Unit 14 Flashcards
what to electrical impulses travel along
neurones
what is a bundle of neurones called
nerves
what does hte central nervous system consist of
the brain and spinal cord
what does the peripheral nervous system consist of
the nerves outside the brain and spinal cord
what is the role of the nervous system in the body
coordination and regulation of body functions
the ability to respond to our surroundings
what is the purpose of sensory neurones
they carry impulses from sense organs to the CNS
structure of sensory neurones
long and have a cell body in the middle of the axon
purpose of relay neurones
they are found inside the CNS and connect sensory and motor neurones
structure of relay neurones
they are short and have a small cell body with many dendrites branching off
purpose of motor neurones
they carry impulses from the CNS to the effectors
structure of motor neurones
they are long and have a large cell body with long dendrites
what are effectors
muscles or glands that produce a response
describe a reflex arc
receptor sends a signal through a sensory neurone where it goes through a relay neurone and is passed on to a motor neurone. the impulse produces a response through the effector
what is a reflex action
it is a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors
advantages of reflex actions
they are quicker than any other type of response and help minimise damage to the body
what is a synapse
a junction where two neurones meet
what are the parts of a synapse
vesicles containing neurotransmitter molecules
the synaptic gap
receptor proteins
describe the events at a synapse
an impulse stimulates the release of the neurotransmitter molecules from vesicles into the synaptic gap
the neurotransmitter molecules diffuse across the gap
neurotransmitter molecules bind with the receptor proteins on the next neurone
an impulse is stimulated in the next neurone
what is the purpose of synapses
to ensure that impulses travel in one direction only
what are sense organs
groups of receptor cells responding to specific stimuli( such as light,sound,touch,temperature,chemicals)
what does the cornea do
refract light
what does the iris do
control how much light enters the pupil
what does the lens do
focuses light onto the retina
what does the retina do
contains light receptors ( rod and cone cells)
what does the optic nerve do
carry impulses to the brain
what is the blind spot and why is it created
it is where nothing can be seen because there are no rod or cone cells. it i found where the optic nerve joins the retina
what happens to the pupils in dim light
pupils dilate to allow as much light in as possible
what happens to the pupils in bright light
they constrict to allow less light in to protect the retina
how do the pupils dilate
radial muscles contract and circular muscles relax
how do the pupils constrict
radial muscles relax and circular muscles contract
what is accomodation
the eye focusing on near or far objects
what happens when objects are close
ciliary muscles contract
suspensory ligaments loosen
lens becomes fatter
light is refracted more
what happens when objects are far from the eye
ciliary muscles relax
suspensory ligaments tighten
lens becomes thinner
light is refracted less
where are cone cells found
in the fovea, near the centre of the eye
what do rod cells do
they are sensitive to dim light
what do cone cells do
they see color
how many different types of cone cells are there
3, they absorb light for different colors
what is a hormone
a chemicla substance produced by a gland and carried by the blood, which alter the activity of one or more specific target organs
what do the adrenal glands produce
adrenaline
where are the adrenal glands found
next to the kidneys
what do the pancreas secrete
insulin
what do the testes secrete
testosterone
what do the ovaries secrete
oestrogen
when is adrenaline secreted
its secreted in ‘fight or flight’ situations
what is the affect of adrenaline
increased breathing rate
increased heart rate
increased pupil diameter
increased blood glucose concentration
diverts blood supply away from unneeded areas
what are the differences between nervous and hormonal control
nervous control is very fast and duration of effect is short
hormonal control is slower and length of effect is longer
where is glucagon secreted from
the pancreas
what is homeostasis
the maintenance of a constant internal environment
what does insulin do
decrease the blood glucose concentration
what is negative feedback
when conditions change from an ideal or set point and these conditions need to be returned to the set point
how does insulin achieve its purpose
it converts extra glucose into glycogen in the liver
what does glucagon do and when is it released?
it increases blood glucose concentration by converting the glycogen back into glucose. happens when blood glucose concentration is low
what is the treatment of diabetes
insulin injections to decrease blood glucose concentration because the body is unable to produce enough insulin on its own
how does the body insulate itself to maintain a constant body temperature
fatty tissue under the skin acts as a layer of insulation to prevent too much body heat being lost
why do we sweat
when its too hot, sweat is secreted by sweat glands to cool the skin.
hairs lie flat against the skin allowing air to frelly circulate and increase heat transfer
why do we shiver
when its cold, skeletal muscles contracts and we shiver which leads to energy being released as heat
erect hairs trap a layer of air around the skin preventing heat loss
what is vasoconstriction
when its cold ,skin capillaries get narrower to reduce heat loss
what is vasodilation
when its hot, skin capillaries get wider to increase heat loss
what is gravitropism
a response in which parts of a plant grow towards or away from gravity
what is phototropism
a response in which parts of a plant grow towards or away from the direction of the light source
what are the tropic responses of the shoots of a plant
shoots have a positive phototropic response and a negative gravitropic response
what are the tropic response of the roots of a plant
they have a negative phototropic response and positive gravitropic response
what does auxin do
hormone that causes cell elongation wherever its concentrated
how does auxin work
its made in the shoot tip
diffuses through the plant from the shoot tip
it is unequally distributed in response to light and gravity
auxin stimulates cell elongation
