Science Sem 1 Test Flashcards
Define homeostasis
The process where an organism maintains a stable internal environment despite changes to the external environment.
What is the stimulus response pathway?
Stimulus - Receptor - Control Centre - Effectors - Response
Explain stimulus
A change in internal or external environment that triggers a response. It is a piece of information that
the receptors detect when it changes.
Explain Receptors
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.
Explain Control Centre
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.
Explain Effectors
Muscles, glands or organs that carry out the response directed by the control centre.
Explain Response
Action or change in behavior that occurs as a result of the stimulus. Aimed at restoring homeostasis or protecting the body.
Types of sensory (broad) receptors
Vision, touch, smell, hearing, taste
Types of Body Receptors
Chemoreceptors
Mechanoreceptors
Photoreceptors
Thermoreceptors
Olfactory Receptors
Nociceptor
Explain chemoreceptors
Located in blood vessels or the brain
Stimulus it detects are changes in blood chemistry (oxygen, pH levels, CO2).
Explain Mechanoreceptors
Located in the skin, muscles, joints and the inner ear.
Stimulus it detects is touch/pressure/stretching and sound.
Touch + hear
Explain Photoreceptors
Located in the retina of the eye.
Stimulus it detects is light energy.
Vision
Explain Thermoceptors
Located in skin and brain.
Stimulus it detects is a change in external/internal temperature.
Touch
Explain Olfactory Receptors
Located in the nose
Stimulus it detects are chemicals in the air (smells)
Smell
Explain the Gustatory Receptors
Located in taste buds on the tongue
Stimulus it detects are the chemicals in food/drink (taste)
Taste
Explain Nociceptors
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
Why is homeostasis important for survival?
Regulates blood oxygen and pH levels which are critical for survival and would not be regulated without the process of homeostasis.
Compare negative feedback to positive feedback
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.
Factors our body must keep balanced include:
- pH levels
- blood glucose levels
- blood oxygen levels
- internal temperature
- water levels
What is the Stimulus Response Pathway for running around outside in hot weather and then sweating and turning red because of it?
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.
What is the pH of the extracellular fluid inside humans?
7.35-7.45
How can the respiratory system control the extracellular pH?
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.
Define extracellular
Anything outside of the cells. E.g. plasma or interstitial fluid
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.
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.
Break down the Nervous system
Nervous system > CNS
> PNS
PNS > Somatic
> Autonomic
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.
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.
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.
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.
Structure of a neuron
Dendrites
Cell body (soma)
Axon
Dendrites
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.
Function of nucleus
control centre
Function of cell body (soma)
Control centre: contains the nucleus and other organelles
Function of axon
Long cable that transmits the impulse (electrical signals/messages) through to other neurons
Function of myelin sheath
Insulate the axon which speeds up transmission of messages
Function of axon terminal
Transmits messages to next neuron
Three types of neurons
Sensory
Motor
Inter
Explain sensoryneurons
Transmits messages from sensory organs (eyes, tongue) to interneurons.
Go towards the brain
Explain interneurons (in the CNS)
Transmits messages from sensory neurons to motor neurons - around and in between the brain.
Explain motorneurons
Transmits messages from interneurons. Goes from brain to effectors to tell them the response.
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.
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.
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).
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.
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.
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.
What is the endocrine system?
Communication system which controls the internal environment of the body and works with the nervous system.
What are endocrine glands?
They secrete chemicals called hormones in response to internal or external stimuli.
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.
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.
What is the thyroid gland?
Produces the hormone thyroxine - controls the metabolism rate and also brings out balanced growth.
What is the Parathyroid gland?
Produces the hormone parathormone - controls the calcium balance in the body.
What is the adrenal gland?
Produces the hormone adrenaline - prepares the body for an amergency.
What is the pancreas (gland)?
Produces the hormone insulin - controls glucose levels in the blood.
What are the testes (gland)?
Produces the hormone testosterone - controls growth and development in the male reproductive system.
What are the ovaries (gland)?
Produces the hormone oestrogen and progesterone - controls growth and development of the female reproductive system.
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)
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
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.
Hormones travel from ___ through the ___ to ____
Endocrine glands
Bloodstream
Target organs
What are the types of microorganmisms
Pathogens
Viruses
Fungi
Parasites
What are pathogens?
Disease causing organisms or agents (factors). E.g. bacteria, bacterial infections, antibiotics
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
What are bacterial infections?
- some bacteria releases posonous substances called toxins. E.g. whooping couch, tetanus, pneumonia and salmonella.
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
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.
What are viral infections?
Sicknesses that viruses cause - common cold, cold sores, pneumonia
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
What are fungal infections?
Infections caused by the growth of fungi - thrush, athletes foot and ringworm
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
What are parasitic infections?
Infections caused by parasites - malaria, amoebic dysentery, elephantiasis (caused by many types of parasitic worms).
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
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
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.
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
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.
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
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.
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.
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.
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.
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.
Define element
Contain atoms but only one type so all atoms within an element are identical. Cannot be broken down chemically.
Define compound
A substance formed by the chemical combination of two or more different elements. E.g. NaCl.
Define molecules
A chemical made up of two or more non metal atoms. Can be a molecular element: 02 or a molecular compound: H20
Define combustion
A type of reaction where a substance reacts with oxygen, releasing heat and light: C02 and H20
Parts of atom
Atom cloud - electron shells
Atom nucleus - protons (+) and neutrons (neut.)
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.
What is the mass number?
Total number of protons and neutrons in the atom.
How many electrons are allowed in each shell?
First: 2
Second: 8
Third: 18 (sometimes 8 but is actually 18)
Fourth: 32
How do you draw electrons onto an atom?
Go clockwise and in pairs
What are valence electrons?
The electrons in the outer shell of an atom. Each electron shell has a difefrent amount of eergy.
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.
