homeostasis Flashcards
what is a stimulus
change in an animals surroundings
what is a receptor
the organ which detects the change
what is an effector
muscles are the effectors and they contract
what is the CNS
the central nervous system- consists of the brain and the spinal cord and it coordinates all the nervous responses such as moving or reflexes
what are the three types of neurones
sensory, relay and motor
what is the order of events of an impulse sent from a receptor to the effector
- impulses from the receptor are sent along the sensory neurone
- sent to the CNS
impulse is passed to relay neurones in the CNS - impulse is then passed along the effector via the motor neurone
what is the dendrite
tree like projections which connect to different neurones
what is the axon
long section, electrical impulses travel long distances through this axon
myelin sheath
insulates axon and speeds up the transmission of impulse
what is a reflex
automated actions which do not involve the brain, fast actions which involve the three neurones
what is a synapse
a gap between two neurones where the electrical impulse diffuses across
what is the cornea
a curved transparent disc at the front of the eye and does most of the focusing
what is the pupil
a circular opening whose size is controlled by the iris
what is the iris
a ring of muscle with a hole in the middle. The iris controls how much light enters the eye
what is the lens
soft flexible and transparent. shape can be changed to fine tune the focusing of light onto the retina
what are the ciliary muscles
a ring of muscle at the edge of the eye which circles the lens. when it contracts the lens gets fatter. when it relaxes the lens gets thinner
what are the suspensory ligaments
strong fibres which attach the lens to the ciliary muscles
what is the retina
contains light sensitive cells called rods and cones
what is the optic nerve
consists of many neurones which carry impulses from the retina to the brain
what is the fovea
the region of the retina with the greatest number of cones
what is the conjuntiva
a mucous membrane that covers the eye to prevent infection
describe what happens when you look into bright light
- circular muscles contract
- radial muscles relax
- iris becomes wider
- pupil constricts
describe what happens when you look into dim light
- radial muscles contract
- circular muscles relax
- iris becomes wider
- pupil dilates
describe what happens when you focus on a far away object
- ciliary muscles relax
- suspensory ligaments are pulled tight
- lens is pulled thin and has a less convex shape
- less refraction of light
describe what happens when you focus on a nearby object
- ciliary muscles contract
- suspensory ligaments relax
- lens is not stretched
- more refraction of light
how does hair standing on end help when you are cold
hair traps layer of air which provides insulation for conduction for heat
how does less sweating help when you are cold
less sweat is released therefore less heat loss via evaporation
how does constricting the capillaries help when you are cold
arterioles supplying the capillaries near the surface of the skin get narrower. Less blood will flow through capillaries near the surface of the skin therefore less heat will be lost by radiation
how does hair lying flat help when you are too hot
hair lying flat makes sure an insulating layer of air is not formed
how does sweating help when you are too hot ( vasoconstriction )
when sweat is evaporated heat energy is taken away from the skin as evaporation of water requires energy
how does widening the arterioles help when you are too hot ( vasodilation)
arterioles supplying the capillaries near the surface of the skin get wider. More blood will through capillaries near the surface of skin therefore more heat will be lost by radiation
what is osmoregulation
the regulation of water levels within the body to keep rising or falling too much
what happens when your water levels are low
- water levels are detected by the hypothalamus in the brain
- more ADH is sent from the pituitary gland
- ADH makes the collecting duct in the nephron more permeable
- more water is reabsorbed back into the body
what is positive phototropism
growth towards the light
negative phototropism
growth away from the light
positive geotropism
growth downwards with gravity
negative geotropism
growth upwards against gravity
what happens when light is shone on the plant from one side
- auxins are produced in the tip of the plant
- auxins diffuse to the shady side of the plant so they don’t get destroyed
- the auxins cause the cells on the shady side of the plant to elongate more
- this results in the plant to grow and bend towards the light
what is a hormone
a chemical messanger that are made in the glands
How are hormones transported
in the bloodstream in the plasma
What is ADH
increases permeability of collecting duct in the nephron so more water reabsorption into the blood
Where is ADH released from
pituitary gland
what is the ADH target organ
Kidney
What is Insulin
convert glucose to glycogen
lowers blood sugar levels
Where is Insulin released from
the pancreas
What is the target organ for insulin
Liver
What is Adrenaline
triggers fight or flight response by making heart beat faster
Where is Adrenaline released from
adrenal gland
What is the target organ for adrenaline
heart / liver
Descriptions of the endocrine ( hormone ) system
- speed
- length of response
- how it travels
- signal made of
- target
- slow
- long term response
- in the blood plasma
- chemical
- all around the body
descriptions of the nervous system
- speed
- length of response
- how it travels
- signal made of
- target
- fast
- short term response
- diffusion, along neurones
- electrical impulse
- specific area
What is an Auxin
plant growth substance
How do auxins work
- diffuse to other parts of roots or shoots
- change the rate of elongation in plant cells
How does the plant growth change when light is being shone on one side of it
- sunlight destroys auxins so they diffuse away from the light
- auxins cause elongation on the shady side of the plant causing shoot to bend towards the light
what is positive phototropism
shoot grows towards light source
what is negative phototropism
shoot grows away from light source
what is positive geotropism
roots grow towards gravity
what is negative geotropism
roots grow away from gravity
how does geotropisms ( auxins in the roots ) work
- auxins inhibit cell growth
- auxins gather at the bottom of the root because of gravity
- slows cell growth so root bends down
