Senses Flashcards
Why do we have senses
To get all our knowledge and experience of the world
They inform on external environment in which the organisms is located and on the internal environment I. Which organs tissues and cells reside
What are our senses
Vision hearing touch taste and smell
Pain temperature balance body position and movement
Transduction sending the sensory information to the nervous system
Specialised sensory cells detect specific stimuli and transducer them into Acton potentials that the nervous system will interperate
Eg vision photoreceptors detect light waves
Touch hearing and balance by mechanoreceptors
Taste and smell by chemoreceptors
What are the chemical senses
Gustation and olfaction
The chemical senses
The sesnses detect environmental chemicals they act as a quality control and. Heck substances if they are safe of toxic for ingestion
They have unusual strong and direct connection with most basic internal needs
The neural information from each system is processed in parallel and is ,edged at rather high levels in ceeebral cortex
The olfactory epithelium
When sniffing the odourus substance in air enters nasal cavity and gets caught on the mucus of epithiulim where they are dissolved and bind to receptors cells
Structure of the olfactory epithelium
Olfactory receptors are neurons have cilia and unmylinated axon penetrating cns
Supporting cells produce mucus basal cells are source of olfactory cells
Mucus flow replaced constantly every 10 mins presence of operant binding proteins which helps to concentrate the mucus
Structure of olfactory bulb
2 olfactory bulbs left and right located above the cribriform plate in forebrain
Olfactory cell axons enter bulb where endings contact with dentrites of second order olfactory neurones
Points of contact are called glomeruli
Olfactory transduction
Binding of operant molecule to operant receptor protein stimulates G protein activates camp which binds to cyclic nucleotide gates cation channel which then allows an+ and ca2+ influx which causes opening of ca2+ activated cl- channels
Leas to membrane depoarisation generate action potentials propagate up to cns
Termination of olfactory response
OderAnts diffuse away or are broken down camp activation of other signalling pathways end transduction
Olfaction receptor proteins
Express one or few of olfactory gpcrs
These have binding sit for the oderants on cel membrane an bind to different oderants
The zones of epithelium olfactory
Large zones each express specific olfactory GPCR group of genes
Within the zones cell types are randomly scattered however a particular kind of olfactory cell is only found in one zone
Olfactory bulb divided into 4 each typ of olfactory cell which from its epithelium sends its axon to only one or two glomerli in the olfactory bulb
Central olfactory pathways
Range of interactions between bulbs and glomerli
The second order of olfactory neurones project directly to different targets or indirectly through thalamus pathways are complex
Spatial and temporal representation of olfactory information.
Paradox- each olfactory receptor cell is sensitive to range of oderants
Humans can discriminate at least 10 to the power of 12 different combinations of odour stimuli
Olfactory population coding
Each odour is represented by large population of neurons
The higher number number of receptor cells the more accurate is odour discrimination
Temporal coding in olfactory system
Timing of action potentials
Sensation of touch
Somatic- refers to the body
If something touches your finger can accurately determine place and pressure sharpness and texture a single stimulus usually activists many receptors
Sensation of touch begins at skin
Two major types of skin hairy top of hand glabrous or hairless lips hand palm
Epidermis outer layer dermis hand palm
Largest sensory organ
Highly sensitive
Mechanoreceptors cells and the hairs hair grows from folliclesninvated by free nerve endings
Mechanoreceptors
Are sensitive to physical distortion
Types of skin mechanoreceptors
Pacinian corpuscle (pc)
Ruffinis endings
Meissnerz corpuscle
Merkels disk
Krause end bulbs
Mechanoreceptor cells field receptivity
Mechanoreceptors cells respond to specific frequencies pressures and receptive field sizes
Pacinian corpuscle compression
Capsule compression
Energy transferred to nerve terminal
Membrane deformation
Opening of mechanosesntive ion channels
Current causes local depolarisation
If threshold reached an action potential is generated
If prolonged pressure onion layers slip past each other due due to presence of viscous fluid between them transfer the energy which nullify the deformation and stop receptor potential
Mechanosensitive ion channels
Mechanoreceptor of the skin have all unmylinated axon terminals
Mechanosensitve ion channels are present in the axon membranes where convert mechanical force into ionic currents
Primary afferent axons
Skin is highly innervated by axons that follow vast network of perishable nerves going to the CNSaxons bring info to spinal cord or brain system
