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PreClinEazy X Cardiff Medsoc PCS 3 P art 1 Nada DahanStructure & function of the brainCerebrum, Cerebellum, Brainstem Cerebrum - Higher-order brain functions: conscious thought, emotion, memory, perception, and voluntary motor control. Cerebellum - Below the cerebrum - Ensures smooth coordinated muscle movement Brainstem - Midbrain - integrating visual, auditory, and motor information (arousal & alertness) - Pons - motor control, respiratory regulation, sleep regulation - Medulla - regulates essential functions: cardiovascular and respiratory activities, reflexes, and coordination of motor pathways.Cerebrum - Divided into L & R hemispheres (connected by corpus callosum) - outer layer: cerebral cortex (highly folded) - divided into 4 lobes Lateral sulcus = Sylvian fissureCorpus Callosum - Allows communication between L & R hemisphere Remember G Before SFunctional Brain Anatomy Executive function - higher level cognitive skills used to control other cognitive abilities and behavioursBrain Functional Areas ● Primary areas - directly receive sensory input or initiate motor outer, responsible for basic processing M1 - initiation and control of voluntary movements S1 - processes tactile info (touch, pressure, temperature, pain) ● Secondary areas: Integrate and interpret information from primary areas, contribute to more complex cognitive functions. M2 - planning, coordination, and execution of movements. They work in conjunction with the primary motor cortex. S2 - integrates and interprets sensory information received from the primary somatosensory cortex. Broca’s area - involved in speech production (expressive aphasia - BROken language) Wernicke’s area - involved in language comprehension (receptive aphasia) Pituitary glands not part of Diencephalon diencephalon but closely Limbic System associated anterior pituitaryterior pituitary - Part of forebrain - Consists of hypothalamus, thalamus, - Collection brain regions play important epithalamus, subthalamus - integration and regulation of various bodily role in emotion, motivation, learning & functions, sensory processing, and memory emotional responses. - thalamus, hypothalamus, - Pituitary secretes - GH, ADH etc hippocampus, amygdala Meninges Dura Mater Arachnoid Mater Pia Mater Outermost vascularised Middle avascular layer of Innermost highly vascularised thick tough layer of connective tissue - beneath layer. Very thin and tightly dense irregular tissue it is the subarachnoid space adheres to brain & spinal cord surface. Only surface to containing CSF (cushions the brain) contour gyri & sulci. Question 1 A patient with difficulty in forming grammatically A Expressive aphasia correct sentences is observed saying, "Want... coffee... table." When asked about their day, they Damage to the medulla respond, "Go... shop... yesterday." What is the B patient most likely presenting with? C Receptive aphasia D Lesion in the cerebellum E Global aphasia Question 1 A patient with difficulty in forming grammatically A Expressive aphasia correct sentences is observed saying, "Want... coffee... table." When asked about their day, they respond, "Go... shop... yesterday." What is the patient most likely presenting with? B Damage to the hippocampus Expressive = Broca’s aphasia C Receptive aphasia can comprehend what is being said but can not form proper sentences Receptive = Wernicke’s aphasia D Lesion in the cerebellum can form grammatically correct sentences but can not understand what is being said E Global aphasia Global problems with language comprehension & production Hippocampal damage - problem with memory formation Lesion in cerebellum - motor coordination & balance problems Question 1 Dr Ahmed is carrying out a craniotomy in which A Pia Mater part of the skull (bone flap) is temporarily B Subarachnoid Space removed to access the brain. Which layer is exposed following removal of the bone flap? C Dura Mater Arachnoid Mater D E Subdural Space Question 1 Dr Ahmed is carrying out a craniotomy in which A Pia Mater part of the skull (bone flap) is temporarily B Subarachnoid Space removed to access the brain. Which layer is exposed following removal of the bone flap? C Dura Mater Arachnoid Mater D E Subdural SpaceThe Nervous SystemSpinal Cord CS - Dorsal & ventral root form spinal nerve - Dorsal (sensory) - Ventral (motor) - white matter myelinated, opposite to brain (inside) - Cell bodies of many sensory neurons in dorsal root ganglion - Sensory neuron synapses with interneuron in grey matter - Interneuron sends signals across ascending tracts t to brain → can send signals through descending tractsSpinal Tract - 31 pairs of spinal nerves - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal - Nerve roots (dorsal & ventral) combine to form spinal nerves after leaving the spinal cord - Both para/sympathetic preganglionic fibres release acetylcholine Sympathetic: - Fight or flight (survival) - Postganglionic fibres: adrenergic fibres - release noradrenaline → bind to alpha & beta receptors - Some preganglionic fibres synapse directly to the adrenal medulla releasing adrenaline & norad Parasympathetic: - Rest & digest (dominant in resting state) - Postganglionic cholinergic fibres - release ACh→ bind to muscarinic receptors (GPCRs) Question 1 Which of the following best describes the primary A Constriction of bronchioles effect of stimulation of beta-1 receptors in the sympathetic nervous system? B Increased heart rate & contractility C Pupil dilation Inhibition of GI motility D E Decreased heart rate & contractility Question 1 Which of the following best describes the primary A Constriction of bronchioles effect of stimulation of beta-1 receptors in the sympathetic nervous system? B Increased heart rate & contractility Beta-1 receptors are predominantly located in the heart, and their activation by noradrenaline (released by sympathetic nerves) or C Pupil dilation adrenaline (released by the adrenal medulla) leads to positive inotropic (increased contractility) and chronotropic (increased heart D Inhibition of GI motility rate) effects. B1 (heart), B2 (lungs), alpha (vasoconstriction, pupil E Decreased heart rate & contractility dilation)the vertebrae and their supportivencluding structures. Contribute to formation of Area of skin supplied Group of muscles axial skeleton including by single sensory nerve innervated by a single vertebrae (embryonic root spinal nerve root development) Dermatomes Myotomes Sclerotomes Note: peripheral nerves are different to dermatomes as they cover larger areas → single peripheral nerve may innervate many dermatomesExteroreceptors in the Skin Exteroreceptors - sensory receptors that respond to stimuli from external environment Sensory Nerve Fibres A - Delta A - Beta C Fibres • Slow, unmyelinated ● Fast, myelinated • Fastest, myelinated • Responds to thermal, ● Transmit sharp, localised • Responds to non- pain & temperature in noxious stimuli mechanical and response to thermal, • Detects light touch & chemical stimuli mechanical noxious stimuli • 2ndary throbbing, vibrations burning, poorly ● 1st sharp pain sensation localised dull pain sensationSynaptic Transmission at NMJ -Neuro-muscular junction (synapse between motor neurone & muscle fiber (muscle contraction) - AP travels down motor neurone - Once reaches the axon terminal → depolarisation (voltage gated Ca2+ open) - Ca2+ influx triggers vesicles containing ACh to fuse with neuron membrane - ACh released into synaptic cleft binds to ligand gated ion channels (Na+ in, K+ out) → depolarisation (if reaches threshold → muscle contraction (travels along sarcolemma) Question 1 Lily gets a stung by a bee and immediately screams A A-delta then A-beta from the pain. She then feels a dull throbbing pain in the area. Which nerve fibres are responsible for her C fibres then A-delta B initial reaction & the subsequent dull pain? C A-beta then C fibres D A-delta then C fibres E Only A-beta Question 1 Lily gets a stung by a bee and immediately screams A A-delta then A-beta from the pain. She then feels a dull throbbing pain in the area. Which nerve fibres are responsible for her C fibres then A-delta B initial reaction & the subsequent dull pain? C A-beta then C fibres D A-delta then C fibres A-delta - initial sharp pain (fast, myelinated) → C fibres (slow, unmyelinated) secondary dull throbbing E Only A-beta pain Ascending P athways - Sensory pathways - pathways receiving sensory information from the periphery to the cerebral cortex - All enter via dorsal root & have 3 neuron pathways (orders) - Conscious tracts: Dorsal Column-Medial Lemniscus (DCML) & Spinothalamic tract (anterior/ lateral) (sensory information consciously perceived by individual) - Unconscious tracts: Spinocerebellar pathway Ascending P athways Cont. ● DCML - carries information related to fine touch, vibrations, conscious proprioception (awareness of body’s position in space) ● Spinothalamic Tract - Anterior: Crude touch & pressure - Lateral : Pain & temperature ● Spinocerebellar Pathway - Unconscious proprioception & crude touch Dorsal Column Medial Lemniscus • 1st order neurones carry sensory info from peripheral nerves to nucleus cuneatus/ gracilis of the medulla oblongata where they synapse - T6 & above - travels in the fasciculus cuneatus - below T6 -fasciculus gracilis ● 2nd order neurones decussate (cross to other side of CNS). Travel in the contralateral medial lemniscus to reach Contralateral - opposite side the thalamus Ipsilateral - same side ● 3rd order neurones transmits sensory signal from thalamus → ipsilateral primary sensory cortex of the brain The Anterolateral System •1st order neurones arise from sensory receptors in periphery, enter spinal cord, ascend 1-2 vertebral levels. Synapse at the tip of the dorsal horn (substantia gelatinosa) • 2nd order neurones carry sensory info from substantia gelatinosa → thalamus. At the SG these fibres decussate within the spinal cord forming 2 spinothalamic tracts: - Crude touch & pressure fibres enter anterior ST - Pain & temperature fibres enter lateral ST ● 3rd order neurones carry sensory signals Spinothalamic crosses over from thalamus to the ipsilateral primary before ascending to the brain, sensory cortex. DCML crosses after!! Descending P athways - Pyramidal tracts - tracts originating in cerebral cortex, carry motor fibres to spinal cord & brain stem (responsible for voluntary control of musculature of body & face) - Extrapyramidal tracts - tracts originating in brain stem, carry motor fibres to spinal cord. (responsible for involuntary & automatic control of all musculature e.g. muscle tone, balance & posture) ● Descending pathways primarily involve a direct connection between upper and lower motor neurons Motor Neurones Upper Lower • Located in PNS • Located in CNS • Directly innervates muscles, pass • Conveys signal from brain to lower motor neuron signal from CNS to muscles causing movement • Important in initiation & modulation of voluntary movements Corticospinal Tract ● Upper motor neurons originate in the motor cortex in the cerebral cortex ● Neurones descend as the corticospinal tract down through the midbrain into the medulla oblongata ● In medulla about 90% of the tracts decussate to the contralateral side of the medulla (become lateral corticospinal tract) Significance: Stroke R side → - UMN synapse with LMN in ventral (anterior) grey horn of the spinal cord leaves out of spinal cord via ventral left skeletal root to skeletal muscle → contraction muscles -ve - Contralateral control of distal limb muscles (hands, impact. Distal muscles ↑ than feet etc) ● 10% remain on the same side (continue ipsilaterally as postural as only the anterior corticospinal tract) control through R side of brain - Bilateral innervation of neck, shoulders, trunk (postural muscles)Brown Sequard Syndrome Pain & temperature → contralateral at the level it enters Movement & fine touch → decussate at the medulla same side of lesion below level of damage → problems with fine touch & motor movement Hand will feel pain & temperature as this pathway is on the opposite side of the spinal cord to the lesion weakness or paralysis on one side of the body and a loss of sensation on the opposite side.Upper & Lower Motor Lesions - Spastic paralysis - constant muscle contraction Flaccid paralysis - muscles cannot contract (floppy & immobile) Hyperreflexia - heightened muscle reflex Clonus -rhythmic involuntary muscle contraction & relaxation in response to sustained muscle stretching Fasciculations - spontaneous brief & involuntary contractions of a small group of muscle fibers. Question 1 In the Dorsal Column Medial Lemniscus pathway A Fasciculus cuneatus what does the 1st order neurones synapse with if the sensory information comes from below T6? B Nucleus gracilis C Thalamus Fasciculus gracilis D E Substantia gelatinosa Question 1 In the Dorsal Column Medial Lemniscus pathway A Fasciculus cuneatus what does the 1st order neurones synapse with if the sensory information comes from below T6? B Nucleus gracilis C Thalamus Fasciculus gracilis D E Substantia gelatinosa Question 1 A 65-year-old man presents with muscle weakness, A Located in CNS muscle atrophy, and weakness. Upon investigation, he exhibits a negative Babinski sign. What is accurate regarding the type of motor neuron affected by the Conveys signal from brain → LMN lesion? B C Initiates and modulates movement D Indirectly innervates muscles E Passes signal from CNS → muscles Question 1 A 65-year-old man presents with muscle weakness, A Located in CNS muscle atrophy, and weakness. Upon investigation, he exhibits a negative Babinski sign. What is accurate regarding the type of motor neuron affected by the Conveys signal from brain → LMN lesion? B C Initiates and modulates movement D Indirectly innervates muscles E Passes signal from CNS → musclesTHANK YOU! ANY QUESTIONS?References https://www.myshepherdconnection.org/disorders-consciousness/Intro-disorders-of-consciousnes s/brain-anatomy https://www.researchgate.net/figure/Quantitative-tractography-of-major-white-matter-tracts- measured-in-this-study-Examples_fig1_286444337 https://teachmeanatomy.info/neuroanatomy/brainstem/midbrain/ https://www.medicinehack.com/2011/07/plantar-reflex-babinskis-sign.htmlPLEASE FILL OUT THE FEEDBACK FORM PLEASE TUNE IN TO OUR REMAINING SESSIONS THIS WEEK