Neuroanatomy Lecture Notes (PDF)

Ne u roa n a t om y P SYU2236 / P SYX2236 Biop s yc h o lo gy & Le a rn in g Le c t u re r: Dr Ch ris t in a P e rry Re c a p 1. The Neuron 2. The Synapse Th e Ne u ron REVISION Types of cells in the nervous system - What is a neuron? - Structure of a neuron (dendrites, soma,...

Ne u roa n a t om y P SYU2236 / P SYX2236 Biop s yc h o lo gy & Le a rn in g Le c t u re r: Dr Ch ris t in a P e rry Re c a p 1. The Neuron 2. The Synapse Th e Ne u ron REVISION Types of cells in the nervous system - What is a neuron? - Structure of a neuron (dendrites, soma, axon, terminals) - Classification of neurons - What are a glial cells? - Different glial cells have different functions The Action Potential - Resting potential and how it is generated - How is membrane potential regulated - What happens when membrane potential changes - threshold 3 Th e Syn a p s e REVISION Neural Integration - Excitatory and Inhibitory Postsynaptic Potentials (EPSP and IPSP) - Changes in membrane potential are integrated at the axon hillock - If depolarisation reaches a threshold, an action potential occurs Communication between neurons: across the synapse - Chemical synapses and electrical synapses - Neurotransmitter release - Exocytosis and Endocytosis Ion- ion channels so when the NT binds to them they open or close and that causes changes to the Neuropharmacology resting potential. - Ionotropic receptors - Metabotropic receptors Metabotropic- bind to g proteins and when the NT binds to - Agonists and antagonists them it causes a change to the G proteins and once there's been that change that can trigger second messenger Agnonist (increasing the function) cascades or open ion channels. GDT is swapped out for Antagonist (decreasing the function) Guanine Triphosphate. 4 Ou t lin e 1. Overview of the Nervous System 1. Central Nervous System (CNS) 2. Peripheral Nervous System (PNS) 3. Communication between Brain and Body 2. Major Systems in the Brain 1. Cerebral Cortex 2. Limbic System 3. Basal Ganglia 4. Midbrain Dopaminergic Pathway Ove rvie w o f t h e Ne rvou s Sys t e m Overview of the Nervous System Central Nervous System Cerebrum Cerebellum Brain Stem Spinal Cord Peripheral Nervous System All nervous outside the spinal cord Somatic Nervous System Autonomic Nervous System Somatic; voluntary movement Autonomic; automatic functions such as respiration Similar to Fig 3.1 Kalat 7 Central Nervous System Emotions Sensation Controlled action: seeking rewards avoiding danger Co-ordination of movement Reasoning and judgement Learning and memory Control of bodily function Maintenance of homeostasis 8 Anatomical Directions OVERVIEW OF THE NERVOUS SYSTEM Visualisation in two-dimensional space Rostral comes Horizontal from the word Sagittal 'beak' whereas Coronal caudal comes from 'tail' “Directions” or axes Rostral - caudal (front to back) Dorsal - ventral (top to bottom) Medial – lateral (middle to edge) Fig 3.2, Kalat 12th Ed. 9 Ventricles and Cerebrospinal Fluid OVERVIEW OF THE NERVOUS SYSTEM Nervous system begins as a tube Central Canal (spinal cord) Four Ventricles within the brain Cerebral Aqueduct Two lateral ventricles Third ventricle Fourth ventricle Cerebrospinal fluid (CSF) produced in the choroid plexus CSF surrounds and protects the brain (meninges) CSF carries hormones and nourishment Fig 3.17, Kalat 12th Ed. 10 Meninges and the Subarachnoid Space OVERVIEW OF THE NERVOUS SYSTEM 1. Cushioning: protects the brain and spinal cord from mechanical trauma and injury. Distributes the forces that occur during head movements or impacts. 2. Buoyancy: Brain "floats" within the skull. Prevents compression of the brain under its own weight. 3. Nutrient Transport: CSF supplies essential nutrients and removes waste products from the brain and spinal cord. It acts as a medium for transporting substances between the nervous system and the blood. 11 Summary OVERVIEW OF THE NERVOUS SYSTEM Cerebrospinal fluid (CSF) is made by the choroid plexus (in lateral & third ventricles) The ventricles and subarachnoid space circulate cerebrospinal fluid through and around the brain to provide nourishment and protection (cushioning) of neural tissue There are four ‘ventricles’ (lateral, third, fourth, cerebral aqueduct) Once CSF has circulated around the brain it is reabsorbed by the arachnoid villi (of subarachnoid space) into venous blood (return to heart) The cranial and spinal meninges also protect and nourish these areas: dura mater, arachnoid mater, pia mater. 12 Blood Brain Barrier OVERVIEW OF THE NERVOUS SYSTEM Tightly packed endothelial cells line the blood vessels in the brain and spinal cord 1. Physical Barrier: tight junctions prevent most substances from freely passing between the blood and the brain tissue. 2. Selectively Permeable: certain molecules can pass through Small, lipophilic (fat-soluble) molecules like oxygen and carbon dioxide pass through easily larger or hydrophilic (water-soluble) molecules, pathogens, and toxins are blocked. Active transporters allow passage for select molecules e.g. glucose, amino acids Fig 1.11, Kalat 12th Ed. 13 Crossing the Blood Brain Barrier OVERVIEW OF THE NERVOUS SYSTEM (CNS) Brain capillary endothelial cells have continuous tight junctions Only highly lipophilic drugs and small uncharged molecules can cross from blood capillaries to cerebrospinal fluid (CSF) by diffusion What is di usion? Important nutrients - amino acids & glucose are actively transported across to CSF by proteins in the capillary membrane called TRANSPORTERS. Transportation across the membrane requires energy use. 14 Peripheral Nerves OVERVIEW OF THE NERVOUS SYSTEM Cranial Nerves (12 Pairs) Cervical Nerves (8 Pairs) Fig 3.6 Kalat Thoracic Nerves (12 Pairs) Lumbar Nerves (5 Pairs) Sacral Nerves (5 Pairs) Coccygeal Nerve (1 Pair) 15 Somatic Nervous System OVERVIEW OF THE NERVOUS SYSTEM Nerve fibres have dorsal roots and ventral roots Dorsal roots connect to skin (sensory nerves) Send information to motor system Sense of touch Ventral roots connect to muscle Send information from motor system Movement Degeneration of ventral roots Motor Neuron Disease (MND) or Amyotrophic Lateral Sclerosis (ALS) 16 Summary Somatic Nervous System OVERVIEW OF THE NERVOUS SYSTEM The somatic nervous system receives sensory input and delivers motor/muscle output Sensory input is received through the dorsal roots to the spinal cord Motor output is delivered via the ventral roots of the spinal cord to the muscle There are 6 areas that the nerves join the CNS - cranial, cervical, thoracic, lumbar, sacral, coccygeal There are 4 lobes of the cerebrum (frontal, parietal, occipital, temporal) The brain receives sensory information (of touch) at the somatosensory cortex and produces behaviour by modulating motor output from the primary motor cortex 17 Autonomic Nervous System OVERVIEW OF THE NERVOUS SYSTEM Sympathetic - extends from thoracic and lumbar spine Short preganglionic nerves Ganglion = cluster of neurons Long postganglionic nerves Parasympathetic - extends from cranium and sacral spine (craniosacral) Long preganglionic nerves Para means alongside Short postganglionic nerves (i.e. parallel) Both are usually active - but change intensity as the need arises Parallel systems that work in opposition to each other Increase sympathetic results in decreased parasympathetic Sympathetic – Prepared to body for action Parasympathetic - non emergency (digestion, growth, immune responses, energy storage) P69-70 Kalat 18  Sympathetic and Parasympathetic Outflow OVERVIEW OF THE NERVOUS SYSTEM Sympathetic Parasympathetic Cell bodies in spinal Ganglia are close cord to target organs Closely linked If you're in danger the parasympathetic NS organs tend to shut down Fig 3.6 Kalat 19 Hormones OVERVIEW OF THE NERVOUS SYSTEM Carry information (like neurotransmitters), but conveyed by blood Slower acting Longer lasting action Hormones important for the nervous system controlled by the hypothalamus and pituitary Some hormones can also be neurotransmitters. They're carried in the blood and bind to receptors or organs. The pituitary gland is connected to/part of the hypothalamus Fig 2.21 Kalat 20 Hormones OVERVIEW OF THE NERVOUS SYSTEM Hypothalamus regulates hormone release from the pituitary Secretes releasing hormones and inhibiting hormones Negative feedback control (Inhibit already released hormones) GH – growth hormone ACTH – adrenocorticotropic hormone adrenal gland TSH – thyroid secreting hormone thyroid gland FSH – follicle-stimulating hormone ovaries/testes LH – luteinizing hormone ovaries Prolactin mammary glands Vasopressin Oxytocin Fig 2.22 Kalat 21  Communication between Brain and Body OVERVIEW OF THE NERVOUS SYSTEM Peripheral Nervous System Sympathetic prepares the body for action and Somatic (sensorimotor) parasympathetic is for when we don't need to act Autonomic (parasympathetic, sympathetic) (rest and digest) Hormones Hypothalamus & Pituitary (many different hormones) Pineal gland (melatonin) Consider: speed and range of effect 22 1. Ove rvie w of t h e Ne rvou s Sys t e m - Su m m a ry Vertebrate Nervous System is subdivided into central and peripheral Central nervous system (CNS) is the brain and spinal cord CNS is protected by cerebrospinal fluid which circulate through a system of ventricles and around the brain. Blood brain barrier also protects the brain by providing a semipermeable barrier across which only certain substances can pass. Peripheral nervous system connects the brain to the body, and can be further divided in the autonomic and somatic systems The somatic nervous system controls voluntary action, and consists of axons which convey messages between sense organs, the CNS, and muscles in the body. The autonomic nervous system controls bodily functions such as heartrate and respiration, and consists of axons that connect organs with the CNS Sympathetic outflow – prepares the body for action Parasympathetic outflow – promotes “non emergency” actions e.g. digestion Hormones release from the hypothalamus and pituitary gland are also critical for communication between brain and body. Bre a k Bre a k Tim e Ma jor Sys t e m s in t h e Bra in BRAIN STRUCTURE AND FUNCTION Lateral Surface of the Brain BRAIN STRUCTURE AND FUNCTION Sulci – fissures Gyri – ridges 26 Sagittal Section of the Brain BRAIN STRUCTURE AND FUNCTION The corpus collum is a long layer of myelinated axons 27 The Cerebral Cortex BRAIN STRUCTURE AND FUNCTION Frontal Lobe Primary motor cortex and prefrontal cortex Parietal Lobe Primary somatosensory cortex Occipital Lobe Primary visual cortex Temporal Lobe Primary auditory cortex See Kalat: Module 3.2. 28  Frontal lobe function: motor function BRAIN STRUCTURE AND FUNCTION Primary motor cortex Execution, regulation and coordination of movements on the opposite side of the body Somatotopic organisation: point-for-point correspondence of an area of the body to a specific point on the central nervous system Premotor cortex Preparing and executing limb movements Selection of appropriate movement Learning Social cognition Mirror neurons: active when observing others performing an action Supplementary motor area Planning of complex movements Coordinating two handed movements 29  Frontal Lobe – Cognitive Function BRAIN STRUCTURE AND FUNCTION Prefrontal cortex Attention Working memory Prospective memory Temporal memory Planning Decision making See Phineas Gage Problem solving Language Self Control 30 Temporal Lobe BRAIN STRUCTURE AND FUNCTION Auditory Functions – Superior Temporal Gyrus Primary auditory cortex – processes and integrates auditory stimuli Language recognition Tonotopic map: certain cells prefer particular tones Memory and Emotion Function Medial temporal lobe involved in encoding long term declarative memory (hippocampus) Damage can result in anterograde amnesia Inability to respond appropriately to emotional stimuli 31  Speech Function BRAIN STRUCTURE AND FUNCTION Broca’s area In the motor cortex (frontal lobe) Important for speech production Broca’s aphasia caused by damage to this area – people can understand speech, but cannot speak properly themselves. Wernicke’s area In the auditory cortex (temporal lobe) Important for speech comprehension Wernicke’s aphasia (fluent aphasia) caused by damage to this area – people can speak, but cannot understand speech properly. The result is fluent speech with no meaning CHRISTINA PERRY | PSYCHOLOGY 32  Occipital Lobe Function BRAIN SYSTEMS AND CIRCUITS Processing visual information Primary visual cortex (V1) Receives input from retina via the lateral geniculate bodies First stage of visual processing – responsive to simple properties e.g. orientation, spatial frequency, edge detection Higher visual areas (V2-6) Process more complex features Integrate information Cortical blindness Damage to the occipital lobe can cause blindness, even though eyes are fully functional CHRISTINA PERRY | PSYCHOLOGY 33  Parietal Lobe Function BRAIN SYSTEMS AND CIRCUITS Primary Somatosensory Cortex Integrating sensory information Proprioception (knowledge about the position of the body in space) Somatotopic organisation, like the motor cortex CHRISTINA PERRY | PSYCHOLOGY 34  The Limbic System BRAIN SYSTEMS AND CIRCUITS Limbus meaning boundary Forms a border around the brain stem Important for processing emotional stimuli Amygdala is names after an almond due to its shape CHRISTINA PERRY | PSYCHOLOGY PSYH4461/PSYM7761 Lecture 1: Basic Biopsychology Review, Feb 21, 2023. Perry.35  Amygdala BRAIN SYSTEMS AND CIRCUITS Important for processing emotional stimuli Activated when viewing images that should arouse fear Damage to this area results in reduced fear Urbach-Wieth’s disorder Klüver-Bucy syndrome Also important for learning and memory CHRISTINA PERRY | PSYCHOLOGY 36  Hippocampus BRAIN SYSTEMS AND CIRCUITS Long-term episodic memory: memory for specific events Damage causes loss of episodic memory (e.g. patient H.M.) “Engram” cells have been identified in the hippocampus. These encode: Specific objects (place cells) Locations in space (grid cells) Location in time (time cells) Also important for processing contextual information Adult neurogenesis occurs in the dentate gyrus CHRISTINA PERRY | PSYCHOLOGY 37  Cingulate Gyrus BRAIN SYSTEMS AND CIRCUITS Processing pain and emotional pain Activated in response to empathetic pain (watching others in pain) Damage does not prevent the sensation of pain, but the pain is not distressing CHRISTINA PERRY | PSYCHOLOGY 38  The Basal Ganglia (dopamine neurons BRAIN SYSTEMS AND CIRCUITS synapse on this part of the brain) Important for movement, cognition and motivation Parkinson’s Disease Spontaneous, self-generated behaviours Direct and Indirect Pathways Striatum Thalamus Direct = simple excitatory movement Indirect = learned movement, inhibition of previous response. Involves more relay between the striatum and thalamus, which slows processing The Putamen also controls the NaC (Nucleus Accumbens) involved in reward CHRISTINA PERRY | PSYCHOLOGY  Caudate nucleus and Putamen BRAIN SYSTEMS AND CIRCUITS Together termed the striatum Terminal of the midbrain dopaminergic neurons (from Ventral tegmental area and substantia nigra) Important for motivation and movement Limbic motor interface Nucleus accumbens is particularly important for motivated responding Implicated in substance use disorders Things that are rewarding will cause an activation of dopamine. CHRISTINA PERRY | PSYCHOLOGY 40  Globus Pallidus BRAIN SYSTEMS AND CIRCUITS Part of the relay system between the striatum and the Sub-thylamic nucleus thalamus Important for regulation of voluntary movement Loops between striatum, globus pallidus and thalamus form the indirect pathway Striatum Obeso et al. 2012 Movement Disorders 23(S3) ppS548-559 CHRISTINA PERRY | PSYCHOLOGY 41  Thalamus BRAIN SYSTEMS AND CIRCUITS Relays sensory information to the cerebral cortex Multiple different subunits that have different functions Essentially, the thalamus is the relay centre taking info from the brain stem to the cortex and back out the cortex via the STR and the GPs. (See above) CHRISTINA PERRY | PSYCHOLOGY 42  Hypothalamus BRAIN SYSTEMS AND CIRCUITS Neuroendocrine centre Many different subregions that regulate the production and release of different hormones Plays an important role in Motivated behaviour Feeding Drinking Temperature regulation Sexual behaviour Fight or flight Arousal Hypothalamic-pituitary adrenal axis (HPA axis) controls stress/response to stress via cortisol release Rewatch to see how cortisol plays a role in stress here CHRISTINA PERRY | PSYCHOLOGY 43  Ventral Tegmental Area and Substantia Nigra BRAIN SYSTEMS AND CIRCUITS Primary source of dopamine in the brain Dopamine neurons Mesocorticolimbic dopaminergic pathways VTA nucleus accumbens VTA frontal cortex Learned behaviour, reward seeking, substance use disorder Nigrostriatal pathway Substantia nigra Striatum (caudate nucleus) Movement Parkinson's Disease The Nigrostriatal pathway is the rst pathway to degrade in Parkinson's Disease CHRISTINA PERRY | PSYCHOLOGY 44  Comparative brains BRAIN SYSTEMS AND CIRCUITS Human Rat Sokolowski & Corbin (2012); Front. Mol. Neurosci. Human cortex is larger and more complex than other mammals Subcortical structures, including basal ganglia and limbic system are highly conserved What sort of behaviours may be realistically modelled in other animals? CHRISTINA PERRY | PSYCHOLOGY 45 2. Ma jo r Sys t e m s in t h e Bra in - Su m m a ry 1. The cerebral cortex of the brain has four lobes Frontal (cognition, motor function) Temporal (hearing, memory and emotion) Parietal (sensory systems esp touch) Occipital (sight) 2. The Limbic system is important for motivation and emotional processing Amgydala Hippocampus Cingulate Gyrus 3. The Basal Ganglia is important for movement, cognition and motivated behaviour Limbic motor interface Striatum (caudate nucleus and putamen) and nucleus accumbens Thalamus 4. The Hypothalamus is the endocrine centre, and controls motivated behaviour via hormone release 5. The VTA and SN are the source of midbrain dopaminergic pathways Ne xt Tim e The lecture topic next week is “Neurotransmitters” Reading: Kalat Module 2.2 and Appendix A Remember to post questions in teams if you don’t understand anything! Ha ve a go o d d a y!