Physio - Exam 3 Flashcards
3 Perspectives on Brain Development
- As the brain develops, new behavior emerges.
- Emerging circuitry predicts behavioral development.
- Research investigates how language, injury, socioeconomic status impact brain structure & behavioral development.
Neurobiology of Development
Early development: all vertebrates appear similar.
Human embryos (day 28): forebrain, midbrain, hindbrain are visible.
Gross Development of the Nervous System
Day 15 Post-Fertilization: developing embryo takes shape. - Multiple cell layers.
- Embryonic Disc: Raised central area; the primitive body.
Neural Plate
The thickened region of the ectodermal layer that forms the neural tube.
Neural Groove
Shallow median groove found in the neural plate of an embryo.
Neural Tube
Structure in the early stage of brain development from which the brain and spinal cord develop.
How Do Stem Cells Know What to Become?
Stem cells receive instructions through molecular chats & epigenetic signals.
- Guide stem cells to transform into specific
cell types
- Their adaptability ensures our bodies can
grow, heal, and regenerate.
Neural Stem Cells
Self-renewing cells, that creates neurons & glia, lines the neural tube. When stem cells divide, it creates 2 stem cells. This stem cell process repeats all throughout life
- one that dies
- the other that lives to divide again
Subventricular Zone
Lining of neural stem cells surrounding the ventricles in adults.
Progenitor Cells
A precursor cell, originating from a stem cell, migrates and gives rise to either a neuron or a glial cell. It produces nondividing cells called neuroblasts and glioblasts.
Neuroblasts
Product of a progenitor cell that gives rise to different types of neurons.
Glioblasts
Product of a progenitor cell that gives rise to different types of glial cells.
Neurotrophic Factors
A chemical compound that promotes growth and differentiation in developing neurons and may also contribute to the survival of specific neurons in adulthood.
Growth & Development of Neurons
The human brain needs around 10 billion cells to create the cortex covering one hemisphere.
During peak prenatal brain development….
- Generates about 250,000 neurons per
minute.
- The brain prunes unnecessary cells and
connections.
- Adapting to an individual’s
experiences and requirements.
Cell Birth
Age 7 Weeks Post-Conception: A chemical compound aids the growth & specialization of developing neurons.
@ 5 months: this process is mostly finished; the hippocampus keeps producing new cells throughout life.
Initial 5 months of Pregnancy: the brain is better at handling injuries.
Cell Migration
Neurogenesis begins after the first neurons form. It lasts 6 weeks in the cortex and continues throughout life in the hippocampus. Damage during this process can be severe. Radial glial cells guide migrating neurons to their proper destinations.
Cell Differentiation
Neuroblasts transform into specific types of neurons post-cell migration & is mostly completed at birth. This process, also, continues for years in certain brain regions.
Cell Maturation
After neurons reach their destinations and differentiate into specific types, they mature in two ways:
1. Dendritic Growth: Neurons grow dendrites, increasing surface area for synapses with other cells.
2. Axonal Growth: - Neurons extend axons to appropriate targets, initiating synapse formation.
Synaptogenesis
Fully grown cerebral cortex, 1000s of synapses form through a genetic programming & environmental cue.
- 5th Gestational Month: simple synaptic contacts emerge.
- 7th Gestational Month: deep cortical neurons undergo synaptic development.
- After Birth: synaptic development accelerates rapidly during the first year of life.
Cell Death
The brain shapes itself by removing cells through cell death and synaptic pruning.
- Influenced by genetic signals, experience,
reproductive hormones, and stress.
- The cortex becomes thinner, following a back-
to-front gradient.
- Likely due to ongoing synaptic pruning.
Myelogenesis
Astrocyte and oligodendrocyte development occurs post-neurogenesis and persists lifelong, with oligodendroglia generating CNS myelin, serving as a cerebral maturation indicator.
Correlation with Behavior & Brain (Motor Development)
- Motor cortex neuron axons undergo myelination around the same time that the abilities to reach and grasp develop.
- Neurons in the motor cortex that regulate finger movements begin myelination when the pincer grasp skill starts to develop.
- Improved hand coordination in right-handed people is linked to thinner left motor cortex areas controlling the hand.
Correlation with Behavior & Brain (Language Development)
- Language development typically starts between 1 and 2 years of age.
- Most language acquisition is completed by age 12.
- Key neural changes during this period include:
- Increased dendritic complexity
- Enhanced interconnections
- Greater myelination in speech areas - Language development is not solely dependent on motor skills.
- Cell growth in language-specific brain regions is complete by age 2.
- From ages 2 to 12, the focus shifts to neuronal connectivity and myelination.
- Broca’s area undergoes significant axonal and dendritic growth between 15 to 24 months.
- This growth correlates with a rapid increase in vocabulary around age 2.
Correlation with Behavior & Brain (Cognitive Development)
- Children’s exploration and problem-solving evolve with cognitive growth.
- Brain development spurts, featuring more glial cells, blood vessels, myelin, and synapses.
- These growth spurts match Piaget’s stages, peaking at 14 to 16 years.
- Enable learning abilities like discrimination tasks at 12 months and memory tasks at 18 months.
- Reflects maturation of neural structures.
Piaget’s Stage’s of Cognitive Development
Age Range: 0 – 2 YearsDescription: Sensorimotor: Experiences the world through senses and actions (looking, touching, mouthing)
Developmental Phenomenon: Object permanence, Stranger anxiety
Age Range: 2 – 6 Years
Description: Preoperational: Represents things with words & images but lacks logical reasoning
Developmental Phenomenon: Pretend Play, Egocentrism, Language Development
Age Range: 7 – 11 Years
Description: Concrete operational | Thinks logically about concrete events; grasps concrete analogies and performs arithmetical operations
Developmental Phenomenon: Conservation, Mathematical transformations
Age Range: 12+ Years
Description: Formal operational: Reasons abstractly
Developmental Phenomenon: Abstract logic, Potential for mature moral reasoning
Brain Development & the Environment
The brain adapts to diverse environments, influenced by culture.
These cultural differences may lead to lifelong behavioral variations due to brain structure.
Cognitively stimulating environments enhance intellectual development, while enriched environments boost synapses and astrocytes.
Brain Development & the Environment (Enrichment)
Neurons (with the influence of a complex environment) are larger & richer in synapses & astrocytes.
Critical Periods
Developmental window where certain events have a long-lasting influence on the brain “sensitive period” (ex. Imprinting)
Sensory Receptors
Specialized cells transform sensory energy (such as light) into neural activity, and each sensory system’s receptors are finely tuned to respond to a specific energy range.
Receptive Fields
A receptive field is the specific area in the world to which a sensory receptor responds. In the case of photoreceptor neurons, each one has its own unique receptive field that partly overlaps with neighboring fields.
Optic Flow
Stream of visual stimuli that accompanies an observer’s forward movement through space.
Auditory Flow
Change in sound heard as a person and a sound source pass each other.
Receptor Density
Density is important for determining the sensitivity of a sensory system and determines the special abilities of many animals.
Neural Relays
Receptors connect to the cortex through a chain of 3 - 4 intervening neurons with no direct, one-to-one link between each neural relay.
How Do Action Potentials Encode Features of Particular Sensations?
Action potentials carry sensory information from our body’s nerve to the brain. Different sensations have specific pathways in the brain.
How Do Action Potentials Code the Different Kinds of Sensations?
Distinct pathways in different areas of the cortex handle various sensations.
Sensation vs. Perception
Our brain receives input from the world as action potentials along sensory pathways.
- We understand how nerves converting energy into nerve impulses and the pathways they take
- The process of this conversion is less understood
Range of Human Vision
Our central vision is sharper than our peripheral vision. When we focus on the center, letters at the edges need to be significantly larger for us to see them clearly.
Cone / Color Pigments (Shortest to Longest)
Functional Anatomy of the Eye
Vision is our dominant sensory experience.
The brain devotes more resources to vision than any other sense.
Retina
Where light energy initiates neural activity
Cornea
Clear outer covering
Iris
The iris opens and closes to regulate the amount of light entering the eye. The pupil is the actual hole in the iris.
Lens
The lens focuses light & adjusts to accommodate objects at varying distances.
Lens
(Myopia)
Nearsightedness.
Focal point of light falls short of the retina.
Lens
(Hyperopia)
Farsightedness.
Focal point of light falls beyond the retina.
Fovea
specialized for high visual acuity.
Corresponds to the receptive field at the center of the eye’s visual field.
Blind Spot
Located in the retina at the optic disc.
Axons forming the optic nerve exit the eye.
entry/exit point for blood vessels.
Lacks photoreceptors.
Papilledema
When the optic disc swells.
- due to increased intracranial pressure (tumor/brain infection) or inflammation of the optic nerve.
- Can result in vision loss.
Photo Receptors
(Rods)
Outnumber cones.
Sensitive to dim light.
Responsible for night vision.
Only 1 type of pigment.
Photo Receptors
(Cones)
Highly responsive to bright light.
specialize in color vision & high visual acuity.
Found exclusively in the fovea.
Comes in 3 types, each with a different pigment.
Bipolar Cells
Receives input from photoreceptors.
Horizontal Cells
Links photoreceptors & bipolar cells.
Amacrine Cells
Links bipolar cells & ganglion cells.
Retinal Ganglion Cells
Gives rise to the optic nerve.
Retinal Ganglion Cells
(Magnocellular Cells)
Large.
Receives input from rods.
Sensitive to light / movement.
Retinal Ganglion Cells
(Parvocellular Cells)
Small.
Receives input from cones.
Sensitive to color.
Visual Field Processing
Information from the left visual field is processed in the right side of the brain.
Information from the right visual field is processed in the left side of the brain.
Optic Chiasm
Intersection of optic nerves from each eye.
Axons from the inner (nasal) half of each retina cross over to the opposite side of the brain.
Axons from the outer (temporal) half of each retina remain on the same side of the brain.
Geniculostriate System
Signals travel from the retina to the lateral geniculate nucleus and then to the visual cortex.
Geniculostriate System
(Dorsal Visual Stream)
This pathway starts in the occipital cortex & extends to the parietal cortex. It’s known as the ‘how pathway,’ as it guides actions toward objects.
Geniculostriate System
(Ventral Visual Stream)
The ‘what pathway’ originates in the occipital cortex and extends to the temporal cortex. Its primary function is to identify objects
Tectopulvinar System
Magnocellular cells from the retina project to the superior colliculus (sends info to the pulvinar “thalamus”)
Provides info regarding location.
Medial Pulvinar
Sends connections to the parietal lobe.
Lateral Pulvinar
sends connections to the temporal lobe
Retinohypothalamic Tract
Regulates circadian rhythm & pupillary reflex.
V1
Striate Cortex
Primary Visual Cortex
Receives input from lateral geniculate nucleus.
Striate Cortex
Where visual processing begins
Helps us perceive the world by analyzing visual input from our eyes.
Blobs
(V1)
The visual cortex contains neurons sensitive to color.
Interblobs
(V1)
Separates blobs.
Perception of form & motion.
Thick Strips
(V2)
Receives info from movement-sensitive neurons.
Thin Strips
(V2)
Receives info from color-sensitive neurons.
Pale Zones (V2)
Receives info from form sensitive neurons.
Visual Corpus Callosum
connects specific structures of the 2 hemispheres.
Frontal: mostly connected
Occipital: minimal corpus callosum
Exception: allow receptive fields to overlap.
Agnosia
Visual: inability to recognize objects/drawings of objects.
Color: inability to recognize color.
Face: inability to recognize faces.
Optic Ataxia
