminants.
Do not feed poor quality silage at all?!
Ensure feed method used reduces ocular contact.
Vaccines do NOT work as the pathogen is intracellular
What is Rabies?
RNA virus
Rod shaped
Enveloped
How is rabies spread?
- Variety of reservoirs (most common animal reservoir= bats)
- Present in infected carnivore’s saliva
- Bite proximal leg
- Virus replicates in muscles
- Virus reaches sensory/motor nerve ends
- Binds acetylcholine receptor (or other sensory end receptors)
- Virus enters distal reaches of nerves and begins second stage of infection
- Neuronal infection with centripetal passive movement within axons
(“retrograde axoplasmic flow”) - Reaches CNS (spinal cord initially)
- Virus reaches limbic system of brain and replicates extensively here (leads to the aberrant behaviour) (“furious rabies”)
- Spread continues clinical replication in cortex (“dumb rabies”)- Cell pathology low, but cells all contain virus.
- Centrifugal spread to periphery: organs, salivary glands where virus buds from cytoplasmic membrane different from nerves
Fungi that can cause neurological infection?
> NOTE: fungal infections of CNS= fairly uncommon in dogs/cats (more common in warm, humid conditions)
> Fungi that can cause neurological infection:
Cryptococcus neoformans (dimorphic yeast) Can infect cats carried by pigeons, normally infects when immuno suppressed.
Primary pathogens:
Histoplasma, Blastomyces (Fungi)
[Do Not Occur in the UK]
Opportunistic invaders:
Aspergillus and Penicillium (fungi) Rare often a consequence of discospondylitis or osteomyelitis.
Extension of nasal aspergillosis through the cribriform plate has been observed.
Clinical signs are dependent on lesion location and are often multi-focal.
Pathogen spread and access to the CNS?
Entry to body -> Spread -> a.) Neurotropic (from peripheral nerves - nerve to nerve) - Intra-axonal modes of spread
OR
b.) Neural Abscess
(from a septic focus)
OR
c.) Haematogenous
(via blood)
- Bacteraemia OR viraemia
SEE IMAGE 134
How can the blood brain barrier be breached?
a. ) Transcellular
- Pathogens bind host cells and invade through the cell (i.e. binds to membrane, uptake into cell)
- Passive or active on the part of the pathogen
- Transcellular common pathogen examples:
* Bacterial= Streptococci, Listeria sp.
* Fungal= Candida (yeast), Cryptococcus (dia-morphihic fungus)
b. ) Paracellular
- Tight junctions dramatically change or new routes open
- Increased pinocytic activity leading to trans-endothlial channels formation or tight junction function can be broken
- Paracellular common pathogen examples:
* Nipah virus (Malaysia-Porcine respiratory and encephalitis syndrome).
* Lyme disease (bacterial) - Borrelia burgodorferi a spirochete.
c.) Intracellular within leucocytes (Torjan horse)
- Requires primary infection
- Pathogen inside cell (e.g. macrophage) and so not recognised by host immune system- spreads where cell goes (i.e. migrates through endothelial layers)
- May be refractive to antibody once established (if it spreads cell-to-cell)
- Intracellular transmigration pathogen examples:
Examples intracellular transmigration:
* SIV/ HIV
* Canine distemper
NOTE: In addition to these breaches, overgrowth and necrosis can cause indiscriminate damage to tissue
NOTE: Some organisms can also enter by different routes
How do viruses cause infection?
How do bacteria cause infection?
> Viruses:
- Have host-cell binding proteins that MUST bind to specific receptors on endothelia to progress
- Example: Distemper uses receptors which are on many different types of cells
> Bacteria:
- Surface proteins (Pili or outer-membrane proeteins, OMPs) increase adhesion of bacteria to cells
- The binding MAY trigger specific invasion mechanisms
- Once inside the cell, the intracellular bacteria require a survival mechanism
Pathogens can trigger inflammation: what are the consequences of this?
NOTE: Non specific inflammation can be caused by attracted leucocytes
Impacts neuronal tissue (can be indirect: pressure from attracted cells)
COMPLETE Infection indicators slide
Slide 17
What is Canine Distemper Virus (infection and spread overview)?
Describe Distemper virus? Consequences of being enveloped?
> CDV (infection/spread overview):
- Infectious disease of dogs and other carnivores
- Pantropic – generalised infection in many organ systems as the receptors are common on many cells
- Spread: close contact or by aerosols infect via URT then go systemic
> Distemper virus:
- Pleomorphic, enveloped virus
- Negative sense single stranded RNA
- Attaches to cells using F-protein
- Replication in cytoplasm buds from cells
> As it is enveloped: - Relatively labile: Sensitive to heat, desiccation, lipid solvents and non-ionic detergents and disinfectants SO isolation and disinfection can control outbreaks
- Vaccines: H-protein can be used to induce neutralising antibodies
NOTE: (GENERALLY) enveloped viruses are more labile than non-enveloped- easier to disinfect and persist less well in environment
