IB Biology: Neurones

13 flashcards · Other · by Gabrielle Wong

1. The nervous system

   Processing system to respond to the outside world

2. Types of nerves/neurones: central nervous system: brain and spinal chord peripheral nervous system: other nerves cranial nevres: 12 pairs of nerves emerging from the brain spinal nerves: come from spinal chord, 31 pairs relay neurones: the connection of sensory and motor neurones sensory neurones: take information to CNS motor neurones: take information to muscles

   Divisions are somewhat arbitrary since everything is connected anyways

3. Neurone structure: dendrite: nerve fibres branching out to increase surface area cell body axons: elongated nerve fibre Schwann cells: creates the Myelin sheath nodes of Ranvier: gaps in-between sheath synaptic terminals at the end

4. Nerve impulses

   The transmission of a one-way electrical signal from dendrite to axon

5. Action potential:

   Self-propagating wave of ions in and out of a neuron membrane (first starts with a receptor neurone which transmits physical stimulus into first potential once thershold potential is met)

6. Resting potential: state in which the neurone is ready to send an impulese, but isn't

   The charge at this point is -65 mV, created due to the sodium-potassium pump. Potassiums and in the neurone, soidum is out.

7. Threshold potential:

   point at whcih there is significant stimulus for a receptor neurone to transmit that stimulus into the first action potential ex. retina cells and light

8. The process of an action potential Depolarization: sodium channels open, sodium diffuses in, charge becomes +35 mV next part of axon opens up channels as a result reploraization: potassium repelled, potassium channels open, charge returns to -65 mV sodium-potassium pump must move potassium in and sodium out to return to resting channel

   Refractory period: type between repolarization and resting potential Hyperpolarization: occurs briefly when K+ ions are moving out, corrected by the pump

9. Action Potential Diagram

10. Saltatory Conduction: term for action potentials that are propagated from one node of Ranvier to the next, increasing the speed of transmission and lowering the amount of ATP used since the Na-K pump works less

    This occurs becuase the myelin sheath is an insulator, the cytoplasm is conductive, but the phospholipid bilayer Shwann cells prevent charge leakage

11. Neurotransmitter: small molecule (usually a single amino acid or derivative of a protein) that transport nerve impulses across synapses

    Example: acetylcholine, a excitatory neurotransmitter found especially between neurones and muscle fibres, bonds and generates one action potential by increasing the permability of the post-synaptic receptor to positive ions Broken down by acetylcholinesterase, choline reabosrboed for resuse, acetyl group binding to another choline

12. Transmision of a nerve impulse across a synaptic junction:

    Synapse: junction between neurones action potential travels to end of neurone ca+ ions diffuse in vesicles with nuerotransmietter fuse with membrane, release neurotransmitter neurotransmitter travels across synaptic cleft binds to receptor sodium channel opens, leading to one action potential enzyme degrades neurotransmitter ion channel closes neurotransmitter fragments diffuse

13. Insectides:

    Neonicotinoid insectides: new insectide chemcially similar to nicotine, binds to post-synaptic receptors that normally accept acetylcholine When bound: Action potential can't be propagated receptor is permanently blocked neonitinoid can't be broken down Result: -insect is paralyzed, eventually dies