Homeostasis and Response Flashcards
What is homeostasis?
maintaining a stable internal environment in response to changes in both internal and external conditions
Why does you body temperature need to stay at a stable temp?
cells need the right temperature to function properly and for enzyme action
what are some automatic control systems in your body?
nervous and Hormonal communication
What are the three main components which work together to maintain a steady condition?
receptors, coordination centres and effectors
What is negative feedback?
your automatic control system so when something gets too low or high your body brings it back up
explain what happens when something is too high?
- receptor detects a stimulus
- coordination center receives and processes information, then organises a response
- effector produces a response which counteracts the change and restores to optimum level
What does the nervous system do?
detect and react to stimuli
What is central nervous system?
spinal chord + brain
in mammals- sensory neurons and motor nuerons
What are sensory neurones?
carry information as electrical impulses from the receptors to the CNS
What are motor neurones?
carry electrical impulses from the CNS to effectors
what are effectors?
all your muscles and glands which respond to nervous impulses
What are receptors?
cells that detect stimuli
What are the different types of receptors?
taste, sound, heat, light
how do muscles react to effectors?
contract
How do glands react to effectors?
secrete hormonmes
What are neurones?
transmit information quickly to and from the brain
What is a synapse?
the connection between two neurones
nerve signal is transferred by chemicals which diffuse across the gap
chemicals set off a new electrical signal in the next neurone
What are reflexes?
help prevent injury
rapid and automatic
What is a reflex arc?
the passage of information in a reflex (from receptor to effector)
What do neurones in reflex arcs go through?
spinal chord or unconscious part of the brain
What are relay neurones?
connect sensory neurons to motor nuerons
describe the process from when a bee stings your finger?
- stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS
- when the impulses reach a synapse between the sensory neurone and relay neurone, they trigger chemicals to be released
- causes impulses to be sent along the relay neurone
- when impulses reach a synapse between the relay and motor neurone the same thing happens, chemicals released which causes impulses to be sent along motor neurone
- impulses travel along the motor neurone to the effector
- muscle moves hand away from bee
What is reaction time?
time it takes to respond to a stimulus
What can reaction time be effected by?
age, gender or drugs
how can reactions time be measured with a computer?
- clicking a mouse as soon as a stimulus changes on a screen
What can computers do that humans can’t?
give more precise reaction time because they remove the possibility of human error, more accurate and can’t predict when to respond
What is the brain made of?
billions of interconnected neurones
What are the 4 main parts of the brain?
cerebral cortex, medulla, cerebellum, spinal chord
what does the cerebral cortex do?
responcable for things like consciousness, intelligence, memory and language
What does the medulla do?
controls unconscious activities, breathing and heart rate
what does the cerebellum do?
muscle cooordination
What are the three methods for studying the brain?
studying patients with brain damage, electrically stimulating the brain, MRI scans
How can you electrically stimulate the brain?
by pushing a tiny electrode into the tissue and giving it a small zap of electricity. by examining what stimulating different parts of the brain does, it gives an idea of what parts do
What is an MRI scan?
magnetic resonance imaging scanner that gives a detailed picture of the brains structures.
LEARN EYE DIAGRAM
LEARN EYE DIAGRAM
What is the sclera?
tough, supporting wall of eye
What is the cornea?
transparent outer layer found at the front of the eye, it reflects light into eye
What is the iris?
contains muscles that allow it to control the diameter of the pupil and therefor how much light eneters
What is the lens?
focuses light onto the retina
What is a retina?
contains receptor cells sensitive to light and colour
What is the shape of the lens controlled by?
ciliary muscles and suspensory ligaments
What is the optic nerve?
carries impulses from the receptors on the retina to the brain
What happens when light detectors in the eye detect very bright light?
circular muscles in the iris contract and the radial muscles relax
What happens when there is dim light?
circular muscles relax and radial muscles contract
What is accommodation?
eye focuses light on the retina by changing the shape of the lens
What happens when looking at a near object?
- ciliary muscles contract
- suspensory ligaments slacken
- lens becomes more curved
- Increases amount of light refracted
What happens when looking at a far object?
- ciliary muscles relax
- suspensory ligaments pull tight
- lens becomes less curved
- decreases amount of light refracted
What can’t long sited people do?
focus on near objects
When does a person become long sited?
when the lens is the wrong shape and doesn’t refract the light enough. or
the eyeball is too short
What happens when you are long sited?
the image of a near object is bought into focus BEHIND the retina
what is the medical term for long sitedness?
hyperopia
What lens corrects long sitedness?
convex lens
What can’t short sited people do?
focus on distant objects
When does shortsitedness occur?
When the lens is the wrong shape and refracts the light too much or eyeball is too long
What happens when you are short sighted?
image focuses infront of the retina
What lens can you use to correct shortsightedness?
concave lens
What is the medical term for shortsightedness?
myopia
What are three alternatives to wearing glasses?
contact lenses
laser eye surgery
replacement lens surgery
Explain contact lenses?
thin lenses that sit on the surface of the eye, lightweight and almost invisible
- two types, hard and soft
Explain laser eye surgery?
laser can be used to vaporise tissue, changing the shape of the cornea. sergeon can be very precise but there is a risk to complications
explain replacement lens surgery?
natural lens is removed and an artificial one is inserted , high risk and could damage retina
