NPB101: Neurophysiology Part 6

Examples of Sensory Transduction & Higher Brain Function

Touch

Pressure (skin)

Vision

Lightwaves

Hearing

Pressure waves traveling through air

Vestibular System

• Central Balance

• detect where body is relative to space/gravity

Transducing/Transduction

changing the energy of the stimulus (chemical) into an electrical signal to basically a bunch of AP

General Somatic Sensory Afferent

Touch sensitive neurons that are innervating the skin

Innervating

supply (the body/skin) with nerves

General Somatic Senses: Touch Receptor

Embedded in the skin

What is the name for these Touch Receptors

Mechanosensitive Neurons

What happens when you apply a stimulus to the dendrite

1. It deforms the dendrite/channel

2. the mechanical pressure pushes on the dendrite to open the ion channel with a depolarizing current of Na+ influxing into the cell

3. The influx is from touching the finger

4. When we get this depolarizing influx we create a graded potential, but the depolarizing influx creating graded potential is a “Receptor Potential”

When you have a depolarizing influx you create a graded potential, this ____ potential is called a _____ potential

graded, Receptor

Receptor Potential

travels through the dendrite and cell of body of neuron and then finally to axon

Axon Hillock Facts

• front of the axon

• depolarize the neuron —→ AP—→ localized current

Touch Receptors

• Uncapsulated, free nerve endings —→ Free Neuron Ending

• Encapsulated nerve endings —→ special channel in the dendrite and then opens channel and depolarizes

  • Meissner’s corpuscle

  • Merkel’s corpuscle

  • Pacinian corpuscle

Free Neuron Ending

• slowly adapting

• free nerve endings

• no special structure at the end

• itch receptor

• thermoreceptors

• uncapsulated

Meissner’s Corpuscle

touch and pressure, rapidly adapting

Merkel’s Corpuscle

touch and pressure, slowly adapting

Pacinian Corpuscle

Dendrite with cells wrapped around it, rapidly adapting

Afferent Process

Like a dendrite, senses

Afferent moves through

Spinal Cord, Thalamus, Medulla (brainstem), Cortex

Touch info is sent to the ___, with the Dorsal ____ pathway

brain, Columnar

Dorsal Columnar Pathway: TOUCH SENSITIVE PATHWAY

• 3 Neuron pathway

• info crosses at the brain stem (medulla)

If there is pain is crosses over to the ____ ____ & this is ____ order neuron

spinal cord, second

If you touch something it crosses over to the ______ & this is ____ order neuron

brainstem, second

NOCICEPTIVE NEURONS

• Pain info is carried by this

• Detects painfully strong stimuli

T/F: Nociceptive neurons cross over at the spinal cord

True, nociceptive neurons detects painful strong stimuli and carries pain info to the Anterolateral Pathway(Spinothalamic pathway), pain sense from the general somatic sense of cutaneous pain cross overs at the spinal cord with second order neuron

Anterolateral Pathway (Spinothalamic pathway),

Pain

T/F: Mechanosensor neurons cross over at the brainstem (medulla)

True, Mechanosensor neurons that detect normal touch with General Somatic Sensor cross over at the brainstem (medula) via the Dorsal Columnar Pathway with second order neuron in spinal cord trasmitting info to third order where it crosses at brainstem

Primary Somatosensory Cortex

• Homunculus

• First part of Cerebral Cortes involved in conscious perception of general somatic senses (touch, pain, temperature)

Homunculus

Body Representation

Homunculus is part of the ____ somatosensory cortex that is involved in the ___ somatic sensory (touch,____, temperature)

Primary, General, pain

Central Sulcus

Process Somatic Afferent information (touch)

Conscious Perception of Touch

Greater in thumb, lips

Pain Withdrawal Reflex

cause activation of certain muscles so we can pull away the organ (limb) while shutting off action of a given muscle

Pain Withdrawal Reflex Example

Want to contract hamstring to pull away limb (leg) that is experiencing the pain on the foot when you step on a tack and then contract muscle in the quads on the other leg or else you’ll fall

Retina

• detects photoreceptor

• sees fine detail

Cornea & Lens

Help focus image onto Retina

Iris

• Limits the amount of light that enters via pupil

• is the color we see in peoples eyes

Light

comes in through the cornea, pass the iris, through the lens, and it shoots across to the retina

Ganglia Cell (in Retina)

neuron that takes sensory info to the brain (thalamus)

Photoreceptors

• Cones

• Rods

Cones

Allow iris to detect color of wavelength

Rods

hardly any stimuli in dark so its used in low light situations & bright situations

Photopigments

• Rhodopsin

• Cone opsins

• In outer segment of photoreceptors(cones & rods)

• change shape when light waves are absorbed

Rhodopsin

Rods photopigment that detects visible wavelength

Cone opsin

Cone photopigment

The ___ segment of cones and rods have layers of ____

outer, photopigment

11-cis

Before exposure to a light wave

All trans

After exposure to a light wave

Dark Current

in the dark where cGMP opens/activates a channel where a depolarizing current occurs

cGMP

open Na+ channels within the outer segment of photoreceptors

T/F: Even if you don’t have lightwaves on stimulus it depolarizes

True, you don’t have to have a stimulus (light) in order to depolarize in the eye, so the photoreceptor depolarizes to darkness and it continually releases neurotransmitters

Absorbing Light Waves

when exposed to light the photopigment absorbs it and changes shape because it changes from the 11-cis(bent) to all-trans (straight)

Phosphodiesterase (PDE)

an enzyme that when activated it decreases cGMP (closes dark current channel)

T/F: When there is lightwaves neurotransmitters stop from getting released

True, This is because in the eye neurotransmitter release it opposite as when you have a stimulus=no neurotransmitter release & when there is no stimulus=neurotransmitter released

Cones have a 1:1:1 connection with?

Rods: bipolar cells: afferent neurons(single ganglion cell)

Afferent Neuron (Single Ganglion Cell)

• have a big receptive field with all the bipolar cells and it goes to the photoreceptors

• so many bipolar cells this is a big receptive field where it cannot detect fine detail

Macula Densa

• this is where rods are

• Part of retina where this is all rods

ON center/OFF surround

Ganglion Cell fires off AP at center, but decrease AP in the surround

OFF center/ON surround

Ganglion cells fire off in surround (periphery) but when in center it dec AP

T/F: The left visual field is processed by the left visual cortex

False, the left visual field is processed by the right visual cortex

Right Visual Cortex is processed by the ____ brain

Contralateral

The left Visual Cortex is processed by the ____ brain

bilateral

The guy playing saxophone

signal (dark color) is where our attention goes

Women’s face

noise (white color) is something we tend to ignore

The brain loves to perceive where its supposed to signal

As if something is supposed to be there the “dark dots” this is the blind spot (fill in blind spot)

Sound Waves

Pressure Wave (air or solid)

Auditory Canal

receives sound waves

Tympanic Membrane

Vibrates

Inner Ear Bone

concentrate sound wave energy to one spot (Cochlea)

Where is the soundwaves concentrated to, what area of the ear?

Cochlea

Chambers

1. Scala Media

2. Scala Tympani

3. Scala Vestibuli

M.T.V.

Sensory Cell- Hair cell

• sensory receptor

• pays attention to sound waves

Sound Waves are _____ by hair cells

transduced

Sound Waves Working

can zip all the way across/ cut across

Stereocilia

• Bend towards & away from the Kinocilium

• Bends Towards—→Hair cell depolarize

• Bends Away—→ Hair cell hyperpolarize

Hair cell Bend Towards Kinocilium

the hair cell depolarizes

Hair bends away from the Kinocilium

the hair cell hyperpolarizes

Basilar Membrane

a flexible membrane that vibrates in response to sound and varies in stiffness along its length to distinguish different frequencies

High Pitch

High Frequency

Hair cells in cochlea are maximally activated a specific locations along the basilar membranes based on pitch frequency

maximally activated

highest possible level of activity or response

T/F: Stereocilia grows back

False stereocilia cannot grow back once destroyed

High Pitch

base of membrane

Low Pitch

Tip of membrane