Coordination and Response in Humans Flashcards
How does muticelluar organisms respond to their Environments to survive?
All living organisms can respond to changes in the environment. It can be the external environment that surrounds the body of the organism. Or it can be the internal environment within and around the cells of the organism.
A change in the environment is called a stimulus. (plural stimuli)
E.g Human have sense organs containing special receptors that allow us to detect changes in the world around us and inside our own bodies. Using this information we can react to our surroundings.
What are the receptor cells sensitive to?
eyes - light
ears - sound, changes in position - important for keeping balance
tounge - chemicals - enable us to taste
skin - touch, pressure, pain and temperature changes
Human Nervous System
The human nervous system enables your body to detect and respond quickly to stimuli. A stimulus is a change in your surroundings or inside your body. Your senses make you aware of these changes using special receptors which detect different kinds of stimuli. The rest of your nervous system coordinates all the information and control the way your body responds.
The sequence of event is:
stimulus -> receptor -> coordination -> effector -> response
The nervous system is made up of a number of parts. Explain the job of each of these parts:
- the sense organs
They detect changes in the environment (or stimuli), e.g. eyes respond to light, ears to sound.
- the central nervous system
It receives information from all the sensory organs, makes sense of the information, and controls the responses of various parts of our bodies. It also provides us with an image of the world around us.
- the sensory neurones
They carry impulses from the sense organs to the central nervous system.
- the motor neurones
They carry impulses from the central nervous system to the muscles.
What is the main difference between a voluntary action and a relfex action?
A voluntary action involves conscious thought and control by the central nervous system. A
reflex action is very fast and does not involve conscious thought.
What is the value of reflex actions to the body?
They allow important repetitive actions – breathing, control of the heart, gut, etc. – to take place without using up conscious thought, and they allow a very rapid response to danger or pain, faster than if conscious centres were involved.
Describe the following refex actions using the sequence stimulus -> receptor -> sensory neurone -> relay neurone in CNS -> motor neurone -> effector -> response:
1) a doctor hits you just below the knee cap with a rubber hammer
Blow below kneecap -> receptor in skin/tendon -> sensory neurone -> relay neurone in
spinal cord -> motor neurone -> muscles of leg -> knee jerks
2) you put your bare foot down on a drawing pin
Pain from sharp point -> receptor in skin -> sensory neurone -> relay neurone in spinal
cord -> motor neurone -> muscles of leg -> foot withdrawn
3) someone claps their hands near your face.
Sound/movement -> eyes/ears -> sensory neurone -> relay neurone in brain -> motor
neurone -> muscles of eyelids -> blink
Look at the diagram below.
a) Write a description of what is happening at each of the numbered points 1-5.
- Receptors in the skin detect stimulus.
- Impulses pass along sensory neurones to spinal cord.
- Relay neurones in spinal cord transfer impulses from sensory neurones to motor neurones.
- Impulses pass from spinal cord along motor neurones to reach muscles.
- Finally, impulses cause muscles (effector) to contract: hand is pulled away without conscious thought.
b) How do you know consciously what has happened in a reflex action like this?
Impulses also pass from the hand and muscles to the brain. Combined with impulses from the
eyes seeing what is happening, you have a conscious realisation of the hot plate and the reflex action a very short time after it has happened.
Describe each of their functions.
retina - contains receptor cells that are sensitive to light
sclera - tough white outer layer
iris - muscle that changes the size of the pupil
cornea - curved, transparent area at the front of the eye
lens - focuses the image on the retina
optic nerve - sensory neurones carry impulses from the retina to the brain
pupil - hole that allows light into the eye
ciliary muscles - change the shape of the lens
suspensory ligaments - attach the ciliary muscles to the lens
The pupil of the eye is the hole through which light enters. The size of the pupil is controlled by the muscles of the iris, and the pupil changes size depending on the light levels.
Explain how the muscles of the iris change the size of the pupil.
Diagrams to show what the pupil and iris of the eye would look like:
1) in very bright light
2) in ordinary light levels
3) in very dim light
The iris is a ringed-shaped disc of muscle that is the coloured part of the eye.
The hole in the centre of the ring is the pupil. The iris is made of circular and radial muscles that can contract or relax to change the size of the pupil.
In dim light conditions, the iris muscles widen the pupil. The circular muscles contract This allows more light to reach the receptor cells in the retina. The pupil is dilated.
When the light is bright the iris muscles make the pupil smaller to protect the receptor cells from damage. The radial muscels contract. The pupil is constricted.
Here is some information about three eye problems. Use what you know about how the eyes work to explain why these conditions affect sight.
a) With cataracts, the lens goes cloudy or milky.
If the lens is cloudy, light cannot get through into the eye, making it impossible to see. The blindness will be progressive as the lens becomes increasingly
cloudy.
b) some people have an eyeball that is mroe egg-shaped than round. They are often short-sighted - they can see close objects but not those at a distance.
The lens focuses light on the retina. If the eyeball is egg-shaped or bulbous, light from distant
objects will tend to be focused in front of the retina, so lenses are needed to bend the light from
distant objectsbefore it enters the eye.
c) If the retina of the eye becomes detached, the person goes completely blind in that eye.
The retina contains light-sensitive cells, so if it becomes detached there are no working sensory
cells to detect light and it becomes impossible to see.
Focusing the light
a) How do we focus on nearby objects?
b) How do we focus on distant objects?
The eye lens is a clear, flexible bag of fluid surrounded by circular ciliary muscles that change the shape of the lens (accomodation). Suspensory ligaments attach the lens to the ciliary muscles.
a) How do we focus on nearby objects?
- the ciliary muscles contract
- the suspensory ligaments relax
- the lens is short and fat to refract light a lot
The light from nearby objects needs to be bent strongly to focus on the retina. When looking at
nearby objects, the ciliary muscles contract, so the suspensory ligaments are slack and the lens
becomes thicker, bending light more strongly. This brings nearby objects into focus on the retina.
b) How do we focus on distant objects?
- the cliliary muscles relax
- the suspensory ligaments contract
- the lens is long and thin because the light only needs to be refracted a little.
The light from distant objects needs to be bent only weakly to focus on the retina. When looking
at distant objects, the ciliary muscles relax, pulling in the suspensory ligaments which pull on
the lens, stretching it thinner and bending light less strongly. This brings distant objects into
focus on the retina.
Describe the changes that take place in your body when your temperature begins to rise above 37 degree celcius or fall below 37 degree celcius
Enzymes in your body work best at 37c, so it’s essential that your body remains very close to this temperature. Heat produced through respiration is used to maintain your body temperature.
If body temperature becomes too high
- Blood vessels in the skin widen (vasodilation) and the blood flows closer to the skin surface so heat can be lost.
- sweat is produced – the evaporation of sweat requires heat energy.
Getting too hot can be very dangerous. If too much water is lost through sweating, the body becomes dehydrated. This can lead to heat stroke and even death.
If the body temperature falls too low
- Blood vessels in the skin constrict (vasconstriction) and the blood flow near the skin is reduced.
- Sweating stops
- Muscels start making tiny contractions (shivering) which releases heat.
Getting too cold can be fatal. Hypothermia is when the body tempeature drops below 35 degree Celcius. This causes unconsciousness and sometimes death.
Insulin is an important hormone.
Name the target organ for insulin and state the role of insulin in the body.
June 2014 paper 2BR
Liver (pancreas - gland).
Insulin decreases the level of glucose in the blood. It causes the liver cells to change blood glucose into glycogen to be stored.
Tips:
Make sure you’re clear about the difference between glucagon ( the hormone), glycogen (the carbohydrate stored in the liver) and glucose ( the sugar carried around in the blood).
The diagram shows a section through an eye with the iris and parts A, B and C labelled.
(a) Name parts A, B and C.
(b) When you move from a bright room into a dark room you cannot see very well for a while. After a brief time, a change in the iris helps you to see more clearly.
(i) The iris contains muscle tissue.
What is meant by the term tissue?
(ii) Describe the changes that take place in the iris when moving into the dark room and explain how they help you to see more clearly.
June 2014 2B
a)
A - lense
B - cornea
C - retina
b)
(i) A tissue is a group of cells that have similar structure and function. For example:
- muscle tissue contracts so we can move
- glandular tissue produce substances such as enzymes and hormones
- epithelial tissue covers organs.
(ii) When you move from a bright room into a dark room
- radical muscles contracted, and circular muscle relaxed;
- the iris muscles widen the pupil;
- this allows more light to reach the receptor cells in the retina. The pupil is dilated.
(b) Explain how lens changes when you view a near object.
(a) retina contains light receptor cells
sensory neurone that sends impulse into brain
synapes/synaptic(cleft)/synaptic(gap) microscopic gap between neurone
Iris contains muscle effector cells
(b) When receiving light rays from a near object,
- the ciliary muscles contract
- the suspensory ligaments relax
- the lens is more convex, short and fat to refract light a lot
The skin is an organ of homeostasis and excretion.
(a) Describe what is meant by the term excretion.
Excretion is the removal, from an organism, of waste substance produced by chemical reactions inside its cells (metabolism)
The skin, lungs and kidneys are organs used for excretion.
Explain the role of structure A.
Explain the role of structure B.
Structure A - sweat gland
Sweat is produced to cool the skin. The evaporation of sweat draw heat from the skin.
Structure B - Blood vessels
Blood vessels in the skin widen (vasodilation) and the blood flows closer to the skin surface so heat can be lost.
Some hormones are involved in homeostasis.
(i) Explain the role of insulin in homeostasis.
(ii) Explain the role of **ADH** in hoemostasis.
(i) Insulin decreases the level of glucose in the blood. Causes liver cells to change blood glucose into glycogen to be stored.
(ii) ADH, antidiuretic hormone from the pituitary gland, regulates the amount of water in the body.
ADH changes the permeability of the collecting ducts to water so that more or less water is reabsorbed into the blood. This changes the volumne and concentration of the urine. Increase in ADH increases the amount of water reabsorbed by the kidneys. And small quantity of dark, concentrated urine is produced. More water is reabsorbed into the blood.
Describe how the levels of blood glucose are kept constant in human plasma after
eating a meal.
- After a meal, blood sugar levels go up.
- Pancreas monitors the blood sugar(glucose) level.
- Insulin is released by the pancreas, and lets your body cells take in some of this glucose.
- Insulin turns glucose into glycogen. Glycogen is stored in the muscles and liver. As a reuslt, it lowers the level of glucose in the blood after a meal.
Match the letter to health problem
conjunctivitis (A)
cataract B;
blindness G;
glaucoma F;
myopia D
(i) Name the structures labelled A, B and C.
(ii) Explain the changes that take place in structures B and C when a person focuses on a nearby object.
(i) A - conjunctiva
B - lens
C - ciliary muscle
(ii) When looking at nearby objects, the ciliary muscles contract, so the suspensory ligaments are slack and the lens becomes thicker, bending light more strongly. This brings nearby objects into focus on the retina.
Human responses are also controlled by hormones.
For one named example of a hormone, give its site of production and its effect.
