Brain and Behavior Module 2 SI Session Flashcards

Sensory Transduction

the process by which sensory stimuli are transduced into nerve impulses so the CNS can understand them

Ionotropic Sensory Receptors

Mechanoreceptor

Thermoreceptor

Electroreceptor

Metabotropic Sensory Receptors

Chemoreceptor

Photoreceptor

Labeled Lines

each sensory modality follows a specific path to/within the CNS

General Sensory Pathway

1. Afferent sensory nerves

2. Spinal cord

3. Brainstem

4. Thalamus

5. Primary Sensory Cortex

6. Nonprimary Sensory Cortices

Touch and Pressure Receptors - Epidermis

1. Free Nerve Endings (temperature and pain)

Touch and Pressure Receptors - Dermis

1. Merkel's Disc (touch)

2. Meissner's Corpuscle (touch)

3. Hair Follicle Receptors (touch)

Touch and Pressure Receptors - Hypodermis

1. Pacinian Corpuscle (vibration and pressure)

2. Ruffini Corpuscle (stretch)

Layers of the skin

Epidermis (most outer layer), Dermis (middle layer), Hypodermis (most inner layer)

Pacinian Corpuscle Depolarization

Stimuli: vibration and pressure

At Rest: ion channels "plugged" closed

When Stimulated: plug is removed - influx of cations - EPSP - can cause an action potential

Receptive Field

portion of sensory space that can elicit a neuronal response when stimulated

Effect of stimuli in a receptive field

Graded depolarization

Effect of stimuli in area surrounding a receptive field

Graded hyperpolarization (inhibition - moving nerve farther away from firing an action potential)

Effect of stimuli outside of a receptive field

No effect

Dermatome

area of skin innervated by a specific spinal nerve

What can cause a rash on your skin?

a problem with the spinal nerve that innervates that skin area (dermatomes)

Where is the primary somatosensory cortex?

Postcentral gyrus (parietal lobe)

Where is the primary motor cortex?

Precentral gyrus (frontal lobe)

Similarity between primary somatosensory and primary motor cortexes?

Both display a homunculus - more area is devoted to parts of the body that move a lot (motor) or require a lot of fine touch processing (somatosensory)

What tract does touch and pressure travel on?

Medial Lemniscus Tract

What is a tract?

Bundle of axons in the CNS

Pathway of touch and pressure

1. Specialized nerve endings in skin

2. Stimulus applied and sensory transduction occurs to create nerve impulse

3. Nerve impulse travels to dorsal root ganglion of spinal cord

4. Nerve impulse travels to dorsal white matter and ascends the spinal cord along myelin

5. First synapse from dorsal white matter onto dorsal column nuclei in the medulla

6. Crosses over midline and follows medial lemniscus tract

7. Medial lemniscus tract synapses onto thalamus

8. Information is sent to primary somatosensory cortex in the parietal lobe

9. Information can then be sent to association cortices in frontal or parietal lobes

Where is the first synapse in the pathway of touch and pressure? Second?

Onto dorsal column nuclei; Onto thalamus

When does touch and pressure information crossover the midline?

Between the dorsal column nuclei in the medulla and medial lemniscus tract, the neuron crosses over

What is the universal sensory receptor?

There is NOT one!

What is the pathway of the universal labeled line?

There is NOT one!

What is another name for the pacinian corpuscle?

Lamellated Corpuscle

The _______ pathway carries touch information to the brain, while the _________ pathway carries pain information to the brain.

Medial lemniscus tract; Spinothalamic

Differences between dermatomes and labeled lines

Dermatomes: innervation of spinal nerves to specific parts of the skin

Labeled Lines: specific nerve receptors traveling to CNS

Where does synesthesia occur?

Association Cortices

Synesthesia

when one kind of sensory stimulus evokes the experience of another

ex. tasting a sound

Spinothalamic Pathway

1. Damage to cells

2. Substances are released that cause inflammation and signal nociceptors

3. Free Nerve Endings in epidermis generate action potentials

4. AP sent to dorsal root ganglion through A-delta and C fibers

5. First synapse onto grey matter in the dorsal horn where Substance P and Glutamate are released and pain fibers are signaled

6. AP crosses the midline in dorsal horn of spinal cord

7. AP ascends the spinal cord and travels to the brainstem

8. Second synapse onto the thalamus

Substance P

tells the brain the INTENSITY of the pain

(more Substance P, more intense the pain is)

Glutamate

tells the brain that there IS pain

Pain Fibers

A-delta (fast, myelinated) and C fibers (slow, unmyelinated)

A-Delta Fibers

sharp, immediate pain right when a painful stimulus occurs

C Fibers

slow, dull ache after a painful stimulus has occurred

What kind of pathway does touch/pressure follow? Pain/temperature?

Medial Lemnicus Tract; Spinothalamic Tract

Where does pain information crossover?

The Dorsal Horn

Pons - in pain

axons may branch out from here to send pain information traveling through the brainstem to other parts of the brain (ie. speech portion to cause you to yell)

Anterior Cingulate Gyrus - in pain

involved in the perception of pain

What happens if you have a lesion on the anterior cingulate gyrus?

You can not feel pain anymore

What happens to the pain pathway if you sever the right side of the spinal cord? Why?

You cannot feel pain on the left side of your body

This happens because pain information crosses over in the spinal cord, so if the right is severed, information from the left side will not be able to crossover to the right side of the spinal cord to ascend to the CNS and process the pain

What happens to the touch pathway if you sever the right side of the spinal cord? Why?

You cannot feel touch on the right side of your body

This happens because touch information crosses over in the brain, so the touch information from the right side is able to travel up the right side of the spinal cord, but will not be able to reach your brain to crossover to the left side of your brain to process the touch

Where is the first synapse in the spinothalamic pathway? Second?

Onto the dorsal horn; Onto the thalamus

Which synapse is the same between the medial lemniscus pathway and the spinothalamic pathway? Different?

The second synapse onto the thalamus is the same in both

The first synapse is different for the two pathways:

- Medial Lemniscus (onto dorsal column nuclei in brain)

- Spinothalamic (onto dorsal horn in the spinal cord)

Nociceptors

pain receptors found on free nerve endings in the epidermis

In pain, what is the neuromodulator and what is the neurotransmitter?

Neurotransmitter: Glutamate

Neuromodulator: Substance P

Neuropathic Pain

pain that occurs with no obvious injury or long after an injury has healed

Example of neuropathic pain

Phantom limb pain

Neural Plasticity

our brain is able to change and adapt its connections based on our experiences.

Voluntary Motor System Pathway from Brain to Muscle

1. Association Corties

2. Primary Motor Cortex

3. Thalamus and Brainstem

4. Pyramid of Medulla

5. Crosses over in Lower Medulla

6. Ventral Spinal Cord

7. Skeletal Muscle

Which part of the spinal cord is where information ascends? Descends?

Dorsal; Ventral

Other name for neuromuscular junction

Motor endplate

What is a neuromuscular junction?

Synapse between efferent motor neuron and a skeletal muscle

What neurotransmitter is released at the neuromuscular junction?

Acetylcholine

How is acetylcholine released at the neuromuscular junction?

1. Action potential from the efferent motor neuron reaches the axon terminal

2. Voltage-gated Ca channels open and Ca2+ rushes into axon terminal

3. Ach is released via Calcium dependent exocytosis

4. Ach attaches to receptors on the postsynaptic muscle cell membrane, causing an action potential in the muscle cell and causing the muscle fibers to contract

What does a muscle spindle detect?

Stretch in muscle fibers

What does Golgi tendon organ detect?

Tension in our muscle tendons

Stretch-Reflex Circuit

1. Muscle stretches

2. Muscle spindle is activated

3. Muscle spindle sends action potentials via an afferent sensory fiber through the dorsal root ganglion of the spinal cord

4. Synapse is made in gray matter of spinal cord with motor efferent neuron

5. Motor efferent neuron sends TWO branches: one to agonist muscle to contract, and one to antagonist muscle to relax

6. Synapse at neuromuscular junction

Withdrawal Reflex Circuit

1. Nociceptors sense pain

2. Afferent sensory neurons send action potentials to the dorsal root ganglion

3. Action Potential follows spinothalamic pathway

4. Collateral action potential synapses onto the gray matter of spinal cord

5. Motor efferent neuron sends TWO branches: one to agonist muscle to contract, and one to antagonist muscle to relax so you can quickly pull that body part away from the source of pain

Pathway of sound through the ear

1. Pinna

2. Ear Canal

3. Causes vibration of tympanic membrane

4. Causes movement of ossicles

5. Ossicles transfer vibration through oval window

6. Once through oval window, vibration reaches the cochlea

7. Hair cells on the cochlea transduce the signal into a nerve impulse

8. Nerve impulse sent through auditory nerve to the brain

What membranes are the cochlear hair cells embedded between?

Basilar and Tectorial

Organ of Corti

Cochlear hair cells + basilar membrane + tectorial membrane

What sounds does the apex of the cochlea respond to? What about the base?

Low frequency (bass); High frequency

Tonotopic Organization

an arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency

What are the bases of cochlear hair cells attached to?

The bases reach into the basilar membrane and are attached to the vestibulocochlear nerve

Where are stereocilia?

The tips of cochlear hair cells

Tip Links

Structures at the tops of stereocilia, which stretch or slacken as the stereocilia move, causing ion channels to open or close

allow/prevent neurotransmitters to be released onto the vesticulocochlear nerve

What are cochlear hair cells very receptive to? What effect does this have?

Very receptive to mechanical stress which is how hearing loss occurs

Pathway of sound in the brain to primary sensory cortices

1. AP generated in vestibulocochlear nerve

2. Synapses at the cochlear nuclei

3. Synapses at the superior olive

4. Synapses on the inferior colliculus

5. Synapses on medial geniculate nucleus (thalamus)

6. Reaches the auditory cortex

7a. Anterior Auditory Cortex

7b. Posterior Auditory Cortex

Anterior Auditory Cortex

WHAT a sound is

frontal lobe

Posterior Auditory Cortex

WHERE a sound is (localization)

parietal lobe

Binaural Hearing

the ability to hear in two ears

Onset Disparity

the latency difference between the two ears for the beginning of a sound

Ongoing Phase Disparity

the difference between the ears for arrival of the peaks and troughs of the sound wave

Conduction Deafness

problem with the outer or inner ear that prevents vibrations from reaching your cochlea

Sensorineural Deafness

problems with the cochlea that prevent sensory transduction

Central Deafness

damage to auditory brain structures

Analgesia

the inability to feel pain

Proprioception

understanding what your body is doing in space

Interoception

sensation from inside of our bodies

Exteroception

outside stimuli being sensed by our skin

Where does somatosensory information from the head and face enter the CNS?

Cranial Nerves

Where does somatosensory information from the neck and below enter the CNS?

Spinal Cord

Association Cortices Purpose

Areas within the brain that integrate different types of information

Amplitude

height of the sine wave (dB)

intensity of sound

Frequency

how frequently the sine wave is occurring (Hz)

pitch

Ossicles

Malleus (hammer), Incus (anvil), and Stapes (stirrup)

Most common cause of hearing loss

Damage to cochlear hair cells

Five tastes

Salty, Sour, Bitter, Sweet, Umami

Which tastes are sensed by ionotropic receptors?

Salty and Sour

What ions are important in tasting salt? Sour?

Salt - Na+

Sour - H+ (acid)

Which tastes are sensed by metabotropic receptors?

Bitter, Sweet, Umami

When tasting umami, what are we actually tasting?

Glutamate

Papillae

Bumps on our tongue

Taste Buds

Clusters of non-neuronal sensory receptor cells on the sides of our papillae

Microvilli

projections on our taste buds that trap tastant molecules

Gustatory Pathway

1. Tongue innervated by three cranial nerves

2. Cranial nerves synapse onto Solitary Tract Nucleus

3. Synapse onto thalamus

4. Brought to gustatory cortex (in the limbic system)

What three cranial nerves innervate the tongue?

Facial Nerve - tip of the tongue

Glossopharyngeal Nerve - middle of the tongue

Vagus Nerve - back of the tongue