Homeostasis Flashcards
Define homeostasis
The maintence of keeping a constant stable internal environment for cells and to keep enzymes from being denatured
What condition are maintained by homeostasis?
Ph
Amount of water and glucose present in blood
temperature
What two effector systems are there?
Nervous and endocrine system
What are the three components of all control systems
Receptors - detect the change in environment
coordination systems - process the info from receptors and send out an effector
Effector- reverse the actual change in environment
what are the two main effectors and describe them
glands - usually the hormonal or digestive glands send out a slow response
Nerves - electrical impulses through the myelin sheath a fast instant response
what is the function of the nervous system?
allows body to react to stimulant and co ordinate a response
Describe from a stimulus to a response the role of the nervous system
stimulus is picked up by receptors and turned into an electrical impulse
this moves along sensory neruones to the CNS
The relay neruones in the CNS connect the sensory neruones to the motor neruones
the motor neruones carry the impulse to the effector which carry out the response
describe the sequence of events
stimulus - receptor - co -ordinator -effector - response
what is a reflex action?
an automatic and rapid response that doesn’t require the concious brain
describe how a reflex action occurs via a reflex arc
stimulus is detected by receptor
an electrical impulse is sent from the sensory neurones the the CNS
In the synapses between the sensory and relay nerurones a chemical diffuses and stimulates a new impulse across the relay neruones
same happens at the motor neurones
at the effector the appropiate impulse is carried for the response
difference between a reflex pathway and a conscious pathway?
within a reflex pathway the impulse is through a relay neruone in the spinal cord / unconious part of the brain
a concious pathway will use the conscious part of the brain
function of the cebreal cortex?
control’s concious, memory and languge
function of cerebellum?
muscle co-ordination
function of the medulla?
controls the unconcious activites of the brain e.g breathing heart rate
why is study and treatment of the brain so hard?
exact function of each part of brain is not known
brain is very delicate
brain can be easily damaged
certain membranes block drugs from reaching the brain
methods used to determine brain functions?
MRI scans
electrical impulsions
study of patients with brain damage
which stimuli are the eye receptors senstive too?
light intensity and colour
what are the two main functions of eye structures?
to adapt to dim conditions
focusing on near or far objects
describe the strucutre and function of the retina
Retina - light senstivie layer in the back of the eye
Light will stimulate the retina cells resulting in a impulse being sent to the brain (response from muscles being to shut eyes)
What are the 3 ways scientists study the brain?
MRI scans
electrically stimulating the brain
studying patients with brain damage
What are the main functions, eye structures are used for?
Accommodation (focusing on near and far objects)
Adapting to bright and dim light by opening and closing the lens
describe the function of the optic nerve
Connects the brain and eye
carries impulses,
describe the function of sclera?
tough white layer of the eye which protects the eye
describe the function of the cornea?
reflects light and allows it too enter and be focused onto the retina
describe the function of the iris?
Is a muscle that controls the size of the pupil by contracting or relaxing
how does the iris alter the size of the pupil in dim and bright light?
bright light - circular muscles contract and radial muscles contract this makes the pupil smaller
dim light the circular muscles relax and the radial muscles relax dilating the pupil
define accommodation
the alteration of the lens to focus on near and far objects
How does the eye focus on near objects?
Ciliary muscles contract
suspensory ligaments slacken
the lens becomes short and fat
how does the eye focus on far objects?
ciliary muscles loosen
suspensory ligaments relax
the lens become thinner light is refracted weakly
what is myopia?
short sightedness occurs when the lens of the eye is too curved so images will focus in front of the retina
images are blurry
How can myopia be treated?
using concave glasses
what is hyperopia?
Long sightedness is when the lens is too flat so light will focus behind the retina
cure for hyperopia?
Using convex glasses lens which brings the light rays together
How does laser surgery work?
To treat myopia it is used to decrease the size of the cornea so light is refracted less strongly
to treat hyperopia is treats the curavture of the lens
Pro’s and con’s of replacment lens?
Replacements lens will fix the lens
can cause cataracts or blindess due to being so invasive
Where is the body is temperature controlled?
Thermoregulatory centre in the hypothalamus of the brain
Name the 4 hormones needed in the menstrual cycle?
LSH- lutenzing hormone
FSH- follice stimulating hormone
Oestrogen
Proestrogen
What is the purpose of LH?
To stimulate the ovary to relase an egg every month, most highest concentrated when ovulation occurs
What is the purpose of FSH?
This stimulates the eggs in the ovaries to begin to mature and grow.
Purpose of proestrogen?
Maintains the uterine lining after ovulation.
Purpose of oestrogen?
stimulates the start of the uterus lining to build back up again, when it is low the uterus lining breaks down
Name the 3 neruones
Motor neurone, sensory neruone, receptor neurone
What are the two main structures found within the eye?
Focusing on near and far objects (accomodation)
Adaptation to dim light
Describe the function and structure of the cornea?
It is a curved transparent part at the front of the eye that helps to bend and refract light onto the retina
Describe the function and structure of the iris?
Is a muscle that contracts and relaxes to control the size of the pupil, allows eyes to adjust to dim lighting
Describe how the iris alters the size of the pupil in both dim and bright light?
Bright light : the circular muscles contract and the radial muscles relax makes the pupil smaller so less light can enter eye
Dim light: Circular muscles relax and radial muscles contract allowing more light into the eye
How does the eye focus on nearby objects?
cillary muscles contract suspensory ligaments loosen, so the lens becomes more curved so the light rays are refracted strongly
How does the eye focus on far objects?
cillary muscles loosen and suspensory ligaments loosen so the light rays are less refracted
What is myopia?
Myopia (short sightedness)occurs when the lens of the eye is too curved, so the light is focused in front of the retina so objects appear blurry
How can myopia be treated?
Can be treated with a concave lens which spreads out the light rays so they can be focused onto the retina
What is hyperopia?
Hyperopia (long sighted) usually occurs when the lens is too flat so light is focused behind the retina so objects appear out of focus
How can hyperopia be treated?
Hyperopia can be treated with a concave lens which brings the light rays closer together to be focused on the retina
What is laser eye surgery?
This fixes the size of the cornea, in myopia lasers reduce the size of the cornea so light is refracted less strongly
In hyperopia the cornea curvature is changed so the light is refracted more strongly
Where is body temperature controlled?
Body temperature is controlled in the thermoregulatory centre in the brain.
How is temperature measured in the body?
The thermoregulatory centre has receptors in the blood that detect blood temperature
The skin has receptors sensitive to skin temp
How does the body react when the temperature is too high?
Vasodilation- the blood vessels near the surface of the skin dilate, so more heat evaporates away
Sweat - evaporation of water takes away heat energy from the surface of skin
How does the body react when the temperature is too low?
vasoconstriction- The blood vessels at the surface of the skin constrict so less heat evaporates
Shivering - the work your muscles do create heat energy
no sweating
What is the name of the body system that controls hormones?
The endocrine system
What is a hormone ?
Hormones is a chemical messenger released by glands, It travels to the target organ to create a response
What is the master gland?
The pituary gland
What is the role of pituary gland?
Secretes growth hormones - controls human growth
Stimulates the the thyroid glans
stimulates ovulation and oestrogen in the uterus
Role of thyroid gland
To secrete thyroxine which controls metabolism, heart rate and body temperature
What is the role of the pancreas?
To secrete insulin - controls glucose in blood
role of adrenal gland
to secrete adrenaline (ADH) to stimulate fight or flight response
How does the pancreas respond when glucose is low?
Pancreas releases glucagon which binds to the liver receptors making the stored glycogen break down into glucose again
how does the pancreas respond when the glucose levels are too high?
Pancreas secretes insulin which binds to the livers receptors, causing the excess glucose to be stored into the liver as glycgoen
How is blood glucose concentration controlled using a negative feedback loop?
When the blood glucose levels is below or above optimum the pancreas will secrete a hormone
This action will do the opposite to the blood glucose level
what is type 1 diabetes?
An autoimmune disease when the pancreas fails to create enough insulin, so blood glucose levels are dangerously high
How can type 1 be treated?
Insulin injections inbetween meals so the glycogen can be broken into glucose
pancreas and pancreatic cell transplants
what is type 2 diabetes
when the body stops responding to insulin- onset of obesity and age
how is water lost from body?
exhalation
sweat
urine
How are excess amino acids excreted from the body?
The excess amino acids are deaminated in the liver to form ammonia
Ammonia is toxic so is converted into urea
urea is excreted in urine and sweat
How do kidneys balance the amount of water, ions and glucose in the body?
The blood is filtered to remove waste(urea excess ions excess water) and the reabsorp useful molecules
(glucose water and ions)
ADH?
Anti-diuretic hormone
How does ADH affect the reabsorption of water in the kidneys?
When the blood is too low in water more ADH is secreted ADH travels to the bloodstream of the kidneys, this increases the permeability of the kidney tubules so more water is reabsorbed into the blood
Why is kidney failure dangerous?
kidneys will be unable to filter the blood
This will lead to a build of toxic urea
an unbalanced amount of ions and water so osmosis in cells will not be correct
two ways of treating kidney failure?
Dialysis and transplant
what is kidney dialysis
Patient is hooked up to dialysis machine which contains fluids with the same concentration of glucose and ions as healthy blood. So therefore the patients blood will only lose urea and waste only
describe the events of the menstrual cycle
FSH is relased which makes eggs mature in the ovaries
and promotes oestrogen which begins to thicken uterus lining
Oestrogen promotes LH which makes ovulation occur and restricts anymore FSH
Progesterone is secreted from the follicle of the ovary, which maintains the uterus lining and inhibits FSH and LH
How does contraceptive pill stop pregnancy?
Inhibts FSH so eggs do not mature and oestrogen to lining does not thicken
and increases cervical mucus which slows down sperm cells
What is the IUS?
Is a small plastic device inserted into the uterus, so it relases progestogen and stops uterus lining thickening
what is the IUD?
Is a small copper device inserted into the uterus which prevents to implantation of embryos
How do fertility drugs increase the chance of pregnancy?
Contain FSH which promote egg maturtity which stimulate oestrogen production.
They also contain LH which triggers ovulation
What is IVF?
Mother injects FSH and LH
Eggs are collected from the ovary
eggs are fertlised in a petri dish and developed into embryos
the embryo’s are then inserted into the mothers womb
Disadvantges of IVF?
Very expensive
low success rate as you get older
Increased chance of multiple pregnancy which is dangerous for mom
How is the relase of thyroxine controlled by negative feedback?
Thyroxine is a hormone relased by the thyroid gland.it is triggered by the thyroid stimulating hormone. Thyroxine stimulating hormone. when thyroxine is too low TSH is released
what are the effects of adrenaline?
Increased in heart and breathing rate- deilvers more oxygen and glucose to the body
Stored glycogen converted into glucose
dilation of pupils
Blood diverted away from digestive system to muscle
What is a tropism?
A plants response to a stimulus
Phototropism?
Is a plant’s shoots or roots response to light
gravatropism?
A plants response to gravity
Hydrotropism?
A plants response to water
what is auxin?
A hormone that controls the rate of growth and found in the tips of roots or shoots
How do plants show positive phototropsim?
One side of the plant is light causing the auxin to move to the dark side, at the dark side is stimulated to grow. bend towards the light
this means more photosynthesis can occur
what are gibberelins?
A plant hormone that helps with seed germination
what is ethene?
a plant hormone involved in plant ripening
uses of auxin?
Weedkiller- auxins helps plants to grow at a rapid rate causing plant death
Rooting powder- auxins causes a new plant to grow very quickly
Tissue culture - promotes growth of roots and shoots from other plants quickly
uses of gibberelins?
Terminates seed dormancy
Promotion of flowering
Increases of fruit sizes
