Neurobiology

  • Vocabulary:

    • Neuron: Nerve cell that transmits signals through the body, uses both electrical signals and chemical signals. They can vary in shape

      • Cell body: Relays messages down axon, integrates chemical signals and ā€˜translatesā€™ into electrical signals

      • Dendrites: Receives signals in the form of chemicals and electricity

      • Axon: Sends electrical signals, terminates at a synapse

      • Myelin sheath: Insulates, consists of cells around the axon and increases action potential to as fast as 100 m/s, build of Schwann cells

    • Synapse: The gap between neurons/other cells

    • Synaptic terminal: Where one neuron ends, ā€˜topā€™ of the synapse

    • Synaptic terminus: End of a synapse

    • Synaptic Cleft: Actual space in the synapse

    • Glia: Cells that support and nourish neurons

    • Neurotoxin: Released by some animals like the cone snail, harm other organisms by attacking nervous systems

    • Action potential: Generated by changes in the membrane potential done by the sodium-potassium pump. This is a quick change in the membrane potential. As voltage increases, ions flow down their gradients. Sodium is brought in

    • Sensory neuron: Have cell body in the middle

    • Interneuron: Huge amount of dendrites

    • Motor neuron: ā€˜Typicalā€™ neuron in terms of shape, long axon and cell body surrounded by dendrites

    • Tetanus: Constant depolarization of the nervous system, ultimately leading to a paralysis, muscles are constantly contracted. This can be caused by venom/poison

    • Membrane potential: Maintained by a sodium-potassium pump, with more K inside and more Na outside, controlled by channels. This leads to a charge only at the membrane, leading to the inside of the cell being more negative than the outside. K tends to travel out, forming an electrochemical gradient. For cells, this is typically -70 millivolts in a resting cell. at -50 mv, channels open freely

    • Voltage gated channels: At rest they are closed, with voltage changes they respond and allow various ions inside. These are manipulated to send signals

    • Propagation: A depolarization/repolarization cycle, repeats a signal down an axon

    • Neurotransmitters: Chemicals that can either inhibit or help an action potential, sometimes gases like CO and NO can function as neurotransmitters that are synthesized by the body on command

      • Inhibitory: GABA, glycine, serotonin

      • Excitatory: Acetylcholine, dopamine, norepinephrine, nitric oxide

      • Released by the synaptic cleft from an axon, held in place by membrane proteins at the synapse, they diffuse across the cleft

    • Glutamate: An amino acid that also acts as a neurotransmitter

    • Norepinephrine: Works with epinephrine, make from tyrosine amino acid

    • Neuropeptide: Short chains of amino acids, can function as neurotransmitters. Examples are substance P and endorphins

    • Opiates: Bind to the same receptors that endorphins do, used widely as painkillers

    • Resting potential: The base membrane potential for a cell, restored from a signal with the sodium-potassium pump, around -70 mv

    • Ena: Measures voltage in a cell

    • Rising phase: Threshold for channels is reached and they open freely around -50 millivolts

    • Falling phase: Closing of potassium channels

    • Undershoot: Membrane permeability of K is higher at first, so K leaves the cell, leaving the cell more negative relative to the outside

    • Electrode: Measures action potentials of a cell, scientific device ends up damaging the cell

    • Hyperpolarization: Goes under the resting membrane potential, leads to an inhibitory signal

    • Depolarization: Massive amount of positive ions moving in, leads to an action potential

    • Refractory period: Happens after depolarization, when sodium channels are inactivated, the reason why signals only travel in one direction

    • Central Nervous system: Nervous system that isnā€™t the brain or spinal cord

    • Nerve: Bundles of axons, specifically many nerve fascicles

    • Nerve fascicle: Bundle of axons in connective tissue

    • Temporal summation: When two excitatory post synaptic potentials and produced in rapid succession

    • Spatial summation: Multiple neurons act on one neuron, multiple neurotransmitters at once

    • Afferent nerves: Carry sensory signals, from external and internal stimuli

    • Efferent nerves: Carry motor signals

      • Autonomic nervous system: Done without control, controls smooth and cardiac muscles, and glands

        • Enteric division

        • Sympathetic division: Works in fight or flight, times of high stress, activated by epinephrine and norepinephrine

        • Parasympathetic division: Balances out sympathetic division, calms down

      • Motor system: Controls skeletal muscles

    • Spinal cord: Runs in a vertebral column, can carry out certain responses like reflexes (and then the brain tells itself it did it when really it didnā€™t fun little psych fact), conveys information from the brain

    • Central nervous system (CNS): The brain and the spinal cord

    • Forebrain: Contains the cerebrum which carries out high end functions

    • Midbrain: Integrates signals and delegates them to other parts of the brain

    • Hindbrain: Carries out regulatory actions and involuntary actions like breathing and heart rate

    • Peripheral nervous system: Nervous system other than the CNS, afferent and efferent neurons

    • Neuronal plasticity: The way the neurobiological system is changed after birth, changes occurs at synapses due to plasticity. Changes can strengthen or weaken signaling

    • Autism: Caused by disruption in activity-dependent remodeling at synapses, can lead to impaired communication, social interaction, and repetitive behaviors

    • Glutamate: Helps open up ion channels, can remove magnesium ions from blocking channels

  • Resting potential, depolarization threshold, voltage gated channels open, falling phase, undershoot

  • Outside/inside to find the equilibrium potential

  • If suddenly Na and K pumps stopped functioning, the resting membrane potential will drop to 0 mv, chemistry pretty much takes over and neutralizes the overall charge to 0

  • Organisms can have diverse nervous systems, like cnidarians with nerve nets that are overall spread, compared to cephalized organisms with a processing center (usually the head) and nerve cord(s) that branch

  • Learning:

    • Neurons compete for resources, only half of these synapses survive to adulthood

    • As specific neurons have the same synaptic connections, strength of the post synaptic response will strengthen over time, chemically the synaptic gap will be smaller and smaller if it is used a lot, increasing the signaling speed at which chemicals are transferred

    • Short term memory forms in the hippocampus but is recorded in the cortex, memories are accessed by a pathway through the hippocampus and into the cortex

    • Some long term memories can be directly accessed from the cerebral cortex without the hippocampus

    • Consolidation of memory occurs during sleep

    • Long term potentiation (LTP) is a form of learning, glutamate receptors increase the strength of synaptic transmission, if presynaptic neurons and postsynaptic neurons are stimulated at the same time glutamate receptors will be recruited more easily, increasing the efficiency of ion flow