homeostasis and response Flashcards
what is homeostasis
homeostasis is the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme and cellular function
give examples of conditions maintained by homeostasis in the body
blood glucose concentration
body temp
water levels
what two types of responses are used in body control systems
nervous and chemical
3 components do all control systems have
receptors
coordination centres
effectors
function of a receptor
receptor detect changes in the environment
function of coordinate centre
coordinate centres obtain and process information from receptors
function of effector
effectors bring about responses to the stimuli
function of nervous system
the nervous system allows the body to react to its surroundings and coordinate an appropriate response
how does a stimulus lead to a response being carried out by the body
- stimulus is converted into an electrical implies by the receptors
- the electrical impulse passes along sensory neuron’s to the central nervous system
- the CNS coordinates an appropriate response and an electrical impulse is sent along motor neuron’s to the effector, which carries out the response
what sequence of events describes how the nervous system works
stimulus, receptor, coordinator, effector, responce
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 aid survival by preventing harm to the body
describe how a reflex action occurs via a reflex arc
- the stimulus is detected by a receptor
- an electrical impulse passes along a sensory neurone to the spinal cord
- at a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
- the same process occurs at a synapse between a relay neurone and a motor neurone
- 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 neurone found in the spinal cord. in a conscious pathway, the coordination centre is in the conscious part of the brain
function of the cerebral cortex
control consciousness, intelligence, memory, and language
function of cerebellum
controls muscular coordination
function of medulla
controls unconscious activities
example of what the medulla controls
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 east function of each part of the brain is not known
what methods are used by scientist to determine brain function?
studying patients with brain damage
electrical stimulation of the brain
MRI scans
what stimuli are the receptor of the eye sensitive too
light intensity
colour
2 main functions of structures found within the eye
focusing on near or distant objects
adaptation to dim light
describe the structure of the retina
the retina is a light sensitive layer found at the back of the eye
describe the function of eye
light stimulates the retinal cells, resulting in impulses being sent to the brain
describe function of the optic nerve
it carries impulses to the brain so that an image can be visualised
describe the optic nerve
the optic nerve connects eye and brain
describe the structure of sclera
the tough outer layer of the eye
function of sclera
protects its internal structures
describe the structure of the cornea
the cornea is the curved transparent layer at the front of the eye
describe the function of the cornea
lets light into the eye and allows light to be focused onto the retina
what is the iris
a muscle which controls the size of the pupil by contracting or relaxing
function of the iris
allows the eye to adjust to bright and dim lighting
function of the ciliary muscles and suspensory ligaments
hold the Len in place and control its shape
describe how the iris alters the size of the pupil in bright light
circular muscles contract and radial muscles relax
makes pupils smaller to avoid retinal damage
describe how the iris alters the size of the pupil in dim light
circular muscles relax and radical 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 nearby objects
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
describe myopia
myopia usually occurs when the lens of the eye is too curved
as a result the light is focused in front of the retina so images appear blurry
what is myopia
short sightedness
how can myopia be treated
myopia can be treated using glasses with a concave lens
which spreads out light rays so they can be focused on the retina
what is hyperopia
long sightedness
describe hyperopia
occurs hen the lens is to flat, as a result, light is focused behind the retina so images appear out of focus
how can hyperopia be treated
can be treated using glasses with a concave lens, which brings the light rays together so they can be focused on the retina
2 types of contact lenses
hard: rigid material, long lasting, must be kept sterile
soft: flexible material, short lasting, more comfortable
what is laser eye surgery
laser eye surgery is the use of lasers to fix visual defects in adults,
to treat myopia, lasers reduce the thickness of the cornea so light is refracted less strongly
to treat hyperopia, lasers alter the curvature of the cornea so that light is refracted correctly
how can replacement lenses be used to treat visual defects
a replacement lens can either be implanted into the eye or it may replace the natural lens all together.
disadvantage to replacement lens
risk of lens replacement include retinal damage, cataracts, or infections
where is body temp controlled in the body
body temp is controlled by the thermoregulatory centre in the hypothalamus of the brain
how is temp monitored by the body
thermoregulatory centre has receptors sensitive to blood temp
skin has receptors sensitive to skin temp - so sends impulses to the thermoregulatory centre
what physiological changes occur when the body temp 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 temp is too low
vasoconstriction: blood vessels near the surface of the skin constrict - less heat radiated away
shivering: respiration allows muscles to contract. an exothermic process, so heat energy is released
sweating stops
give the name of the body 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 pituitary gland considered a master gland
it secrets a wide range of hormones some of which may stimulate other endocrine glands
what is the role of the pituitary gland in the endocrine system
- secrets human growth hormone, controls human growth
- stimulates the thyroid gland
- stimulates ovulation and the production of oestrogen in the ovaries
- stimulates 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 temp
what is the role of the pancreas in the endocrine system
secrets the hormone insulin, controls blood glucose levels
what is the role of the adrenal gland in the endocrine system
secretes adrenaline, controls the body’s “fight or flight” response
what is the role of the ovaries in the endocrine system
secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics
what is the role of the testes in the endocrine system
secrete testosterone, which coordinates the production of sperm and the development of male secondary sexual characteristics
which organ monitors and 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 the muscles, causing excess glucose to be converted into glycogen and stored
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.
how is blood glucose concentration controlled using a negative feedback loop
when the blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas
the action of either hormone helps bring back the concentration to the correct level.
what type one diabetes
type one diabetes is an autoimmune disorder in which the pancreas does not produce sufficient, insulin to control the blood glucose concentration. as a result, blood glucose levels are often very high, leading to excessive urination, tiredness and weight loss
how can type one diabetes be treated
insulin injections before meals, allows glucose to be converted into glycogen.
limiting carbon dioxide intake
attempts using pancreas and pancreatic cell transplants, investigations into genetic engineering of pancreatic cells
what is type 2 diabetes
type 2 diabetes is a disorder in which the body cells stop responding to insulin, leading to an unrolled blood glucose concentration. its onset is linked with increasing age and obesity
how can type 2 diabetes be treated
following a carefully controlled diet
doing regular exercise
loosing weight
use of drugs which increase insulin production and effectiveness
what is osmosis
osmosis is the movement of water from a diet solution to a concentrated solution through a partially permeable membrane
in what ways is water lost 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
excess amino acids are deaminated in the liver to form ammonia
ammonia is toxic, therefore it is converting into urea
urea is excreted from the body via sweat and urine
how do the kidneys maintain the balance of water and other substances in the body
filter blood in order to remove waste products
selectively reabsorb useful molecules
why is kidney failure dangerous
when the kidneys are damaged, they may be unable to filer the blood properly, this could lead to:
- a build-up 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
transplate
what is kidney dialysis
kidney dialysis is the use of specialist machine to carry out the function of kidneys. dialysis fluid contains the same concentration of glucose and ions as healthy food. as result, only excess and water molecules are lost from the blood, and glucose and ions remain
what is function of reproductive hormones during puberty
males: cause the development of secondary sexual characteristics
females: cause the development of second sexual characterises an the maturation of eggs
what is the main male reproductive organ
testosterone
produced by the testes and controls sperm production
main female reproductive hormone
oestrogen
produced in the overrates 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 ovulating
describe the events of the menstrual cycle
- uterus lining thickens and eggs begin to mature in the ovaries
- an egg is released from one of the ovaries, uterus lining remains thick
- if the egg is fertilised, pregnancy may occur. if not both the egg and uterus lining are shed during menstruation
what is ovulation
ovulation is the release of a mature egg from the ovaries, which occurs ever 28 days, approx
4 main hormones involved in the menstrual cycle
oestrogen
progesterone
follicle stimulating hormone
luteinising hormone
what is the role of FSH is the menstrual cycle?
FHS is secreted by the pituitary gland
it controls the maturation of eggs within the ovaries and triggers the production of oestrogen by the ovaries.
what is the role of oestrogen in the menstrual cycle?
oestrogen is produced by the ovaries and released due to the action of FSH - it causes the re-growth of the uterus lining
it triggers the production of LH and restricts the release of more FSH
what is the role of LH in the menstrual cycle
LH is produced in the pituitary gland as a result of oestrogen.
its release triggers ovulation
what is the role of progesterone in the menstrual cycle
progesterone is secreted from the follicle of the ovary. it sustains the uterus lining and inhibits FSH and LH
what is contraception
contraception refers to any method of preventing pregnancy
2 types of oral contraceptives
combined contraceptive pill
mini pill
what does the combined contraceptive pill contain
contains oestrogen and progesterone
what does the mini pill contain
only progesterone
how does the contraceptive pill prevent pregnancy
- inhibits FSH, eggs do not mature
- prevents the development on the uterus lining, eggs cannot implant
- increases the thickness of cervical mucus, immobilise sperm cells
what does the contraceptive patch contain
contains both oestrogen and progesterone
what is the contraceptive implant
a small rod inserted under the skin which continuously releases the hormone progesterone
what is the contraceptive injection
an injection containing the hormone progesterone
how long does the contraceptive injection last
3 months
how long does the contraceptive patch last for
for 7 days at a time
how long does the contraceptive injection last for
3 years
what is the IUS
the IUSE is a small plastic device that is inserted into the uterus
releases progesterone which thickens cervical mucus and prevents the build-up of the uterine lining
what is the IUD
the IUD is a small copper-containing device inserted into the uterus, which prevents the implantation of embryos
what is a spermicide
a spermicide is a chemical that kills or immobilises sperm cells
what is the issue with a spermicide
not very effective
work better when combined with other barrier methods
define barrier method of contraception
a barrier methods of contraception involves a physical separation between the sperm and the egg
examples of barrier methods of contraceptions
condoms
diaphragms
what is a condom
huh
thin sheath worm on the penis or inside the vagina, protects against STI’s but may tear
what is a diaphragm
(Monica friends)
a thin cap placed over the cervix, preventing entry of sperm
what surgical methods of contraception are available
(chop chop)
sterilisation in males - the sperm ducts are tied together
a vasectomy
and
in females, the oviducts are tied
what is abstinence
abstinence is the practice of not having sex, helps avoid pregnancy
some people abstain from sex around the time of ovulation
how do fertility drugs increase the chance of pregnancy
many fertility drugs contain FSH, which stimulates oestrogen production and the maturation of eggs in the ovary. the also contain LH which triggers ovulation
what is IVF
a type of fertility treatment
mother is given FSH and LH - stimulates maturation of eggs and ovulation
eggs are fertilised using sperm in a lab, developed into embryos
1 or 2 embryos inserted into the mother womb
advantages of the fertility treatment
- allows infertile couples to have children
- can store a women’s eggs for later
disadvantage of fertility treatment
- very expensive
- low success rate
- increases chance of multiple pregnancies, dangerous for mothers and babies
- side effects of fertility drugs
what is negative feedback
negative feedback is a type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level
why is thyroxine
thyroxine is a hormone is released by the thyroid gland. its release is triggered by the thyroid stimulating hormone. thyroxine controls the body’s metabolic rate, growth and development
how Is the release of thyroxine controlled by negative feedback
- levels of blood thyroxine falls, detects by receptors in the brain
- puituaity gland releases more TSH
- more thyroxine produced and released by thyroxine gland
- blood thyroxine levels return to normal
what is adrenaline
adrenaline is a hormone secreted by the adrenal gland in time of stress, responsible for flight or fight responses
effects of adrenaline
- increased heart rate and breathing rate
- stored glycogen converted to glucose
- dilation of pupils
- increased mental awareness
- blood diverted away from digestive system to muscles
what is a tropism
a tropism is the response of a plant to a specific stimulus
what is phototropism
phototropism is the response of a plants shoot or root to light
what is gravitropism
gravitropism is the response of a plants shoot or root to gravity
what is auxin
auxin is a hormone which controls growth of a plant roots and shoots. when auxin in unevenly distributed in a growing plant, the growth of the plant will be unequal
how do plants shoots show positive phototropism
one side of the shoot is in the light, causing to move to the shaded side
at the shaded side, the cells are stimulated to grow - the shoot bends towards the light
as a result, photosynthesis can occur at a faster rate
how do plant shoots show negative gravitropism
in a horizontal shoot, auxin accumulates in the lower side due to gravity
cells on the lower side of shoot grow more, 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 cels to grow less
the root bends in the direction of gravity
as a result, more water and nutrients are available to the plant roots
what are gibberellins
gibberellins are a type of plant hormone involved in seed germination
what is ethene
ethene is a type of plant hormone involved in cell division and ripening
what are the uses of auxins
weedkillers - causes cells to grow at a rapid rate, causing plant death
rooting power - causes new plant to grow very quickly
tissue culture - promotes growth of roots and shoots
uses of ethene
control of food ripening in the food industry
allows fruit to be ripened just before they are sold
uses of gibberellins
termination of seed dormancy
promotion of flowering
increase fruit size
components of the CNS
spinal cord
brain
what are synapses
synapses are gaps between neurons and can be found at each junction of a reflex arc
what are neurotransmitters
chemicals that diffuse across synapses and bind to receptors on the next neurone
what is a reflex arc
a reflex arc is the unconscious response that allows a person to respond to a dangerous situation automatically and rapidly via a reflex arc
what type of signal are neurotransmitters
chemical
