homeostasis and response Flashcards
What is homeostasis?
Maintenance of a constant internal environment in order to maintain optimum conditions for enzymes and cellular function
Give examples of conditioned maintained by homeostasis in the body
blood glucose concentration
Body temperature
Water levels
What two types of responses are used in body control systems?
Nervous and chemical
What 3 components do all control systems have?
receptors
Coordination centres
effectors
what is the function of a receptor?
Receptors detect changes in the environment
What is the function of a coordination centre?
Coordination centres obtain and process information from receptors
what is the function of an effector
Bring about response to stimuli
What is the function of the nervous system?
The nervous system allows the body to react to its surroundings and coordinate an appropriate response
How does a stimulus lead to response being carried out by the body?
stimulus is converted into an electrical impulse by the receptors
The electrical impulse passes along century neurons to the central nervous system
The CNS coordinate an appropriate response and an electrical impulse is sent along motor neurons to the effector, which carries out the response 
what sequence of events describes how the nervous system works? 
stimulus——>receptor——->coordinator——>effector——>response
what is a reflex action?
A reflex action is an automatic and rapid response, which does not involve any conscious input from the brain
why are reflex actions important?
Reflex actions a survival by preventing harm to the body
describe how reflex action occurs via a reflex arc
The stimulus is detected by a receptor
An electrical impulse passes along a sensory neuron to the spinal cord
At a pace between a sensory neuron and a relay neuron, a chemical diffusers across the gap and stimulates a new impulse which passes along the relay neurone
The same process occurs at a centipedes between a relay neuron and motor neuron
At the effector an appropriate response is carried out
What is the difference between a reflex pathway and a conscious pathway?
Within a reflex pathway, the coordination centre is a relay neuron found in the spinal cord unconscious parts of the brain. In a conscious pathway, the coordination centre is the conscious part of the brain.
What is the function of the cerebral cortex?
Controls consciousness, intelligence, memory and language
What is the function of the cerebellum?
Controls muscular coordination
what is the function of the medulla
Controls unconscious activities, e.g. breathing, heart rate
why is the investigation and treatment of the brain difficult?
The brain is a complex and delicate organ
The brain is easily damaged and destroyed
Certain membranes prevent drugs from reaching the brain
The exact function of each part of the brain is not known
what methods are used by scientists determine brain function?
Studying patients with brain damage
Electrical stimulation of the brain
MRI scans
what stimuli are the receptors of the is sensitive to?
Light intensity and colour
What are the two main functions of structures found within the eye?
focusing on near or distant objects
Adaptation to dim light
describe the structure and function of the retina
The retina is a light sensitive layer found at the back of the eye
light stimulates the retinal cells, resulting in impulses being sent to the brain 
describe the structure and function of the optic nerve
The optic nerve connects the eye and the brain
It carries impulses to the brain so that an image can be visualised
describe structure and function of the sclera
the sclera is the tough outer layer of the eye which protects its internal structures
Describe the structure and function of the cornea
The cornea is the curved transparent layer at the front of the eye
It lets light into the eye and allows light to be focused on to the retina
describe the structure and function of the iris
The iris is a muscle which controls the size of the pupil by contracting or relaxing. This allows the eye to adjust to the bright and dim light.
describe the structure and function of the ciliary muscles and suspensory ligaments 
the ciliary muscles and suspensory ligament hold the lens in place and control its shape
Describe how that iris alters the size of the pupil in both bright and dim light
bright light: circuit muscles, contract and radial muscles relax – makes pupil smaller to avoid retinal damage
dim light: circuit muscles relax and radio muscles contract – makes pupil larger so more light can enter the eye
what is accommodation?
Accommodation is the alteration of the lens shape in order to focus on near or distant objects
how does the eye focus on a nearby object?
ciliary muscles contract
suspensory ligaments loosen
lens becomes thicker and more curved -light rays are refracted strongly
How does the eye focus on a far away object?
ciliary muscles relax
suspensory ligaments tighten
lens becomes thinner -light rays are refracted weakly
what is a myopia
Usually occurs when the lens of the eye is too curved. As a result, light is focused in front of the retina and show images of blurry.
how can myopia be treated
using glasses with a concave lens, which spreads out light rays so they could be focused on the retina
what is hyperopia
usually occurs when the lens of the eye is too flat. As a result, the light is focused behind the retina so images appear out of focus. 
how can hyperopia be treated
using glasses with a convex lens, which brings the light raises together so they can be focused on the retina
what are the two types of contact lenses?
hard – rigid material, last long time, must be kept sterile
Soft – flexible material, last short time, more comfortable
What is a laser eye surgery?
laser eye surgery is the use of lasers to fix defects in adults.
To treat myopia, laser reduce the thickness of the cornea so light is refracted less strongly.
The treat hyperphoria lasers alter the curvature of the so that light is refracted correctly. 
how can replacement lenses be used to treat visual defects?
Replacement implanted into the eye or it may replace the natural lens altogether. Risk of the reliance replacement include retinal damage cataracts, and infection.
What are the risk of lens replacement?
Retinal damage, cataracts, and infections
where is the body temperature controlled in the body?
Body temperature is controlled by the Thermo regulator centre in the hypothalamus of the brain
how is the temperature monitored by your body?
Thermo regulator centre has receptors sensitive to blood temperature
Skin has receptor sensitive to skin temperature – send impulses to Thermo regulator
What physiological changes occur when the body temperature is too high?
vasodilation – blood vessels near the surface of the skin dilate –more heat is radiated away
Sweating – evaporation of water takes away heat energy from the surface of the skin
What physiological changes occur when the body temperature is too low?
vasoconstriction-blood vessels near the surface of the skin constrict – less heat radiated away
Shivering – respiration allows muscles to contract. It is an exothermic process, so he energy is released.
Sweating stops
give the name of the bodies coordination system which involves hormones
The endocrine system
what is a hormone?
A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ, where it causes a response.
what type of organ secretes hormones
Glands
Which gland controls many other glands in the body?
the pituitary gland
why is the pitunitary gland considered a master gland
it secrets a wide range of hormones,some which may stimulate other endocrine glands
What is the role of the pitcunitary gland in the endocrine system?
secretes human growth hormone – controls human growth
Stimulates the thyroid gland
Stimulates the ovulation and the production of oestrogen in the ovaries
The production of sperm and testosterone in the testes
What is the role of the thyroid gland in the endocrine system?
Secretes the hormone thyroxine – controls metabolism, heart rate and body temperature
what is the role of the pancreas in the endocrine system?
Secretes the hormone insulin – controls blood glucose levels
what is the role of the adrenal gland in the endocrine system?
Secrets adrenaline – controls the body flight or fight response
What is the role of the ovaries in the endocrine system?
Secret oestrogen, which coordinates the mental cycle and the development of female secondary sexual characteristics
what is the role of the testes in the endocrine system?
Secretes testosterone, which coordinates the production of sperm and the development of a male secondary sexual characteristics
which organ monitoring controls blood glucose concentration?
The pancreas
How does the pancreas respond when blood glucose levels are too high?
The pancreas secretes the hormone insulin. Insulin binds to receptors on the liver and muscles, causing access glucose to be converted into glycogen installed.
How does the pancreas respond when blood glucose levels are too low
The pancreas secretes the hormone glucagon. Glucagon binds to liver cells, causing glycogen to be converted into glucose and released into the blood.
Blood glucose concentration controlled using a negative feedback loop
when the blood glucose concentration rises and falls below the optimum, a hormone is secreted by the pancreas
The action of either hormone insulin or glucagon helps bring back the concentration to the correct level
what is type one diabetes?
Type one diabetes is an autoimmune disorder in which the parent does not produce sufficient insulin to control the blood glucose concentration. As a result blood glucose levels are often very high to, leading to excessive urination, tightness and weight loss
how can type one diabetes be treated?
Insulin injections before meals – allows glucose to be converted into glycogen
Limiting carbohydrate intake
Attempts using pancreas and pancreatic cell transplant: investigations into genetic engineering of pancreatic cells
What is type two diabetes?
Type two diabetes is a disorder in which the body cells stop responding to insulin, leading to an uncontrolled blood glucose concentration. Its answer is linked with increasing age and obesity.
how can type two diabetes be treated?
Following a careful controlled diet
Doing regular exercise
Losing weight
Use of drugs which increase in insulin production and effectiveness
in what ways is water loss from the body?
During exhalation via the lungs
Sweating
Urine
In what ways are ions lost from the body?
sweating
Urine
how are excess amino acids excreted from the body?
Access amino acids are deaminated in liver to form ammonia
ammonia is toxic, therefore it is converted into urea
Urea is excreted from the body via sweat and urine
how do kidneys maintain the balance of water and other substances in the body?
Filter blood in order to remove waste products, e.g. urea
Selectively reabsorb useful molecules e.g. glucose, water, ions
What is the full name of the hormone ADH?
anti-diuretic hormone
where isADH secreated in the body?
The pituitary gland
how does ADH affect the absorption of water in the kidneys?
When the blood is too concentrated, the pituitary gland secretes more ADH
ADH travels into the blood trim to the kidneys and increases the permeability of kidney tubules to water
More water is reabsorbed in the kidneys resulting in a smaller volume of more concentrated urine
 why is kidney failure dangerous?
when the kidneys are damaged, they may be unable to fill other blood properly. This may lead to:
A buildup of toxic molecules in the body
An uncontrolled ion and water balance and cells being damaged as a result of osmosis
What are two main ways of treating kidney failure?
Dialysis and transplant
what is kidney dialysis?
Kidney dialysis is the use of a specialist machine to carry out the function of kidneys.
Fluid contains the same concentration of glucose and ions as a healthy blood
As a result, only excess and waste molecules are lost from the blood and glucose and irons remain
what is the main function of reproductive hormones during puberty?
Males: characterised development of secondary sexual characteristics
Females: causes the development of secondary sexual characteristics and the maturation of eggs
What is the main male reproductive hormone
Testosterone which is produced by the testes and control sperm production
What is the main female reproductive hormone?
Easter room which is produced by the ovaries and is involved in the menstrual cycle
what is the menstrual cycle?
is the monthly cycle of physiological changes that occur in females, involving the shedding of the uterus lining and ovulation
describe the events of the menstrual cycle
Uterus lining thickens and eggs begin to mature in the ovaries
an egg release from one of the ovaries – uterus lining remains thick
If the egg is fertilised pregnancy may occur if not both the egg and the uterus lining are shed during menstruation
what is ovulation?
Ovulation is the release of a mature egg from the ovaries which occurs approximately every 28 days
name the four main hormones involved in the menstrual cycle
Oestrogen
Progesterone
Follicle stimulation hormone FSH
luteinising hormone LH
What is the role of FSH in the mental cycle?
FSH is secreted by the pit gland. It controls the maturation of eggs within the ovaries and triggers the production of eastern by the ovaries.
What is the role of oestrogen in the menstrual cycle?
Oestrogen is produced by the ovaries and is released due to the action of FSH – it causes the regrowth of the uterus lining
Production of LH and restrictive release of more FSH
What is the role of LH in the menstrual cycle?
LH is produced in the pit territory gland as it result of oestrogen it’s release triggers ovulation
What is the role of progesterone in the menstrual cycle?
progesterone is secreted from the molecule of the ovary. It sustained the uterus lining and inhibits FSH and LH
What are the two types of oral contraceptives?
combined contraceptive pill – contains oestrogen and progesterone
Mini pill – contains only progesterone
How does the contraceptive pill prevent pregnant pregnancy?
inhibit FSH – eggs do not mature
Prevents the development of the uterus learning – eggs cannot implant
Increases the thickness of cervical mucus – immobilises sperm cells
What is the contraceptive patch?
contains both oestrogen and progesterone
It is a patch that is placed onto the skin for seven days at a time
what is the contraceptive implant?
A small rod inserted under the skin which continuous releases the hormone progesterone – last three years
What is the contraceptive injection?
An injection containing the hormone progesterone – last for approximately three months
What is the iUS
Is a small plastic device that is inserted into the uterus. It releases progesterone which thicken cervical mucus and prevents the buildup of the uterine lining.
what is the iud
Small copper containing device inserted into the uterus, which prevents the implantation of embryos
What is spermicide?
A chemical that kills are immobilised sperm cells – however they are not very effective and work better when combined with barrier methods
what is a barrier method of contraception?
Condoms
Diaphragms
what surgical methods of contraception are available?
Sterilisation – in males are sperm ducks are tied and in females oviducts are tied
What is abstinence?
The practice of not having sex, which also avoid pregnancy. Some people abstain from sex around the time of ovulation – this is known as The Rhythm Method.
how do you fertility drugs increase the chance of pregnancy?
Many fertility drug contain FSH – which stimulates oestrogen production and the maturation of eggs in the ovary. They also contain LH which triggers ovulation.
what is IVF?
Mother is given FSH and LH – in maturation of eggs and ovulation
eggs are fertilised using sperm in a laboratory – develop into embryos
One or two embryos are inserted into the mother’s womb
what are the advantages of fertility treatment?
Allows infertile couples to have children
Can store women’s eggs for later
what are the disadvantages of fertility treatment?
It can be very expensive process
It has low success rate – especially for older couples
Increases chance of multiple pregnancies – dangerous for mother and babies
Side effects of fertility drugs
What is negative feedback?
Negative feedback is a type of control whether the body responds to an increase or decrease in a factor by returning it to optimum level
What is thyroxine?
thyroxine is a hormone released by the thyroid gland. It’s release is triggered by the thyroid stimulation hormone. Thyroxine controls the body metabolic rate growth and development.
how is the release of thyroxine controlled by negative feedback?
levels of blood thyroxine falls – detected by receptors in the brain
pituitary gland releases more TSH
more thyroxine produced and released by thyroid gland
blood thyroxine levels return to normal
What is adrenaline?
Adrenaline is a hormone secreted by the adrenaline and gland in times of stress it is responsible for the fight or flight response
What are the effects of adrenaline?
increases in heart and breathing weight – delivers oxygen and glucose to the body
Stored glycogen converted into glucose
Dilation of pupils
Increased mental awareness
Blood diverted away from digestive system to muscles
what is tropism?
Response of a plant to specific stimulus
What is phototropism?
phototropism is the response of a plant shoot or root to light
what is gravitopism
The response of a plant shoot or root to gravity
what is auxin
Hormone which controls the growth of a plant shoots or roots when oxygen 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 light, causing auxin to move to the shaded side
at the shaded side, the cells are stimulated to grow – the shoot bends towards a light
As a result, photosynthesis can occur faster rate
how do plant shoots show negative gravitropism
In a horizontal shoot, auxin accumulate in the lower side due to gravity
cells on the lower side of shoot grower causing the shoot to bend away from the direction of gravity
As a result, more light is usually available for photosynthesis
how do plant roots show positive gravitropism
in a horizontal root ,auxin accumulates in the lower side, causing cells to grow less
The root bends in direction of gravity
As a result, more water and nutrients are available to the plant roots
what are gibberellins
type of plant hormone involved in seed germination
What is ethene
Type of plant hormone involved in cell division and ripening
what are the uses of auxins
Weed killer – causes cells to grow at a rapid rate, causing plant death
Rooting powder – causes new plant to grow very quickly
Tissue culture – promotes growth of roots and shoots
what are the uses of ethene
Control of food ripening in the food industry – allows fruit to be ripen just before they are sold
what are the uses of gibberellins
termination of seed dormancy
Promotional flowering
Increase of fruit size
