What are the two classifications of the senses?
General- somatic (body and environment)
-visceral (internal organs)
Special- highly localised receptors
What are the 4 kind of information sensory receptors transmit?
Modalities (form), location, intensity and duration
How can intensity of nerve signals be altered?
Alter firing frequency, recruit great number of nerves and use nerve fibres of different thresholds
What are phasic receptors?
They stop transmitting information even if stimulus continues
What do tonic receptors do?
Transmit information about the duration of a nerve impulse but they adapt slowly to stimulus
What is a receptor?
Any structure specialises to detect a stimulus
What are the 5 types of receptors?
Mechanoreceptors, chemoreceptors, photoreceptors, thermoreceptors and nociceptors
What do mechanoreceptors do?
They respond to mechanical stimulus such had bending or stretching of cells
What do chemoreceptors do?
They are membrane receptors that have chemicals become attached to them
What are photoreceptors?
They respond to light striking a receptor cell
What are thermoreceptors?
They respond to changes in temperature at site of receptor
What do nociceptors respond to?
Painful stimuli
What are the three major types of unencapsulated sensory nerve endings that are involved in general sensation?
Free nerve endings, merkels disc and hair follicle endings
What are the 6 major type of encapsulated sensory nerve endings that are involved in general sensation?
Meissen corpuscle, Krause end bulb, pacinian corpuscle, ruffini endings, muscle spindle and Golgi tendon.
What do meissners corpuscles detect?
Touch involved in two-point discrimination
What do ruffini endings detect?
Continuous touch or pressure
What does the pacinian corpuscle detect?
Deep pressure, vibration and proprioception
What does merkels disks detect?
Light, touch and superficial pressure
Where on the body are nociceptors not found?
The brain
Where on the body are nociceptors not found?
The brain
Where on the body are nociceptors not found?
The brain
What sort of pain in received from myelinated pain fibres?
Fast pain
What sort of pain is received from unmyelinated pain fibres?
Slow pain
What is somatic pain?
Pain arising from skin, muscles and joints. It can be superficial (sharp, stabbing and prickly) and deep (less localised and longer lasting)
What is visceral pain?
Pain arising from the internal organs
What are the chemicals injures tissues release that stimulates nociceptors?
Bradykinin (from blood protein), serotonin, prostaglandins, histamine and K+
What is referred pain?
Pain from viscera that is misinterpreted as coming from skin or other superficial structures
How does the CNS use to modulate pain?
Neuromodulators to block transmission eg. Endorphins or enkephalins or dynorphins
What are the sensory inputs we are aware of?
Sight, small, sound, touch and taste
What are the sensory inputs we are unaware of?
Body temperature, blood pressure and muscle tension
What is taste a result of?
The action of chemicals on the taste buds
Where are the taste buds?
They lie within the bumps on the tongue as well as on cheeks, soft palate, pharynx and epiglottis
What are the 4 types of bumps on the tongue called?
Lingual papillae
What are the 4 lingual papillae?
Filiform, foliate, fungiform and circumvallate
What are taste buds made up off?
Taste cells, supporting cells and basal cells that differentiate into taste cells
What are the 5 primary taste sensations?
Salty, sweet, sour, bitter and umami (meaty amino acids)
What is the olfactory mucosa?
A patch of epithelium made up of smell receptors in roof of nasal cavity
What are olfactory cells?
Replaceable neurons
What are taste cells?
Epithelial cells
What are the only neurons exposed to the external environment?
Olfactory cells
What is the life span of olfactory cells?
60 days
What are the 7 primary classes of odour?
Camphoraceous, musky, floral, pepperminty, ethereal, pungent and putrid
What is the definition of sight?
Perception of objects in an environment by means of the light they emit or reflect
What are the accessory structures to the eye?
Eyebrows, eyelids, conjunctiva, lacrimal apparatus and extrinsic eye muscles
What is the conjunctiva?
A vascular, transparent mucous membrane over eye
What is the lacrimal apparatus made up of?
A gland and duct that drains tears to nasal cavity
What does the tear system of the lacrimal apparatus contain?
Lacrimal gland, superior lacrimal punctum, superior lacrimal canal, lacrimal sac, inferior lacrimal punctum, inferior lacrimal canal and nasolacrimal canal
What are the 3 principal components of the sphere of the eye?
Tunica (3 layers that for lm wall), optical apparatus (admits and focuses light) and neural apparatus (retina and optic nerve)
What components of the eye is the retina part of?
Tunica and neural apparatus
What components of the eye is the cornea part of?
Tunica and optical apparatus
What are the 3 parts that make up the tunica?
Tunica fibrosis, tunica vasculosa and tunica interna
What is the tunica fibrosis made up of?
Sclera (white of eye) and cornea
What is the tunica vasculosa made up of?
Choroid (highly vascular, deeply pigmented layer behind retina), ciliary body (think extension of choroid forming muscular ring around lens) and iris
What determines your eye colour?
Amount of melanin
What is the tunica interna made up of?
Retina
What parts of the eye are that transparent elements that admit, bend and focus light?
Cornea, aqueous humour, lens and vitreous body
What is the retina?
A thin transparent membrane that is attached at the optic disc and ora serrata
Where is the macula lutea?
Directly posterior to centre of lens
What does the macula lutea do?
It is responsible for sharp, finely detailed images as it has a high concentration of cones and no rods
What is the optic disc?
The blind spot where all nerves and blood vessels pass
What happens in proliferative diabetic retinopathy?
Irregular new blood vessels are formed
What are pupillary constrictors?
Concentric circles of SMC that narrow pupil
What are pupillary dilators?
Spokelike myoepithelial cells that widen pupils
How is light bent in the eye?
By curvature of cornea towards centre of retina
What is the refractive index?
Measure of bending of a ray of light as it travels through different mediums of eye
What is the near response?
Eyes adjustment to close range vision
What are the 3 processes involved in the near response to focus an image on the retina?
Convergence of eyes, constriction of pupil and accommodation of lens
What is the closest an object can be at age 10 and 60 that can still be in focus?
7cm and 100cm
What lens would you use for someone with hyperopia (far sighted)?
Convex lense as uncorrected image is projected too far behind eye ball
What lens would you use for someone with myopia (short sighted)?
Concave lens because uncorrected eye projects image short of where it needs to be in eye ball
What are the 5 cellular layers of the eye?
Pigment cell layer, photoreceptor layer, bipolar layer, ganglion layer and nerve fibre layer
What is the pigment cell layer of the eye?
Retinal layer that absorbs light and reduces light scatter
What is found in the photoreceptor layer of eye?
Rods on the periphery of the eye that help see at night and cones in the centre of the eye that help see in the day and see colour
What cellular layer has largest neurons of retina?
Ganglion layer
What is the visual pigment in rods?
Rhodopsin (retinal and opsin)
What is the visual pigment found in cones?
Photopsin (retinal and a bit opsin)
Is retinal a pigment or a protein?
Pigment
Is opsin a pigment or a protein?
Protein
At what wavelength is blue light absorbed?
420nm
At what wavelength is green light absorbed?
534nm
At what wavelength is red light absorbed?
564nm