AO1 - Unit 6 Flashcards
1
Q
How do organisms increase their chance of survival?
A
respond to changes in external environment to keep them in favourable conditions to increase chance of survival
2
Q
What is a stimulus?
A
something that provokes a functional response from an organ/tissue or organism
3
Q
What detects a stimulus?
A
receptors
4
Q
What stimuli do flowering plants respond to?
A
light, gravity
5
Q
Give another word for a plant growth response
A
tropism
6
Q
Name the main auxin (plant growth regulator) involved in plant responses
A
IAA - indole acetic acid
7
Q
What is a positive phototropic response?
A
growth towards light
8
Q
What is gravitropism?
A
movement in response to gravity
9
Q
How are tropisms controlled?
A
auxins/growth hormones
10
Q
How do auxins control gravitropic responses in the shoot?
A
IAA moves to lower side of the shoot and encourages cell elongation meaning the shoot grows upwards
11
Q
How do auxins control gravitropic responses in the root?
A
IAA moves to lower side of the root and inhibits cell elongation meaning the shoot grows downwards
12
Q
Why is a logarithmic scale sometimes used when plotting a graph?
A
when there is a large range in results
13
Q
How do auxins control phototropic responses in the shoot?
A
auxins accumalate in the shaded side of a shoot, increasing elongation of these cells so shoot bends towards light
14
Q
What is a simple behavioural response in which an organism moves either towards or away from a directional stimulus?
A
taxis
15
Q
What is a simple behavioural response in which a stimulus leads to a non-directional response?
A
kinesis
16
Q
What is the purpose of a mobile organism having simple responses?
A
respond to changes in external environment to keep them in favourable conditions to increase chance of survival
17
Q
What is a reflex?
A
a rapid, automatic response to a stimulus
18
Q
What is a reflex arc?
A
pathway that controls the reflex from receptor to sensory neuron to relay neuron to motor neuron to effector
19
Q
Name the neurons present in a simple reflex arc.
A
sensory neuron to relay neuron to motor neuron
20
Q
Why are reflex arcs automatic and very rapid?
A
protect the organism from harm
21
Q
What does the central nervous system consist of?
A
brain, spinal cord
22
Q
Give 2 examples of effectors.
A
muscles and glands
23
Q
Name a mechanoreceptor found deep in mammalian skin
A
pacinian corpuscle
24
Q
Describe this mechanoreceptor
A
Pacinian corpuscles contain the end of a sensory neuron. This sensory neuron ending is wrapped in loads of layers of connective tissue called lamellae which deform under pressure and stimulate the sensory neuron
25
What happens when the mechanoreceptor is stimulated?
Lamellae deform. This causes the sensory neuron?s cell membrane to stretch, deforming the stretch mediated sodium channels. The channels open which allows sodium ions to diffuse into the neuron
26
Where are the light sensitive receptor cells found in humans?
eyes
27
Name 2 types of photoreceptor cells found in human eyes?
rods and cones
28
Through what is information about incoming light relayed to the brain?
optic nerve
29
What is the back of the eye called which contains photoreceptors?
retina
30
What is visual acuity?
ability to tell separate points apart
31
Which light receptors function best at low levels of light?
rods
32
Which light receptors have best visual acuity?
cones
33
Explain what is meant by retinal convergence.
many rods synapse to one bipolar neuron
34
What is rhodopsin?
pigment which breaks down when exposed to light in rod cells
35
Which light sensitive cell has low visual acuity, but high sensitivity?
rods
36
What is iodopsin?
pigment which breaks down when exposed to light in cone cells
37
Where is the greatest concentration of cones?
fovea
38
Which light sensitive cells are responsible for colour vision?
cone cells
39
How is the heart/cardiac muscle described?
myogenic
40
What initiates the heart beat?
SAN
41
Describe the path of the electrical impulses involved in co-ordinating a heart beat
SAN to AVN to bundle of His/purkyne fibres
42
Where does the cardiovascular system receive information from?
cardioregulatory centre in the medulla
43
Where are the baroreceptors?
aorta and carotid artery
44
When do the baroreceptors send impulses to the cardiovascular centre?
when blood pressure is too high or too low
45
Where are chemoreceptors?
aorta and carotid artery
46
What gas do chemoreceptors respond to? Why?
carbon dioxide - high concentrations reduce the pH of the blood and can denature enzymes
47
Give an example of when the chemoreceptors would send more impulses to the cardiovascular system
when high carbon dioxide concentrations are detected
48
What does antagonistic mean?
working in opposition to each other
49
What neurons can be described as antagonistic in relation to control of heart rate?
sympathetic and parasympathetic neurons
50
How does the cardiovascular centre communicate with the SAN to modify heart rate?
via the sympathetic and parasympathetic neurons
51
What does the autonomic nervous system comprise of?
The ANS is divided into 2 :
the sympathetic nervous system (SNS) . At the nerve endings, a chemical called noradrenaline is secreted and this generally speeds up activities
the parasympathetic nervous system (PNS). At the nerve endings, acetycholine is secreted which generally slows down any activity
52
Increased impulses travelling down the sympathetic nerve to the SAN would cause what to happen?
increase heart rate
53
What would happen if both the sympathetic and parasympathetic nerve to the SAN were cut?
heart would still contract as it is myogenic but would not change rate in respond to stimuli to speed up or slow down
54
What is the difference between a nerve and a neuron?
neurons are single cell components and nerves are bundles of neurons plus other tissue
55
What is a synapse?
junction between two neurons
56
What is the axon?
long, tube-like extension of a neuron
57
How could you describe "resting potential" of a neuron?
the outside of the axon membrane is positively charged compared to the inside. This is because there are more positive ions on the outside than there are on the inside
58
Which two processes are involved in establishing the resting potential of a neuron?
sodium/potassium pump removes 3NA+ for every 2K+ and the membrane is more permeable to potassium diffusing out of the axon than sodium diffusing in
59
What does the sodium- potassium pump do?
pumps 3NA+ out for every 2K+ in, active process
60
Suggest a typical value for resting potential.
negative 65mV
61
What happens when the nerve is stimulated?
When a stimulus is detected, the cell surface membrane of a receptor becomes ?excited? causing sodium ion channels to open so sodium ions diffuse into the neurone down an electrochemical gradient.
The change in potential difference is called the generator potential
62
Name the 2 stages of an action potential.
depolarisation and repolarisation
63
Describe the events of depolarisation.
the potential difference across the axon membrane reaches the threshold (around -55mV), voltage-gated sodium ion channels open. More sodium ions diffuse into the neurone and depolarise the axon membrane, setting up an action potential at that point.
64
What is positive feedback? Give an example
a change causes a response which amplifies that change. EG - oxytocin stimulates contractions which stimulate more oxytocin release
65
Describe the events of repolarisation.
Once an action potential of around +30mV to +40mV has been reached, the voltage-gated sodium ion channels close and voltage-gated potassium ion channels open. Potassium ions then diffuse out, resulting in repolarisation of the membrane
66
What is the refractory period?
The minimum interval between action potentials is called the refractory period
67
What are the 2 phases of the refractory period? What is the difference between them?
Absolute refractory period during which it is impossible to generate another action potential, Na+ voltage-gated channels are inactivated.
Relative refractory period, Voltage gated sodium ion channels are closed but it is possible for them to open and to generate another action potential but only if the stimulus is of greater intensity than normal.
68
Why is the refractory period important?
Each action potential is kept discrete (separate)- there is no overlapping of action potentials.
It ensures the action potentials pass in one direction only
69
Do Action Potentials vary in size?
no, only in frequency
70
Give 4 factors that affect speed of transmission of AP along axons
myelinated vs non-myelinated, temperature, diameter of axon, number of synapses
71
What is saltatory conduction?
describes the way an electrical impulse skips from node to node (nodes of ranvier) down the full length of a myelinated axon
72
What type of substance is myelin?
lipid
73
What produces the myelin sheath?
schwaan cells
74
What happens initially when an AP arrives at the synaptic knob?
tirggers the opening of voltage gated calcium channels and calcium diffuses into presynaptic knob
75
What do the vesicles in the presynaptic neuron contain?
neurotransmitters
76
What happens to the vesicles during synaptic transmission?
move towards the pre-synaptic membrane, fuse and release contents via exocytosis
77
What is found on the membrane of the post synaptic neuron
receptors
78
How does the neurotransmitter cross the synaptic cleft?
diffusion
79
Once the NT is bound to the post synaptic membrane, sodium ions flow inwards building up a charge known as ________________
depolarisation
80
What happens to the transmitter substance after an AP has been generated?
broken down by enzymes and the products reabsorbed by the pre-synaptic knob
81
Why are mitochondria found in the synaptic knob?
release energy/produce ATP for movement of vesicles and to resynthesise acetycholine
82
Why is transmission across a synapse unidirectional?
vesicles with high concentrations of NTs only in pre-synaptic knob and recptors only on post-synaptic knob
83
Name a widespread neurotransmitter used at neuromuscular junctions
acetylecholine
84
Which neurotransmitter is used by the sympathetic nervous system?
noradrenaline
85
Name 2 neurotransmitters used in the brain?
dopamine, acetylecholine, serotonin
86
How do many drugs and toxins work?
they affect synapses
87
What are inhibitory neurotransmitters?
An inhibitory neurotransmitter will open chloride and potassium ion channels allowing chloride ions to flow into the cell and potassium ions to flow out. This causes hyperpolarisation (the inside becomes even more negative) of the post synaptic membrane, preventing it from firing an action potential.
88
What are the two types of summation?
spatial and temporal
89
What is muscle tissue able to do?
contract
90
Muscles work in pairs known as ?
antagonistic pairs
91
How are muscles attached to bone?
tendon
92
What is the function of skeletal muscle?
contract to pull on tendons to pull on bones of the skeleton
93
What is the basic unit of of skeletal muscle?
muscle fibres
94
what is the modified cell membrane around each muscle fibre called?
sarcolemma
95
Name the 2 main proteins involved in muscle contraction.
actin and myosin
96
Which protein wraps around actin fibres blocking binding sites?
tropomyosin
97
What brings about the change that enables actin-myosin bridges to form?
calcium ions released bind to troponin and move the tropomyosin molecule away from the binding site
98
What is the role of ATP in muscle contraction?
Hydrolysis of ATP (on myosin heads) causes myosin heads to bend/ become cocked; Removal of ADP changes the shape of the myosin head (Bending) pulling actin molecules across the myosin / power stroke; Attachment of a new ATP molecule to each myosin head causes cross bridges to break / myosin heads to detach (from actin sites).
99
How is ATP resynthesised after 3 seconds of intense exercise?
Muscle fibres also contain stores of phosphocreatine. This can be used to produce ATP rapidly by transferring a phosphate ion (Pi) to ADP and thus replacing the ATP that has been (broken down)hydrolysed
100
Name the 2 types of muscle fibre.
fast and slow twitch
101
Compare the 2 types.
comment on amount of myoglobin, mitochondria, density of cappilary network, calcium ion storage
102
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment within restricted limits using physiological control systems
103
Why is it important that body temperature remains within narrow limits?
Temperature and pH affect enzyme activity and enzymes control the metabolic reactions
104
Why is it important that blood pH remains within narrow limits?
Temperature and pH affect enzyme activity and enzymes control the metabolic reactions
105
Why is it important that blood glucose concentration is maintained?
It is important that there is always some glucose circulating in the blood because cells need a constant supply for respiration. However, if the concentration of glucose rises too high it has a major effect on the water potential of the blood.
106
What is negative feedback?
a change away from the optimum results in an opposing change back towards the optimum
107
Define glycogenesis.
the formation of glycogen
108
Define glycogenolysis
the breakdown/hydrolysis of glycogen
109
Define gluconeogenesis
the formation of glycogen from substances other than sugars
110
What is hyperglycaemia?
level of glucose in the blood is too high
111
Which organ monitors blood glucose levels?
pancreas
112
What are the 2 hormones involved in the control of blood glucose.
insulin and glucagon
113
Where are these 2 hormones produced?
alpha cells of islets of langerhans produce glucagon/ beta cells produce insulin
114
Name 3 types of tissue that contain an abundance of insulin receptors
muscle, liver, adipose tissue (fat)
115
By what mechanism is blood glucose lowered..........?
More glucose enters cells by facillitated diffusion. Cells increase their rate of respiration, Glycogenesis can be stimulated to convert glucose to glycogen to be stored in the cytoplasm
116
Insulin also causes glucose to be converted into what?
glycogen
117
Which hormone is secreted when blood glucose levels fall?
glucagon
118
When glucagon attaches to receptors it sets in motion a cascade of reactions. What is the first one?
Adenylate cyclase converts ATP into cyclic AMP( cAMP), which is know as the second messenger ( meaning that it carries the message of the hormone inside the cell).
119
What is the second messenger?
cAMP
120
How is the blood glucose returned to normal levels?
Protein kinase A activates a cascade ( a chain of reactions) that breaks down glycogen into glucose ( glycogenolysis)
121
What are protein kinases?
enzymes which activate a cascade resulting in glycogenolysis
122
Name one other hormone that can increase blood glucose
adrenaline
123
How does this hormone increase blood glucose?
similar to glucagon - stimulates glycogenolysis
124
What is type 1 diabetes?
the immune system attacks the ? cells in the Islets of Langerhans so they cannot produce insulin.
125
Name 5 symptoms of type 1 diabetes
feeling very thirsty.
peeing more than usual, particularly at night.
feeling very tired.
losing weight without trying.
thrush that keeps coming back.
blurred vision.
126
What is type 2 diabetes also known as?
type 2 diabetes mellitus and adult-onset diabetes.
127
Name a risk factor for type 2 diabetes?
obesity
128
What does treatment for type 2 diabetes include?
control of diet, reduced intake of carbohydrates, exercise, weight loss
129
What is the cause of type 2 diabetes?
the body may not produce enough insulin or the cells fail to respond to insulin. Receptors for glucose may be abnormal; fewer glucose transport proteins may be added to cell surface membranes SO less glucose enters cell and less glycogenesis.
130
How could you determine the glucose concentration of a urine sample?
calibration curve using known concentrations of glucose
131
What is osmoregulation?
maintainance of a constant blood plasma concentration/water potential
132
Name the key organ in control of water potential.
kidneys
133
name the 2 main processes that occur in kidney nephrons
ultrafiltration and selective reabsorption
134
What is the functional unit of the kidney?
nephron
135
How is the glomerular filtrate produced?
ultrafiltration between the glomerulus and the bowman's capsule
136
What are fenestrations? Where are they found?
small gaps in endothelium of capillaries
137
What are podocytes?
cells lining the tubule at the bowman's capsule
138
Where is the basement membrane?
bowman's capsule
139
The filtrate has the same composition as what other fluid?
tissue fluid
140
What is the next thing to happen to the filtrate after ultrafiltration?
selective reabsorption
141
What is the main region of reabsorption?
proximal convoluted tubule
142
By what processes is most of the reabsorption brought about?
facilitated diffusion and active transport
143
Name 3 substances that are reabsorbed?
glucose, amino acids, ions
144
What does the Loop of Henle consist of?
thin descending limb and a thicker ascending limb
145
What is the vasa recta?
blood vessels that supply the kidneys
146
What are aquaporins?
protein channels that allow the passage of water across a membrane
147
What happens as the filtrate passes down the descending limb of the loop of Henle?
water leaves via osmosis to the medulla interstitual fluid
148
What happens as the filtrate travels up the ascending limb?
na+ and cl- ions leave the tubule via active transport
149
What prevents water moving out by osmosis in the ascending limb?
it is impermeable to water
150
What does the loop of Henle create?
concentrated filtrate and an increasing concentration of the medulla tissue fluid
151
What is the permeability of the distal convoluted tubule under the influence of?
ADH
152
Where are osmoreceptor cells?
cells which monitor the water potential of the blood in the hypothalamus
153
If water loss exceeds water intake what happens to blood water potential?
decreases
154
What is stimulated if this happens?
When the water potential of the blood plasma decreases, water will move out of the osmoreceptor cells by osmosis. This causes the cells to decrease in volume. This sends a signal (nerve impulse) to other cells in the hypothalamus which send a signal (nerve impulses) to the posterior pituitary gland. This causes the posterior pituitary to release a hormone called antidiuretic hormone (ADH). The hormone travels around the body in the blood plasma
155
What is the target organ of ADH?
kidneys
156
What is the effect of ADH?
ADH molecules bind to specific protein receptors on the plasma membranes of cells in the DCT and the collecting duct. This causes protein channels called aquaporins to be inserted into the plasma membrane. These channels allow water to pass through by diffusion. This means that more water is reabsorbed from these tubules into the medulla and then into the blood by osmosis
