Nervous coordination and muscles

• Nervous System


  Uses nerve cells to pass electrical impulses along their length. Stimulates target cells through the release of neurotransmitters to allow for rapid communication between specific parts of an organism (e.g. a reflex arc)
• Hormonal System


  Produces chemicals (hormones) that are transported in the blood plasma to target cells. Stimulates target cells by increasing hormone concentration, allowing for a slow and long lasting communication at the target cells of the organism (e.g. controlling blood glucose level)
• Cell Body


  A part of a neurone that contains usual cell organelles including a high number of endoplasmic reticulum. Also associated with the production of proteins and neurotransmitters
• Dendrons


  A part of a neurone that is an extension of the cell body, divided into small branched fibres (dendrites) to carry a nervous impulse towards the neurone from the previous cell
• Axon


  A part of the neurone that is a single long fibre which carries nervous impulses away from the cell body
• Schwann Cells


  A part of the neurone that surrounds the axon, serving as protection and electrical insulation, whilst carrying out phagocytosis and assisting in nerve regeneration. These wrap around the axon many times so that there are multiple layers of membrane surrounding the axon.
• Myelin Sheath


  A part of the neurone that is comprised of multiple Schwann cells that run along the axon. The membranes of the Schwann cells are rich in the lipid myelin
• Nodes of Ranvier


  A part of the neurone that is not protected by a myelin sheath and acts as small constrictions between myelinated sections. These are important as they allow for the depolarisation of the next section of the axon
• Sensory Neurone


  A type of neurone that transmits nervous impulses from a receptor to an intermediate neurone. Contain one dendron that is very long to carry the impulse towards the cell body, and one axon to carry the impulse away from the cell body

  
• Motor Neurone


  A type of neurone that transmits nervous impulses from an intermediate neurone to an effector. Contains a long axon and many short dendrites

  
• Intermediate Neurone


  A type of neurone that transmits nervous impulses between neurones. Contains many dendrites and has many short processes

  
• Resting Potential


  A state of the neurone that is maintained in three ways:

  1) Sodium-potassium pump allows 3Na+ to leave and 2K+ to enter the membrane

  2) Sodium ion channels remain closed to prevent sodium movement

  3) Potassium ion channels remain open to allow for diffusion out of the membrane

  The outside is always more positive than inside the membrane
• 65mV


  The normal resting potential of humans
• 50-90mV


  The range of resting potential for organisms that have nervous impulses
• 40mV


  The normal charge of depolarisation in humans
• Depolarisation


  The process by which a stimulus forces the sodium voltage-gated channels to open, allowing for an influx of sodium ions, making the axon membrane much less negative.

  From this, the sodium voltage-gated channels close and potassium channels open, allowing for the movement of potassium out of the membrane

  
• Hyperpolarisation


  The process by which the outward movement of potassium ions from the axon membrane causes an overshoot of an electrical gradient, forcing the inside of the membrane to be too negative. This forces the closing for potassium channels

  
• Refactory Period


  The time it takes after hyperpolarisation for the electrical overshoot to be restored back to resting potential after an action potential has occurred

  
• Repolarisation


  The process by which an axon membrane returns to resting potential after being depolarised
• Saltatory Conduction


  The process by which an action potential can "jump" from one node of Ranvier to the next from the electrochemical gradient
• Unmyelinated Action Potential


  The process of an action potential travelling along an axon. The process starts at depolarisation at one end, which stimulates depolarisation at the next section of the axon, allowing for gradual movement along the axon
• Myelinated Action Potential


  The process of an action potential travelling along an axon. The process starts at depolarisation at one end, which allows for saltatory conduction of the impulse to the next node of Ranvier, allowing for gradual movement along the axon
• Diameter of Axon


  A factor that affects the speed at which an action potential travels. If this factor is larger then there is less leakage of ions from the axon which allows for faster conduction
• Temperature


  A factor that affects the speed at which an action potential travels. If this factor is higher then there is better function of enzymes to allow for more efficient respiration and a faster transfer of ions, which allows for faster conduction along the axon
• Myelination


  A factor that affects the speed at which an action potential travels. A neurone that doesn't have this will not be able to undergo saltatory conduction, therefore the passage of the nervous impulse will happen more slowly (3x more slowly)
• Threshold Value


  The level of stimulus which will allows for the all-or-nothing principle. Below this level, there will be no action potential, but reaching this level will allow for an action potential
• Strong Stimulus


  This type of stimulus can be identified in two ways:

  1) Multiple impulses within a given time frame

  2) Different neurones are stimulated with different threshold values
• Weak Stimulus


  This type of stimulus can be identified in two ways:

  1) Few impulses within a given time frame

  2) Few neurones are stimulated with only similar threshold values
• Purpose of Refactory Period

  A factor that helps an action potential by ensuring action potentials travel in one direction only, producing discrete impulses (separates impulses) and limits the number of action potentials
• Synaptic Cleft


  The space between the presynaptic neurone and the postsynaptic neurone
• Synaptic Knob


  The end of a neurone that is swollen and contains many mitochondria and endoplasmic reticulum
• Synaptic Vesicles


  The location by which neurotransmitters are stored before they are released into the synaptic cleft
• Unidirectionality


  The movement of neurotransmitter from the presynaptic to postsynaptic neurone, in one direction
• Spatial Summation


  Where multiple presynaptic neurones release neurotransmitter to meet the threshold value, to trigger an action potential at one postsynaptic neurone
• Temporal Summation


  Where one presynaptic neurone releases neurotransmitter to meet the threshold value, to trigger an action potential at one postsynaptic neurone
• Inhibitory Synapse


  A type of synapse that makes a new action potential less likely to occur by releasing a specific type of neurotransmitter to release chloride ions (allowing for movement into the postsynaptic neurone) and opens nearby potassium channels (allowing for movement out of the postsynaptic neurone). This makes the postsynaptic neurone more negative, making it harder for the threshold value to be met
• Cholinergic Synapse


  A type of synapse that has the neurotransmitter acetylcholine. These are common in vertebrates, involved in the CNS and at neuromuscular junctions
• Morphine and Codeine


  Drugs that will mimic endorphins by blocking the sensations of pain
• Prozac


  A drug that will interfere with serotonin levels to restore them to a normal state (acts as an antidepressant)
• Valium


  A drug that prevents the inhibiting of action potentials by the neurotransmitter GABA, allowing for continued stimulation