Sensory Receptors

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

5. neurotransmitter released, which sends us to the next level of processing

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 impulse

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 regeneration tube

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