BIO 3200 Ch. 10 Review

What are the special senses?

vision, hearing, taste, smell, equilibrium

What are the somatic senses?

touch, temperature, pain, itch, proprioception

what does a sensory receptor act as?

a transducer

what is the difference between a simple sensory system and a complex sensory system?

simple - single sensory neuron; complex - multicellular sense organs

properties of neural receptors

* naked (“free”) nerves
* complex neural receptors encased in connective tissue capsules
* may be myelinated or unmyelinated

general properties of sensory systems

* stimulus as physical energy → sensory receptor
* intracellular signal → usually change in membrane potential
* stimulus → threshold → action potential to CNS
* integration in CNS → cerebral cortex or acted on subconsciously

what are nonneural receptors?

highly specialized cells associated with sensory neurons

what are the 4 major groups of receptors?

* chemoreceptors
* mechanoreceptors
* thermoreceptors
* photoreceptors

how do chemoreceptors work? what senses are they associated with?

respond to chemical ligands: taste, smell

how do mechanoreceptors work? what senses are they associated with?

respond to mechanical energy pressure and sound: hearing

how do thermoreceptors work? what senses are they associated with?

respond to temperature

how do photoreceptors work? what senses are they associated with?

respond to light: vision

what are receptive fields in sensory neurons?

the physical area where a stimuli activates a neuron

what may neighboring receptive fields exhibit?

convergence

what does the size of the receptive field determine?

sensitivity

Sensitive areas have ___ receptive fields while less sensitive areas have ___ receptive fields.

smaller; larger

how does sensory information travel from the spinal cord to the brain?

ascending pathways, directly to brain stem by cranial nerves

where are visceral reflexes integrated and why are they special?

integrated in brain stem or spinal cord; they usually do not reach conscious perception

perceptual threshold definition

level of stimulus necessary to be aware of particular sensation

habituation definition

decreased perception through inhibitory modulation, falls below perceptual threshold

sensory modality definition and example

* which sensory neurons are activated and where neurons terminate in brain
* labeled line coding

labeled line coding definition

1:1 association of receptor with sensation

how is location of the stimulus determined?

* based on which receptor fields are activated
* lateral inhibition (needles on skin) and population coding

how is intensity of the stimulus determined?

number of receptors activated and frequency coding

how is duration of the stimulus determined

duration of action potentials & how receptors adapt

what are the two types of receptors involved with coding and processing distinguish stimulus properties?

tonic receptors and phasic receptors

what are tonic receptors and how do they work?

slowly adapting receptors that fire rapidly when first activated, then slow and maintain their firing as long as the stimulus is present

what are phasic receptors and how do they work?

rapidly adapting receptors that fire when they first receive a stimulus but cease firing if the strength of the stimulus remains constant

where are the receptors for touch, proprioception, temperature, and nociception located? what are the three types of neurons involved?

in the skin and viscera; primary, secondary, and tertiary

primary sensory neurons

synapse in CNS with secondary sensory neurons

secondary sensory neurons

interneurons in the CNS, synapse with tertiary sensory neurons in the thalamus

tertiary sensory neurons

project to somatosensory cortex and many project to cerebellum somatosensory cortex

Touch receptors are the most common receptors in the body and respond to many different stimuli. What are the different types of physical contact that can stimulate these receptors?

* stretch
* steady pressure
* fluttering or stroking movements
* vibrations
* texture

what are skin temperature receptors and what are the types?

* free nerve endings that terminate in subcutaneous layers
* cold receptors and warm receptors

when are pain receptors activated in terms of temperature?

above 45°C

what are nociceptors? what do they respond to? where are they found?

* neurons with free nerve endings
* respond to strong noxious stimulus that may damage tissue
* found in the skin, joints. muscles, bones, and viscera (not in the CNS)

how are nociceptors activated?

* activation is a reflexive protective response
* integrated in spinal cord
* ascending pathways to cortex become conscious sensation

what is the withdrawal reflex?

protective reflective response to pain

what is ischemia?

lack of adequate blood flow, protects muscle from damage

what is referred pain?

poorly localized pain perceptions from visceral and somatic pain pathways converging on a single ascending tract

what is gate control theory in pain modulation?

AB fibers synapse on inhibitory neurons and increase inhibition

* integrated response from AB and C fibers decrease the perception of pain

what are the two types of senses that chemoreception refers to?

smell (olfaction) and tase (gustation)

what is the olfactory bulb?

an extension of the forebrain

True or False: Olfaction is one of the youngest senses and allows us to discriminate among millions of different odors.

False (it is one of the OLDEST senses)

what do olfactory pathways involve?

* olfactory sensory neurons
* ascending pathways to amygdala and hypothalamus

what is the olfactory epithelium embedded with?

olfactory sensory neurons (primary sensory neurons)

what is happening to stem cells in the olfactory epithelium?

they are consistently dividing into new neurons

what are the steps in olfactory signal transduction?

* odorants bind to odorant receptors
* G protein - linked membrane receptors
* Neurons project from bulb to form olfactory tract

what is gustation?

the sense of taste

which sense is gustation closely linked to?

olfaction

what are the five basic sensations of gustation?

sweet, bitter, umani, sour, salt

what are the nontraditional taste sensations?

specific hunger and salt appetite

what parts make up the “external ear”?

pinna → ear canal → tympanic membrane

what parts make up the middle ear?

malleus → incus → stapes & eustachian tube

what parts in the inner ear are used for equilibrium?

vestibular apparatus and semicircular canals

what parts of the inner ear are used for hearing?

cochlea with oval window and round window

define hearing

our perception of energy carried by sound waves

sound definition

the brain’s interpretation of the sound waves that reach the ear

what is frequency translated into? what is it measured in?

pitch; Hz

what is intensity of sound translated into? what is it measured in?

loudness, dB (decibels)

what are sensory (receptor) cells in our ears?

hair cells in the cochlea

what are the three parallel, fluid-filled channels in the cochlea?

* vestibular duct
* cochlear duct
* tympanic duct

where are the vestibular and tympanic ducts in the cochlea and what are they filled with?

continuous with each other, divided by the helicotrema; perilymph (similar to plasma)

where is the cochlear duct in the cochlea and what is it filled with?

dead-end tube between vestibular and tympanic duct; filled with endolymph (similar to ICF)

what organ does the cochlear duct contain? what does the organ sit on and what is it covered by?

the corti, which is made up of hair cell receptors and support cells; sits on basilar membrane; partially covered by tectorial membrane, which bends stereocilia on non-neural hair cells

where are sounds first processed? what it being transformed?

the cochlea; the cochlea transforms sound waves into electrical signals

where is the coding for pitch and loudness in the cochlea?

* pitch: basilar membrane
* loudness: number of action potentials produced

where are auditory pathways projected?

to the auditory cortex

which two types of neurons are in the auditory cortex?

* primary auditory neurons which project to brain in medulla oblongata
* secondary sensory neurons which project to nuclei
* synapse in nuclei in midbrain and thalamus before projecting into auditory cortex

what does the localization of a sound source require?

simultaneous output from both ears

hearing loss may result from …

mechanical or neural damage

conductive hearing loss

no transmission through either external or middle ear

central hearing loss

damage to neural pathway between ear and cerebral cortex or damage to cortex itself

sensorineural hearing loss

damage to structures of inner ear

equilibrium definition

a state of balance

what is the function of vestibular apparatus

provides information about movement and position

what does the vestibular apparatus consist of?

1. series of interconnected fluid-filled chambers
2. otolith organs; saccule and utricle
3. semicircular canals
4. filled with endolymph

what do the otolith organs do?

sense linear acceleration and head position

* maculae consist of our hair cells, otolith membrane, calcium carbonate, otoliths

what do semicircular canals do?

ampulla contains crista made up of hair cells and cupula

where do equilibrium pathways project primarily to?

cerebellum

vision definition

light reflected from objects in the environment are translated into a mental image

1st of 3 steps of vision

light enters the eye, and the lens focuses the light on the retina

2nd of 3 steps of vision

photoreceptors of the retina transduce light energy into an electrical signal

3rd of 3 steps of vision

neural pathways from retina to brain process electrical signals into visual images

where does light enter in the eye?

through the cornea

where are the two places light is modified?

* __pupil__ modulates quantity of light and depth of field
* focused on retina by changes in the __lens__

light is directed to…

the retina

in the eye, neural pathways process electrical signals into …?

visual images

what is the location where neurons join into the optic nerve?

optic disk

where do optic nerves cross over?

in the optic chiasm

neurons synapse in lateral geniculate body in the …?

thalamus

optic tracts at the …?

visual cortex in the occipital lobe

where does the lens focus light on?

the retina

focal point

point where light rays converse

focal length

distance from the center of the lens to the focal point

light entering eye is ___ , or bent at the *_* and *_*

refracted, cornea, lens

what modifies the lens so that the focal point lands on the retina?

ciliary muscles

accomodation

the process of eye adjusting lens shape to keep objects in focus

near point accomodation

the closest distance at which the lens can focus an object

myopia

focal point falls in front of the retina (near-sightedness)