Lecture 10: the nervous system part II: sensory input Flashcards
What is signal transduction?
The conversion of environmental factors into neural information
Why are the five classic senses not well-considered?
They measure the same thing encompassed by different types of stimuli (i.e. different modalities)
What are the 5 types of signal modalities?
Mechanoreception Thermoreception Photoreception Chemoreception Nociception
What are 5 things measured by mechanoreception?
Pressure, body position, sound, acceleration and gravity
Where are hair cells involved in mechanoreception found?
The organ of Corti
Semicircular canals
The utricle and saccule
Where does thermoreception take place?
Free nerve endings in skin and core temp sensors in hypothalamus
What cell types are involved in photoreception?
Rod and cone cells
Name receptors involved in chemoreception
Olfactory receptors in nose
Gustatory receptors in taste buds
What does nociception measure?
Cellular damage (e.g. NK1 receptor for Substance P)
What are lamellar corpuscles also known as?
Pacinian corpuscles
What is the structure of lamellar corpuscles?
Dendrites surrounded by layers (lamellae) of connective tissue
How do lamellar corpsucles work?
When lamellae are distorted by physical pressure, dendrite membrane stretches, opening special sodium ion channels
What is the charges of a lamellar corpuscle when at resting potential?
Positive outside, negative inside
What happens when sodium rushes into the lamellar corpuscle?
Voltage-gated ion channels open and the signal travels down to the myelinated dendrite to soma and axon hillock, triggering AP down axon
What is proprioception?
perception or awareness of the body position or movement of the body
What do spindles respond to (and inform the brain of)?
Muscle length
Rate of change of length
What happens when muscles stretch to propriceptors?
They stretch and activate. There is an increased rate of action potential in the fibers
Pacinian corpuscles and muscle spindles are examples of _____ stimulation of sensory neurons
Direct
What is the magnitude of depolarisation of the membrane called?
The receptor potential or generator potential
Why is lamellar corpuslces considered an example of direct stimulation of sensory neurons?
Connective tissue sheath is not a cell
Where are pressure waves transmitted to inside the ear?
Vestibular duct
Hearing is an example of what type of sense?
Mechanoreception
What do sound waves cause to vibrate within the ear?
Connective tissue fibres in the tectorial membrane
When do sound waves cause connective tissue fibres in the tectorial membrane to vibrate?
When they match resonant frequency of the fibres
The tectorial membrane is bathed in what?
High potassium ion concentration
What are hair cells?
Modified epithelial cells
From what side of the hair cell does cilia project?
The apical side
The tallest cilium in each hair cell is called the…?
Kinocilium
What is the kinocilium linked to?
The stereocilia
What happens when the kinocilium is bend away from the sterocilia?
K+ channels open
When do K+ channels close in hair cells?
When kinocilia is bent towards the sterocilia
What happens when K+ channels open and depolarises hair cells?
Ca2+ channels open, causing neurotransmitter vesicles to migrate to membrane and dump NTs onto afferent neuron dendrites
What structure is used to detect acceleration and gravity?
Domes of extracellular gel with otoliths embedded in them
What happens to the domes of extracellular gel with otoliths embedded in them when your head moves?
Fluid moves past the dome, pushing it
Where are the acceleration and gravity sensing domes located?
One in each of the semicircular canals and one in the saccule
Hair cells are an example of what type of stimulation of neurons?
Indirect
Sensory receptors and sensory neurons encode what 4 types of information?
Stimulus:
Modality, location, intensity and duration
Sensory receptors encode what type of stimulus information?
Modality and location
Integrating centers interpret what types of information?
Modality, location, intensity. duration
What are the three pressure sensitive cutaneous receptors?
Ruffini’s endings, pacinian corpuscles, krause’ end bulbs
What are the three fine touch cutaneous receptors?
Meissner’s corpuscle
Merkel disks
Root hair plexus
What are the temperature and pain cutaneous receptors?
Free nerve endings
How is the location of a stimulus determined?
Integrating information from several cells, processing from the brain
How is stimulus intensity determined?
Frequency of APs
All receptors adapt, what are the two types and how fast do they adapt?
Tonic receptors adapt slowly
Phasic receptors adapt quickly
What system interprets APs?
Somatosensory system
Where is most tactile information (sense of touch) wired to in the somatosensory system?
Postcentral gyrus
How does the postcentral gyrus interpret information?
Different areas respond to different body parts (sensory homunculus)
