focus/accommodation on an object
- cornea and aqueous humour (in aqueous chamber) refract light rays onto lens
- lens further refracts and converges light rays on retina
◦ light rays must converge on retina to form a clear image
◦ shape of lens must change to converge light rays on retina - image is upside down, laterally inverted and smaller
what is focusing/accommodation
= adjustment of lens of the eye so that clear images of objects at diff distances are formed on the retina
what is pupil reflex
= reflex action which is protective in nature
diff between circular and radial muscles
circular muscles
= arranged in a circle around pupil
vs (antagonistic muscles)
radial muscles
= radiate outwards from pupil
what is sensitivity, stimulus and response
- an organism can react to changes in its environment
|
change in environment that causes reaction in an organism = stimulus
|_ response
what does central nervous system consist of
-> consists of brain + spinal cord
what is the role of the brain in CNS
integrates visual, auditory, touch, olfactory and taste information from sensory organs
what is the role of the the spinal cord in CNS
involved mostly in automatic actions known as reflex actions
processes of CNS
- when there is a stimulus, receptors in our sense organs are stimulated to produces nerve impulses
- nerve impulses are transmitted by nerves to CNS
- CNS sends nerve impulses to effectors (either muscles/glands)
what are receptors
specialised structures that detect stimuli and generate nerve impulses, which can be transmitted around the body via nerves in nervous system
what do sensory neurons do
= transmits nerve impulses from receptors to CNS
features of sensory neurons
-> circular cell body
|_ contains nucleus, cytoplasm, cell surface membrane and organelles
-> one long nerve fibre between receptor and cell body
-> one short nerve fibre between cell body and CNS
what do relay neurons do
= transmits nerve impulses within CNS
what do motor neurons do
= transmits nerve impulses from CNS to effectors
features of motor neurons
-> irregular-shaped cell body
-> one long nerve fibre between cell body and effector
what is reflex action
= immediate response to a specific stimulus without conscious control
diff between voluntary and involuntary actions
voluntary -> controlled consciously
involuntary actions -> not controlled consciously
reflex action - cranial vs spinal reflexes
- cranial reflexes
-> controlled by brain - spinal reflexes
-> controlled by spinal cord
*brain and spinal cord are reflex centres
what is reflex arc
= shortest pathway by which nerve impulses travel from receptor to effector in a reflex action
what does peripheral nervous system consist of
-> consists of cranial and spinal nerves + sense organs
