Co-ordination and response Flashcards
What is a voluntary action
A voluntary action involves a conscious decision made within the cerebral hemispheres of the brain Relatively slow response The same stimulus can provide a variety of different responses Many voluntary actions are learnt
What does the nervous system allow us to do
It allows us to make sense of our surroundings and respond to them and to co-ordinate and regulate body functions
What are neurones
Nerve cells found in the nervous system
Hundreds of neurones make up one nerve
What are receptors
They are found in sense organs
They respond to changes in the environment (stimuli)
What is an effector
Parts of the body that respond to a stimulus
e.g. muscles and glands
What are the three different types of neurone and what are their functions
Sensory - Carry nerve impulses from sense organs to the central nervous system
Relay - Found in the central nervous system and connect sensory and motor neurones
Motor - Carry nerve impulses from the central nervous system to effectors
Why can a nerve impulse only travel in one direction along the reflex arc?
Because the neurotransmitter is present on the only one side of the synapse Drugs act as synapses
What does the human nervous system contain
Central nervous system - brain and spinal cord
Peripheral nervous system - all of the nerves in the body
What is an involuntary action
An involuntary action only involves the spinal cord and other parts of the brain Faster response The same stimulus produces the same response; it is automatic Many involuntary actions are instinctive
What is a synapse?
A tiny gap between two neurones
Describe what happens when a nerve impulse arrives at the end of a sensory neurone
Vesicles containing neurotransmitters move to the cell membrane of the sensory neurone The vesicles burst open and empty the neurotransmitter into the synaptic cleft The neurotransmitter diffuses across the cleft The neurotransmitter molecules slot into their receptors on the membrane of the relay neurone This sets off a nerve impulse in the relay neurone
How are neurones adapted
They have a long axon to carry impulses over long distances
The axon is insulated by a fatty (myelin) sheath, increases the speed of nerve impulse
What do dendrites do
Dendrons are tiny branches at the end of neurones which break up in dendrites which recieve incoming nerve impulses
What is a nerve impulse
An electrical signal that passes along a nerve impulse
What is a sense organs
Groups of receptor cells responding to specific stimuli; light, touch, sound, tempurature and chemicals
What does the iris do
Controls how much light enters the pupil
What does the lens do
Focuses light on the retina
What do the pupil do
A hole in the iris that allows light to pass through to the lens
What does the cornea do
Refracts light
What does the retina do
Contains light receptors, some sensitive to light of different colours
What does the fovea do
Where light is focused when you look directly on an object; geatest concentration of receptors is here
What does the blind spot do
No receptors here; so light falling onto this area is not seen
What does the optic nerve do
Carries nerve impulses to the brain
What happens when light enters the eye
Light enters the eye through the cornea
Light is refracted as it passes through the cornea and the lens
Light is focused onto the recpetor cells in the retina
This sets off nerve impulses that travel along the optic nerve to the brain
Why do the muscles in the iris contract making the diameter of the pupil smaller in bright light
The bright light may damage the retina
What happens when bright light falls on the retina
Impulses pass alomng sensory neurones to the brain, and then along motor neurones to the muscles in the iris
Circular muscles in the iris contract, the diameter of the pupil is decreased, reduces amount of light able to pass through the pupil
What happens when dim light falls on the retina
Radial muscles in the iris contract, this widens the pupil allowing more light to pass through
What are the radial and circular muscles in the eyes
Antagnostic, they have opposite effects
What do the suspensory ligaments do
They hold the lens in place
How does an eye focus on a close object
The lens needs to be wide and thick, so it refracts more strognly
To achieve this, the suspensory ligaments must be loose
the ciliary muscles must contract
How does an eye focus on a distant object
The lens must be narrow and thin, to refract light less strongly
The suspensory ligaments must be pulled tight
The ciliary muscles need to relax
What two types of light sensitive cell does the retina contain
Rods - sensitive to dim light
cones - sensitive to bright light
Where are rods and cones found
Cones - In the fovea
Rods - in most other parts of the retina
What is a hormone
A chemical substance, produced by a gland and carried by blood which alters the activity of one of more specific target organs
What gland secretes adrenaline
When is it secreted
what is its function
The adrenal glands; it is secreted when the person is excited or freightened; it increases heart rate, breathing rate, pupils dilate, causes concentration of glucose in blood to increase
What gland secretes insulin
when is it secreted
what is insulins function
The pancreas; when the concentration of glucose in the blood is too high, causes the liver to reduce concentration of glucose in the blood
Where is testosterone secreted
when is it secreted
what is its function
- Secreted from the testes
- it is secreted from puberty onwards
- its function is to produce male secondary sexual characteristics
- Where is oestrogen secreted
- When is it secreted
- what is its function
- Secreted from the ovaries
- from puberty onwards
- secreted to produce female secondary sexual characteristics and to regulate menstrual cycle
What are the difference between nervous and hormonal control
Hormonal control acts slower than nervous control as it must travel in the blood rather than along neurones as electrical signals
Hormones take a longer time to break down as they remain in the blood for a while whereas nerve impulses happen at an instant in time
What is the general type of gland that produces hormones
An endocrine gland
Define “homeostasis”
The maintenance of a constant internal environment
What happens if the internal body tempurature rises too high
- Blood tempurature receptors in the brain detect the rise in tempurature
- This causes the brain to send nerve impulses to the sweat glands
- this makes the sweat glands secrete more sweat, which evaporates and cools the skin
- the erector muscles relax so the hairs lie flat
What happens if the internal body tempurature falls too low
- Blood tempurature receptors in the brain detect the fall in tempurature
- This makes the brain send nerve impulses to the erector muscles and skeletal muscles
- This makes the erector muscles contract so hairs are pulled erect, trapping an insulating layer of hair
- the skeletal muscles contract and relax quickly (shivering), releasing heat that helps warm the blood
What can happen to arterioles (homeostasis)
They can become narrower (vasoconstriction) or wider (vasodilation)
What happens if vasoconstriction occurs
Arterioles become narrower
- less blood is delivered to the surface capillaries, and blood is diverted beneath the fat layer
- this reduces heat loss from the blood to the air
What happens if vasodilation occurs
The arterioles become wider
- more blood flows through the surface capillaries
- more heat can therefore be lost from blood to the air
What happens when blood glucose concentration rises too high
- The pancreas secretes insulin into the blood
- Insulin is carried into the blood from the liver
- insulin stimulates the liver to take up glucose from the blood
- the liver changes glucose into the polysaccharide glycogen, and stores it
What happens when blood glucose levels fall too low
- The pancreas secretes glucagon into the blood
- glucagon is carried in the blood to the liver
- glucagon stimulates the liver to break down glycogen into glucose
- the liver reduces glucose into the blood
What is type 1 diabetes
The type where the person’s own immune system attacks and destroys cells in the pancreas which secrete insulin
Why after a meal does a diabetes patient have very high glucose levels in his blood
Because there is no insulin to stimulate the liver to convert the extra glucose in the blood into glycogen
Between meals, what is happening to a diabetes patient’s glucose levels and why
The glucose levels are falling much lower than usual
This is because the body gradually uses up the glucose in respiration
But there is no glycagon in the liver to be converted to glucose to top up the glucose concentration in the blood
What are some symptoms of diabetes
- Thirst - because a high concentration of glucose in the blood decreases its water potential; the brain percieves this as the body needs more water
- Having glucose in urine - happens when the blood glucose concentration rises so high that the kidneys are unable to absorb all the glucose back into the blood
- Blurred vision - happens because the change of water potential of the blood cause osmosis to occur, which changes the shape of the lens of the eye
- feeling very tired between meals - betwee meals blood sugar levels drop very low, as there is not enough glucose for respiration to occur
How is type 1 diabetes cured
A combination of diet and insulin injections
- eat regular small meals, to even out the intake of carbohydrates throughout the day
- Injecting insulin after a meal to reduce any spikes in the blood glucose concentration
Definition of gravitropism
A response in which parts of the plant grow towards or away from gravity
Definition of phototropism
A response in which parts of a plant grow towards or away from the direction which light is coming from
How does a plant grow in even light
The shoot grows straight upwards
How does a plant grow in light from one side
A shoot grows towards the light
This is phototropism
How does a plant grow in no light
In darkness, a shoot grows very tall and spindly, and looses its green colour
What are auxins and what do they do
Auxins are plant hormones which stimulate cells to get longer by making plants take up extra water
What happens to auxins when light shines on one side of the plant
active transport causes auxin to accumulate on the shady side
- This means that the shady side elongates more causing it to curve
What happens to the auxin on the shaded side of the plant
They elongate more than the cells on the bright side
The shoot curves towards the light
What happens to auxins on a horizontally growing shoot when light is shone on the up side
- What does it cause
Auxins accumulate on the lower side
- This causes elongation of auxins on the dark side which causes the shoot to curve upwards
Defintion of a drug
A substance taken into the body that modifies or affects chemical reactions in the body
What is a medicinal drug
A drug used to prevent or cure disease
What are antibiotics
Drugs that kill bacteria inside the body.
- Used to cure infections that are caused by pathogenic bacteria
How do certain types of bacteria become reistant to antibiotics
- Within a population of bacteria, there are some bacterium that have alleles that make them resistant to antibiotics
- these bacteria survive and reproduce to create the next generation in which all of them have the allele
How can we reduce the risk of bacteria developing resistance
By reucing the use of antibiotics
e.g. don’t give people antibiotics who have viral infections, which antibiotics are ineffective against
What is alchahol
- A depressant drug
- people become addicted to alchahol and cannot function without it
- They experience withdrawal symptoms like nausea and tremors
- causes agression and anti social habits
What is a depressant drug
A drug which slows reaction times and reduces self-control
What is heroin
- Heroin is a depressant
- It reduces pain and slows breathing rate
- injection of heroin carries risks of transmitting pathogens into the blood, such as HIV
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What does heroin affect?
Synapses
- It fits into receptors that normally accept neurotransmitters called endorphins which make us feel good
- heroin reduces the production of endorphins
- if a person takes heroin, they have fewer endorphins when sober creating awful withdrawals
What does cigarette smoke contain
Carbon monoxide - binds to haemoglobin and prevents transfer of oxygen
Nicotine - a highly addictive stimulant drug
Tar - mixture of different substances some of these are carcinogens which carry the risk of cancer
What does tobacco smoke also cause
- Chronic obstructive pulmonary disease -
- happens when delicate walls of alveoli break down, so that gas exchange cannot occur
- their cells cannot recieve oxygen so they cannot respire
- eventually they dont have enough energy to walk around and need to sit all day, breathing from an oxygen cylinder
Why does smoking cause cancer
The chemicals in cigarette smoke cause changes in the DNA which lead to the cells dividing uncontrollably and forming cancerous tumors
What chemicals are steroids
- Testosterone
- Osetrogen
- Progestorone
What is testosterone
An anabolic steroid
What does an anabolic steroid cause
It stimulates metabolic reactions that result in muscle developemtn and increased strength
What is a correlation
One thing causes another
