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Biopsych - Neuroanatomy (Y1) - Coggle Diagram
Biopsych - Neuroanatomy (Y1)
Neuraxis of the brain
Function is about economy and efficiency and it is dynamic and evolving dependent on the environment
Directions in the body are described relative to the neuraxis, which is a line drawn from the spinal cord to the front of the brain
Dorsal - up (towards back) and ventral - down (towards stomach)
Horizontal / transverse slice (superior and inferior)
Posterior / caudal - back, anterior / rostral - front half
Coronal slice
Lateral - far away from midline, medial - close to midline
Left and right slice - midsagittal slice
CNS and PNS - CNS are the nerves of the spinal cord and brain; PNS are all nerves and ganglia outside the brain and spinal cord
Somatic and autonomic nervous systems; somatic is voluntary control, autonomic is subsconscious
Autonomic divided into parasympathetic and sympathetic - rest and digest and fight or flight respectively
Organisation of nervous system: stimulus - sensory division of PNS transmits information from periphery
CNS processes and integrates information, initiates responses, mental activity
Motor division of PNS transmits information to the periphery, with somatic nervous system causing response in the skeletal muscles, and the autonomic nervous system causing a response in the cardiac, smooth muscles and glands
Output of activity / behaviour
Autonomic nervous system - visceral function, heart rate, respiration rate, digestion, salivation, pupil dilation and sexual arousal
Sympathetic - fight or flight, HPA axis, adrenaline to adrenal medulla, medulla sensory pathway
Parasympathetic - rest and digest system
CNS - Brain regions
Hindbrain - at bottom, PONS, cerebellum and the medulla oblongata
Cerebellum - little brain, 50% of the total neurons in brain, grey and white matter, important to voluntary movement, body position and motor learning
PONS - situated at top of brainstem, acts as a bridge between cerebrum, medulla oblongata and the cerebellum
Reticular formation (orange strips of cells inside the pons) - 90+ nuclei, regulate activity and sleep
Medulla oblongata - relays motor and sensory signals between spinal cord and higher brain regions, reflex control centre e.g. heart rate, blood pressure, breathing, swallowing and sneezing
Midbrain: tectum and tegementum, located just above medulla oblongata
Tectum - dorsal; superior and inferior colliculus, responsible for visual processing
Tegmentum - Substantia nigra, responsible for movement control, involved in Parkinson's and other motor diseases; contains red nucleus and cerebral aqueduct
Brainstem - pons, medulla oblongata and midbrain
Forebrain - thalamus, hypothalamus (diencephalon), telencephalon (cerebral hemispheres, containing cortex, basal ganglia and the limbic system)
Thalamus - all sensory pathways but the olfactory relay here before terminating in cerebral cortex and distributes responses to parts of the body where it is required-
Hypothalamus - homeostasis and hormones, controlling the autonomic nervous system or by causing the release of hormones (pineal gland is here)
Diencephalon - above brain stem, bottom part of hemispheres
Basal ganglia - 4 major neuron groups; striatum containing caudate and putamen, globus pallidus, substantia nigra - movement and subthalamic nucleus - mainly concerned with movement
-> basal ganglia also location of olfactory tract and olfactory bulbs, involved in planning, memory, motor control of voluntary movement, attention, habits and procedural memory
Limbic system - hypothalamus, hippocampus, amygdala and cingulate cortex (looks like a swirl/yule log)
Learning and memory, emotional memories and recognition of emotion in other people
Structures; anterior thalamus, mammillary bodies, hippocampys, amydalaga, cingulate cortex, hypothalamus
Amygdala - fear and threat detection, emotional memories, coordinates behaviour, autonomic and endocrine responses to environmental stimuli especially those with emotional content (SM case study, women with no fear and a damaged amygdala) - fight or flight response
Hippocampus - posterior to amygdala - establishing memories, context learning, memory retrieval, understanding spatial relations within environment and navigation - HM
-> hippocampus is near olfactory tract, explaining why smell triggers memory - memory, learning and spatial processing
Telencephalon - fore brain cortical folding; folds allow higher surface area, making it easier for brain regions to communicate with one another and means more structures can fit; important for childbirth
Cortical folding also decreases the distance of travel for signals and information
Cortical folding - gyri and sulci;
gyri are a convolution or bump, and are the surface of the fold
sulci are the valley between gyri or enfolded regions that appear as surface lines (gaps between gyri) - sulcus
Fissure - very deep sulcus
Grey matter in gyrus, white matter beneath
Longitudinal fissure - hemispheric fissure as it divides the two hemispheres
Major sulci - central sulcus (rolandic) - divides the parietal and frontal lobes, location of motor cortex
Sylvian / lateral fissure - divides the temporal lobe from the frontal and parietal lobes
4 lobes of the brain - frontal, parietal, temporal and occipital
Frontal lobe - largest brain lobe, latest to develop and mature, executive brain in planning, guiding and moral judgement behaviour
Also contains motor cortexes, develops until late twenties
guiding behaviour - reward behaviour, personality, foresight - orbital portion of prefrontal cortex important for switching between mental sets and regulation of emotion
Broca's area - motor functioning of speech
Motor cortex - primary motor cortex, voluntary movement
Parietal lobe - association cortex, integrates sensory information from multiple modalities
Somatosensory cortex - integration and processing sensory information from the body and tactile perception
Cortical association area - inferior parietal gyrus integrates and processes sensory information from the body - tactile perception
Spatial processing - superior parietal gyrus is concerned with body image and spatial orientations
Occipital lobe - vision, one of the most complex senses or shapes, colour and motion
Primary visual cortex - located in and around the calcarine fissure, with many additional areas dealing with colour and motion
Temporal lobe - language processing in Wernicke's area, long term memory knowledge processing (hippocampus)
Primary auditory cortex - near Wernicke's area
Parahippocampal gyrus - learning and memory
Corpus callosum - largest white matter structure in the brain (bundle of axons) with 200-250 million axonal projections
Projects information between the two hemispheres - Sperry and Gazzaniga's split brain research
Major fibre connection between the hemispheres
Allows communication between cerebral hemispheres - important for normal brain functioning
Brain barrier systems - Skull, meninges, cerebrospinal fluid and the blood brain barrier
Meninges - spongy structures, three layers of membrane that cover and protect brain (dura mater; tough hard layer, arachnoid space / subarachoid space where CSF sits, blood vessels and the pia mater, thin membrane with blood vessels that divide the brain from meninges )
Cerebrospinal fluid:
CSF - buoyancy; allows brain to maintain its density without being impaired by its own weight
Protection - protects brain tissue from injury when jolted or hit
Chemical stability - allows for homeostatic regulation
CSF produced in the ventricular system (choroid plexus) - flows into ventricles of the cerebrum, central cavities in brain stem core, then exist in subarachnoid space through apertures, where it is then absorbed by arachnoid villi blood vessels
Blood brain barrier - tightly packed blood vessels creating a barrier that only allows certain molecules to pass through, and this protects the neural tissue from variations in blood composition and toxins
Blood molecule in the body has less protection than a blood molecule in the brain but this makes developing drugs difficult due to impaired delivery systems
Brain cells - neurons, glial cells; neurons are electrically active
Generate a series of electrical impulses that allow them to send information throughout the brain - 85 billion
Information processing, still finding unique neurons that only exist in men or women etc
Rosehip neuron - upper layer of cortex, associated with inhibition of neurons; not in mice, so unique to humans
Glial cells - glue support for neurons, contribute and regulate the chemical environment, enhance the electrical signalling of neurons, remove debris left by dead neurons
Important roles in brain signalling
Golgi - reticular theory of neurons, Cajal - neuron doctrine - electron microscope proved him right
Prototypical neuron - soma + dendrites + axon;
soma contains nucleus, is the metabolic centre of neuron, nucleus contains the DNA and is the blueprint for RNA
Cytoplasm - everything within the cell membrane, including organelles, excluding nucleus
Cytosol - intracellular fluid inside a cell (potassium rich, salty)
Organelles - other structures in the cells, nuecleus, mitochondria, rough and smooth endoplasmic reticulum (ER has ribosomes)
Nucleus - transcription in protein synthesis, where messenger RNA (mRNA) takes information spliced from nucleus, exons removed and in translation mRNA binds to ribosomes to translate mRNA into proteins and many attach to rough ER
Mitochondria - powerhouse of the cell, respiration and ATP
Cytoskeleton - cell shape, correct positioning of organelles and track in cell respiration (mircotubules, microfilaments and neurofilament)
Neuronal membrane - barrier to enclose cytoplasm inside neuron, protein composition varies depending on environment, critical for neuron functioning, as action potentials depend on these depolarising
ribosomes syntehsis the protein information, gathering amino acids and stringing them into peptides / polypeptides
Golgi apparatus takes any proteins not required for intracellular function and distributes them to axon / dendrites
Smooth ER regulates internal substances and folds proteins
Rough ER - ribosomes, binding site for mRNA to assemble proteins (Nissl bodies) and ribosomes manufacture proteins from amino acids using the mRNA sequence
Axon - specialised to neurons, information transfer of electrical signals over great distances
No rough ER, hardly any ribosomes, most proteins come from axon hillock, where neurofilaments cluster to provide fascicles
Sciatica nerve is longest axon
Finishes at axon terminal, starts at hillock
Axoplasmic transport - transports necessary materials from soma to axon terminal (anterograde travel, forward, and retrograde travel back)
Terminal arbor - synaptic vesicles, containing neurotransmitters and mitochondria
Synapse - point of contact between axon and dendrite of another neuron, synaptic cleft in which diffusion of chemical signals occurs
Dendrite - antennae of the neuron - receiving systems; acts as postsynaptic membrane
full with receptors, special proteins which bind to neurotransmitters and take up chemical signals from pre synaptic neurons and carry on electrical signals
Dendritic spines - increases possible synaptic contact sites between neurons and are very effective synapses that can quickly change in appearance
Important for plasticity and learning, as new spines can grow, existing spines can change through synpatic pruning
Ribosomes found in spines - protein production for structural change
Classification based on neuronal structure
Number of neurites (axon and dendrites) - all neurons have one axon but have different dendrite amounts
Unipolar - one axon, skin cells
Bipolar - one axon and one dendrite, visual cells
Multipolar - one axon and many dendrites (most neurons)
Taking a small amount of information leads to greater precision, hence the uni and bi polar neurons being sensory
Dendrites -
Stellate cells - tight network, perfect for interconnection and information exchange between neighbouring neurons
Pyramidal cells - dendrite tree with pyramid shape, and are perfect for transferring information over long distances
6 layers in cortex - integrative neurons, input of sensory information and output to other parts of the brain
Primary sensory cortex - half of layers are integrative, 1/6 is inpiut and 2/6 are output (smallest output)
Association cortex - same structure, but layer of input is much smaller than sensory cortex
Primary motor cortex - same structure, but thinnest input and biggest output - also smallest integrative layer
Brainbow - genetic method to label each individual nerve cell a different colour in order to track axons and dendrites over long distances
With light microscopy, scientists image the branching patterns and connections of all the axons within a region of the nervous system in transgenic mice that express a number of different fluorescent proteins (transgenic - gene replaced, in mice have gene added, out mice have gene removed)
Glial cells - CNS and PNS; astrocytes, oligodendrocytes cells and Schwann cells:
Astrocytes - star like, most numerous glia in brain, in gaps between neurons and influence neurite growth (dendritic spines), regulation of chemical content in the extracellular space, restricting spread of neurotransmitters from synaptic cleft, active removal of neurotransmitters from synaptic cleft
Neurotransmistter receptors can trigger electrical and biochemical events inside the glial cell
Myelinating cells - oligodendrocytes (CNS) and Schwann cells (PNS):
insulation of axons by supplying a myelin sheath around the neuron axon to increase conduction speed through nodes of ranvier also
Myelination disorders result when neurons lose their insulation and so electrical signals are lost, leading to motor disorders (treatments for MS could come from replacing genes that produce these cells)
Microglia - 10% of brain cells, continually survey local environment;
Remove dead or degenrated neurons and glia, acting as immune cells of the brain
Developmental synaptic pruning - get rid of weak, extra synapses
Synaptic plasticity in the adult - learning and memory
Involved in neurodevelopment and neurodegenerative disorders - seem dysfunctional in autism spectrum disorders, reactive gliosis and neuroinflammation are hallmarks of Alzheimer's disease