Neuroanatomy + Neurophysiology

• label the parts of a neuron

  A) Dendrites

  B) Axon

  C) Axon terminals

  D) Cell body

  E) Myelin

  
• Microglia


  small cells involved in immune functions, response to injury and disease, regulation of cell death, synapse formation/elimination, and overall cleaning functions
• Astroglia


  type of cells that contract/relax blood vessels, regulate flow of materials into the CNS, provide nutrients to neurons, are vital to injury response, and play a role in synaptic activity
• Oligodendroglia


  type of cells that myelinate neurons. in the PNS, Schwann cells perform this function
• Phospholipid bilayer


  separates the inside from the outside of the cell
• Because of the neuronal membrane, most substances cannot easily enter or leave the cell, called selective permeability
• During resting potential, the inside of the cell is negatively charged and the outside is positively charged
• During resting potential, A- ions and K+ ions have higher concentration inside the axon relative to the outside, whereas CL- ions and Na- ions are more concentrated outside the axon
• Resting membrane potential is typically between -60 to -70 mV
• When channels open, ion flow accross the membrane will occur
• there are both chemical and electrical forces driving the force of ions across a membrane, but the sum of these forces determines wether the net electrochemical driving force is inward or outward
• At the RMP, leak potassium channels are open all the time, and potassium ions flow outward. At the same time, sodium-potassium pumps are bringing potassium ions in and pushing sodium ions out
• Ligand-gated channels are opened by a ligand (extracellular neurotransmitter) binding to a receptor
• The membrane becoming less negative is called depolarization
• When glutamate binds to the channel AMPA, it opens and NA+ ions flow into the cell. This flow causes an excitatory post-synaptic potential which depolarizes Vm
• EPSP stands for

  excitatory post-synaptic potential
• GABA stands for Gamma-aminobutyric acid. It is a major inhibitory neurotransmitter in the brain.
• Inputs are summated at the axon hillock, the area of the cell body closest to the axon
• EPSPs push a neuron to threshold and IPSPs push a neuron away from threshold
• At threshold, the membrane potential is -55mV. Voltage-gated Na+ channels open, and NA+ ions flood into the cell
• Label the steps of an action potential

  A) Threshold

  B) Stimulus

  C) Repolarization

  D) Depolarization

  E) Resting state

  F) Hyperpolarization

  
• The action potential propagates down the axon, jumping over myelin sheaths, as there is a high density of v-gated Na+ channels in the gaps between myelin sheaths, called nodes of ranvier
• Myelin helps make signal conductance faster and more energetically favourable. Sensory and motor systems need to be the quickest, so they are the most myelinated
• Loss of myelin impairs signal conduction and is a defining feature of multiple sclerosis
• After the AP goes through, V-gated NA+ channels close and V-gated K+ channels open. During this refractory period, the neuron cannot fire a new AP
• At the end of an axon, depolarization arrives at axon terminal, where V-gated Ca2+ channels open, allowing Calcium to flow into the presynaptic terminal, triggering vesicular fusion and release of neurotransmitters into the synapse
• Ionotropic receptors signal quickly while metabotropic receptors signal slowly via a messenger cascade
• cells in the NS organize into layers. A group of myelinated axons headed in the same direction is called a tract in the CNS and a nerve in the PNS
• The meninges covers the brain and is split up into three layers: in descending order, the dura, arachnoid, and pia. The subarachnoid space is filled with Cerebrospinal fluid (CSF).
• The cerebral cortex consists mostly of neocortex (6 layers), with 10% consisting of allocortex (3-4 layers)
• The forebrain consists of the:

  A) Telencephalon

  B) Diencephalon

  
• The Midbrain consists of the Mesencephalon, which includes the Substantia Nigra
• The Hindbrain consists of the Metencephalon and the Myelencephalon
• The Hindbrain consists of the Metencephalon, which includes the Pons and Cerebellum, and the Myelencephalon, which includes the medulla
• The Telencephalon includes the Cortex, Basal Ganglia, and Limbic system
• The Basal Ganglia includes the dorsal striatum, globus pallidus, and nucleus accumbens
• The limbic system includes the cingulate cortex, hippocampus, amygdala, mamillary body, and septum
• The Diencephalon includes the Thalamus and Hypothalamus
• The Nervous system includes the Central NS and Peripheral NS
• The Central NS includes the Brain and Spinal Cord