Week 9- Sensory Receptor Physiology Flashcards
Define a stimulus
Change detectable by the body that exists in a variety of energy forms
What is a receptor?
Either a specialised ending of an afferent neuron or a cell body closely associated with the peripheral ending of the neuron that converts stimulus energy into action potentials
What is transduction?
The process by which stimulus energy is converted into action potentials at a receptor
What is meant by ‘perception’ of a stimulus?
what you receive as a stimulated being arises from multiple inputs from different senses
What are the categories of receptors?
- Photoreceptors
- Mechanoreceptors
- Thermoreceptors
- Osmoreceptors
- Chemoreceptors
- Nociceptors (pain receptors)
Define the term ‘compound sensations’
Perception that arises from integration of several simultaneously activated primary sensory inputs
What is processing of sensory input by the brain stem critical for?
Cortical arousal and consciousness
How does sensory stimuli have an effect on our emotions?
Afferent neurons send signals to limbic system, evoking responses that we don’t consciously notice, triggering emotional effects
How does stimulation of a receptor alter its membrane permeability?
Causes a non-selective opening of small ion channels. Receptor potentials or graded potentials are generated. These are then converted into APs if required for long-distance transmission
The intensity of a stimulus is reflected by what?
The magnitude of the receptor potential. The larger the receptor potential is, the greater the frequency of APs generated.
Also distinguished by the number or receptors activated within the area
What is ‘adaption’?
Where stimuli of the same intensity not always bring about receptor potentials of the same magnitude from the same receptor
What are the 2 types of receptors based on their speed of adaption?
Tonic receptors and phasic receptors
What are tonic receptors and where are they important?
- no not adapt or adapt slowly
- Important in situations where it s valuable to maintain information about a stimulus e.g. muscle stretch receptors
- Continue to generate APs, however, to relay information to the CNS
What are phasic receptors and where are they important?
- rapidly adapt
- adapts by no longer responding to a maintained stimulus
- When the stimulus is removed, the receptor has a slight hyperpolarisation “off response”
- Useful in situatons where it is important to signal a change in stimulus intensity
What are the 2 possible scenarios when the afferent information reaches the spinal cord?
- Reflex arc; bringing about an appropriate effector response when integrated in the spinal cord
- May be relayed up to the brain for further processing & possible conscious awareness
What are somatosensory pathways and what do they consist of?
Pathways conveying conscious somatic stimulation
consist of discrete chains of neurons, synaptically interconnected in a particular sequence to accomplish more sophisticated processing of the sensory information
What is a first order sensory neuron?
The afferent neuron thats peripheral receptor first detects the stimulus
What is a second order sensory neuron?
Located in either the spinal cord or the medulla, where the 1st order synapses onto
What is the 3rd order sensory neuron?
In the thalamus, where the 2nd order synapses onto
Where are particular sensory inputs usually projected?
defined areas of the somatosensory cortex
What does labelled pathways allow?
Allows the brain to decode the type and location of the stimulus
What is a receptive field?
The circumscribed region of skin in which each somatosensory neuron responds to stimulus. allows for differentiation of different stimuli on points of the skin
What is the relation between the size of a receptive field and the density of the receptors in the region?
The size of a receptive field varies inversely with the density of receptors in the region. The closer the receptor spacing, the smaller the area of skin each monitors
What factors influence acuity?
receptive field size and lateral inhibition
