SENSORY SYSTEM Flashcards
Sensation
Activation of sensory receptor cells at level of stimulus
Perception
Ability to see, hear or become aware of senses; dependant on sensation but not all sensations are perceived
Receptors
Cells or structures that detect sensations
Transmembrane protein receptors
Activated by ligand chemicals that usually open ion channels
Transmembrane proteins
Sensitive to mechanical or thermal changes and increase ion flow across membrane
3 receptor structures:
- Free ending of dendrites
- Encapsulated ending
- Specialized receptor cell
Free ending of dendrites
Embedded in tissue and receives a sensation (pain and temperature receptors)
Encapsulated ending
Encapsulated in connective tissue that enhance sensitivity (pressure and touch receptors)
Specialized receptor cell
Has structural components to interpret a specific type of stimulus (light receptors)
Exteroreceptors
Receptors located near a stimulus in the environment (somatosensory receptors located in skin)
Interoreceptors
Receptors that interpret stimuli from internal organs and tissues (eg. receptors that sense blood pressure in aorta)
Proprioreceptors
Receptors located near a moving part of the body interpreting positions of tissues as they move (eg. receptors in muscles)
Ways that receptors can transduce stimuli into changes in membrane potential (3)
- Some stimuli are ions and macromolecules affecting transmembrane proteins as they diffuse across membrane
- Some stimuli are physical variations in the environment affecting receptor cell membrane potentials
- Some stimuli are composed of electromagnetic radiation from visible light
Chemoreceptors
Receptors that detect chemical stimuli that arise from external environment (taste, smell, pain, solute concentration)
Mechanoreceptors
Interpret physical stimuli (pressure, vibration, sound, body position)
Thermoreceptors
Specialized class of mechanoreceptors that are sensitive to temperature changes
Photoreceptors
Detect light
General sense
Sensation of touch, pain, balance, and sensations from internal organs that are felt throughout the body
Special sense
Sense that has a specific organ devoted to it (eye, inner ear, tongue, nose)
5 major submodalities of sensory:
- Chemical senses are taste and smell
- Touch is a general sense and includes chemical sensation of pain
- Pressure, vibration, muscle stretching and movement of hair sensed by mechanoreceptors
- Hearing and balance use mechanoreceptors
- Vision uses photoreceptors
Free nerve endings stimuli
Pain, temperature, mechanical deformation
Mechanoreceptors stimuli
Low frequency vibration (5-15 Hz)
Bulbous corpuscle stimuli
Stretch
Tactile corpuscle stimuli
Light touch, vibrations below 50 Hz
Lamellated corpuscle stimuli
Pacinian corpuscle
Hair follicle plexus stimuli
Movement of hair
Muscle spindle stimuli
Muscle contraction and stretch
Tendon stretch organ stimuli
Stretch of tendons
Gustation
Special sense associated with tongue. Surface of tongue lined by stratified squamous epithelium
Papillae
Raised bumps on tongue that contain structures for gustatory transduction. Contains taste buds that have gustatory receptor cells sensitive to chemicals within food
What are gustatory receptor cells activated by
Taste molecules through the release of NT to dendrites of sensory neurons (facial, glossopharyngeal, vague nerves)
Pre-8os taste (gustation)
Sweet, salty, sour, bitter
8os taste (gustation)
Very savory
Facial nerves
Connects to the anterior 1/3 of tongue
Glossopharyngeal nerve
Connects to posterior 2/3 of the tongue and pharynx
Vagus nerve
Connects with taste buds in extreme posterior of tongue and pharynx
Pathway of gustation (2):
- Sensory neurons carry information to medulla (reflexes contribute to digestion by increasing secretion of saliva and gastric juices) then thalamus
- Neurons project to the cerebrum where taste is perceived
Limbic system and hypothalamus function regarding gustation
Involved in emotional responses elicited by food
Where are olfactory receptor neurons located
In small region of the walls of superior nasal cavity; olfactory epithelium - and contains bipolar sensory neurons
Olfactory receptor neuron structure
Each neuron has dendrites that extend from apical surface of epithelium into mucus lining the cavity
Pathway olfactory receptor neuron (3):
- Molecules are inhaled and pass over the olfactory epithelial region and dissolve into mucus
- Molecules bind to proteins that help transport them to olfactory dendrites
- Odorant-protein complex binds to a receptor protein within cell membrane of olfactory neuron dendrite and produce action potential
Olfactory sensory neuron structure
Axons extends through opening in skull and into brain. Group of axon called olfactory tract connect to olfactory bulb on ventral surface of frontal lobe
Pathway of olfactory sensory neuron
Olfactory tract connect to olfactory bulb and some travel to temporal lobe of cerebral cortex
How can smell be a potent trigger of memories and emotion
Some axons of olfactory sensory neuron project to limbic system and hypothalamus where smell becomes associated with long-term memory and responses
Audition
Transmission of sound waves into neural signal
External ear
Collects and focuses sound waves
Middle ear
Amplifies and transmits sound waves from outer ear to inner ear
Inner ear
Transduces sound waves into neuronal signal
External ear components (3)
- Auricle
- Auditory canal
- Tympanic membrane
Auricle
Large, fleshy structure on each lateral aspect of the head functioning in directing sounds towards auditory canal which enters skull
Tympanic membrane
Eardrum at the end of the canal and vibrates when struck by sound waves
What part of the ear is responsible for directing sound waves towards inner ear
Outer and middle ear
Conductive deafness
Interference with directing sound waves towards inner ear
Middle ear component
Auditory ossicles
3 auditory ossicles:
- Malleus
- Incus
- Stapes
Malleus:
Attached to tympanic membrane and articulates with incus