Homeostasis and response Flashcards
Define homeostasis.
The regulation of the internal conditions of a cell or organism to maintain optimum conditions.
Why does homeostasis need to maintain optimal conditions?
For enzyme action and all cell functions.
List three conditions that the body needs to maintain.
Blood glucose concentration, body temperature and water levels.
What do the two automatic response systems involve?
Nervous responses or chemical responses.
Define stimuli.
Changes in the environment.
List the receptor cells and state what stimulus they detect.
Eye (retina) - light, Ear – sound, Nose – Chemicals in the air, Mouth (tongue) – chemicals in food, Skin - touch, pressure, pain and temperature
Name the 3 coordination centres in the body and describe what each of them coordinates.
Brain - coordinates information from the receptor cells and send signals to the muscles and glands.
Spinal cord - Coordinates messages from the brain and receptor cells and coordinates reflexes.
Pancreas - coordinates the glucose levels in the blood.
What is an effector?
A muscle or gland.
Name the three main parts of the brain and state the role of each.
cerebral cortex – is the outer ‘wrinkled’ layer of the brain it is responsible for intelligence, language, memory and consciousness;
cerebellum – is located at the lower part of the back of the brain and is responsible for voluntary coordination of the muscles;
medulla – is located in the lower part of the brain stem. It is responsible for involuntary coordination such as breathing, swallowing and heart rate
How do neuroscientists study the brain?
Studying patients with brain damage, electrically stimulating the brain and using magnetic resonance imaging (MRI) scanning.
What is an EEG?
electroencephalogram (EEG) is a test used to find problems related to electrical activity of the brain.
What is an MRI?
A device that uses strong magnetic fields and radio waves to produce detailed images of the brain and spinal cord.
What does an MRI do?
MRI can distinguish between different types of tissues, including detecting cancerous cells.
Describe the cornea
Transparent layer at the front of the eye, it refracts light into the eye.
Describe the iris
The coloured part of the eye, contains muscles that control the amount of light entering the eye.
Describe the pupil
The hole in the middle of the iris that lets light in. Its diameter is controlled by the iris.
Describe the lens
A transparent, biconvex structure in the eye that refracts light onto the retina.
Describe the retina
Thin layer of tissue at the back of the eye that contains receptor cells for light and colour.
Describe the sclera
Tough white supporting wall of the eye.
Describe the ciliary muscles
Muscles that are connected to the lens by the suspensory ligaments; they change the shape of the lens.
Describe the suspensory ligaments
These connect the lens to the ciliary muscles.
Describe the optic nerve
Carries impulses fro the retina to the brain.
What is accommodation?
The process of changing the shape of the lens focus on near or distant objects
How does the eye focus on distant objects?
The ciliary muscles relax, the suspensory ligaments are pulled tight, the lens is then pulled thin and only slightly refracts light rays
How does the eye focus on near objects?
The ciliary muscles contract, the suspensory ligaments loosen, the lens is then thicker and refracts light rays strongly
What is myopia? How can it be corrected?
Short-sightedness, it can be corrected with concave lenses
What is hyperopia? How can it be corrected?
Long-sightedness, it can be corrected with convex lenses
Name three ways that vision can be corrected?
Contact lenses, laser surgery and lens replacement
State the optimum human body temperature.
37oC
What part of the brain monitors and controls temperature?
Thermoregulatory centre
Describe what happens in vasoconstriction and vasodilation.
If the body temperature is too low, blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver).
If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. Both these mechanisms cause a transfer of energy from the skin to the environment.
What is the endocrine system composed of?
Glands
State the ways in which water is lost from the body.
Lungs, urine, skin (sweat)
Sweat contains mostly water. What else can be found in sweat?
Ions and urea
What is removed via the kidneys in the urine?
Excess water, ions and urea
What is a hypertonic solution?
More concentrated solution than in the cells e.g. concentrated sugar solution
What is an isotonic solution?
Same concentration as the solution in the cell
What is a hypotonic solution?
More dilute than the solution in the cells. e.g. water or dilute sugar solution
What happens to animal cells when they are put in water?
Water enters the cell by osmosis and as the volume increases this puts pressure on the cell membrane and it bursts. This is called lysis.
What happens to animal cells when they are put in a concentrated sugar solution?
Water leaves the cell by osmosis and the cells shrink and the membrane wrinkles. This is called crenation
What happens to excess proteins in the diet?
They are transported to the liver and converted into urea
What does deaminated mean?
An amino group is removed from an amino acid.
What is ammonia converted to in the liver?
Urea
Name the structures in the kidneys where the blood is filtered.
Kidney tubules (nephrons)
What are the 3 steps in the blood filtering process?
Filtration, selective reabsorption and excretion
Describe what happens in each of the 3 steps of the blood filtering process.
Filtration of glucose, urea, ions (salts) and water from the blood.
Selective reabsorption of ALL glucose, some ions (salts) and some water into the blood.
Excretion of ALL urea, excess ions (salts) and excess water into the urine.
Where in the body are the water levels in the blood monitored?
The pituitary gland in the brain
Name the hormone that controls the water levels in the blood
Anti-diuretic hormone (ADH).
What effect does an increased levels of this hormone have on the kidneys?
The kidney tubules to become more permeable to water. Increased levels of ADH cause the kidneys to re-absorb more water
Describe what happens in the body when the water content of the blood is too low?
The PITUITARY GLAND releases ADH into the blood, Kidney Tubules MORE permeable and reabsorb MORE water MORE CONCENTRATED urine is produced and the blood water levels return to normal
Describe what happens in the body when the water content of the blood is too high?
The PITUITARY GLAND stops releasing ADH into the blood, Kidney Tubules LESS permeable and reabsorb LESS water LESS concentrated urine is produced and the blood water levels return to normal
How does kidney dialysis treat kidney failure?
Filters the blood to restores the concentrations of dissolved substances in the blood to normal levels
Describe how the dialysis machine works
Blood high in urea flows between partially permeable membranes in the opposite direction to the dialysis fluid (maintains the concentration gradient). The dialysis fluid contains the same concentration of useful substances as the blood - this ensures that glucose and ions (salts) are not lost. Urea passes out from the blood into the dialysis fluid.
How does a kidney transplant treat kidney failure?
A diseased kidney is replaced by a healthy donor kidney; this can be from a live donor or from someone who has died.
State the advantages of kidney dialysis and kidney transplants.
Kidney Dialysis – Advantages: Available to all kidney patients (no shortage), no need for immune-suppressant drugs Disadvantages: Patient must limit their salt and protein intake between dialysis sessions, expensive for the NHS, regular dialysis sessions (up to 8hrs) – impacts on the patient’s lifestyle, risk of infection Kidney Transplant – Advantages: Patients can lead a more normal life without having to watch what they eat and drink, cheaper for the NHS overall
State the disadvantages of kidney dialysis and kidney transplants.
Disadvantages: Must take immune-suppressant drugs which increase the risk of infection, shortage of organ donors, kidney only lasts 8-9 years on average, any operation carries risks
What is the name of the main female reproductive hormone and where is it produced?
Oestrogen and it is produced in the ovaries
What is the name of the main male reproductive hormone and where is it produced?
Testosterone and it is produced in the testis
Define the word puberty.
The stage in life when a child’s body develops into an adult’s body
Between what ages does puberty usually occur?
10 to 16
What are the female secondary sexual characteristics?
Breasts develop, hips get wider, ovaries start to release eggs, pubic and underarm hair grows, sexual organs grow and develop
What are the male secondary sexual characteristics?
Voice deepens, body becomes more muscular, testes start to produce sperm, facial, pubic, underarm and body hair grows , sexual organs grow and develop
What is the menstrual cycle and how long is it?
It is the reproductive cycle in women, it is brought about by hormones. It lasts around 28 days
At what stage of the menstrual cycle is an egg released?
About half way through, usually day 14
Where is FSH released and what is its role in the menstrual cycle?
The pituitary gland, it stimulates egg ripening and oestrogen production (in ovaries)
Where is oestrogen released and what is its role in the menstrual cycle?
The ovaries, helps the lining of the womb to develop and stimulates pituitary gland to make LH
Where is LH released and what is its role in the menstrual cycle?
The pituitary gland, stimulates egg release and progesterone production in the ovaries
Where is progesterone released and what is its role in the menstrual cycle?
The ovaries, helps the lining of the womb
What do high levels of oestrogen stimulate the release of?
LH
What do high levels of oestrogen inhibit the release of?
FSH
What do high levels of progesterone inhibit the release of?
LH
What does the term contraception mean?
Prevents pregnancy
How does the contraceptive pill work?
Contain oestrogen to inhibit FSH production so that no eggs mature
How do contraceptive implants and injections work?
They slowly release progesterone to inhibit the maturation and release of eggs for a number of months or years
What is a spermicidal agent?
A chemical that kills sperm
Name 2 barrier methods of contraception and say how they work.
The condom, fits over the penis. The diaphragm, covers the cervix in the female and they both and prevent sperm reaching an egg.
What is the coil and how does it work?
It is a device that is place in the uterus, it stops a fertilised egg implanting in the lining
What does abstaining mean?
Avoiding having sex around ovulation
What is in a fertility drug and how does it work?
A drug that contains FSH and LH. FSH stimulates the maturation of the eggs and
LH stimulates the release of the egg
What is IVF?
In vitro fertilisation where an egg is fertilised outside the body in a laboratory
Describe the IVF process.
FSH and LH are given to stimulate the maturation of several eggs. The eggs are collected from the mother and fertilised by sperm from the father in the laboratory. The fertilised eggs develop into embryos. At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb).
Describe some issues with IVF treatment.
It is emotionally and physically stressful with low success rates, increases the risk of complications, may lead to premature or underweight babies and multiple births
What is negative feedback?
It is where a stimulus causes an opposite effect
Where are the adrenal glands?
On top of the kidneys
What is the role of adrenalin?
To prepare the body for rapid activity
Where is the thyroid gland?
In the neck
What is the role of thyroxine?
It regulates the metabolic rate, this is the rate at which energy is released in the body.
What is a stimulus?
Any change in the surroundings
What is a receptor?
Cells that detect a change
Name the two parts of the central nervous system
Brain and spinal cord
What is an effector?
A muscle or gland
What does the CNS coordinate?
The response of effectors
Put these in the correct order: receptor, stimulus, response, coordinator, effector.
stimulus 🡪 receptor 🡪 coordinator 🡪 effector 🡪 response
What is the role of the sensory neurone?
Carry impulses from the receptors to the central nervous system (CNS)
What is the role of the relay neurone?
Connect the sensory neurones to the motor neurones in the CNS.
What is the role of the motor neurone?
Connect the sensory neurones to the motor neurones in the CNS.
What is a synapse?
A gap between two neurones
Describe what happens at the synapse.
An impulse reaches the end of a neurone; neurotransmitter is released across the gap. It then diffuses across the synapse and when it reaches the next neurone this starts another impulse.
Why are reflex actions important?
They protect the body from injury
Recall the pathway of the reflex arc.
receptor 🡪 sensory neurone 🡪 spinal cord 🡪 motor neurone 🡪 effector
