What is a sensory receptor?
1. neural structures that respond to stimuli
2. it takes energy and converts it to an action potential
3. receptor responds to this energy by creating a graded potential
What is a stimulus?
a form of energy; a stress or change
Sensory receptors can lead to, but do not provide themselves with what two things?
1. sensation
2. perception
Can sensory receptors be stimulated?
yes, but it's the brain that actually gives us these sensations
How are sensory receptors classified?
1. type of stimuli they detect
2. location
3. structure complexity
What are 5 types of receptors that are based on their stimulus?
1. mechanoreceptor
2. thermoreceptor
3. photoreceptor
4. nociceptor
5. chemoreceptors
List what the following receptor responds to and give an example.
Mechanoreceptor
responds to: mechanics force
example: touch, vibration, stretch, pressure, itch
List what the following receptor responds to and give an example.
Thermoreceptor
responds to: heat energy
example: feeling changes in temperature
List what the following receptor responds to and give an example.
Photoreceptor
responds to: light energy
example: sun
List what the following receptor responds to and give an example.
Nociceptor
responds to: pain
example: sensing danger
List what the following receptor responds to and give an example.
Chemoreceptors
responds to: chemical energy
example: pH
Any class of receptor can become a ------ if overstimulated.
pain receptor
What are 3 types of receptors that are based on their location?
1. exteroceptors
2. interoceptors
3. proprioceptors
Where is the following receptor located?
Exteroceptor
at or on the surface of the body
Where is the following receptor located?
Interoceptor
in the body
Where is the following receptor located?
Proprioceptors
muscles, joints, tendons, ligaments, connective tissue
What are 2 types of receptors that are classified based on their structural complexity?
1. simple receptors
2. complex receptors
Which are most common, simple receptors or complex receptors?
simple receptors
What is the definition of a simple receptor?
modified dendritic ending on sensory neurons
What is the definition of a complex receptor?
localized collections of cells associated with special senses
General sensory receptors mostly include sensory receptors, which are related to...
vibration, touch, pain, etc.
What are free nerve endings?
dendrites of a sensory nerve
What are 3 types of free nerve endings?
1. merkel discs
2. hair follicle receptors
3. itch receptors
List what the following free nerve ending responds to and where it is located.
Merkel discs
responds to: light touch
location: epidermis
List what the following free nerve ending responds to and where it is located.
Hair follicle receptors
responds to: temperature change and light touch
location: root hair plexus
List what the following free nerve ending responds to and where it is located.
Itch receptors
responds to: something getting into the pores; comes from something chemical like poison ivy
location: pores
What are encapsulated dendritic endings?
dendrites surrounded by connective tissue covering
What are 6 types of encapsulated dendritic endings?
1. meissner's corpuscles
2. pacinian corpuscles
3. ruffian's corpuscles
4. muscle spindles
5. golgi tendon organs
6. joint kinesthetic receptors
List what the following encapsulated dendritic ending responds to and where it is located.
Meissner's corpuscles
responds to: light touch
location: dermis
List what the following encapsulated dendritic ending responds to and where it is located.
Pacinian corpuscles
responds to: deep pressure
location: deep dermis
List what the following encapsulated dendritic ending responds to and where it is located.
Ruffini's corpuscles
responds to: stretch or pressure
location: connective tissue
List what the following encapsulated dendritic ending responds to and where it is located.
Muscle spindles
responds to: stretch
location: muscle
List what the following encapsulated dendritic ending responds to and where it is located.
Golgi tendon organs
responds to: stretch in tendons
location: tendons
List what the following encapsulated dendritic ending responds to and where it is located.
Joint kinesthetic receptors
responds to: stretch on articular capsule
location: articular capsule of synovial membrane
Which 3 encapsulated dendritic endings could be classified as synovial receptors?
1. muscle spindles
2. golgi tendon organs
3. joint kinesthetic receptors
The somatosensory system is part of the sensory system that serves the ------- and the -------.
1. body wall
2. limbs
The somatosensory system requires ------- at 3 levels.
neural integration
What 3 levels does the somatosensory system require neural integration at?
1. receptor (sensory) level
2. circuit level
3. perceptual level
Which level of the somatosensory system is being described below?
A sensory receptor which detects the stimulus and turns it into an nervous impulse
receptor (sensory) level
Which level of the somatosensory system is being described below?
Sent toward the CNS (ascending pathway)
circuit level
Which level of the somatosensory system is being described below?
Function of the cerebral cortex (ascending pathway)
Example: brain know you are sitting in a chair because you have sat in a chair before
perceptual level
What are the 5 components of receptor level processing?
1. receptor must be receptive to the stimulus
2. the stimulus must be applied within the receptive field
3. stimulus has to be transuded into a receptor potential
4. if the stimulus is strong enough (at or above threshold), an action potential is produced
Within the receptor level processing, a receptor must be receptive to the stimulus - what does this mean?
1. the right type of stimulus must be applied to the receptor
-example: touch receptors detect touch
2. this is specific - each stimulus / receptor is specific to a particular type of receptor / energy and they won't respond to the wrong type
Within the receptor level processing, the stimulus has to be transducer into a receptor potential - what does this mean?
1. transduction is the conversion of one form of energy to another
2. stimulus energy is converted or leads to graded potential
What are the 2 types of receptors involved in receptor level processing?
1. tonic
2. phasic
List for the following receptor its usual state, its adaptation rate, and an example.
Tonic
usual state: on
adaptation rate: slowly
example: equilibrium receptor (balance)
List for the following receptor its usual state, its adaptation rate, and an example.
Phasic
usual state: off
adaptation rate: quickly
example: eating spicy food or an ant crawling up your leg
What is adaptation?
1. an area of receptor level processing
2. reduction in sensitivity in the presence of a constant stimulus
What types of receptors do not adapt?
proprioceptor and pain receptors / nociceptors
What is the most important component of circuit level processing?
ascending pathways carry impulses to appropriate regions of the cerebral cortex
Within the circuit level processing, first-order neurons carry signals to what?
the spinal cord
Within the circuit level processing, where does the synapse with the second-order neuron occur?
in the posterior horn of the spinal cord; or in the medulla oblongata
Within the circuit level processing, where does the synapse with the second-order neuron occur if it is a part of the spinal reflex?
it synapses directly with a motor neuron
Within the circuit level of processing, where does the second-order neuron carry the impulse?
to the thalamus or the cerebellum
Within the circuit level of processing, when the synapse with the third-order neuron occurs, where is the impulse carried to?
the somatosensory cortex of the cerebrum
Circuit level processing leads us into...
perceptual level processing
What are the 2 main components of perceptual level processing?
1. message to the cortex is always in the form of an action potential
-it doesn't matter how the receptor was stimulated, it always sends the same signal
2. sensation is determined based on what part of the cerebral cortex receives the action potential im
What is projection?
stimulation of the same area of the body always sends to the same area of the cerebral cortex
What are the 6 aspects of sensory perception?
1. perceptual detection
2. magnitude estimation
3. spatial discrimination
4. feature abstraction
5. quality discrimination
6. pattern recognition
Which aspect of sensory perception is being described below?
Knowing we've been stimulated
perceptual detection
Which aspect of sensory perception is being described below?
Knowing the difference between a weak stimulus and a strong stimulus and a loud volume versus a quiet volume
magnitude estimation
Which aspect of sensory perception is being described below?
Knowing where exactly we've been stimulated
spatial discrimination
Which aspect of sensory perception is being described below?
Ability to differentiate the differences between materials
feature abstraction
Which aspect of sensory perception is being described below?
Ability to differentiate between sub-modalities
quality discrimination
Which aspect of sensory perception is being described below?
Detecting a pattern in a stimulus
Familiar or significant stimuli
pattern recognition
Are nerves and neurons the same thing?
NO, they are different
Neurons or nerves?
Tissues
neurons
Neurons or nerves?
Cord-like organs of the peripheral nervous system (PNS)
nerves
Nerves are composed of what 5 things?
1. neural tissue (small portion)
2. myelin (adipose tissue)
3. connective tissue wrappers
4. blood vessels
5. lymphatic vessels
Nerves are individual ---- collectively wrapped together. Then those get wrapped together again.
axons
Nerves are parallel bundles of...
peripheral neurons enclosed by successive wrappings of connective tissue
What are the 3 layers of a nerve?
1. epineurium
2. perineurium
3. endoneurium
What is the epineurium of a nerve?
dense irregular connective tissue
surrounds all fasciculi
What is the perineurium of a nerve?
dense irregular connective tissue
surrounds an individual fascicle
What is the endoneurium of a nerve?
reticular connective tissue
surrounds each individual axon
What are the 3 classifications of nerves?
1. sensory (afferent) nerves
2. motor (efferent) nerves
3. mixed nerves
Which classification of nerves is being described below?
Going toward the CNS
Composed of all sensory neurons
sensory (afferent) nerves
Which classification of nerves is being described below?
Going away from the CNS
Composed of all motor neurons
motor (efferent) nerves
Which classification of nerves is being described below?
Part sensory and part motor
Can also be somatic and autonomic
Some neurons going toward the CNS and some are going away from the CNS
The majority of the nerves in our body are these
mixed nerves
What are ganglia?
collection of cell bodies of neurons that are associated with a peripheral nerve
The dorsal root ganglia contains the cell bodies of ----- neurons.
sensory
What are peripheral nerves?
nerves that branch off of the brain (cranial nerves) or the spinal cord (spinal nerves)
not part of the CNS
connects the CNS to the rest of the body
Nerve regeneration is limited to...
damage of areas other than the cell body
What happens if the cell body of a nerve is damaged?
then the nerve cannot regenerate, it is simply dead
Do successive neurons within a neural chain survive during nerve regeneration?
NO
What are the 5 steps to nerve regeneration?
1. peripheral axon is injured
2. separated ends seal and swell
3. Wallerian degneration occurs
4. surviving Schwann cells migrate and go to the injury site
5. Schwann cells release growth factors and CAMS (cell-surface adhesion molecules) and form a regen
The first step of nerve regeneration is, peripheral axon is injured - describe this step.
1. far away from the cell body
2. the farther away from the cell body, the higher the likelihood of regeneration
3. if we injure a CNS axon, it typically will not regenerate
The second step of nerve regeneration is, separated ends seal and swell - how do they do this?
they spread distally; meaning, away from the body
List the 3 components of Wallerian degeneration.
1. axon and the axon sheath degenerate due to the lack of nutrient
2. once it degenerates, phagocytes degrade the damaged portion
3. the neurolemma and endoneurium are left in tact
Growth factors and CAMS cause the axon to...
grow
The axon grows at about ---- mm per day.
1.5