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Nervous System - Coggle Diagram
Nervous System
Structures
Integration Centres
Brain
Spinal Cord
Motor Output
Motor Neurons
Glands and Muscles
Sensory Input
Sensory Neurons
Receptors
Signal Transmission (Chemical Synapses)
Signal is conducted to the axon terminal
Synaptic vesicles fuse with presynaptic membrane (this is known as exocytosis) and neurotransmitters are released into the synaptic cleft
Neurotransmitters bind to the ligand-gated sodium channels of the postsynaptic cell, causing an influx of sodium cations and generating a signal
Removal of Neurotransmitters
Neurotransmitters can diffuse out of the synaptic cleft
Enzymes break down the neurotransmitters, the broken-down neurotransmitters are resynthesised into new ones and repackaged into new synpatic vesicles in the presynaptic cell
Reflexes
Monosynaptic (Knee-Jerk Reflex)
Patellar tendon is hit
Stretch receptors or the muscle spindle in the quadriceps is stimulated
Signal is generated in the sensory neuron
Sensory neuron conducts signal to the spinal cord
Signal is transmitted to the motor neuron
Signal is transmitted to the quadriceps muscle which contracts to make the knee jerk
Polysynaptic (Pain Withdrawal)
Hot object is touched or skin is pricked
Pain receptors under the skin are stimulated
Signal is generated in the sensory neuron
Sensory neuron conducts signal to the spinal cord
Signal is transmitted to the interneuron
Signal is conducted to the motor neuron
Signal is transmitted to the biceps, which contract to withdraw the hand
Signal is conducted to the brain and the experience is remembered
Signal Conduction (Saltatory Conduction)
Neuron
Axon
Myelinated Segment or Internodes
Made up of Schwann cells that wrap around the axon
The cell membranes of the Schwann cells prevent sodium cations from leaking, allowing for fast signal conduction
Since the signal is made of sodium cations that move via diffusion, the signal is gradually weakened by cytoplasmic resistance
Unmyelinated Segment or Nodes of Ranvier
Made up of Voltage-gated Sodium Channels
Open to allow an influx of sodium cations, regenerating the signal that was weakened by cytoplasmic resistance
Axon Terminal
Bulb-shaped
More synaptic vesicles
More surface area for exocytosis
Cell Body or Soma
Axon Hillock generates Action Potential
Integration of weak signals from highly-branched dendrites