B10 Homeostasis/nervous system Flashcards
what do enzymes need in order to work?
very stable conditions
what is homeostasis?
the regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
what is homeostasis used for in humans?
to keep the blood glucose level, temperature and water levels constant
what does homeostasis consist of?
automatic control systems that make sure the internal conditions of the body stay constant
what do automatic control systems involve?
the nervous systems or hormones
what do receptor cells do?
detect changes to the environment
this could be the internal or external environment
what is a stimulus?
a change to the environment
what is a coordination centre?
it receives and processes the information from the receptor cells
what is the job of an effector?
carry out the response (restore the optimum level/condition)
what is an effector?
a muscle or gland
what is the central nervous system (CNS)?
the brain and spinal cord
what is the peripheral nervous system?
the nerves running to and from the CNS
what are the parts of a reflex arc?
receptor
sensory neurone
CNS
relay neurone (in the CNS)
motor neurone
effector
response
what is a synapse?
a junction between two neurones
how do synapses work?
when an electrical impulse reaches the synapse, a chemical is released
this diffuses over the gap (synapse) between the two neurones and triggers an electrical impulse to be sent down the next neurone
what do reflexes do?
help protect from danger as they are very rapid
what is a reflex action?
an automatic and rapid response to a stimulus
what is the independent variable in the reaction time practical?
the person being tested
what is the dependent variable in the reaction time investigation?
reaction time
what are some control variables in the reaction time investigation?
starting distance between the thumb and the first finger should be kept constant
always measure from the top of the thumb
conditions in the room
what are some other possible independent variables for the reaction time investigation?
the effect of practice (a person catches the ruler a large number of times and look to see if the reaction time changes depending on the number of tries)
the hand catching the ruler
if chemicals have an effect on reaction time
what does the brain control?
complex behaviours
what is the cerebral cortex?
the highly folded outer layer of the brain
what is the function of the cerebral cortex?
language
memory
consciousness
what is the function of the cerebellum?
it coordinates movement and controls balance
what does the medulla control?
heart rate
breathing rate
what are three parts of the brain?
cerebral cortex
medulla
cerebellum
why is it difficult to study or treat the brain?
it is protected by the skull so difficult to access
the structure is complex so it is difficult to figure out which parts do what
it is extremely delicate and easy to damage
what are the ways to study the brain?
look at patients with brain damage
electrical stimulation
MRI
what is the eye?
a sense organ sensitive to light intensity and the colour of light
what is the function of the cornea?
start focusing the light rays
what is the function of the lens?
focus the light rays onto the back of the eye
what is the function of the retina?
it contains receptor cells that allow us to detect light intensity and colour
what does the sclera do?
protects the eye
what is the function of the ciliary muscles and suspensory ligaments?
they help change the shape of the lens, allowing us to see distant and near objects
what is the pupil?
the space in the centre of the iris which lets light pass through
what is the function of the iris?
it controls the size of the pupil
what does the iris reflex action do?
it protects the retina from bright light and allows more light into the eye when it is dark
how does the iris reflex action work?
if the conditions are dark, the light intensity receptors sense this and send a message to the brain.
the brain then sends a signal to certain muscles in the iris to contract, making the pupil larger to let more light into the eye.
the opposite happens if conditions are bright
what is accomodation?
when the lens in the eye changes shape to focus on distant or near objects
what happens when the ciliary muscle is contracted?
the suspensory ligaments loosen.
this causes the lens to thicken and refract light more strongly
what happens when the ciliary muscles loosen?
the suspensory ligaments are pulled tight
this causes the lens to flatten and refract light less strongly
what needs to happen to light from distant objects?
it needs to be refracted a relatively small amount
what needs to happen to light from near objects?
it needs to be refracted a large amount
what can cause hyperopia?
the eyeball is too short so the light is focused behind the retina
or
the lens becomes less elastic
what can be used to treat hyperopia?
convex lenses
they partially refract the light before it enters the eye
what can cause myopia?
the eyeball can be too long so the light focuses in front of the retina
or
the lens is too thick
what can be used to treat myopia?
concave lenses
these partially unfocus the light rays before entering the eye
what can also be used to treat vision problems?
hard or soft contact lenses
laser surgery changes the shape of the cornea
the lens inside the eye can be replaced
what controls body temperature?
the thermoregulatory centre in the brain
how does the body detect temperature?
the thermoregulatory centre in the brain has receptors sensitive to the temperature of the blood
the skin also has temperature receptors which send signals down sensory neurones to the thermoregulatory centre in the brain
what does sweat do?
it is released from sweat glands and pools on the surface of the skin
when it is evaporated away, it takes energy away from the body and cools it down
what is vasodilation? what does this do to the body’s temperature and how?
the blood vessels supplying the capillaries dilate so more blood flows through the capillaries
this means heat transfers out of the blood, cooling the body down
what is vasoconstriciton? what does this do to the body’s temperature and how?
the blood vessels supplying blood to the capillaries in the skin constrict
less blood now flows through the capillaries so less heat is lost
this causes the body to stay warm
how does shivering increase the body’s temperature?
the skeletal muscles contract
to generate energy for this contraction, the cells increase the rate of respiration
this releases heat to warm the body
