B10 - The human nervous system Flashcards
What is homeostasis?
The maintenance and control of the body’s internal environment to maintain optimum conditions to respond to changes in the environments
Examples of internal conditions that need to be controlled (4)
- pH
- blood glucose conc.
- water
- temperature
What does the nervous system allow
Allows humans to react to their surroundings and coordinate their behaviour
What are receptors
Cells that detect changes (stimuli) in the internal and external environments
What are coordiantion centres
Areas that receive and process info from the receptors. They also send signals and coordinate responses
Examples of coordination centres
Brain, spinal cord, pancreas
What are effectors
Muscles or glands that carry out a response to a stimulus
What is a reflex and why are they important
They are automatic and rapid as they dont involve the conscious part of the brain.
This allows the body to avoid harm
How is a signal sent across a synapse?
- electrical impulse triggers release of chemical neurotransmitters
- These diffuse across the synapse
- Once across, they set up another electrical impulse
Give a detailed explanation of a reflex arc
- Receptor detecs stimulus and sets up & sends an impulse along the sensory neurone to the spinal cord
- Sensory neurone is synapsed with the relay neurone which is synapsed with the motor neurone
-The electrical impulse in the neurone triggers the release and diffusion of chemical neutrotransmitters which set up another electrical imuplse in the next neurone - Impulse travels along motor neurone to effector which carries out a response
What does the cerebral cortex control?
Consciousness, language, intelligence and memory
What does the cerebellum control
Controls balance and muscle activity
What does the medulla control?
Unconscious activities e.g. breathing and heartbeat
What does the hypothalamus control
Body temperature and release of some hormones (e.g. ADH) from the pituitary gland
What does the pituitary gland control
Known as the master gland, it controls many body systems by producing and storing many hormones
Problems with the brain that make brain issues hard to resolve
- The brain is delicate
- Not everything isknown about the brain
- Blood brain barrier makes drug delivery harder
- Surgery could cause unintended damage
Outline what happens in your eyes when a bright light is switched on
- Circular muscles contract
- Radial muscles relax
- Pupil constrics
- Less light enters eyes
Outline what happens to your eyes when entering a dark area
- Circular muscles relax
- Radial muscles contract
- Pupil dilates
- More light enters eyes
What is accomodation
The process of changing the shape of the lens to focus on near or distant objects
Describe the process of accomodation for distant objects
- Ciliary muscles relax
- Suspensory ligaments taught
- Lens is flat and thin as less refraction is required
Describe the process of accomodation for close objects
- Ciliary muscles contract
- Suspensory ligaments loosen
- Lens is thicker and more curved (convex)
This is due to light rays from a close object being divergent meaning the lens has to refract light more
How is myopia caused and where is the image formed
- Eyeball is too long or lens is too curved
- Image is ‘formed’ infront of the retina
How is myopia fixed
Glasses with concae lenses
How is hyperopia caused and where is the image formed
- Lens is too flat or eyeball is too short
- The image is ‘formed’ behind the retina
How is hyperopia fixed?
Glasses with convex lenses
Why are contact lenses a common fix for eye problems
Advantages of contacts basically
- Versatile - can be soft + disposable or hard + long lasting
- Offers freedom
How does laser eye surgery fix myopia and hyperopia
- Myopia - reduces thickness of cornea so less refraction
- Hyperopia - reshapes cornea to increase refraction
