Neuroanatomy Lecture 3 Slides PDF

Neuroanatomy at multiple scales PSYC 123 UCSC Jason Samaha Don’t forget, if there is content you want me to review next lecture, post it to the Canvas...

Neuroanatomy at multiple scales PSYC 123 UCSC Jason Samaha Don’t forget, if there is content you want me to review next lecture, post it to the Canvas “discussion” board 1 Follow up on last week’s discussion 2 Follow up on Tuesday’s discussion https://www.biorxiv.org/content/10.1101/2021.05.28.446230v2.full.pdf+html 3  Learning objectives Brain cells: types of brain cells, types of neurons, neuron structure (dendrites, cell body, axon, terminal/synapse, axon hillock), neuron function (AP process, membrane channels, neurotransmitters) Organization of brain cells: nuclei, cortex, white/grey matter, gross anatomy, orientation terminology, laminar structure of cortex, connectivity Neural dynamics: oscillations, local field potentials, synchronization 4 Neurons and Glia (Very) roughly speaking there are two types of cells in your brain. Neurons ~86 billion of them Like almost every other cell in your body except: Total dependency on oxygen (dies in 5 min w/o oxygen) Highly specialized to transmit electro/chemical signals Glia Just as numerous as neurons! Get short shrift as just “cleaners”, thought to maintain proper function of neurons 5 Neuron diversity 6 irl Dendrites Tiny “spines” are where synapses formed Cell body Axon 7 irl 8 In cartoon form 9 Basic functions of neurons 10 Basic functions of neurons 3 components to neural transmission Integration Firing (action Firingpotential) Chemical transmission 11  Integration Dendrites Dendrites of another neuron Axon Hillock Synapic terminal Axon 3 components to neural transmission Integration Firing (action potential) Chemical transmission 12 Integration Dendrites of another neuron Dendrites Axon Hillock Synapic terminal Axon 3 components to neural transmission Integration Firing (action potential) Chemical transmission 13  Firing Dendrites of another neuron Dendrites Axon Hillock Synapic terminal Axon 3 components to neural transmission Integration Firing (action potential) Chemical transmission 14  Chemical transmission Dendrites of another neuron Dendrites Axon Hillock Synapic terminal Axon 3 components to neural transmission Integration Firing (action potential) Chemical transmission 15 An analogy: leaky bucket 16 Action potential in detail Sodium Potassium Axon Na+ K+ 1 pump and 2 channels 17  Strong stimulus (e.g., bright light) Many action potentials Information is mainly Weak stimulus (e.g., thought to be encoded in dim light) a ‘rate code”! Spontaneous 18 Synapse in detail Axon 19 Synapse in detail 20  Binding on the post-synaptic dendrite Synapse Ions already exist in the synapse and could be Inside the dendrite positive (e.g., Na+) or negative (e.g., Cl-) 21 Binding on the post-synaptic dendrite Neurotransmitters Can be excitatory (depolarizes the next neuron) or inhibitory (hyperpolarizes the next neuron) 22 Binding on the post-synaptic dendrite Neurotransmitters Can be excitatory (depolarizes the next neuron) or inhibitory (hyperpolarizes the next neuron) The effect of a neurotransmitter depends also on it’s receptor Pyramidal neurons are typically excitatory Release glutamate onto AMPA receptor Inhibitory interneurons Release GABA onto various GABA receptors (e.g., GABAa) 23 Neurons in sum Electro-chemical Integration and firing is an electrical process Synaptic transmission is a chemical process Integration of electrical signals happens prior to the Axon hillock (AH) AH contains a large density of voltage-gated Na+ channels Opening these channels depolarizes that part of the axon Depolarization continues along axon via successive Na+ channels Axon is hyperpolarized (back to resting potential -70mv) by voltage- gated K+ channels Na+ pumps maintain a hyperpolarized resting potential AP reaches synaptic terminal and neurotransmitters are released Neurotransmitters cross the synapse and bind to receptors (like a lock/key) on the post-synaptic neuron Neurotransmitters can be excitatory (glutamate) or inhibitory (GABA) on the likelihood of the next neuron firing 24 25 What do we call a bunch of neurons together? Two broad organizational devisions Cortex: folded sheet-like structure covering the brainstem Has sulci (valleys) and gyri (hills) but is continuous Nuclei: collections of neuron cell bodies that all do “similar” things Found in the brainstem (e.g., the thalamus is a collection of nuclei) 26  Gross anatomy Dorsal (Superior) Rostral (Anterior) Caudal (Posterior) Ventral (Inferior) 27  Gross anatomy Dorsal (Superior) Rostral (Anterior) Caudal (Posterior) Ventral (Inferior) 28 Gross anatomy Two more distinctions White matter: Axons - white from myelin Gray matter: Cell bodies of neurons - gray from concentration of Glia Warning: video of “fresh” brain to come in two slides - involves blood 29 Gross anatomy 30 Gross anatomy 31 Knowing your way around ? 32 Knowing your way around 33 Knowing your way around Medial/Sagittal view Lateral view PPC dmPFC PPC lPFC ATL dmPFC lPFC lPFC Dorsal view ATL ATL Ventral view PPC PPC 34 The Cortex is layered: Example V1 (or primary visual cortex) Feed back from V 2 Feed forward to V2 ) us am al Th om backwards (t (fr Thalamus) d ar Feed rw fo ed Fe o 35 The Cortex is layered Different layers (from 1 - 6, or superficial to deep) are defined by Different connectivity Feedforward comes in Layer 4 Feedback comes in at Layer 1 Different density of cells Some layers have more cell bodies, some more axons Different kind of cells Pyramidal neurons in layer 4 Other kinds in different layers 36  Laminar Recordings Local field potential: Summed electric (recording from potentials from electrodes multiple (thousands) of neurons near an spanning the electrode) cortical layers) 37  Oscillations and synchrony This is called sub Failed threshold membrane initiations potential 38 Oscillations and synchrony 39 Thanks, post topics you’d like me to review! 40  Aphasia (review) Wernicke’s aphasia Typically associated with lesion to Broca’s aphasia superior posterior temporal lobe Typically associated with lesion to inferior Typically manifests as difficulty frontal lobe understanding speech, and producing Typically manifests as a speech motor meaningful sentences problem Reading and writing also affected Can usually still understand speech 41