Homeostasis and Response Flashcards
what is negative feedback?
returning body conditions back to normal
define homeostasis
maintenance of a constant internal environment
how is water content controlled in the body?
water is absorbed from food and drink and lost via sweat, urine. and breathing
why is water content controlled in the body?
to maintain concentration gradient for effective osmosis so cells won’t be damaged by too much/little water
how is ion content controlled in the body?
ions are absorbed from food, so amount eaten, and are lost via sweating
why is ion content controlled in the body?
ions are needed in the body
how is temperature controlled in the body?
behaviour and vasoconstriction/dilation
why is temperature controlled in the body?
to keep enzymes healthy and working efficiently
how are blood glucose levels controlled in the body?
food intake, amount of respiration, glucagon, insulin
why are blood glucose levels controlled in the body?
glucose is necessary for respiration
how is co2 concentration in the blood controlled by the body?
rate of respiration and breathing
why is co2 concentration in the blood controlled by the body?
co2 is toxic and can damage cells
what is the homeostasis response pattern?
- stimulus
- receptor
- sensory neurone
- coordination centre
- relay neurone within coordination centre
- motor neurone
- effectors
- response
what is a stimulus?
change in environment away from optimum conditions
what is the coordination centre?
structures which receive and process info from receptors
what are receptors?
cells which detect a stimulus
what are effectors?
organs which carry out response to stimulus
what is the response in the homeostasis response pattern?
return to optimum conditions by causing a muscle to contract or gland to secret hormones
where do sensory neurones transmit information between?
from the receptor cells to the CNS
where do relay neurones transmit information between?
inside the CNS, transmit impulses from the sensory neurone to the motor neurone
where do motor neurones transmit information between?
from the CNS to the effectors
why are reflexes faster?
they don’t involve conscious thought and use the nearest part of the CNS
what do all control systems include?
- receptors which detect stimuli
- coordination centre (eg brain, spinal cord, pancreas) which receives and processes information from receptors around the body
- Effectors to bring about responses to restore optimum levels
what are the features of nerve cells?
- long fibre (axon) insulated by a fatty (myelin) sheath - can carry messages up and down the body.
- Tiny branches (dendrons) which branch further as dendrites at each end - receive incoming impulses from other neurones.
what is a reflex?
automatic and rapid response to a stimulus to minimise any damage to the body from potentially harmful conditions - does not involve the conscious part of the brain, which makes it much quicker.
what is the reflex arc?
stimulus ⇒ receptor ⇒ sensory neurone ⇒ relay neurone ⇒ motor neurone ⇒ effector ⇒ response
what is a synapse?
microscopic gap where 2 neurones meet
how do impulses travel across synapses?
- electrical impulse travels along first axon.
- triggers nerve-ending of neurone to release neurotransmitters.
- diffuse across synapse and bind with receptor molecules on post-synaptic membrane
- receptor molecules on second neurone bind only to the specific neurotransmitters released from the first neurone.
- stimulates the second neurone to transmit the electrical impulse.
what are the 3 parts of the brain?
medulla, cerebral cortex, cerebellum
what does the medulla do?
controls automatic actions eg heartbeat, breathing
what does the cerebellum do?
co ordinates movement and balance
what does the cerebral cortex control?
consciousness, intelligence, memory, language
what are some brain disorders that can be investigated and treated?
- cancer
- epilepsy
- dementia
- paralysis
what are some treatments for brain disorders?
- surgery
- electrical stimulation
- chemotherapy
- medication
how are brain disorders investigated?
- surgery
- MRI scans
- x-rays
- thermal imaging
what are some difficulties in investigating and treating brain disorders?
- infection
- injury - brain damage eg nerves, blood vessels
- very complex
- long operations
what are the benefits of procedures carried out on brain and nervous system?
- treat the patient
- increases understanding for the future
- helps develop new procedures and medicines
what are the risks of procedures carried out on brain and nervous system?
- permanent brain damage
- loss of function of parts of body
- memory loss
- paralysis
what are the parts of the eye?
- ciliary muscle
- lens
- vitreous humour
- retina
- sclera
- choroid
- fovea
- optic nerve
- suspensory ligaments
- rods
- cones
- iris
- pupil
- cornea
- conjunctiva
- aqueous humour
what are the cones in the eye?
3 types - RGB - to see in colour
what is the ciliary muscle?
muscle in the eye attached to ligaments which pulls on ligament to change shape of lens to alter amount of refraction done
what is the function of the vitreous humour?
keeps eyeball spherical
what is the retina?
a clear transducer in the eye where receptor cells are - cones and rods
what is the choroid?
a black layer of tissue at the back of the eye
what is the sclera?
the mainly white outer layer of the eye which protects it
what is the fovea?
where light needs to be focussed in the eye
what is the optic nerve?
very wide nerve to carry clear impulses to brain
what are suspensory ligaments?
attached to lens - changes shape with muscles
what is the lens?
made of curved cells and refracts light
what is the function of rods in the eye?
seeing in monochrome
what is the iris?
circular protein muscle which is able to contract and relax to change size of pupil
what is the aqueous humour?
a gel-like substance which keeps the eye’s curves in place
what is the conjunctiva?
thin layer of tissue which protects lens and cornea
what is the cornea?
clear and curved to refract light
what is the pupil?
a hole that changes size/shape to control amount of light that enters the eye
what are the type of muscles that work opposite to each other?
antagonistic
when the pupil is dilated, are the circular muscles relaxed or contracted?
relaxed
when the pupil is dilated, are the radial muscles relaxed or contracted?
contracted
when the pupil is constricted , are the circular muscles relaxed or contracted?
contracted
when the pupil is constricted, are the radial muscles relaxed or contracted?
relaxed
what is the purpose of the pupil reflex?
so the right amount of light enters the eye, to prevent damage to retina
what is accomodation?
the process by which the lens changes shape to make sure the light focuses on the retina
what changes in the eye to focus on a near object?
- ciliary muscles contract and have a smaller diameter
- suspensory ligaments become looser and slacken
- lens becomes thicker and more rounded - more convergent
- light is refracted more - more curved lens
what changes in the eye to focus on a far object?
- ciliary muscles relax and have a thicker diameter
- suspensory ligaments tighten and become thinner
- lens become longer and thinner - less convergent
- light is refracted less - less curved lens
what is myopia?
short-sightedness
what causes myopia?
the lens is too strong (too round) or the eye is too long so too much refraction is done and light rays meet before the retina