Neuro Flashcards
name the regions supplied by the cerebral arteries
- The middle cerebral artery runs between the lateral fissure and supplies the lateral aspect of the cerebrum
- The anterior cerebral artery passes between the hemispheres and wraps around the corpus callosum to supply the anteromedial aspect of the cerebrum.
- The posterior cerebral artery wraps around the midbrain and supplies the medial and lateral surfaces of the posterior cerebrum [temporal lobes and the occipital lobe]
what type of tissue makes up the cerebrum
white matter
grey matter
what is the difference between white and grey matter
grey matter contains neurones and is responsible for cognition and processing. it forms the cerebral cortex
white matter is made up of myelinated axons only. they carry info between cells and regions
what are the 3 classes of white matter axonal fibres
-
commisural fibres
- corpus callosum
- fibres running between the 2 hemisphere
-
projection fibres
- run up and down between the forebrain, midbrain and hindbrain, brainstem and spinal cord
- the internal capsule is the biggest projection fibre
-
association fibres
- restricted to one hemisphere and to the cerebral cortex
what structure separates the parietal lobe from the frontal lobe
the central sulcus
what is the general role of the frontal lobe
- motor control of body
- also responsible for
- Problem solving, memory, judgement, impulse control, higher cognitive function, language and executive function.
where is the motor cortex located and what does it contain
in the pre-central gyrus
the motor homunculus and upper motor neurones that project down to lower motor neurones
what is the general role of the parietal lobe
- somatosensory info - touch, pain, heat and joint position
where is the somatosensory cortex located
in the postcentral gyrus
has a somatosensory homunculus, set up in a similar way to the motor homunculus
general role of the occipital lobe
vision
where is the visual cortex located
in the occipital lobe at the calacrine sulcus
what is the role of the temporal lobe
- Responsible for:
- Primary auditory cortex and understanding speech
- Semantic processing – meaning and identity of things
- Memory and language.
- Can be divided into 3 big gyri: superior, middle and inferior.
the brain is symmetrical T/F
False
- there is torque on the brain→ the right hemisphere sticking out further in the front than the left.
- the left hemisphere is slightly larger than the right and sticks out further at the back than the right
- both these → talia = the appearance of the brain twisting
what is Broca’s area and where is it located
this is the region of language production
located in the left hemisphere in the majority of people, in the frontal lobe
whta is wernicke’s area and where is it located
the area of the brain that understands language
located in the temporal lobe on the superior posterior temporal lobe
what are the 3 major area of the brain
Forebrain, midbrain, hindbrain
what are the layer of the meninges in order
PAD out
- First layer = dura mater.
- A tough fibrous layer.
- Highly vascularised
- Second layer = arachnoid mater.
- More delicate.
- It is avascular, and does not receive any innervation.
- Third layer = pia mater.
- Most delicate and v thin. Contributes to BBB
- Folds over the groves of the brain
- Highly vascularised
what lies beneath the arachnoid mater
subarachnoid space
- this contains CSF to cushion the brain
- there are arachnoid granulations that start from the subarachnoid space, cross the arachnoid and sub dural space to reach the dura mater.
- they allow for the drainage of CSF back into circulation via the dural venous sinuses
what lies beneath the dura mater
the sub dural space
what do the meninges cover
the brain and the spinal cord
was is the dura mater composed of
2 layered sheets of connective tissue
- Periosteal layer – lines the inner surface of the bones of the cranium.
- Meningeal layer – located deep to the periosteal layer. It is continuous with the dura mater of the spinal cord.
what are the layers of dura mater called and
what lies between them
- periosteal layer and the meningeal layer
- the dural venous sinuses lie between the layers
function and drainage of the dural venous sinuses
they drain deoxygenated blood from the cranium
they drain into the internal jugular vein
dural blood supply and innervation
middle cerebral artery
trigeminal nerve innervation
what are the key dural reflections?
- Falx cerebri - separates the right and left hemispheres of the brain
- attaches to the crista galli
- tentorium cerebelli - seperates the occipital lobe from the cerebellum
- falx cerebelli - separates the left and right hemispheres of the cerebellum
what are the entry points in the skull for the ICA
and what vessel do they branch from
ICA enters the skull via the carotid canal of the temporal bone
they branch from the left and right common carotid arteries, which bifurcate at C4 into internal and external CAs
what are the entry point in the skull for the vertebral arteries
and what vessel do they branch from
enter through the foramen magnum
branches of the subclavian arteries
what are the sinuses of the brain
and what do they drain into
- Superior sagittal sinus
- Inferior sagittal sinus
- Straight sinus
- Transverse sinus
- Sigmoid sinus
- cavernous sinus
- drain into the internal jugular vein
what is the anterior spinal artery a branch of
and where does it run
brnaches from the vertebral arteries
runs down the anterior middle of the spine
what is the cavernous sinus and where is it located
it is a paired dural venous sinus that has 5 nerves and the ICA running through it
located beside the body of the sphenoid bone and is proximal to the pituitary gland
what structures run through the cavernous sinus
- 5 cranial nerves
- oculomotor
- abducens
- trochlear
- opthalmic - trigeminal V1
- Maxillary - trigeminal V2
- the internal carotid artery
clinical relevance of the cavernous sinus
- it is proximal to the pituitary gland, so a pituitary adenoma can compress the nerves and cause problems
- the ICA is next to the abducens, if it enlargens it can→ cross eyed
- bursting of the ICA will lead to mixing of venous/arterial blood = bruit
what is an emissary vein
+ why are they important
a communicating vein between intra and extracranial veins
they provide a route of entry for infection
what are the key elements of the BBB
and what are their function
- lack of fenestrations in the basement membrane
- for impermeability
- tight junctions
- to prevent the passage of molecules in the gap between endothelial cells
- astrocytic end feet
- Astrocytes = support cells of the brain
- They send out processes which end in feet that wrap around the whole blood vessel to form the Glia limitans. This prevents molecular free flow into the brain
- pericytes
- regulate permeability of the BBB
what lines the ventricular system
ependymal cells: ciliated glial cells
where is CSF produced
in the choroid plexus which is found in all the ventricles BUT the largest aggregation is in the lateral ventricles, thus the majority of CSF is produced here
which cells produce CSF
ependymal cells
how many ventricles are there
4
describe the structure of the ventricles
-
lateral ventricles [1+2]
- one in each hemisphere of the brain
- CSF flows through the interventricular foramen into the 3rd ventricle
-
3rd ventricle
- Slit-like between the two thalami
- Hole in for inter-thalamic adhesion
- Drains through the cerebral aqueduct to the 4th ventricle
-
4th Ventricle
- A diamond shaped space between the cerebellum and brainstem
- Drains through the foramen of Magendie and Foramina of Luschka into the subarachnoid space and the spinal cord
- middle magendie lateral luschkas
what are the main function of CSF
- protection
- buoyancy
- chemical stability : maintainance of a chemically stable environment for the brain to function properly
what is the main function of the cerebellum
fine motor movement
balance
what is the largest part of the hindbrain
the cerebellum
describe the structure of the cerebellum
- 2 hemispheres -right and left. joined in the middle by the vermis
- outer layer grey matter cortex and inner layer of white matter which surrounds the deep nuclei [aggregations of nerve cells]
- attached to each structure of the brainstem by the superior, middle and inferior peduncles
- has a flocculo-nodular lobe
- Major fissures = horizontal and primary fissures
- Horizontal divides into superior/inferior
- Primary divides into anterior and posterior.
what are the functional divisions of the cerebellum
Vestibulocerebellum – involved in controlling balance and ocular reflexes [floculonodular node]
Cerebrocerebellum – lateral hemispheres, involved in planning movements and motor learning. It regulates coordination of muscle activation and is important in visually guided movements.
Spinocerebellum – vermis and intermediate of the cerebellar hemispheres. Involved in regulating body movements.
what are the primary vesicles in neurological embryology
what are the secondary vesicles in neurological embryology
what is the vertebral column made of
- 7 cervical vertebrae
- 12 thoracic vertebrae
- 5 lumbar
- 5sacral vertebrae fused together
- coccyx formed from 4 vertebrae
where on the vertebral colum do the legs start bearing weight
the lumbar region
how to differentiate between vertebrae
- vertebral body
- C: small and oval
- T: larger
- L: largest
- spinous process
- C: slender and bifid
- T: long and point downwards
- L: short and points straight back
- transverse process
- C: small and come after transverse foramina
- T: large with costal facets for rib articulation
- L: large, flat blunt
- foramina
- C: 2 sets: transverse and 1 vertebral formen that is the largest and ovalish
- T: small and round
- L: small and ovalish
name the parts of a vertebra
- body
- transverse process
- spinous process
- lamina
- pedicle
- superior and inferior articular processes
describe the structure of the spinal cords at a vertebra
- H-shaped centre of grey matter containing:
- cell bodies and dendrites of efferent neurones and glial cells
- Dorsal root
- Ventral root
- white matter surrounding the grey matter made of:
- myelinated axons arranged in ascending or descending tracts
difference between dorsal and ventral horns
- Dorsal root = afferent and is affected by sensory stimuli [affected by the world]
- Ventral root = efferent and it takes effect on the muscles thus is a motor function.
what makes up the hind brain
medulla
pons
cerebellum
difference between afferent and efferent fibres
- AFFERENT FIBRES: from the PNS enter the cord on the dorsal roots
o The cell bodies are in the dorsal root ganglia (neural crest cells) - EFFERENT FIBRES: leave the spinal cord at the ventral roots
- together they form the spinal tract \
why are the spine and the spinal cord not the same length
they both grow at different rates - the cord grows slower than the spine.
the nerves in the last few sections of the cord have to travel further to extend through the vertebrae
where are lumbar punctures taken from and why
taken below L1 becuase from this point onwards there is no longer any spinal cord BUT there is spinal fluid.
what covers the spinal cord
PAD out
same as the brain
where is CSF found in the spine
in the central canal - continuous with the 4th ventricle
where are cell bodies for sensory and motor nerves
- sensory neurone bodies lie within the dorsal root ganglion
- motor neurone bodies lie deep within the grey matter
the spinal cord is uniform along its length
T/F
False
- The amount of grey matter varies depending on the complexity of movement in the area of the body being regulated.
where does the spinal cord begin
the spinal cord begins from where the C1 nerve exits the spinal cord
difference between upper motor neurones and lower motor neurones
- UMNs synapse to the LMNs and originate in the motor cortex
- LMNs synapse onto the muscle or effector organ
name the descending spinal tracts and their brief function
- pyramidal - voluntary and fine control
-
corticospinal - supplies muscles of the body
- lateral - decussates before entering the spinal cord
- anterior - decussates after entering the spinal cord.
- corticobulbar - supplies muscle of head and neck. terminates on the cranial nerves
-
corticospinal - supplies muscles of the body
- extra-pyramidal - balance, coordination, muscle tone and posture volu
- vestibulospinal
- reticulospinal
- dont decussate therefore ipsilateral innervation
- rubrospinal
- tectospinal
- DECUSSATE therefore contralateral innervation
what are the main differences between Extra-pyramidal and pyramidal descending tracts
funtion and origin
- pyramidal are:
- responsible for voluntary control of the face and body muscles.
- originate in the motor cortex
- extrapyramidal are:
- responsible for involuntary and automatic control of all muscles
- do NOT originate in the motor cortex
name the ascending spinal tracts
- spinothalamic
- DCML - dorsal column medial lemniscus
- splits into gracilis and cuneatus
- spinocerebellar
which tracts are funiculi cuneatus and gracilis a part of
and where do they carry info from
the ascending DCML tract
gracilis carries from the lower limbs below T6
cuneatus carries from upper limbs
what tracts make up the spinothalamic tract
and what info do they carry
- anterior tract
- carries crude touch and pressure
- lateral tract
- carries pain and temperature
summarise the pathway of the spinothalamic tract
- 1st order neurones from periphery enter spinal cord through dorsal root ganglion, ascend ipsilaterally for 1-2 segments and synapses
- 2nd order neurones decussate across the anterior white commissure AND split into the anterior and lateral tracts. Then ascends to the thalamus
- 3rd order neurone carries info from the thalamus to the primary sensory cortex through the internal capsule
what info does the spinocerebellar tract carry
uncoscious proprioception of the trunks and limbs
what info does the spinothalamic tract carry
- anterior = crude touch and pressure
- lateral = pain and temperature
what info does the DCML tract carry
fine touch, vibration and proprioception
summarise the pathway of the DCML tract
- 1st order neurones from periphery enter spinal cord through dorsal root ganglion, in the posterior column and ascends ipsilaterally to the medulla, then synapses
- 2nd order neurone decussates across the medulla then ascends to the thalamus and synapses
- 3rd order neurone travels to the ipsilateral primary sensory cortex.
label
function of the axon hillock
generates impulse in the neuron
function of dendrites
receive signals from other cells
function of the axon
transfers signals to other cells
function of the myelin sheath
increases the speed of signal transmission
function of the axon terminal
form junctions with other cells
how is the resting potential is established
- anions are restircted inside the cell → overall negative intracellular charge at rest
- K+ ions found at a higher conc. within the cell
- Na+ and Cl- are found in higher conc. outside the cell.
- at rest the cell membrane is permeable to Na+, Cl- and K+.
- K+ moves OUT of the cell
- Na+ and Cl- move IN to the cell
- Ion distribution is determined by the sodium potassium pump.
- 3Na+ out and 2K+ with ATP.
- Net loss of +ve charge inside the neuron
what is an action potential
an action pd is a temporary reversal of the cell membrane charge
how is an action potential generated
- neurotransmitters cause a change in membrane permeability at the dendrites → ions crossing and changing the membrane potential
- this change passes through the cell and if the threshold is reached at the axon hillock an action pd is generated
what is the all or none theory
that a maximal stimulus is generated once the threshold potential is reached.
what types of action potentials are there
- Excitatory Ntransmitters depolarise the membrane and INCREASE the chance of action pd and → excitatory post synaptic potential EPSP
- Inhibitory Ntransmitters hyperpolarise the cell membrane DECREASE the chance of an action pd → inhibitory post synaptic potential. IPSP
what is a post-synaptic potential
a temporary change in the polarisation of the membrane of a neurone
what are the different types of summation
which is the most efficient
- temporal summation
- numerous subthreshold frequencies from 1 presynaptic neurone in a short space of time
- spatial summation
- numerous subthreshold frequencies recieved from multiple presynaptic neurones
- spatial is the most efficient
describe an action potential
- resting pd = -70mV
- threshold = -60mV
- an EPSP begins depolarisation → opening of ligand-gated Na+ channels and influx of Na+ → depolarisation
- at - 60mV at the axon hillock Na+ voltage-gated channels open and membrane potential reverses → +30mV
- at +30:
- Na+ voltage-channels close = influx stops
- K+ voltage-channels open = efflux starts
- this restores the resting potential
- once -60mv is reached this marks the relative refractive period
- at -70mv the K+ voltage-channels shut → hyperpolarisation and then the resting state
what is myelin
a fatty insulating substance that speeds up rate of action potential conduction via saltatory conduction
what cells produce myelin
- Schwann cells peripherally
- oligodendrocytes centrally
describe saltatory conduction
the action pd jumps between nodes of ranvier as myelin is insulating
what is the difference between absolute and relative refractory periods
- relative: the Na+ voltage channels are shut but have the potential to open
- absolute: no action pd can occur at all during this stage
what are the 5 fundamental processes needed for neurotransmission
- Manufacture neurotransmitters via intracellular biochemical processes
- Storage in vesicles
- Release stimulated by action potential
- Receptor activation by interacting with post-synaptic receptors following diffusion across the synapse
- Inactivation – break down or re-uptake
what causes MS
the degeneration of peripheral myelin produced by schwann cells → disruption of action pd transmission
difference between schwann cells and oligodendrocytes
-
CNS = oligodendrocytes.
- A single oligodendrocyte can myelinate 50 axons
-
PNS = Schwann cells
- A single cell myelinates ~1.5mm long segments
describe the release of neurotransmitter - pre-synaptic
- action pd arrives at the axon terminal
- this triggers the opening of the calcium ions and influx of Ca2+ ions
- Ca++ stimulates the release of neurotransmitter via exocytosis at the pre-synaptic membrane
- neurotransmitters crosses the synapse to bind to the post-synaptic receptors and cause depolarisation.
what are some effects of sympathetic stimulation
- •Increased heart rate
- •Increased force of heart contraction
- •Vasoconstriction
- •Bronchodilation
- •Reduces gastric motility
- •Sphincter contraction
- •Male ejaculation
the enteric nervous system can operate independently of the autonomic nervous system
T/F
True
what are some effects of parasympathetic innervation
- •Decreased heart rate
- •Decreased force of heart contraction
- •Vasodilation
- •Bronchoconstriction
- •Increased gastric motility
- •Sphincter relaxation
- •Male erection
where are NMJs usually located
•Neuromuscular junctions are typically located in the middle of a muscle fibre, so action potentials are propagated in both directions
only some NMJs are excitatory
T/F
- False
- they all are
which neurotransmitter is responsible for NMJ excitation
ACh
acetylcholoine
how is NMJ excitation halted
ACh is broken down by acetylcholinesterase in the synaptic junction of the NMJ and recycled / reabsorbed in the axon terminals
what is an alpha motor neuron
alpha motor neurons are lower motor neurons whose cell bodies are found in the anterior horn of the spinal cord and whose axons travel down to the body to innervate skeletal muscle to cause muscle contraction.
what type of neurones are contained in the motor pool
alpha neurones
gamma neurones
where do alpha motor neurons originate
the spinal cord
what are the stimuli for cell bodies in the ventral horn
- sensory info from the muscles
- descending info from the brain
define proprioception
- Proprioception = giving the brain info about joint position and pressure and stress placed on the joints by the muscles.
how is proprioception facilitated in the limbs
via:
- Golgi tendon organs to sense how much tension is on the muscle.
- Muscle spindles to sense the degree of stretch in the muscle.
what is a motor unit
- A motor unit = a single motor neurone and all the muscles fibres it innervates.
what is a motor pool
- Motor pool = all the LMNs that innervate a single muscle
where are golgi tendon organs found and what is their function
- found in the tendons of muscle
- fx = It sends ascending sensory info to the brain, via the spinal cord, about how much force there is in the muscle. Thus it is crucial for proprioception.
how is the Golgi tendon organ a protective mechanism
- Under extreme tension the GTO can inhibit the muscle fibre and stop it from being contracted to prevent damage.
- It will also contract the antagonistic muscle
- this is a reflex
the larger the motor unit the finer the control
T/F
False
the smaller the motor unit the finer the control
e.g. the fingers will have a smaller motor unit than the shoulder.
what is the difference between alpha motor neurones and gamma motor neurones
- alpha motor neurons are involved in voluntary muscle contraction
- gamma motor neurons are involved in reflex muscle contraction
what is a muscle spindle
and what is its function
- an intrafusal muscle fibre AND a sensory extension of a sensory neurone wrapped around the fibre.
- prevent overstretching of the muscles
difference between intrafusal and extrafusal muscle fibres
- intrafusal have sensory extension wrapped around and are innervated by gamma motor neurones
- extrafusal are normal muscle fibres and are innervated by alpha motor neurones
explain how a muscle spindle fibre works
this is the myotactic reflex circuit
- the muscle spindle detects over-stretching of the muscle → signal sent via the sensory neurone to synapse with:
- the alpha motor neurones of the same muscles the spindle fibre is in → contraction of the muscle to help shorten the length
- the alpha neurones of the antagonistic muscles to inhibit them → relaxation
what is the inverse myotactic reflex
what is its purpose
- fx = protects muscles from overload
- if golgi tendon organs are stimulated long enough a sensory impulse is generated that synapses on the:
- agonist muscle under tension → relaxation
- antagonistic muscle → contraction
- overall effect = relaxation of the muscle
what is the basal ganglia
a collection of deep nuclei in the cerebral hemispheres
describe the input and output of the basal ganglia
- mainly receives excitatory input from glutamate [neurotransmitter]
- output is mainly inhibitory and takes effect on the cerebrum
components of the basal ganglia
- caudate nucleus,
- putamen,
- globus pallidus,
- sub-thalamic nucleus,
- substantia nigra.
describe the outputs of the basal ganglia
inhibitory in order to regulate movement
slow and tonic = slow and continuous
functions of the basal ganglia
- Turns down the thalamic excitation of the cortex → inhibition of cortical activity.
- The basal ganglia talks to the cortex and coordinates movement for balance and posture.
- It finds out from the muscle spindles proprioception and allows for the correct posture.
what are the components of the limbic system
- cingulate gyrus
- hippocampal formation
- parahippocampal gyrus
- septal nuclei → reward and reinforcement
- anterior perforated substance
- amygdala → fear and reward
- uncus
why is papez circuit significant
•Controls emotional expression
Significant role in memory functions
what is a common cause of upper motor neurone damage
stroke
what are signs of upper motor neurone damage/ weakness
- Hypertonia = abnormally high level of muscle tone due to loss of descending inhibition
- Hyperreflexia = brisk reflexes
-
Spasticity = muscle is tight and stiff on passive movement
- Clasp knife reflex can also be present
- This is the rapid decrease in resistance when flexing a joint
- Clasp knife reflex can also be present
- Positive Babinski sign = large toe extends (instead of flexes) in response to a blunt object stroked on the plantar surface
- Clonus = where a muscle is suddenly stretched and held there
what are signs of lower motor neurone damage
- Hypotonia = reduced or absent muscle tone
- Hyporeflexia = decreased or absent reflexes
- Flaccid muscle weakness or paralysis
- Fasciculations = small involuntary muscle twitches
- Muscle atrophy
what are the names for C1 and C2 vertebrae
C1= Atlas
C2 = Axis
the axis has a spike called the dens that inerts into the axis to allow for head rotation
the larger the motor unit the stronger the contraction
T//F
true
e.g. a leg muscle has a larger motor unit than muscles of the eye
define muscle tone
the level of contraction within a muscle at any time - including at rest
describe an action pd at an NMJ
- action pd arrives at the axon terminal → Ca++ influx → release of ACh into the synaptic cleft
- ACh binds to post-synaptic nicotinic receptors, which are Na+ ligand gated channels → Na+ influx.
- this creates an end plate potential [EPP].
- when the EPP reaches a threshold, voltage gated Na+ ion channels open up → further depolarisation.
- a wave of depolarisation spreads across the fibre and into the T-tubules, reaching the sarcoplasmic reticulum and causing Ca++ release needed for muscle contraction.
- K+ voltage gated channels open up to allow repolarisation of the membrane and
- acetylcholinesterase breaks down ACh→ acetate +choline
what are the sections of the brainstem
- mindbrain
- pons
- medulla
where do spinal tracts decussate on the medulla
The anterior median fissure
what is the function of the olives
- Olives interact with the cerebellum and are involved with coordination of movements.
how many fasciculi are there
where are they found
what is their function
- 2 - gracilis and cuneatus
- on the posterior side of the medulla
- function
- Fasciculus gracilis carries info from the lower body
- Fasciculus cuneatus carries info from the upper body
what is the rhomboid fossa and what does it mark
a structure on the back of the pons marking the floor of the 4th ventricle
how does the cerebellum attach to the brain
- The cerebellum is connected to the brainstem by three pairs of cerebellar peduncles:
- the superior peduncle with the midbrain,
- the middle peduncle with the pons,
- the inferior peduncle with the medulla oblongata.
function of the pons
- The pons = a communication structure.
- fibres run across it and through the middle cerebellar peduncle for communication
how does the fore brain interact with the brainstem
- via the crus cerebri [cerebral peduncles]
where are the mamillary bodies located
between the crus cerebri
involved in emotional regulation
which structures of the brainstem are involved in auditory processing
- inferior colliculus
- medial geniculate body
- both linked by inferior brachium
which structures of the brainstem are involved in visual processing
- superior colliculus
- lateral geniculate bodies
- both linked by superior brachium
location and function of the limbic system
- This is a collection of structures at the inner edge of the cortex involved with emotion, memory and fight or flight response.
function of the hippocampus
- Important for the regulation of storage of memories.
- Loss of function → loss of ability to form new memories.
function of the thalamus
main relay station of the brain
hypothalamus function
- homeostasis via hormone control
- memory formation
function of the amydala
- Produces instinctive emotional output
- Responsible for emotional memory
- Responsible for fear
how many layers of cerebellar cortex are there
3
- Molecular = most outer, fibre-rich
- 2 types of neurons: stellate and basket cells
- Stellate cells are mostly GABAnergic (inhibitory)
- Basket cells are GABAnergic interneurons
- 2 types of neurons: stellate and basket cells
- Purkinje = middle layer
- Monolayer of large cells
- Vast branching pattern
- Synapses with parallel fibres in the molecular layer
- Provide only efferent pathway to deep cerebellum
- Receives input from climbing fibres
- Granule = most inner (largest) layer
- Many small cells – granule cells
- Receives input from mossy fibres
whats the largest cerebellar nucleus
dentate nucleus
what is the substantia nigra
- dopamine centre of the brain
- part of basal ganglia
- projects onto the striatum → nigrostriatal pathway needed for movement
what are the areas of the substantia nigra
and where is the majority of dopamine produced
- pars compacta and pars reticulata
- PC produces most dopamine
- PR has GABA neurons
where are the tectum and tegmentum found
- in the midbrain
- tectum is posterior to the cerebral aquaeduct
- tegmentum is anterior to cerebral aquaeduct
- in the pons and medulla
- only the tegmentum is present
name the structures
- caudate nucleus
- putamen
- subthalamic nucleus
- substantia nigra
- caudate nucleus
- claustrum
- globus pallidus - internal and external
summarise the direct pathway of the basal ganglia
- the motor cortex stimulates the striatum
- the striatum inhibits the internal globus palidus
- the inhibited internal globus palidus now cant inhibit the thalamus
- the thalamus is free to stimulate the motor cortex
summarise the indirect pathway of the basal ganglia
- Motor cortex excites striatum
- Striatum inhibits the External Globus Pallidus.
- External globus pallidus is inhibited so can’t inhibit the subthalamic nuclei
- Subthalamic nuclei free to stimulate the Internal globus pallidus
- Thalamus is inhibited by internal globus pallidus - no stimulation to motor cortex
summarise the layers of the eye
- outer
- cornea
- sclera
- middle [uvea]
- iris
- ciliary body
- choroid
- inner
- retina
function of the cornea
- transmission of light
- refraction of light
- transparency
- smooth surface
function of the sclera
- whites of the eyes
- tough outer layer for protection made of collagen
function of the iris
- controls pupil size using sphinter and dilator muscles
- sphinter muscles controlled by parasympathetic branch of CN3
- dilator muscles controlled by sympathetic
- gives the eye colour
ciliary body function
- Glandular epithelium produces the aqueous humour
-
Ciliary smooth muscle controls accommodation.
- Involved in pathophysiology of closed angle glaucoma
- innervated by parasympathetic branch of CN7
function of choroid of the eye
- Blood supply to the outer third of the retina
- Vascular web attached to retina and sclera.
- Heat sink – the blood traps heat produced by light and takes it away.
main areas of the retina
- macula lutea
- fine vision – rods + cones present but high conc. of cones.
- fovea centralis
- centre of macula. Cones only therefore very sharp vision
- optic disc
- exit of the optic nerve. No photoreceptors thus it’s a blind spot
types of photoreceptors
and their function
Rods = dim lighting, sensitive, peripheral vision
Cones = colour vision
describe the blood supply to the eye
- Internal carotid artery
- Ophthalmic artery,
- central retinal artery
- ciliary arteries
- External carotid artery
- Facial artery supplies medial lid and orbit
what collects together to form the optic nerve
Ganglion cells are the major output cells of the retina. Their axons gather at the optic disk, where they become myelinated and form the optic nerve.
layers of the retina
- pigmented layer
- photoreceptors
- bipolar cells
- ganglion cells
- optic nerve
how does the visual field relate to the visual quadrants
the visual feed in upside down and inversed when it enters the eye
describe the visual fields and where visual information is captured within the eye
- in the right eye
- the lateral eye perceives info from the left field of vision
- the lower quadrant collects info on the upper left field of vision
- the upper quadrant collects info on the lower left field of vision
- the medial eye perceives info from the right field of vision
- the lower quadrant collects info on the upper right field of vision
- the upper quadrant collects info on the lower right field of vision
- the lateral eye perceives info from the left field of vision
- overall between both eyes, the lateral and medial sections of each eye work together to see a visual field
- the right lateral and left medial see the left visual field
- the left lafteral and right medial see the right visual field
how many neurons in visual pathway
what are they
- bipolar neurons
- ganglion neurones [converge into optic nerve]
- optic radiation
- cell bodies reside in the lateral geniculate body of the thalamus
describe the pathway of the optic nerve
- lateral and medial divisions in each eye
- the lateral branches travel to the lateral geniculate body [LGB] ipsilaterally and synapse
- the medial branches pass the optic chiasm and decussate before passing to the LGB and synapsing.
- the optic nerve → optic tract after the optic chiasm
describe the pathway of the optic radiation
- axons from the LGB carry info to the visual cortex via 2 branches
- the upper optic radiations carry fibres from the superior retinal quadrants [inferior visual field] = Baumans loop.
- Travels upwards through the parietal lobe.
- the lower optic radiations carry fibres from the inferior retinal quadrants [superior visual field] = Meyer’s loop.
- Travels laterally through the temporal lobe.
- the upper optic radiations carry fibres from the superior retinal quadrants [inferior visual field] = Baumans loop.
effects of:
- Damage to the left optic nerve
- Damage to optic chiasma
- Damage to left optic tract
- Damage to left Meyer’s loop
- Damage to left Baum’s loop
- Damage to the left optic nerve
- No vision in left eye
- Damage to optic chiasma
- Loss of vision of the temporal visual fields → Hemianopia
- Damage to left optic tract
- Loss of vision of temporal field of left eye
- Loss of vision of nasal field of right eye
- Damage to left Meyer’s loop
- Loss of vision in superior nasal field of left eye
- Loss of vision in superior temporal field of right eye
- Damage to left Baum’s loop
- Loss of vision in inferior temporal field of right eye
- Loss of vision to inferior nasal field of left eye
what will these defects cause
what is the pupillary light reflex
which nerves are involved
- In response to light
- One eye seeing bright light → Both pupils contracting
- Afferent limb – Optic nerve (CN2)
- Efferent limb – Oculomotor nerve parasympathetic branch (CN3)
what is the corneal reflex
which nerves are involved
- Stimulation of cornea (something touching eyeball) →
- Involuntary blinking of both eyelids
- Afferent – Trigeminal nerve (CN5) Ophthalmic branch (V1)
- Efferent – Facial nerve (CN7)
what is accommodation
which nerves are involved
which muscle is involved
- Focusing the lens to see an object clearly
- Oculomotor nerve (CN3)
- ciliary bodies adjust the lens
function of the outer, middle and inner ear
- Outer ear
- Helps collect sound
- Middle ear
- Transmits and amplifies sound
- Inner ear
- Converts sound to neural impulses
function of the pinna/ auricle
directs sound into the ear
summarise the transmission of sound through the ear
- pinna directs sound into the ear
- the sound passes through the external auditory canal
- at the middle ear the sound waves cause vibrations of the tympanic membrane
- these vibrations are transmitted to the oval window of the cochlea by the ossicles:
- malleus
- incus
- stapes
- at the oval window, the sound waves are converted to waves of fluid in the scala vestubuli which then gets transmitted across to the scala tympani, via the helicotrema.
- at the same time the basilar membrane also starts moving.
- the tectorial membrane remains in one position whilst the basilar membrane moves up and down. this causes the hair cells to bend and the formation of action pds in the CN8
where is the eustachian tube found and what is its function
- the opening is found in the middle ear and the other end is in the pharyx. so it links the two
- fx = pressure equalisation
function, innervation and location of tensor tympani and stapedius
- tensor tympani innervated by mandibular branch of trigeminal
- stapdius innervated by CN7
- both reduce the transmission of sound to the cochlea when contracted as a protective reflex.
- located in the middle ear
how is sound information passed to the auditory cortex
- info is carried from the organ of corti to the auditory cortex by the vestibulocochlear nerve [CN8] through the Lemniscal pathway
what are the main compartments of the organ of corti
- scala tympani
- scala media
- scala vestibuli
what are hair cells?
describe the layout of the hair cells
Hair cells = mechanoreceptors, have stereocilia protruding from one end
- 1 row of inner hair cells
- 3 rows of outer hair cells
functions of the hair cells
- outer hair cells amplify low-level noises
- inner hair cells release neurotransmitters that stimulate the vestibulocochlear nerve
- bending of the hair cell → influx of K+ ions → depolarisation
- depolarisation → release of Ca++ via voltage gated channels
- this causes the release of excitatory neurotransmitters
describe the structure of the basilar membrane
and how does this link to its function
- basilar membrane runs along the length of the cochlear and forms the base of the organ of corti.
- it is stiff and narrow at the base
- High pitched sounds detected at the base of the cochlear
- it is floppy and wide at the furthest end
- Low pitched sounds detected at the apex
how are louder sounds distinguished from quieter ones
louder sounds stimulate more hair cells → more nerve signals sent to the brain
how are sound of different frequencies detected
- High pitched sounds detected at the base of the cochlear as they have more energy and can move this part of the basilar membrane
- Low pitched sounds detected at the apex as they have less energy to move the membrane.
- at these locations hair cells are triggered, → nerve signals sent
describe the auditory pathway
- ECO LIMA
- Ear receptos + Eigth cranial nerve
- Cochlear nucleus
- Olives
- Lateral lemniscus
- Inferior colliculi
- Medial geniculate body
- Auditory cortex
key structures of the vestibular system
semi circular canals
saccule
utricle
where are he semi circular canals found
inside the petrous part of the temporal bone in the ear for balance
where is the spinal cord derived from
derived from the ectoderm
what is a relative refractive period
It is the period where a second stimulus must be stronger to produce an action potential
role of the basal ganglia in the control of motor fuction
- Planning and modulation of movement pathways
- They select the most appropriate motor action to pass back to the cortex for execution.
Awareness of pain is associated with activity in which region of the brain
pre-frontal cortex
describe an electrical synapse
- Connexins form junctions with a channel running through the middle
- The action pd passes through the channels from one cell to the next.
- The action pd can travel in both directions.
what is arborisation of a dendrite or axon
branching of axons or dendrites
what are glial cells
the support cells of the neurones of the CNS
5 examples of glial cells
- oligodendrocytes
- microglia
- schwann cells
- astrocytes
- ependymal cells
role of microglia
- Microglia are the immune cells of the CNS
- they are phagocytic
- they remain unactivated and ramified until required → ramification retraction and ameboid structure
role of ependymal cells
- Responsible for the production, flow and absorption of CSF.
- a collection of specialised ependymal cells = choroid plexus
role of astrocytes
- involved in many roles thus its the most abundant
- axon guidance and synaptic support,
- to the control of the blood brain barrier and blood flow
- development
- brain structure
what is the most common cell of the CNS
astrocytes
cerebellar dysfunction
DANISH.
Dysdiadochokinesia
Ataxia
Nystagmus
Intention tremor
Slurred speech
Hypotonia
