B5 - Homeostasis and Response Flashcards
What is homeostatis?
Maintaining a stable environment for optimum conditions for enzyme and cellular functions.
What 3 conditions are maintained by homeostasis?
Water content.
Body temperature.
Blood glucose levels.
Why are control systems needed?
To ensure conditions in your body remain stable even when the external envrionment changes.
What 3 things are needed in control systems?
Receptor
Co-ordination centre
Effector
What organ helps to control body temperature?
Liver controls metabolic reactions so the amount of heat energy transferred to environment is controlled.
What is negative feedback?
Opposing the change.
What is positive feedback?
Acts to amplify or encourage the change e.g. when a mother breastfeeds her child, the more milk she produces.
Why is feedback important in control systems?
To make adjustments and maintain optimum conditions in an organism.
What is the temperature regulation centre in the brain called?
Hypothalamus
What are the body’s responses to an increase in temperature?
Sweat produced - evaporation of water takes away heat energy from the surface of the skin.
Vasodilation meaning more heat is radiated away.
What are the body’s responses to a decrease in temperature?
Muscles contract rapidly - respiration allows muscles to contract. It is an exothermic process so energy released raises body temperature.
Vasoconstriction - less heat radiated away.
Sweating stops.
What is thermoregulation?
The control of body tempertaure.
What temperature do enzymes work best at?
37 degrees celcius
What is the CNS?
Central Nervous System
What are neurones?
Cells that transmit electrical impulses around the nervous system.
Which neurones carry electrical impulses from the receptors to the CNS?
Sensory neurones.
Which neurones carry electrical impulses from the CNS to the effectors?
Motor neurones.
What is a relay neurone?
Sends information from one neurone to another.
What is another term for neurones?
Nerve cells
What 3 things make up the nervous system?
Brain, spinal cord, neurones
What does the CNS consist of?
Brain and the spinal cord.
What does the peripheral nervous system consist of?
Neurones
What are receptors?
Groups of specialised cells that detect changes in the environment, called stimuli, and turn them into electrical impulses.
Where are recepetors often located?
In the sense organs - skin, eye and ear.
What are effectors?
Produce a response.
What is a coordination centre?
Obtain information from the recpetors.
What is the name of the microscopic gap between neurones?
Synapses
How are electrical impulses transmitted?
A chemical (a neurotransmitter) diffuses across the synapse to stimulate a second neurone.
What is a reflex action?
A rapid, automatic response to a stimulus.
Give 4 examples of reflexes performed by the human body and why this reflex is important.
Blink reflex - prevents eye getting damaged
Knee reflex - walking/running
Ankle reflex - walking/running
Pupil reflex - prevents damage from bright light
What is an advantage of the spinal cord being a coordination centre?
Reactions are quicker as shorter pathway between sensory neurone and spinal cord.
How does a stimulus lead to a response being carried out by the body?
- receptor (in skin of finger / hand)
detects stimulus - electrical impulses pass along
neurones - impulses pass from sensory to
relay to motor neurones - synapse between neurones
where chemical crosses gap
(synapses) in spinal cord / CNS - muscle contraction to pull hand
away effector is a muscle
What is the difference between a reflex pathway and a conscious pathway?
Within a reflex pathway, the co-ordination centre is a relay nuerone found in the spinal cord or unconscious part of the brain.
Within a conscious pathway, the co-ordination centre is in the conscious part of the brain.
What is the order of events in a reflex arc?
Stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response
What is accomodation?
The alteration of the lens’ shape in order to focus on near or distant objects.
What are the two main functions of all the structures found within the eye?
Focusing on near and distant objects.
Adapting to light.
What is the function of the retina?
Where light is focused.
Contains photoreceptive cells which detect colour and light intensity.
What is the function of the pupil?
The hole that allows light to enter the eye.
What is the function of the optic nerve?
Carries electrical impulses from the eye to the brain.
What is the function of the sclera?
The tough supporting wall of the eye.
What is the function of the cornea?
Transparent outer layer found at the front of the eye. Refracts light into the eye.
What is the function of the lense?
Focuses light onto the retina.
What is the function of the ciliary muscles?
Muscles connected to the lens by the suspensory ligaments.
Control the shape of the lens.
What is the function of the suspensory ligaments?
Connect the ciliary muscles to the lens and hold the lens in place.
Control the shape of the lens.
What happens to the ciliary muscles and suspensory ligaments when the object is near?
Ciliary muscles contract.
Suspensory ligaments slacken.
What is the shape of the lens when an object is near?
Curved, fat.
What is the muscle tension on the lens when an object is near?
Low.
What is the effect on the refraction of the light when the object is near?
Refracts light more.
What happens to the ciliary muscles and suspensory ligaments when the object is far?
Ciliary muscle relaxes.
Ligaments pull on lens.
What is the shape of the lens when an object is far?
Flat, thin
What is the muscle tension on the lens when an object is far?
High
What is the effect on the refraction of the light when the object is far?
Refracts light less.
What is the action of the circular and radial muscles in dim light? (the iris)
Circular muscles relax.
Radial muscles contract.
What is the action of the circular and radial muscles in bright light? (the iris)
Circular muscles contract.
Radial muscles relax.
Why is the constriction of the pupil important?
It avoids retinal damage.
Why is the dilation of the pupil important?
Allows more light to enter the eye.
What is myopia?
Short-sightedness. Usually occurs when lens is too curved and as a result light is focused in front of the retina.
How can myopia be treated?
Use of a concave lens, which spreads out light rays so they can be focused on the retina.
What is hyperopia?
Long-sightedness. Occurs when the lens is too flat and light is not refracted enough so light is focused behind the retina.
How can hyperopia be treated?
With a convex lens. Which brings the light rays together so they can be focused on the retina.
What are the two types of contact lens?
Hard - rigid material, long-lasting, must be kept sterile
Soft - flexible material, last a shorter amount of time, more comfortable
What is laser eye surgery?
Use of lasers to fix visual defects in adults.
What is done in laser eye surgery to treat myopia?
Lasers reduce the thickness of the cornea so light is refracted less strongly.
What is done in laser eye surgery to treat hyperopia?
Alters the curvature of the cornea so light is refracted more strongly.
How can replacement lenses be used to fix visual defects?
A replacement lens can either be implanted into the eye along with the natural lens. Or replace the lens altogether.
What are the risks of lens replacement?
Retinal damage, cataracts, infection.
How is temperature monitored by the body?
Thermoregulatory centre has receptors sensitive to blood temperature.
Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory centre.
What is a tropism?
Response of a plant to a specific stimulus.
What is phototropism?
Response of a plants shoot or root to light.
What is gravitropism?
Response of a plants shoot or root to gravity.
What is auxin?
A hormone which controls the growth of a plant’s shoot and roots. When auxin is unevenly distributed in a growing plant the rate of growth will be unequal.
What happens when an auxin is unevenly distributed in a growing plant?
The rate of growth will be unequal.
How do plant shoots show positive phototropism?
One side of the shoot is in the light, causing auxin to move to the shaded side.
Cells are stimulated to grow at the shaded side. Shoot bends towards the light.
How do plants show negative gravitropism?
Auxin accumulates in the lower side due to gravity.
Cells on the lower side grow more, causing the shoot to bend away from the direction of gravity.
How do plant roots show positive gravitropism?
Auxin accumulates in the lower side causing cells to grow less. The root bends in the direction of gravity.
How to plants benefit from positive gravitropism?
More water and nutrients are available to plant roots.
How do plants benefit from positive phototropism?
Photosynthesis occurs at a faster rate.
What are gibberellins?
Type of plant hormone involved in seed germination.
What is ethene?
Type of plant hormone involved in cell division and ripening.
3 uses of auxins.
Weed killers - cause cells to grow at a rapid rate causing death.
Rooting powder - causes new plant to grow very quickly.
Tissue culture - promotes growth of roots and shoots.
State a use of ethene.
Control of food ripening in the the food industry - allows them to be ripened just before they are sold.
3 uses of gibberellins.
Termination of seed dormancy.
Promotion of flowering.
Increase of fruit size.
How is temperature monitored by the body?
Thermoregulatory centre has receptors sensitive to blood temperature
Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory centre.
Why are reflex actions important?
Aid survival by preventing harm to the body.
What is the function of the cerebral cortex?
Controls consciousness, intelligence, memory and language.
What is the function of the cerebellum?
Controls muscular co-ordination.
What is the function of the medulla?
Controls unconscious activities e.g. breathing, heart rate.
Why is investigation and treatment of the brain difficult? (4)
Brain is complex.
Brain is easily damaged.
Certain membranes prevent drugs from reaching the brain.
The exact function of each part of the brain is not known so surgery is difficult.
What 3 methods are used by scientists to determine brain function?
Studying patients with brain damage.
Electrical stimulation of the brain.
MRI scans.
What stimuli are the receptors of the eye sensitive to?
Light intensity and colour.
What is the function of the nervous system?
Allows the body to react to it’s surroundings and coordinate an appropriate response.
What is the function of the iris?
Muscle that controls the size of the pupil by contracting or relaxing. Allowing the eye to adjust to bright and dim lighting.
What 2 types of responses are used in body control systems?
Nervous and chemical.
What 2 things can the hypothalamus control?
Body temperature
Water levels in blood
What is the function of the pituitary gland?
Produces many different chemicals (hormones) which help control body systems.
What is the brain stem?
The primitive part and controls basic functions that keep you alive.
Is the cerebral cortex found in every animals brain?
No, only found in highly intelligent animals.
What are insulin and glucagon?
Hormones produced by the pancreas that regulate glucose levels in the blood.
What is the difference between glucose and glycogen?
Glucose is a simple sugar which is a monomer, glycogen is a polymer of glucose and is a storage molecule found in animals.
What response does the pancreas perform when blood glucose is too high?
Pancreas secretes insulin into blood, insulin binds to liver and muscle cells, causing excess glucose to be converted into glycogen and stored.
What response does the pancreas perform when blood glucose is too low?
Glucagon is secreted into blood. Glucagon binds to liver cells, causing glycogen to be converted into glucose and released into blood.
What is the effect on the liver and muscle when glucose levels are too high?
Glucose in blood moves into liver and muscle, where it is converted into glycogen for storage.
What is the effect on the liver and muscle when glucose levels are too low?
Glucose is not converted into glycogen by liver and muscle.
Liver converts glycogen into glucose.
Why is glucose converted into glycogen?
Glucose means that lots of water travels into the cells and they can die. Glycogen doesn’t effect osmosis.
How does type 1 diabetes occur?
When the body doesn’t produce insulin or enough insulin.
How does type 1 diabetes effect your physical appearance?
No stores of glycogen - meaning you are underweight.
How is type 1 diabetes treated?
Insulin injections before meals.
Limiting carbohydrate intake.
Pancreas and pancreatic cell transplants.
What 2 factors effect how much insulin a person with type 1 should take?
How much they have eaten - more insulin needs to be injected
How much they have exercised - less insulin needed to be injection (as muscles take in more glucose when exercising)
What is type 2 diabetes?
When the body cells stop responding to insulin, so the cells won’t take glucose in from the blood stream, leading to an uncontrolled glucose concentration.
Why does type 1 diabetes lead to weight loss?
Insufficient insulin, prevents glucose from going into cells to release energy, so the body starts using fat and muscle stores.
What are the risk factors of type 2?
Age and obesity.
How is type 2 treated?
Losing weight
Exercising more.
Controlled diet.
Drugs which increase insulin effectiveness.
Why is blood glucose concentration part of the negative feedback loop?
The action of the secreted hormone will bring blood glucose levels back to a normal concentration. Opposes the change.
What are 4 symptoms of type 1?
Frequent urination.
Thirst.
Tiredness.
Weight loss.
What age group is type 1 diagnosed at?
Childhood - teenagers.
What age range does type 2 usually become diagnosed?
Over 40.
What do MRI scans enable scientists to do?
To link the loss of a certain function with a particular region of the brain.
Where are amino acids broken down?
Liver.
Why is a decrease in body temperature beneficial to animals during hibernation?
Loses less energy.
Body energy store lasts longer.
Why does an animal have a higher body temperature when it is active?
Activity requires energy from respiration.
Respiration releases heat which increases body temperature.
Why does the dilation of blood vessels in the skin decrease body temperature?
More blood flow near the surface of the skin.
More heat is lost.
Cools blood which cools the body.
What is the name of the coordination system involving hormones?
Endocrine system
What type of organ secretes hormones?
Glands
What gland controls many other glands in the body?
Pituitary gland
Why is the pituitary gland referred to as the master gland?
Secretes a wide range of hormones, some of which stimulate other endocrine glands.
4 roles of pituitary gland.
- Secretes growth hormones
- Stimulates thyroid gland
- Stimulates ovulation and oestrogen.
- Stimulates production of sperm and testosterone.
What is the role of the thyroid gland?
Secretes hormone thyroxine - controls metabolism, heart rate and temperature.
What is the role of the pancreas?
Secretes insulin - controls blood glucose levels.
What is the role of the adrenal gland?
Secretes adrenaline - fight or flight response.
What is the role of the ovaries?
Secretes oestrogen - which co-ordinates the menstrual cycle and controls female sexual characteristics.
What is the role of the testes?
Secretes testosterone - coordinates sperm and male characteristics.
Where is ADH secreted?
Pituitary gland.
In what ways is water lost from the body?
Sweating
Urine (some reabsorbed by kidney)
Exhalation
In what ways are ions lost from the body?
Sweating
Urine (some reabsorbed by kidney)
How are excess amino acids excreted from the body?
Deaminated in liver to form ammonia.
Ammonia converted into urea
Urea excreted via sweat and urine.
How do kidneys maintain the balance of water and other substances in the body?
Filter blood to remove urea.
Reabsorb useful molecules e.g. glucose ions water.
What does ADH control?
The water content of blood.
How does the body respond to too little water in blood?
Releases more ADH.
More water absorbed by kidneys.
Less water lost in urine.
Blood water level returns to normal.
How does the body respond to too much water in blood?
Releases less ADH.
Less water absorbed by kidneys.
More water lost in urine.
Blood water level returns to normal.
What are the effects of adrenaline?
Increase in heart and breathing rate.
Dilation of pupils
Glycogen converted to glucose.
Blood diverted to muscles.
What is thyroxine’s releases stimulated by?
TSH - thyroxine stimulating hormone released by pituitary gland.
Why is kidney failure dangerous?
Unable to filter blood properly leads to:
Build up of toxic chemicals - urea
An uncontrolled ion and water balance
State 2 ways of treating kidney failure.
- Dialysis
- Transplant
What is the function of reproductive hormones during puberty?
Males - sexual characteristics
Females - sexual characteristics and maturation of eggs.
Main male reproductive hormone.
Testosterone
Main female reproductive hormone.
Oestrogen
Describe events of menstrual cycle.
- Uterus lining thickens and eggs mature in ovaries
- An egg is released, lining remains thick
- If egg is fertilised pregnancy may occur, if not both egg and uterus lining are shed during mensturation.
What is ovulation?
Release of a mature egg from the ovaries - every 28 days
Name 4 main hormones in the menstrual cycle.
- Oestrogen
- Progesterone
- FSH
- LH
What is the role of FSH?
Secreted by pituitary gland.
Controls the maturation of eggs.
Triggers the production of oestrogen.
What is the role of oestrogen?
Causes regrowth of uterus lining.
Triggers production of LH.
Stops release of more FSH.
What is the role of LH?
Triggers ovulation.
What is the role of progesterone?
Secreted from follicle of ovary.
Sustains uterus lining and inhibits FSH and LH.
What is adrenaline?
Hormone secreted in the adrenal gland in times of stress.
How is the release of thyroxine controlled by negative feedback?
Receptors detect low levels in the blood.
Pituitary gland releases more TSH.
More thyroxine produced by Thyroid gland.
Blood thyroxine returns to normal.
Name 4 hormones released in the menstrual cycle.
- FSH (follicle stimulating hormone)
- LH (luteinizing hormone)
- Oestrogen
- Progesterone
What gland is FSH and LH released from?
Pituitary gland.
What gland is oestrogen and progesterone released from?
Ovaries
What is the function of FSH?
Causes egg cell to mature in ovaries. Stimulates ovaries to release oestrogen.
What is the function of LH?
Causes mature egg cell to be released. Stimulates release of progesterone.
What is the function of progesterone?
Maintains the uterus lining.
What is the function of oestrogen?
Causes uterus lining to thicken. Inhibits FSH and promotes LH.
What does the pill contain?
Oestrogen and/or progesterone.
How does the pill prevent pregnancy?
Prevents egg cell maturing and being released.
What are the cons of the pill?
Doesn’t protect against STD’s.
Increased risk of breast cancer.
Headaches and nausea.
What is a intrauterine device?
T-shaped device inserted into uterus.
How does a intrauterine device prevent pregnancy?
Kills sperm
Prevents implantation of a fertilised egg cell.
What does the plastic version of a intrauterine device do?
Release progesterone.
What is the only contraceptive method that protects against STD’s?
Condoms
What are the cons of condoms?
Can let semen through if damaged.
What are diaphragms?
Prevents sperm passing through the cervix.
What do diaphragms have to be used with?
Spermicide.
What does surgical contraception involve?
Cutting or tying the fallopian tubes or sperm ducts.
What are the cons of tying the fallopian tubes or sperm ducts?
Chance they will re-join naturally.
Doesn’t prevent against STD’s.
How long is the menstrual cycle?
Around 28 days.
When is a woman most fertile?
Around ovulation (day14). Fertilisation must take place in the fallopian tube.
What is ovulation?
When an egg cell is released from the ovaries.
What is a natural contraceptive method?
Avoiding intercourse when the egg may be in the fallopian tubes. (rhythm method)
What are the cons of the rhythm method?
Unreliable.
Doesn’t protect against STD’s.
What can women take when they have low levels of hormones?
FSH and LH to stimulate ovulation.
What are the pros of taking hormones to stimulate ovulation?
Help people get pregnant.
Non-invasive in tablet form.
What are the cons of taking hormones to stimulate ovulation?
Doesn’t always work - might need to be repeated - expensive.
Too many eggs released results in multiple pregnancies.
Which system are your kidney’s part of?
Excretory system / urinary system
What is the function of the kidneys?
Control water balance.
Remove toxic substances.
Control balance of salts.
Where is ADH secreted?
Pituitary gland.
What does ADH actually do to the kidney tubules that allows it to absorb more water?
It increases the permeability of the tubules.
What is kidney dialysis?
Use of specialist machinery to carry out function of the kidneys.
What does dialysis fluid contain?
Same concentration of ions and glucose as the blood, so only waste molecules are lost from the blood through osmosis.
What is urea?
A waste product.
Made in liver through deamination.
Why is water regulation important?
Cells could swell and burst if water levels are too high.
Shrink if water levels are too low.
Explain how filtration in the kidneys work.
Tubules absorb anything small e.g. water, glucose, amino acids, and urea.
Doesn’t absorb large molecules.
What is selective reabsorbtion?
When all of glucose, some water (and useful molecules) are aborsbed back into blood)
What is the hypothalamus job in water regulation?
Detects water levels in blood stream.
What type of system regulates water content levels?
Negative feedback system
How many adrenal glands are there?
2
Where are the adrenal glands located?
Above each kidney
3 ways the CNS is different to the endocrine system.
CNS triggers rapid and short response
CNS uses electrical signals carried by neurones - Endocrine uses hormones carried by blood
CNS acts on very precise part of the body - endocrine targets larger area of body
What are hormones?
Chemical messages
What is a neurotransmitter?
Chemical involved in passing nerve impulses from one nerve cell to the next across a synapse.
What is the function of the iris?
Controls how much light enters the pupil.
