unit 14 - coordination and response Flashcards
what is a nerve
a bundle of neurons
where are electrical impulses sent through
through nerves to quickly send signals around the body
what are nerve electrical impulses used for
examples (5)
for rapidly coordinating or regulating the bodies functions
eg pupils dilate, breathing contractions, bladder relaxes, stomach digestion, heart rate.
what does the central nervous system consist of
brain and spinal cord
function and look of dendrites
receive signals from surrounding neurons . they are branches to allow connections with many neurons
function of axon
a long structure off the cell body that electrical signals can rapidly be sent through. its long length allows for signals to be sent rapidly
what is the axon terminal
where the signal is passed to the next neuron over the synapse
4 steps of reflex responses / how nerve signals are sent
- a stimulus is received by a receptor
- sensory neurons pass these signals back to the relay neuron in the CNS
- relay neuron sends this signal on to the motor neuron
- motor neuron sends the signal to an effector organ which is then stimulated to respond.
stimuli examples
light, sound, touch, temperature, chemicals.
what is a reflex action
a means of automatically and rapidly integrating and coordinating stimuli with the response of effectors
what are effector organs
muscle or gland
where is cell body on a sensory neuron
half way down axon
defining look of relay neuron
short axon
where is cell body on motor neuron
at end with dendrites
what is the synapse
the junction between 2 neurons
what does the presynaptic cell do
releases neurotransmitters into the synaptic cleft, which then bind to receptors on the postsynaptic cell, triggering a response
how electrical impulses trvael from neurone to neurone
- electrical impulses trvael along the first axon
- this triggers the nerve ending of the presynaptic neurone to release neurotransmitters from vesicles which fuse with the presynaptic membrane
- neurotransmitters diffuse across the synaptic cleft and bind with the receptor molecules on the postsynaptic membrane
- thus stimulates 2nd neurone to generate and electrical impulse that trvales down the 2nd axon
why are neurotransmitters destroyed
to prevent continued stimulation which would cause repeated impulses to be sent
why do impulses only travel one way
neurotransmitters are released from the presynaptic end only and their receptors are present on the postsynaptic end only
function of the optic nerve
sends nerve signals from rod and cone cells in the retina to the brain.
function of the retina
is where light is focused in the eye. it contains light sensitive rod and cone receptor cells
function of the iris
is the coloured part of the eye which affects pupil size
function of the lens
is able to change shape to focus light on the retina
function of pupil
is the opening in the eye which allows light to enter
function of cornea
the curved part of the eye which refracts light as it enters
function of the suspensory ligaments
attaches the lens to the ciliary muscles
function of the ciliary muscles
they contract or relax to make the suspensory ligaments go slack or tight respectively, therefore changing the shape of the lens.
what happens to eye in low light
radial muscles contract in low light so the pupil will appear larger and allow more light in
what happens to eye in bright light
circular muscles contract in bright light so the pupil will appear smaller and less light enters eye
why do pupil size change in light
means light sensitive cells of the retina would gave an appropriate amount of light to be able o send impulses to the brain along the optic nerve to form the image you see.
about rod cells
- detect differences in light intensity
- don’t detect colour
- used extensively in dim light
about cone cells
- detect differences in colour
- red, green, blue cones work together to allow us to perceive a range of colours.
where is information carried from the eye
sensory neurons to the occipital lobe.
what is the fovea
in the eye a tiny pit in the retina that provides the clearest vision. the eye lense will focus light onto the fovea
- no rods only cones
definition of hormones
a chemical substance , produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
what does the pituitary release/excrete
releases ADH
what do the adrenal glands produce
adrenaline
what does the pancreas produce
insulin and glucose
what do the testes produce
testosterone
what do the ovaries produce
oestrogen
changes when adrenaline is released (5)
- increased breathing rate + deeper breathes
- increased heart rate
- increased pupil diameter - can see more
- hair stands on end- making animal look larger
- glucose is released from the liver
short vs long term signal
nerve : send signals fast through neurons , effect is short term
hormones: send signals slowly through blood stream.
hormones that control glucose levels (3)
- adrenaline
- glucose
3.insulin
how does adrenaline help control blood glucose levels
is secreted from adrenal gland, causes liver to break down glycogen and release glucose into the blood stream
how does glucagon help control blood glucose levels
secreted from pancreas. causes the liver to breakdown glycogen into glucose and release it into the blood stream
its the hormone we use when our blood sugar levels are low but we are not in fight or flight.
how does insulin help control blood glucose levels
secreted from pancreas causes the liver to absorb glucose from the bloodstream and covert it to glycogen for later use.
used when blood sugar levels are high
insulin flow chart
eat a large meal
blood sugar levels rise
pancreas releases insulin
insulin travels through blood to liver
this stimulates liver to absorb glucose from blood and convert to glycogen
lowers blood sugars again
describe how eyes adjust to focus on something far away (5)
- suspensory ligaments become taut
- ciliary muscles relax
- image forms on fovea
- lens thinner
- less refraction of light
describe how urea is transported in the blood to the kidney
soluble in plasma
homeostasis defenition
the maintenance of a constant internal environment
what does insulin do to blood glucose concentration
decrease
What is the purpose of Homeostasis?
keeps a variable in our body at a set point using negative feedback.
what triggers homeostasis
if a variable changes from the set point it will be detected by a receptor, transmitted by nerves and an effector will be activated to return the variable to its set point.
How is temperature sensed in the body and prompted to be regulated
- the thermoregulatory centre in the hypothalamus senses the temperature of the blood flowing through it
- the hypothalamus also receives information via sensory neurones from heat receptors in the skin.
How is vasodilation triggered
if body temperature rises
steps of vasodilation
- smooth muscle in wall of arteriole relaxes and arteriole dilates
- more blood flows through capillaries close to surface of the skin
- less blood flows through shunt vessel
rate of heat loss from body increases
what triggers vasoconstriction
when body temperature falls
steps of vasoconstriction
- smooth muscles in wall of arteriole contracts which constricts the lumen
- more blood is shunted away from surface of skin
- less blood flows close to the skin
rate of heat loss from body decreases
steps of sweating
- sweat is secreted onto surface of skin
- water in sweat absorbs heat from the body as it evaporates
this increases the rate of heat loss from the body
purpose/ setps of goosebumps
pili erector muscles contract and hairs stand up straight
still layer of insulating air is trapped by the hairs
how does shivering keep you warm
when we shiver the muscles contract repeatedly so the rate of respiration in muscles increase. uses lots of energy and more heat energy is generated
ways to warm up and cool down
warm up
1. shivering
2. goosbumps / pili erection
3. vasoconstriction
cool down
1. vasodilation
2. sweating
What is tropism
a growth a response of an organism towards or away from a stimulus
describe gravitropism
a response in which parts of a plant grow towards or away from gravity
describe phototropism
a response in which parts of a plant grow towards or away from the direction of the light source
positive vs negative tropism
towards vs away
what is auxin
a growth regulating hormone. it makes plant shoot cells elongate and inhibits elongation in roots.
What does auxin do in shoot tips
loosens the cell wall and stimulates cell elongation. in the shoot tip iir diffuses away from light, elongating cells on shaded side so shoot grows towards the light.
