Topic 5 - Somatosensory System new

Question 1

What is somatosensation?

Answer 1

Somatosensation is the sensory information received from the skin and musculoskeletal system.

Question 1

What are the two major systems involved in somatosensation?

Answer 1

1) cutaneous system and
2) proprioceptive system

Question 2

What is the primary function of the cutaneous system in somatosensation?

Answer 2

Detection of mechanical stimuli.

Question 3

What is the primary function of the proprioceptive system in somatosensation?

Answer 3

The primary function of the proprioceptive system in somatosensation is the detection of pain and temperature.

Question 4

Five Types of Mechanoreceptors in the Skin +1 sensory receptor

Answer 4

Meissner’s corpuscles, Pacinian corpuscles, Merkel’s disks, Ruffini’s corpuscles + Free nerve endings

Question 5

Meissner’s Corpuscles: Location and Function

Answer 5

Location: Found in the superficial layers of the skin, particularly in the fingertips and lips (areas that dont have hair)
Detection: Sensitive to light touch, low-frequency vibrations, and changes in texture/pressure

Question 6

Pacinian Corpuscles:

Answer 6

Location: Located deeper in the skin.
Detection: Sensitive to deep pressure and high-frequency vibrations. They detect rapid changes in pressure or vibration

Question 7

Merkel Cells (Tactile Discs):

Answer 7

Location: Found in the epidermal-dermal junction of the skin, associated with nerve endings.
Detection: Responsible for the perception of sustained touch and pressure, as well as shapes and edges.

Question 8

Ruffini Corpuscles:

Answer 8

Location: Situated in the deep layers of the skin.
Detection: Sensitive to skin stretch and deformation. They detect continuous pressure and joint position.

Question 9

Free Nerve Endings:

Answer 9

Location: Distributed throughout the skin and various tissues.
Detection: These receptors are not specialized for any specific type of mechanical stimulus. Serve as nociceptors, responding to pain, and thermal receptors, detecting temperature changes.

Question 10

Describe the process of sensory transduction in somatosensory afferents

Answer 10

1) Stimuli applied to skin changes the shape of receptor
2) This deformation triggers receptor potential through mechanical ion channels, leading to cell depolarization.
3) If the summation of excitatory postsynaptic potentials (EPSPs) in the trigger zone reaches the threshold, an action potential is generated.
3) AP travel down dorsal root ganglion sensory afferent to CNS​
4) The type of sensation (pressure, stretch, vibration) is determined by the specific receptor properties.

Question 11

What determines the quantity or strength of a stimulus in somatosensory afferents?

Answer 11

The quantity or strength of a stimulus is determined by the rate of action potentials generated in response to the stimulus

Question 12

What determines the quality of a stimulus in somatosensory afferents?

Answer 12

The quality of the stimulus is determined by the receptor properties and the specific CNS target to which the sensory information is sent.

Question 13

Where are somatosensory afferent receptors typically located, and where is the cell body in this system?

Answer 13

Somatosensory afferent receptors are often located in the periphery, such as the skin. The cell body is in the dorsal root ganglion, situated outside the brain and spinal cord.

Question 14

What is sensory neuron adaptation?

Answer 14

Sensory neuron adaptation is the process where our nerves become less responsive to a constant stimulus if it doesn’t change. in position or amplitude

Question 15

What happens to our response when a stimulus remains constant over time?

Answer 15

If a stimulus persists without changing, our response to it becomes less intense due to sensory neuron adaptation.

Question 16

Where does sensory neuron adaptation occur?

Answer 16

Sensory neuron adaptation takes place in both the central nervous system (CNS) and the peripheral nervous system (PNS).

Question 17

What are the two main ways sensory receptors can adapt to a stimulus?

Answer 17

Sensory receptors can adapt in two main ways: slowly adapting (tonic signal) and rapidly adapting (phasic response).

Question 18

Why is the phasic response important in sensory perception?

Answer 18

The phasic response is crucial for informing you when something begins or ends, allowing you to perceive both static and dynamic qualities of a stimulus.

Question 19

What characterizes a rapidly adapting signal in receptor adaptation?

Answer 19

These signals react quickly when a stimulus starts or changes, but then stop responding if the stimulus stays the same

Question 20

What characterizes a tonc signal in receptor adaptation?

Answer 20

These signals keep responding at a steady rate for as long as the stimulus continues without changing.

Question 21

What is the adaptation pattern of messier corpuscles?

Answer 21

Meissner corpuscles respond to low-frequency vibrations and are rapidly adapting. They are well-suited for detecting texture moving across the skin.

Question 22

What type of stimuli do Pacinian Corpuscles respond to?

Answer 22

Respond to high-frequency vibrations and fine textures, especially softer ones.

Question 23

How do Pacinian Corpuscles adapt to stimuli?

Answer 23

Pacinian Corpuscles adapt rapidly, providing information about dynamic changes in stimuli

Question 24

How do Merkel Cells adapt to stimuli? (only slow adapting)

Answer 24

Merkel Cells adapt slowly, allowing them to provide constant feedback about static stimuli.

Question 25

How do Ruffini Receptors adapt to stimuli?

Answer 25

These are slow-adapting receptors that respond to stretching and internally generated stimuli

Question 26

What characterizes slowly adapting receptors in terms of their response to stimuli?

Answer 26

Slowly adapting receptors exhibit persistent depolarization and continuous action potentials in response to stimuli.

Question 27

What is the primary characteristic of rapidly adapting receptors?

Answer 27

Only respond to increases or decreases in intensity of a stimulus but not to constant or persistent stimuli.

Question 28

Receptive Field

Answer 28

specific area on the sensory receptor or sensory neuron’s surface from which a response can be generated in response to an adequate stimulus.

Question 29

How does the number of mechanoreceptors associated with a neuron affect the field of response and the information sent to the CNS?

Answer 29

The more mechanoreceptors associated with a neuron, the wider the field of response. This, in turn, impacts how much sensory information the central nervous system (CNS) receives from the periphery.

Question 30

How is the sensitivity of a sensory system measured?

Answer 30

Sensitivity is measured through a concept called two-point discrimination: determines the minimum distance required to perceive two distinct stimuli.

Question 31

What factors influence the sensitivity of a sensory system?

Answer 31

The concentration of receptors and the size of the field of response are factors that influence the sensitivity of a sensory system.

Question 32

How does the size of the field of response impact sensitivity in a sensory system?

Answer 32

A larger field of response allows the system to detect stimuli over a wider area, while a smaller field of response limits sensitivity to a more localized region.

Question 33

How does a high concentration of receptors affect sensitivity in a sensory system?

Answer 33

A high concentration of receptors in a region increases sensitivity, making that area more responsive to stimuli.

Question 34

How does the depth of receptors in the skin affect the size of their receptive field?

Answer 34

Receptors closer to the surface have smaller receptive fields, while deeper receptors have larger receptive fields.

Question 35

What are muscle spindles?

Answer 35

Muscle spindles are sensory receptors located in skeletal muscles.

Question 36

What type of changes do muscle spindles signal?

Answer 36

Muscle spindles signal changes in the length of skeletal muscles.

Question 37

What kind of information do muscle spindles provide about the body?

Answer 37

Muscle spindles provide information about the relative positions of body segments.

Question 38

What are the three main components of a muscle spindle?

Answer 38

1) Intrafusal muscle fibers.
2) Sensory afferent endings (Large Myelinated Sensory Endings ex: (Primary and Secondary Endings).
3) Efferent motor endings (Small Myelinated Motor Endings (ex: Gamma Motor Neurons):.

Question 39

What are intrafusal muscle fibers?

Answer 39

Intrafusal muscle fibers are specialized muscle cells within the muscle spindle that respond to changes in muscle length.

Question 40

What is the role of sensory afferent endings in a muscle spindle?

Answer 40

Sensory afferent endings are nerve endings that detect and transmit information about muscle length and changes to the nervous system.

Question 41

What is the role of efferent motor endings in a muscle spindle?

Answer 41

Nerve fibers that also travel from the CNS to the intrafusal muscle fibers within the spindle, regulating their activity

Question 42

What are the two main types of intrafusal muscle fibers?

Answer 42

The two main types of intrafusal muscle fibers are nuclear chain fibers and nuclear bag fibers.

Question 43

What are the subtypes of nuclear bag fibers, and how are they classified?

Answer 43

Nuclear bag fibers have two subtypes: dynamic bag fibers and static bag fibers. They are classified based on their responsiveness to changes in muscle length.

Question 44

What sets dynamic bag fibers apart from static bag fibers?

Answer 44

Dynamic bag fibers, specifically type Ia fibers, monitor the rate of change in muscle length, while static bag fibers, which include both type Ia and type II fibers, monitor the length of the muscle.

Question 45

What are the two main types of sensory afferent endings in muscle spindles?

Answer 45

The two main types are the primary sensory ending (Group Ia) and the secondary sensory ending (Group II).

Question 46

How does spindle density vary in different parts of the body?

Answer 46

Spindle density varies depending on the importance of movement accuracy needed for that area. Areas requiring fine motor skills, such as the hands, neck, and extraocular muscles of the eye, have a higher spindle density.

Question 47

What are muscle spindle receptors, and what happens when you stretch them?

Answer 47

Muscle spindle receptors are sensory nerve fibers wrapped around intrafusal muscle fibers. When you stretch them, their activity increases, leading to more action potentials.

Question 48

What is the effect of loading vs. unloading the muscle spindle?

Answer 48

Loading the muscle spindle increases its sensitivity and responsiveness, while unloading it decreases its sensitivity and responsiveness

Question 49

What is the function of gamma motor neurons in relation to muscle fibers?

Answer 49

Gamma motor neurons connect from the spinal cord to intrafusal muscle fibers, extending from the central nervous system (CNS) to the periphery.

Question 50

How do dynamic gamma motor neurons affect the sensitivity of muscle spindles?

Answer 50

Dynamic gamma motor neurons are responsible for increasing the sensitivity of primary sensory endings in muscle spindles (sensory receptors become more responsive to changes in muscle length,_

Question 51

What happens to the sensory ending (Ia) in the muscle spindle when the muscle stretches and contracts?

Answer 51

When the muscle stretches, the sensory ending (Ia) becomes excited, but it becomes less active when the muscle contracts. Gamma motor neurons help maintain its sensitivity during muscle contractions.

Question 52

What is alpha-gamma co-activation, and why is it important?

Answer 52

Alpha-gamma co-activation is when both alpha motor neurons (for muscle contraction) and gamma motor neurons activate together. It’s crucial for muscle contraction and staying responsive to external stimuli.

Question 53

What occurs when the muscle is contracted, and how does it affect the muscle spindle?

Answer 53

When the muscle is contracted, the muscle spindle becomes “saggy” and insensitive, leading to reduced Ia afferent output.

Question 54

What effect do static motor efferent neurons have on muscle spindle activity?

Answer 54

Static motor efferent neurons increase tonic activity in both primary and secondary endings of the muscle spindle (making them more sensitive to maintain awareness of muscle length and position )

Question 55

How do static gamma motor efferents influence tonic activity in muscle spindles?

Answer 55

Static gamma motor efferents can change the tonic activity in muscle spindles.

Question 56

Why is coordination with the alpha motor system important for static gamma motor efferents?

Answer 56

Coordination with the alpha motor system is crucial to ensure that the tonic information provided by muscle spindles remains accurate and reliable

Question 57

What is the role of Golgi Tendon Organs (GTOs) in relation to muscle fibers?

Answer 57

Golgi Tendon Organs (GTOs) sit in series with muscle fibers and measure force generated by muscles.

Question 58

How does the activity of GTO afferents change with increasing muscle force?

Answer 58

As the force generated by active muscles increases, the afferent activity of GTOs going into the spinal cord also increases, resulting in a higher action potential rate.

Question 59

Is the relationship between GTO activity and force linear or non-linear?

Answer 59

The relationship between GTO activity and force is non-linear. The action potentials generated are not directly proportional to the amount of force produced.

Question 60

What’s the main job of Golgi Tendon Organs in muscle activity signaling?

Answer 60

Golgi Tendon Organs primarily signal changes in muscle force rather than giving an exact measure of constant muscle contractions.