HUBS1403 Lecture Notes - Lecture 28: Choline, Joint Capsule, Nociceptor
8 Jun 2018
School
Department
Course
Professor
Sensory Nervous System
Sensory System
Sensory Processing
Stimulation of sensory receptor
• Many different types of receptors
Transduction of the stimulus
• Converting a stimulus into an electrical signal
Transmission of sensory signal
• Generation of Aps from site of stimuli to CNS
Integration and perception of sensory signal
• Sensory signals are transmitted to the CNS and integrated at specialised sites before
perception occurs at the cortex
Sensory Receptors
How do we detect stimuli?
Receptors for a specific sensory modality are activated
Sensory modalities
Sensory Modality = what we consciously perceived to be the nature of the stimulus
General Senses
Special Senses
• Pain
• Temperature
• Touch
• Pressure
• Vibration
• Proprioception (sense of your body in space)
• Length of muscle
• How quickly the muscles are stretching
• Angle of joints
• Taste
• Smell
• Vison
• Hearing
• Equilibrium
but this is not actually the same as the stimulus itself, eg a 'smell' is the result of an molecule biding
to a receptor
Sensory receptors are differentiated on the basis of:
1. The receptor's 'labelled line' connection to CNS: determines interpretation of activity eg eye
2. Receptor specificity: nature of the adequate stimulus (the stimulus has to be of great enough
strength and has to be appropriate for that particular receptor)
3. Receptor structure: integral or separate to afferent neuro, occurrence of accessory cells or
structures
4. The receptive filed: dimension determines discrimination
5. The receptors adaptation profile: whether slowly or rapidly adapting
Labelled Line
Particular pathways that the receptor will travel along
Receptor Specificity
Adequate stimulus
Receptor
Receptor sub-types
Mechanical movement
Mechanoreceptors
tactile receptors
• Touch
• pressure
• Vibration
baroreceptors
• Changes in pressure
proprioceptors
• Stretch and angles
Damage- painful
Nociceptors
temperature-sensitive
mechanically-sensitive
chemically-sensitive
Temperature change
Thermoreceptors
cold-sensitive
warm-sensitive
Chemical
Chemoreceptors
Light
Photoreceptors
Particular stimuli will only activate certain types of receptors
Mechanoreceptors
Layer
Receptor
Types of stimulus
Superficial layers of skin
• Meisser's corpuscles
• Merkel's disks
• Fine touch and pressure
Deep layers of skin
• Pacinian corpuscles
• Rufini's endings
• Pressure, vibration and crude touch
Receptor Structure
Tactile mechanoreceptors of the skin
Unencapsulated
Structural
class
Functional classes according to location (L) and
stimulus type (S)
Body location
Free nerve
endings of
sensory
neuros
L: exteroceptors, interceptors, and proprioceptors
S: thermoreceptors (warm and cool),
chemoreceptors (itch, pH etc), mechanoreceptors
(pressure), nociceptors (pain, hot, cold, pinch, and
chemicals)
Most body tissues; most dense in
connective tissue (ligaments,
tendons, dermis, joint capsules,
periostea) and epithelia (epidermis,
cornea, mucous and glands
Modified free
nerve
endings:
tactile discs
(Merkel discs)
L: exteroceptors
S: Mechanoreceptors (light pressure); slowly
adapting
Basal layer of epidermis
Hair follicle
receptors
L: exteroceptors
S: mechanoreceptors (hair deflection); rapidly
adapting
In and surrounding hair follicles
Document Summary
Stimulation of sensory receptor: many different types of receptors. Transduction of the stimulus: converting a stimulus into an electrical signal. Transmission of sensory signal: generation of aps from site of stimuli to cns. Sensory signals are transmitted to the cns and integrated at specialised sites before perception occurs at the cortex. Receptors for a specific sensory modality are activated. Sensory modality = what we consciously perceived to be the nature of the stimulus. General senses: pain, temperature, touch, pressure, vibration, proprioception (sense of your body in space) Length of muscle: how quickly the muscles are stretching, angle of joints. Smell: vison, hearing, equilibrium but this is not actually the same as the stimulus itself, eg a "smell" is the result of an molecule biding to a receptor. Particular pathways that the receptor will travel along. Mechanical movement mechanoreceptors tactile receptors: touch, pressure, vibration baroreceptors, changes in pressure proprioceptors. Stretch and angles temperature-sensitive mechanically-sensitive chemically-sensitive cold-sensitive warm-sensitive.
