Human A&p Sensory Physiology

Front 1

Purpose of the afferent division of the PNS?

Back 1

Sends information about internal and external environment to CNS

Front 2

Types of afferent sensory input(broad categories)

Back 2

1.) Visceral Afferent = afferent input that doesn't reach level of conscious awareness
2.) Somatic Afferent and special senses= afferent input that reaches level of conscious awareness.

Front 3

What does the somatic nervous system control

Back 3

Skeletal Muscle indicating more deliberate movements

Front 4

What does the Autonomic nervous system control

Back 4

Smooth muscles, cardiac muscles, and glands. Those things that can be controlled without our conscious knowledge

Front 5

Where are the three main places receptor information passes through before getting to the thalamus.

Back 5

1.) Spinal cord = somatic "skin" sensation.
2.) Brain Stem = info from tongue and ear
3.) Thalamus = all previous information plus info from eye and nose.
4.) All the info must pass through thalamus before getting CNS (cortex)

Front 6

How is used to change one for of energy into another that is recognized by CNS (like light energy turning to chemical energy)

Back 6

Transduction occurs by the transducers. They allow the body to respond to change in the environment even if it doesn't understand the original stimulus.

Front 7

Modalities

Back 7

A variety of energy forms in which a stimuli can exist.
Examples: Chemical, mechanical ect...
-adequate stimulus
"All receptors can respond to all types of energy (if stimulus is strong enough)"

Front 8

Specific Receptors

Back 8

receptors specialized to respond to one particular type of energy at much lower threshold that other receptors respond to this form of energy.

Front 9

Adequate Stimulus

Back 9

particular form of energy to which a receptor is the most sensitive
- it IS possible to respond to other types of stimulus if the intensity is high enough.
- Example: seeing starts induced by force to eye... eye not used to touch

Front 10

What is a sensory receptor

Back 10

specialized ending of afferent neuron.
Separate cell closely associated with peripheral ending of an afferent neuron.

Front 11

How does information get from sensory receptor to CNS
-general path taken of somatosensory pathway
-what is it responsible for?

Back 11

1.) Sensory receptor
2.) primary sensory neuron: Spinal cord to midbrain
2.) secondary sensory neuron:
Midbrain to thalamus
3.) tertiary secondary neuron.
thalamus to cortex

Above path is somatosensory pathway responsible for conveying conscious somatic sensations.

Front 12

Where does information from a sensory receptor from right hand cross over to stimulate the left brain

Back 12

?????
- midbrain
- thalamus
- corpus callosum

Front 13

What are the general processing patterns or levels of the CNS

Back 13

- spinal cord
- brainstem
- diiencephalon: thalamus (everything passes through and then is relayed to appropriate part of cortex)
- cerebral hemispheres: cortex which has.

Front 14

Three main responsibilities of the cortex when receiving somatosensory info.

Back 14

- conscious perception
- integration
- initiation of voluntary movement

Front 15

Why have a afferent input?

Back 15

- controls and determines efferent output
- lead to cortical arousal, consciousness
- gives us a perception of our world
- can be used in the future.

Front 16

Sensory receptors are part of the _____________ system and respond to _____________

Back 16

- peripheral
- stimuli

Front 17

What different classifications are used to categorize sensory receptors.

Back 17

- location
- type of stimuli
- structural complexity

Front 18

teloceptors

Back 18

sensitive to events at a distance (think telopathic)

Front 19

exteroceptors:

Back 19

sensitive to stimuli arising outside the body, but near at hand
- located near body surface
- light receptors (cones and rods) are examples

Front 20

interoceptors:

Back 20

Respond to stimuli arising from within the body
- monitor a variety of stimuli such as chemical changes, temperature; usually we are unaware of their function.
- blood vessels monitor body processes

Front 21

Proprioceptors:

Back 21

respond to internal stimuli
- location much more restricted,
- constantly advise the brain of body movements
- sending the cerebellum messages (i think)

Front 22

Mechanoreceptors:

Back 22

generate nerve impulses when they are deformed by mechanical forces

Front 23

Thermorecptors

Back 23

sensation of temperature changes

Front 24

Osmoreceptors

Back 24

detect changes in concentration of solutes in body fluids

Front 25

Photoreceptors

Back 25

respond to light energy

Front 26

Chemorectors

Back 26

respond to chemicals in solutions (smell and taste)

Front 27

Nociceptors

Back 27

respond to potentially damaging stimuli that results in pain
- extreme temperature
- mechanical damage
- chemicals released by damage cells

Front 28

What are the two divisions of complexity of a sensory receptor

Back 28

- simple receptors
- complex receptors

Front 29

General definition of simple sensory receptors

Back 29

Modified dendritic endings of sensory neurons. Modified and unmodified exist.

Front 30

Unmodified simple sensory receptors

Back 30

Free dendritic ending: found in all body tissues, especially in the epithelium and connective tissue.
- located between cells
- root hair plexus - free endings surrounded by hair follicles making sensitive to light touch.
- could also be sensitive to heat pressure

Front 31

Two types of modified simple sensory receptor endings.

Back 31

- expanded endings
- encapsulated dendritic endings

Front 32

Expanded endings of simple receptors: modified dendritic ending of sensory neurons.

Back 32

- distal ending have knoblike swelling
- if the free ending is associated with a disk shape cell - MERKLE DISK -
- light touch is all that is needed
- deep epidermis

Front 33

Encapsulated dendritic ending of simple receptors: modified dendritic ending of sensory neurons.

Back 33

- one or more terminal fibers of sensory neurons enclosed in connective tissue capsule
- almost all are mechanoreceptors (Pacinian corpuscles, Ruffini corpuscle)

Front 34

Examples of: Encapsulated dendritic ending of simple receptors: modified dendritic ending of sensory neurons.

Back 34

- propriorecptors include muscle spindles
- Golgi tendon organs
- joint kinesthetic receptors.

Front 35

Simple structural overview of Pacinian corpuscle of Encapsulated dendritic ending of simple receptors: modified dendritic ending of sensory neurons.

Back 35

It's a single dendrite surrounded by connective tissue with fluid inside

Front 36

What classifies of complex receptor

Back 36

- sense organs
- cells work together to accomplish a specific receptive process
- associated with special senses
- example: with hear there is sensory hair that is responsible for picking up the info and sending out synaptic vesicles.

Front 37

With receptor cell what does the intensity depend on

Back 37

It depends on the type of graded potential and how large it is, which leads to the opening of Na/K channel. The amount of Na+ (the depolarization) that enters will dictate the the frequency at which the signal enter and determine how much of a stimulus we feel.

Front 38

What's the difference between mechano and chemical receptors.

Back 38

The only real difference is the type of channels that will open after the stimuli. As long as the stimulus is strong enough to hit the trigger zone with enough power and trigger the voltage gated channels AP will occur

Front 39

Where is the trigger zone located in relation to the rest of the components of a nerve ending

Back 39

It is located right after the first node of ranvier which is down a little bit from the actual receptor.

Front 40

A stimulus will cause a change in membrane permeablilty of specilized receptors cell. What will all occur when this happens

Back 40

-results in local graded potential, a receptor potential
- one type of channel opens tht allows ion fluxes (usually Na+ or Na/K)
- produces modulated neurotransmitter release which will affect the function of the secondary sensory neuron.

Front 41

What is a receptor potential

Back 41

a local graded potential of a receptor cell

Front 42

What determines the modulation of NT release which is passed on to following cell.

Back 42

The amplitude of depolarization.
Frequency is also an issue

Front 43

Why is receptor potentials different from graded potentials?

Back 43

- location :)
- it is also different because it is linked to the magnitude of depolarization. More Na that enters = more deporlarization = more modulation of NT.
- frequency also plays into determining the intensity.

Front 44

How do receptors which are separate cells work?

Back 44

The cells are not a nerve but they can respond to a stimulus by releasing NT just as any other nerve would.

Front 45

Why are taste cells so complex

Back 45

Their microvilli pick up different senses which is relayed to a cell, which is initially related to dendrites of afferent fibers.

Front 46

What would happen to a receptor cell if the node of ranvier was damaged.

Back 46

Action potential would never be able to stimulate the axon beyond that point.

Front 47

What is all determining the strength of a sensory stimulus?

Back 47

Stimulus strength is going to ultimately determine how strong a stimulus is because it will increase the generator potential which can lead to a greater frequency of firing and a high action potential

- look at corresponding graphs (15)

Front 48

Difference between generator potentials and receptor potentials.

Back 48

generator potentials are associated with afferent neurons. A graded potential will have to be great enough to stimulate the trigger zone for any activity.

receptor potentials are run through receptive cells which will be stimulated and then eventually release modulated NT. This NT will effect the secondary sensory neuron (from midbrain to thalamus.
Example is taste receptors

Front 49

Summary of generated and receptor potentials

Back 49

graded potentials: stronger the stimulus, the greater the permeability change, the larger the receptor/generator potential
Receptor: no refractory period, summation in response to rapidly successive stimuli is possible.

Front 50

Adaptation

Back 50

Stimuli of same intensity do not always elicit receptor potentials of the same magnitude from the same receptors.

Front 51

Two type so adaptation

Back 51

- Phasic receptors
- tonic receptors

Front 52

Phasic receptors

Back 52

if stimulus is applied at constant strength, AP generation stops - receptor stops responding. "phases out"
chart pg 17

Front 53

Tonic Receptors

Back 53

If stimulus is applied at constant strength, frequency of AP generation somewhat declines but receptors keep responding.
Chart pg 17

Front 54

What would the graph look like, over time, for a generator potential of a tonic receptor

Back 54

It would start of high and then drop lower but never stop firing until stimulus was removed.

Front 55

What would the graph look like, over time, for a generator potential of a phasic receptor.

Back 55

There would be an initial stimulus to the graded potential but to adapt to the constant stimulus they rapidly turn off and then one more (smaller)graded potential is seen when the stimulus is turned off.

Front 56

Summary of Tonic receptors

Back 56

- slow adapting
- continue to transmit impulses to CNS as long as stimulus is present
- important where maintained info. about a stimulus is valuable

Front 57

Examples of Tonic receptors (think of slight habituation)

Back 57

- muscle spindles
- proprioceptors
- receptors for cold/hot, pain
- receptors for lung inflation
- receptors for blood pressure.

Front 58

Summary of phasic receptors

Back 58

- fast adapting
- fire when receive first stimulus
- stop firing if stimulus remains constant with the exception of a small graded potential from off response
- useful in situations where important to signal a change in stimulus intensity rater than relay status quo info.

Front 59

Mechanism of phasic receptors after initial graded response.

Back 59

- opening channels that cause repolarization
- inactivation of opened Na+ channels
- accessory structures decrease amount of stimulus reaching receptors (for example... pacinian corpuscl less responsive because of fluid)

Front 60

Examples of phasic receptors

Back 60

- touch, pressure receptors
- "wearing clothes"

Front 61

What is happening to a pacinian corpuscl if it is a phasic receptor

Back 61

- deformation of layers which result in a shift in the fluid causing the first graded potential
- Continued consistent stimuli cause no further changes
- when stimulus is taken away the fluid shifts again causing the off response.

Front 62

Two examples of both tonic and phasic receptors (19)

Back 62

Tonic: pain receptors, proprioceptors

Phasic: Pressure receptors (no true for cat pressure receptors), light tough receptors.

Front 63

What attributes of different stimuli must be coded for to completely understand what just occurred.

Back 63

1.) Modality - each type of cell has own function so info from that receptor means something
2.) Location
3.) Intensity (tickle vs. punch)
4.) Duration (length

Front 64

Doctrine of specific nerve endings

Back 64

sensation invoked by impulses generated in receptor depends of specific part of brain they ultimately activate.

Front 65

Labeled line coding (another property of specificity of each sensory nerve)

Back 65

information from different receptors is kept separated within specific labeled lines between the periphery and the cortex.

-the sensory pathways are different from sense organs to cortex

-WE NEED TO KNOW WHERE EVERYTHING IS COMING FROM FOR OUT BRAIN TO MAKE SENSE OF IT.

Front 66

What leads to modality.

Back 66

Our brains association of signals from specific receptors with a specific modality (path taken)

Front 67

Example of Modality of sensory receptors.

Back 67

- stimulate a sensory fiber from Pacinian corpuscle = touch
- stimulate second-order neuron from Pacinian corpuscle = touch
- Simulate are of cortex that ultimately receives input from Pacinian corpuscle = touch

Essentially everything in the sensory tract of Pacinian corpuscle will lead to the sensation of touch even if first receptor was not stimulated.

Front 68

Reason for Phantom Limb.

Back 68

Because of label line coding, even when the receptive region for a neuron is no long there, stimulating the pathway somehow will lead to the illusion of touch.

Front 69

Law of projection

Back 69

no matter where a particular sensory pathway is stimulated along its course to cortex, conscious sensation produced is referred to the location of the receptor
- a particular sensory input is projected to a specific region of the cortex.

Front 70

Location sense receptors can differentiate touch that is very close. How is this possible.

Back 70

lateral inhibition. It helps to isolate the location by involving pre-synaptic inhibition.

Front 71

Proof of the specificity of location from certain sensory pathways.

Back 71

- stimulation of sensory fiber from receptor in hand - stimulus location - hand
- stimulation of secondary neuron in same pathway - stimulus location - hand
- stimulation of are in cortex that receives input from pathway -stimulus location - hand.

- Further explains phantom limb example in amputees.

Front 72

How does lateral inhibition work?

Back 72

It allows the sensory pathway the closes (most direct) to proceed to be stimulated without interference
- at the same time the central pathway sends out IPSP to it's neighbors and suppresses their activity leading to a more direct stimulus
- seen in retina

Front 73

How is the intensity and duration of sensory info coded for?

Back 73

It is coded for by the frequency of the AP's generated which is proportional to the intensity of stimulation.

Front 74

Why do we register feeling a harder touch

Back 74

Receptive fields.
Light touch activates a few
Harder touch activates more

Front 75

How do we translate the location and the strength of a touch?

Back 75

- Location is determined by the primary neurons that pick up info from a specific area
- Intensity is coded by the number of secondary neurons receptive fields which are activated
-The final sensation is a combination of the two.
- Usually a converging scheme.

Front 76

What's a good way to think about the intensity and receptive fields?

Back 76

Often, there are a lot of primary receptors and when these want to initiate a touch in one region the will converge on a secondary sensory neuron. If a stronger intensity is noted they will converge on multiple secondary sensory neurons.

Front 77

What does the system of having primary and secondary receptors allow for acuity?

Back 77

Because it allows our bodies to discriminate where it is being touched depending on the density of receptors.
- The size of the receptive field is inversely related to the receptor density.

Front 78

How are the acuity of sensory neurons and the sensitivity related but not the same

Back 78

Sensitivity is more closely related to how hard the stimulus is and how much response is seen. Number of receptors does matter
Acuity is related to the ability to use these receptors to discriminate or to amplify locations of touch.

Front 79

What are two things acuity is related to?

Back 79

1.) density of receptors and size of receptive field
-degree of convergence between primary and secondary sensory neurons.

Front 80

What is a high acuity region?

Back 80

High Acuity
-High receptor density
- "small" receptive field
- low convergence

Front 81

What is a low acuity region?

Back 81

Low Acuity
- low receptor density
- "Large" receptive field
- High convergence

Front 82

How does acuity relate to intensity?

Back 82

Convergence of primary sensory neurons allow simultaneous subthreshold stimuli to sum at the secondary sensory neuron and initiate an action potential

Front 83

How do cells differ in stimulus duration

Back 83

duration of perception of a stimulus has to do with whether adaptation is occurring or not.

Front 84

Summary of stimulus modality

Back 84

Distinguished by the type of receptor activated and the specific pathway over which this information is transmitted to a particular are of the cerebral cortex.

Front 85

Summary of location of stimulus

Back 85

Distinguished by the location of the activated receptive field and the pathway that s subsequently activated to transmit this information to the area of the somatosensory cortex representing that particular location

Front 86

Summary of stimulus strength

Back 86

Distinguished by tthe frequency of action potential initiated in an activated afferent neuron and the number or receptors activated.

Front 87

Why does pain exist

Back 87

- protective mechanism
- awareness that tissue damage is occurring
- storage of painful memories = avoid harmful events
- accompanied by behavioral responses

Front 88

Three types of pain receptors

Back 88

- mechanical nociceptors
-thermal nociceptors
- polymodal nociceptors

Front 89

Mechanical Nociceptors

Back 89

respond to mechanical damage

Front 90

Thermal nociceptors

Back 90

respond to temperature extremes

Front 91

Polymodal nociceptors

Back 91

respond equally to all kinds of damaging stimuli (including chemicals released from injured tissue)

Front 92

What are all nociceptors sensitized by?

Back 92

The presence of prostaglandins
- cycloxinagenase inhibitors interfer with the ability of prostagladins in tissues making them less sensitive.

Front 93

What does Bradykinin do?

Back 93

It increases the permeability of capillaries to chemicals.
-released by injured cells
- sets up inflamation

Front 94

How do fast pain pathways process

Back 94

1.) A- delta fibers
2.)Fast - 30 m/sec
3.) occurs on stimulation of mechanical and thermal nociceptors
-produces sharp, prickling sensation
- easily localized
- occurs first

Front 95

How do slow pain pathways proceed

Back 95

- C fibers
- slow - 12 m/sec
- Activated by chemicals-- bradykinin
- Activated by capsaicin
- harder to localize, dull/aching/burning sensation, lasts longer
-occurs on stimulation of polymodal nocicptors.

Front 96

What are pain processing neurotransmitter?

Back 96

- Substance P
- Glutamate - significance of LTP
- exaggerate sensitivity of injured area

Front 97

What do endogenous analgesics do.

Back 97

Opiates.
- allow for the knockout of pain.
- suppresses transmission of pain pathway as they enter SC
- If you use endogenous analgesics you don't even get to thalamus.