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Mammalian Nervous System

Edexcel A-level BiologyTopic 12 of 1638 lessons

Revision notes for Mammalian Nervous System in Edexcel Biology B (9BI0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. Nervous SystemAnimals respond to changes in their surroundings using two coordination systems: the nervous system and the endocrine (hormonal) system.
  2. Structure and Function of NeuronesA neurone is a nerve cell specialised to carry electrical impulses.
  3. Nerve ImpulsesA nerve impulse is a self-propagating wave of electrical activity that travels along the membrane of a neurone.
  4. Myelinated NeuronesIn vertebrates, many neurones are myelinated: their axons (and the dendrons of sensory neurones) are wrapped in a myelin sheath.
  5. Speed of Nerve ImpulsesThe speed at which an impulse travels along a neurone, its conduction velocity, depends on three main factors.
  6. Investigating Nerve ImpulsesMuch of what we know about nerve impulses came from experiments by Hodgkin and Huxley in the 1940s and 1950s on the giant axon of the squid.
  7. Resting PotentialWhen a neurone is not transmitting an impulse, there is a potential difference of about −70 mV across its membrane, with the inside negative…
  8. Action PotentialAn action potential is a brief reversal of the potential difference across the membrane of a neurone, from about −70 mV (inside negative) to about…
  9. DepolarisationDepolarisation is the change in the potential difference across a neurone membrane from its resting value (about −70 mV) towards zero and then above…
  10. RepolarisationRepolarisation is the return of the membrane potential from its positive peak back towards the negative resting potential.
  11. HyperpolarisationHyperpolarisation is the brief period after repolarisation when the membrane potential becomes more negative than the resting potential, falling to…
  12. Refractory PeriodAfter an action potential there is a short time during which the axon membrane cannot be stimulated to produce another action potential, or can only…
  13. Transmission of Nerve ImpulsesAn action potential at one point on an axon triggers an action potential in the region next to it, so the impulse moves along the neurone as a wave…
  14. Saltatory ConductionIn a myelinated neurone, the myelin sheath insulates the axon membrane so ions cannot move across it, except at the nodes of Ranvier.
  15. SynapsesA synapse is the junction between two neurones, or between a neurone and an effector cell such as a muscle fibre (a neuromuscular junction).
  16. Pre-synaptic MembraneThe events at the presynaptic membrane turn an electrical signal (the action potential) into a chemical one (the release of neurotransmitter).
  17. Post-Synaptic MembraneThe postsynaptic membrane converts the chemical signal back into an electrical one.
  18. NeurotransmittersA neurotransmitter is a chemical released from a presynaptic neurone that diffuses across a synaptic cleft and binds to receptors on a postsynaptic…
  19. DrugsMany drugs, both medicines and recreational drugs, work by affecting synaptic transmission.
  20. NicotineNicotine is the drug in tobacco.
  21. LidocaineLidocaine is a local anaesthetic.
  22. Cobra VenomCobra venom contains toxins that act on the nervous system.
  23. Sensory ReceptorsA sensory receptor is a cell, or group of cells, that detects a stimulus.
  24. The Human EyeThe eye is a sense organ that focuses light onto a layer of photoreceptors, the retina, and sends information to the brain along the optic nerve.
  25. The RetinaThe retina is the light-sensitive layer lining the back of the eye.
  26. RodsRods are photoreceptors that work in dim light.
  27. ConesCones are photoreceptors that work in bright light and give detailed, colour vision.
  28. Colour VisionHumans can see colour because there are three types of cone, each containing a different form of iodopsin.
  29. Formation of the BrainThe brain and spinal cord develop from a structure in the early embryo called the neural tube.
  30. Major Areas of the BrainThe human brain is part of the central nervous system (CNS).
  31. Other Areas of the BrainAs well as the cerebrum, cerebellum and medulla oblongata, several smaller regions lie deep inside the brain.
  32. Spinal CordThe spinal cord is part of the central nervous system.
  33. Reflex ResponsesA reflex is a rapid, automatic (involuntary) response to a stimulus.
  34. Peripheral Nervous SystemThe nervous system has two main parts.
  35. Voluntary Nervous SystemThe voluntary (somatic) nervous system is the part of the peripheral nervous system that controls skeletal muscles.
  36. Autonomic Nervous SystemThe autonomic nervous system (ANS) is the part of the peripheral nervous system that controls the internal organs automatically, without conscious…
  37. Sympathetic Nervous SystemThe sympathetic nervous system prepares the body for action in stressful or dangerous situations: the 'fight or flight' response.
  38. Parasympathetic Nervous SystemThe parasympathetic nervous system is most active when the body is at rest.

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