Lecture 23

Question 1

What do sensory neurons carry

Answer 1

Afferent signals
- in and up
- info about the environment

Question 2

What is neuron 1 in the somarosensory cortex

Answer 2

• This neuron starts at the sensory receptor in the body, such as in the skin.
  
  • Its cell body resides in the dorsal root ganglion, which is located just outside the spinal cord.
  • The peripheral fiber of neuron #1 carries sensory information from the receptor to the central nervous system.
  • The central fiber of neuron #1 ascends towards the brain through the dorsal columns of the spinal cord white matter.
  • Neuron #1 synapses on neuron #2 in the medulla oblongata.

Question 3

Dendrites: ion Chanel location in sensory neurons

Answer 3

Chemically or mechanically gated ion channels ( Na+ and K+ )

Question 4

What is the dendrities and cell body ion channel location in the intermediate and motor neurons

Answer 4

Chemically gated ion channels ( Na+ and K+ )

Question 5

What is the axon ion channel location

Answer 5

Voltage gated ( Na+ and K+ ) channels

Question 6

What is the Axon thermals, ion channel location

Answer 6

Voltage gated Ca2+ channels

Question 7

What is the sensory neurons, somatic senses

Answer 7

Detected by the receptors in the skin, muscle and joints

Question 8

What is the Visceral senses in the sensory neurons

Answer 8

Detected by recptors in the internal organs

Question 9

What does sensory detection require

Answer 9

Stimulus transduction

Question 10

What does transduction mean

Answer 10

Convert or change from one form to another

Question 11

What is sensory transduction

Answer 11

Conversion of sensory stimulus into an action potential

Question 12

Please tell me an example of stimulus transduction

Answer 12

• when you touch something with your finger
• …a mechanoreceptor in the skin of your fingertip gets squished.
• This deforms the membrane, opening mechanically-gated Na+ channels
• …allowing Na+ to enter and depolarise the membrane
…sending action potentials to the brain to make you aware of the touch.

Question 13

What are the 4 types of information encoded by neural activity

Answer 13

• modality
• duration
• intensity
• location

Question 14

What is modality

Answer 14

A type of stimulus detected by a specific type of receptor

Question 15

Duration

Answer 15

Time period of which action potentials fire in afferrent neurons

Question 16

Intensity

Answer 16

Rate ( frequency ) of action potential firing in afferent neurons

Question 17

Location

Answer 17

Location of receptors withen the body. The somatosensory cortex has a map of locations from which it receives action potentials

Question 18

What are the 4 examples of modality of stimulus

Answer 18

• thermoreceptor
• chemoreceptor
• there are 3 types of mechanoreceptors, 1) tactile receptors 2) proprioreceptor 3) baro receptor
• nociceptor

Question 19

What is thermo receptor and give an example

Answer 19

This is for temperature, so a stimulus example is relative temperature ranges

Question 20

What is chemoreceptor

Answer 20

Chemical and a stimulus examples is CO2, O2, H concentration in blood

Question 21

What isn’t mechankreceptor

Answer 21

There are 3 basic mechano receptors
1) tactile receptor, this is for skin touch, SE: light touch, pressure, texture, vibration, stretch
2) propriceptor, this is propriception, SE: stretch or tension in skin, muscle and/or tendon
3) baro receptor this is pressure , SE: stench of visceral tubes ( eg: blood vessels, airways, intestines)
- Nociceptor! This is for PIAN, SE: excess temperature, chemical or mechanical stimuli

Question 22

In depth of thermoreceptors

Answer 22

Thermorecetoes are nerve endings with temperature gated ion channels, they can sense a range of temperature and are sensitive to both increase and decrease of temperatures and are FAST ADAPTING.

Question 23

Transduction of tempeture stimuli

Answer 23

Temperature stimuli opens temperature gated Na+ channels,
Allowing Na+ to enter and depolarise the membrane
If the threshold is reached in the thermoreceptor, an action potential will fire and propagate the brain.

Question 24

In-depth of chemo receptors

Answer 24

These are specialised receptor cells with chemically gated ion channels
They respond to different chemical concentrations

Question 25

Transduction of chemical stimuli

Answer 25

This is the same as the tempeture one: Chemical stimuli bind and open chemically gated Na+ channels, Allowing Na+ to enter and depolarise the membrane If the threshold is reached in the thermoreceptor, an action potential will fire and propagate the brain. A PH sensitive cell is an example of,e of an chemoreceptor

Question 26

In depth about Mechaoreceptos

Answer 26

They are nerve endings with mechanical,t gated ion channels They respond to physical forces that distort the plasma membrane ( deformation

Question 27

Transduction of mechanical stimuli

Answer 27

Mechanical stimuli deform the membrane causing mechanically gated Na+ channels to open This allows Na+ to move in and depolarise the membrane And is the threshold is reached in the menchnoreceptor, an action potential will fire and propagate to the brain

Question 28

Mechanoreeceptors: tactile receptor

Answer 28

- responds to light touch, pressure, vibration and stretch of skin - Some are tonic ( slow adapting ) - some are phasic ( fast adapting )

Question 29

Me hnoreceptors: proprioceptors

Answer 29

- respond to stretch, tension in receptors - inform about limb position - are tonic ( slow adapting )

Question 30

Mechanicoreceptors: baro receptors

Answer 30

- detect pressure in/strech of tubes ( eg:blood sugar )

Question 31

In depth of Nociceptors

Answer 31

- this is a Nerve ending that responds to noxious stimuli ( harmful, painful ) and is tippically caused by tissue damage - They have either temperature gated, chemically gated or mechicallt gated ions channels responding to extreme stimuli - are tonic ( slow adapting )

Question 32

Transduction of noxious stimuli

Answer 32

Noxious stimuli causes ion channels to open allowing Na+ to enter and depolarise the membrane If the threshold is reached in the nociceptor, an action potential will fire and propagate to the brain

Question 33

Duriation of stimulus, tonic receptors

Answer 33

Tonic receptors are continually active, providing a continuous signal to the central nervous system (CNS) that reflects the background level of stimulation. - These receptors maintain a relatively constant firing rate over time, even in the presence of a sustained stimulus. - The action potential (AP) frequency may change when the intensity of the stimulus changes, but the receptors continue to respond as long as the stimulus is present. - Tonic receptors are associated with slowly adapting responses, meaning they continue to respond for a prolonged duration to sustained stimuli. - Examples include muscle spindles involved in proprioception (sensing body position and movement) and nociceptors responsible for detecting pain.

Question 34

Duration of stimuli, phasic receptors

Answer 34

- Phasic receptors, on the other hand, respond rapidly to changes in the stimulus but adapt quickly to sustained stimuli. - They are characterized by a burst of activity when the stimulus is first applied but then rapidly decrease their firing rate, becoming less responsive over time if the stimulus remains constant. - Phasic receptors are associated with fast-adapting responses, meaning they quickly adapt to sustained stimuli and may stop firing even if the stimulus is still present. - Examples include receptors for touch, vibration, and pressure, which are crucial for detecting changes in the environment but may become less responsive to constant stimuli.

Question 35

Intensity of stimulus, action potential frequency

Answer 35

NO AP = NO SENSATION SOME AP = SOME SENSATION MORE AP = MORE INTENSE SWNSATION

Question 36

Intensity of stimulus, Ap frequency plus number of neurons activated

Answer 36

- below threshold there is no response in afferent neuron - increasing stimulus increases action potential frequency - stronger stimuli can also activate more receptors and action potentials in more sensory axons

Question 37

Location of stimulus, receptive Feilds

Answer 37

• The area of skin with receptive endings for a single sensory neuron • 1 receptive field to 1 sensory neuron Size and density of receptive fields affect discriminatory touch (sensitivity) and ability to localize a stimulus.

Question 38

Location of stimulus - size and density of receptive Feilds - sensitivity and localisation

Answer 38

Large and more widely spaced receptive fields provide: • less sensitivity and • less accurate localization • e.g. in arms, legs, torso Small and densely packed receptive fields provide: • More sensitivity (better two- point discrimination) • more accurate localization e.g. hand, fingers and lips

Question 39

Location of stimulus - sometorsensory cortex map

Answer 39

Somatic sensory neurons send signals from different parts of the body and Up axons within the dorsal column pathway to the somatosensory cortex of the brain Creating a somatotopic map

Question 40

Location of stimulus , receptive Feilds and the somatopic map. TRUNK TORSO AND LIMBS

Answer 40

• Areas of skin with larger receptive fields so this has less representation in the brain because there are fewer neurons involved Remember: 1 sensory neuron per receptive field

Question 41

Location of stimulus : lips and hands, receptive Feilds and somatopic map

Answer 41

• Areas of skin with smaller receptive fields • have more representation in the brain because there are more neurons involved Remember: 1 sensory neuron per receptive field