Nerves Flashcards
Why do organisms respond to change in environment
- increase chance of survival by responding to changes in external environment
- respond to changes of internal environment to ensure healthy metabolism
- Plants respond also
- any change is called a stimulus
What is a stimulus and how are stimuli detected, and how to this body take action
- receptor cells detect stimuli
- receptors in sensory organs, rod and cone cells in eye detect changes of light
- efectors bring about response to stimuli, usually muscle sells and glands, muscle cells contract and glands secret hormones
Receptors communicate with defectors via central nervous system, hormonal system
What does the central nervous system do and what does it consist of
- spinal cord
- brain
- coordinate a response to stimuli
- motor neuron, sensory neuron and relay neuron
what is the purpose of the reflex action
- reduce chances of being injured
describe pathway of reflex arc from stimuli to response
- stimuli detected, impulse sent along sensory neuron
- passed along to relay neuron via synapse
- relay neuron relays the impulse to a motor neuron
- impulse travels along motor neuron to effecter
- muscle contracts
parts of the eye:
- conjunctiva
- cornea
- iris
- lens
- rods and cones
- optic nerve
conjunctiva - lubricates and protects surface of eye
cornea - refracts light into eye
iris - controls how much light enters the eye
lens - refracts light and focuses onto retina
rods - sensitive to dim lights
cones - sensitive to colour
optic nerve - carries impulse from receptors to brain
what is the iris reflex and why is it needed
- very bright light damages retina, reflex protects it
- light triggers reflex that makes pupils smaller and allows less light in
- BC - bright light, circular muscles contract
- DR - dim light, radial muscles contract
how does the eye work, is the lens fat or thin
- accommodation - changing of lens to adapt to near and far objects
- FAR, far objects ciliary muscles relax suspension ligaments contract, tall and thin
- NOC, near object ciliary muscles contract and suspension ligaments relax
what is a hormone
- Chemical messengers that are sent in the blood
- carried in blood plasma and affect target cells
ADH
- pituitary glands
- increases absorption of water into bloodstream in kidneys
Adrenaline
- adrenal glands, on top of kidneys
- role is to ready body for fight or flight
- increases heart rate, rate of respiration, blood flow to muscles and blood sugar
insulin
- made in pancreas
- control blood sugar levels
- stimulate liver to turn glucose into glycogen
testosterone
- testis
- male sex hormone
- promotes male secondary sexual characteristics, hair and so on, puberty
progesterone
- ovaries
- support pregnancy
- reline uterus
oestrogen
- ovaries
- female sex hormone
- secondary sexual characteristics
- controls menstrual cycle
