Brain and Behaviour Flashcards
Anterior cranial fossa bones and contents
Bones = frontal, ethmoid, sphenoid Contents = frontal lobes
Middle cranial fossa bones and contents
Bones = sphenoid, temporal Contents = temporal lobes, pituitary gland
Posterior cranial fossa bones and contents
Bones = sphenoid, temporal, parietal, occipital Contents = brainstem, cerebellum
Accessory nerve innervation
SCM and trapezius
Foramen spinosum
Middle meningeal artery
What the sympathetic nerve can do once it has entered the sympathetic trunk
Synapse
Ascend or descend
Leave
Conus medullaris
End of the spinal cord at L2
Where is a lumbar puncture performed?
Between L3&4 or L4&5
Rexed laminae I-II
Pain
Rexed laminae III-IV
Exteroception
Rexed laminae V-VI
Proprioception
Circulation of aqueous humour
Produced in ciliary body
Passes out of posterior chamber through the pupil and into the anterior chamber
Drains out the canal of Schlemm (scleral venous sinus)
Vitreous chamber function
Helps to preserve the shape of the eyeball to maintain focussing precision
Orbicularis occult innervation
CN VII
Superior rectus action
Elevation, adduction
Inferior rectus action
Depression, adduction
Superior oblique
Depression, abduction, intorsion
Inferior rectus
Elevation, abduction, extorsion
Papilloedema
Swelling of the optic disc
Sign of raised ICP
Partial optic nerve lesion
Ipsilateral scotoma
Optic nerve lesion
Monocular blindness
Optic chiasm lesion
Bitemporal hemianopia
Optic tract lesion
Homonymous hemianopia
Meyer’s loop lesion
Homonymous upper quadrant hemianopia
Optic radiation lesion
Homonymous hemianopia with macular sparing
Parasympathetic innervation of CN III
Sphincter pupillae
Ciliary muscle
Parasympathetic innervation of CN VII
Lacrimal glands
Mucosal glands of the nasal and oral cavities
Submandibular and sublingual glands
Parasympathetic innervation of CN IX
Parotid gland
Horner syndrome symptoms
Miosis - contraction of the pupil
Ptosis - eyelid droop
Anhydrous - lack of sweating on face and neck
Exophthalmos - sinking of the eye
Dural venous sinus location
Between periosteal and meningeal dural layers
What is found in the cereal ventricles that is responsible for producing CSF?
Choroid plexus
Path from lateral ventricles –> subarachnoid space
Lateral ventricles
Interventricular foramen
Third ventricle
Cerebral aqueduct
Fourth ventricle
Then either central canal –> film terminal –> subarachnoid space
Or cisterna magna –> median and lateral aperatures –> subarachnoid space
CSF function
Buoyancy
Protection from trauma
Brain nourishment
How is CSF absorbed into the venous system
Via subarachnoid granulations that project into the superior sagittal sinus and other dural venous sinuses
Where is the fourth ventricle found?
Between the brainstem and cerebellum
What forms the lateral borders of the third ventricle?
Thalamus on either side
What is found superior to the third ventricle?
Corpus callosum
Where are the 3 horns of the lateral ventricles found?
Anterior = frontal lobes Inferior = temporal lobes Posterior = occipital lobes
What is the condition in which there is an excessive accumulation of CSF?
Hydrocephalus
Anterior cerebral artery supplies…
Midline of the brain
Middle cerebral artery supplies…
Lateral 2/3 of the brain
Including Broca’s and Wernicke’s areas and the auditory cortex
Posterior cerebral artery supplies…
Bottom of the brain
Mainly occipital lobes and including visual cortex
Borders of the posterior triangle of the neck
Posterior border of SCM
Anterior border of trapezius
Middle 1/3 of clavicle
Contents of the posterior triangle of the neck
Spinal accessory nerve External jugular vein Subclavian artery Brachial and cervical plexuses Lymph nodes
Borders of the submandibular triangle
Mandible
Anterior belly of digastric
Posterior belly of digastric
Submandibular triangle contents
Submandibular gland
Hypoglossal nerve
Facial artery and vein
Carotid triangle borders
SCM
Posterior belly of digastric
Omohyoid
Carotid triangle contents
ICA CN X, XI, XII IJV Carotid body and sinus Ansa cervicalis
Muscular triangle borders
Hyoid
Omohyoid
Midline of the neck
SCM
Muscular triangle contents
Infrahyoid muscles
Thyroid gland
Parathyroid glands
Submental triangle borders
Hyoid
Anterior belly of digastric
Midline of the neck
Submental triangle contents
Mylohyoid
Carotid sheath contents
Common carotid artery ICA IJV Vagus nerve Ansa cervicalis Sympathetic trunk
Muscles of the pharynx
3 constrictor muscles - superior, muddle and inferior
Palatopharyngeus
Salpingopharyngeus
Stylopharyngeus
Innervation of the pharyngeal muscles
Pharyngeal plexus of vagus nerve
Except stylopharyngeus which is supplied by the glossopharyngeal nerve
Internal laryngeal nerve
Sensory to larynx above vocal folds
Lesion damages cough reflex
External laryngeal nerve
Motor to cricothyroid
Lesion produced monotonous voice
Recurrent laryngeal nerve
Motor to all muscles of the pharynx except cricothyroid
Sensory to larynx below vocal folds
Lesion produces dysphonia
Bones of the orbit
Maxillary, frontal, zygomatic, sphenoid, ethmoid, lacrimal
Orbital foramina
Optic canal = optic nerve and ophthalmic artery
Superior orbital fissure = CN III, IV, VI, VI
MCA stroke
Global aphasia if dominant hemipshere
Sensorimotor loss on contralateral face, upper limbs and trunk
neglect syndrome if non-dominant side
ACA stroke
Contralateral sensorimotor loss below waist
Urinary incontinence
Personality defects
Split brain syndrome
PCA stroke
Contralateral homonymous hemianopia
Reading and writing deficits
Impaired memory
Lateral medullary syndrome
Affects PICA
Vertigo, nystagmus, nausea, dysphonia, dysphagia, loss of gag reflex
Horner syndrome
Diencephalon
= thalamus and hypothalamus
Mesenchaplon
= midbrain
Locus coeruleus
Pons
Noradrenaline
SNS control and pain inhibition
Raphe nuclei
Throughout the brainstem
Serotonin
Arousal, cognition, mood
Damage –> OCD, depression, anxiety
Substantia nigra
Midbrain
Dopamine
Control of movement initiation and switching
Damage –> Parkinson’s disease
Ventral tegmental aera
Midbrain
Dopamine
Organising behaviours, reward, attention, motivation
Damage –> schizophrenia, addiction
Pedunculopontine nucleus
Pons
Acetylcholine
Types of brain herniation
Subfalcine - brain moves under falx cerebri
Uncal - temporal lobe moves down and compresses midbrain
Tonsillar - brainstem moves down through foramen magnum
CN III palsy
Eye in down and out position
Ptosis
Dilated pupil
CN IV palsy
Eye slightly elevated and adducted
Tilting of head due to loss of intorsion
Complain of neck pain and have problems walking down stairs
CN VI palsy
Abduction in affected eye not possible
Ependymal cells
Line the ventricles
Function in the circulation of CSF
Ciliated and appear like epithelial cells
Astrocytes
Most common glial cells
Provide structural and metabolic support to neurones
Help form the BBB
Forms scars in areas of damage
Microglia
Immune cells of the CNS - immune surveillance
Small cells with long spiny processes
Oligodendrocytes
Myelinating cells of the CNS
Each cell can myelinate up to 60 neurones
Schwann cells
Myelinating cells of the PNS
Each cell can only myelinate one axon
Contents of the axoplasm
Mitochondria for energy
Microtubules to maintain shape
Satellite cells
Supporting cells of the PNS
Found in dorsal root ganglia
What sensory modalities are carried by the DCML pathway?
Conscious proprioception
Discriminative touch - touch, pressure, vibration
What sensory modalities are carried by the spinothalamic tract?
Pain and temperature
Crude touch and pressure
What sensory modalities are carried by the spinocerebellar tract?
Unconscious proprioception
What does the corticospinal tract convey?
Control of voluntary movement
Where does the DCML pathway decussate?
High in the medulla after the primary neurone has synapsed in the gracile/cuneate nucleus
Where does the spinothalamic tract decussate?
Low in the spinal cord, around 1-2 levels above where the nerve entered through the spinal root
It is the secondary afferent that decussates after the primary afferent synapses in the dorsal horn
Where does the spinocerebellar pathway decussate?
It doesn’t –> ipsilateral cerebellum
Where does the corticospinal decussate?
At the spino-medullary junction
Superior colliculus function
Visual tracking and attention
Inferior colliculus function
Auditory reflexes
Inferior olivary nucleus
Nucleus found in the rostral medulla
Important projection to the cerebellum
What is found dorsally in the brainstem?
Cranial nerve nuclei
Motor found medially
Sensnory found laterally
What is found down the middle of the brainstem?
Ascending pathways
Reticular formation
What is found ventrally in the brainstem?
Descending pathways
Reticular formation roles
Arousal responses
Autonomic nervous system control
Control fo muscle tone and reflexes
Pain modulation
MLF location and function
Throughout the brainstem, roughly in the middle
Connects gaze centres and vestibular system
Periaqueductal grey location and function
Surrounding the cerebral aqueduct
Descending pain control
Regulation of autonomic functions
Substantia nigra location
Rostral midbrain
Where is the fourth ventricle at its widest point?
At the junction between the pons and medulla
Where is the spinal nucleus of the trigeminal nerve found and what is its function?
Rostral medulla
Receives pain and temperature information from the head
Jaw jerk reflex
Afferent = CN V3 Efferent = CN V
Symptoms of Parkinson’s disease
Tremor, rigidity, gait abnormalities, slurred speech
Where does the damage in Parkinson’s disease occur?
Substantia nigra
Parkinson’s disease treatment
Dopamine receptor agonists
L-dopa + enzyme inhibitor of decarboxylase enzyme (so only converted in the brain)
Schizophrenia symptoms
Hallucination, delusions, social withdrawal, paranoia
Pathology of schizophrenia
Hyperactivity of ventral striatum
Increased dopamine release
Treatment of schizophrenia
Dopamine receptor antagonists
Pathology of depression
Dysfunction of monoamine system in the brain
Deficiency of serotonin and noradrenaline
Treatment of depression
Re-uptake inhibitors
How does ecstasy work?
Increases monoamine release
How does cocaine work?
Inhibits monoamine reuptake
How does heroin work?
Mu opoid receptor antagonist
How does ketamine work?
Glutamate receptor antagonist
How does nicotine work?
Nicotinic cholinergic receptor agonist
How is alcoholism treated?
Disulfiram
Makes alcohol consumption unpleasant and painful
Where in the meninges are blood vessels found?
Within the dura and arachnoid
Epidural haemorrhage
Bleeding outside the dura
Usually arterial
No symptoms initially
Severe headache later as haematoma compresses brain
Subdural haemorrhage
Bleeding between the dura and arachnoid
Usually from bridging veins
Slow onset of symptoms
Imaging shows blood spread diffusely over brain surface
Subarachnoid haemorrhage
Bleeding into the subarachnoid space
Often from ruptured aneurysm
Sudden severe thundercap headache
CSF production rate
500ml/day
Common site of blockage in hydrocephalus
Cerebral aqueduct
What contributes to the BBB
Astrocyte end feet
Tight junction system between endothelial cells of the cerebral capillaries
Broca’s Broadmann area
44 and 45
Wernicke’s Broadmann area
22
Broca’s damage
Expressive aphasia
Halting speech with disordered word order and grammar
Wernicke’s damage
Receptive aphasia
Fluent but meaningless speech
What connects Broca’s and Wernicke’s areas?
Arcuate fasciculus
Arcuate fasciculus damage?
Conduction aphasia
Difficulty repeating words
Difficulty reading aloud
Right Broca’s equivalent damage
Aprosodia
Difficulty understanding the non-semantic aspects of speech such as intonation, emphasis and rhythm
Produce robotic and monotonous speech
Left vs right frontal lobes
Left focuses attention on one aspect
Right maintains an overall vigilance of your surroundings
Left vs right hemispheres
Left good at deductive reasoning
Right good at inductive and intuitive reasoning
Left inferotemporal cortex damage
Associative agnosia
Cannot assign names to objects
Right inferotemporal cortex damage
Apperceptive agnosia
Cannot recognise objects when in an unusual rotation or shadow
Fusiform gyrus damage
Prospoagnosia
Cannot assign names to faces
Primary motor cortex Broadmann area
4
Primary somatosensory cortex Broadmann area
1,2,3
Primary visual cortex Broadmann area
17
Primary auditory cortex Broadmann area
41,42
Right posterior parietal cortex function
Separates what we see into the background and what is part of the object
Right posterior parietal cortex damage
Piecemeal perception - can only observe one object at a time
Constructional apraxia - difficulty building 3D objects
Optic apraxia - inaccuracies reaching for objects
Discalculia - difficulty counting
Contralateral disregard - ignores left side of the body
Balint’s syndrome
Bilateral lesions of the posterior parietal cortex
Appear blind - bump into objects etc
Can describe a small area in great detail
Oculomotor apraxia and simultanagnosia
Where does recall from long term memory occur?
Parts of the temporal lobes
Orbitofrontal cortex
Control of acceptable behaviours and awareness of social norms
Hypothalamic outputs
Neural signals via the ANS
Endocrine through the pituitary gland
Cavernous sinus contents
ICA, CN III, IV, V1, V2, VI
Hypothalamic nuclei involved in ADH release
Supraoptic
Paraventricular
What does the posterior pituitary secrete?
ADH
Oxytocin
What stimulates adrenocorticotrophic hormone release/
Corticotrophin releasing hormone
Types of nerve regeneration
Anterograde (Wallerian)
Retrograde (to the cell body)
Transneural
Where are sensory receptors found in the skin?
At the epidermal-dermal junction
alpha A neurones
Alpha motor neurones
1a muscle spindle afferernts
1b golgi tendon afferent
beta A neurones
General sensory afferents
gamma A neurones
Gamma motor neurones to muscle spindle
delta A neurones
Fast pain
Thermoception
C fibre neurones
Slow pain
Thermoception
Spatial vs temporal summation
Spatial = more than one EPSP at a time Temporal = two EPSPs in close proximity to one another
Where is osmolaity detected?
Subfornical organ in the wall of the third ventricle
Where does the subfornical organ project to?
Medial preoptic nucleus to induce thirst sensation
Paraventricular and supraoptic nuclei to induce ADH release
Effects of ADH
Additional aquaporins to move into the membrane of the collecting duct
Increases collecting duct permeability to urea
Stimulates sodium reabsorption in the thick ascending loop of Henle
Lateral vs medial hypothalamus in maintenance of body weight
Lateral = hunger centre Medial = satiety centre
Which nucleus is the satiety centre?
Periventricular nucleus
Where are internal hunger/satiety cues detected?
Arcuate nucleus of the hypothalamus
Ghrelin
Hunger hormone
Released by cells in the fundus of the stomach
Acts on a GPCR and induces eating behaviours
Also stimulates the dopamine pathway responsible for the enjoyment of food
Leptin
Released from adipose tissue
Acts to reduce hunger
Gives the brain an overall idea of the total amount of adipose tissue in the body
Acts as a long-term regulator rather than a satiety signal
CCK
Released by duodenal cells in response to chyme from the stomach
Causes released of digestive enzymes and bile
Acts on the arcuate nucleus to induce satiety
GLP1
Glucagon like peptide 1
Released as a consequence of food in the gut
Induces satiety
Induces insulin secretion
In what nerves do the sympathetic efferents to the bladder travel?
Hypogastric nerve
Action of sympathetic efferents on the urinary system
Maintain tonic contraction of the internal urethral sphincter via alpha receptors
Tonically inhibit the contraction of the detrusor muscle via beta receptors
What happens when the bladder becomes stretched?
Activation of pelvic nerves
Sense of bladder fullness via spinothalamic tract
What nerve controls the external urethral sphincter?
Pudendal
Where is the micturition centre?
Barrington’s nucleus in the pons
Describe the micturition reflex
Descending fibres in the reticulospinal tract inhibit sympathetic and somatic outputs controlling the urethral sphincters
Activation of parasympathetic efferents which stimulate the contraction of the detrusor muscle via M3 receptors
Ano-rectal reflex
Activated by stretching of the rectal afferents
Inhibition of sympathetic nerves to cause relaxation of the internal anal sphincter
Pressure increases on external anal sphincter and triggers the urge to defecate
Process of defecation
Allow external anal sphincter to relax
Faeces moves down
Upper rectum contracts to propel the faeces out of the anal canal
Ready, steady, go in movement
Ready = posterior parietal cortex Steady = association motor cortex Go = primary motor cortex
3 parts of the cerebellum
Vestibulo = balance and posture Spino = locomotion Cerebro = skilled motor tasks
Cerebellum damage
Ataxia and hypotonia
Basal ganglia damage
Slowing or unwanted movements - hypo/hyperkinesia
Association motor cortex damage
Apraxia - unable to execute familiar, learned movements
Descending motor pathways damage
Spasticity and hypotonia
Spasticity vs rigidity
Both increase in muscle tone
Spasticity due to loss of inhibition of gamma motorneurones
Rigidity due to loss of inhibition of alpha motorneurones
Flaccidity
Occurs when LMNs or peripheral nerves are damaged
CNS excitatory NTs
ACh
Glutamate
CNS inhibitory NTs
GABA - brain
Glycine - spinal cord
Function of gamma motor neurones
Alter the sensitivity of the muscle spindles
Golgi tendon organ reflex arc
1b afferent
Glycinergic inhibitory interneurone
Alpha motorneurone
Flexion reflex arc
Delta A nocioceptor afferent
2-3 excitatory interneurones
Alpha motor neurone
Pacinian corpuscle
Vibration
Ruffini ending
Pressure or skin stretching
VPM vs VLP
VMP = information from the face VPL = information from the limbs
What happens in the VPL?
Convergence of the DCML and anterior spinothalamic pathways
Where does the lateral spinothalamic tract project to?
Limbic system - pain and pleasure
Midbrain reticular formation - pain induced arousal
Intralaminar nuclei of the thalamus - focusing attention on pain
Blink reflex
Input = V1 Output = VII to orbicularis oculi
Pupillary light reflex
Input = CN II Output = CN III parasympathetic portion to the pupillary constrictor muscle
What drug blocks the pupillary light reflex?
Atropine
Components of the accommodation reflex?
Pupillary constriction - improves focusing by increasing depth of field
Thickening of the lens - allows focusing on near objects
Convergence - simultaneous contraction of medial rectus muscles
Vestibulo-ocular reflex
Input = CN VIII Output = CN III and CN VI
Contents of tears
Mucous
Antibodies
Lysozyme
Layers of the eye
Outer = sclera and cornea Middle = iris, ciliary body and choroid Inner = retina
What is the primary refractive surface of the eye?
Cornea
What is normal intra-ocular pressure?
10-21mmHg
Where is visual acuity the highest?
At the fovea
Circulation of aqueous humour
Ciliary body –> posterior chamber –> pupil –> anterior chamber –> canal of Schlemm
Glaucoma
Increase in intraocular pressure that damages the retina
Open angle glaucoma
Progressive condition
Trabecular meshwork over canal of Schlemm becomes gradually blocked
Angle between cornea and iris remains normal around 40 degrees
Primary angle glaucoma
Sudden blockage of canal of Schlemm
Rapid rise in pressure
Sudden loss of vision and extreme pain
Angle between cornea and iris is reduced
Glaucoma treatments
Prostaglandin analogs
Beta adrenergic receptor antagonists
Alpha-2 agonists
CA inhibitors
How do cataracts form?
Level of antioxidants is too low or too much UV exposure
Lens becomes opaque
Protein found in rods
Rhodopsin
Protein found in cones
Iodopsin
How does light affect photoreceptors?
Light hyperpolarises the cell
Stops the tonic glutamate release
Dual blood supply of the eye
Central ophthalmic artery
Choroid network of capillaries from ophthalmic artery
From photoreceptor –> optic nerve
Photoreceptor –> bipolar cell –> ganglion cells –> optic nerve
Organ of Corti hair cells
3 rows of outer hair cells –> amplification of sound signals
1 row of inner hair cells –> auditory discrimination
Apex vs base of cochlea
Apex is thin and wide –> responds to low frequency sounds
Base is thick and narrow –> responds to high frequency sounds
Impedance matching factors
Relative sizes of ear ossicles
Tympanic membrane larger than oval window
Attenuation reflex
Activated by own voice or loud sounds
Contraction of muscles like stapedius to dampen middle ear transmission
50-100ms delay
Startle reflex
Defensive response against threatening stimuli
Involves facial nerve and reticular formation
Less than 10ms latency period
Rinne’s test
Tuning fork on mastoid process then by ear canal
Weber’s test
Tuning fork on forehead
Angular gyrus damage
Alexia and agraphia - can’t read or write
