COGS

Question 1

Four mechanoreceptors specialised for touch

Answer 1

-Merkel cell afferents
-Meissner afferents
-Pacinian afferents
-Ruffini afferents

Question 2

Merkel cell afferents

Answer 2

― Slowly adapting fibers
― Comprise ~25% of the mechanosensory afferents in the hand
― prominent in the fingertips
― Only afferents to sample information from receptor cells in the epidermis
― Express Piezo2
― Highest spatial resolution of all afferents makes them effective at detecting fine edges, points, curves of objects

Question 3

Meissner afferents

Answer 3

Rapidly adapting fibers
― Comprise ~40% of the mechanosensory afferents in the hand
― Corpuscles located in dermis; yet closest to skin surface of any afferent
― Express Piezo2, coordinates urination
― Sensitive to low-frequency (3-40Hz) vibrations produced when textured objects brush against the skin

Question 4

Pacinian afferents

Answer 4

― Rapidly adapting fibers
― Comprise ~10-15% of the mechanosensory afferents in the hand
― Corpuscles located deep in dermis layer or in subcutaneous tissue
― Sensitive to vibrations transmitted through objects making contact with hand

Question 5

What is the difference between dorsal root ganglia and cranial nerve ganglia?

Answer 5

The afferent neurons that control the reflex
are sensory neurons whose cell bodies lie in the dorsal root ganglia and send axons peripherally that terminate in sensory endings in skeletal muscles. (The ganglia that serve this same function for much of the head and neck are called cranial nerve ganglia)

Question 5

Ruffini afferents

Answer 5

― Slowly adapting fibers
― Comprise ~20-25% of the mechanosensory afferents in the hand
― Corpuscles located in dermis
― Sensitive to skin stretching

Question 6

mechanotransduction

Answer 6

the process
of converting mechanical stimuli
(pressure, vibration) into electrical
signals

Question 7

mechanoreceptors specialised for proprioception

Answer 7

Golgi tendon organs,
muscle spindles, and joint receptors

Question 8

Muscle Spindles

Answer 8

-Location: Embedded within skeletal muscles.
-Function: Detect changes in muscle length and the rate of change in length (velocity). Essential for sensing muscle stretch and initiating the stretch reflex to maintain muscle tone.
-Structure: Composed of intrafusal muscle fibers and sensory nerve endings, particularly primary and secondary sensory endings.

Question 9

Golgi Tendon Organs

Answer 9

-Location: Found in tendons near the junction between muscles and tendons.
-Function: Respond to changes in muscle tension (force) and provide information about the force generated by muscle contraction. Activating the -Golgi tendon reflex helps prevent excessive force and potential muscle or tendon damage.
-Structure: Consists of nerve endings entwined among collagen fibers in the tendon.

Question 10

Joint Receptors

Answer 10

-Location: Situated in and around joint capsules.
-Function: Provide information about the position, movement, and force at the joints. -Contribute to the sense of joint position (proprioception) and movement (kinesthesia).
-Types: Include free nerve endings, Pacinian corpuscles, Ruffini endings, and others

Question 11

Cortical magnification

Answer 11

refers to the fact that the number of neurons in the visual cortex responsible for processing the visual stimulus of a given size varies as a function of the location of the stimulus in the visual field

Question 11

topographic organisation

Answer 11

refers to the arrangement of neural pathways in the nervous system in a spatially ordered manner that reflects the spatial relationships of the corresponding sensory or motor

Question 12

synaptic plasticity

Answer 12

the ability of neurons to modify their connections
Molecular Plasticity: Changes in molecules that alter the response / behaviour of a cell
Cellular Plasticity: Changes in the cell structure or shape that alters the response / behaviour of the cell
Systems Plasticity: Reorganization / regeneration of synaptic connections
Behavioral Plasticity: Altered behaviour, such as changes during habituation or sensitization

Question 13

Outer Ear

Answer 13

-Function: funnel for collecting and directing sound waves towards the middle ear the tragus, helix and the lobule
+Pinna (Auricle): The visible, external part of the ear. It helps in the collection of sound waves and assists in the localization of the source of the sound.
+Ear Canal (Auditory Canal): A tube-like structure that extends from the pinna to the eardrum. It channels sound waves from the external environment to the middle ear.

Question 14

Middle Ear

Answer 14

-Function: transmitting and amplifying sound vibrations from the outer ear to the inner ear. Key structures in the middle ear include:
Eardrum (Tympanic Membrane): A thin, membrane-like structure that vibrates in response to incoming sound waves. It marks the boundary between the outer and middle ear.
Ossicles (Malleus, Incus, Stapes): Three small bones (hammer, anvil, stirrup) that form a chain and transmit the vibrations from the eardrum to the inner ear. They act as a mechanical amplifier.

Question 15

Inner Ear

Answer 15

-Function: converting mechanical vibrations into electrical signals that can be interpreted by the brain.
-Cochlea: A spiral-shaped, fluid-filled structure that contains the sensory cells (hair cells) responsible for converting mechanical vibrations into electrical signals. Different regions of the cochlea are sensitive to different frequencies of sound.
-Vestibular System: This includes the vestibule and semicircular canals, which are responsible for detecting changes in head position and movement, contributing to the sense of balance and spatial orientation.

Question 16

tonotopy

Answer 16

the spatial arrangement of where sounds of different frequency are processed in the brain

Question 17

Hearing Loss: Causes and Treatments

Answer 17

-Major Causes: Acoustic trauma, chronic noise exposure, ototoxic drugs, presbyacusis.
Importance:
+Public awareness crucial.
+Developing therapies for normal hearing restoration is vital.

-Peripheral Auditory System Involvement:
+Most common forms involve the peripheral auditory system.
+Monaural hearing deficits are a key symptom.

-Types of Hearing Loss:
+Conductive: Outer or middle ear damage.
+Sensorineural: Inner ear or auditory nerve damage.

-Distinguishing and Treating:
+Weber test distinguishes between conductive and sensorineural.
+Treatment differs: hearing aids for conductive, challenging for profound sensorineural.

-Impact on Cochlear Hair Cells: Depletion diminishes sound detection; hair cells don’t regenerate.

Question 18

How does the bending of stereocilia lead to receptor potentials in hair cells?

Answer 18

When stereocilia, hair-like projections on inner ear hair cells, bend due to sound waves (auditory) or head movements (vestibular), mechanically gated ion channels open. This allows ions to enter, causing depolarization and generating a receptor potential. This potential triggers neurotransmitter release, activating nerve fibers that transmit signals to the brain, ultimately resulting in the perception of sound or the sense of balance and spatial orientation.

Question 19

Wernicke’s area

Answer 19

-Location: In the left hemisphere of the brain, traditionally in the posterior part of the superior temporal gyrus.
-Function: Associated with language comprehension and processing.
-Language Disorder: Damage to Wernicke’s area can result in Wernicke’s aphasia, characterized by difficulty understanding language and producing coherent speech

Question 20

What are the primary targets of auditory information after sensory transduction in the cochlear? Which target is involved in sound localisation?

Answer 20

-Primary Targets of Auditory Information:

+Cochlear Nucleus: Located in the brainstem, it receives input directly from the auditory nerve and is a crucial early processing site for auditory information.

+Superior Olivary Complex: Involved in processing interaural time differences and interaural level differences, important for sound localization.

-Target Involved in Sound Localization:
+Superior Olivary Complex: Particularly important for extracting spatial information from auditory cues and contributing to the brain’s ability to determine the direction of a sound source.

Question 21

Representing Complex Sounds in the Brains of Bats and Humans

Answer 21

Complexity of Natural Sounds:
-Majority are complex, tonal, or frequency-modulated (FM) sweeps.
-Harmonics contribute to timbre; nonharmonic frequencies may be present.
-Spectral splatter or broadband noise may be embedded.

Brain Representation:
-Cognitive studies show how a limited number of neurons represent diverse natural stimuli.
-Bats have specialized processing for complex sounds in the auditory cortex.
-Humans likely have multiple processing modes for different complex sounds.

Asymmetrical Representation:
-Common principle in complex sound processing.
Speech sounds lateralized to the left in the auditory cortex.
-Environmental sounds lateralized in the belt regions.

Modulation and Analysis:
-Variations in sound spectrum and amplitude envelope modulation.
-Spectrographic analysis visualizes complex sound features.

Functional Specialization in Bats: process communication and echolocation sounds within the same neurons. Evident specializations for complex sound processing.

Question 22

Deep Brain Stimulation

Answer 22

Treatment Options Before DBS:
-Limited to pharmacological intervention, physical therapy, and neurosurgical ablation.
-DBS introduced as an alternative to permanent brain structure destruction.

Implementation of DBS:
-Involves battery-powered generator units near clavicles.
-Subcutaneous wires connect to electrodes implanted bilaterally into the brain.
-Bilateral stimulation is necessary for symmetrical results.

Surgery and Stimulation Tuning:
-Stereotaxic surgery with radiological imaging and electrophysiological recordings.
-Neuronal recordings help recognize characteristic discharge patterns in basal ganglia and thalamus.
-Stimulation is tested post-implantation for desired clinical effects.

Common DBS Target Sites:
-Internal segment of the globus pallidus and the subthalamic nucleus.
-Targets abnormal neural activity in thalamus related to movement disorders.

Effects of DBS:
-Overrides pathological discharge patterns.
-Induces stable and structured neural activity for better initiation and termination of movement.

Mechanisms of DBS:
-Induces complex patterns of neural activity.
-May lead to the release of neurotransmitters and neuromodulators.
-Effects on intrinsic membrane properties may block action potential generation.

Applications and Hope:
-Used for various movement disorders and related conditions.
-Provides hope for individuals with neurological dysfunction.
-Adjustable stimulation protocols allow unprecedented manipulation of basal ganglia circuits.

Uncertainties and Expanding Applications:
-Ongoing uncertainties about mechanisms of action.
-DBS applied to disorders beyond movement, including Tourette syndrome, depression, and obsessive-compulsive disorder.

Question 23

dermatome

Answer 23

Sensation arising from a single dorsal root ganglion and its spinal nerve

Question 24

Optic flow

Answer 24

describes the characteristic distribution of local visual motion directions across the visual field

Question 24

pseudounipolar neurons

Answer 24

have one axon that splits into two branches – one branch goes to sensory periphery, the other goes to the CNS

Question 24

Afferent pathways from glabrous (hairless)
portions of the hand

Answer 24

responsible for generating a high-definition internal representation of manipulated objects.

Question 24

Active touching (haptics)

Answer 24

generates complex spatiotemporal patterns of stimulation that activate several types of mechanoreceptors

Question 25

stereognosis

Answer 25

the ability to perceive and recognize the form, size, and properties of an object solely through the sense of touch

Question 26

ventral posterior lateral nucleus (VPL)

Answer 26

receives somatosensory information from the body.

Question 27

ventral posterior medial nucleus (VPM)

Answer 27

receives information somatosensory information from the face.

Question 28

Cortical magnification

Answer 28

disproportionate representation of some body regions compared to others

Question 29

Otolith organs: utricle and saccule

Answer 29

• Detect static tilt and linear/translational head movements
• Otoconia: Calcium carbonate crystals in the ear’s otolithic membrane. When the head tilts, gravity shifts otoconia and the membrane relative to the macula. This movement displaces hair cell bundles => Generates receptor potentials in hair cells due to the displacement.

Question 30

The Organ of Corti

Answer 30

an organ of the inner ear located within the cochlea
* It includes three rows of outer hair cells and one row of inner hair cells.
* Vibrations caused by sound waves bend the stereocilia on these hair cells via an electromechanical force.

Question 31

Synaptic facilitation

Answer 31

rapid increase in synaptic strength that occurs when two or more action potentials invade the presynaptic terminal within a few milliseconds of each other

Question 32

Synaptic depression

Answer 32

decline of neurotransmitter release during sustained
synaptic activity => depletion of pool of synaptic vesicles that are available for release

Question 33

Synaptic augmentation and potentiation

Answer 33

augmentation and potentiation enhance the ability of incoming Ca2+ to trigger fusion of synaptic vesicles with the plasma membrane