B10 - The nervous system Flashcards
Define homeostasis:
the regulation of internal conditions in a cell/organism to maintain optimum conditions for enzyme action and all cell functions, in response to internal/external changes
What 3 things are controlled by homeostasis in the body?
-water content
-body temperature
-blood glucose concentration
Explain the functions of the parts in a control system in the body:
-receptor cells detect stimuli (change in environment)
-coordination centres (brain/spinal cord/pancreas) receive and process information from receptors, to coordinate a response for the effector
-effectors (muscles/glands) that bring about a response to the stimuli to restore optimum levels
Why is the nervous system important?
-promotes survival
-allows us to respond to our environment
-coordinate our behaviour
Describe the 2 parts of the nervous system:
central nervous system - brain and spinal cord organs
peripheral nervous system - all sensory/motor neurones (not organs)
Describe the path of a coordinated response through the body, and provide examples:
-stimuli (change in environment, like sound)
-receptor (ear)
-through sensory neurones to coordination centre (CNS)
-through motor neurones to effector (muscle contraction)
-effect (movement)
Describe what the types of neurones look like:
-sensory has nucleus attached along the axon
-motor has nucleus attached at one end
What is a reflex, and what is involved in the path of a reflex arc? Give examples:
-a rapid/automatic response to a stimulus that bypasses the conscious part of the brain
-reflex arc is the same as a coordinated response except it goes to spinal cord (or bypasses conscious brain parts) and passes through a relay neurone
-breathing, heart beat, digestion
How does a synapse work? How does it affect reaction time?
-gap between two neurones
-neurotransmitters are emitted at one end, diffuse across gap, received at other end
-another electrical impulse sent
-diffusion is slower than electrical impulses, and thus increases reaction time
RP 7 - How can you investigate human reaction time?
-sit down with one arm at rest over table, and have partner hold a ruler where the bottom of it is between your fingers
-partner will drop the ruler without notice, and you have to try and catch it as quickly as possible
-take the length on the ruler that is just above the contact point of where it was caught, use conversion table to convert to time
-repeat ~5 times, switch hands + roles
Don’t do it too many times (catcher will gain practice and affect measurements)
RP7 - What are some variables that must be controlled in the reaction time experiment?
The one with the ruler being dropped
-allow ruler to drop without any extra force applied
-gap between thumb to ruler should be the same each time
-measure distance from same position (just above thumb) each time
-use same hand
RP7 - Why might using a computer to test reaction time be better than the ruler dropping experiment?
eg clicking when the screen changes colour
-more precise time reading
-no indication of when the stimulus will appear (eg colour change) like there would be with a human
What is the brain?
an organ with billions of interconnected neurones and has different regions that perform different functions in order to control complex behaviour
Describe the brain’s anatomy and its functions:
-cerebral cortex (consciousness, memory, senses)
-cerebellum (muscle coordination + balance)
-medulla (unconscious activities)
The diagram says cerebrum which is the same as the cerebral cortex
What are 3 methods of studying the human brain?
-study patients with brain damage
-electrical stimulation of parts of the brain
-scanning (MRI/CT/PET)
Why is it hard to study/treat the brain?
-processes too complex to produce drugs that work
-patient must be alive (to stimulate/measure activity)
-need expensive equipment
-encased in skull
What is the eye?
a sensory organ that contains photoreceptors sensitive to light intensity and colour
Describe the eye’s anatomy + functions:
5 parts
-iris (changes pupil gap size)
-cornea (transparent sclera that refracts light)
-sclera (tough white outer layer)
-retina (sensory neurones where image is projected onto)
-optic nerve (sends impulses to brain)
What is accommodation?
lens accommodation is the process of changing the lens’ shape to focus the light from near/distant objects onto the retina
Describe the arrangement of the muscles that surround the lens:
ciliary muscles - outside, circular structure
suspensory ligaments - inside, radial structure, connected to the lens itself
Opposite to pupils’ muscle structure
Describe the process of lens accommodation:
near - lens thickens to refract more, sus. lig. loosens to thicken lens and ciliary contracts which means the ciliary muscles have a smaller diameter
far - lens flattens to refract less, sus. lig. tightens to pull out lens and ciliary relaxes
What is the iris reflex?
process of changing the diameter of the pupil to control the amount of light entering the eye and landing on the retina
Describe the structure of the muscles involved in the iris reflex:
circular muscles - inside
radial muscles - outside
Opposite to lens’ muscle structure
Explain how the iris reflex is used to adapt to differing light conditions:
dim - circular muscles relax, radial muscles contract, pupil dilates
bright - circular muscles contract, radial muscles relax, pupil constricts
Why do eye defects cause a decrease in visual quality?
light doesn’t get focused properly onto the retina
ALWAYS SAY THIS IN A VISUAL DEFECT QUESTION
Describe short sightedness and how it can be treated:
myopia - far objects are blurry, refracts too much because lens is too thick + curved
-wear concave lenses to diverge the light more to negate the strong refracting power of lens, to focus light onto the retina
Describe long sightedness and how it can be treated:
hyperopia - close objects are blurry, can’t refract enough because lens can’t be thickened enough, and image forms behind the retina
-wear convex lens to refract light inwards more, to focus it onto light onto the retina
Give some examples of new technologies that help people with visual defects:
-hard/soft contact lenses
-laser surgery (changes shape of cornea)
-replacement lens in the eye
