Sensory perception Flashcards
What is the PNS broken down into?
- Afferent division
- Efferent division
What is the function of the afferent divison?
“carry to”, sending information from internal and external environment to CNS
What is the function of the efferent division?
“carry from’, sending information from the CNS to muscles and glands
What is the afferent division of the PNS broken down into?
- Visceral afferent
- Sensory afferent
What is the function of the visceral afferent?
Incoming information from internal viscera
What is the sensory afferent (from the afferent division - PNS) broken down into?
- Somatic
- Special senses
What is the function of the somatic of the sensory afferent?
Sensation from body surface and proprioception
What is the function of the special senses of the sensory afferent?
Vision, hearing, smell, taste
What is a stimulus?
A change detectable by the body
What is the stimulus perceived by?
Receptors - structures at peripheral endings of afferent neurons
What is the function of receptors?
They convert stimuli into electrical signals
What is the sequence from stimulus?
Stimulus - Receptor - Receptor potential - Action potential
What is sensory transduction?
From stimulus - Receptor - Receptor potential
What is a sensory system comprised of?
- The sensory receptors
- Their axonal pathways
- Target areas in the brain involved in perception
Give another name for stimuli.
Modalities
Give examples of modalities
light, sound, pressure, taste, smell
What are the sensory system modalities?
SYSTEMS
- Visual
- Somatosensory
- Auditory
- Olfactory
- Gustatory
What are outside receptors called?
Exteroceptors
What are inside receptors called?
Interoceptors
What are the vision receptors?
Photoreceptors
What are the touch, balance, proprioception, hearing receptors?
Mechanoreceptors
What are the temperature receptors?
Thermoreceptors
What are the smell, taste receptors?
Chemoreceptors
What are the pain receptors?
Nociceptors
What is the stimulus of photoreceptors?
Light
What is the stimulus of mechanoreceptors?
Mechanical energy (stretching muscle, hair cell movement)
What are the stimuli of thermoreceptors?
Heat and cold
What is the stimulus of chemoreceptors?
Specific chemicals (O2, isoamyl acetate)
What are the stimuli of nociceptors?
Excessive pressure, excessive temperature, certain chemicals
Where do primary afferent axons enter the spinal cord?
Through the dorsal roots
Where are the somas of the primary afferent axons?
In the dorsal root ganglia
What do skin receptors lack?
Aalpha
What are the unmyelinated fibres?
C fibres
What are the axons from muscles involving Aalpha
Group I
What are the axons from muscles involving Abeta?
Group II
What are the axons from muscles involving Agamma?
Group III
What are the axons from muscles involving C fibres?
Group IV
What is the speed of Aalpha fibres?
80-120m/sec
What is the speed of Abeta fibres?
35-75 m/sec
What is the speed of Agamma fibres?
5 - 30
What is the speed of C fibres?
0.5 - 2 m/sec
What are the sensory receptors of Aalpha fibres?
Proprioceptors of skeletal muscles
What are the sensory receptors of Abeta fibres?
Mechanoreceptors of skin
What are the sensory receptors of Abeta fibres?
Pain, temperature
What are the sensory receptors of C fibres?
Temperature, pain, itch
What happens if there’s a larger axon diameter?
It will have lower resistance for the current to flow down the length of the axon
What do unmyelinated sheaths have to account for ion leakage across the membrane?
Have voltage regulated channels relatively close to each other
How are the conduct impulses in unmyelinated sheaths? (speed)
Relatively slowly
What is the only [lace where ion leakage occurs in myelinated sheaths?
Nodes of Ranvier
What do Nodes of Ranvier have? (present, function)
With voltage-gated Na+ channels)
Where are action potentials generated at in myelinated sheaths?
At nodes of Ranvier
What type of conduction is present in myelinated sheaths? (and explain)
Saltatory conduction - travel from node to node
Defn Nodes of Ranvier
Myelin-free gaps between segments containing voltage-gated Na+ channels
What does myelin provide (increase velocity)
Provides 50-fold increase in conduction velocity
What does the stimulus induce in either the receptor cell or in the free nerve ending?
Graded potential
What is graded potential proportional to?
Proportional to stimulus strength
Where do receptor potentials occur?
In separate receptor cells
Where do receptor potentials occur?
In separate receptor cells
What are the steps in receptor potentials?
- Stimulus opens ion channels in receptor causing graded membrane potential
- Receptor cell releases chemical messenger
- Chemical messenger opens ion channels in afferent neuron AP generating region
- If threshold reached, AP is generated
Where do generalised potentials occur?
In specialized nerve endings
What are the steps in generator potentials?
Stimulus opens ion channels in receptor causing local current flow
• Local current flow opens ion channels in afferent neuron AP generating region
• If threshold reached, AP is generated
What is the receptive field of a sensory neuron?
A region of space in which the presence of a stimulus will alter the firing of that neuron.
Give examples of receptive fields
- Hair in the cochlea
- Piece of skin
- Retina,
- Tongue
What is transduction?
The process of converting energy forms into electrical signals via a receptor / generator potential which triggers an action potential if it is large enough to reach threshold.
