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Term 1 Yr 9 > Science Sem 1 Test > Flashcards

Science Sem 1 Test Flashcards

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1
Q

Define homeostasis

A

The process where an organism maintains a stable internal environment despite changes to the external environment.

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2
Q

What is the stimulus response pathway?

A

Stimulus - Receptor - Control Centre - Effectors - Response

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3
Q

Explain stimulus

A

A change in internal or external environment that triggers a response. It is a piece of information that
the receptors detect when it changes.

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4
Q

Explain Receptors

A

Specialised cells or organs that detect the stimulus. Converts the stimulus to electrical or chemical signals which are sent to the CNS. There are different types of receptors.

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5
Q

Explain Control Centre

A

In a human the CC is usually the brain (hypothalamus) or the spinal chord. It processes the information received from the receptors and decides the appropriate response. It signals the Effectors of this response.

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6
Q

Explain Effectors

A

Muscles, glands or organs that carry out the response directed by the control centre.

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7
Q

Explain Response

A

Action or change in behavior that occurs as a result of the stimulus. Aimed at restoring homeostasis or protecting the body.

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8
Q

Types of sensory (broad) receptors

A

Vision, touch, smell, hearing, taste

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9
Q

Types of Body Receptors

A

Chemoreceptors
Mechanoreceptors
Photoreceptors
Thermoreceptors
Olfactory Receptors
Nociceptor

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10
Q

Explain chemoreceptors

A

Located in blood vessels or the brain

Stimulus it detects are changes in blood chemistry (oxygen, pH levels, CO2).

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11
Q

Explain Mechanoreceptors

A

Located in the skin, muscles, joints and the inner ear.

Stimulus it detects is touch/pressure/stretching and sound.

Touch + hear

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12
Q

Explain Photoreceptors

A

Located in the retina of the eye.

Stimulus it detects is light energy.

Vision

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13
Q

Explain Thermoceptors

A

Located in skin and brain.

Stimulus it detects is a change in external/internal temperature.

Touch

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14
Q

Explain Olfactory Receptors

A

Located in the nose

Stimulus it detects are chemicals in the air (smells)

Smell

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15
Q

Explain the Gustatory Receptors

A

Located in taste buds on the tongue

Stimulus it detects are the chemicals in food/drink (taste)

Taste

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16
Q

Explain Nociceptors

A

Located in the skin, muscles, joints and organs

Stimulus it detects is tissue damage (e.g. hot or cold temperatures causing burns and also pressure it can detect).

Aka pain receptors

Touch

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17
Q

Why is homeostasis important for survival?

A

Regulates blood oxygen and pH levels which are critical for survival and would not be regulated without the process of homeostasis.

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18
Q

Compare negative feedback to positive feedback

A

Negative feedback (decelerating mechanism) is the body’s biological control mechanism that reverses internal environments that are abnormal and reverses them to their normal state. Aims to restore homeostasis through counteracting the stimulus. E.g. body temp rising and high glucose

Positive feedback (accelerating mechanism) amplifies the stimulus to move it further from balance. This is to speed up processes like childbirth and the healing of wounds where scabs form. Things are produced inside body like platelets or oxytocin to amplify the stimulus.

Both are control mechanisms to help regulate processes or maintain balance.

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19
Q

Factors our body must keep balanced include:

A
  • pH levels
  • blood glucose levels
  • blood oxygen levels
  • internal temperature
  • water levels
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20
Q

What is the Stimulus Response Pathway for running around outside in hot weather and then sweating and turning red because of it?

A

Increased external environment temperature - thermoreceptors detect stimulus - hypothalamus receives the information about the external temperature rising - sweat glands and blood vessels dilate and move around - causes red skin and sweating which drops the internal body temperature to homeostasis.

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21
Q

What is the pH of the extracellular fluid inside humans?

A

7.35-7.45

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22
Q

How can the respiratory system control the extracellular pH?

A

By regulating the amount of C02 in the blood. Negative feedback reverses high pH levels (lower numbers) by dissolving more C02 into the blood. Lower pH’s are more acidic. When C02 dissolves into the blood, it forms carbonic acid which lowers pH.

The respiratory system can hyperventilate - breathe faster - to allow more C02 to enter the body to lower pH levels. Then it can hypoventilate - breathe slower - to allow less C02 to enter the body, resulting in a higher pH, restoring balance and homeostasis.

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23
Q

Define extracellular

A

Anything outside of the cells. E.g. plasma or interstitial fluid

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24
Q

Explain why the sensitivity of areas of the skin may be more/less sensitive when in relation to the body part’s function. Mention the distribution of receptors.

A

More sensitive parts of the body (such as hands and fingers) have more thermoreceptors, mechanoreceptors and nociceptors, to detect touch. This is needed because we use our hands for everything everyday so to keep them protected, we have lots of touch receptors there to warn our body when they get too hot or when changes in the external environment are too extreme.

Less sensitive areas, like the back or upper arms, have fewer touch receptors since they are not used for fine tasks or frequent interaction. With less need for protection, they have fewer thermoreceptors, mechanoreceptors, and nociceptors, making them less sensitive.

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25
Break down the Nervous system
Nervous system > CNS > PNS PNS > Somatic > Autonomic
26
Compare the CNS to PNS
The CNS (central nervous system) includes the brain and spinal cord and controls most body functions by processing information and sending out commands. The PNS (peripheral nervous system) is made up of nerves that branch out from the CNS to the rest of the body, carrying signals to and from muscles, organs, and senses. The brain controls the body, and the spinal cord helps relay messages between the brain and the rest of the body.
27
Compare somatic and autonomic
The somatic nervous system controls voluntary muscle movements, like walking or picking up an object, by sending signals from the brain to the muscles. The autonomic nervous system controls involuntary functions and provides self-regulatory control over internal muscles, organs, and glands, managing processes like heartbeat and digestion without conscious effort.
28
What is the nervous system?
A communication system which controls the rest of the body. It receives messages and sends out others to the body.
29
What are neurons?
Unidirectional (top to bottom) specialized cells that transmit electrical and chemical signals through the nervous system, allowing communication between the brain, spinal cord, and body. They make up the nervous system They are located everywhere in the body, except are concentrated through the CNS and PNS areas.
30
Structure of a neuron
Dendrites Cell body (soma) Axon Dendrites
31
Function of dendrites
Long branches that extend from the neuron and receive messages from receptors and other nerve cells. The dendrites at the bottom of the neuron (axon terminal) connect to the top dendrites of another neuron.
32
Function of nucleus
control centre
33
Function of cell body (soma)
Control centre: contains the nucleus and other organelles
34
Function of axon
Long cable that transmits the impulse (electrical signals/messages) through to other neurons
35
Function of myelin sheath
Insulate the axon which speeds up transmission of messages
36
Function of axon terminal
Transmits messages to next neuron
37
Three types of neurons
Sensory Motor Inter
38
Explain sensoryneurons
Transmits messages from sensory organs (eyes, tongue) to interneurons. Go towards the brain
39
Explain interneurons (in the CNS)
Transmits messages from sensory neurons to motor neurons - around and in between the brain.
40
Explain motorneurons
Transmits messages from interneurons. Goes from brain to effectors to tell them the response.
41
How does the communication of action potential through the neuron work?
Action potential reaches dendrites and goes down the axon. Once it reaches the axon terminal, neurotransmitters pass the action potential into the next neuron. Then it crosses the synapse and enters the next neuron to continue passing the message on.
42
Explain synapses
The junction between neurons where neurotransmitters pass through to deliver action potential to other neurons. The action potential is converted into a chemical signal via a neurotransmitter which carries the message across the synapse. This is then converted back into an electrical signal.
43
Explain the steps of synapse transmission
STEP 1 - The action potential reaches the presymaptic (axon) terminal. STEP 2 - This triggers the release of neurotransmitters from the synaptic vesicles in the presynaptic axon to go through the synaptic cleft. STEP 3 - The neurotransmitter binds to receptors on the postsynaptic dendrite. STEP 4 - The action potential transmits through the next cell (postsynaptic neuron).
44
Define a reflex
A reflex action or reflex arc is a fast, involuntary response that protects the body from danger. The spinal chord is responsible for detecting the initial stimulus and initiating a response - it bypasses the brain.
45
Compare the reflex arc and stimulus response models of the nervous system.
The reflex arc is a fast, automatic response that bypasses the brain, while the stimulus-response model describes the broader process of how the nervous system detects and reacts to stimuli.
46
What is a hormone?
A regulatory substance produced in an organism and transported in tissue fluids such as blood to stimulate specific cells or tissues into action. They attach to receptors on target cells to produce a slow but long lasting response.
47
What is the endocrine system?
Communication system which controls the internal environment of the body and works with the nervous system.
48
What are endocrine glands?
They secrete chemicals called hormones in response to internal or external stimuli.
49
What does the hypothalamus do in the brain?
Constantly checks your body's internal environment. Links the nervous system and the endocrine system. It secretes hormones that act on the pituitary gland.
50
What is the Pituitary gland?
Master gland - controls other endocrine glands and is responsible for things like hormones and puberty. Is located in brain. It produces the growth hormone and regulates growth, controls the functioning of the endocrine glands.
51
What is the thyroid gland?
Produces the hormone thyroxine - controls the metabolism rate and also brings out balanced growth.
52
What is the Parathyroid gland?
Produces the hormone parathormone - controls the calcium balance in the body.
53
What is the adrenal gland?
Produces the hormone adrenaline - prepares the body for an amergency.
54
What is the pancreas (gland)?
Produces the hormone insulin - controls glucose levels in the blood.
55
What are the testes (gland)?
Produces the hormone testosterone - controls growth and development in the male reproductive system.
56
What are the ovaries (gland)?
Produces the hormone oestrogen and progesterone - controls growth and development of the female reproductive system.
57
Compare the nervous and endocrine system.
Nervous - Involuntary and voluntary Signals are electrical and sent via electrical impulses and neurotransmitters Neurons make up the pathway which is through the nervous system (brain and spinal chord). Fast info transfer Short lived effects Localised target cells Endocrine - Involuntary Signals are chemical Transported via hormones Pathway is through bloodstream and lymph which is a fluid (lymphatic system) Slow info transfer Longer lasting effects Systemic target cells (many cells can be affected - widespread and many at a time)
58
Explain the fight or flight response in relation to the endocrine and nervous system.
Endocrine - adrenaline and cortisol increase your pulse and breathing rate - blood glucose levels rise to provide muscles with energy Nervous - pupils dilate - breathing and heartrate increase - sweat more - digestion slows down
59
How is blood glucose regulated in the body?
Insulin is released by pancreas when blood glucose levels are high Insulin converts excess glucose into glycogen or fat in the liver and muscle, decreasing the glucose concentration in the blood Glucagon is secreted by the pancreas when blood sugar levels are low Glucagon signals liver to breakdown glycogen and release glucose back into bloodstream, increasing the glucose concentration in blood.
60
Hormones travel from ___ through the ___ to ____
Endocrine glands Bloodstream Target organs
61
What are the types of microorganmisms
Pathogens Viruses Fungi Parasites
62
What are pathogens?
Disease causing organisms or agents (factors). E.g. bacteria, bacterial infections, antibiotics
63
What are bacteria?
Type of pathogen - unicellular organisms - most are harmless but some are beneficial (friendly bacteria in digestive tract and decomposers in the environment) - pathogenic bacteria causes disease
64
What are bacterial infections?
- some bacteria releases posonous substances called toxins. E.g. whooping couch, tetanus, pneumonia and salmonella.
65
What are antibiotics?
Treat pathogens that are bad - Medicine that treats bacterial infections - substances that kill or prevent the growth of (all) bacteria. E.g. penicillin
66
What are viruses?
- pathogens about 1/100th the size of bacteria - non living because they don't need nutrients, don't produce waste and do not exchange gases with the environment. - viruses are pathogens. Must invade a host cell to replicate - host cell is damaged/destroyed when it releases new viruses that spread throughout the body, infecting other cells. - Infect all types of living things - even bacteria.
67
What are viral infections?
Sicknesses that viruses cause - common cold, cold sores, pneumonia
68
What are fungi?
- some fungi are useful like mushrooms - food source - others are decomposers e.g. molds that break down dead plant or animal matter - most are multicellular (besides yeast) - fungi are spread by spores which are made of a single cell - like warm, moist environments so they grow well on your skin
69
What are fungal infections?
Infections caused by the growth of fungi - thrush, athletes foot and ringworm
70
What are parasites?
- an organism that lives in or on the body of another organism (host) and takes nutrients from it - A parasite benefits at the expense of the host organism (grows bigger on your food) - you do not digest food properly and get very sick
71
What are parasitic infections?
Infections caused by parasites - malaria, amoebic dysentery, elephantiasis (caused by many types of parasitic worms).
72
What is the immune system?
- involves biological structures and processes which keep the body protected against disease. There are three main defense mechanisms: 1st, 2nd, 3rd lines of defence
73
Explain the first line of defence
Defends against infection and are the surface barriers that prevent the entry of pathogens e.g. skin, mucous, stomach acid
74
Explain the 2nd line of defence
An antigen is anything that triggers an immune response. 2nd line of defense includes: - phagocytosis - inflammation - fever The second line of defense fights infection but also causes sickness symptoms (when pathogens bypass the first line of defense, the 2nd line takes control.
75
Explain what phagocytosis is?
Type of white blood cell that engulfs and digests pathogens. E.g. neutrophils and macrophages. This process releases chemicals that trigger inflammation and fever, causing symptoms like swelling and heat
76
Explain what inflammation is?
- bodies response to infection - once pathogens enter body tissues, are becomes red, hot and swollen, due to histamine being released and causing more blood to flow to the infected area. - pus forms around wounds because neutrophils and macrophages die as they consume and destroy bacteria, releasing their contents and causing a thick, yellowish fluid. - Pus is helpful because it shows your immune system is fighting infection.
77
Explain what fever is?
- increase in body temp prevents pathogens from reproducing as fast. This gives immune system time to fight them more easily. E.g. normal temp: 36.6-37.2
78
What is the third line of defence?
- lymph nodes contain large numbers of white blood cells including lymphocytes, - function of lymphocytes is to destroy pathogens and protect the body from re-infection - some lymphocytes make proteins called antibodies. - antibodies cause pathogens to clump together so phagocytes can engulf and destroy them.
79
Explain antibodies
- specific to a particular pathogen - can take time for the body to produce the antibodies, in the meantime you get sick and show symptoms of disease. - after the infection, the body makes memory lymphocytes so if you are re-infected with the same pathogen, the memory lymphocytes make antibodies very quickly. the pathogen is destroyed quickly and you don't get sick.
80
Explain vaccinations
- given if disease is particularly harmful - contains weakened or dead forms of the pathogen which is harmless, but your immune system responds to the vaccine by producing antibodies. - your body also makes billions of memory lymphocytes against the pathogen, which remain stored in the body. - if you become infected by the same pathogen as in the vaccine, your memory lymphocytes are activated and produce trillions of antibodies more rapidly so you don't get sick - provide long-term immunity but some memory cells may not last forever so booster shots are required.
81
How do vaccines work?
The second time you are exposed to the same pathogen as in the vaccine, the concentration of antibodies in the blood is much higher.
82
Define atom
Smallest possible form of an element. There is a unique atom for every element. Made up of subatomic particles and atoms are the building blocks for everything. Smallest unit of matter.
83
Define element
Contain atoms but only one type so all atoms within an element are identical. Cannot be broken down chemically.
84
Define compound
A substance formed by the chemical combination of two or more different elements. E.g. NaCl.
85
Define molecules
A chemical made up of two or more non metal atoms. Can be a molecular element: 02 or a molecular compound: H20
86
Define combustion
A type of reaction where a substance reacts with oxygen, releasing heat and light: C02 and H20
87
Parts of atom
Atom cloud - electron shells Atom nucleus - protons (+) and neutrons (neut.)
88
What is the atomic number?
Tells you the number of protons in the nucleus and the number of electrons (only in a neutral atom) and the location on the periodic table.
89
What is the mass number?
Total number of protons and neutrons in the atom.
90
How many electrons are allowed in each shell?
First: 2 Second: 8 Third: 18 (sometimes 8 but is actually 18) Fourth: 32
91
How do you draw electrons onto an atom?
Go clockwise and in pairs
92
What are valence electrons?
The electrons in the outer shell of an atom. Each electron shell has a different amount of energy. This is unstable so the electrons drop back down to their original energy level releasing the absorbed energy as light.
93
What is an ion?
When atoms lose of gain electrons, they become ions. The properties of the element changes but the type of element doesn't change.
94
What is Hydrogen?
Non-metal
95
Where are all the different categories on the periodic table?
Left = Metals Middle-right = metalloids Right = non metals
96
What are the vertical columns called on the PT?
Groups - all have same number of valance electrons Group 1 has one shell in total. Group 2 has two shells. Group 3 has three shells.
97
What are the horizontal rows called on the PT?
Periods - all have same number of electron shells
98
What are groups 1, 2, 3-12, 13, 17 and 18 called?
1 = Alkali metals 2 = Alkaline metals 3-12 = Transition metals 13 = Metalloids - staircase - 112 112 17 = Halogens 18 = Noble gases
99
Characteristics of metals
- lustrous - malleable - bendy - ductile - stretchy - conductors of heat and electricity - mostly solid at room temp
100
Characteristics of non-metals
- have 4-8 valence electrons - poor conductors of heat and electricity - dull - brittle
101
Describe halogens (G17)
- non metals - only group to have solid, liquid and gas present at room temp - highly reactive as only need one more valence electron to have a full outer shell - diatomic molecules
102
Describe noble gases (G18)
- all gases at room temp - all gases on PT want to achieve noble gas structure - inert - will not react as they have full outer shells
103
Describe monatomic molecules
- single atoms - noble gases are monatomic because they're inert
104
Describe diatomic molecules
- consist of two atoms joined together - only 7 diatomic molecules on periodic table
105
List all diatomic molecules on the periodic table.
I Bring Cookies For Our New Home Iodine Bromine Chlorine Fluorine Oxygen Nitrogen Hydrogen
106
How do you find the number of neutrons?
Mass number - atomic number
107
Stable VS Unstable atoms
Stable has the same number of protons and neutrons. Unstable has different or unmatched numbers of protons and neutrons in the nucleus. Unstable atoms are isotopes and result in radioactive decay.
108
What is an isotope?
Elements that have the same atomic number but different mass number so therefore a different number of protons and neutrons. Stable isotopes are the same as normal atoms.
109
How do you name an isotope?
Writing the element first and them doing a dash and then the mass number.
110
What is the stability of an isotope based on?
- whether it's likely to break down or decay into other elements.
111
What are unstable isotopes trying to achieve?
A stable nucleus
112
Define radioisotopes
Unstable isotopes - they are atoms that undergo decay rather than just break down.
113
Are stable isotopes radioactive?
Stable isotopes are just normal atoms so aren't radioactive as they have a stable nucleus.
114
Explain radioactive decay
- isotopes with different numbers of protons and neutrons will eventually decay by emitting a particle. - this transforms the element into a new one called transmutation. This process = nuclear decay and emits radiation. - a chain of decays takes place until a stable nucleus is reached.
115
What are the types of radioactive decay?
Alpha, Beta, Gamma
116
Explain alpha decay
- alpha particle consists of two protons and two neutrons. Therefore when an atom undergoes alpha decay, the atomic number decreases by 2 and the mass number decreases by 4. When atomic number changes, a new element is formed. Then, the new element has 2 fewer protons. 4 A 2
117
Explain Beta decay
- beta particles are fast moving electrons emitted from a nucleus. - during beta decay, a neutron is transmuted (changes) into a proton and an electron. - consequently the atomic number increases by one which changes the element altogether. The mass number of the remaining atom is not affected because it has lost a neutron but gained a proton. 0 B -1
118
Explain gamma decay
- different from alpha and beta because the atom undergoing gamma decay is not changed. Meaning that the mass and the atomic number are not altered. - this is because gamma decay involves the emission of a high energy wave (gamma ray) rather than a particle. 0 Y 0
119
Which type of radioactive decay has the most penetrating ability?
Alpha = least Gamma = most
120
Explain half-life
The time taken for half the atoms in a sample to decay.

Term 1 Yr 9 (5 decks)

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