Topic 5 - Homeostasis and Response Flashcards
why do the conditions in your body need to be kept steady?
your cells need the right conditions in order to function properly, including conditions for enzyme activity. even if the external environment changes
what is homeostasis?
the regulation of the conditions inside your body (and cells) to maintain a stable internal environment in response to changes in internal and external conditions
what regulates your internal environment?
automatic control systems, including nervous and hormonal communication systems
what are examples of things your body has control systems to maintain?
body temperature
blood glucose
water content
what 3 main components are all control systems made up of?
receptors
coordination centres
effectors
how do your automatic control systems keep your internal environment stable?
using a mechanism called negative feedback
what is negative feedback?
when the level of something gets too high or too low your body uses negative feedback to bring it back to normal
process of negative feedback when the stimulus level is too high:
- receptor detects stimulus - level is too high.
- coordination centre receives and processes the information then organises a response
- effector produces a response which counteracts the change and restores the optimum level - the level decreases
process of negative feedback when the stimulus level is too low:
- receptor detects a stimulus - level is too low
- the coordination centre receives and processes the information, then organises a response
- effector produces a response, which counteracts the change and restores the optimum level - the level increases
why does negative feedback keep happening?
the effectors will just carry on producing the responses for as long as they’re stimulated by the coordination centre. this can cause the opposite problem - making the level change too much(away from ideal). the receptor detects the level is too different and negative feedback starts again
what is the nervous system made up of?
central nervous system sensory neurones motor neurones effectors Receptors
what is the CNS?
in vertebrates this consists of the brain and spinal chord only. in mammals, the CNS is connected to the body by sensory nuerones and motor neurones
what are sensory neurones?
the neurones that carry information as electrical impulses from the receptors to the CNS
what are motor neurones?
the neurones that carry electrical impulses from the CNS to effectors
what are effectors?
all your muscles and glands, which respond to nervous impulses
what are receptors?
the cells that detect stimuli. there are many different types, like taste receptors in the tongue.
what can receptors form?
parts of larger, complex organs,e.g. the retina of the eye is covered in light receptor cells
what do effectors do?
they respond to nervous impulses and bring about a change. muscles and glands respond in different ways. muscles contract in response to a nervous impulse, whereas glands secrete hormones
what does the CNS do?
it receives information from the receptors and then coordinates a response. the response is carried out by effectors
example of the CNS coordinating a response:
a bird sees a cat (stimulus)
the receptors in the birds eyes are stimulated. sensory neurones carry the info from receptors to the CNS
the CNS decides what to do
The CNS sends info to the muscles in the wings (effectors) along motor neurones. the muscles contract
what is a synapse?
the connection between 2 neurones
what happens inside synapses?
the nerve signal is transferred by chemicals which diffuse across the gap. these chemicals then set off a new electrical impulse in the next neurone
what are reflexes?
rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain.
what happens if someone shines a bright light in your eye?
your pupils automatically get smaller so less light gets in your eye, this stops them getting damaged
what happens if you get a shock?
your body releases the hormone adrenaline automatically
what is a reflex arc?
the passage of information in a reflex (from receptor to effector)
where do the relay neurones in a reflex arc go through?
the spinal cord or through an unconscious part of the brain
Describe a reflex arc:
impulses are sent along a sensory neurone to a synapse which triggers chemicals to be released, these chemicals cause impulses to be sent along the relay neurone in the CNS the same thing happens in the synapse between the relay and motor neurones. they then go to the effectors which carry out the response
why is a reflex quicker then a regular response?
we don’t have to think about the response (which takes time)
what is the reaction time?
the time it takes to respond to a stimulus - its often less than a second
what can a reaction time be affected by?
factors like age, gender or drugs
what is caffeine?
a drug that can speed up a person’s reaction time.
how do you conduct an experiment for measuring reaction time?
have a person sat with their arm on the edge of a table.
hold a ruler vertically at the 0 mark between their thumb and finger. then drop it without warning.
the other person should try to catch the ruler as quickly as possible.
the further down the ruler it is caught the slower the reaction time.
repeat several times and calculate the mean distance the ruler fell by.
what are the control variables for measuring reaction time?
the same person to catch the ruler each time
the same hand catching the ruler
ruler dropped from the same height
person being tested shouldn’t have anything to affect their reaction time before
what can be used to measure reaction time?
simple computer tests e.g. clicking the mouse, or pressing a key as soon as they see a stimulus on the screen
why might a computer be better at measuring reaction time?
they give a more precise reaction time because they remove the possibility of human error.
they can record in milliseconds to give a more accurate measurement.
remove the possibility that the person being tested may be able to predict when to respond from the other persons body language
what is the brain made of?
its made up of billions of interconnected neurones
what does the brain do?
it’s in charge of all of our complex behaviours. it controls and coordinates everything you do
what are the different parts of the brain?
cerebral cortex
medulla
cerebellum
spinal cord
what is the cerebral cortex?
this is the outer wrinkly bit. it’s responsible for things like consciousness, intelligence, memory and language
what does the medulla do?
it controls unconscious activities (things you don’t think about doing) like breathing and your heartbeat
what does the cerebellum do?
responsible for muscle coordination
what are scientists that study the brain called?
neuroscientists
what are the 3 methods to study the brain?
studying patients with brain damage
electrically stimulating the brain
MRI scans
studying patients with brain damage:
if a small part of the brain has been damaged, the effect this has on the patient can tell you a lot about what the damaged part of the brain does.
electrically stimulating the brain:
the brain can be electrically stimulated by pushing a tiny electrode into the tissue and giving it a small zap of electricity. by observing what stimulating different parts of the brain does, it’s possible to get an idea of what those parts do.
example of studying patients with brain damage to map the brain:
if an area at the back of the brain is damaged and the patient is blind, that part is responsible for vision
example of electrically stimulating the brain:
when a certain part of the brain (known as the motor area) is stimulated, it causes muscle contraction and movement.
MRI scans:
a magnetic resonance imaging scanner is a big tube-like machine that can produce a very detailed picture of the brains structures. scientists use it to find out what areas of the brain are active when people are doing things like listening to music or trying to recall a memory
how has studying the brain helped people?
knowledge of how the brain works has led to the development of treatments for disorders of the nervous system. e.g. electrical stimulation can help reduce muscle tremors
how can studying the brain have consequences?
the brain is incredibly complex and delicate - the investigation of brain function and any treatment of brain damage or disease is difficult. it also carries risks, such as physical damage to the brain or increased problems with brain function
what are all of the different parts of the eye?
iris cornea pupil lens ciliary muscles sclera optic nerve retina suspensory ligaments
what is the sclera?
the tough, supporting wall of the eye
what is the cornea?
the transparent outer layer found at the front of the eye. it refracts light into the eye
what does the iris do?
it contains muscles that allow it to control the diameter of the pupil and therefore how much much light enters the eye
what does the lens do?
it focuses the light onto the retina
what is the retina?
which contains receptor cells sensitive to light intensity and colour
what controls the shape of the lens?
the ciliary muscles and suspensory ligaments
what does the optic nerve do?
it carries impulses from the receptors on the retina to the brain
what does the iris do when there is bright light?
when light receptors in the eye detect very bright light, a reflex is triggered to make the pupil smaller. the circular muscles contract and the radial muscles relax. this reduces the amount of light that can enter the eye
what does the iris do when there is dim light?
the radial muscles contract and the circular muscles relax, which makes the pupil wider
what is accommodation?
when the eye focuses light on the retina by changing the shape of the lens
what does the eye do when looking at near objects?
the ciliary muscles contract, which slackens the suspensory ligaments
the lens becomes fat (more curved)
this increases the amount by which it refracts light
what does the eye do when looking at distant objects?
the ciliary muscles relax, which allows the suspensory ligaments to pull fight.
this makes the lens go thin (less curved)
so it refracts light by a smaller amount
why are some people long-sighted?
their lens is the wrong shape and doesn’t refract light enough. so the images of near objects are brought into focus behind the retina
how can long-sightedness be resolved?
you can use glasses with a convex lens to correct it. the lens refracts the light rays s they focus on the retina
what is the medical term for long-sightedness?
hyperopia
why are some people short-sighted?
their lens is the wrong shape and refracts light too much or the eyeball is too long. images of distant objects are brought into focus in front of the retina
how can short-sightedness be corrected?
you can use glasses with a concave lens, so that the light rays focus on the retina
what is the medical term for short-sightedness?
myopia
what are the different treatments for eye defects?
contact lenses
laser eye surgery
replacement lens surgery
what are contact lenses?
thin lenses that sit n the surface of the eye and are shaped to compensate for the fault in focusing.
why do people like contact lenses?
they’re lightweight and almost invisible, they’re more convenient than glasses for activities like sports
what are the 2 main types of contact lenses?
hard lenses
soft lenses
what are the differences between hard and soft lenses?
soft lenses are generally more comfortable but have a higher risk of eye infections than hard lenses
how does laser eye surgery work?
a laser can be used to vaporise tissue, changing the shape of the cornea. so it changes how strongly it refracts light. the surgeon can precisely control how much the laser takes off to completely correct the vision
how can laser eye surgery improve short sight?
it slims the cornea down, making it less powerful
how can laser eye surgery improve long sight?
it changes the shape of the cornea so that it’s more powerful
what are the complications of laser eye surgery?
infection or the eye reacting in a way that makes your vision worse than before
what is replacement eye surgery?
where the natural lens of the eye is removed and an artificial lens, made of clear plastic, is inserted in its place.
why does replacement eye surgery have higher risks?
it involves working inside the eye so it has higher risk than laser eye surgery. the retina could get damaged and that could lead to sight loss
what does the body do to keep the core body temperature constant?
it has to balance the amount of energy gained and lost
how does the thermoregulatory centre detect body temperature?
there are receptors that are sensitive to the temperature of the blood flowing through the brain. it also receives impulses from the temperature receptors in the skin giving info about skin temperature
what does the thermoregulatory system do when you warm up?
temperature receptors detect core body temp is too high
thermoregulatory centre acts as coordination centre - it receives info from receptors and triggers effectors automatically
effectors e.g. sweat glands produce a response and counteract the change
what does the thermoregulatory system do when you cool down?
detect core body temp is too low
thermoregulatory centre acts as coordination centre - it receives info from receptors and triggers effectors automatically
effectors e.g. muscles produce a response and counteract the change
how can effectors work antagonistically?
e.g. one effector heats and another cool- they’ll work at the same time to achieve a very precise temperature. this allows a more sensitive response
what do your effectors do when you’re too hot?
sweat is produced by sweat glands and evaporates from the skin. this transfers energy to the environment.
vasodilation happens which helps transfer energy from the skin to the environment
hair erector muscles relax
what is vasodilation?
blood vessels supplying the skin with blood, dilate so more blood flows close to the surface of the skin.
what do your effectors do when you’re too cold?
hairs stand up on end
no sweat is produced
vasoconstriction happens
you shiver (your muscles contract automatically) this needs respiration, which transfers some energy to warm the body
what is vasoconstriction?
when blood vessels supplying skin capillaries constrict to close off the skin’s blood supply
what are hormones?
chemical molecules released directly into the blood. they tend to have relatively long-lasting effects
how are hormones carried around the body?
they are carried in the blood to other parts of the body, but only affect particular organs (target organs)
what do hormones control?
they control things in organs and cells that need constant adjustment
where are hormones produced?
they are produced in and secreted by various glands, called endocrine glands. these glands make up the endocrine system