Coordination and Response Flashcards
what is a nervous system
coordinates and regulates body function
describe the mammalian nervous system
- the central nervous system (CNS) consisting of the brain and the spinal cord
- the peripheral nervous system (PNS) consisting of the nerves outside of the brain and spinal cord
types of neurons
motor neuron, relay neuron and sensory
what is a motor neurone
long and have a cell body at one end with long dendrites branching off. Carry impulses from the CNS to muscles and glands
cell body
controls the metabolism of nerve cell
dendrites
‘collect’ information from other cells
axon
a long fibre which carries information away from the cell body, sometimes over long distance
fatty sheath made of myelin
gives electrical insulation between neighboring cells and speeds up transmission
end plate
synapses with another nerve cell, a muscle or a gland
what is a sensory neurone
long and have cell body branching off the middle of an axon. Carry impulses from the sense organ to the CNS
what is a relay neurone
short and are located in the CNS, connecting sensory and motor neurones
what’s a reflex action
a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
example of reflex action
moving you hand away from a hot object, coughing, pupil contraction, knee jerk
what’s a reflex arc
the nerve pathway involved in the reflex action
spinal reflex neurone pathway
receptor to sensory neurone to relay neurone to motor neurone to motor neurone to effector (muscle or gland)
what is a nerve impulse
an electrical signal that passes alone neurones. also called action potential
what is a synapse
junction between two neurones between axon terminal of one neurone and dendrite of next
what occurs in the synapse
- impulse goes down neurone
- vesicles with NT move to membrane and fuse with it
- NT is released
- NT diffuses across synaptic gap
- NT binds to a specific protein receptor on the membrane of post-synpatic neurone
- impulse generated in post- synpatic neurone
what are sense organs
groups of receptor cells that detect and respond to specific stimuli
e.g. light, sound touch, temperature, chemicals
examples of sense organs
eyes,ears,skin,nose,tongue
what are receptors
the structure that detects the stimulus
examples of receptors
photoreceptors - light
chemoreceptors (tongue) - chemicals
thermoreceptors (skin) - temperature change
what are transducers
they convert one type of energy (light) into chemical energy of a nerve impulse
cornea
transparent layer- refracts light
iris
the coloured part- expands and contracts to control how much light enters the pupil
pupil
the black part- opening which lets light in
retina
contains light receptors (rods and cones)
lens
refracts light and focuses light on retina
optic nerve
carries impulses from retina to brain (sensory nerves)
blind spot
exit point of nerve- no receptors, so light falling there is not detected
fovea (yellow spot)
has the highest density of cones- offers maximum sharpness- works fully at bright light (located at central part of retina)
ciliary muscle and suspensory ligament
together with the lens, the control focusing of light (accommodation)
how a sharp image is formed on the retina
an image is formed when rays of light from an object are brought together (focused) into the retina
what is accommodation
the ability of the lens system to produce a sharp image of objects at different distances
what happens to the eye distant object
- light needs to be refracted (bent) less
- ciliary muscles relax, eyeball becomes spherical
- ligaments are tight
- lens is pulled long and thin
what happens to the eye
close object
- light must be greatly refracted (bent)
- ciliary muscles contract, pull eyeball inwards (eyeball bulges forward)
- ligaments relax
- lens becomes short and fat
what is the pupil reflex
pupil diameter changes when exposed to different light intensities
- automatic reflex action
how does pupil reflex happen
- in bright light: circular muscles of iris contract – diameter decreases
- in dim light: radical muscles contract + circular relax – diameter increases
what does the retina contain
contains two types of photoreceptors (light sensitive cells) : rods and cones
what are rods
- sensitive to low light intensity/ needed for night vision
- packed around edge of retina
what are cones
- enable to distinguish colour
- 3 types (for red, green, blue)
- work only under high light intensity
- packed at the center of the retina
