Lecture 28 Flashcards
What is the general name of the sensory receptors of the autonomic and somatic systems?
Somatic sensory receptors are the somatic and special receptors while autonomic receptors are the visceral receptors.
What is the most common form of sensory neurons?
Unipolar.
What are our special senses? What are our somatic and visceral sensations?
special: vision, hearing, taste, smell (and pheromones) and vestibular (for balance).
Somatic and visceral: Touch, pain, warm and cold and body position.
Where do all sensory signals travel?
To the central nervous system.
What seperates our special senses from the somatic and visceral senses?
Special senses tend to have specialised cells which convert the stimulus into the correct output before triggering a signal in the afferent neuron which will carry the signal on. Somatic and visceral neurons instead tend to travel straight to the CNS once triggered by the stimulus.
What is modality?
Modality refers to the type of sensory receptor activated, different neurons have differing modalitys.
What parts are involved in conscious sensations?
A sensory receptor converts the stimulus into an action potential (the transduction step), this action potential travels up the afferent neuron through a tract to the cerebral cortex where it is percieved as a conscious sensation.
What four information types describe a sensory stimulus?
Modality: the type of sensory receptor activated
Intensity: The frequency of action potential firing in afferent neurons
Duration: how long the action potential is firing in the afferent neuron.
Location: Where the sensory receptor that has been activated is located, this is ‘mapped’ in the brain.
What is proprioception? Which receptors are associated with this?
Proprioception is to do with detecting body position and posture. This is maintained with proprioceptors like the length receptors (which utilise muscle spindle to detect length change and cause the stretch response if a muscle is stretched, helping to maintain posture), or the tension receptors (sensed by golgi tendon organ and causes the tension relex and helps air in relaxation as well as tearing protection for the muscle).
What sensory receptor allows us to feel pain?
Free nerve endings.
What sensory receptors are used in touch and what are their functions?
Krause’s end bulb (textural sensation), Pacini’s corpuscle (deep pressure/high frequency vibration), Merkel endings (light pressure), Meissner’s corpuscle (low frequency vibration), Ruffini’s corpuscle (crude and persistent touch).
What does an increase in stimulus intensity cause? How does it do this?
Increased stimulus intensity increases the action potential frequency, this is because the relative refractory period is overcome by stronger input, hence threshold is reached more often.
What is adaptation as it applies to sensory receptors?
A decreased receptor potential over time due to continuous stimulation, this is because sensory receptors mostly rspond to change in conditions.
What is a receptive field?
A receptive field is the area upon which a neuron acts, a stimulus within this area will trigger the neuron, hence larger receptive fields mean that signals are harder to distinguish.
What is the afferent pathway for touch and posture? What path does it take?
The Medial lemniscal pathway, it travels along the dorsal column and involves three neurons in relay with one another. The primary sensory neuron is from the peripheral to the medial lemniscus (roughly in the medulla), there it crosses sides and synapses with the secondary sensory neuron which synapses in the thalamus where the tertiary neuron synapses with the somatic sensory area of the cerebral cortex. An example is the muscle spindle fibres.
