Lecture 3: The Nervous System

Neurons: a nerve cell that receives and sends signals within the body

Sensory neuron: a nerve cell that carries information into the brain and spinal cord. 

Motor neuron: A nerve cell that sends instructions from the brain and spinal cord out to nerves, muscles, and glands. 

Neurogenesis: The production of new neurons

Neuroglia: Nerve cells that support neurons and aid in neurotransmission

Neurotransmitter: A chemical substance released from a neuron that binds to a receptor and affects another cell. 

Soma: The cell body of a neuron

Nucleus: The part of a cell that contains genes that code for proteins

Axon: The long, wire-like part of a neuron along which electrical impulses are conducted away from the cell body. Neuron’s only have one axon, but the axon can split into numerous branches called collaterals

Myelin: A white fatty material that encloses and insulates some axons and speeds neurotransmission. 

Node of Ranvier: A gap in the myelin sheath of an axon, where action potentials are propagated. 

Axon terminal: the end of the axon, which contains vesicles of neurotransmitter

Vesicle: A small sac in the axon terminal that contains neurotransmitter molecules. 

Synapse: The gap between two nerve cells

Dendrites: The branched outgrowths from the soma, they are the main receptive surface of the neuron. 

Receptor: A protein molecule located on or in a cell, which responds specifically to a particular neurotransmitter, hormone, or drug. 

Action potential: The short-term change in electrical potential between the inside and outside of a neuron that leads to transmission of nerve signals. 

Depolarization: When the charge across the neuron is reversed, in a neuron, depolarization refers to the inside of a neuron becoming more positively charged compared with the outside. 

  • The neuron that releases neurotransmitter is called the presynaptic neuron, while the neuron the transmitter affects is the postsynaptic neuron. 

Steps of Neurotransmission

  1. The neurotransmitter is produced and packaged into vesicles, which are stored in the axon terminal 
  2. When an action potential travels down the axom and reaches the terminal it opens voltage-gated calcium channels. 
  3. Calcium enters the axom terminal from the extracellular fluid and causes vesicles containing neurotransmitters to fuse with the presynpatic membrane. 
  4. The neurotransmitter is then released into the synapse. 
  5. The neurotransmitter binds to receptors that are located on the dendrites of the postsynaptic neuron
  6. It causes ion channels on the postsynaptic neuron to open or close, allowing ions to flow into or out of the cell. 

  • Depending on the neurotransmitter, the target organ, and other factors, the postsynaptic cell may be excitatory or inhibitory

Ionotropic receptors: A type of receptor that is also an ion channel, when a substance binds, the receptor quickly opens, and an ion such as sodium or chloride rushes into the cell. 

Metabotropic receptors: A type of receptor that is separate from an ion channel, if a substance binds to the receptor, a series of events may open a separate ion channel or cause another change in the cell, but it happens relatively slowly

Presynaptic autoreceptors: A type of receptor located on the presynaptic membrane, which detects the presence of neurotransmitter in the synapse and sends a signal to inhibit synthesis or release of that neurotransmitter

Three ways neurotransmission stops: 1) reuptake, enzymatic degradation, and diffusion. 

Reuptake: the process by which a presynaptic neuron reabsorbs a neurotransmitter that it has released. 

Central Nervous System: The brain and spinal cord

Peripheral Nervous System: All the nerves going to and from the brain and spinal cord. 

Somatic Nervous System: Part of PNS, consists of nerves that carry sensory information into the CNS, as well as nerves that carry motor signals from the CNS to skeletal muscle cells. 

Innervate: To supply a part of the body with nerves, or to stimulate an area by a nerve. 

Neuromuscular junction: The site at which motor neurons from the somatic nervous system influence skeletal muscles

Autonomic nervous system: Part of the PNS, consists of nerves that go to and from smooth muscle, heart muscle, and glands. Regulates heart rate, blood pressure, digestion, urination. 

Sympathetic nervous system: Part of the PNS, the sympathetic nervous system regulates “fight or flight” impulses. 

Parasympathetic nervous system: Part of the PNS, the parasympathetic nervous system regulates result “business as usual” impulses. 

Cerebrum: Part of the forebrain containing the cerebral cortex, basal ganglia, and hippocampus. 

Cerebral cortex: the outermost portion of the brain hemisphere.

  • Left hemisphere is known for speech. Reading, writing, vocabulary and understanding language, as well as math skills. 
  • Right hemisphere is synthesis. Spatial perceptions, map reading, geometry, art, and musical appreciation, and emotions, intuitions,  understanding emotional tone. 

Corpus callosum: The band of nerve fibers that connect the left and right hemispheres of the brain. 

Frontal lobe: the part of the cerebrum responsible for planning, programming, speech, and initiating voluntary movements. 

Prefrontal cortex: The part of the cerebrum responsible for reasoning, judgements, and decision-making

Parietal lobe: The part of the cerebrum that contains the primary somanosensory area of the cortex, where sensations such as pain, temperature, and touch are processed. 

The temporal lobe: The part of the cerebrum that processes hearing, memory, and integration of sensory functions. 

Occipital lobe: The part of the cerebrum where visual images are sent. 

Insula: The fifth lobe of the cerebrum taht receives and responds to internal sensations and translates these into a conscious, subjective experience. 

Basal ganglia: a group of connected nuclei that influence muscle movement, emotions, and mood. 

Nucleus accumbens: An area in the basal ganglia that plays an important role in reward, pleasure, and addiction. 

Limbic system: involved in the control of emotions and memory, this entity includes the hypothalamus, hippocampus, and amygdala, among other areas. 

Hypothalamus: Part of limbic system. Integrates and controls the fighting, fleeing, feeding, and mating. Helps regulate blood pressure, heart rate, respiratory rate, body temperature. Produces horomone and coordinates response between emotional state and physical response. 

Thalamus: part of the forebrain that serves as the relay station of the brain. It sorts many sensory signals and sends them to the appropriate areas of the cortex. 

Pineal gland: one of our biological clocks that produces a substance called melatonin, which is involved in sleep and depression. 

Pituitary gland: sometimes called the master gland, it releases many important hormones. 

Tectum: part of the midbrain that contains nuclei that control’s eye movements, pupillary response to light, and reactions to moving stimuli, as well as auditory reflexes. 

Tegmentum: A neural network in the midbrain that is involved in many reflexive and homeostatic pathways. 

Periaqueductal gray: An area of the midbrain involved in pain control. 

Substantia nigra: Part of the midbrain that plays an important role in movement. 

Ventral tegmental area: An area of the midbrain involved in addiction, reward, and rational processing. 

Reticular formation: a network of nuclei involved in mediating levels of arousal and attention. 

Pons: Part of the brainstem that contains respiratory nuclei that help smooth out breathing patterns, it is also important in sleep and arousal. 

Brainstem: Part of the brain that includes the medulla oblongata, pons, and midbrain and controls basic vegetative processes and other automatic activities of the body. 

Medulla oblongata: Part of the brainstem that controls basic vegetative processes such as heart rate, blood vessel diameter, respiratory rate, coughing, swallowing,and sneezing. 

Cerebellum: Part of the hindbrain that helps control balance, posture, and coordination. 

Spinal cord: A longitudinal system of neurons and supporting tissue that carries signals between the brain and the peripheral nervous system. 

Blood brain barrier: The specialized capillaries that carry blood to the CNS, blocking the entry of certain substances. 

GABA: Gamma-aminobutryic acid is the major inhibitory neurotransmitter of the brain. When released, it is transformed to glutamate, and then carried into the axon terminal and turned into GABA again. Highly concentrated in the basal ganglia, hypothalamus, hippocampus, and brainstem. 

Glutamate: The major excitatory neurotransmitter in the central nervous system. 

AMPA receptors: The most common type of glutamate receptor.

NMDA: N-Methyl-D-aspartate is an important class of glutamate receptors that are involved in memory. Require two neurotransmitters to stimulate the receptor. glutamate + glycine or serine. Sodium and calcium enter 

Catecholamines: Neurotransmitters, including dopamine, norepinephrine and epinephrine, all of which have a similar structure and function.  Synthesized from Tyrosine and converted into DOPA, from which dopamine is synthesized. 

Serotonin: A neurotransmitter found throughout the brain and body. Involved in many functions, including mood, sleep, appetite, and visual perception. Synthesized in tryptophan. Converted to 5-hydroxytryptamine, then converted into serotonin. 

Acetylcholine: The first neurotransmitter to be discovered and the most common neurotransmitter in the body. 

Opioid: Any natural, synthetic, or endogenous substance that binds to the opioid receptor. 

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