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Nervous System

Nervous System. Nervous System. Made up of nerve cells called neurons found in the: Brain Spinal Cord All of the nerve cells connected to all other parts of the body. Nervous System. The nervous system can be divided into the: Central Nervous System – brain and spinal cord

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Nervous System

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  1. Nervous System

  2. Nervous System • Made up of nerve cells called neurons found in the: • Brain • Spinal Cord • All of the nerve cells connected to all other parts of the body

  3. Nervous System • The nervous system can be divided into the: • Central Nervous System – brain and spinal cord • Peripheral Nervous System – neurons outside the spinal cord/brain

  4. PNS • The PNS is made up of: • Sensory neurons (affector neurons) – detect changes in the external and internal environment and sends information to the CNS • Motor neurons (effector neurons) – send information away from the CNS to muscles and other effector organs

  5. PNS • The motor neurons of the PNS can be further divided into 2 categories: • Autonomic nervous system – involuntary, transmits messages to internal organs • cannot be consciously controlled by thoughts • Somatic nervous system – voluntary, transmits messages to skeletal muscle • can be consciously controlled

  6. CNS • The CNS acts as the control centre of the entire nervous system: • It processes the information received by the sensory neurons in the PNS; and • sends messages back through motor neurons in the PNS to the effector organs, initiating a response.

  7. Summary Nervous system CNS PNS Sensory Motor Voluntary Involuntary Spinal Cord Brain Autonomic Somatic

  8. Nerve cells, Neurons • These are the basic units of the nervous system • There are 3 main types: • Sensory (affector) • Motor (effector) • Interneurons (connecting neurons) • When many neurons are connected together in a bundle, they are called a nerve

  9. Typical motor neuron

  10. Reflex arc

  11. Neurons • Neurons are able to pass messages onto other neurons and cells by sending electrical impulses called action potentials • Electrical impulses are created by a rapid change in positive/negative charges across the membrane of the neuron • Electrical impulses are generated when a stimulus is detected

  12. Action Potentials • There are 4 main phases in an action potential: • Resting potential – when neuron is not active/stimulated - there is a difference in charge across membrane, called potential • More + outside membrane compared to inside

  13. Action Potentials • Depolarisation – when the neuron is stimulated the potential reverses and this change in potential is carried along the axon to the axon terminal, causing a signalling molecule called a neurotransmitter (within the secretory vesicles) to be released • This neurotransmitter then diffuses across a very short distance (called a synapse) to the neighbouring (postsynaptic neuron, causing it to be stimulated

  14. Action Potentials • Repolarisation – The potential returns to resting state • More + outside membrane compared to inside • Refractory period – For a brief period after repolarisation, the neuron cannot be stimulated again http://www.learner.org/channel/courses/biology/archive/animations/hires/a_neuro1_h.html

  15. http://www.learner.org/channel/courses/biology/archive/animations/hires/a_neuro2_h.htmlhttp://www.learner.org/channel/courses/biology/archive/animations/hires/a_neuro2_h.html

  16. Depolarisation – stimulus reached threshold Resting potential Repolarisation

  17. K+ flows out of neuron Na+ comes into neuron

  18. Animations • http://outreach.mcb.harvard.edu/animations/actionpotential.swf

  19. Toxins and venom • Toxins and venoms produced by animals such as snakes and spiders can cause paralysis • This is because they can: • interfere with the release of neurotransmitters • Prevent transmission of electrical impulses from travelling along the axon • Damage the presynaptic or post-synaptic membranes

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