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29 Cards in this Set
- Front
- Back
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Basic sensory pathway - 3 elements |
Stimulus response receptors Sensory Pathways - minimum 3 neurons w/ 2 synapses Conscious awareness - Contralateral sensory cortex |
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1st order neurons |
Dorsal root ganglion neuron Send axons into the spinal cord Cell body @ganglion |
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2nd order neurons |
Located in the CNS Crosses over Axons project to Thalamus |
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3rd order neurons |
Cell body is located in the thalmus - relay centre |
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Receptor function |
Coverts stimulus energy into nerve impulses Functions as a sensory transducer |
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Receptor features |
Specific - For their preffered stimulus (Lowest threehold) Variable structure - free nerve endings - specialised nerve-endings Classification based on - Location- somatic/ visceral / CNS / special senses Proffered stimulus type - Mechanical/ chemical / thermal / noxious or photic |
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Pacinian corpescule |
Detects Vibration - Laminar capsules acts as a filter - permits only high frequency disturbances to activate nerve Very rapidly adapting |
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Hair cells |
Sound energy -》 Electrical Signal - sound energy displaces sterocillia - activates ion channels - Depolarises cell, generating action potential Rapidly adapting |
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Rods and cones |
Light energy to electrical signals Rods - night vision - Double membrane disc- Large amounts of rhodospin Cones - Day vision - Outer segment of unfolding, small amounts of rhodopsin |
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Free nerve endings |
Transmit pain |
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Sensory transduction |
Conversion of stimulus energy into Action Potential in the sensory neuron 2 steps - Stimulus induces a receptor Potential - usually a depolarisation - If threshold is reached - Receptor potentual -》 Action Potential in the sensory nerve |
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Post synaptic Potentials |
Occur in dendrites or cell bodies of post synaptic neuron Excitatory post synaptic potential (EPSP) - Depolarisation brings membrane closer to threshold Inhibitory post synaptic potential (IPSP) - Hyperpolarisation moves the membrane potential away from threshold |
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4 qualities of a stimulus interpreted in sensory cortex |
Modality - What is it Location - Where is it Intensity - How strong is it Timing - How long does it last / Is it constantly or changing |
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Sensory unit |
A sensory nerve pathway and its receptive field |
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Modality - coding of sensory information |
A sensory unit projects to a specific area of the cortex - gives rise to sensation of preferred stimulus |
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Location- Coding of sensory information |
Sensory units are mapped in the cortex Precision is inversely proportional to the size of the receptive field |
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Intensity - Coding of sensory information |
Proportional to the rate of AP's The no. Of sensory units activated Recruitment of high threshold units |
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Timing - Coding of sensory information |
Duration of response Info. From rapidly adapting receptors |
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Adaptation of sensory receptors |
Decrease in receptor response to a constant stimulus - most receptors adapt Slow adapting - Give steady rate info. Muscle spindles and muscle length Rapidly Adapting - Gives info about rate of change in a stimuli e.g, pacinuan corpuscle and vibration Mechanism Chemical - visual pigment bleaching, na+ k+ pump Mechanical - Pacinuan corpuscles capsules |
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Receptive field |
Area of the body that when stimulated - results in a change in firing rate of sensory neuron 1st, 2nd and 3rd order neurons have receptive fields Complexity of receptive field increases proportionally w/ order of neurons Small receptive field = more precise identification and localisation |
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Mesissners corpuscule |
Point discrimination Fast adaptation Superficial Small receptive Field |
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Merkel disc |
Vertical idententation of the skin Light touch Slow Adaptation Superficial Small receptive Field |
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Pacinian Corpuscole's |
Vibration Tapping Fast Adaptation Deep Large receptive field |
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Ruffini Ending |
Skin Stretch Slow Adaptation Deep Large receptive field |
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Cutaneous mechenoreceptors _ touch |
Meissner's corpuscle - Point Discrimination Merkel disc receptor - Light touch Ruffini Ending - Vibration's Pacinian Corpuscle - Skin Stretch |
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Kinesthesia |
Sense of movement and position of limbs and other parts ofthe body |
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Proprioception in mechenoreceptors |
Muscle spindle receptors- Sensitive to change in muscle tension Golgi tendon organ's - sensetive to changes in muscle tension Joint receptors - Judging Position's |
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Function of Muscle stretch Reflex |
Muscle Tone Conscious position sense Regulation of Movement |
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Muscle Spindle - 2 Types |
Nuclear bag Fibres - 1-3 spindles, Central part of fibre, Contractile, attatched to the extra fusil Fibres Sensitive to rate of Change in muscle length - rapidly adaptive Association w/group 1A - Afferernt's Innervated w/gamma efferent motor neuron's
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