Senses and Perceptions Flashcards
What is the function of specific sensory receptors
To convert stimulus into an electrical action potential
What type of cell is a sensory skin receptor
Pseudounipolar
What is the name of receptor and sensation for a mechanical stimulus
Mechanoreceptor
Touch
What is the name of receptor and sensation for a thermal stimulus
Thermoreceptor
Hot, cold
What is the name of receptor and sensation for a noxious stimulus
Nociceptor
Pain
What is the name of receptor and sensation for a chemical stimulus
Chemoreceptor
Taste, smell
What is the name of receptor and sensation for a light stimulus
Photoreceptor
Sight, vision
What is the name of receptor and sensation for a sound stimulus
Mechanoreceptor
Hearing
What is the name of receptor and sensation for a limb position stimulus
Proprioceter
Spatial awareness
What is the name of receptor and sensation for a blood pressure stimulus
Baroreceptor
What is a nerve receptor
A neuron with a cluster of peripheral nerve branches, each with a nerve ending
What is a receptive field
The distribution of a neurons receptors
What is two point discrimination
The ability to discern two separate mechanical stimuli
A measure of spatial awareness
An indication of receptive field size
How does two point discrimination relate to receptive fields and cortical representation
Areas with small two point discrimination have small receptive fields and large cortical representation
Give an example of an area with small receptive fields
Finger tips
Give an example of an area with large receptive fields
The trunk
How is a stimulus transduced
Stimulus causes change in receptor membrane permeability. This causes an influx of cations which causes depolarisation, changing the resting membrane potential. This generates an action potential
How are mechanoreceptors activated
Fore opens ion channel as structures tethered to the intracellular membrane move causing the pulling open of the channel
What are the different types of chemoreceptors
Ionotropic
G-protein coupled
How does a ionotropic chemoreceptor work
Binding to receptor protein causes opening of ligand gated channel leading to generation of AP
How does a G-protein coupled receptor work
Pore is recruited and chemical binds to receptor, causing channel to open
Chain of events takes longer so channel stays open for longer
How is the stimulus quality coded
Type of receptor
How are the stimuli magnitude and intensity coded
AP frequency
How are the stimuli duration and timing coded
Number of neurons activated
Duration of AP firing
How is the stimulus location coded
Where
How is action potential intensity coded
Frequency of AP discharge
High stimulus intensity = high AP frequency
How can APs adapt
Slowly and rapidly
What happens to neurons of the same function
They bundle together and are grouped into pathways
How are pathways specific
Modality specific eg - touch, pain, vision
Where are cell bodies of sensory neurons collected
In dorsal root ganglia
What are Ruffini’s and pacinian receptors related to
Slipping and vibration
Describe a hair follicle receptor
Axon is wrapped around receptor, when hair is pulled, the membrane is deformed - mechanical
What is the brachial plexus
Bundles of cables of sensory and motor axons providing innervation to the upper limb
What are the groups of nerves in the brachial plexus
Axillary Musculocutaneous Radial Ulnar Median
What is the epineurium
Tough connective tissue bundling nerves that supply separate skin regions
Describe A alpha axons
Thickest diameter and myelin sheath
Proprioceptors - sensory nerve that responds to position and movement
Describe A beta axons
Conduction velocity still quick but slower than A alpha - same for thickness of myelin sheath
Involved in i oculus tactile sensation and perception of mechanoreceptor in skin
Describe A delta axons
Small axon diameter, thin myelin sheath
Conduct APs pretty quickly but slower that A alpha and beta
Important in perception of sharp, stabbing pain
Also recruited in thermoreceptors
Describe C axons
Conduct APs slowly
Convey perception of dull aching pain
Where do sensory axons enter the CNS
Via the dorsal roots
Where do motor axons exit the CNS
Via the ventral roots
Describe the cervical spinal cord
Grey matter in the middle, surrounded by white matter
Dorsal surface closer to back, ventral surface closer to abdomen
Where are motor efferent axons derived from
Grey matter in the ventral horn - ventral root is motor axons only
Describe the trigeminal nerve
CN V
Ophthalmic and maxillary branch - sensory
Mandibular branch - motor
Which nerves control sensory pathways innervating the face
CNV
Which nerves control sensory pathways innervating the body apart from the head
Spinal nerves
Describe a sensory pathway
Primary sensory neuron in the periphery projecting into the CNS
Secondary sensory neuron in the CNS
Tertiary sensory neuron in the thalamus in the CNS
Describe the dorsal column - medial lemniscal all pathway
Mechanoreceptor (somatic)
A beta axon of secondary swaps to other side of the brain where it connects to the tertiary sensory neuron
It then projects to the appropriate region in the sensory cortex
Describe the posterior (dorsal) trigeminothalamic tract
Mechanoreception (trigeminal nerve)
Describe the spinothalamic pathway
Nociception (somatic)
Primary goes to spinal cord meeting secondary in dorsal horn, which crosses to the other side of the brain and ends in the thalamus. Tertiary goes from thalamus to sensory cortex
Describe the anterior (ventral) trigeminothalamic tract
Nociception (trigeminal nerve)
Why is the brain image distorted
The more sensory neurons that supply an area, the more brain space in the cortex
Areas with high density (small receptive fields) are represented more widely in the cortex
Sensation is recruitment of sensory pathways leading to appreciation of the stimulus
What is stereognosis
The ability to recognise objects by the feel alone
Requires a 3D mental image and need to compare with previous experiences - memory
Activates dorsal column pathway
What is proprioception
Appreciating where our body parts are in space without looking
Give examples of proprioception
Balance in the inner ear - utricle, saccule, semicircular canals, head posture, overall balance
Joint receptors - joint position, angle
Muscle receptors - muscle length tension
Periodontal receptors - tooth contact, bite force
