Neurology Flashcards
What plane is this?
Coronal plane
What plane is this?
Horizontal/transverse/axial plane
What plane is this?
Sagittal plane
What is the purple structure?
Label its parts:
Brainstem
What is this?
Cerebellum
What does the brainstem carry + function?
-Ascending sensory and descending motor tracts
-Breathing, consciousness, heart rate, sleep
What are the functions of the cerebellum?
-Balance & coordination
-Gait, posture, motor learning, fine skills
What is this?
What does the thalamus do?
Sensory relay station
What is this?
Hypothalamus
What is the function of the hypothalamus?
-Homeostasis
-Temperature, food intake, water content, endocrine control, body cycles
What are these?
Hippocampus & fornix
in what lobe are the hippocampus and fornix and what are their functions?
-Temporal lobe
-Learning & memory, spatial navigation
What is this?
Lateral ventricles (aqua)
What is the function of the lateral ventricles?
Cerebrospinal fluid (CSF) production and recycling
What is this?
Caudate nucleus
What is the function of the caudate nucleus?
-Planning & execution of movement
-Memory, cognition, emotion
What is this?
Putamen
What is the function of the putamen?
-Regulation of movement c.f caudate
-Cognition and reward
What is this?
Amygdala
What are the functions of the amygdala?
Emotional learning & behaviour, fear, anxiety and aggression
What is this?
White matter
What does this show?
Label the diagram:
What is the function of sub-cortical white matter?
Interconnects cortical and sub-cortical regions
What are the functions of the cortical grey matter?
-Higher processes - memory, thinking, problem solving, reasoning, consciousness, emotion
-Sensory processing
-Movement
Label this diagram:
What major landmarks can be identified to help locate brain structures?
-Corpus callosum
-Lateral sulcus
-Brainstem
How are myofibres arranged in skeletal muscle?
Fascicles
What connective tissues are in skeletal muscle?
-Epimysium
-Perimysium
-Endomysium
What surrounds each myofibre?
What is its role?
-Basement membrane
-Tensile strength, regeneration, development
What makes up the basement membrane surrounding myofibres?
-Collages
-Glycoproteins
-Proteoglycans
What three external things connect to skeletal muscle?
-Vascular supply
-Innervation
-Myotendinous junction - transmit force of contraction to tendon
What is the innervation to skeletal muscle?
-Each fibre innervated by one nerve
-Cell bodies in anterior horn of spinal cord or brainstem
What is a motor unit?
One neuron innervates multiple muscle fibres
What are neuromuscular junctions?
Neurotransmitter?
-Synapse - rapid transmission of depolarising impulse
-Acetyl choline - binds to post-synaptic AChR
Describe proprioception in skeletal muscle:
-Length and tension
-Muscle spindles - encapsulates intrafusal fibres
-Mediate stretch reflexes and propriorecpetion
-Golgi tendon organ
Label this diagram:
What does it show?
Skeletal muscles - control and sites of pathology
What is a myopathy?
Primary muscle disease
What are the 2 types of muscle fibre?
-Slow twitch (red fibres) - fatigue resistane
-Fast twitch - fatigue rapidly but generate a large peak of muscle tension
What are examples of slow and fast twitch muscle fibres?
-Slow: Type 1, oxidative
-Fast: - 2A glycolytic and oxidative (intermediate)
-2B glycolytic (white)
What does this show?
Motor unit
4 features of motor unit:
-Motor neuron (lower) and the fibres it innervates
-Neuron and its fibres of same type
-Fibre type dependant on neuron
-Size of motor unit varies between muscles
What does this show?
Denervation (loss of nerve supply)
What does this show?
Re-innervation (restoration of nerve supply)
What is utilised by the contractile apparatus?
What regenerates one of them?
-High ATP requirement
-Creatine phosphate as short term energy store
-CP replenished by creatine kinase
-CK release on muscle fibre damage (CK serum useful clinically)
What can be diagnosed via muscle biopsy and why?
-Mitochondrial cytopathy
-Affect muscle
-Ragged red fibres, ETC deficit, mitochondrial abnormal morphology
What maintains membrane stability in skeletal muscles?
Dystrophin and its associated proteins
Label this diagram:
What are dystrophies?
-Genetically determines
-Destructibe
-Mainly progressive disorders of muscle
-Defects in proteins conferring stability can be cause
What is the difference between the central and peripheral nervous system?
-CNS - Brain, spinal cord
-Peripheral - Division located outside the skull and spinal cord
What does somatic and autonomic mean?
-Somatic - of the body
-Autonomic - unconscious/automatic
What does somatic nervous system interact between?
What does autonomic nervous system interact between?
Where is the non-brain part of the central nervous system located?
Within vertebral column
What are the different divisions of the spinal CNS?
What are the two parts of the spinal CNS in each vertebrae?
What do dorsal and ventral roots contribute towards and what fibres are they?
-Dorsal root -> Afferent
-SENSORY (affected by the world)
-Ventral root -> Efferent
-MOTOR (having an effect on the world)
What is the first basic subdivision of the brain?
-Forebrain
-Midbrain
-Hindbrain
Label the basic 3 subdivisions of the brain:
What are the further sub-divisions of the forebrain?
-Telencephalon (cerebral cortex, basal ganglia, limbic system)
-Diencephalon (thalamus, hypothalamus)
What is the further sub-division of the midbrain?
Mesencephalon - tegmentum, tectum
What are the further sub-divisions of the hindbrain?
-Metencephalon (pons,cerebellum)
-Myelencephalon (medulla)
Label the further sub-divisions of the brain:
What does the brain compose of in terms of systems?
Brain comprises hierarchy of functional systems providing increasingly sophisticated competences
What does the medulla contain?
Tracts carrying signals between the rest of the brain and the body
What formation does the medulla contain and do?
-Caudal part of reticular formation
-Functions:
-Low level sensorimotor control (e.g. balance)
-Sleep/wakefulness
-Motor plant (movement, muscle tone)
-Reflexes of cardiac, circulatory, respiratory, excretory
Describe the pons and its functions:
-Relay from cortex and midbrain to cerebellum
-Contains millions of neuronal fibres
-Pontine reticular formation (pattern generators) - e.g. walking
What is the function of the cerebellum?
-“Motor errors” between intended movement and actual movement
-Adjusts synaptic weights to eliminate error
-Online correction during movement - motor learning
-Thought-exclusive for motor coordination
Label the parts of the midbrain:
What are they?
-Tegmentum - body of midbrain
-Tectum - roof of midbrain
What does the tectum do?
-Visual/spatial and auditory frequency maps
What is the tectum separated into?
-Superior colliculus:
-Sensitive to sensory change - orienting/defensive movements
-Inferior colliculus:
-Similar but for auditory events
-Connoliculi (little hills)
What is the tegmentum separated into?
-Periaqueductal gray
-Red nucleus
-Substantia nigra
Label the 3 parts of the tegmentum:
What are the functions of the periaqueductal gray of the tegmentum?
-Defensive behaviour role
-Role in pain (ascending and descending signals)
-Role in reproduction
What is the function of the red nucleus of the tegmentum?
What are the parts of the substantia nigra and their roles?
-Part of basal ganglia
-Sustantia nigra pars compacta (dopamine cells) - basal ganglia input
-Substantia nigra pars reticulata - basal ganglia output
What is the diencephalon divided into?
-Thalamus
-Hypothalamus
What is the relay structure of the thalamus:
-Specific nuclei - relay signals to cortex/limbic system for all sensations
-Non-specific nuclei - role in regulating state of sleep and wakefulness and levels of arousal
What is the role of the thalamus?
Important relays from basal ganglia and cerebellum back to cortex
What is the role of the hypothalamus?
-Regulates the pituitary gland which regulates hormonal secretion
-Interface between brain and hormones
-Hormonal control of motivated
-Hunger, thirst, temperature, pain, pleasure and sex
What are the sub-cortical portions of the cerebral cortex?
-Basal ganglia
-Limbic system
Describe the basal ganglia:
-Group of structures
-Loop organisation
-Thought to be involved in motor function since involvement in movement disorders
Describe the limbic system:
-Group of structures
-Emotion, motivation and emotional association with memory
-Influences formation of memory by integrating emotional states with memories of physical sensations
What parts make up the limbic system?
What is the function of the different limbic system parts?
What are the lobes of the brain?
-Frontal
-Temporal
-Parietal
-Occipital
Label this diagram:
Describe the structure of the cortical lobes of the brain:
-Gray matter (6 lobes) : cell bodies
-White matter : fibres/axons
-Biggest part of the brain in primates
What does the frontal lobe contain?
Precentral gyrus from which motor instructions (fine motor control) that are sent to muscles controlling hands and feet
What are the divisions of the frontal lobe?
-Primary motor cortex : Contains many of cells giving in origin to the descending motor pathways (initiation of voluntary movements)
-Premotor and supplementary motor areas : higher level motor plans and initiation of voluntary movements
What are functions of the frontal lobe?
-“executive planning”:
-generating models of consequences of actions
-judgemental roles
-emotional modulation
-Working memory : short term info
-Control of behaviour depending on context or setting
-Prefrontal cortex
What does the prefrontal cortex do?
Generating sophisticated behavioural options that are mindful of consequences
What does the parietal lobe contain?
Postcentral gyrus which receives sensation from the rest of the body
Describe the parietal lobe:
-Primary somatosensory cortex
-Maintains representations of the body’s and head’s position in space
-Permits complicated spatio-temporal predictions e.g. catching something when you are moving
What does the temporal cortex contain?
Primary auditory cortex
Describe the temporal lobe:
-Inferotemporal cortex
-Recognition of faces and objects
-Important role in integrating sensory info from various parts of the body
-Interface between cortex and limbic system - association of affect/emotion with things
What does the occipital lobe contain?
Visual cortices
What are the two streams of the occipital lobe?
-Dorsal stream - vision for movement
-Ventral stream - vision for identification
How does the brain control behaviour?
-Sensory + selection + skill + memory + thought + emotion + motor = behaviour
-All actions will engage a bit of cortex interacting with a bit of basal ganglia, cerebellum and hippocampus all directing brainstem what to do
What is dystrophin?
-Large protein
-Confers stability to muscle cell membrane
Describe neuromuscular transmission:
Describe the basic histology of a peripheral nerve:
What does this show?
Axons within nerves can be myelinated or unmyelinated
In the PNS what is responsible for the myelin sheath?
-Schwann cells
-Each Schwann cell is responsible for one segment of myelin
-Allows saltatory conduction
What lie in between adjacent myelin segments?
-Nodes of Ranvier
-Where depolarisation of the membrane occurs
-Saltatory conduction
Describe axonal degeneration/regeneration (Wallerian degeneration):
Describe demyelination:
What is the range of human hearing?
-20-20KHz
-Range change during life
What are the components of the auditory system?
-Outer ear: air
-Middle ear: air
-Inner ear: fluid
-Central auditory pathways
What makes up the outer ear?
-Pinna
-Ear canal
Describe the pinna:
-Cartilaginous structure
-Formed from pharyngeal arches 1 & 2 (6x Hillocks of His) - 10th to 18th week in utero
-Direct soundwaves towards ear canal
-High pitch > low pitch
Describe the ear canal:
-1/3 cartilage
-2/3 bone
Label the structures of the outer ear:
What is this?
Describe it:
-Tympanic membrane
-8 x 10mm diameter
-84-55mm2
What makes up the middle ear?
-Bones: malleus, incus, stapes
-Muscles: tensor tympani, stapedius
-Tubes: eustachian tube
What does this show?
Bones of the middle ear
What is the role of the middle ear?
Acoustic impedance match between air and fluid-filled inner ear
How does the middle ear carry out its role (bones)?
-Amplification of the airborne sound vibration = makes it louder
-Area TM: Stapes 14:1
-Lever action of ossicles - handle of malleus is 1.3x longer than incus process
-Total gain = 20-35Db (18.3:1)
What is the increase in pressure generated in the inner ear?
200 fold increase boost in pressure from TM to inner ear
What is the role of muscles in the middle ear?
-Protection of the inner ear from acoustic trauma
-Stiffens ossicular chain
-Stapedius stimulated acoustically
Describe the nervous control of the muscles in the middle ear:
-Reflex arc: 3 or 4 neurones
-25ms
-Voluntary and involuntary control of tensor tympani
What is the role of the eustachian tube?
-Ventilation of the middle ear space
-Drainage of secretions
-Often dysfunctional in children
Label the structures of the middle ear:
What is contained within the inner ear?
Vestibulocochlear apparatus
Describe the vestibulocochlear apparatus and its innervation:
-Set of fluid filled sacs encased in bone
-Cochlear - hearing
-Labyrinth - balance
-Innervation - vestibulocochlear nerve
Describe the cochlear:
-2.5 turns
-2 openings (round & oval window)
-3 compartments
-2 ionic fluids
What are the 3 compartments of the cochlea?
-Scala tympanin
-Scala media
-Scala vestibuli
What are the 2 cochlear fluids?
-Endolymph: High K+
-Perilymph: Like ECF & CSF Na+ rich
How are gradients of cochlear fluids maintained?
-Na, K-ATPase
-NKCC1, CIC-K chlorine channels
Label this diagram of the cochlea:
Describe the basilar membrane:
-Narrow at base - stiff - high frequency detection
-Wide at apex - floppy - low frequency detection
Label this diagram to represent movement in inner ear:
What is it called?
Organ of corti
What does the basilar membrane cause?
-Displacement of basilar membrane causes movement of specialised mechanical transducing cells
-Hair cells
What are the two types of hair cell?
-Inner - mechanical transduction
-Outer - fine tuning
What is the structure of the hair cell of the ear?
-Base attached to basilar membrane
-Stereocillia anchored to tectorial membrane
-Shearing forces at sterocillia
What does this show?
Inner hair cell
What are neurons and their propagation?
-Specialised for electrical signalling
-Mainly formed during development
-Input via dendrite
-AP propagate along axon from axon hillock
How do neurones communicate?
-Via synapses
-Chemical - majority: neurotransmitters
-Electrical - less abundant: direct flow of ions that enable synchronized electrical activity e.g. brainstem
Describe chemical synaptic transmission:
-Axon potential depolarises synaptic terminal membrane
-Voltage-gated calcium channels open leading to calcium influx
-calcium influx triggers neurotransmitter release
What is the structure of an electrical synapse?
-Gap junctions mediate
-Direct movement of ions between two cells
Where are excitatory synapses often concentrated?
Dendritic spines
What is neural plasticity and why is it important?
-Changes in neuronal/synaptic structure and function in response to neural activity
-Basis of learning and memory
Describe features of dendritic spines:
-Dynamic structures - number, size composition
-Spine remodelling linked to neural activity
-Lower spine density linked to disease
Describe neuron heterogeneity:
Neurons differ in their:
-Size
-Morphology
-Neurotransmitter content
-Electrical properties
What are 2 examples of neuronal heterogeneity?
-Betz cells: upper motor, large, excitatory, long, pyramidal
-Medium spiny neurons: striatal interneurons, small, inhibitory
What does this show?
Arborisation of axons and dendrites
What are oligodendrocytes?
-Myelinating cells of the CNS
-Provide metabolic support for axons
What does myelin do?
-Insulates axon segments enabling rapid nerve conduction
-Myelin sheath segments interrupted by nodes of Ranvier - saltatory conduction
-Provide metabolic support for axons
How is the myelin sheath formed?
-Wrapping of axons by oligodendrocyte processes (membranes)
-Highly compacted - 70% lipid, 30% protein
-Myelin specific proteins used as markers
What are microglia?
-Resident immune cells of the CNS
-Originate from yolk sac progenitors that migrate to CNS
Describe the states and actions of the microglia:
-“resting state” highly ramified, motile processes survey environment
-Upon activation, retract processes, become amoeboid and motile
-proliferate at sites of injury - phagocytic
What are 4 features of microglia?
-immune surveillance
-Phagocytosis - debris/microbes
-Synaptic plasticity - pruning of spines
-good M2 and bad M1 microglia
What are astrocytes?
-Star like cells
-Most numerous glial cells in CNS
-Highly heterogeneous
-Common marker glial fibrillary acidic protein
What are the 5 functions of the astrocyte?
-Structural - define brain micro-architecture
-Envelope synapses
-Metabolic upport
-Neurovascular coupling - changes in cerebral blood flow
-Proliferate in disease
What is a nuclei in CNS?
Abundance of cell bodies
What do axons gather into and what are these called when they cross the midline in CNS?
-Tracts
-Commissures
What is grey matter abundant in?
-Neural cell bodies and processes
-Neutropil contains few cell bodies
What is white matter abundant of?
Myelinated tracts and commissures
What do cell bodies form in the PNS?
Ganglia
What do axons bundle into in the PNS?
Nerves
What are many PNS axons enveloped by?
Schwann cells
What forms the blood/brain barrier?
-Endothelial cell tight junctions
-Basement membrane (few fenestrations)
-Astrocyte end feet
-Pericytes (contractile-aid blood flow)
Describe the blood/brain barrier’s features:
-Dyes in blood can’t penetrate
-Sensitive to inflammation, hypertension, trauma and ischaemia
-Problem for drug delivery
What is special about circumventricular organs in the brain?
-Lack normal BBB
-Homeostatic & endocrine functions
What are ependymal cells?
-Epithelial-like
-Line ventricles & central canal of spinal cord
What are the functions of the ependymal cells?
-CSF production
-Flow & absorption
-Ciliated to facilitate flow
-Allow solute exchange between nervous tissue & CSF
What is choroid plexus?
-Frond-like projections in ventricles
-Formed from modified ependymal cells - villi form around network of capillaries
-Highly vascularised
What is the function of the choroid plexus?
-Main site CSF production by plasma filtration driven by solute secretion
-Gap junctions between cells form blood-CSF barrier
Describe the conversion of waves to electrical current in the ear:
-Movement of stereocilia
-Rapid response
-Mechanically gated K+ channels open cause depolarisation
-Results in opening of Ca2+ channels
-Neurotransmitter released - glutamate
-Repolarisation through K+ eflux into perilymph
What do nerves respond to on a basic level and is this a fully sound model?
Ear
-Each nerve responds maximally at a specific frequency
-Ability to discriminate different frequencies not fully explained in this frequency
What can outer hair cells alter and why is this important?
-Alter the stiffness of basilar membrane
-Ensures maximal stimulation at one site and dampened response at another
-Increase resolution
How is frequency (pitch) encoded?
In nerves by location along the basilar membrane
How is intensity (loudness) encoded?
In nerves by numbers responding and by firing rate
How is sound transduction encoded?
Inner hair cells (and OHC)
How is sound amplification encoded?
Outer hair cells
What is the nerve pathway from the ear to the brain?
-Auditory fibre - spiral ganglion
-Spiral ganglion -> cochlear nerve (VIII)
-Central auditory pathway
Label this diagram:
Describe the central auditory pathway:
-Cochlea -> brainstem via VIIIth nerve
-Brainstem -> medial geniculate body
-Medial geniculate body -> auditory cortex
Label the central auditory pathway:
Label the brainstem part of the central auditory pathway:
What does ITD stand for?
Interaural Time Differences
What is the central auditory pathway?
-8th nerve
-Cochlear nucleus
-Olive
-Lateral leminiscus
-Inferior colliculus
-Medial geniculate
-Auditory cortex
What does a defective outer/middle ear cause?
-Conductive hearing loss
-Treatment involves improving conduction or amplification
What does a defective inner ear cause?
-Sensorineural hearing loss
-Amplify/stimulate
What are the 4 key features of the blood brain barrier?
-Endothelial cell tight junctions
-Lack of BM fenestrations
-Astrocytic end feet
-Pericytes
What do these show?
Arterial territories
What is venous drainage of the brain?
-Veins drain into sinuses channels between 2 layers of dura
-Superior sagittal sinus
-Inferior sagittal sinus
What is the general vasculature of the spinal cord?
-Anterior spinal artery + vein
-Posterior spinal artery + vein
-Anterior + posterior radicular artery
What separates anterior vs posterior communication of circulation?
-Anterior = anterior communicating artery
-Posterior = basilar artery
Label this diagram:
Label this diagram:
What does the ventricular system contain?
CSF
What does interstitial fluid drain into?
-Into CSF via perivascular channels
Drains back via:
-Via arachnoid granulations
-Peripheral nerves to lymphatics
-Nasal mucosa lymphatics deep cervical lymph nodes
What are ependymal cells?
Have cilia to move CSF
Where is CSF produced?
Choroid plexus
What is this?
Brainstem
Label this diagram:
What does it show?
Midbrain
Label the cerebellum divisions:
NOT LOBES
.
What is the function of the archicerebellum floculonodular lobe?
-Balance
-Connected to vesibular nuclei and reticular nuclei
What is the function of the paleocerebellum?
Muscle tone and posture
What is the function of the neocerebellum?
Movements, coordination, muscle tone
What is the limbic system involved in?
-Memory
-Motivation
-Emotion
-Fight or flight
What is the hippocampus involved in?
Laying down memories
What is this?
Hippocampus
What is the thalamus composed of?
3 main groups of nuclei:
-Sensory relays
-Cerebellar and basal ganglia relays to motor frontal lobe
-Connected to associative and limbic areas of cerebral cortex
What does damage to the thalamus result in?
Loss of sensation, pain or movement disorders
What are the pathways through the basal ganglia?
Direct and indirect pathways of basal ganglia
Describe the hypothalamus:
-Multiple inputs
-Sits on top of pituitary gland and tells it what to do
Label this diagram:
What is the role of the spinothalamic tract and its pathway?
-Crude touch
-Pain
-Temperature
INPUT PATHWAY
What is the role of the corticospinal (pyramidal) tract and its pathway?
Movement
SOLE OUTPUT PATHWAY
What is the role of the dorsal column-medial lemniscus pathway?
-Vibrations
-Joint position
INPUT PATHWAY
How many extraocular muscles are there and their general functions?
-7 muscles
-Control movement of eyes
-Allow us to move our eyes without moving our head
-Conjugate movements (coordinated movements of both eyes) allow us to form one image
Where are the extraocular muscles?
Inside the orbit - attached to the outer surface of the eyeball
What is the natural orientation of the orbit?
-Orbit axis is off to an angle
-Does not line up with the optical axis (eye looking straight ahead)
What are the 7 extraocular muscles?
-1 lifts upper eyelid = levator palpabrae superioris (LPS)
-6 move eyeball
-4 recti
-2 obliques
What 3 cranial nerves are involved in extraocular muscle innervation?
-3 cranial nerves
-CN III -> Oculomotor
-CN IV -> Trochlea
-CN VI -> Abducens
How do you remember what cranial nerves innervate what extraocular muscles?
LR6 SO43
-Lateral rectus 6 (abducens)
-Superior Oblique 4 (trochlea)
-All rest 3 (oculomotor)
What is the origin and insertion of the extraocular muscles?
-Attached to orbital bones
-Insert onto the sclera (except LPS)
-LPS inserts upper eyelid
What does how the extraocular muscles move the eye depend on?
-Where muscle originates
-Where it inserts on eyeball
-Determines which way it will pull eyeball when it contracts
What movements of extraocular muscles are possible?
-Some only move eye in one direction
-Some in more than one direction
-Movement of eye involve several muscles acting together
Label this diagram of eye movements:
What is significant about the direction of muscle fibres of the orbit?
-Apex of orbit lies medially so optical axis does not coincide with orbital axis
-Direction of muscle fibres do not coincide with optical axis
What does the levator palpebrae superioris do?
-Inserts into upper eyelid and elevates it
-Innervated by oculomotor nerve (CN III) and sympathetic fibres
What can CN III injury cause?
Describe the medial and lateral recti muscles:
-Both only one action
-Medial rectus - moves eye medially (adducts)
-CN III
-Lateral rectus - moves eye laterally (abducts)
-CN VI
What can oculomotor nerve lesion lead to?
-Medial rectus weak
-Unopposed pull of lateral rectus
-Eye deviates laterally
-Diplopia
What can an abducens nerve lesion lead to?
-Lateral rectus weakness
-Unopposed pull of medial rectus
-Eye deviates medially
-Diplopia
Describe superior and inferior recti:
-More complex primary and secondary actions
-Superior: 1o elevates eye, 2o and medially rotate
-Inferior: 1o eye, 2o abducts and laterally rotate
-Both CN III
Describe super and inferior oblique:
-Superior : 1o medially rotates eye, 2o depresses and abducts
-Inferior: 1o laterally rotates eye, 2o elevates and abducts
Do extraocular muscles work by themselves with example?
-No they work together
-Looking down shows antagonistic movements of So and IR
Label which muscles provide which ocular movements:
What does the inner ear contain?
-Cochlea = sound
-Vestibular apparatus = balance
Vestibular structures:
-utricle and saccule
-3 semicircular ducts containing fluid
How are the semicircular ducts orientated?
What do they do?
-At right angles to each other
-Semicircular ducts and utricle contain sense organs for balance
What is in the semicircular ducts and what do they drain into?
-Endolymph fluid
-Empty into a sac called the utricle
Explain the function of the semicircular ducts:
-Detect movement of the head
-Head moves in one direction
-Endolymph, cupula and hair cells in ampulla bend in opposite direction
-Info sent centrally via 8th CN from right and left semicircular ducts to nuclei in medulla
Label these structures:
Describe the signal pathways from semicircular ducts when they reach the brain:
-Reach nuclei in brainstem
-Connections control posture, balance and conscious awareness of position
-Nuclei make connections with nuclei of CN III, IV and VI
-Coordinated head and eye movement
What is this called?
-Oculocephalic reflex
-Maintain fixed gaze whilst head is moving
Describe the oculocephalic reflex:
-Normally when head rotates the eyes move in the opposite direction and the gaze remains fixed
-Used to assess vestibular apparatus and brainstem
-Absent = eyes move in same direction as head = brainstem lesion
What is diplopia?
Double vision
What happens at the third week of embryonic development?
Gastrulation:
-Ectoderm: skin, NS
-Mesoderm: Notochord, muscular system
-Endoderm: epithelial lining of gut + resp system, liver, pancreas
What is the first stage of the development of the spinal cord?
Ectoderm thickens in midline to form the neural plate
Describe the formation of the neural tube up until the end of the 4th week:
When does the neural tube close?
-Normally at the end of the 4th embryonic week
-Failure to close can cause abnormalities of spinal cord (anencephaly, spina bifida)
NEURAL TUBE DEFECTS
What are lateral to the neural groove?
Presumptive neural crest cells
Label this diagram:
What do cells of the neurual crest go on to form?
-Sensory dorsal root ganglia of spinal cord and V/VII/IX/X
-Schwann cells
-Adrenal medulla
-Bony skull
-Meninges
What stages of brain development do these show?
4 and 6 weeks
What structures are present in the developing brain at 4 weeks?
-Prosencephalon - cerebral hemispheres & thalamic structures
-Mesencephalon - midbrain
-Rhombencephalon - medulla, pons, cerebellum
Label this diagram:
What does it show?
Brain development at 4th week
What do microcephaly and macrocephaly mean?
Reduced or increased head circumference
What does the CSF circulate through and what is its volume?
-Through subarachnoid spaces and ventricles
-120mLs
How is CSF produced and what is its function?
Where is it absorbed?
-Produced as filtrate of blood at choroid plexus in ventricles
-Absorbed via arachnoid granulations in superior sagittal sinus
-Cushions brain and helps circulate metabolites
What is hydrocephalus?
-Accumulation of CSF with increased intracranial pressure
-Can cause macrocephaly in children
-Obstructive (non-communicating - tumour, haemorrhage) or non obstructive (increased production)
What are the causes and responses in stress?
-Cause = stressor
-Response = stress
What is stress?
-As a response it is often characterised as either somatic (physical) or psychological (mind)
-Overlap and mediated by brain
-Preceptions are both somatic and psychological - different connected neuronal networks
What is somatic (physical) stress?
-Physical, emotional and subjective experiences
-Associated with damage of body tissue and bodily threat (pain & inflammation)