unit 6 senses Flashcards
somatic senses (conscious or unconscious, function)
aka general senses, conscious, associated with receptors in skin (touch , temp, pain, itch, proprioception- position of body)
special senses (conscious or unconscious, function)
conscious, vision, hearing, taste, smell, equilibrium
somatic stimuli (conscious or unconscious, function)
unconscious (sensations not in cerebral cortex), muscle length and tension, proprioception
visceral stimuli (conscious or unconscious, function)
unconscious (sensations not in cerebral cortex), blood pressure, lung inflation, ph of plasma, etc (things going on inside)
which senses provide us information about external body and ourselves
somatic (senses), visceral, and special senses
specific form of stimulus
sensory modality
receptor acts on the
transducer
what can stimulus do to gated ion channels
cause them to open or close (depends on receptor type or modality), and this can cause depolarization/hyperpolarization
adequate stimulus
modality or form of energy to which the receptor is most responsive (Receptors can sometimes respond to other modalities but only if the stimulus strength has a high enough intensity. ex: temp receptors with chemical receptors pf hot sauce causing you to feel heat)
types of adequate stimulus:
Mechanoreceptors, Thermoreceptors, Chemoreceptors
- detect physical forces/stimuli (touch, pressure, stretch, vibrations,
gravity, soundwaves, etc.) Includes baroreceptors (detect pressure/stretch in blood
vessels, lungs, etc. - detect hot and cold temperatures.
- detect chemicals – e.g. olfactory neurons;
types of adequate stimulus: Photoreceptors, Nociceptors, Proprioceptors
- detect light. Includes the rods and cones (transducer cells) in the retina
of the eye. - detect pain
- detect body position and movement.
adaptation of receptors: tonic receptors
slowly adapting receptors
fire rapidly upon stimulus, then decrease firing rate but maintaining firing rate under a constant stimuli
adaptation of receptors: phasic receptors
rapidly adapting receptors. Fire at onset of stimulus, then stop if stimulus intensity remains constant
(adaptation).
They do not fire again until there is a change in the
intensity of the stimulus.
graded potential produced on the receptor cell is called a________ triggered by _____
receptor potential, adequate stimulus (aka prefered stimulus of receptor cell type
Primary (first order) sensory neurons
- unipolar neurons
- first neuron in the pathway
are the receptor in which transduction occurs (in the dendrites) OR they are the unipolar
neurons that receive the transduced signal from the non-neuronal receptor cell
Secondary (second order) sensory neurons
Multipolar neurons
Cell bodies in dorsal horn of spinal cord or in medulla depending on the sense involved
Tertiary (third order) sensory neurons
Multipolar neurons
Cell bodies in thalamus with axons relaying to cortex.
Receptive field
physical area in which
the presence of a stimulus will activate the receptor and alter the firing of a sensory neuron
receptive field
often associated with cutaneous (skin) receptors and the retina
what allows spatial summation of signals on the secondary neurons
Primary sensory neurons converging onto secondary neurons
Sensory Acuity (and when is it low/high)
how accurately a stimulus can be
located.
The more convergence of primary sensory neurons onto secondary sensory neurons, the
larger the receptive field and the lower the sensory acuity
less convergence the receptive
fields associated with each individual primary sensory neuron do not overlap, so easier to locate
Each part of the body can be mapped
to a specific area of the primary somatosensory cortex
These maps were developed by electrically stimulating the different regions of the cortex in people undergoing brain surgery
Areas of the body that appear larger on the map, have
greater acuity/sensitivity (less
convergence, opposite (etc)
sensation vs perception (and examples)
Sensation occurs when sensory information is detected by receptors in the peripheral nervous system.
ex: auditory receptors detect a loud, high pitched ringing noise
Perception occurs in the brain and involves awareness, organization and interpretation (assigning of meaning) of the sensation.
ex: the high pitched ringing noise is a fire alarm and you need to gather your things and leave the building
Sensory information travels
- From spinal cord to brain via ascending (sensory) pathways comprised of primary, and secondary neurons and in many cases tertiary neurons.
- Directly to brainstem via cranial nerves (exception – pathway for olfaction – olfactory nerves)
The four main properties of a stimulus are:
modality: interpretation of the type of stimulus. E.g. Touch, temperature, pain, sound, light, taste etc.
location: interpretation of where on the body the stimulus occurred
intensity: interpretation of strength of stimulus (e.g. how to tell if a feather has dropped on your foot vs. a brick).
duration (interpretation of how long the stimulus is applied/present)
Modality encoded by:
Labelled line coding
it is the pathway that
determines the modality, not the receptor (turning on kitchen light wont turn on bedroom light)
Location encoded by
Determined by which receptive fields are activated
Labeled line coding ensures that when a particular
receptive field is simulated, the pathway of neurons
to the brain will connect to the specific region of the
brain associated with the area stimulated
Intensity Encoded by
The number of receptors activated (population coding
And The frequency of action potentials reaching the brain
A feather touching the bottom of your foot
may only activate a few touch receptors. A brick falling
on your foot, would activate, touch, pressure, and
possibly pain receptors. With more receptors activated,
there would be an increase in the frequency.
of APs reaching the brain
Duration encoded by
duration of action potentials
in neurons.
The longer a stimulus is present, the longer action potentials will continue to be sent to the brain
Pathways to cortex have
primary, secondary and tertiary neurons.
Secondary neurons
decussate – cross over to the
opposite side of body in either the
spinal cord - for nociception, temperature and coarse touch
medulla - for fine touch, proprioception and vibration
All secondary neurons connect with
tertiary neurons in the thalamus
Sensations are perceived in the
primary somatosensory cortex
