Put everything in, fix later merge plz

Grade 10/Science/SNC2DZ/Unit 2: Biology.md

@@ -1,6 +1,5 @@
 # Unit 2: Biology
 
-## Cellular Biology
 A person contains roughly 100 trillion cells
 - Cells are roughly 20 `μm` (micrometre, 10<sup>-6</sup> m), around 250 cells / cm
 
@@ -22,22 +21,7 @@ A person contains roughly 100 trillion cells
 |Organization|Usually singlecelled|Often form multicellular organisms|
 |Metabolism|May not need oxygen|Usually need oxygen|
 
-## Cellular Organelles
+## Organelles
-
-### Business Analogy
-
-| In a business | In a cell | 
-| ------------- | --------- |
-| Building      | Cytoplasm & Cytoskeleton |
-| Department Head | Organelles |
-| Boss          | DNA |
-| Workers       | Ribosomes & Enzymes |
-| Waste management | Lysosomes |
-| Storage       | Vacuoles | 
-| Powerhouse    | Chloroplasts & Mitochondria |
-| Security gate | Cell membrane controls entrance and exit from the cell |
-| Transportation Department | IMPORT: Cell membranes and vesicles, INTERNAL: Endoplasmic reticulum & vesicles, EXPORT: Golgi apparatus, vesicles, and cell membrane |
-
 
 ### Cell Membrane
 - Controls what substances **enter/leave** the cell selectively via various receptors/osmosis
@@ -226,11 +210,11 @@ A person contains roughly 100 trillion cells
 - `Zygote`: A single-celled organism formed from the fertilization of an egg by a sperm cell, is a totipotent stem cell
 - A cell's position in the `gastrula` (outer, middle, inner layer) will determine the fate of the cell, or its potiental. 
 - Chemical signals from other cells will also determine activated genes that lead to specialisation
-- (LOCATION LOCATION LOCAION!)
+- (LOCATION LOCATION LOCATION!)
 - Specialisation is determined by reading only certain genes
 
 ### Stem Cells
-- They are an **unspecialized** cell that has the potential to become one of several types of cells. 
+- **Unspecialized** cells with the potential to become one of several types of cells. 
 - Can either divide to two stem cells or one stem cell and one specialised cell
 - Specialised cells generally do not divide
 
@@ -355,7 +339,6 @@ A person contains roughly 100 trillion cells
  - Intestines
     - Pancreas makes most digestive enzymes and pumps them in the duodenum
     - Absorbs nutrients and water to bloodstream
-    - Duodenum digests food chemically even more
     - Forms and excretes feces
     - Contains smooth muscle to continue peristalsis
     - Contains plenty of blood vessels for faster nutrient absorption
@@ -368,7 +351,7 @@ A person contains roughly 100 trillion cells
 ## Respiratory system
  - Exchanges oxygen gas and carbon dioxide gas between red blood cells and the surrounding air, which is required for cellular respiration
  - Diaphragm contracts to lower itself, causing the rib cage to rise, which increases lung volume, which subsequently causes pressure to decrease and air to rush in to the lungs
- - Diaphragm relaxes to return everything to its normal position
+    - Diaphragm relaxes to return everything to its normal position
  - Air is warmed and moisted while passing through nasal cavity blood vessels
  - Trachea and bronchi are made of rigid cartilage rings
     - Prevents airways from closing, similar to a vacuum hose
@@ -468,3 +451,87 @@ A person contains roughly 100 trillion cells
     - Vaccines do not cause autism or seizures, but may act as a trigger for the latter due to genetics
 
 ## Musculoskeletal system
+ - Maintains **structure**
+ - **Protects** other systems and cells
+ - Enables **movement**
+ - Four types of **connective tissues**: Ligaments, tendons, bones, and cartilage
+
+| **Bone** | **Information** | **Location** |
+| :--- | :--- | :--- |
+| Clavicle | Collarbone | Collar |
+| Humerus | Funny bone | Lower upper arm |
+| Femur | Largest bone | Thigh |
+| Tibia | One of two bones in lower leg | Front lower leg |
+| Vertebrae | Enable spinal movement | Spine |
+| Patella | Prevents leg overextension and protects knee join | Kneecap |
+
+### Bones
+ - Hard and dense
+ - Bone cells produce minerals (e.g., phosphorus + calcuium) and **collagen**
+    - Minerals for strength, collagen for flexibility
+ - Bone marrow produces blood cells
+ - Contain blood cells
+
+### Joints
+ - Anywhere where two bones meet
+ - Types of joints
+    - Hinge joint (e.g., knee, elbow)
+    - Ball and socket joint (e.g., Hip, shoulder)
+    - Fixed (e.g., skull, pelvis)
+ - `Ligaments` connect bones across joints
+ - `Cartilage` cushions bone on each side of joint and allows for smooth motion
+
+### Skeletal Muscle
+ - Made of **striated** muscle fibres of long cells
+ - Voluntary muscles, receive signals from brain via nerves
+ - Always come in pairs as **any muscle can only pull, not push**
+ - Must be attached to two bones in order to move a bone
+
+## Nervous System
+ - Coordinates body activities
+ - `Central nervous system`: Brain + spinal cord
+ - `Peripheral nervous system`: All other nerves connecting everything to spinal cord/brain
+ - `Neurons` send electric signals down their singular long `axon` branch thing
+    - They accept signals from `dendrites` on the main cell body
+    - `Schwann cells` form the `myelin sheath` to insulate and nurture the axon, protecting it from interference
+    - Neurotransmitters are chemical signals that transmit information between neurons
+    - Electrical signals tell chemical signals to go to other neurons
+ - Nerves
+    - Bundle of axons
+    - Surrounded with blood vessels and connective tissue
+    - Nerve signals are short-lived, fast, and targeted towards specific groups of cells
+
+### Disorders
+ - Parkinson's disease
+    - Loss of brain neurons that send neurotransmitters to muscles
+    - Leads to muscular and mental decline
+ - Multiple sclerosis
+    - Immune system attacks myelin sheath
+    - Disruption of neurons' electric signals due to lack of protection
+    - Causes spasms and loss of muscular control
+ - Alzheimer's disease
+    - Protein deposits (plaque) build up in brain tissue
+    - Leads to memory loss and total system failure
+
+## Endocrine System
+ - Coordinates organ functions
+ - `Hormone` chemical signals produced by endocrine glands that, compared to nerve signals, are **long-lasting**, **slower**, and **general**
+ - Specific hormones bind to specific receptors on specific cell membranes (e.g., mailing lists)
+ - Hormones travel through the bloodstream
+ - Hormones either encourage or discourage activity
+ - Can cause positive or negative feedback loops with glands
+
+| **Endocrine organ** | **Purpose** | **Location** |
+| :--- | :--- | :--- |
+| Pituitary gland | Controls growth and development | Brain |
+| Pancreas | Secretes insulin to ensure sugar in bloodstream is taken in by cells | Attached to duodenum |
+| Gonads (ovaries + testes) | Secretes the reproductive hormones testosterone and estrogen, respectively | Lower abdomen |
+| Adrenal glands | Control stress response, secrete adrenaline (fight/flight response) | Above kidneys |
+
+### Disorders
+ - Type 1 diabetes: The pancreas is unable to produce any insulin, resulting in high blood sugar
+     - Generally caused by genetics
+ - Type 2 diabetes: The pancreas produces not enough insulin and/or cells are resistant to it, resulting in high blood sugar
+    - Generally caused by lifestyle choices (e.g., diet)
+ - Growth disorders (dwarfism/gigantism)
+    - Caused by poor pituitary and/or hypothalamus function or endocrine gland damage as an adult