The Human Eye

• The basic parts of the human eye are: Cornea, sclera, iris, pupil, lens, ligament, retina, optic nerves, fovea, and blind spot

• Light passes through the eye structures in the following order: Cornea, pupil, lens, retina, optic nerve

• The fovea is located in the center of the retina

• The fovea's function is to provide high-acuity vision, giving the most clear and detailed view of focused objects

• The optic nerve consists of axons of retinal ganglion cells

• The optic nerve creates a blind spot because it exits the retina which creates a small region where light cannot be detected due to a lack of photoreceptors

• The Purkinje Effect is a phenomenon where the relative brightness of colors changes as light levels decrease

• Blues appear brighter in dim light conditions

• In intense light, red and yellow wavelengths look brighter than blue or green wavelengths of equal intensity

• In dim light, blue and green wavelengths look brighter than red and yellow wavelengths of equal intensity

• Electrical pulses induced by sound go to the hindbrain before interacting with the thalamus

• The thalamus relays the signal to the primary auditory cortex

• The medial geniculate nucleus is the nuclei of the thalamus that sends fibers to the primary auditory cortex

• Types of Cutaneous Receptors:

  • Free nerve endings → pain and temperature
  • Pacinian corpuscles → deep, fast-adapting touch
  • Merkel receptors → slow-adapting, gradual skin indentation
  • Ruffini corpuscles → slow-adapting touch for skin stretch

• The cingulate cortex plays a role in the emotional response to pain

• The cingulate cortex contributes to processing painful sensations and how we react to them

• The thermal grid illusion creates feelings of pain without actual harm

• Thermal grid illusion increases the activity in the cingulate cortex, further proves the cortex is involved in processing sensation of pain

• The periaqueductal gray (PAG) is a descending analgesia circuit, that controls pain

• The descending pain control pathway activates serotonergic neurons

• Serotonergic neurons send signals down the spinal cord, which excite interneurons in the dorsal horn, blocking incoming pain signals and resulting in pain relief

• The gustatory system recognizes five primary tastes: umami, sweet, bitter, salty, and sour

  • Metabotropic receptors activated by umami, sweet, and bitter tastes
  • Ionotropic receptors activated by salty and sour tastes

• Primary sensory cortex is one of the areas of the neocortex that receives direct input from thalamic relay nuclei

• Relay nuclei mostly projects from the primary cortex

• Three Principles of Sensorimotor Function:

  • Hierarchy of control
  • Motor output is guided by sensory input
  • Learning changes nature and locus of sensorimotor control, this relates to automaticity

• Learning/practicing allows performance without thinking

• The posterior parietal association cortex provides information on body part locations and receives input from visual, auditory, and somatosensory systems

• The Somatosensory system deals with sensory processing and perception

• Sensorimotor systems focuses on motor control

• The posterior parietal association cortex helps the brain plan, execute, and refine movements

• Lesions to the right parietal lobe can result in contralateral neglect

• Mrs. S., who had pastier damage to her cotex, had very large right parietal lesions and learned that if she turned her chair, she would be able to eat her food to get the right nutrients

• Associative, secondary, and primary are hierarchical areas of the brain that premotor cortex, supplemental motor areas, and cingulate motor areas can be found in

• Secondary motor cortex

• Mirror neurons encode for particular goal objects and require a purpose for action

• Mirror neurons fire when an individual makes goal-directed movements and when an individual observes like movements from another

• Definitions:

  • Stereognosis is the process of identifying objects by touch
  • Astereognosia is an inability to recognize objects by touch that is not attributable to a simple sensory deficit or intellectual impairment

• The cerebellum integrates and coordinates activity in the sensorimotor system and contains over half of the brains neurons

• The cerebellum contributes to 10% of the brains total mas

• Signals from the primary motor cortex transit via 4 different pathways, 2 in the dorsolateral corticospinal tract and 2 in the ventromedial corticospinal tract

• Distal limb muscles controlled by signals via dorsolateral tract of the spinal cord

• Trunk and proximal limb muscles controlled by signals via ventromedial tract of the spinal cord

• Lawrence and Kuypers experiment:

  • Dorsolateral tract transactions: Monkeys could stand, walk, and climb but arms hung limply and they could still reach for small objects
  • Ventromedial tract transactions: Monkeys had a difficult time walking or sitting; they would fall with the smallest disturbance

• Isometric muscle contraction increases the force of a muscles pull but does not shorten the muscles with no action at the joint

• Dynamic muscle contraction causes the muscle to shorten with action at a joint

• Types of Embryonic Stem Cells:

  • Totipotent: Can develop into any type of cell
  • Pluripotent: Can develop into many, but not all, types of cells
  • Multipotent: Can develop into different cells of only one class

• Phases of Neurodevelopment:

  • Induction of the neural plate
  • Neural proliferation
  • Migration and aggregation
  • Axon growth and synapse formation
  • Neuron death and synapse rearrangement

• The neural plate develops into the neural tube

• The neural groove develops into the neural tube

• The inside of the neural tube becomes the cerebral ventricles and spinal canal

• Developing neurons proliferate, migrate, aggregate, and cell adhesion molecules (CAMs) recognize other cells and adhere to them allowing this to happen

• A growth cone is an amoebalike structure at the growing tip of axons and dendrites, guides growth to the appropriate target

• As cells grow in development up to 50% die during the course of normal development

• Necrosis is a passive cell death process where cells break apart, spilling their contents into the extracellular fluid

• Apoptosis is an active cell death – where the internal cell structures are cleaved and packaged in membranes before the cell breaks apart

• Apoptosis is a safer process that does not result in inflammation

• Necrosis results in inflammation.

• The prefrontal cortex is the part of the brain that reaches full maturity last

• Perseverative errors are damage in the prefrontal cortex which lead to repetitive behavior

• Prefrontal cortex is responsible for higher cognitive functions and knowing an object exists even if hidded

• Critical period refers to a crucial time for experience to occur at a specific time

• Sensitive period refers to when experience has an effect outside of the specific time or interval

• The vast majority of experiential effects on neurodevelopment occur during the sensitive period

• Neurogenesis occurs mostly on the Hippocampus

• The two core symptoms of autism spectrum disorder (ASD) are:

  • Reduced capacity for social interaction
  • Restricted and repetitive patterns of behavior

• Brain tumors is a term given when a group of cells grow independently from the rest of the body

• Benign tumors have a low spread risk

• Malignant tumors have a high spread risk

• Encapsulated tumors grow within their own membrane and are benign

• Infiltrating tumors grow diffusely through surrounding tissue and are malignant

• Encapsulated tumors like meningiomas grow in the meninges

• Infiltrating tumors like gliomas originate from glial cells

• Strokes result from cerebral hemorrhage or cerebral ischemia

• Ischemic strokes often induce brain damage via excitotoxicity through excess glutamate release

• Contrecoup contusion is an injury including bleeding without laceration, caused by the brain hitting the skull

• Encephalitis is inflammation in the brain resulting from infection

• Neurotoxins can induce toxic psychosis

• Mercury led to the term Mad hatter

• Lead led to the term Crackpots

• Epilepsy can induce tonic-clonic seizures

• Tonic portion involves rigidity of the muscles

  • Clonic portion involves jerking movements

• Alzheimer's diseases are neuropathological changes

• The loss of neurons is associated with the aberrant folding of tau proteins and amyloid beta proteins

• Amyloid plaques and neurofibrillary tangles lead to neuron loss

• Anterograde degeneration: Degeneration occuring in the distal segment of a cut axon

  • Retrograde degenration: Degeneration occuring in the proximal segment of a cut axon

• Transneuronal degeneration leads to the spread of neurodegeneration as damage spreads to connected neurons

Collateral sprouting is the regeneration in the CNS that facilitates formation of new connections that compensate for lost neurons by surviving neurons

• The axons of retinal ganglion cells are found in large numbers at the blind spot of each eye

• The bleaching of rhodopsin by light produces hyperpolarizing rods

• The axons of the olfactory receptors run through the cribriform plate to the olfactory bulbs

• Pupil-lens-fovea-optic nerve is the pathway that light travels through the eye from the external world of the brain

• Taste transduction for sweet, umami, and bitter is mediated by metabotropic receptors and ionotropic receptors

• The primary somatosensory cortex is organized in four somatotopically organized, parallel strips

• Pacinian corpuscles, merkel's disks, and ruffini endings are receptors in the skin

• Modern neuroscientific theory considers sensory systems to be hierarchical, functionally segregated, and parallel

• The Purkinje effect refers to the fact that light in the blue-green portion of the spectrum are brighter than equally intense lights in the yellow-red portion of the spectrum when viewed under dim illumination

• The identification of objects by touch is Stereognosis

• A small indentation found in the eyes is the Fovea

• As sound makes its way from the ear to the auditory cortex the medial geniculate nuclei can be found in Thalamus

• Electrical stimulation of the periaqueductal gray produces a(n) Analgesic effect

• Areas of the neocortex that receive most of their input from the thalamic relay nuclei of one sensory system are classified as a Primary sensory cortex

• Light enters the human eye through an opening in the is called the Pupil

• The dorsal column medial-lemniscus system and the anterolateral system both carry sensory information from the Skin

• The external stimuli to the skin is apart of the somatosensory system which is exteroceptive

• The cortical area most commonly linked to the perception of pain is called the Anterior cingulate cortex

• An area of the cerebral cortex that receives substantial input from more than one sensory system is classified as the Association cortex

• Harold's Klawans neurological case of Aunt Betty suffered from Asomatognosia

• The loudness, pitch, and timbre of a sound are directly related to the amplitude, frequency and complexity respectively of the vibrations that produced it

• In comparison to the photopic system, the scotopic system has more receptors in the periphery of the retina

• Nociceptive stimuli are Painful

• With respect to the visual system, a high degree of neural convergence is to a low degree of neural convergence as Low acuity is to high acuity

• Saccades are Eye movements