Topic 5: Homeostasis Flashcards
What is homeostasis?
Homeostasis is the regulations of conditions to maintain a stable internal environment
What are the main components your automatic control systems are made up of?
- receptors
- coordination centre
- effectors
When is negative feedback used?
When a level is too high or too low, your body uses negative feedback to return it back to normal
What is a stimulus?
A change in environment
Describe how the body uses negative feedback to return the level back to normal when the level is too high
- receptors detect a stimulus, level is too high
- coordination centre receives and processes the information and organises a response
- the effector carries out the response to counteract the change and restore its optimum level - the level decreases
Describe how the body uses negative feedback to return the level back to normal when the level is too low
- receptors detect a stimulus, the level is too low
- coordination centre receives and processes the information and organises a response
- the effector carries out the response to counteract the change and restore optimum level - the level increases
What is the central nervous system made up of?
The brain and spinal cord
What is the spinal cord and body organs connected by?
They are connected by nerves. Nerves are made up of neurones
What are the three neurones and what are their functions?
- sensory neurone - transmits signals from receptors
- relay neurone - transmits signals between neurones
- motor neurone - transmits signals to the effector
What are the two types of responses that occur when your body detects a stimulus?
Voluntary response and involuntary response (also known as a reflex action)
Why is the nervous system important in humans?
It allows us to react to our surroundings and coordinate our behaviour
What happens in the nervous system when a voluntary response occurs?
- stimulated receptor detects a stimulus and sends a signal to the sensory neurone
- the sensory neurone then carries the signal and sends it to the spinal cord and then the brain
- the brain receives and processes the information and sends a response via the motor neurone to the effector
- the effector carries out the response
What happens in the nervous system when an involuntary response occurs? (Also known as a reflex action)
- stimulated receptor detects a stimulus and sends a signal to the sensory neurone
- the sensory neurone then sends the signal to the relay neurone in the spinal cord
- the relay neurone then connects to the motor neurone so the response travels via the motor neurone to the effector
- the effector carries out the response
What are the features found in a nerve cell?
- nucleus
- cell body
- dendrites
- dendron (if signal sent towards cell body)
- axon (if signals are carried away from the cell body)
- insulating sheath
- axon terminal
- myelin
What are some features of neurones?
Neurones are like wires. They carry electrical signals and are long so that the signals can travel long distances
They have an insulating sheath to stop electrical signals jumping onto other neurons
What are synapses and what do they do?
Synapses connect neurones - the connection between two neurones
How do synapses connect to neurons?
- the connection between two neurons is called a synapse
- the nerve signal is transferred by chemicals which diffuse across the gap
- these chemicals then set off a new electrical signal in the next hormone
What are reflexes and what do they do?
Reflexes are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain
What is a reflex arc?
The passage of information in a reflex (from receptor to effector) is called a reflex arc
The reflex arc goes through the central nervous system
Describe what happens when the reflex arc goes through the central nervous system
- cheeky bee stings finger
- stimulation of the pain receptor
- impulses travel along the sensory neurons
- impulses are passed along a relay neurone via a synapse
- impulses travel along a motor neurone via a synapse
- when impulses reach muscle, it contracts
What are the two hormones that control blood glucose level?
Insulin and glucagon
Give one example on how glucose is put into the blood
Eating foods containing carbohydrates puts glucose into the blood from the gut
What are two things that removes/ reduces glucose from the blood?
- metabolism of cells
- vigorous exercise
Where and what can excess glucose be stored as?
Excess glucose can be stored as glycogen in the liver and in the muscles
How are changes of the level of glucose in the blood monitored and controlled?
The level of glucose in the blood must be kept steady
Changes are monitored and controlled by the pancreas, using hormones insulin and glucagon
What happens when the blood glucose level is too high?
blood glucose level is too high - insulin is added
- blood with too much glucose
- insulin secreted by pancreas
- too much glucose but insulin as well
- glucose moves from blood into liver and muscle cells
- insulin makes the liver turn glucose into glycogen
-Body glucose reduced
What happens when the blood glucose level is too low?
Blood glucose level is too low - glucagon is added
- blood with too little glucose
- glucagon secreted by pancreas
- too little glucose, but glucagon as well
- glucose released into blood by the liver
- glucagon makes the liver turn glycogen into glucose
- blood glucose increases
What is diabetes?
The condition that affects your ability to control your blood sugar level
Describe the two types of diabetes
- Type 1: is where the pancreas produces little or no insulin
- Type 2: is where a person becomes resistant to their own insulin
Type 1 diabetes needs insulin therapy - what is insulin therapy?
Very effective treatment
Usually ensures several injections of insulin throughout the day
What does insulin therapy do?
Makes sure that glucose is removed from the blood quickly once the food has been digested, stopping the level getting too high
What do people with Type 1 diabetes need to keep in mind?
Limiting the intake of food rich in simple carbohydrates
Taking regular exercise
What can having type 2 diabetes cause?
Can cause a person’s blood sugar level to rise to a dangerous level
Give an example of what can cause type 2 diabetes
Being overweight increases the chance of developing type 2 diabetes, as obesity is a major risk factor
What can type 2 diabetes be controlled by and what do people with Type 2 diabetes need to keep in mind?
Can be controlled by eating carbohydrates, controlled diet and getting regular exercise
Describe the four stages of the menstrual cycle
Stage 1: Day 1 - menstruation starts - the uterus lining breaks down for about 4 days
Stage 2: the uterus lining builds up again, from day 4 to day 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
Stage 3: An egg develops and is released from the ovary at day 14 - this is called ovulation
Stage 4: the wall is maintained for about 14 days until day 28. If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts again
What happens during puberty?
Your body starts releasing sex hormones that trigger off secondary sexual characteristics e.g. the development of facial hair in men and breasts in women
What’s the main reproductive hormone in men and how is it released?
In men, the main reproduction hormone is testosterone - it’s produced by the testes and stimulates sperm production
What’s the main reproductive hormone in women and how is it released?
In women, the main reproductive hormone is oestrogen - it’s produced in the ovaries
What are the four hormones the menstrual cycle is controlled by?
Oestrogen, FSH, LH, progesterone
What do the hormones FSH and Oestrogen do and where are they produced?
FSH (follicle - stimulating hormone):
- produced in the pituitary gland
- causes an egg to mature in one of the ovaries in a structure called follicle
- stimulates the ovaries to produce oestrogen
Oestrogen:
- produced in the ovaries
- causes the lining of the uterus to grow
- stimulates the release of LH (which causes the release of an egg) and inhibits the release of FSH
What do the hormones LH and Progesterone do and where are they produced?
LH (luteinising hormone):
- produced by the pituitary gland
- stimulated the release of an egg on day 14 (ovulation)
Progesterone:
- produced in the ovaries by the remains of the follicle after ovulation
- maintains the lining of the uterus during the second hand of the cycle
- when the level of progesterone falls, the lining breaks down
- inhibits the release of LH and FSH
Describe condoms and sterilisation surgery
Condoms:
- no hormones involved - barrier
- advantages: cheap and highly effective
- disadvantages: might be allergic, might tear
Sterilisation surgery:
- no hormones involved - culturing the ovarian duct and testes
- advantages: non-hormonal
- disadvantages: can’t reverse
Describe oral contraceptives and implants
Oral contraceptives:
- hormones involved - releases oestrogen and progesterone, so FSH and LH can’t be released
- advantages: free in the UK, very effective
- disadvantages: causes illness and weight gain, doesn’t protect against STDs
Implants:
- hormones involved - high levels of oestrogen and progesterone to prevent LH and FSH
- advantages: convenient
- disadvantages: side effects, doesn’t protect sexual transmitted infection
Describe copper UD
- no hormones - prevents implantation
- advantages: convenient
- disadvantages: painful periods
What is the eye? Name all the several parts in the eye
The eye is a sense organ
Several parts found in the eye: the sclera, the cornea, the iris and pupil, the lens, the ciliary muscles and suspensory ligaments, the optic nerve
What is the function of the cornea?
The transparent outer layer found at the front of the eye
It refracts light into the eye
What is the function of the suspensory ligaments?
Controls the shape of the lens
What is the function of the sclera?
The tough, supporting wall of the eye
What is the function of the optic nerve?
Carries impulses from the receptors on the retina to the brain
What is the function of the ciliary muscles?
Controls the shape of the lens
What is the function of the retina?
Contains receptor cells sensitive to light intensity and colour
What is the function of the lens?
Focuses the light onto the retina (which contains receptor cells sensitive to light intensity and colour)
What is the function of the iris?
controls how much light enters the eye ( contains muscles that control the diameter of the pupil)
Describe what happens when light receptors in the eye detect a very bright light
- a reflex is triggered that makes the pupil smaller
- circular muscles in the iris contract
- the radial muscles relax
- this reduces the amount of light that can enter the eye