The senses Flashcards
what is a sensation
conscious and subconscious awareness of change in the internal and external environment
Perception
conscious awareness and interpretation of sensations.
- primary function of the cerebral cortex
4 elements for sensation
- stimulation of sensory receptor
- Trabsduction of the stimulus (change in membrane potential)
- Generation of nerve impulses
- Integration of sensory input
Sensory receptors - free nerve endings
bare dendrites, lack any obvious structural specialisation
encapsulated nerve endings
dendrites enclosed
separate cells
receptors for taste, olfaction, vision and hearing
exteroreceptors
- located at the external surface of the body
- ## respond to stimuli that originate from outside the body
Interoreceptors
- located in blood vessels, muscles and in the nervous system
- monitor the internal environment
Proprioreceptors
- located in the muscles, tendons and joints
- provide info. about body position, muscle length and tension
mechanoreceptors
- respond to mechanical stimulation such as stretching or bending of cells
thermoreceptors
- respond to changes in temperature
Nocioreceptors
- respond to painful stimuli in the mouth, nose and body fluid
photoreceptors
respond to light
chemoreceptors
respond to chemicals in the mouth, nose and bodily fluids
osmoreceptors
respond to changes in the osmotic pressure of body fluids
Adaptation
where the response produced by the sensory receptor (e.g. the graded potential) becomes smaller when the stimulus is presented over a prolonged, sustained period. Thus, the number of action potential reduces.
somatic sensations
sensations that arise from receptors
- skin, mucous membranes, muscles, tendons, joints
Tactile sensations
touch pressure vibration itch tickle by mechanical stimuli
receptors in the skin responding to touch
corpuscle of touch
hair root plexuses
type 1 and 2 cutaneous mechanoreceptors
receptors that respond to pressure
- corsucle of tuch
- type 1 cutaneous mechanoreceptors
lamellated corpsucles
receptors that respond to vibration
corpsucle of touch
Lamellated corpsucle
respond to itch and tickles
- free nerve endings
- for itch, the free nerve endings respnds to chemicals released during inflammatory response
respond to thermal sensation?
thermoreceptors
painful stimuli ?
nocioreceptors
2 types of pain
slow pain - pain begins seconds after stimulus and gradually increases in intensity over the course of seconds to minutes e.g. burning, throbbing.
Fast pain - acute, sharp. pain occurs rapidly after stimulus.
superficial somatic pain
pain that arises from stimulation of nocioreceptors in the skin
deep somatic pain
pain that arises from stimulation of nocioreceptors in skeletal muscle joints/tendons
Visceral pain
pain that arises from the stimulation of nocioreceptors present in visceral organs
function of propriorecptors
enable us to determine the location of our body in space
- found in muscles and tendons and degree of stretch and contraction.
Proprioreceptors in muscles ?
- muscle spindles
monitor changes in length of skeletal muscles and stretch reflexes
proprioreceptors in tendons
tendon organs
provide information related to muscle tension
Proprioreceptors in joints
Joint kinaesthetic receptors
- sense joint position and movement
- respond to joint pressure, and the acceleration and deceleration of joints during movements
What type of stimuli respond to taste and small
chemical senses
Due to interactions of oderants and tastants
involves 3 types of cells
olfactory cells
- bipolar cells (one dendrite + one axons)
- involves the olfactory bulb - by the axon
- olfactory epithelium - where oderants are detected
supporting cell
epithelial cells of mucous membrane ling the nose
- provide physical support, nutrients and electrical insulation for olfactory cells
basal stem cells
continually undergoes cell division
responsible for the continued production of new olfactory receptor cells
Olfactory glands
- produce mucous that is secreted onto the olfactory epithelium
- the mucus moistens the epithelium and dissolves oderants
effect of an oderant binding to an olfactory receptor
- leads to generation of a depolarising graded potential
- if the depolarisation is large enough, action potentials are generated and nerve impulses are sent to CNS
Role of olfactory nerve
- pathway of olfactory information to the CNS.
- the axons in the olfactory nerves terminate in the frontal lobes.
- axons travelling in the olfactory tract project to the primary olfactory area of the cerebral cortex. Others goes to hypothalamus involved in memories and emotion
5 primary tastes
- bitter
- sour
- salty
- sweet
- msg
receptors of taste
- supporting cells = surround the gustatory cells and provide support
- gustatory receptor cells - responsible for detecting chemicals.
- basal cells - stem cells that provide supporting cells
effect of the binding of a tastant (chemical dissolved in saliva) to a taste receptor ?
- generation of depolarising graded potentials and the release of transmitter = stimulates sensory neurons that project to the CNS
Pathway of gustatory information to the CNS ?
- 3 cranial nerves = vagus, glassopharyngeal nerve and facial nerve.
- medulla oblongata
- hypothalamus and thalamus
- cortex
