S1W2- Advanced neural transmission

S1W2- Advanced neural transmission

1. Terminology

   • Slices
     • Views of the brain, as if it has been sliced in half from different angles: Horizontal Sagittal Coronal Some parts of the brain are more easily seen in certain slices: E.g. basal ganglia is best seen in coronal slice
   • Directions
     • Top or bottom of a region (e.g. Dorsal Anterior Cingulate is the top of the Anterior Cingulate) -Can also refer to the top or bottom of a region (e.g. Superior temporal lobe is on the top of the temporal lobe – and is superior to the other parts of the lobe)
   • Gyrus = protuberance on the surface of the brain (plural = gyri)
     • Sulcus = fold or groove separating gyri (plural = sulci)
       • Fissure = a long, deep sulcus
         • Proximal = close to Distal = far from Ipsilateral = same hemisphere Contralateral = opposite hemisphere

2. Neurons

   • Central nervous system
     • Central Nervous System: Brain Spinal Cord
       • Peripheral nervous system
         • Somatic Nervous System: Voluntary Muscles and Senses
           • Autonomic Nervous System: Involuntary Muscles Sympathetic: “fight or flight” Parasympathetic: “rest and digest”
   • Neurons and Glia
     • The nervous system consists of Neurons and Glia Neurons – receive and transmit information Glia – serve many varied functions (e.g. insulation, support)
       • All neurons consist of a cell body with a number of processes (longer parts leading off the cell body – e.g. dendrites, axon) A collection of cell bodies in the peripheral nervous system is called a ganglion A collection of cell bodies in the central nervous system is called a nucleus*
     • Neurons:
       • Nucleus DNA Protein Synthesis, including neurotransmitters
         • Soma Cell Body Contains the nucleus
           • Dendrites Receives signals from other neurons. Dendrites are bumpy – they have spines which grow and shrink as a result of repeated activations (e.g. through learning)
             • Axon Hillock: Very top of the axon Common ‘trigger site’ for action potentials
               • Axons: - Carries action potentials Transmits signals to other neurons
                 • Axon Terminals: - End of the axon- End in the terminal buttons
                   • Terminal Buttons : Release neurotransmitters into the synapse
                     • Myelin Sheath Made of Glial Cells Insulates the axon Increases speed of action potential propogation
                       • Nodes of Ranvier: Gaps in the myelin sheath Site of action potential regeneration in myelinated axons
                         • Afferent/Efferent? - Relative term referring to where the axon is going from or to This axon is efferent from the pre-synaptic neuron, and afferent to the post-synaptic neurons
     • Glia: Three primary types of Glial cells
       • Astrocytes (star-shaped)- involved in response to injury of the CNS; regulate blood flow to some neurons
         • Oligodendrocytes - form myelin in the CNS Schwann cells form myelin in PNS
           • Microglia – involved in immune response in the CNS

3. Brain anatomy

   • Three major divisions of the brain: Hindbrain (rhombencephalon) Midbrain (mesencephalon) Forebrain (prosencephalon)
     • The posterior part of the brain, consisting of the: Medulla Pons Cerebellum
       • The Medulla (oblongata) is an enlarged extension of the spinal cord into the skull Controls vital reflexes – breathing, heartrate, vomiting, salivating, coughing, sneezing – through the cranial nerves
         • -The cranial nerves control sensations from the head, muscle movements of the head and most parasympathetic output to the organs -The receptors and muscles of the head are connected the brain via 12 pairs of cranial nerves - Each cranial nerve originates in a nucleus (cluster of neurons) that integrates sensory information, regulates the motor output, or both - The nuclei for cranial nerves V to XII are located in the medulla and pons; those for cranial nerves I to IV are in the midbrain and forebrain
       • The hindbrain
     • Midbrain
       • The middle part of the brain, consisting of the: Tectum Superior colliculus Inferior colliculus
         • The superior colliculus is important for vision The inferior colliculus is important for hearing. - Several nuclei and tracts occur in the midbrain – including the substantia nigra
     • Forebrain
       • Most prominent part of mammalian brain, consisting of two cerebral hemispheres (left and right) Hemispheres receive sensory input, and control muscles, on the opposite side of the body
         • Consists of: Limbic System Diencephalon Basal Ganglia Cerebral Cortex
           • Limbic structures carry out a very wide variety of functions, including emotion, motivation (including feeding/sleeping, and cognition. - The Thalamus and Hypothalamus together form the Diencephalon
             • The forebrain- Diencephalon
               • Most sensory information (except olfactory) first goes to specific nuclei of the thalamus, which processes it and send output to the cerebral cortex Thalamus: Many important functions, one of which is a sensory relay. Information from all sensory receptors (except olfactory) goes to the thalamus for processing before travelling on to specific areas of the cortex Hypothalamus: Tiny area below the thalamus, vital for homeostatic functions, regulation of the autonomic nervous system Epithalamus: includes the pineal gland
                 • The forebrain- Basal ganglia
                   • A group of subcortical structures lateral to the Thalamus, includes the: Caudate nucleus The Putamen The Globus Pallidus. Functions include movement and memory
                     • The forebrain- Cerebral Cortex
                       • Outer layer of the brain = cerebral cortex Cerebrum = ‘brain’, Cortex = ‘bark’ or ‘shell’ . The cerebral cortex is folded (creating gyri and sulci) – two-thirds is found under the surface Approximately 1,000,000,000,000 neurons in the entire cortex
                         • Distinct lobes of the cortex are separated by particularly large sulci/fissures: Frontal Parietal Occipital Temporal
                           • These lobes include some primary sensory/motor areas: Occipital: primary visual cortex Parietal: primary somatosensory cortex Temporal: primary auditory cortex Frontal: Primary motor cortex
   • White matter
     • -White matter is composed of bundles of axons connecting different areas of the brain. -Very important. to brain function, as it allows for neural communication. -The white colour derives from the myelin sheath
       • Major white-matter tracts include: Corpus Callosum: connects left and right hemisphere Anterior commissure: connects left and right hemisphere Fronto-Occipital Fasciculus: connects frontal and occipital lobes

4. Resting potential

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