Perception

Perception

1. To transform patterns of energy from an external or internal source to awareness

2. 1)Discriminate: To detect differences, 2) To recognise and 3) Act

3. Neural Mechanism

   • Brain is composed of separate cells
   • Neurons: Receive and integrate stimulation, have dendrites and spines
     • Types of neurons: Motor (efferent) and Sensory (Afferent)
     • Types of signals: Axon, Axon Tunnels and Vesicles
     • Gilal cells: Supportive function
     • Activate other cells: Receptor cells
     • Synapses: Functional connection between neurons
       • Synaptic Cleft: 0.2 - 0.5 milimetres wide
       • Release of transmitter substance: Takes <10MS for chemical to diffuse
       • Post synaptic Cell: Receptor sites for transmitters
         • Excitatory and Inhibitory post synaptic potential

4. Discharge of neuron:

   • Acting potential occurs when Na+ gates open causing a huge influx of Na+ ions
     • Depolarisation (EPSP): If the threshold of excitation is reached then all becomes permeable to Na+
       • Voltage activated gates open
     • Hyperpolarisation (HPSP): occurs when permeability to K+ ions increase, refractory period

5. Electrochemical activity of a nerve cell: Resting potential = 70mV, channels in membranes are selectively permeable to different ions

   • Unequal distributions of ions: Inside = high K+ and A- and outside =High Na+ and Cl -
     • Chemical gradient: sodium/potassium pump

6. Acting Potential

   • Size and shape of AP dependent on intensity of stimulus. ECG reflects summoned activity of acting potential
   • Propagates by saltatory conduction
     • Causes vesicles at axon terminal to release transmitter substance. Amount depends on frequency of action potential/voltage dependent Ca+ gates. Released in quantum amounts and diffuse across synpatic gap
   • Connections & Circuits in the nervous system: Neurons form circuits through multiple synaptic connections
     • Convergence and Divergence
       • Utilize excitatory and inhibitory connections