Co-ordination and response Flashcards
(62 cards)
1
Q
What is homeostasis?
A
The regulation of conditions inside the body to maintain a constant internal environment in response to changes in the internal or external environment
2
Q
Name some examples of things controlled by homeostasis
A
- core body temperature
- water potential of the blood
- blood pH
- blood glucose levels
3
Q
Stimulus definition
A
a change in the internal or external environment
4
Q
What does a co-ordinated response require?
A
- stimulus
- receptor
- effector
5
Q
Receptor definition
A
Detects the stimulus and generates à nerve impulse which passes along a sensory neurone into the CNS
6
Q
Effector definition
A
a muscle or gland that receives the nerve impulse via the motor neuron from the CNS
7
Q
what two systems work together to co-ordinate response?
A
Nervous and hormonal system
8
Q
Describe the nervous system and how it controls response
A
- made up of nerves and the CNS (brain + spine)
- type of message sent = electrical nervous impulses along neurons
- speed of action = very fast
- duration of effect = short until the nerve impulse stops
- often used in reflexes
9
Q
Describe the hormonal system and how it controls response
A
- made up of glands that secrete hormones into the bloodstream to target organs
- type of message sent= chemical hormones in the bloodstream to target
- speed of action = slower
- duration of effect = long-lasting until hormone is broken down by body
10
Q
what is the CNS made up of and how does it connect to sense organs?
A
- CNS = central nervous system
- made out of the brain and spine
- CNS links to sense organs by sensory neurones in nerves
11
Q
what do sensory, motor and relay neurons do?
A
- sensory neuron = carry impulses from sense organs to the CNS
- relay neurons = pass impulses within the CNS, often between a motor and sensory neuron
- motor neurons = carry impulses from CNS to the correct effector to cause a response
12
Q
what are the three characteristics of reflexes (and so reflex arcs)?
A
- they are RAP
- R = rapid
- A = automatic
- P = protective
13
Q
what happens once receptors in sense organs are stimulated? what are the sense organs?
A
- sense organs = hands, eyes, nose, tongue, ears
- stimulation of receptors in sense organs sends electrical impulses along nerves into and out of the CNS to the correct effectors which will cause rapid response
14
Q
define synapse and briefly describe its role
A
a gap between the dendrites of two neurons, and the role of the synapse, by using neurotransmitters, is to transmit the impulse from the presynaptic membrane to the post-synaptic membrane
15
Q
why are neurotransmitters needed?
A
- in between the dendrites, there is a synaptic gap or cleft
- the electrical nerve impulse cannot travel through this gap so is briefly converted into a chemical message to cross the synaptic cleft
16
Q
what structures in the synapse are specific and complementary? why is this beneficial?
A
- the neurotransmitters found in the vesicle of the first neuron/presynaptic membrane are specific and complementary to the receptor proteins on the post-synaptic membrane
- after the neurotransmitter binds to the receptors on the post-synaptic membrane, they are broken down or recycled
- this allows the nerve impulse to travel unidirectionally
17
Q
describe how nerve impulses are transmitted across synapses
A
- nerve impulse arrives from the axon of the first neuron
- this arrival triggers vesicle with neurotransmitter to fuse with pre-synaptic membrane and release neurotransmitters into the synaptic cleft
- the neurotransmitters diffuse across the synaptic cleft
- when they reach the other side, they bind with the receptors of the post-synaptic membrane, triggering the electrical impulse to occur and transmit along the second neuron
- neurotransmitters are broken down by enzymes to be reused
18
Q
name the steps of the stimulus response pathway in order
A
- stimulus
- receptor
- coordinator
- effector
- response
19
Q
describe a reflex arc of the withdrawal of a finger from a hot object
A
- stimulus is the heat from the hot object
- the temperature receptors in the skin of the hand detect the heat (stimulus)
- this triggers an electrical nerve impulse to be sent down the sensory neuron to the CNS - specifically the spine as it is closer, therefore reducing the time taken for the reflex arc to be completed
- relay neuron within CNS relays nerve impulse through CNS to the correct motor neuron
- motor neuron carries nerve impulse to correct effector (in this case muscles in hand)
- reflex arc is completed when a response by muscle contraction to move hand away from hot object occurs
- reflexes are RAP - rapid, automatic and protective
20
Q
cornea function
A
transparent lens that refracts light as it enters the eye
21
Q
iris function
A
coloured part of the eye visible from the front that contains muscles which control how much light enters the eye by changing the size of the pupil
22
Q
retina function
A
the inner, light-sensitive layer at the back of the eye that contains receptor cells detecting light intensity and colour
23
Q
optic nerve function
A
nerve that carries electrical impulses from the retina to the brain
24
Q
pupil function
A
hole that allows light to enter the eye
25
conjunctiva function
clear membrane covering the sclera and inside of eyelids that lubricate the eye and provides protection from external irritants
26
ciliary muscle function
ring of muscle that contracts and relaxes to change the shape of the lens
27
suspensory ligaments
ligaments that connect the ciliary muscle to the lens
28
sclera function
strong outer wall of the eyeball that keeps it in place by providing an area of attachment for other muscles of the eye
29
fovea function
region at the center of the retina where there is the highest density of light-sensitive receptor cells
30
choroid function
supplies oxygen and nutrients to the retina and prevents light reflection inside the eye
31
what is the blind spot?
where the optic nerve leaves the eye so no light-sensitive receptor cells are present
32
label the parts of the eye
GO ONTO ONENOTE HOME NOTES OF EYE LABELING
33
what is accommodation? why does it work?
- accommodation = the process of focusing on objects by the lens
- the lens is elastic and its shape can be changed by the tightening and slackening of the suspensory ligaments
- the tightening and slackening of the suspensory ligaments occurs due to the contraction and relaxation of the ciliary muscles
34
explain accommodation when focusing on nearby objects
- ciliary muscles contract
- this causes the suspensory ligaments to slacken
- the slackened suspensory ligaments no longer pull on the lens, allowing it to return to its natural fatter shape
- this curvedness of the lens causes light to be refracted more so that it can be concentrated onto the fovea more easily
- this allows the eyes to concentrate on a nearby object
35
explain accommodation when focusing on faraway objects
- ciliary muscles relax
- this causes the suspensory ligaments to tighten
- the suspensory ligaments pull on the lens, causing it to become less curved
- this means that light is refracted less so that it can be concentrated onto the fovea more easily
- this allows the eyes to concentrate on a faraway object
36
why does the lens have to be more curved when focusing on nearby objects? why is this the opposite when focusing on distant objects?
- nearby objects' light rays diverge more, so the eye lens needs to refract them more to focus on the fovea
- faraway objects' light rays are nearly parallel to the lens, so less refraction is required to focus them onto the fovea
37
briefly describe the iris reflex
- iris reflex is an action carried out to prevent damage to the retina
- in dim light (low light intensity), the pupil dilates to allow more light to enter the eye so we can see
- in bright light (high light intensity), the pupil constricts to prevent too much light from entering the eye and damaging the retina
38
what two muscles create an antagonistic pair within the iris?
radial and circular muscles
39
explain iris reflex in low light intensity
- radial muscles contract
- this means that the radial muscles relax
- this causes the pupil to dilate
- more light enters the eye so we can see in the dark
40
explain iris reflex in high light intensity
- radial muscles relax
- this means that circular muscles contract
- this causes the pupil to constrict
- this means less light enters the eye, protecting the retina from damage
41
name three things that the skin does to regulate temperature of body - thermoregulation
- sweating
- vasoconstriction
- vasodilation
42
where is the thermoregulatory center?
hypothalamus
43
explain how sweating aids temperature regulation
- if too hot = sweat glands produce more sweat. this means more sweat evaporates using energy from skin surface so more energy is transferred away from body to surrounding = cooling effect
- if too cold = sweat glands produces less sweat, so less sweat evaporates which means less energy is transferred from the body to surroundings - reducing heat loss
44
explain what the erector pili and skeletal muscles do to aid temperature regulation
- if too hot = no shivering occurs from skeletal muscles, and erector pili muscles relax, causing hairs to lie flat
- if too cold = spontaneous contraction of skeletal muscles causes shivering, which releases heat in body + increases blood and so core body temp as muscles are respiring at higher rates. erector pili muscles contract, causing hairs to stand up, trapping a layer of air that insulates the body so less heat loss by radiation occurs
45
explain vasodilation of skin arterioles - when and how does it happen
- vasodilation occurs when the body is too warm
- blood vessels in the skin are supplied with a greater volume of blood which transfers heat energy to environment by radiation
- blood vessels (arterioles with muscular walls) relax and widen so that they are closer to skin's surface
- more blood flows closer to the skin surface so more heat is transferred to environment by radiation
- this reduces core body temp by reducing blood temp
46
explain vasoconstriction of skin arterioles - when and how does it happen
- vasoconstriction occurs when the body is too cold
- blood vessels in the skin are supplied with smaller volume of blood
- this minimizes transfer of heat to the environment by radiation
- muscles in arteriole walls contract, causing the arteriole to constrict away from the surface of the skin
- this means that less heat flows closer to skin surface so less heat is transferred to the environment by radiation, reducing heat loss
47
source gland and function of oestrogen
- produced by the ovaries
- controls the development of female secondary sexual characteristics
- rebuilds uterus lining
- inhibits FSH production
- stimulates LH production
48
source gland and function of progesterone
- produced in ovaries
- thickens and maintains uterus lining
- inhibits the release of both FSH and LH
49
source gland and function of FSH
- produced by pituitary gland
- stimulates ovaries to release oestrogen
- stimulates the maturation of a follicle containing ova
50
source gland and function of LH
- produced by pituitary gland
- stimulates ovulation by causing a follicle to burst and release ova
51
source gland and function of testosterone
- produced in the testes
- controls the development of male secondary sexual characteristics
52
source gland and function of adrenaline
- produced by the adrenal glands that sit above the kidneys
- prepares body for physical activity
53
source gland and function of insulin
- produced by the pancreas
- lowers blood glucose by helping cells absorb glucose and storing excess glucose as glycogen in the liver
54
what is a tropism?
a directional growth response by plants to changes in environment
55
describe a positive and negative tropic response
- positive tropic response = growth towards stimulus
- negative tropic response = growth away from stimulus
56
what is geotropism? what parts of a plant follow a negative/positive geotropic response?
- geotropism = response to gravity
- plants' shoots are negatively geotropic as they grow against gravity
- plants' roots are positively geotropic as they grow towards direction of gravity
57
what is phototropism? what parts of a plant follow a negative/positive phototropic response?
- phototropism = response to light
- plants' shoots are positively phototropic as they grow towards the light
- plants' roots are negatively phototropic as they grow away from light underground
58
why are geotropism and phototropism beneficial to plants?
- geotropism is beneficial as it allows plants to grow towards mineral ions and water in the soil + anchors the plant in the ground
- phototropism is beneficial as it allows plants to grow towards light to aid photosynthesis
59
what are auxins?
plant growth hormones produced in the growing tip of plants' shoots + roots, and act locally in those areas
60
how do auxins work?
- produced in growing tip of shoot or root
- they then dissolve into the cell fluid and diffuse backwards along the root or shoot
- in shoots they stimulate growth and in roots they inhibit growth
- auxins always accumulate on the lower or shaded side of the growing shoot or root
61
describe the role of auxins in a shoot's phototropic response
- plant shoots are positively phototropic as they grow towards light
- auxins accumulate on the shaded side
- this stimulates the cells to elongate (grow), causing the shoot to bend towards the light
- this only occurs in unidirectional light
- however when light is evenly distributed, then auxins is evenly distributed as there isn't a shaded side
- this causes shoots to grow directly upwards
62
what is a clinostat and how can it be used in experiments with geotropism?
- A clinostat is a rotating device used to cancel out the effects of gravity on a plant by constantly changing the plant's orientation
- It helps scientists study geotropism (gravitropic responses) by showing what happens when a plant can't sense a consistent gravity direction
- usually, no bending occurs.
