Bio Review Flashcards
Primitive Streak
Structure that appears as a groove into the epiblast layer of the bilaminar disk
- Cells within the epiblast disk migarte downwards through the primitive strek giving rise to the three layers
Three germinal layers if the epiblast
- Endoderm: Innermost layer
- Mesoderm: Middle layer
- Ectoderm: Outer Layer
Nervous system is derived from the ectoderm
Neurolation
formation of neural tubes = achieved at the end of the fourth week
Neural Plate
- Rises to form neural folds towards each other forming the neural tube
- During fusion some cells in the neural fold form a distinct cell population = neural crest
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Notochord
- Notochord: Appears in the third week of development
- Secretes growth factors stimulating differentiation of the ectoderm = neuroectoderm = neural plate
Neural crest
give rise to a diverse cell lineage = Carnio facial cartilage and smooth muscle
Later development
- 5th week sweeling appears at the cranial end of the neural tube
- This forms three primitive vesicles = developing into 5 secondary vesicles
- vesicles will give rise to all the brain structures and cerebellum
Synaptic pruning
allows damaged synapses to be eliminated
Different vesicles
Spinal Chord
+/- Electroencephalography (EEG)
+ : High temporal resolution, non-invasive, cost-effective.
- : Poor spatial resolution, does not directly measure deep brain activity.
+/- Magnetoencephalography (MEG)
+ : Excellent temporal resolution, good spatial resolution, non-invasive.
- : Expensive, requires specialized equipment, sensitive to interference.
+/- Positron Emission Tomography (PET)
+ : Can detect metabolic and neurotransmitter activity, useful for studying disorders.
- : Exposure to radiation, expensive, lower temporal resolution.
+/- Functional Magnetic Resonance Imaging (fMRI)
+ : High spatial resolution, non-invasive, good for functional studies.
- : Slower than EEG/MEG, can have difficulty distinguishing precise functions.
+/- Magnetic Resonance Imaging (MRI)
+ : High-resolution anatomical details, non-invasive, no radiation exposure.
- : Cannot measure brain activity, requires the subject to remain still.
+/- Computerized Tomography (CT)
+ : Quick, widely available, good for detecting structural abnormalities.
- : Involves radiation exposure, lower resolution than MRI.
+/- Diffusion Tensor Imaging (DTI)
+ : useful for studying white matter pathways, high spatial resolution.
- : Limited to white matter pathways, does not measure neuronal activity.
Cornea
- Function: The transparent, dome-shaped outer layer that helps to focus light onto the retina.
- Additional Role: Protects the eye from dust and microorganisms.
Sclera
The white, protective outer layer of the eye that maintains its shape and provides attachment points for eye muscles.
Pupil
A circular opening in the center of the iris that controls the amount of light entering the eye.
Iris
The coloured part of the eye that contains muscles to adjust the size of the pupil, regulating light entry.
Conjunctiva
A thin, transparent membrane covering the sclera and inner eyelids that lubricates and protects the eye.
Lens
A transparent, flexible structure that focuses light onto the retina by changing its shape (accommodation).
Retina
The inner layer of the eye that contains photoreceptor cells (rods and cones) which convert light into electrical signals.
Ciliary Muscles
Adjust the shape of the lens for near or distant vision.
Fovea
A small central pit in the retina that contains a high concentration of cones, responsible for sharp, detailed vision.
Optic Disc (Blind Spot)
The point where the optic nerve exits the eye; lacks photoreceptors, creating a blind spot.
Rods
Photoreceptors that detect low light levels (night vision) but do not perceive color.
Cones
Photoreceptors responsible for colour vision and sharp central vision, mainly concentrated in the fovea.
Bipolar Cells
Intermediate neurons that transmit signals from photoreceptors to ganglion cells.
Ganglion Cells
Receive input from bipolar cells and send signals through their axons to form the optic nerve.
Horizontal and Amacrine Cells
Help process and integrate visual signals by modulating input from photoreceptors and bipolar cells.
Myopia
= Nearsightedness
- Cause: The eyeball is too long or the cornea is too curved, causing light to focus in front of the retina instead of directly on it.
- Symptoms: Blurry distance vision, squinting, eye strain, headaches.
- Treatment: Glasses, contact lenses, LASIK surgery.
Hyperopia
Farsightedness
- Cause: The eyeball is too short or the cornea is too flat, causing light to focus behind the retina.
- Symptoms: Difficulty seeing close objects, eye strain, headaches.
- Treatment: Glasses, contact lenses, or surgery.
Astigmatism
- Cause: The cornea or lens is irregularly shaped, causing light to focus at multiple points instead of one.
- Symptoms: Blurry vision at all distances, eye strain, headaches.
- Treatment: Glasses, contact lenses, LASIK.
Presbyopia
= Age-Related Farsightedness
- Cause: The lens loses elasticity with age, reducing the ability to focus on close objects.
- Symptoms: Difficulty reading or seeing close objects, needing more light.
- Treatment: Reading glasses, bifocals, multifocal lenses.
Brain Parts Involved with vision
Electrical Transition in the brain for hearing
Electrical Transduction in the Cochlea
- Sound Wave Detection: Sound waves enter the cochlea and cause movement in the basilar membrane, which vibrates in response to different frequencies.
- Stereocilia Bending: The movement of the basilar membrane displaces the hair cells in the organ of Corti, causing their stereocilia to bend.
- Ion Channel Activation: When the stereocilia bend toward the kinocilium, mechanically gated ion channels open, allowing potassium (K⁺) ions to enter the hair cells from the surrounding endolymph.
- Depolarization and Neurotransmitter Release: The influx of K⁺ ions leads to depolarization of the hair cells, which opens voltage-gated calcium (Ca²⁺) channels. Calcium influx triggers the release of the neurotransmitter glutamate.
- Signal Transmission: Glutamate binds to receptors on the auditory nerve fibers, generating an action potential that travels through the cochlear nerve to the brainstem and eventually to the auditory cortex, where sound is processed.
Explicit (Declarative) Memory
Requires conscious recall
2 Types
- Episodic Memory: Personal experiences
- Semantic Memory: General knowledge and facts
Implicit (Non-Declarative) Memory
Does not require conscious awareness.
2 Types
- Procedural Memory: Motor skills and habits
- Priming: Exposure to a stimulus influences responses
Short-Term vs. Long-Term Memory
- Short-term memory holds limited information temporarily.
- Long-term memory stores information for extended periods, strengthened by consolidation.
Working Memory
Short-term, active processing of information (e.g., solving a math problem in your head)
Hippocampus in Memory
Critical for declarative memory (explicit memory), including episodic memory (personal experiences) and semantic memory (facts and knowledge). It is essential for spatial navigation and memory consolidation—transferring short-term memories to long-term storage.
Striatum in Memory
Part of the basal ganglia, mainly involved in procedural memory and habit formation. It plays a key role in implicit learning, particularly in skills and motor-based tasks, such as riding a bike or playing an instrument.
Cholinesterase Inhibitors (Cognitive Symptom Management)
Function:
- Prevent the breakdown of acetylcholine, improving memory and cognitive function.
Examples:
- Donepezil (Aricept) – Used for mild to severe AD.
- Rivastigmine (Exelon) – Available in patch or oral form, also used in Parkinson’s dementia.
- Galantamine (Razadyne) – Enhances nicotinic receptors, improving acetylcholine function.
Limitations:
- Provides temporary cognitive improvement, but does not stop disease progression.
- Common side effects: Nausea, diarrhea, dizziness, falls.
NMDA Receptor Antagonists (Excitotoxicity Control)
Function:
- Blocks excessive glutamate activity, which can lead to neuron damage.
- Helps in moderate to severe AD, particularly in maintaining basic functions.
Example:
- Memantine (Namenda) – Used in moderate to severe AD.
Side effects:
- Dizziness, confusion, headache, constipation.
Disease-Modifying Immunotherapies (Beta-Amyloid Removal)
Function:
- Helps remove amyloid-beta plaques, targeting the root cause of AD.
- Aimed at slowing down progression, but benefits are limited to early-stage AD.
Examples:
- Lecanemab (Leqembi) – FDA-approved immunotherapy that reduces amyloid plaques.
- Donanemab – Another monoclonal antibody therapy under study.
Limitations:
- Only effective in early AD.
- Can cause brain swelling (amyloid-related imaging abnormalities, ARIA).
Dopaminergic Therapy (Primary Treatment for PD)
Function:
- Replaces or mimics dopamine, which is deficient in PD.
Examples:
- Levodopa (L-DOPA) + Carbidopa (Sinemet)
- Levodopa converts into dopamine in the brain.
- Carbidopa prevents L-DOPA breakdown before it reaches the brain.
- Most effective for motor symptoms but can cause dyskinesia (involuntary movements) over time.
Dopamine Agonists (Pramipexole, Ropinirole, Rotigotine (patch))
- Mimic dopamine at dopamine receptors.
- Used in early PD or alongside L-DOPA.
- Side effects: Hallucinations, drowsiness, impulse control issues.
MAO-B Inhibitors
Function:
- Blocks monoamine oxidase-B (MAO-B), an enzyme that breaks down dopamine.
- Extends the effects of dopamine therapy.
Examples:
- Selegiline (Eldepryl)
- Rasagiline (Azilect)
Side effects:
- Insomnia, nausea, increased blood pressure with certain foods.
NMDA Receptor Antagonists
Function:
- Helps control dyskinesia (involuntary movements) caused by long-term L-DOPA use.
Example:
- Amantadine – Also has mild dopamine-enhancing effects.
First-Generation Medications
Characteristics:
- Developed earlier, usually the first type of drug used for a condition.
- Often have stronger effects but also more severe side effects.
- Tend to have a narrower mechanism of action, affecting one neurotransmitter system.
- Commonly cause extrapyramidal side effects (movement disorders), sedation, and other adverse reactions.
Second-Generation Medications
Characteristics:
- More recently developed with improved safety and effectiveness.
- Broader mechanisms of action, affecting multiple neurotransmitter systems.
- Designed to reduce side effects like movement disorders seen in first-generation drugs.
- Typically have lower risks of extrapyramidal side effects.
Meninges
