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Year 1: The Nervous System Laura McCafferty - 4th year 2365005ILOs ● The Central Nervous System ○ Structure and function of the brain ■ Cerebral hemispheres ■ Lobes ■ Brainstem ■ Cerebellum ○ Structure and Function of spinal cord ○ Major cell types ■ Different structures and functions ■ Grey vs white matter ○ Meninges ○ Function, production, and composition of CSF ○ Blood Brain Barrier ● The Peripheral Nervous System ○ The Autonomic Nervous system ■ Sympathetic and parasympathetic divisionsThe Nervous System ● CNS ○ Brain ○ Spinal cord ● PNS ○ Cranial nerves ■ 12 pairs ○ Spinal nerves ■ 31 pairs ● Somatic = skin, skeletal, joints, tendons ● Visceral = smooth muscle, cardiac muscle, glandsBrain Structure ● Telencephalon “telos end, last part to develop in humans” ○ Cerebral cortex ○ Basal ganglia ○ Hippocampus ○ Amygdala ● Diencephalon - “dia- passing through or between diameter” ○ Thalamus ○ Hypothalamus ● Mesencephalon “mesos middle”“ ○ Tectum ○ Tegmentum ● Metencephalon “behind”, metacarpal” ○ Pons ○ Cerebellum ● Myelencephalon “myelo- marrow, refers to spinal cord” ○ MedullaTelencephalon - Cerebrum ● 2 hemispheres divided by sagittal/longitudinal fissure ○ Connected by corpus callosum - myelinated axons horizontally linking fissures ● 4 primary cortical lobes ○ Frontal ■ Voluntary motor control ■ Personality ■ Working memory ○ Parietal ■ Sensory input ○ Occipital ■ Visual input and processing ○ Temporal ■ Auditory input ■ Spoken and body language ● Basal Ganglia ○ Gray matter mass in each cerebral hemisphere ○ Control of voluntary muscle movements ● Limbic system (in cerebral cortex and extends into diencephalon) ○ Amygdala - emotions ○ Hippocampus - learning and memoryDiencephalon + Cerebellum ● Diencephalon ○ Contains ■ Thalamus ■ Hypothalamus ○ Functions ■ Endocrine ■ Emotions and memories ■ Relay centre ■ Autonomic functions of PNS ● Cerebellum ○ Coordinates motor activities ○ Processes muscle positionBrain Stem ● Brain stem ○ Midbrain ■ Contains centres for visual and hearing reflexes ■ Origin of 2 cranial nerves ○ Pons ■ Origin of 4 cranial nerves ○ Medulla oblongata ■ Continuous with spinal cord ■ Allows communication between spinal cord and brain ■ 3 important function centres ● Cardioinhibitory = HR regulation ● Respiratory = RR regulation ● Vasomotor = Blood vessel regulation ■ Origin of 5 cranial nervesSpinal Cord ● Spinal nerves ○ 31 bilateral pairs ■ 8 cervical ■ 12 thoracic ■ 5 lumbar ■ 5 sacral ■ 1 coccygeal ○ Dorsal = sensory ○ Ventral - motor ● Enlargements ○ Cervical Plexus ○ Lumbar Plexus ● Conus medullaris ○ Conus termination ○ L1-L2 in adults ○ L3/L4 infants ● Filum terminale ○ Strand of connective tissue from tip of conus ● Cauda equina ○ Below termination of cord ● Intervertebral discs ○ Fibrocartilaginous discsCell Types ● Grey matter ○ Nerve cell bodies, dendrites ● White matter ○ Axons ○ Looks white due to myelin sheathing coating axons ● Glial cells ○ Support and nutrition ○ Astrocytes ■ Form BBB ○ Microglia ■ Defence ○ Ependymal cells ■ Production of CSF ○ Oligodendrocytes ■ Myelin formation in CNS ○ Schwann cells ■ Myelin formation in PNSNeurons ● Bipolar ○ Interneurons ○ Two cytoplasmic extensions ■ One axon and one dendrite ○ Sensory ■ Found in retina, nasal cavity, inner ear ● Unipolar ○ AKA pseudounipolar // sensory neurons ○ Cell body sitting atop an axon ■ Divides axon into peripheral process (dendrites, usually long) and central process ■ Most common sensory neuron ● Multipolar ○ AKA motor neurons ○ Three or more processes ■ One axon, remaining dendrites (think increased surface area to receive information) ■ Usually long axons covered by Schwann cells ● Pyramidal cells ○ Upper motor neurons in motor cortex of brain and carry potentials to spinal cordMeninges ● Dura mater ○ Tough and fibrous ○ Two layers ■ Periosteal: Outer is stuck to the inside of the skull (does not continue to spinal cord) ■ Meningeal: continuous with dura mater at spine ■ Space between forms venous sinuses ● Arachnoid mater ○ Spider ● Pia mater ○ Gentle ○ Thin and veil likeBrain Spaces ● Epidural ○ Above the dura mater ○ Contains meningeal arteries in the brain ○ Contains fat and venous plexus in spinal cord ● Subdural ○ Below the dura ○ Bridging veins connect to venous sinuses ● Subarachnoid space ○ CSF and cerebral arteries and veins CSF ● Functions ○ Cushioning ○ Reduce pressure of brian on vessels and nerves inferiorly ○ Fluid delivery system for chemical mediators ○ Paracrine communication ○ Stable chemical environment ○ Nutrient and waste exchange with the blood ● Location of production ○ Ependymal cells of choroid plexus in lateral and 4th ventricles ● Passage ○ Ventricles → subarachnoid space (brain and spinal cord)→ dural venous sinuses → blood circulationBlood Brain Barrier ● Function ○ Maintains special chemical environment of nervous tissue ■ Brain requires specific concentration of ions, nutrients, and metabolites ○ Stop bad substances from entering brain and spinal cord from blood ■ Water, small lipophilic (i.e. can cross basement membranes)l molecules and gases can enter passively ■ Active transport carriers across substances such as glucose and amino acids ■ Many drugs cannot pass through the blood brain barrier ● Structure ○ Capillaries ■ Tight junctions between endothelial cells ■ Thick, continuous basement membrane ■ Astrocyte processes cover vessels ○ Epithelial cells ■ Line ventricles and spinal canal ■ Contain tight junctions ○ Areas with higher permeability ■ Sensory functions e.g. medulla detects toxins→ vomiting ■ Secretory functions e.g. pituitary→ hormone secretion Peripheral Nervous System - neurons ● Neurons can be classified by: ○ whether they innervate somatic (skin, skeletal muscles, tendons, joints), or visceral (smooth muscle, cardiac muscle, glands) tissue ○ and whether they are travelling towards (afferent) or away (efferent) from the brain Somatic Visceral Afferent (sensory) Touch, temperature, pain Enteroreceptors or visceroreceptors Body position and movement Pain, temperature, nausea Hearing and vision Smell and taste Efferent (motor) Skeletal muscle Visceral muscle (smooth, cardiac) and glands Makes up autonomic nervous system - divided into sympathetic and parasympathetic Autonomic Nervous System ● Sympathetic “fight or flight” ○ Thoracolumbar, T1-L2/L3 in origin ○ Short preganglionic fibre → synapse in sympathetic ganglia→ long postganglionic fibre → organ ○ ACh preganglionic synapse and A/NA postganglionic synapse ● Parasympathetic “rest and digest” ○ Craniosacral, CN (III, VII, IX, X) and S3-S4 in origin ○ Long preganglionic fibre → synapse autonomic ganglia near effector organs→ short postganglionic fibre ○ ACh both preganglionic and postganglionic synapse