Topic 5-Homeostasis Flashcards
what is homoeostasis
homeostasis is the regulation
of the internal conditions of a cell or organism to maintain optimum
conditions for function in response to internal and external changes.
what does homeostasis maintains optimal conditions for
enzyme action and all cell
functions.
what does homeostasis control in the human body
blood glucose concentration
body temperature
water levels.
what three things does the automatic control system contain
effectors, receptors and the co ordination centre
what do receptors do
detect stimuli (changes in the environment)
give examples of co ordination centres
(such as the brain, spinal cord and pancreas)
what do co ordination centres do
receive and process information from receptors
what do effectors, muscles or glands do
bring about responses which
restore optimum levels.
what is negative feedback
a mechanism where your auto matic control systems keep your internal environment stable
what does stimuli mean
change in the environment
whats the difference between multicellular and single celled organisms in terms of response
single celled organisms can just respond to its environment bu the cells of multi cellular organsims need to communicate with each other first
what does the nervous system mean for humans
that they can react to their surroundings and co ordinate their behaviour
what is the CNS and what does it consist of
CNS- central nervous system- recieves info from the receptors and then coordinates a response
vertebrates- brain and spinal cord
mammals- CNS is connected to the body by sensory neurons and motor neurons
what are sensory neurons
neurons that carry info as electrical impulses from the RECEPTORS to the CNS
what are motor neurons
the neurons that carry electrical impulses from the CNS to the EFFECTORS
what are effectors
all your muscles and glands which respond to nervous impulses
explain the order of the body’s response to a stimulus
Stimulus receptor sensory neuron CNS motor neuron effector response
what is a synapse
the connection between two neurons
how is the nerve signal transferred
by chemicals that diffuse across the gap
what do the chemicals between the gap in the neurons do
set off a new electrical signal in the next neuron
what are reflexes
Reflex actions are automatic and rapid; they do not involve the conscious part of the brain
whats a reflex arc
the passage of information in a reflex (from receptor to effector)
what does the refelx arc pass through
the CNS (spinal chord or unconscious part of the brain)
what happens in the reflex arc
a stimulus (eg. bee sting) is detected by the receptors
impulses travel along a sensory neuron
chemicals are passed, causing an impulse to be passed along a synapse from the sensory neuron to the relay neuron
impulses are passed along the synapse to the motor neuron in the same way
impulses travel form motor neuron to the effector
the muscle contracts and moves the hand away from the bee
what does the brain do
controls complex behaviour
It is made of billions of interconnected neurones
has different regions that carry out different functions.
name three parts of the brain
cerebral cortex
medulla
cerebellum
what does the medulla do
controls unconscious activities
eg, breathing and your heartbeat
what does the cerebral cortex do
(outer wrinkly bit)
responsible for things like consciousness, intelligence memory and language
what does the cerebellum do
responsible for muscle coordination
what three things can a scientist do to study the brain and map out which bit does what
studying patients with brain damage
electrically stimulating the brain
MRI scans
how can studying a patient with brain damage help discover more about the brain
Eg. if an area at the back of the brain was damaged by a stroke and the patient went blind you know that that area has something to do with vision.
how does electrically stimulating the brain help scientists
by pushing an electrode into the tissue of the brain and giving it a small zap of electricity, the scientist can observe what stimulating different parts does
how do MRI scans help scientists discover about the brain
find out which parts are active when people are doing different things
what are some consequences of treatment of brain damage or disease
physical damage to the brain
increased problems with brain function
what is the eye
a sense organ containing receptors sensitive to light intensity and colour.
that is the sclera
the tough supporting wall of the eye
what is the cornea
the transparent outer layer
at the front of the eye
it refracts (bends) light into the eye
what is the iris
contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye
what is the lens
focuses the light onto the retina
which contains receptor cells sensitive to light intensity and colour
the shape of the lens is controlled by…
the ciliary muscles and suspensory ligaments
what does the optic nerve do
carries impulses from the receptors on the retina to the brain
what does the iris reflex mean
adjusting for bright light
what happens when light receptors in the eye detect a very bright light
the circular muscles in the iris contract and the radial muscles relax - pupil gets smaller
this reduces the amount of light that can enter the eye
what happens to the eye in dim light
radial muscles contract
circular muscles relax
pupil gets wider
more light can get into the eye
what is accomodation
the process of changing the shape of the lens to
focus on near or distant objects.
To focus on a near object what happens to the eye
- the ciliary muscles contract
- the suspensory ligaments loosen
- the lens is then thicker and refracts light rays strongly.
To focus on a distant object what happens to the eye
- the ciliary muscles relax
- the suspensory ligaments are pulled tight
- the lens is then pulled thin and only slightly refracts light rays.
what is short sightedness called
myopia
what is long sightedness called
hyperopia
what does my/hyper opia mean for the eye
rays of light do not focus on the retina.
what is long sighted-ness and how does it occur
unable to focus on near objects
occurs when lens is wrong shape and doesn’t refract light enough, or eyeball is too short
SO the images of near objects are brought to focus behind the retina
how can L sightedness be fixed
use glasses with a convex lens (curves outwards)
lens refracts the light rays so they focus on the retina
what is short sighted-ness and how does it occur
unable to focus on distant objects
occurs when lens is wrong shape and refracts the light too much or the eye ball is too long
SO the images of distant objects is brought into focus in front of the retina
how can S sightedness be fixed
use glasses with a concave lens (curves inwards) so that the light rays focus on the retina
name three treatments for vision defects
contact lenses, laser eye surgery and replacement lens surgery
what do contact lenses do
thin lenses that are thin and compensate for fault in focusing
lightweight and almost invisible
hard and soft lenses
soft- more comfy but carry a higher risk of infection
what does laser eye surgery do
laser vaporises tissue which changes the shape of the cornea, which changes how strongly it refracts light into the eye
slimming down=less powerful= improve short sight
more powerful= improves long sight
risks= infection, bad reaction
explain what replacement lens surgery is
long-sightedness treated by replacing lens of the eye
risks- damage to retina- loss of sight
which hormones control blood glucose levels
insulin and glucagon
where is body temperature is monitored
its monitored and controlled by the thermoregulatory
centre in the brain
what does the thermoregulatory centre contain
receptors
sensitive to the temperature of the blood
what does the skin contain
temperature receptors which send nervous impulses to the thermoregulatory centre.
what happens if the body temperature is too high
blood vessels dilate (vasodilation)
sweat is produced from the sweat glands
both these mechanisms
cause a transfer of energy from the skin to the environment.
plus hairs stand flat
what happens if the body temperature is too low
blood vessels constrict (vasoconstriction)
sweating stops
skeletal muscles contract (shiver)
hairs stand up
how does sweat cool you down
its produced by sweat glands
it evaporates from the skin
this transfers energy to the environment
how does vasodilation help cool down the body
the blood vessels dilate so more blood flows closer to the skin
this helps transfer energy from the skin to the environment
how does hairs standing up help you warm up
trap an insulating layer of air
how does vasoconstriction help you warm up
blood vessels constrict to close off the skins blood supply
how does shivering help you warm up
your muscles contract automatically
this needs respiration which transfers some energy to warm the body
what is the endocrine system
The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream
how are hormones carried around the body
The blood carries the hormone to a target organ where it produces an effect.
which has longer effects, the nervous system or the hormonal system
nervous system has
fast action
act for a short time
very precise area
endocrine system
slower action
act for a longer time
act in a more general way
what does the pituitary gland do
a ‘master gland’ which secretes
several hormones into the blood in response to body conditions.
These hormones in turn act on other glands to
stimulate other hormones to be released to bring about effects.
what do the ovaries do
produce oestrogen- involved in the menstrual cycle
what do the testes do
produce testosterone- controls puberty and sperm production
what does the thyroid do
produces thyroxine- regulates metabolism, heart rate and temperature
what does the adrenal gland do
produces adrenaline- prepares body for fight or flight response
what does the pancreas do
produces insulin which is used to regulate the blood glucose level
Blood glucose concentration is monitored and controlled by…
the pancreas
If the blood glucose concentration is too high, what happens
The pancreas produces the hormone insulin that causes glucose to move from the blood into the cells
what happens to excess glucose in the liver and muscle cells
it’s converted to glycogen for storage.
what happens when the blood glucose level is too high
insulin is secreted by the pancreas
insulin enters the liver and makes it turn glucose into glycogen
glucose moves from the blood into the liver and muscles cells
BLOOD GLUCOSE IS REDUCED
what happens when the blood glucose level is too low
glucagon is secreted by the pancreas
glucagon enters the liver and makes it turn glycogen into glucose
glucose is released into blood by the liver
BLOOD GLUCOSE IS INCREASED
what is type 1 diabetes
Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin
what is type 2 diabetes
In Type 2 diabetes the body cells no longer respond to insulin produced by the pancreas
how is type one diabetes characterised
by uncontrolled high blood glucose levels
how is type one diabetes treated
normally treated with insulin injections.
how is type two diabetes charictarised
can cause persons blood sugar levels to rise to a dangerous level
how can type two diabetes be treated
by having a carbohydrate controlled diet and an exercise regime
what’s a risk factor for type two diabetes
obesity
how do the kidneys make urine
by filtration of the blood and selective
reabsorption of useful substances such as glucose, some ions and
water.
what does filtration do
filters substances out of the blood as they pass through the kidneys
what is selective re absorption
when useful substances like glucose, some ions and the right amount of water are absorbed back into the blood
name three substances that are removed from the body in urine
water, urea and ions
what happens to proteins and the amino acids that they are broken down into in the liver?
they cant be stored by the body, so any excess amino acids are converted into fats and carbohydrates, which can be stored- involves a process called deamination
what happens to ammonia in the liver?
ammonia is produced as a waste product from deamination
its toxic so is converted to urea in the liver
urea is then transported to the kidneys where it’s filtered out of the blood and excreted from the body in urine
how do ions enter the body
ions, such as sodium are taken into the body via food and then absorbed into the blood
how does water leaves the body
via the lungs during exhalation
how are water, ions and urea lost
from the skin in sweat.
what is there no control over the loss of
water, ion or urea loss by the lungs or skin
Excess water, ions and urea are removed via what
the kidneys in the urine.
what happens if body cells lose or gain too much water by osmosis
they do not function efficiently
where is ADH released
released into the blood stream by the pituitary gland
what is the concentration of urine controlled by
a hormone called anti-diuretic hormone (ADH)
what does the brain do for the water content of the body
the brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed.
what happens if the water content increases
a receptor in the brain detects it’s too high
the coordination centre in the brain receives the info and coordinates a response.
the pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules
what happens if the water content decreases
a receptor in the brain detects this
the coordination centre receives this and coordinates a response
the pituitary gland releases more ADH, so more water is reabsorbed from the kidney tubules
what happens if the kidneys dont work properly
waste substances build up in the blood and you eventually lose your ability to control the levels of ions and water in your body
results in death
what is a dialysis machine
a machine which the person’s blood flows between partially permeable membranes, surrounded by dialysis fluid.
whats a dialysis machine permeable to
ions and waste substances, but not big molecules like proteins
whats the concentration like of dissolved ions and glucose like in the dialysis fluid and why?
its the same concentration as healthy blood
this means it wont be lost from the blood during dialysis
which substances diffuse across the barrier in dialysis
urea and excess ions and water
advantages of dialysis treatment
can buy a patient with kidney failure valuble time until a donor organ is found
disadvantages of dialysis treatment
not pleasant
time consuming (3-4 hours) three times a week
dialysis may cause blood clots or infection
expensive for the NHS to run
what is the only cure for kidney failure at the moment?
kidney transplant
whats a risk of kidney transplant and how is it prevented
donor kidney can be rejected by the patient’s immune system
treated with drugs to try and prevent it, but can still happen
advantages for kidney transplants
cheaper in the long run than dialysis
no hours sat at machine
disadvantage to kidney transplants
there is a long waiting list
During puberty reproductive hormones cause what
secondary sex characteristics to develop.
what happens in stage one of the menstrual cycle
menstruation starts- the uterus lining breaks down for about four days
what happens in stage two of the menstrual cycle
the uterus lining builds up again, from day 4 to 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
what happens in stage three of the menstrual cycle
an egg develops and is released from the ovary at day 14- ovulation
what happens in stage four of the menstrual cycle
the wall is then maintained for about 14 days until day 28. if no fertilised egg has landed on the uterus wall by day 28, spongy lining starts to break down and process starts again
name the four hormones that control menstruation
FSH, oestrogen, LH and progesterone
what does FSH do
Follicle-stimulating hormone- FSH
causes egg to mature in one of the ovaries in a structure called a follicle
stimulates the ovaries to produce oestrogen
what produces FSH
the pituitary gland
where is oestrogen produced
ovaries
what does oestrogen do
causes the lining of the uterus to grow
stimulates the release of LH and inhibits the release of FSH
what produces LH
pituitary gland
what does LH do
stimulates the release of an egg at day 14 (ovulation)
what does progesterone do
maintains the lining of the uterus during the second half of the cycle.
when the level of progesterone falls, the lining breaks down
inhibits the release of LH and FSH
where is progesterone produced
ovaries by the remains of the follicle after ovulation
name hormonal contraception methods and what they do
oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature
injection, implant or skin patch of slow release progesterone to inhibit
the maturation and release of eggs for a number of months or years
intrauterine devices which prevent the implantation of an embryo or
release a hormone
name barrier methods of contraception
spermicidal agents which kill or disable sperm
condoms and diaphragms which prevent the
sperm reaching an egg
name other methods of contraception
abstinence- when an egg may be in the oviduct
surgical methods of male and female sterilisation.
how can fertility be increased using hormones
giving FSH and LH in a ‘fertility drug’ to a woman
advantages of the FSH and LH drug
helps a lot of women to get pregnant when they previously couldnt
disadvantages of the FSH and LH drug
• it is very emotionally and physically stressful
• the success rates are not high
• it can lead to multiple births which are a risk to both the babies and
the mother.
what happens in IVF
- mother given FSH and LH 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).
pros to IVF
can give an infertile couple a child
cons of IVF
multiple births can happen
low success rate- 26%
stressful and upsetting
strong reaction to the hormones- eg. abdominal pain, vomiting, dehydration
what have developments of
microscopy techniques done
enabled IVF treatments to develop.
why are some people against IVF
results in unused embryos that are eventually destroyed- unethical- destroying a life
preferred characteristics
when and where is adrenaline produced
produced by the adrenal glands in times of fear or stress.
what does adrenaline do
it increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’.
where is thyroxine produced
thyroid gland
what does thyroxine do
stimulates the basal metabolic rate and plays an important role in growth and development
why do plants produce hormones
to coordinate and control growth and
responses to light (phototropism) and gravity (gravitropism or geotropism)
what does unequal distributions of auxin cause
unequal growth rates in plant roots and shoots
