Neuroanatomy I PDF - BIOL2051/2052 Past Paper

Neuroanatomy I BIOL2051/2052 Dr. Melissa Andrews ([email protected]) October 3, 2024  Lecture Objectives Compare and contrast the key features of invertebrate and vertebrate nervous systems Discuss the role in cephalisation in developing a...

Neuroanatomy I BIOL2051/2052 Dr. Melissa Andrews ([email protected]) October 3, 2024  Lecture Objectives Compare and contrast the key features of invertebrate and vertebrate nervous systems Discuss the role in cephalisation in developing a more complex nervous system Discuss the characteristics of vertebrate and mammalian nervous systems Describe the divisions and components of the human brain Recommended reading: Chapter 1 (Studying the Nervous System in Humans and Other Animals) in Neuroscience, 3rd ed by Purves et al (check later editions for chapter number) Areas of the nervous system: PNS (Peripheral Nervous System) Cranial Nerves Spinal Nerves Ganglia (Dorsal root ganglia and autonomic ganglia) CNS (Central Nervous System) Brain and spinal cord Control centre for information processing, responding to sensory information Organisation of the nervous system: In higher order organisms PNS (Peripheral Nervous System) Nerves, ganglia (aggregations of neurons), sensory receptors CNS (Central Nervous System) Brain and spinal cord Dolphin Cat Basic building blocks of the nervous system: Neurons Receive stimuli Transmit nerve impulses or action potentials Activate muscles Dendrites collect electrical signals and carry input to cell body Cell body/soma integrates signals and generates action potential Axon transmits signals over long distances from the cell body to the axon terminals. Nervous systems across species Neurons in all species are the functional units of the nervous system, organised into a functional network capable of: Response to stimuli Information processing Communication? Cultured neuron with axon initial Neuronal Networks segment labelled in yellow http://www.jneurosci.org/content/38/9/2135 http://brainmind.com But what about in less evolved organisms such as invertebrates? Nervous systems across species Differences amongst species are not due to the neurons, but how they are organised: Nerve nets Also how well they Cephalisation propagate signals Central Nervous Sys (CNS) (action potentials!) Peripheral Nervous Sys (PNS) …………………………….. do they have myelin? Sea sponges - multicellular organism without a nervous system Nervous systems across species - invertebrates Invertebrate Nervous systems are specialised for: - stimulus/response, receptor/effector - Reflexes, conditioned responses Nerve nets: Simplest form of nervous system found in some invertebrates (such as hydras, jellyfish, etc). Individual nerve cells exist in a net-like formation scattered in layers of body wall. Neurons exist in a ‘loose network’ to allow for contraction and expansion of the body cavity. Nerve nets lack distinct central or peripheral regions, and anything that resembles a brain. Nervous systems across species - invertebrates Nerve nets have no associative activity, just reflexes (with action potentials!) Nerve signals can travel in both directions However, neurons can carry: - information from sensory organs that detect touch, light, or other changes in the environment. - These neurons in turn contact neurons that control movement of the organism, such as swimming. Nervous systems across species - invertebrates Species such as sea stars (echinoderms) display centralisation of the nervous system. A ring of neurons is located in the center with simple bundles of neurons (radial nerves) extending from the ring to the tip of each arm. Radial nerves form nerve nets permitting coordinated movement of each arm and the tube feet located on the surface of the arm. ‘Eye spots’ are found at the end of each arm – for light & shadow https://www.slideshare.net/slideshow /vw/4156437 Nervous systems across species - invertebrates Cephalisation and formation of the primitive brain: In animals with bilateral symmetry, there is a clustering of neurons into ‘ganglia’ near head of animal to form more complex systems to integrate incoming/outgoing signals (seeing, hearing, tasting, etc.). Emergence of a central nervous system?…. Nervous systems across species - invertebrates Emergence of a central nervous system Nerve cords and trunks: With bilateral symmetry (flatworms, etc), 2 nerve cords run down the length of the body. This system allows more complex control of muscles for movement.  Cephalopods Nervous systems across species - invertebrates Distinct PNS and CNS regions Connections required between PNS and CNS, but PNS can act https://animals.net/giant-squid/ autonomously in some cases. Invertebrates lack myelin but action potential propagation overcome by increasing diameter of axons (Giant squid axons!) https://www.theguardian.com/environment/2019/may/12/octopus-farming-unethical-and-threat-to-food-chain Diversity of nervous systems - Giant neurons and axons – no myelin - Nerve nets – action potentials, reflexes Organism Complexity - Ganglia chains (in molluscs, worms, arthropods) Head ganglia are fused/ Cephalisation Specialisation of cells (receptors – eyes, etc) - Brain (& spinal cord) – organisation of CNS Vertebrates Diversity of nervous systems Vertebrate Nervous systems contain: Forebrain (cerebrum, optic - Sophisticated sensory mechanisms structures, olfactory lobe) - Clear differentiation of CNS and PNS Midbrain as well as sensory and motor nerves Hindbrain (Brainstem – pons, - Elaboration of brain structure, etc medulla; cerebellum) Coordination of motor reflexes in vertebrates; regulation of autonomic processes Diversity and Evolution of the ‘Brain’ Sulci – Infoldings of the cerebral hemispheres that form ‘valleys’ between the gyri (singular = sulcus) Gyri – Ridges of the infolded cerebral cortex (singular = gyrus) Subdivisions of the Nervous Systems Central Nervous System Motor and Sensory Brain Spinal Cord Peripheral Nervous System Sensory (Afferent) Motor (Efferent) Division Division (Information coming into (Information from the CNS the body and CNS) to muscles, glands, etc) Visceral/Autonomic Motor Somatic Motor Division Division (Autonomic NS: Parasympathetic and Sympathetic NS) Brain areas based on Development Forebrain Prosencephalon - Telecephalon (Cerebrum) - Diencephalon (Thalamus and Hypothalamus) Midbrain Mesencephalon Hindbrain Rhombencephalon The brain develops first as a 3 ‘vesicle’ - Myelencephalon (Medulla) structure, then a 5 ‘vesicle’ structure - Metencephalon (Pons and Cerebellum) CNS: Brain Brain divisions Cerebrum Cerebrum Diencephalon Brain Stem Cerebellum Cerebellum Frontal Lobe Parietal Lobe Temporal Lobe Occipital Lobe Netter: Atlas of Human Anatomy, 5th Edition. Copyright ©2011 by Saunders, Elsevier. CNS: Brain divisions - Cerebrum Functional areas Motor – primary motor and premotor in frontal lobe Sensory – primary somatosensory and somatosensory association areas in parietal lobe CNS: Brain divisions - Cerebrum Functional areas Vision (primary visual and visual association areas) in occipital lobe Auditory (primary auditory and auditory association areas) in temporal lobe