5- Homeostasis and response Flashcards
What stimulus is the eye receptor sensitive to?
Light
What stimulus is the ear receptor sensitive to?
Sound / balance
What stimulus is the tongue / nose receptor sensitive to?
Chemicals
What stimulus is the skin receptor sensitive to?
pressure / temperature
What stimulus is the brain receptor sensitive to?
Blood temperature, concentration of water in the blood
What stimulus is the pancreas receptor sensitive to?
Concentration of glucose
What is a stimulus?
A change in the internal or external environment of a cell
What is a receptor?
Cells which detect a stimulus and convert it into an electrical impulse
What is a coordinator?
Something that processes the information and coordinates the effectors
What is an effector?
A muscle or gland that brings about a response
What does a response do?
Restores optimum levels
What is the sequence for a nervous system?
Stimulus -> Receptor -> Coordinator -> Effector -> Response
What is a neurone?
Nerve cells
What do neurones do?
Carry electrical impulses:
- from receptors to the CNS
- from the CNS to effectors
What are the 3 types of neurones?
Sensory
Relay
Motor
Function of sensory neurones
Send information from the receptor to the spinal cord and brain (CNS)
Function of relay neurones
Send information between sensory and motor neurone
Function of motor neurones
Send information AWAY from CNS to muscles or glands
What are reflexes?
Reflexes are automatic and are faster than conscious though, as the coordination happens in the spinal cord. The purpose of this is to protect us from damage/harm. After the reflex, the brain detects what has happened
What is a synapse?
A gap between 2 neurones
What does the medulla do?
Control unconscious activities (e.g. heart rate, breathing, movements in the gut (peristalis))
What is the pituitary gland also known as?
The master gland
Which region in the brain is the largest?
Cerebral cortex
What does the cerebral cortex do?
memory, conscious thought, language and intelligence
What does the cerebellum do?
Coordinates muscular activity and balance
Why is it difficult to investigate the brain? (4)
- protected by the skull
- complex with different regions + functions
- billions of neurones + their synapses
- tissue is delicate + could cause brain damage
Why is it difficult to treat brain damage? (4)
- It’s very difficult for drugs to get to the neurones in the brain
- This is because there is a barrier between the blood vessels and the brain called the blood-brain barrier
- It’s also challenging to do surgery as we son’t understand what different parts of the brain do - billions of neurones
- Brain disorders are difficult to treat because drugs cannot cross blood-brain barrier
Function of the sclera
Tough and strong. Prevents damage to eyeball
Function of the cornea
Transparent area of sclera. Refracts light
Function of the iris
Made of radial and circular muscles. Controls size of pupil
Function of the pupil
A space that allows light through
Function of the lens
A clear disk that can change shape, fine tuning the focussing of light rays
Function of the suspensory ligament
Holds the lens in place
Function of the ciliary muscle
Attaches to the suspensory ligaments and contracts and relaxes changing the shape of the lens
Function of the retina
An area at the back of the eye which is filled with light sensitive cells
Function of the optical nerve
A bundle of sensory neurones which send impulses to the brain
Function of blind spot
The point where the optic nerve leaves the eye. There is no retina in this area
What does the circular muscle do in bright light?
Contract
What does the radial muscles do in bright light?
Relax
How does the pupil change with bright light?
It constricts
What does the circular muscle do in dim light?
Relax
What does the radial muscle do in dim light?
Contract
What does the pupil do in dim light?
Dilate
Nervous pathway for bright light
Stimulus: Bright light
Receptor: Retina
Coordinator: Optic nerve -> brain
Effector: Circular muscles contract
Respons: Constricted pupil
Definition of accomodation
Ciliary muscles and suspensory ligaments work to change the shape of the lens to focus light onto the retina.
What happens to light going in in bright light?
Reduced to protect retina
What happens to light going in in dim light?
More to allow vision at low light intensity
What happens to the ciliary muscle when looking at something far away?
Relax
What happens to the ciliary muscle when looking at something near?
Contract
Suspensory ligament when looking at something far away
Tight
Suspensory ligament when looking at something near
Loose
Lens when looking at something far away
Less convex / thinner
Lens when looking at something near
More convex / thicker
Light refraction when looking at something far away
Less
Light refraction when looking at something near
More
Why does reaching make your eyes ache?
Ciliary muscles contract to focus on near words
What is myopia also known as?
Short sighted
What is hyperopia also known as?
Long sighted
If you have myopia, where does the focus fall?
In front of the retina
If you have hyperopia, where does the focus fall?
Behind retina
If you have myopia, which objects are in focus?
Near
If you have hyperopia, which objects are in focus?
Far
If you have myopia, what type of corrective lenses are needed?
Concave
If you have hyperopia, what type of corrective lenses are needed?
Convex
Myopia light refracton
Out
Hyperopia light refraction
In
If you have myopia, where will the focus be moved to if you get glasses?
Back onto retina
If you have hyperopia, where will the focus be moved to if you get glasses?
Forwards onto retina
what is the function of the cornea?
Refracts light
What part of the eye detects light?
Retina
what happens to lens to focus light from near objects?
It becomes more convex
what happens to the ciliary muscles to slacken the suspensory ligaments?
They contract
If a lens gets thicker, does light bend more or less?
More
what happens to the lens to focus light from distant objects?
Less convex
What happens to the ciliary muscles so the suspensory ligaments tighten?
They relax
If a lens gets thinner, does light bend more or less?
Less
Alternative vision correction treatments: Contact lenses
Lenses placed on the surface of the eye, can’t see them. Removed over night in sterile solution
What are the two types of contact lenses?
Hard and soft
Hard contact lenses
last a long time, ridged, remove every night
Soft contact lenses
more flexible, can be worn for 30days or some disposable after a day
Alternative vision correction treatments: Laser eye surgery
Lasers are used to reduce the thickness or increase the curve of the cornea to help focus light on the retina. Only available once eyes have stopped growing and vision stable
Alternative vision correction treatments: Replacement lenses
Permanent contact lens implanted into eye in front of or in place of the natural lens. Risks include damage to retina, cataracts and infections if original lens remains in place
What is the endocrine system?
System of glands that secrete hormones into the bloodstream
How do the effects of the endocrine system compare to those of the nervous system?
The effects caused by the endocrine system are slower but they act for longer
Where is the pituitary gland located?
Brain
Which organ monitors and controls blood glucose concentration?
pancreas
Which hormones interact to regulate blood glucose levels?
Insulin and glucagon
What is the cause of Type 1 diabetes?
Pancreas produces insufficient insulin
What is the cause of Type 2 diabetes?
Body cells no longer respond to insulin
What is the function of FSH?
Causes eggs to mature in the ovaries, and stimulates ovaries to produce oestrogen
What is the function of LH?
Stimulates the release of an egg
What is the function of oestrogen?
causes lining of uterus wall to thicken
What are the methods of hormonal contraception?
Oral contraceptives, injection, implant, skin patch, IUD
What are the methods of non-hormonal contraception?
barrier methods, copper IUD, spermicidal agents, sterilisation, abstinence
State the disadvantages of IVF treatment
- emotionally and physically stressful
- low success rate
- can lead to risky multiple births
What is the function of adrenaline in the body?
Increases heart rate and boosts delivery of oxygen
What is the function of thyroxine in the body?
stimulates basal metabolic rate, so is important for growth and development
Name one hormone controlled by negative feedback
thyroxine
Which endocrine glands control secondary sexual characteristics?
Ovaries in females, testes in males
What is diabetes?
Diabetes is a non-communicable disease where the body either cannot produce or cannot respond to insulin, leading to uncontrolled blood glucose concentrations
Function of progesterone
- maintains thick uterus lining
- inhibits release of FSH and LH
What happens during IVF treatment?
- mother given FSH and LH to stimulate the maturation of several eggs
- eggs collected from the mother and fertilised by sperm from the father in a laboratory
- fertilised eggs develop into embryos
- one or two embryos are inserted into the mother’s uterus (womb) when the embryos are still tiny balls of cells
What is homeostasis?
maintenance of a constant internal environment
Give three internal conditions controlled in homeostasis
body temperature
blood glucose concentration
water levels
Give three things all control systems include
receptors
coordination centres
effectors
Where is the body temperature monitored and controlled?
thermoregulatory centre in the brain
What happens if body temperature is too high?
blood vessels constrict (vasoconstriction) and sweat is produced
What happens if body temperature is too low?
blood vessels constrict (vasoconstriction), sweating stops, and shivering takes place
What is the function of the kidneys?
filter and reabsorb useful substances from the blood, and produce urine to excrete excess water, ions and urea
How are excess amino acids excreted from the body?
deaminated to form ammonia in the liver, ammonia is converted to urea and excreted
Which hormone controls the water level in the body?
ADH
How is kidney failure treated?
organ transplant or kidney dialysis
In kidney dialysis, what fluid is temporarily removed from the patients body?
blood
In kidney dialysis, name one substance that diffuses from the patients blood into the dialysis fluid
Urea or waste products
Define diffusion
The movement of particles from an area of higher concentration to an area of lower concentration
What are proteins broken down into?
Amino acids
Amino acids are de-aminated to form ammonia in what organ of the body?
The liver
Why does ammonia need to be excreted safely?
Ammonia is toxic
State two things controlled by negative feedback in the body
Blood glucose, water, thyroxine
Where is the hormone adrenaline produced?
Adrenal glands
What is the function of adrenaline?
Prepares the body for fight or flight, increases heart rate
Where is the hormone thyroxine produced?
Thyroid gland
What is the function of thyroxine?
Regulates how quickly the body produces energy, makes proteins
What is tropism?
The growth of a plant in response to an external stimulus (e.g. light or gravity)
Two examples of tropism
Phototropism
Gravitropism (or geotropism)
What is phototropism?
Growth in response to light
What is gravitropism (or geotropism)?
Growth in response to gravity
Purpose of auxin in shoots/stems
Cell division and elongation
Process of phototropism
- The hormone auxin is produced from the tip of the shoot
- If light is shone from the side
- Auxin accumulates on the shady side
- This leads to more growth on the shady side
- This unequal growth causes the shoot to grow towards the light
Process of gravitropism
- Auxin produced from the tip of the root and shoot
- Gravity causes auxin to build up on the side facing the ground
- The root grows down because auxin inhibits growth on the bottom side
- The shoot grows up because auxin stimulates growth on the bottom side
- In both cases unequal growth causes the root or shoot to grow either towards or away from gravity
Uses of auxin
as weed killer
as rooting powders
for promoting growth in tissue culture
Why is auxin an effective weed killer?
When absorbed by broad leaved plants they cause rapid growth which kills the plant
They don’t kill grass as it has narrow leaves and a small surface area
What are gibberellins?
Hormones that are important in initiating seed germination
What is ethene?
a gas produced by plants that controls cell division and the ripening of fruit
Uses of ethene
used in the food industry to control ripening of fruit during storage and transport
Uses of gibberellins
- end seed dormancy
- promote flowering
- increase fruit size
