Organisms respond to changes Flashcards
1
Q
Stimulus
A
something detected by an organism- internal or external
2
Q
Receptor
A
organ or specialised cell that can detect the change that is causing the stimulus
3
Q
Response
A
movement or change in behaviour as a result of the stimulus
4
Q
Taxis
A
a response which involves movement in a specific direction- positive= towards
5
Q
Kinesis
A
a response that involves movement in random directions. The speed and frequency of direction change increase in order to increase the chance of entering favourable conditions.
6
Q
Simple reflex arc process
A
Stimulus -> receptor -> sensory neurone -> intermediate neurone -> motor neurone -> effector -> response
7
Q
sensory neurone
A
carries the nerve impulse from the receptor to the spinal cord
8
Q
intermediate neurone
A
located entirely in the spinal cord and relays the nerve impulse from the sensory neurone to the motor neurone
9
Q
motor neurone
A
carries the impulse from the spinal cord to the effector which can be a muscle or gland
10
Q
Pancial corpuscle
A
located deep in the skin, found on fingers, soles of feet, joints etc.
11
Q
Pancian corpsucle structure
A
They have a single sensory neurone located in the layer of connective tissue called llamele which forms layers separated by gel. It contains stretch mediated sodium ion channels in the cell surface membrane.
12
Q
What happens when sodium ion channels are under pressure
A
the channels become deformed and open to allow the rapid influx of sodium ions. This changes the membrane potential causing it to become depolarised.
13
Q
What happens when sodium ion channels are not under pressure
A
The sodium ion channels are closed
14
Q
What does membrane depolarisation cause
A
generator potential then action potential (nerve impulse)
15
Q
What does the lens of the eye do
A
focuses light on the retina where photoreceptors are located
16
Q
where are photoreceptors located
A
on the fovea on the retina
17
Q
Why is there a blind spot where the optic nerve leaves the eye
A
no photoreceptors there
18
Q
what are the 2 types of photoreceptors and what to they do
A
cones- colour vision
rods- b&w vision
19
Q
Describe cone cells
A
they are present at the greatest density in the fovea and contain the pigment iodopsin.
Not sensitive to light so requrie bright light to work
3 types which are sensitive to the 3 primary colours
Each cone has its own synapse via a bipolar neurone
20
Q
Describe rod cells
A
highest density outside the fovea and contain the pigment rhodopsin
They are very sensitive to light and so are stimulated in low light conditions
Rod cells share synapses with a bipolar cell
So multiple rods must be stimulated to cause the generator potential
21
Q
how is the heart myogenic
A
it initiates its own contraction
22
Q
what is the sinoatrial node
A
specialised fibres in the wall of the right atrium
23
Q
what does the sinoatrial node do
A
initiates a wave of electrical exitation
24
Q
describe the process when the sinoatrial node initiates the wave of electrical exitation
A
wave of exitation causes the atria to contract
ventricles don’t start contracting until after this as the tissue at the base of the atria is not conductive
there is a pause to allow the atria to empty
wave reaches AV node between the atria
wave is produced by the AV node and passed to ventricles, down the bundle of His to the apex of the heart
The bundle of His branches into Purkyne fibres which carry the wave upwards, causing ventricles to contract from the bottom.
cells repolarise and muscle relaxes
25
how does temperature affect the speed of an action potential
ions have more kinetic energy at a higher temperature
so they move faster
enzymes involved in respiration work faster so there is more ATP for the Na+/K+ pump
But if it's too high, proteins in the membrane will denature
26
How does the mylein sheath affect action potential
myelin stops the diffusion of potassium and sodium ions so depolarisation cannot occur
Action potentials occur only at the nodes of Ranveir
Action potentials 'jump' from one node to the next- saltatory conduction
27
what is the name of the type of conduction when the myelin sheath is present
saltatory conduction
28
How does the axon diameter affect action potential
greater diameter = less resistance so more sodium ions can flow through
so depolarisation occurs more rapidly
there is less leakage
29
What happens when an action potential reaches the presynaptic reigon
voltage sensitive calcium ion channels open and calcium ions move in down a conc. gradient
30
name of vesicles containing the neurotransmitter in the presynaptic reigon
acetyle choline (Ach)
31
what happens when calcium ions enter the presynaptic reigon
they bind with the vesicles (Ach) and move towards the membrane
vesicle fuses with membrane and releases the neurotransmitter across the synaptic cleft
32
how are calcium ions moved out of the presynaptic reigon
by active transport producing ADP and Pi
33
what happens when Ach reaches the post synaptic reigon
it binds to the complementary receptor which causes the sodium ion channels to open
so Na+ moves into the post-synaptic reigon
34
what happens if sufficient Na+ enters the post synaptic reigon
an action potential is generated
35
which enzyme removes Ach in the cleft
acetylcholinesterase
36
what is acetyl choline hydrolysed into and what happens to it
choline and acetyl it is reabsorbed into the presynaptic reigon and made back into Ach
37
why are there many mitochondria in the presynaptic reigon
reforming acetyl choline uses ATP
so cacium ions can be actively transported out the cells
38
summation meaning
the buildup of neurotransmitters in the synapse to generate an action potential
39
why is summation needed
some action potentials do not result in enough neurotransmitter being released to generate a new action potential
40
spatial summation meaning
many different neurones collectively trigger a new action potential by combining the neurotransmitter they release to exceed threshold
41
temporal summation meaning
one neurone releases neurotransmitter repeatedly over a short period to reach threshold
42
How does inhibiton work
A negative inhibitory neurotransmitter enters the postsynaptic reigon which means the potential is further away from the threshold
43
what do agonist drugs do
bind to the post synaptic reigon and initiate the action potential to increase cellular activity
44
what do antagonist drugs do
block the post synaptic receptor to stop the neurotransmitters binding to decrease cellular activity
45
positive tropisms
grow towards the stimulus
46
what controlls tropisms
Growth factors e.g indoleacetic acid (IAA)
47
What is IAA
A type of auxin which controls cell elongation in shoots and inhibits growth in roots. It can also diffuse into other cells
48
what happens if there is unilateral light on a shoot
IAA will diffuse towards the shaded side causing the shoot to elongate more here and grow towards the light
49
what happens if light hits the roots
IAA moves towards the lower side so the roots bend away from the light and anchor more
50
How do shoots respond to gravity
IAA diffuses to the lower side which causes cell elongation so the plant grows upwards (negative gravitotropism)
51
How do roots respond to gravity
IAA moves to the lower side of roots stopping growth here so roots grow downwards
52
PNS vs CNS
CNS includes the brain/ spinal cord but PNS includes receptors, sensory and motor neurones
53
what kind of channel proteins are there in the pancial corpsule cell membrane
stretch-mediated sodium ion channels
54
how is a generator potential formed in rod cells
light energy causes the pigment rhodopsin to be broken so the threshold is met in the bipolar cell
55
what is an example of spatial summation
many rod cells are connected to a single bipolar cell
56
why does spacial summation result in retinal convergence
since many rods are connected to one bipolar cell, the brain can't tell which light source stimulated it, leading to poor visual acuity
57
main difference between rhodopsin and idopsin
idopsin is only broken down if there is high light intensity
58
why are cone cells located on the fovea
they require high light intensity and there is the highest light intesnsity here as this is where light is focues by the retina
59
what is heartrate controlled by
the autonomic nervous system in the medulla oblongata in the brain
60
what increases heart rate
the sympathetic nervous system
60
what decreases heart rate
the parasympathetic nervous system
61
what detects pH in the blood
chemoreceptors
62
what detects blood pressure
baroreceptors
63
what happens if blood pressure is too high
the artery walls can become damaged
64
what happens if blood pressure is too low
may not be enough oxygen delivered to respiring tissues or removal of waste
65
what happens if there is too much carbon dioxide or lactic acid in the blood
blood pH drops and this can denature enzymes
66
what happens if there is low blood pressure
baroreceptors detect this so are stretched less
more electrical impulses are sent to the medulla
then impulses are sent by the sympathetic nervous system to the SAN (effector)
so the heart rate increases
67
what happens if there is high blood pressure
baroreceptors detect this so are stretched more
more electrical impulses are sent to the medulla
then impulses are sent by the parasympathetic nervous system to the SAN (effector)
so the heart rate decreases
68
where are baroreceptors and chemoreceptors found
wall of aorta and carotid artery
69
response for low blood pH
chemoreceptors detect this
more impulses are sent to the medula then to the SAN via the sympathetic nervous system
heart rate increases
70
what is the myelin sheath made of
Shwann cells
71
what is the shwann cell made of
lipid
72
what are the gaps between the myelin sheath called
nodes of ranvier
73
what is the resting potential
the potential difference between the electrical charge inside and outside the neurone when there is no impulse
74
what is the resting potential
-70mV
75
why is the resting potential negative
there are more positive ions outside than inside the cell
76
how is resting potential maintained
sodium/potassium ion pump moves 2K+ in and 3Na+ ions out (using ATP)
this creates an electrochemical gradient so K+ diffuses out and Na+ diffuses in
but more K+ moves out as the membrane is more permeable to it
77
what is an action potential
when a neurone's voltage increases beyond threshold (depolarisation), generating a nervous impulse
78
why does depolarisation occur
the membrane becomes more permeable to sodium ions
79
what effect does a stimulus have on an axon
it causes the sodium voltag-gated ion channels to open
80
what happens to an axon when a stimulus is detected
sodium voltage-gated ion channels open
Na+ diffuses in, meaning the axon is more positive
so more Na+ channels open
81
what happens when the threshold in an axon is reached
voltage-gated sodium ion channels close and voltage-gated K+ ions open
K+ moves out and the axon is repolarised
82
what is hyperpolarisation
after polarisation, when K+ moves out the axon it temporarily becomes more negative than the resting potential
K+ gates close and the resting potential is restored
83
what is the all or nothing principle
an action potential is only produced when a stimulus exceeds the -55mV threshold
stronger stimuli don't exceed the maximum voltage, instead then generate more action potentials
84
what is the refractory period
after an action potential is generated, there is a period where it can't be stimulated as the sodium ion channels are recovering
85
why is the refractory period important
it ensures each action potential is separate
it ensure action potentials travel in one direction
it limits the number of transmissions to prevent overreaction
86
why is saltatory conduction important
it means action potentials jump from node to node so they don't have to travel down the whole axon
87
why can nerve impulses only travel in one direction
only receptors on the postsynaptic reigon and only vesicles/neurotransmitters in the presynaptic reigon
88
what does an inhibitory synapse do
causes chloride ions to move to the postsynaptic reigon so K+ moves out. This causes hyperpolarisation so an action potential is unlikely.
89
what is a neuromusclular junction
a synapse between a motor neurone and a muscle
90
features of a neuromusclular junction
only excitory
connect a motor neurone and a muscle
end point of an action potential
Ach binds to receptors on muscle fibres
unidirectional
91
features of a cholinergic synapse
connect two neurones (any type)
can be excitory or inhibitory
new action potential is generated in the next neurone
unidirectional
Ach binds to receptors on the post synaptic membrane
92
structure of myofibrils
made up of fused cells which share nuclei and cystoplasm (sarcoplasm)
93
how do muscles work
in antagonistic pairs against an incompressable skeleton to create movement
94
what are muscle fibres made from
millions of microfibrils which bring about the force to create movement
95
what proteins are found in the mucle cell
myofibrils
96
what is the cell membrane called in a muscle cell
sarcolemma
97
what is a tendon
non-elastic tissue which connects muscle to bone
98
what are motor end plates
end of the motor neurone which attach to a musle cell and can activate it
99
can a neuromuscular junction be inhibitory
no
100
what are the thick myofibril filaments called
myosin
101
what are the thin myofibril filaments called
actin
102
sarcomere meaning
distance between z bands in muscle
functional unit of a myofibril
103
what happens to the sarcomere when the muscle contracts
shortens as myosin slides between actin
104
evidence supporting the filament hypothesis
I band becomes narrower
H zone becomes narrower
sarcomere shortens
105
what does the sliding filament hypothesis require
ATP
106
name of bands in muscle fibres
striations
107
what is the band where the mysosin is found
A band
108
Explain the difference betweeen the appearance of myofibril when relaxed vs contracted
actin and myosin overlap
thin filaments move along thick actin
this pulls z lines closer
ATP needed
109
what is the area that the sarcolemma connects to the neurone
motor end plate
110
where in the muscle do Ca2+ ions accumulate
sarcoplasmic reticulum
111
what is ATP used for in the muscle cell
active transport of calcium ions into the sarcoplasmic reticulum
112
what happens when depolarisation occurs in the sarcolemma
voltage sensititive Ca ion gates in the sarcoplastic reticulum open so Ca2+ moves into the sarcoplasm via diffusion
113
how would strength of muscle contraction increase
more acetyl choline so more muscle cells contract
114
osmoregulation meaning
control of blood water potential
115
Type 1 diabetes
body is unable to produce insulin (possibly due to an autoimmune disease where beta cells are attacked)
116
Type II diabetes
receptors on target cells lose their responsiveness to insulin (due to obesity/ poor diet)
117
glomerulus function
filters small solutes from the blood
118
Proximal convoluted tubule function
reabsorbs ions, water and nutrients, removes toxins and adjusts filtrate pH
119
distal convoulted tubule function
selectively secretes and absorbs ions to maintain blood pH and electrolyte balance
120
collecting duct function
reabsorbs solutes and water from the filtrate
121
descending loop of Henle function
aquaporins allow water to pass from the filtrate into the interstitial fluid
122
Bowman's (renal) capsule function
Ultrafiltration occurs hereas the afferent arteriole is wider than the efferent arteriole
Creating high hydrostatic pressure
So small molecules are forced out of capillaries into the renal capsule creating the glomerular filtrate
123
Afferent vs efferent arteriole
Afferent- entering the glomerulus
Efferent- leaving the glomerulus
124
PCT meaning
Proximal convoluted tube
125
Process which occurs in the PCT
walls made of microvilli epithelial cells to provide a large surface area for diffusion of glucose into cells from PCT
Glucose is actively transported out of cells into intercellular space to create a concentration gradient. Glucose then diffuses back into the blood.
126
Process that occurs in the loop of henle
Na+ actively transported out of the ascending limb into the medulla to create a low water potential.
Water moves out the descending limb and out of the distal convoluted tubule and collecting duct by osmosis.
127
What happens in kidney if blood water potential is too low
more water is reabsorbed by osmosis into the blood from the tubules of the nephrons. This
means the urine is more concentrated
128
What happens if blood water potential is too high
less water is reabsorbed by osmosis
into the blood from the tubules of the nephrons
129
role of the hypothalamus in osmoregulation
Changes in water potential are detected by osmoreceptors in the hypothalamus
ADH is produced in the hypothalamus
130
describe how a glucagon works
Binds to complementary membrane- bound receptor in CSM of target cell
This activates adenyl cyclase
This causes ATP to be converted into cyclic AMP (by acting as a catalyst)
This activates protein kinase from inactive protein kinase
Protein kinase can convert glycogen into glucose and can activate other enzymes involved in converting glycerol and amino acids into glucose
131
glycogenolysis meaning
breaking up glycogen to release glucose
132
gluconeogenesis meaning
creating glucose from non-carbohydrate stores (if all glycogen has been used)
133
glycogenesis meaning
formation of glycogen from glucose
134
where is insulin secreted from
In beta cells in the Islets of Langerhan
135
where is glucagon secreted from
alpha cells in the Islets of Langerhan
136
What does insulin do
Attaches to receptors in target membranes
Stimulates liver enzymes to carry out glycogenesis
Increases glucose channel proteins in cell membrane (for fac. diff)
137
What does glucagon do
Attaches to receptors in target membrane
Stimulates liver cells to carry out gluconeogenesis
Stimulates liver enzymes to carry out glycogenolysis
138
What does adrenaline do
Attaches to receptors in target membrane
Stimulates liver enzymes to carry out glycogenolysis
139
Type 1 diabetes features
autoimmune chronic condition
Beta cells targeted
Must inject insulin and control diet
140
Type 2 diabetes
linked to obesity etc.
Overuse of beta cells
Diet and medication
141
generator potential vs action potential
generator potential is when the cell starts depolarising but action potential is when it reaches threshold
142
negative feedback meaning
there is deviation from the normal then a return to normal
143
why is the action of glucagon an example of the second messanger model
cAMP is the second messanger
144
what happens if blood water potential is too low (refer to ADH)
water leaves osmoreceptors and they shrivel
this stimulates the hypothalamus to produce more ADH
ADH moves to the posterior pituitary gland
ADH is released into capillaries and travels to the kidney
ADH makes the walls of the collecting duct and DCT more permeable to water
145
how does ADH make the DCT and collecting duct walls more permeable to water
ADH binds to receptors on the walls
this activates a phosphorylase enzyme
phosphorylase causes vesicles containing aquaporins to fuse with the CSM and create more aquaporins
so more water leaves the DCT
146
what is an aquaporin
protein channel water can pass through
147
structure and function of slow twitch muscle fibres
lots of myoglobin
lots of mitochondria
good blood supply
contract slower and can aerobically respire for a long time
found in calves etc
148
structure and function of fast twitch muscle fibres
thicker myosin fillament
large store of glycogen (for glycogenolysis) and phosphocreatine
contract faster to provide a powerful burst of muscle contraction
enables more anerobic respiration
found in biceps etc
generate less ATP per glucose molecule
149
what happens at a neuromuscular junction
action potential reaches the presynaptic reigon of a motor neuron
calcium ion channels open and calcium ions diffuse into the presynaptic neuron
vesicles containing the neurotransmitter fuse with the presynaptic membrane
the neurotransmitter diffuses across the neuromuscular junction binds to receptors on the sarcolemma
sodium ion channels in the sarcolemma open and Na+ ions move into the sarcolemma
the membrane depolarises and an action potential is created
150
explain the sliding filiament theory
the release of calcium ions is triggered by an action potential
calcium ions bind to tropomyosin which causes it to move and unblock the binding sites on actin
the myosin heads (with ADP and Pi attached) bind to the binding site on actin and form an actin-myosin cross-bridge
the myosin head bends, pulling the actin fillament along (powerstroke), releasing ADP and Pi, generating tension and causing actin to slide over myosin
a new ATP binds to the myosin head, causing it to detach from the actin
ATPase hydrolyses ATP into ADP and Pi, which releases the energy needed to reposition the myosin head to its original state
Calcium ions are actively transported back into the sarcoplasmic reticulum and tropomyosin returns to block the binding sites
151
what is tropomyosin
a protein which can block the myosin head binding sites
152
use of ATP in muscle contraction
breaks actinomyosin cross bridges
bends the myosin head to slide actin fillaments
actively transports calcium ions back into the sarcoplasmic reticulum
153
what is the role of phosphocreatine in muscle contraction
acts as a rapid ATP source by phosphorylating ADP
154
what is the role of calcium ions in muscle contraction
binds to tropomyosin to cause it to unblock the binding site
so myosinoactin crossbridges can form
155
what is the H zone
where only myosin is found
156
what is the z line
the start and end of a sarcomere
157
what is the I band
where only actin is found
