#science/y9/nervous-system#science/y9/atoms
Atoms
- An atom is made up of 3 particles (protons, neutrons and electrons)
- Protons have a positive charge, and have a relative mass of 1. There must be the same number of protons as there are electrons.
- Neutrons have a neutral charge, and also have a relative mass of 1. The number of neutrons in an atom can create isotopes of the same element.
- Electrons have a negative charge, and orbit around the nucleus of an atom in ‘shells’. They have a mass of 1/1840.
- An isotope is simply another form of the same element that contains equal numbers of protons but differs in their numbers of neutrons.
- There are two types of isotopes, stable isotopes (don’t emit radiation) and unstable isotopes (emit radiation)
Electron orbits and valence electrons
- Electron orbits are filled in order, the first orbit can hold 2, the second can hold 8 and the third can also hold 8.
- Elements react because they want to fill or empty their ‘shells’ (orbits).
- Noble gasses don’t react as their outer shells are full.
- Ions: Atoms that have reacted to gain an electrical charge (positive or negative)
- Ions with fitting electrical charges (e.g. +1 and -1) stick together, this forms a new substance
- Valence electrons are the electrons in the outermost ‘shell’ of an atom.
Covalent bonds
- Covalent compounds are formed when two nonmetal atoms create a covalent bond by sharing valence electrons.
Radioactive decay and half life
- Alpha Decay: Nucleus emits an alpha particle (2 protons and 2 neutrons), reducing atomic number by 2 and mass number by 4.
- Beta Decay (minus): a neutron transforms into a proton, emitting an electron (beta-minus particle) and increasing atomic number by 1.
- Beta Decay (plus): In beta-plus decay, a proton transforms into a neutron, emitting a positron (beta-plus particle) and decreasing atomic number by 1.
- Gamma Decay: Nucleus emits high-energy gamma rays without changing atomic or mass number.
- Half life: the time it takes for something that’s falling apart or decaying to reduce in quantity by half.
Acids and bases
- Acids have a sour taste, react with metals and can be corrosive
- Bases can be solid or liquid. They have a bitter taste and are corrosive.
- Some solid bases can be dissolved in water. A base that is soluble in water is called an alkali.
- Neutral substances are not corrosive – they tend to be harmless to the touch. They may have a sweet or salty taste or no taste.
- Lower pH = acidic, higher pH = basic. 7 is neutral. (water is neutral).
More chemistry
- Ions are electrically charged particles that can be positively charged (cations) or negatively charged (anions).
- Cations have more protons than electrons, giving them a net positive charge.
- Anions have more electrons than protons, resulting in a net negative charge.
Nervous system
- A neuron is a single nerve cell that transmits electrical signals.
- A nerve is a bundle of neurons that transmits signals between the brain, spinal cord, and other body parts.
- Reflex actions are rapid and automatic responses to stimuli to protect the body.
Neurons consist of a dendrite, cell body, axon and an axon terminal. They also have a myelin sheath to keep the electrical signal going, and to protect the neuron.
Endocrine system
- The endocrine system uses hormones for slower, longer lasting regulation of bodily functions, while the nervous system uses electrical impulses and neurotransmitters for fast, shorter responses.
Main hormonal glands
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- Hypothalamus: controls important body functions like temperature, hunger / thirst and sleep. Tells the pituitary gland when to release hormones.
- Pineal gland: produces melatonin, which helps regulate our sleep.
- Pituitary gland: the pituitary gland controls other glands in the body.
- Thyroid gland: makes hormones that control our metabolism (how we use energy)
- Adrenal glands: releases adrenaline for quick energy in emergencies and for responses to stress.
- Pancreas: controls the sugar (glucose) in our blood. It helps our cells get the energy they need.
- Ovaries: produce eggs for reproduction and hormones, which regulate the menstrual cycle and pregnancy.
- Testes: make sperm for reproduction and release testosterone, which is responsible for male characteristics like facial hair and deep voices.
Insulin, glucose and glucagon
- Glucose is a simple sugar and the primary source of energy.
- Insulin is a hormone that lowers blood sugar levels by promoting the absorption of glucose into cells.
- Glucagon is a hormone that raises blood sugar levels by stimulating the release of glucose from the liver.
- Type 1 diabetes: insufficient insulin production.
- Type 2 diabetes: cells become resistant to insulin, leading to high blood sugar levels.
Blood-water levels
- When blood water levels rises above normal, the pituitary gland reduces the release of ADH, leading the kidneys to excrete excess water, which results in homeostasis.
- When blood water falls below normal, the pituitary gland produces ADH, making the kidneys to retain more water in the bloodstream, which results in homeostasis.
The brain
- Cerebrum: The largest part of the brain, divided into frontal, parietal, occipital, and temporal lobes, responsible for complex cognitive functions.
- Frontal Lobe: Controls decision-making, problem-solving, and personality.
- Parietal Lobe: Manages sensory perception and spatial awareness.
- Occipital Lobe: Processes visual information and sight.
- Temporal Lobe: Handles auditory processing and memory.
- Thalamus: Relays sensory and motor signals to the cerebral cortex.
- Cerebellum: Coordinates movement, balance, and fine motor skills.
- Brain Stem: Controls basic life functions like breathing and heart rate.
- Amygdala (in temporal lobe): processes emotions emotions - fear and emotional memories.
- Hippocampus (in temporal lobe): forming and consolidating memories, particularly those related to spatial navigation and long-term declarative memory.