Unit 5 - homeostasis and response Flashcards
What is homeostasis
Regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
What do the automatic control systems in the body involve
Either nervous system or hormones
Features of an automatic control system
Receptor cells, coordination centre, effector
Function of receptor cells
Detect changes in the environment either internal (concentration of glucose in the blood) or external (temperature of the skin)
What is a stimulus
A change to the environment
Example of a coordination centre
Brain, spinal cord or pancreas
Function of the coordination centre
Receives and processes information from the receptors
What is an effector
A muscle or a gland
Function of the effector
Carry out the response (restore the optimum level), either a muscle contract or a hormone is secreted from a gland
2 parts of the nervous system
-The central nervous system (brain and spinal cord)
-other nerves running to and from the central nervous system
What is a neurone
A nerve cell= carry electrical impulses when stimulated
Process of when you touch a hot object
- The stimulus is detected by a receptor (in this case the stimulus is heat and the receptor is the skin)
- Electrical impulses pass from a receptor along a sensory neurone to the central nervous system
- At the synapse of the sensory neurone a chemical is released
- This chemical now diffuses across to a relay neurone in the CNS where it triggers an electrical impulse
- The impulse now passes across the relay neurone and reaches another synapse
- Once again a chemical is released which triggers and electrical impulse in a motor neurone
- The impulse moves down the motor neurone to an effector (muscle )
- The muscle now contracts and pulls the hand away from the heat this is the response
Characteristics of reflexes
No decision making by conscious part of brain
Automatic
Rapid
What are the 3 different neurones
Sensory neurones
Relay neurones
Motor neurones
Function of sensory neurones
carry electrical signals - nerve impulses - towards the central nervous system (spinal cord and brain). The signal starts in a receptor which detects a change.
Function of a relay neurones
-carry nerve impulses within the central nervous system, connects sensory to motor neurones
-only used in reflex actions and it replaces the CNS
Function of motor neurones
carry nerve impulses away from the central nervous system. The neurone ends in either a muscle or gland, which are effectors.
Function of cerebral cortex
Language , memory and consciousness
Function of the cerebellum
Controls our balance and coordination of our movements
Function of the medulla
Controls our breathing and heart rate
Why is studying the brain difficult
-brain is protected by the skull so it is very tricky to access
-the structures of the brain are complex so it’s difficult to work out which part of the brain carries out specific functions
-brain is extremely delicate and easy to damage
3 ways scientists use to investigate the brain
-look at patients who have suffered brain damage by looking at where damage has taken place they can try work out that part of the brains function
- electrically stimulate different parts of the brain and look at effects on person behaviour
-use MRI scanning to look at which part of the brain are most active during different activities
What type of organ is the eye
A sense organ (contain receptors sensitive to both light intensity and colour of light)
Function of the cornea
It refracts light into the eye
It is transparent so allows light through
What is the iris
The coloured part of the eye in the pupil, controls the size of the pupil
Function of the lens
Focus the light rays onto the retina
It can change its shape allowing us to focus on distant or near objects (this is called accommodation)
Function of the retina
Contain receptor cells for light
These receptor cells allow us to detect light intensity and light colour
They then send the impulses down the optic nerve to the brain
What is the sclera and function
The white part of the eye, this tough outer structure protects the eye
Function of ciliary muscle and suspensory ligaments
Allow us to focus on distant or near objects
What happens to your pupil when you enter a dark room
Amount of light entering eye is low
This drop in light intensity is sensed by light receptors in the retina
These send electrical impulses to the brain
The brain then sends impulses to specific muscles in the iris
These muscles contract causing the pupil to become larger
What does homeostasis control
-blood glucose concentration
-body temp
-water levels
What is a synapse
Connection between two neurones
Features of a neurone and adaptations
-Long fibre (axon) which is insulated by a fatty sheath, they are long so can carry messages and up and down the body
-Tiny branches (dendron ) which branch further, these receive incoming impulses from other neurones
What is the CNS
the brain and spinal cord
Function of the CNS
coordinates the response of effectors which may be muscles contracting or glands secreting hormones
Why are reflex actions important
Essential to survival of many organisms, prevent injuries
How does an electrical impulse in one neurone pass to another neurone
When electrical impulse reaches the end of the neurone it stimulates the release of a chemical. The chemical diffuses across the synapse to activate an electrical impulse to the next neurone
Reflex that occurs when the eye adjusts to bright or dim light
-when light receptors in the eye detect very bright light a reflex is triggered which makes the pupil smaller
-muscles in the iris contract reduces light that can enter the eye
-the opposite process happens in dim light
-the muscles relax which makes the pupil wider
Evaluate benefits and risks of procedures carried out on the brain and nervous system
Risks = The brain is extremely delicate and hard to access because of the skull.; accidental damage could lead to speech or motor issues, or changes to personality which are permanent, or side effects.
The brain is extremely complex, don’t fully understand how it works, making procedures difficult.
Benefits = improve someone’s quality of life, MRI scans can produce a detailed picture of the brains structures. Scientists can then see what parts of the brain are most stimulated when a patient is doing something, allowing them to further understand the brain’s complex structure. Scientists can pin specific regions to functions.
What does the eye do for focus on near objects
-ciliary muscles contract so they have smaller diameter
-suspensory ligaments loosen
-lens then thickens and refracts light rays strongly
-light rays are then focused on retina
What does the eye do to focus on distant objects
-ciliary muscles relax
-suspensory ligaments are pulled tight
-lens is then pulled thin and only slightly refracts light rays
What is accommodation to do with the eye
process of changing the shape of the lens to focus on near or distant objects
What are two common defects of the eyes
myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina.
How to fix long and short sightedness
-Generally these defects are treated with spectacle lenses which refract the light rays so that they do focus on the retina.
-New technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea and a replacement lens in the eye.
How do contact lenses work
They float on the surface of the cornea. They work like spectacle lenses, by focusing and refracting the light.
What does long sighted mean in terms of the eye
-unable to focus on near objects
-lens is in the wrong shape and does not refract the light enough or the eyeball is too short
-you use glasses with convex lens to correct it as this helps refract the light rays so they focus on the retina
What does short sighted mean in terms of the eye
-unable to focus on distant objects
-lens is wrong shape and refracts light too much or the eyeball is too long
-use glasses with concave lens to correct it so that the light rays can focus on the retina
What is body temperature monitored and controlled by
The thermoregulatory centre in the brain
What is optimum temperature for enzymes to work in body
37 degrees
Function of thermoregulatory system
Contains receptors which are sensitive to the temperature of the blood
Receives nervous impulses from the skin (which also contains temperature receptors)
What happens if body temperature is too high
blood vessels dilate (vasodilation) so more blood slows close to surface of the skin and sweat is produced from the sweat glands. Both these mechanisms cause a transfer of energy from the skin to the environment.
Hairs also lie flat
What happens if body temperature is too cold
blood vessels constrict (vasoconstriction) to close off skins blood supply to skin, sweating stops and skeletal muscles contract (shiver).
Hairs stand up to trap an insulating layer of air
Function of the optic nerve
Carries impulses from the receptors on the retina to the brain
Describe the principles of hormonal coordination and control by the human endocrine system
-is composed of glands which secrete chemicals called hormones directly into the blood stream
-the blood carries the hormone to a target organ where it produces an effect
Similarities and differences between the nerves and the hormones
Nerves = very fast, act for short time , act on very precise area
Hormones = slower action, act for long time, act in a more general way
Function of the pituitary gland
-In the brain, known as the ‘master gland’
-secretes 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.
Function of the thyroid
Produces thyroxine which is involved in regulating things like rate of metabolism, heart rate and temperature
Function of the adrenal gland
Produces adrenaline which is used to prepare the body for a ‘fight or flight’ response
Function of the pancreas
Produces insulin which is used to regulate the blood glucose levels
Function of the ovaries
Produces oestrogen which is involved in the menstrual cycle
Function of the testes
Produce testosterone which controls puberty and sperm production in males
What does the endocrine system do
composed of glands which secrete chemicals called hormones directly into the bloodstream. The blood carries the hormone to a target organ where it produces an effect.
What part of the body monitors and controls blood glucose concentration
-by the pancreas
What happens if blood glucose concentration is too high
- the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells
-liver and muscle cells then convert excess glucose to glycogen for storage
What happens if blood glucose levels are too low
-glucagon is added
-this makes liver turn glycogen into glucose
-glucose then released into blood by liver
What is type 1 diabetes and how is it treated
-pancreas fails to produce sufficient insulin
-It is characterised by uncontrolled high blood glucose levels-
-is normally treated with insulin injections mainly at mealtimes which makes sure glucose is removed from the blood once food has digested
-could also limit the intake of simple carbs and take regular exercise
What is type 2 diabetes and how is it treated
-person becomes resistant to their own insulin produced by the pancreas
-cause a persons blood sugar levels to rise dramatically
-being overweight can increase your chances of developing this as obesity is a risk factor
-can be controlled by eating a carbohydrate controlled diet and regular exercise
-sometimes is inherited
explain the effect on cells of osmotic changes in body fluids
-if the water concentration is too low outside compared to the inside of the cells, water will leave by osmosis
-the cells may shrivel
-If body cells lose or gain too much water by osmosis they do not function efficiently
Function of kidneys (to do with selective reabsorption)
-make urine by taking waste products out of your blood
-helps filter substances out of that blood as it passes through
-useful substances like glucose, some ions and the right amount of water are then re absorbed back into the blood
How is water lost from the body
-urine from the kidneys
-sweat from the skin (also lose ions and urea)
-water vapour from the lungs
There is no control over water, ion or urea loss by the lungs and the skin
How and why is urea excreted from the body?
-proteins (and amino acids they have broken down into) cannot be stored by the body
-so any excess amino acids are converted into fats and carbs which can be stored
-this occurs in the liver and is called deamination
-ammonia is produced as a waste product
-ammonia is toxic and so is immediately converted to urea for safe excretion
What hormone controls the concentration of urine and where is it released from and how do your body know when to release it
Anti diuretic hormone = ADH
Pituitary gland
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 water content in blood is too high
-receptor in the brain detects water content is too high
-coordination centre in the brain receives information and coordinates a response
-pituitary gland releases less ADH is less water reabsorbed from kidney tubules
What happens if blood water content levels are too low
-receptor in brain detects that the water content is too low
-coordination centre in the brain receives information and coordinates a response
-pituitary gland releases more ADH so increased permeability of tubules so more water reabsorbed from kidney tubules
Ways to treat kidney failure
Organ transplant or by using kidney dialysis
How does dialysis work
-the persons blood flows through the partially permeable membrane surrounded by dialysis fluid
-the dialysis has the same concentration of dissolved ions and glucose as healthy blood
-this means that useful dissolved ions and glucose won’t be lost from the blood during
-only waste substances such as urea and excess ions and water will diffuse across the barrier
Advantages and disadvantages of dialysis
A= can buy a patient valuable time until a donor organ is found, removes harmful and waste substances
D= has to be done regularly 3-4 times a week and each session is 3-4 hours, expensive for NHS to run, may cause blood clots or infections, must limit their salt and protein intake between sessions
Why do people do dialysis
Keep concentration of dissolved substances in the blood at normal levels and remove waste substances and excess water
Advantages and disadvantages of kidney transplants
A= transplants are cheaper than dialysis (in the long run), recipient can lead a normal life afterwards (don’t have to watch what they eat or drink)
D= must take immune suppressant drugs which increase risk of infection, shortage of organ donors, only last 8-9 years, any operation carries risk
How does information passes across a synapse
Chemical passes across synapse to next neurone to stimulate electrical impulse
Main male reproductive hormone, where is it produced and what is its function
Testosterone
Produced by testes
Stimulates sperm production
During puberty reproductive hormones cause what to develop
Sex characteristics
Main female hormone, where is it produced and function
Oestrogen
Produced in the ovary
Stimulates the release of the egg (ovulation)
Hormones involved in the menstrual cycle of a woman and their function
-FSH
-LH
-oestrogen
-progesterone
What are the 4 stages of the menstrual cycle
Stage 1 - menstruation starts, uterus lining breaks down for about 4 days
Stage 2 - uterus lining builds up again from days 4 to 14 into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
Stage 3- egg develops and is released from the ovary at day 14 (ovulation)
Stage 4- wall is then maintained from days 14-28, if no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down and the cycle repeats
Where are all the hormones involved in the menstrual cycle produced
FSH= Pituitary gland
Oestrogen = ovaries
LH= pituitary gland
Progesterone = ovaries
Role of FSH in the menstrual cycle
-causes an egg to mature in one of the ovaries in a structure called a follicle
-stimulates the ovaries to produce oestrogen
Role of oestrogen in the menstrual cycle
-causes the lining of the uterus to grow
-stimulates the release of LH
-inhibits the release of FSH
Role of LH in the menstrual cycle
-stimulates the release of an egg at day 14 (ovulation)
Role of progesterone in the menstrual cycle
-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
Types of hormonal contraceptives
-the pill
-contraceptive patch
-contraceptive implant
What does the pill do and Advantages and disadvantages of the pill
Contains oestrogen and progesterone, inhibits production of FSH
A= 99% effective, makes bleeding lighter, can reduce acne
D= side effects like headache, nausea and high blood pressure, doesn’t protect against STIs, tablets must be taken same time every day
What is a hormone
A chemical messenger
How are hormones transported to their target organs
In the bloodstream
What is the IUD (coil) and advantages and disadvantages of it
Small plastic/ metal implant which is placed in uterus this stimulates an ovary and prevents an egg from being released
A= works immediately, can stay in place for 10 years
D= inserting can be uncomfortable, periods can be longer and more painful
What is the contraceptive patch and advantages and disadvantages of it
Release progesterone to inhibit the maturation and release if eggs
A= lower hormone dosage so less side effects, can make bleeding lighter and reduce acne
D= visible and have to change weekly, can cause similar side effects to pill ( headaches, high blood pressure), no STI protection
What is the contraceptive implant and advantages and disadvantages of it
release progesterone to inhibit the maturation and release of eggs
A= lasts up to 3 years, fertility returns to normal as soon as it’s taken out
D= period may be irregular or stop altogether, small surgical procedure to have it fitted and removed, no STI protection
Types of non hormonal contraceptives
-condoms
-spermicidal gel
-IUD(coil)
-sterilisation
What is a condom and advantages and disadvantage of it
Barrier method can be placed on penis of men or inside the women’s vagina to stop sperm from entering the cervix
A= widely available, can protect against STIs, no health risks
D= male condom may slip off, female condom will have to stay in place several hours after sex to be effective
What is spermicidal gel and advantages and disadvantages of it
Gel which kills sperm when it comes in contact with it
A= can be added to certain barrier methods to increase effectiveness
D= should not be used on its own, cannot be used with a male condom, some peoples skin may be sensitive to this
What is sterilisation and advantages and disadvantages of it
Sperm ducts or oviducts are stitched so no sperm or eggs can be released
A= permanent
D=requires an operation, no STI protection
What is a diaphragm in contraception
Barrier method that is a shallow plastic cup that fits over the cervix to form a barrier
What does fertility treatment involve
Giving an infertile couple a child
Advantages and disadvantages of using hormones to increase fertility
A= helps a lot of woman get pregnant when they previously couldn’t
D= doesn’t always work and is expensive (provided by NHS) , too many eggs could be stimulated resulting in unexpected multiple pregnancies, emotional and physically stressful
Define fertilisation
When the egg envelops with the sperm to form an embryo
Process of IVF
-involved giving a mother FSH and LH to stimulate the maturation of several eggs
-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)
Advantages and disadvantages of IVF
A= gives an infertile couple a child
D= multiple births can happen if more than one embryo grows into a baby these are risky for the mother and babies (high risk of miscarriage), success rate is low, stressful and upsetting especially if it ends in multiple failures, physically stressful (abdominal pain, vomiting , de hydration)
Where is adrenaline produced and why
-Produced by adrenal gland
-in times of fear and stress
-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’
Why do plants produce hormones
to coordinate and control growth and responses to light (phototropism) and gravity (gravitropism or geotropism)
What is auxin
-plant growth hormone that controls growth in response to light (phototropism and gravity (gravitropism or geotropism)
-auxin is produced in the tips and moves backwards to stimulate elongation
-if tip removed no auxin is available and shoot may stop growing
-promotes growth in shoot but inhibits growth in the root
If a shoot tip is exposed to light what happens
-More auxin accumulates on the side that is in the shade than the side in the light
-this makes the cells elongate faster on the shaded side so the shoot bends towards the light
What happens when shoots grow away from gravity
-gravity produces an unequal amount of distribution of auxin in the tip with more auxin on the lower side
-this causes the lower side to grow faster bending the shoot upwards
What happens when roots grow towards gravity
-more auxin on its lower side
-the extra auxin will inhibit growth, this means the cells on top elongate faster and the foot bends downwards
What is phototropism
Plants response to light (grows towards the light )
What is gravitropism/ geotropism
When plant roots grow towards the force of gravity
Uses of auxin
-weed killers
-rooting powders
-promoting growth in tissue culture
Uses of gibberellins
-end seed dormancy
-promote flowering
-increase fruit size
What does Ethene do (plant hormone)
used in the food industry to control ripening of fruit during storage and transport
What does gibberellin do
Stimulates plant stems to grow
