Bio Review

Question 1

Primitive Streak

Answer 1

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

Question 2

Three germinal layers if the epiblast

Answer 2

• Endoderm: Innermost layer
• Mesoderm: Middle layer
• Ectoderm: Outer Layer

Nervous system is derived from the ectoderm

Question 3

Neurolation

Answer 3

formation of neural tubes = achieved at the end of the fourth week

Question 4

Neural Plate

Answer 4

• 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
  -

Question 5

Notochord

Answer 5

• Notochord: Appears in the third week of development
  
  • Secretes growth factors stimulating differentiation of the ectoderm = neuroectoderm = neural plate

Question 6

Neural crest

Answer 6

give rise to a diverse cell lineage = Carnio facial cartilage and smooth muscle

Question 7

Later development

Answer 7

• 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

Question 8

Synaptic pruning

Answer 8

allows damaged synapses to be eliminated

Question 9

Different vesicles

Answer 9

Question 10

Spinal Chord

Answer 10

Question 11

+/- Electroencephalography (EEG)

Answer 11

+ : High temporal resolution, non-invasive, cost-effective.
- : Poor spatial resolution, does not directly measure deep brain activity.

Question 12

+/- Magnetoencephalography (MEG)

Answer 12

+ : Excellent temporal resolution, good spatial resolution, non-invasive.
- : Expensive, requires specialized equipment, sensitive to interference.

Question 13

+/- Positron Emission Tomography (PET)

Answer 13

+ : Can detect metabolic and neurotransmitter activity, useful for studying disorders.
- : Exposure to radiation, expensive, lower temporal resolution.

Question 14

+/- Functional Magnetic Resonance Imaging (fMRI)

Answer 14

+ : High spatial resolution, non-invasive, good for functional studies.
- : Slower than EEG/MEG, can have difficulty distinguishing precise functions.

Question 15

+/- Magnetic Resonance Imaging (MRI)

Answer 15

+ : High-resolution anatomical details, non-invasive, no radiation exposure.
- : Cannot measure brain activity, requires the subject to remain still.

Question 16

+/- Computerized Tomography (CT)

Answer 16

+ : Quick, widely available, good for detecting structural abnormalities.
- : Involves radiation exposure, lower resolution than MRI.

Question 17

+/- Diffusion Tensor Imaging (DTI)

Answer 17

+ : useful for studying white matter pathways, high spatial resolution.
- : Limited to white matter pathways, does not measure neuronal activity.

Question 18

Cornea

Answer 18

• Function: The transparent, dome-shaped outer layer that helps to focus light onto the retina.
• Additional Role: Protects the eye from dust and microorganisms.

Question 19

Sclera

Answer 19

The white, protective outer layer of the eye that maintains its shape and provides attachment points for eye muscles.

Question 20

Pupil

Answer 20

A circular opening in the center of the iris that controls the amount of light entering the eye.

Question 20

Iris

Answer 20

The coloured part of the eye that contains muscles to adjust the size of the pupil, regulating light entry.

Question 21

Conjunctiva

Answer 21

A thin, transparent membrane covering the sclera and inner eyelids that lubricates and protects the eye.

Question 22

Lens

Answer 22

A transparent, flexible structure that focuses light onto the retina by changing its shape (accommodation).

Question 23

Retina

Answer 23

The inner layer of the eye that contains photoreceptor cells (rods and cones) which convert light into electrical signals.

Question 23

Ciliary Muscles

Answer 23

Adjust the shape of the lens for near or distant vision.

Question 24

Fovea

Answer 24

A small central pit in the retina that contains a high concentration of cones, responsible for sharp, detailed vision.

Question 25

Optic Disc (Blind Spot)

Answer 25

The point where the optic nerve exits the eye; lacks photoreceptors, creating a blind spot.

Question 26

Rods

Answer 26

Photoreceptors that detect low light levels (night vision) but do not perceive color.

Question 27

Cones

Answer 27

Photoreceptors responsible for colour vision and sharp central vision, mainly concentrated in the fovea.

Question 28

Bipolar Cells

Answer 28

Intermediate neurons that transmit signals from photoreceptors to ganglion cells.

Question 29

Ganglion Cells

Answer 29

Receive input from bipolar cells and send signals through their axons to form the optic nerve.

Question 30

Horizontal and Amacrine Cells

Answer 30

Help process and integrate visual signals by modulating input from photoreceptors and bipolar cells.

Question 31

Myopia

Answer 31

= 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.

Question 32

Hyperopia

Answer 32

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.

Question 33

Astigmatism

Answer 33

- 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.

Question 34

Presbyopia

Answer 34

= 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.

Question 35

Brain Parts Involved with vision

Answer 35

Question 36

Electrical Transition in the brain for hearing

Answer 36

Question 36

Electrical Transduction in the Cochlea

Answer 36

- 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.

Question 37

Explicit (Declarative) Memory

Answer 37

Requires conscious recall 2 Types - Episodic Memory: Personal experiences - Semantic Memory: General knowledge and facts

Question 38

Implicit (Non-Declarative) Memory

Answer 38

Does not require conscious awareness. 2 Types - Procedural Memory: Motor skills and habits - Priming: Exposure to a stimulus influences responses

Question 39

Short-Term vs. Long-Term Memory

Answer 39

- Short-term memory holds limited information temporarily. - Long-term memory stores information for extended periods, strengthened by consolidation.

Question 40

Working Memory

Answer 40

Short-term, active processing of information (e.g., solving a math problem in your head)

Question 41

Hippocampus in Memory

Answer 41

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.

Question 42

Striatum in Memory

Answer 42

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.

Question 43

Cholinesterase Inhibitors (Cognitive Symptom Management)

Answer 43

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.

Question 44

NMDA Receptor Antagonists (Excitotoxicity Control)

Answer 44

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.

Question 45

Disease-Modifying Immunotherapies (Beta-Amyloid Removal)

Answer 45

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).

Question 46

Dopaminergic Therapy (Primary Treatment for PD)

Answer 46

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.

Question 47

MAO-B Inhibitors

Answer 47

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.

Question 48

NMDA Receptor Antagonists

Answer 48

Function: - Helps control dyskinesia (involuntary movements) caused by long-term L-DOPA use. Example: - Amantadine – Also has mild dopamine-enhancing effects.

Question 49

First-Generation Medications

Answer 49

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.

Question 50

Second-Generation Medications

Answer 50

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.

Question 51

Meninges