Topic 5 - Homeostasis And Response Flashcards
What is the brain responsible for?
Complex behaviours
Whoa is the Brian made up of?
Billions on interconnected neurones and has different regions that carry out different functions
What is the cerebral cortex?
Outer wrinkly bit - responsible for consciousness, intelligence, memory and language
What is the medulla?
Attached to spinal cord - controls unconscious activities (like breathing and your heartbeat)
What is the cerebellum?
At the back of your brain at the bottom - responsible for muscle coordination
How do scientists study the brain and work out which bits do what?
Studying patients with brain damage
Electrically stimulating the brain
MRI scans
What makes investigating the brain difficult?
It is complex and delicate
What is homeostasis?
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
What does homeostasis do?
Maintains optimal conditions for enzyme action all functions
What does homoeostasis control in the human?
Blood glucose concentration
Body temperature
Water levels
Give two examples of automatic control systems?
Nervous responses chemical responses
What do all control systems include?
Receptors
Coordination centres
Effectors
What is a receptor?
Cells which detect stimuli (changes in environment)
What are coordination centres?
They receive and process information from the receptors
Give examples of coordination centres?
Brain
Spinal cord
Pancreas
What is an effector?
Muscles or glands which bring about responses which restore optimum levels
How do automatic control systems keep your internal environment stable?
Using a mechanism called negative feedback
What does the nervous system enable humans to do?
React to their surroundings and coordinate their behaviour
Give examples of receptors
Taste receptors on tongue
Sound receptors in ears
How do muscles and glands respond to information?
Muscles contract
Glands secrete hormones
What happens to information from receptors?
It passes along cells called neurones as electrical impulses
Where are the electrical impulses from receptors sent?
The central nervous system
What is the central nervous system?
- In vertebrates this consists of the brain and spinal cord
- In mammals it is connected to the body by sensory and motor neurons
What does the central nervous system do?
Coordinates the response of effectors
What is the order in which a nervous impulse travels?
1) stimulus
2) receptor
3) coordinator
4) effector
5) response
What are reflex actions?
Automatic and rapid actions that do not involve the conscious part of the brain
What is a synapse?
The connection between two neurons
How is the nerve signals transferred through the synapse?
It is transferred by chemicals which diffuse (move) across the gap and the chemicals set off a new electrical signal in the next neurone
What is stage one of the reflex arc?
A stimulus (a bees sting) is detected by receptors
What is stage two of the reflex arc?
Impulses are sent along a sensory neurone
What is stage three of the reflex arc?
The impulses reach a synapse between the sensory neurone and the relay neurone and trigger chemicals to be released
What is stage four of the reflex arc?
The impulses pass along the relay neurone in the CNS
What is stage five of the reflex arc?
The impulse reaches a synapse between the relay neurone and a motor neurone and chemicals are released
What is stage six of the reflex arc?
The impulses travel along the motor neurone to the effector which contracts as a response
Why is the reflex arc quicker than normal responses?
You don’t have to think about the response
how can you measure reaction time?
Ruler drop test
Computer
How do you test reaction time using a computer?
The person being tested has to click the mouse as soon as they see a stimulus on the screen
What are the benefits of using computers to test reaction time
- Give more precise readings as they remove the possibility of human error
- Record time in milliseconds so it is more accurate
What is the Sclera?
Tough supporting wall
What is the cornea
Transparent outer layer found it front of eye that refracts light
What is the iris?
Contains muscles that allow it to control diameter of the pupil and therefore how much light enters the eye
(Cover edges of lens just in-front)
What is the pupil?
The hole in the middle
What is the lens?
Focuses light onto the retina
Behind the pupil
What is the retina?
Contains receptors cells sensitive to light intensity and colour
(At back of eye)
What do the ciliary muscles and suspensory ligaments do?
Control the shape of the lens
Top (suspensory) and bottom (ciliary) of lens
What is the optic nerve?
Carries impulses from the receptors on the retina to the brain
(Back and bottom of eye ball)
What is the eye?
Sense organ containing receptors sensitive to light intensity and colour
What are the functions of the eye the relate to it’s structure?
Accommodation to focus on near or distant objects
Adaptation to dim light
What is accommodation in the eye?
The process of changing the shape of the lens to focus on near or distant objects
How does the eye focus on a near object?
- The ciliary muscles contract
- The suspensory ligament loosen
- The lens is then thicker and refracts light rays strongly
How does the eye focus on a distant object?
- The ciliary muscles relax
- The suspensory ligament are pulled tight
- The lens is then pulled thin and only slightly refracts light rays
What are two common defects of eyes?
Myopia (short sightedness)
Hyperopia (long sightedness)
Why do the defects of eyes happen?
Rays of light do not focus on the retina
How are the defects of eyes treated?
Spectacle lenses which refract the light rays so that they focus on the retina
What are the new technologies to treat eye defects?
- Hard and soft contact lenses
- Laser surgery to change the shape of the cornea
- Replacement lens in the eye
What is the iris reflex?
Adjusting the eye for bright light
How does the iris reflex work in bright light?
A reflex is triggered that makes the pupil smaller
The circular muscles in the iris contract and the radial muscles relax to reduce the amount of light that can enter the eye
How does the iris reflex work in dim light?
The radial muscles contract and the circular muscles relax making the pupil wider
When does long sightedness occur?
When the lens is the wrong shape and doesn’t refract the light enough or when the eyeball is too short
What happens to the light rays in long sighted eyes?
The images of new objects are brought into focus behind the retina
How can you correct long sightedness?
Using glasses with a convex lens
When does short sightedness occur?
When the lens is the wrong shape and refracts light too much or when the eyeball is too long
What happens to the light rays in short sighted eyes?
The images of distant objects are brought into focus in front of the retina
How can you correct shortsightedness?
Using glasses with a concave lens
What are the advantages of contact lenses?
Convenient, light weight and almost invisible
What are the two types of contact lenses and which is better?
Hard lenses and soft lenses
Soft lenses are more comfortable but carry a higher risk of eyes infections
What is laser eye surgery?
Laser is used to vaporise tissue, changing the shape of the cornea - slimming it down makes it less powerful and can improve short sight
What are the advantages of laser eye surgery?
The surgeon can precisely control how much tissue the laser takes off