6- Nervous Sytem And Homeostasis Flashcards
1
Q
Why do we need a nervous repsone
A
Selection pressure favours orgaisms with the more appropriate response
2
Q
What is a stimulus
A
A detectable chmage In the internal or external environment
3
Q
What is the response
A
What an organism can do to react to the stimuli
4
Q
What are cells sensitive to stimulus called
A
Receptors
5
Q
T or f
Receptors are specific to stimuli they recieve
A
T
6
Q
response produced by an effector can be at what 2 levels
A
At a molecular level ( hormones)
Behaviour of Whole organism
7
Q
What is taxis
A
The moment of an animal towards or away form a stimulus in one direction
Eg, chemotaxis
8
Q
What is kinesis
A
Orienting behaviour where an animal reduced or increases it rate of movement as the intensity of a stimuli increases
9
Q
What is an example of kinesis
A
Woodlois start to move when they start to dry out
10
Q
What is Tropism
A
The growth movement of part of a plant in response to a directional stimuli
11
Q
What is the reflex escape response
A
Rapid automatic response to escape predators
12
Q
Why do plants respond to external stimuli
A
Avoid stress
Avoid being eaten
Enhance survival
Improve chances of successful breeding
13
Q
What is phototropism response to
A
Light
14
Q
What is geotropism response to
A
Gravity
15
Q
What is chemotropism response to
A
Chemicals
16
Q
What is thigmotropism response to
A
Touch
17
Q
What controls the response of plants
A
hormones control / coordinate plant response
18
Q
What are the chemicals in plants still considered hormones eventhough they are not produced by the endocrine system
A
They are transported away from site of manufacture to a target cell
19
Q
Do hormones allways move from site of manufacture to target cell
A
No some hormones stay in the cell that makes them and exerts their effects within the cell
20
Q
Descirbe hormones in plants
A
Produced by a specific cell
Have a specific shape
Bind to reseptors on the target cell
Receptor complementary to the shape of the hormone
21
Q
How are hormones carried around the plant
A
Diffusion
Active transport
Mass flow ( phloem / xylem)
22
Q
What is it called when hormones amplify each other
A
Synergy
23
Q
What is it called when hormones cancel each other out
A
Antagonistic
24
Q
Where does growth in a plant occur
A
Meristem
25
What are the 3 areas of the meristem ( and be able to label)
Apical meristems
Lateral bud meristems
Intercallary meristem
26
What causes phototropism
All shoots bend towards the light
As the shaded side elongates faster as light causes auxins to be transported to shaded side which promotes growth
27
What causes gravptropism
Auxin increases in side next to the stimulus and inhibits growth. So upper roots grow quicker and bend roots ( down ) towards stimuli
28
What does IAA stand for
Indolaceticacid
29
What is the commercial use of auxins
Promotes cell gworth so used in cuttings
Seedless fruits
Herbicides
30
What is the commercial use of gibberellins
Seed germination and grows the stems
Delays senescence ( aging )
Imporves shapes
31
What is the commercial use of cytokinins
Promotes cell division
Prevents yellowing
Mass production
32
What is the commercial use of ethene
Promotes fruit ripening
Promotes fruit drop
Female sex expression in cucumbers
Promotes lateral growth
33
What is the acid growth hyposthesis
The action of IAAs increases the plasticity of cell walls in young cells (mature cells are more rigid)
Active transport of H+ ions form cytoplasm to spaces in the cell wall causing cell to become more plastic and elongated by expansion
34
Describe the plant repsonse experiment carried out by Charles Darwin;
He observed young grass shoots growing towards the light
He proposed stimuli of the light was detected by the tip of the shoot
He cut of the tip in one
One with a tip bent towards the light , one with no tip had no response
35
Desicbe the Peter boysen-jenson experiment
He tried to prove weather chemical substances produced in the top and transported down the stem and cause a repsonse or an electrical signal
He put a thin impermeable barrier of mica on light side# movement of chemical down shaded side caused stem to bend toward slight
The put the mica on the shaded side - the chemical was blocked by the mica so no response
Then he put a block of gelatin across whole stem- an electrical signal would be blocked by a chemical can still move , the stem bent towards the light so chemicalnot electrical
36
Desicbe paal plant response experiments
He investigated how chemical messagers worked - he removed tops of shoots and put them in darkness
The tips bent towards side where no tips where present
37
Describe the Winslow brings plant response experiment
How Light caused uneven distribution of IAA
1- two tips , one had light and bent - the total IAA is each was approx the same
2- then 1 tip with a thin glass plate separating the side of the shoot
Amount of iaa collected is apr. The same
3- half glass plate
Bent - 30% collected in light side amd 70% on shaded elongated side
38
Why do animals respond to changes in their internal environment.
To make cure that the conditions are always optimal for their metabolism
39
What is any change in the interbank or external environment called
A stimulus
40
What detects stimuli
Receptors
41
What can receptors be
Cells or proteins on cell surface membranes
42
What are effectors
Cells that bring about a response to a stimulus, to produce an effect
43
What do effectors include
Muscle cells and cells found in glands
44
How do receptors communicated with effectors
Via the nervous system or the hormonal system or sometimes using both
45
What is the nervous sustem made. Up of
Neurones
46
What are the 3 main neuron types
Sensory neurones
Motor neurones
Relay neurones
47
What do sensory neuron’s do
Transmit electrical impulses form receptors to the central nervous system - the brain and spinal cord
48
What is included in the CNS
Brain and spinal cord
49
What do motor neurons do
Transmit electrical impulses form the cns to effectors
50
What do relay neurons do
Transmit electrical Impulses between sensory neurons and motor neurons
51
What are electrical impulses also called
Nerve impulses
Or
Action potentials
52
Desicbe what happens when a stimulus is detected to an effect or
1- stimulus detected by receptor cells and an electrical impulse is sent along a sensory neurone
2- when an electrical impulse reached the end of a neurone, chemicals called neurotransmitters take information across to the next neuron which then sends an electrical impulse
3- the cns ( the coordinator) processes the information and sends impulses along motor neurons to an effect or
53
What chemicals take information from one neurone to the next
Neurotransmitters
54
What is the peripheral nervous system made up of
Neurons that connect the cns to the rest of the body. It also has 2 differnt systems
55
What 2 ways is the nervous system split
Central nervous system
Peripheral nervous sustem
56
What 2 systems are a part of the peripheral nervous system
Somatic
Autonomaic
57
What does the somatic nervous system control
Conscious activates
Eg, running
58
What does the autonomic nervous system control
Unconscious activities
Eg. Digestion
59
What 2 systems does the autonomic nervous system and what effect do they have on each other
Opposite effect on each other
The sympathetic nervous system
The parasympathetic nervous system
60
What does the sympathetic nervous system condo
Gets the body read for action
It’s the flight or fight system
61
What does the parasympathetic nervous system do
Calms the body down
It’s the rest and digest
62
What are reflexes
Rapid
Automatic responses to stimuli
A reflex is where the body response to a stimuluswithout making a conscious decision to repsond
63
Why does information travel real fast from receptor to effector when it’s a reflex
Don’t spend time deciding how to repsond
64
Why do simple reflexes help organisms to protect the body
They’re rapid
65
What is the pathway of neurones linking receptors to effectors in a reflex is called what
Reflex arc
66
Describe the reflex arc with the example of a had withdrawal response to heat
Thermoreceptors In the skim detector the heat stimulus
The sensory neurons carries impulses to the relay neurone
The relay neuron connects to the motor neurone
The motor neurone sends impulses to the effector
Your muscle contracts to withdraw your ban and stop it being damaged
67
If there is a ….. neurone Involved in the simple reflex arc then it’s possible to override the reflex
. How does this link to hand withdrawn in response to heat
Relay
In the example above your brain could tell your hand to withstand the heat
68
Nervous system communication is
…..
…..
……
Localised
Short lived
Rapid
69
Why is nervous system communication localised
When an electrical impulse reaches the end of a neuron, neurotransmitters are secreted directly onto target cells
70
How is nervous system communication short lived
Neurotransmitters are quickly removed once they’ve done their job
71
3 ways , plants increase their chance of survivals by responding to changes in environment
1- grow towards lifht to maximise light absorbtion for photosynthesis
2- sense gravity Si roots and shoot grow in right direction
3climbing plants sense touchy so can find things to climb up and reach the sunlight
72
What is a positive tropism
The growth is towards the stimulus
73
What is negative tropism
The growth is away for the stimulus
74
Are shoots positively phototrophic or negative
Positively - they grow towards the light
75
Are roots postivitley phototophic or negatively
Negatively- thus grow away from light
76
Are shoot positively or negatively gravitrioic
Negative - they grow upwards
77
Are roots positively gravitrioic or negative
Positive they grow downwards
78
What do3s auxin do
Stimulate growth of shoot by cell elongation , the cell walls become loose and stretchy so the cell become longer
79
What does high conc of auxin in the roots do
Inhibit growth
80
What are IAAs
An important auxin that’s produced in the tips and shoots in flowering plants
81
What does IAA do
Moved around the plant to control tropisms
82
How does IAA move around the plant
And what does this result in
Moves by diffusion and active transport over shot distances and via the phloem for long distances
Results in differnt parts of the plant having differnt concentrations of IAA. An uneven distribution of IAA means there’s uneven growth of the plant
83
Describe p how you can use choice chambers to investigate animal response
1( light intensity
- cover one half with black paper , place 10 wood louche in the centre and cover , after 10 mins count number of woodlouse on each side repeate (they should end up on dark side - as it keeps them concealed under stones during the day so away form predators)
2) humidity
- damp filter paper on one side and a drying agent on the other. Lid on, wait 10 mins
(The damp conditions are more favourable as it reduces water loss)
84
How do woodlice show a kinetic response to humidity
In high humidity they move slowly and turn less oftern
So that they stay where they are
As the air gets drier they move faster and turn more oftern so they move into a new area - this response increwsss rhe chance the woodlouse will move unit an area with higher humidity - reduces water loss in high humidity
85
Describe nervous communication
Electrical impulses
Target cells stimulated by neurotransmitters
Rapid ( transmission + response)
Short lived response
Localised
Specifically trageted
Temporary
86
Describe hormones
Chemicals from endocrine glands, blood plasma to target cells
Target cells have receptors on CSM, change in conc. stimulate them
Slower, less specific, long lasting and widespread.
Hormones travel throughout body but only granger cells response
(Effect permanent and can be irreversible)
Transmission amd response is slow
87
What 2 ways can you Desicbe the nervous system
Central nervous sustem
Peripheral nervous system
88
What’s included in the CNS
Brain and spinal chord
89
What 2 ways is the peripheral nervous system divided
Sensory receptors —> CNS
Motor CNS —-> effector
90
What 2 ways is the motor nervous system divided
Voluntary NS
Automatic NS
91
What sit he voluntary NS
Carries nerve impulses to body muscles, voluntary control
92
What is automatic NS
Nerve impulses carried to glands, smooth muscles and cardiac muscle and is not under voluntary control - its involuntary (unconscious)
93
Describe the reflex arc
Stimulus
Receptor
Sensory neuron
Coordinator
Motor neuron
Effector
Repsonse
94
What are the 3 neurons and where do they go
Sensory neurons ( receptors to CNS)
Interneurons ( to motor neuron )
Motor neuron ( to effectors)
95
Key features of a reflex arc
Automatic
Innate
Cannot be learned
Don’t involve the brain
Immediate
Fast ( short neuron pathway as only 1 or 2 synapses)
96
Learn the structure of the myelinated never cell
97
How can you tell the difference between the motor /intermediate and sensory
Motor and intermediate - the cell body is at the end of
Sensory the cell boys is in the middle
98
T or f
Receptors only detect one particular stimulus
T
99
What are some receptor types
Cells (eg, photoreceptors)
Proteins on cell surface memebrane (eg, glucose receptor)
100
When a nervous system receptor is in its resting state, what is there
A differnce in charge between the inside and outside of the cell
101
How is the difference in charge between inside and outside of cells generated , in the resting state of the nervous system
Generated by ion pumps and ion channels
102
What is there across the membrane of a nervous system receptor
Voltage known as potential difference
103
What is the potential differnce when a cell is as rest called
Resting potential
104
What happens to potential differnce In receptors when a stimulus is detected
The cell memebrane is excited and becomes more permeable , allowing more ions to move in and out of cell. Altering the potential differnce
105
What is the change in potential differnce due to a stimulus called
Generator potential
106
How does a bigger stimulus effect generator potential
Excited the membrane causing a bigger movement of ions and a bigger change in potential differnce
So a bigger generator potential is produced
107
If the generator potential is big enough what is triggered
Action potential
108
What is action potential
An electrical impulse along a neuron
109
When is an action potential only triggered
If the generator potential reaches a certain level called threshold level
110
T or f
Action potentials are all one size
T
111
The strength of the stimulus is measured by what
The frequency of action potential
112
How is frequency of action potential measured
The number of action potential triggered during a certain time period
113
Will there be a action potential if the stimulus is too weak
The generator potential won’t reach the threshold
So no action potential
114
What are pacinian corpuscles
Mechanoreceptors
115
What do mechanoreceptors detect
Mechanical stimuli
(Eg. Pressure and vibration )
116
Where are mechanoreceptors found
In the skin
117
What do pacinian corpuscles contain
End of a sensory neuron ( called sensory Nerve ending )
The sensory nerve ending is wrapped in loads of layers of connective tissue called lamellae
118
What happens when a pacinian corpuscle is stimulated
Eg. Tap on the arm
The lamellae are deformed and press on the sensory Neve ending
This causes the sensory neurons cell memebrane to stretch, deforming the stretch-mediated sodium ion channels
The channels open and sodium ions diffuse into the cell , creating a generator potential
If the generator potential reaches the threshold it triggers an action potential
119
How does light enter the eye
Pupil
120
The amount of light that enters is controlled by what
The muscles of the iris
121
How are light rays focused in the eye
Focused by the lens onto the retina, which lines the inside of the eye
122
What does the retina contain
Photoreceptors cells
123
What is the fovea
An area of the retina where there are lots of photoreceptors
124
How does nerve impulses form the photoreceptor cells work ( eye)
Carried form the retina to the brain by the optic Nerve ( which is a bundle of neurons )
125
Where the optic nerve leaves the eye it’s called what
The blind spot
126
Why is where the optic nerve leaves rhe eye called a blind spot
There arnt any photoreceptor cells , so it’s not sensitive to light
127
How does photoreceptors convert light into an electrical impulse
1) light enters the eye, hits the photoreceptors and it’s absorbed by light sensitive optical pigments
2) light bleaches the pigments, causing a chemical change and altering the membrane permeability to sodium ions,
3) a generator potential is created and if it reaches the threshold, a neve impulse is sent along a bipolar neurons
4) bipolar neuorne connect photoreceptors to the optic Nerve which takes impulses to the brain
128
What are the 2 types of photoreceptors in the human eye
Rods and cones
129
Where are rods mainly found
Peripheral part of the retina
130
Where are cones found
Packed together in the fovea
131
What differs between rods and cones
They contain differnet optical pigments making ghem sensitive to differnt wavelengths.
Rods only give information in black and white(monochromatic vision) but cones give information in colour (trichromatic vision)
132
What are the 3 types of cones
Each contain different optical pigment
Red sensitive
Green sensitive
Blue sensitivity
( they’re stimulated in differnt proportions you see differnt colours)
133
What is rods sensitivity light
They’re very sentimental to Light ( they fire action potentials in dim light)
This is because many rods join one neuron, so many weak generator potentials combine to reach the threshold and trigger action potentials
134
How sensitive are cones to light
Less sensitive than rods
(They only fire action potentials in bright light )
This is because one cone joined one neurons, so it takes more light to reach the threshold and trigger an action potential
135
What is rods visual acuity
Low visual acuity because many rods join same neuron, which means light form two points close together can’t be told apart
136
What is cones visual acuity
High
As cones are close togetehr and one cones joined one neuron
When light form two points hits two cones, two action potentials go to the brain
So you can distinguish two points that are close together as two separate points
137
What the stimulus for a mechanoreceptor
Physical
138
Be able to label pacinian corpuscle
139
Why is pacinian corpuscle a primary receptor
It’s Stimulated directly
140
What do pacinian corpuscles respond to changes in
Mechanical pressure
141
What happens when a pacinian corpuscle is pressed
When pressed, the change in pressure on
the membranes passes to the core and
causes increased permeabiltiy to sodium
ions Na+ causing depolarisation leading to
a generator potential. If this exceeds
the threshold then a nerve impulse is
generated.
142
T or f
Slow pressure changes or prolonged pressure does not cause a response
T
143
t or f
Pacinian corpuscle is a transducer
T
144
What is a transducer
Converts one from or energy into another
145
What do pacinian corpuscles convert what energy to what energy
kinetic to electrical
146
How do stretch mediated sodium channel proteins work
When pressure is applied the membrane
around the neurone becomes stretched.
This stretching widens the sodium channels
and sodium ions diffuse into the neurone.
• The influx of the sodium ions changes the
potential of the membrane ( it has become
depolarised) thus making a generator
potential.
• The generator potential therefore starts an
action potential-nerve impulse.
147
Where are the receptors in the eye found
The inner layer of the retina
148
What are the 2 types of receptors in the eye
Rods
Cones
149
How does receptors in the eye act as a transducer
Converts light energy to electrical. Energy
150
Check labelling of fovea, optic nerve, retina of eye
151
Where are the nerve imupuses sent along optic never to
The brain
152
What photosensitive chemical do rods contain and where
Rhodopsin in the outer segment
153
What type of photosensitive chemical do cones contain and where
Iodopsin in outer segment
154
What must light pass through to reach rods and cones
Other structures
Eg. Bipolar cells, blood vessels
155
Rhodopsin and iodopsin pigment get …… by light.
Is it reverisble
Bleaches
Yes
156
After bleaching rhodopsin regenerates fast ro slow
Slowly
157
After bleaching iodopsin regenerates fast ro slow
Fast
158
What happens when rhodopsin or iodopsin is stimulated
Changes shape and a transmitter substance is released to bipolar cells
159
How many and where are rods in the retina
120 million in all parts except the fovea
160
What are rods used for
Night vision
161
What do rods repsond to
Low light elevens and are used to see in dim light
162
What does light cause rhodopsin to do
Change shape
Splits into opsin and retinal
Transmitter is sent to bipolar cells
Bipolar cells are neurons wich transmit impulse to next cell layer
163
T or f
Rod cells produce transmitter when not stimulate and stop producing when stimulated
T
164
How many rods connect to each bipolar cell
So is it Moore likely to be activated by bright light or dim light
Several
Dim
165
Rhodopsin is very stable in ……..
In …….. it breaks down quickly
The dark
Strong light
166
How many cones are in the retina and where
5-6 million
All parts of retina especially in fovea
167
Why does the fovea have high visual acuity
In fovea the Sa is more thinner
Cone cells are very small
So this area has high visual acuity
168
What 2 things can the fovea area be described as being
High visual acuity
Better resolution
169
What are cones used for
Colour vision in high intensity light
170
What is the pigment in cones only broken down by
High light intensity
171
What is colourblindness due to
Lack of comes responding to some wavelengths
172
They heart is myogenic
What does this mean
When removed form the body it continues to beat
173
What does the heart need to be
Regulated and controlled
174
What is the SA under control of
The brain
( the sympathetic and parasympathetic)
175
What is heartbeat regulated by
Specialised muscle cells called pacemakers and a tract of conducting purkyne fibres
176
What does the pacemaker do
Initiates the cardiac cycle by spontaneously generating action potentials in the atria, spreading to the ventricles and stetting a basic heart rhythm
177
What are the basic rhythms in the heart regulated according to
Demand
178
What 2 things are heartbeats controlled by
Hormones and nerves
179
What 2 hormones control the heat beat
And how do they act in relation to each other
Adrenaline
Noradrenaline
Act antagonistically
180
What 2 nerve systems control the heart beat
And how do they act in relation to each other
Parasympathetic
Sympathetic
Act antagnotically
181
Sympathetic stimulation via the cardiac muscle
Is it the predominant influence
Yes
182
What does the parasympathetic nervous systems do for heart beat
Inhibits effectors
Controls actions under resting conditions
Slows down activity
Conserves energy
183
What does the sympathetic nervous system do
Stimulates effectors
Controls conditions under stress of activity
Speeds us up ( fight / flight)
184
What is the area of the brain that controls heart rate
Medulla oblongata
185
What are the 2 parts of the medulla oblongata in heart beat
1, centre linked to sinoatrial node that inc heart rate via the sympathetic NS
2. A centre linked to the sinoatrual that dec, heart rate via the parasympathetic NS (Vegus nerve)
186
What 4 things effect cardiovascular centre in medulla
And what does this effect
1. Pressure receptors I’m aortic and carotid bodies
2. Chemoreceptors in aortic and carotid bodes
3. Temperature receptors in muscles
4. Stretch receptors in muscles
Effects parasympathetic and sympathetic to bring about an effect
187
How do receptors respond to pressure changes in the blood ( heart rate)
Pressure receptors in wall of aorta and acrid artery send messages via sympathetic nervous system if blood pressure is slow and through PSNS when high
188
How do receptors repsond yo chemical chmages in the blood ( heart. Rate)
Low O2 means increased co2 and reduced PH. Detected by chemoreceptors in wall of aorta and carotid artery, heart rate increase via SNS. Removal of CO2 increasesPHand heart rate reduced via PSNS
189
The heart can contract and relax without receiving signals form nerves.
So what is the heart called
Myogenic
190
How is the regular heartbeat contorted
1) Sino atrial mode (SAN)
2) SAN sends out regular waves of regular activity to the atrial walls
3) so right and left atria to contract at the same time
4) waves of electrical activity are transferred form the SAN to the atrioventricular node ( AVN)
5) AVN is responsible for passing the waves of electrical activity on to the bundle of his (there is a slight delay before AVN reacts )
6) the bundle of his conducts waves of electrical activity between the ventricles to the apex of the heart . The bundle splits into finer muscle fibres In the right and left ventricles called purkyne tissue
7) these carry waves of electrical activity into keuclat walls of R and L ventricles, causing them to contract simultaneously from bottom up
191
Where is the San
Wall of the right atrium
192
What does the SAN do
Like a pacemaker
Sets the rhythm of the heartbeat by sending regular waves of electrical activity to atrial walls
193
What prevents the waves of electrical activity form being passed directly from the atria to the ventricles
A band of non conducting collagen tissue
194
What is the AVN responsible for
Passing the waves of electrical, activity on to the bundle of his
195
Why is there a slight delay after the AVN
To make sure the atria have emptied before the ventricles contact
196
What is the rate at which the SAN fires controlled by
Unconsciously controlled by the medulla oblongata in the brain
197
Why do animals need to alter their heart rate
Respond to internal stimuli
198
What are stimuli that effect heart rate detected by
Reassure receptors and chemical receptors
199
What are pressure receptors for heart rate called. And what are they stimulated by
Pressure receptors ( called baroreceptors) in the aorta and the carotid artieries. Stimulated by high and low blood pressure
200
What are chemical receptors for heart rate called. And what are they stimulated by
Chemcial receptors called chemoreceptors in the aorta, the carotid artaeries and In the medulla.
They monitor the oxygen level in the blood and also carbon dioxide and ph
201
Electrical impulse from receptors are sent to the mudulla along the …….. neurons
Sensory
202
What system does medulla send info to SAN along
Sympathetic or parasympathetic
203
What NS are sympathetic or parasympathetic part of
autonomic
204
How does the heart repsond ot high blood pressure
Receptor - Baroreceptors detect Hugh blood pressure
Impulses are sent to the medulla, which sends impulses along the parasympathetic neurons. There secrete acetylcholine ( a neurotrwmitter) which binds to the receptors of the SAN
Heart rate slows down to reduce blood pressure back to normal
205
How does the heart repsond to low blood pressure
receptors - baroreceptors detect low blood pressure
Impulses are sent to the medulla, which sends impulses along the sympathic neurons. These secrete noradrenaline ( a neurotranimtter( which binds to receptors of the SAN)
Herat rate speeds up to increases blood pressure back to normal
206
How does the heart repsond ot high blood O2, low CO2, high PH
Chemoreceptors detected chemical changes in the blood
Impulses are sent to the medulla, which sends impulses along parasympathetic neurons
These secrete acetylcholine which binds to receptors on the SAN
Heart rate decreases to return O2, co2 and Oh levels back to normal
207
How does the heart repsond To low blood O2, high CO2 or low PH levels
Chemoreceptors detect chemical changes in the blood
impulses are sent to the medulla, which sends impulses also sympathetic neurons. These secrete noradrenalin which binds other the SAN
Heart rate increases to return O2! CO2 and PH back to normal
208
Describe a Schwann cell
Surrounds axon by wrapping around many times, protecting , provides electrical insulation . Can undergo phagocytosis to fight infection and nerve Regeneratiom
209
Describe a cell body
Nucleolus, RER for proteins and neurotransmitter synthesis
210
Describe dendrons
Carrys nerve impulses towards cell body
211
Desicbe the axon
Single long fibre , carries nerve impulses away from cell body
212
Describe the myelin sheath
Forms covering of axon and made of membrane of the Schwann cell. Rich is lipid known as mylelin. Can be myleinated or unmylinated, myelinated neurons transmitted nerve impulses faster than
213
Desicbe the nodes of ranvier
Gaps between Schwann cells ( where there is no myelin sheath) gaps 2-3 um , occur every 1-4 mm
214
What is a nerve impulse
Self propagating wave of electrical disturbance that travels along the surface of the axon memebrane .
It isn’t an electrical current , it’s a temporary reversal of the electrical potential difference across the axon memebrane
215
What is the temporary reversal between in a nervous impulse
2 states called resting and action potential
216
The inside of the axon is ……. Changed relatively to the outside
Negatively
217
What is the resting potential around
-65 mV
218
What is potential difference established by
1) Na + ions AT out of axon by Na-K pump
2) K+ ions AT into axon by Na-K pump
3) AT of Na ions is greater than K ions (3Na out, 2K in)
4) Na and K both positive , more Na in tissue fluid around axon , more K in cytoplasm so a chemical gradient
5) Na diffuses back naturally into axon , K + out , but Na gates mainly shut and K mainly open
6) axon 100x more permeable to K ions - inc PD
7) electrical gradient as K+ leave outside - outside axon becomes more positively changed
8)further K+ movement become hard as they are attracted to the negative axon so prevents them movement out
9) equilibrium extravlished which chemical and electrical gradient balances
219
Desicbe the action potential.
Stimulus received by receptor or nerve ending . It’s energy causes a temporary reversal of the change on the axon memebrane
Results is a negatively changed inside memebrane becoming +40mv
220
What is the memebrane said to be during action potential
Depolarised
221
What are the basic points of action potential.
1) Na+ gated channels open
2) Na+ flood into axon
3) potential differnce reversed
4) Na+ gates closed
5) K+ gates channels open
6) K+ flood out of axon
7) inside axon returns to negative
8) resting potential restored
222
Make sure you understand potential differences across memebrane graphs
Be able to label
223
Explain action potential in detail
1)At resting potential some K voltage-gated channels are open but Na channels are closed.
2) Energy of stimulus causes some Na voltage channel in the axon membrane to open and therefore sodium ions diffuse into the axon through these channels, along their electrochemical gradient. As they are + charged, they trigger a reversal in the PD across the membrane.
3) As the Na+ diffuse into the axon, more Na channels open, increasing the Na+ influx by diffusion .
4) Once the action potential of around +40mV has been established, the voltage gates on the sodium ion channels close and the voltage gates on the K+ channels open.
5) With some K voltage-gated channels open, the electrical gradient that was preventing further outward movement of K ions is now reversed, causing more K ion channels to open. This means more K ions diffuse out, causing repolarisation of the axon.
6) The outward diffusion of these K ions causes a temporary overshoot of the electrical gradient, with the inside of the axon being more negative (relative to the outside) than usual (hyperpolarisation)
7) The gates on the K+ channels now close and the activities of the Na-K pumps once again cause
Na+ to be pumped out and K+ to be pumped in. The resting potential of -65mV is re-established
and the axon is said to be repolarised.
224
What is hyperpolarisation
Outward diffusion of K ions cause a temporary overshoot of the electrical gradient.
The inside of the axon being more Negative relative to the outside than usual
225
What happens in an unmylenated neuron
Localised electrical current are set up and the action potential is propagated along the neuron
226
Descirbe a myelinated neuron
Neuron is encased in a fatty myelin sheath
The Sheath of one cell meets the next - here the axon is unprotected
227
What happens at the unprotected areas of the axon in a mylenated neuron
Voltage gated Na+ channels of myelinated neurons are confined to these spots
( nodes of ranvier h
228
What describes the movement from one node of ranvier to another
Saltatory conduction
229
Desicribe saltatory conduction
In rush of sodium ions at one node creates enough depolarisation to reach the threshold of the next
Action potential’ jumps ‘ from one node to the next
230
Advantages of saltatory conduction
Much faster propagation of the nerve impulse that is possible in unmyleinated neurons
231
What factors effect speed of an action potential
1.the mylenated neurons
2. Diameter of axon
3. Temperature
232
How does diameter of the axon effect speed of the AP
Greater the diameter the faster the conductance due to less leakage
233
How does temp effect speed of AP
Higher temp = faster nerve impulse ( rate of diffusion is faster) , enzyme activity is faster eg. ATP
234
What is the all or nothing principle
AP only happens if the stimulus reaches a threshold value
- stimulus strong enough to cause an
it’s all or nothing as when it starts it travels to the synapse
The Ap is always the same size
The ap is the same size all the way along the axon
The transmission of the ap along the axon is the nerve impulse
235
What is rhe refractory period
Time after depolarisation where no new ap can start
236
Why is the refractory period needed
To restore the proteins of the voltage sensitive ion channels to their original resting conditions
- na+ channels Cannot be opened as it can’t be depolarised again
Also needed:
Ap travels in one directions
Produced a discrete impulse
Limits frequency of impulse
237
How does the size of stimulus detected effect ap
The number of impulses in a given time - the larger the stimulus the more impulses generated
By having neurons with differnt threshold values - the brain interpreters the number and type of neuron and thereby determine its size
238
In a neurons resting state - the outside of the membrane is ….. positively changed than the inside.
Why
More
As there are more positive ions outside the cell than inside
239
There is a differnce in charge across. The axon memebrane.
So what is it described as
Being polarised
( called a potential differnce or voltage across it)
240
What is the voltage across the memebrane when it’s at rest. Called
Resting potential
241
Roughly what is resting potential
-65mV
242
What is the resting potential created and maintained by
Sodium potassium pumps and potassium ion channels in the neurons memebrane
243
Describe how a resting potential is mainliner / created
1) sodium potassium pump moves sodium ions out of the neuron but the memebrane ist permeable to sodium ions so they can’t diffuse back in . This creates a sodium ion electrochemical gradient because there are more positive sodium ions outside the cell than inside
2) the sodium potassium pump also. Move potassium ions in to the neuron, but the membrane is permeable go potassium ions so they diffuse back out through potassium ion channels
3) this makes the outside of the cell positivity changed compared to the inside
244
What does a stimulus trigger in an axon
Sodium ion channels to open , if the stimulus is big enough it will trigger a rapid change in potential differnce called an action potential
245
What are the the key changed in potential differnce during an action potential on the Pd-time graph
1. Stimulus
2. Depolarisation
3. Repolarisation
4. Hyperpolaistion
5. Resting potential
246
How does the membrane of an axon change when it detected a stimulus
Stimulus excited the neuron cell membrane causing sodium ion channels ot open
The membrane becomes more permeable to sodium, so sodium ions diffuse into the neuron down the sodium ion electrochemical gradient, thus makes the inside of the neuron less negative
247
How does the membrane of the axon change during depolarisation
If the potential differnce reaches the threshold, more sodium ion channels open. More sodium ions diffuse rapidly into the neuron
248
How does the membrane of the axon change during repolarisation
At a potential differnce of around + 30mV the sodium ion channels close and potassium ion channels open. The memebrane is more permeable to potassium so potassium ions diffuse out of the neurone down the potassium ion conc gradient . This starts to get the membrane back to resting potential
249
How does the membrane of the axon change during hyperpolarisaton
Potassium ion channels are slow to close so there’s a slight overshoot where too many potassium ions diffuse out to the neurone. The potential differnce becomes more negative then the resting potential
250
How does the membrane of the axon change during re reaching resting potential
The ion channels are reset. The sodium potassium pump retunes the membrane to its resting potential and maintains it until the membranes excited by another stimulus
251
After an action potential can the neuron cell membrane be excited again
And why
Not immediately
Because the ion channels are recovering and they can’t be made it open -
252
When are the sodium ion channels closed
During repolarisation
253
When are potassium ion channels closed
During hyperpolarisation
254
What is the period of recovery for the axon memebrane called
Refractory period
255
When an action potential happens what happens to some of the sodium ions that enter
They diffuse sideways
256
What effect does sodium ions diffusing sideways during action potential have
Causes sodium ion channels in the next region of the neuron to open and sodium ions diffuse into that part - causing a wave of depolarisation to travel along the neuron
257
The wave moves away from part of the membrane in the ………
Why
Refractory period
These parts can’t fire an action potential
258
The refractory period acts as a time delay form one action potential to the next
What does this mean for AP:
1) AP don’t overlap, but pass along as discrete separate impulses
2) there’s a limit to the frequency at which the nerve impulses can be transmitted
3) action potentials are unidirectional ( only travel in one direction)
259
Once a threshold is reached an action potential will always fire the same change in voltage no matter how big the stimulus is
And if it’s not reached the ap won’t be fired
What is this known as
All of nothing principle
260
A bigger stimulus won’t cause a bigger action potential, what will it cause
Them to fire more frequently
261
What does it mean if neurons are myelinated
They have a myelin sheath
262
What is the myelin sheath
An electrical insulator
263
What is the myelin sheath made form
Schwann cells
264
In a myelinated neurons, where does depolarisation only occur
And how does this still allow a wave of depolarisation
At the nodes of ranvier
The neurons cytoplasm conducts enough electrical charge to depolarise the next node, so the impulse jumps form node to node
265
Is Saltatory conduction fast or slow
Very fast
266
How does an impulse travel in a non myelinated neuron
A wave along the whole length of the axon memebrane ( this is slower)
267
Why are action potentials conducted quicker along axons with bigger diameter
Less resistance to the flow of ions than in the cytoplasm of a smaller axon. With less resistance, depolarisation reaches other parts of the neurone cell memebrane quicker
268
How does temp effect speed of conduction
Increases as temp increase as ions diffuse faster,
Only increases up to around 40°c then after that proteins begin to denature and speed decreaes
269
What is a synapse
A junction between a neuron and another neuron
Or between neurone and an effector
270
The tiny gap between the cells at the synapse is called….
The synaptic cleft
271
What is the neurone before the synapse called
Presynaptic neuron
272
The presynaptic neurone has a swelling called a …
synaptic knob
273
What does the synaptic knob contain
Synaptic vesicles filled with chemicals called neurotransmitters
274
What happens when an action potential reaches the end of the neuron
It causes neurotransmitters to be released into the synaptic cleft
They diffuse across to the postsynaptic memebrane and bind to specific receptors
275
What is the neurone after the synapse xallled
Postsynaptic memebrane
276
When the neurotramitter bind to the receptors ( in a synapses what might happen
Might trigger an action potential in a neurons
Cause muscle contraction in muscle cell
Hormone to be secreted from a gland cell
277
Where are receptors only found in synapses
On the postsynaptic membrane
278
What effect does receptors only being on postsynaptic membranes have
make sure impulses are unidirectional- they only go in one direction
279
Why are neurotramitters removed from the cleft
So response doesn’t keep happening
280
How are neurotransmitters removed from the cleft
They are taken back into the presynaptic neurone or they are broken down by enzymes
281
Examples of neurotransmitters
Acetylcholine (ACh)
Noradrenaline
282
What are synapses that use acetylcholine called
Cholinergic synapses
283
How is a nerve impulse transmitted a cholinergic synapse
1) an action potential arrives at the synaptic knob of the presynaptic neurone
2) the action potential stimulates voltage gated calcium ion channels in the presynaptic neurone to open
3) calcium ions diffuse into the synaptic knob
4) influx of calcium ions into the synaptic knob cause the synaptic vesicles to move to the presynaptic membrane. They then fuse with the presynaptic membrane
5) the vesicles release the neurotransmitter acetylcholine into the synaptic cleft - called exocytosis
6) ACh diffuse across the synaptic cleft and bind to specific cholinergic receptors on the postsynaptic membrane
7) this causes sodium ion channels in the postsynaptic neurons to open
8) the influx of sodium ions into the post synaptic memebrane causes depolarisation. An AP on the postsynaptic membrane is generated if the threshold is reached
9) ACh is removed form the synaptic cleft so the response doesn’t keep happening,
284
How is ACh removed form the synaptic cleft
Brocken down by an enzyme called acetylcholinesterase (AChE) and the products are re absorbed by the presynaptic neuron and used other make more ACh
285
What happens to the calcium ions that diffuse into the synaptic knob
They are pumped out afterwards by AT
286
What 3 things can neurotransmitters be
Excitatory
Inhibitory
Both
287
What is an excitatory neurotransmitter
Depolarise the postsynaptic membrane, making it fire and AP if the threshold is reached.
288
Give an example of excitatory neurotransmitter
Acetylcholine
At the cholinergic synapse in the CNS - it binds to cholinergic receptors to cause AP in the postsynaptic memebrane and at neuromuscular junctions
289
What is a inhibitory neurotransmitter
Hyperpolarise the postsynaptic membrane ( make the potential differnce more negative) preventing it from firing an AP
290
Examples of an inhibitory neurotransmitters
Acetylcholine is an inhibitory neurotransmitter at cholinergic synapses in the heart. When it binds to receptors here, it can cause. Potassium ion channels to open on the postsynaptic membrane , hyperpolarising it
291
What happens when a stimulus is weak in terms of neurotransmitter
if weak only small amounts of neurotransmitters will be released from a neurone into the synaptic cleft. This might not be enough to excite the postsynaptic membrane to the threshold level and stimulate an AP
292
What is summation (neurotramitters)
Where the effect of neurotransmitter released form many neurons ( or one neurone that’s stimulated a lot in a short period of time) is added together l there are two types of summation
293
What are the 2 types of summation
Spatial summation
Temporal summation
294
What spatial summation
1) sometimes many neurone connect to one neurone
2j the small amount of neurotransmitter released from, each of those neurons can be enough altogether to reach the threshold in the postsynaptic neurone and trigger an AP
3) if some neurons release an inhibitory neurotramitters then the total effect of all the neurotramitters might be no AP
295
If more Inhibitpry neurotramitters are realised then excitatory neurotransmitter what happens
No AP
296
What is temporal summation
Where two or more nerve impulses arrive in quick, succession form the same presynaptic neurone.
This makes AP more likely because more neurotramitters is released into the synaptic cleft
297
What does summation do
Means synapses accurately process information , finely tuning the response
298
What is a synapse between motorr neurons and muscle cells called
Neuromuscular junction
299
What neurotramitters does neuromuscular junctions use
Acetylcholine
300
What does ACh bind to at neuromuscular junctions
Cholinergic receptors called
Nicotinic cholinergic receptors
301
What are the differences between neuromuscular junctions and cholinergic synapse
- the postsynaptic membrane has lots of folds that from clefts m these clefts store the enzyme that breaks down ACh
- the postsynaptic memebrane has more receptors than other synapses
- ACh is always excitatory at neuromuscular junction . So when a motor neurone fires an AP, it triggers a response in a muscle cell. This isn’t always the case for synapse between two neurons
302
What enzyme breaks down ACh
Acetylcholinesterase
303
What 5 ways can drugs effect synaptic transmission
1) Soem drugs are the same shape as neurotramitters so they mimic their actions at receptors
2) block receptors
3) inhibits enzymes that break down neurotramitters
4) stimulate the release of neurotramitters
5) inhibit release of neurotramitters
304
How do drugs that are the same shape of neurotramitters effect synaptic tramission
They mimic their actions at receptors
These drugs are called agonists
This means more receptors are activated
305
How do drugs that block receptor effect synaptic tramission
Block receptors so they can’t be activated by neurotransmitters ( these are called antagonists) this means fewer receptors can be activated
This results in the muscle being paralysed
306
How do drugs that inhibit enzymes that break down neurotramitters effect synaptic tramission
This means there are more neurotramitters in the synaptic cleft to bind to receptors and they’re there for longer
Lead to loss of muscles control
307
How do drugs that stimulate the release of neurotramitters effect synaptic tramission
More receptors are activated
308
How do drugs that inhibit the release of neurotramitters effect synaptic tramission
Fewer receptors are activated
309
What are synapses , what are the size
Gaps between neurons
20z30nm
310
What are the functions of synapses
A single impulse can be transmitted to a number of differnt neurons creating simultaneous responses
A number of impulses combined at a synapse allowing stimulus form differnt receptors to interact to form a single response
311
What are the steps of synaptic transmission
1) incoming AP, depolarisation in synaptic knob, ca2+ channels open and flood into knob
2) influx Ca2+ causes synaptic vesicles to fuse to presynaptic memebrane and release NT into cleft
3) NT( acetylcholine) released cleft, diffuse, AC bind to receptors on NA+ channels which causes a conformational change ( shape) and NA+ channels open.
4) NA+ to flood in causing depolarisation, new AP sent along axon of postsynaptic neurone
312
What happens for AC after synaptic transmission
ACase breaks yo acetylcholine into acetylcholine ( Ethanoic acid; and choline
So sodium ions channels close
The bits diffuse back across cleft into the presynaptic neurone allowing NT to be recycled
313
What enzyme breaks down acetylcholine
Acetylcholinesterase
314
Why is AC broken down
Beacuse if it’s not broken down it could allow it to be continuously generating new AP.
315
How is acetylcholine remade
ATP released by mitrochondia is used to recombined acetylene and choline thus recycling the acetylcholine
Thus us stored in synaptic vesicles for future use
316
Where can more acetylcholine be made
in SER
317
2 features of the synapse
Unidirectional
Summation
318
What does it mean that synapses are unidirectional
Synapses can only travel in one direction:
from the presynaptic neurone to the
postsynaptic neurone
319
What are the two types of summation
Spatial
Temporal
320
What is spatial summation
A number of different presynaptic neurones
together release enough neurotransmitter to
exceed the threshold value of the postsynaptic
neurone. Together they therefore trigger a new
action potential
321
What is temporal summation
A single presynaptic neurone releases
neurotransmitter many times over a short period.
If the total amount exceeds the threshold value
of the postsynaptic neurone, then a new action
potential is triggered
322
Explain inhibition of synaptic transmission
On the postsynaptic mebrane, some synapses the protein channels carrying Cl- ions can be made to open
Leads to inward diffusion of Cl- ions making the inside of the the postsynaptic mebrane even more negative than resting potential (hyperpolarisation (
So less likely that a new AP will be created
323
What type of muscle can you move
Skeletal muscle
324
Skeletal muscle are attached to ……. By….
Bones
Tendons
325
What attach bones to other bones and holds them together
Ligaments
326
What moves bones at a joint
Pair of skeletal muscles contract and relax to move bones at a joint
327
How do the bones of the skeleton act as levers for muscles
They are incompressible ( rigid)
This gives muscles something to pull against
328
What are muscles that work together to pull a bone called
Antagonistic pair
329
In an antagonistic muscle pair
What is the contracting and relaxing msucle called
The contracting muscle is called the agonist
The relaxing muscle is called the antagonist
330
Why do muscles only work in pairs
They can only pull when they contract - they can’t push
331
Desicbe how your biceps and triceps work antagonisticall
When biceps contracts (agonist) the triceps relaxes ( antagonist )
This pulls the bones so your arm bends at the elbow
When your tricep contracts ( agonist ) , the bicep relaxes relaxes ( antagonist) this pulls the bones so your arm straightens as the elbow
332
What are muscles stimulated to contract by
Neurons
333
What is skeletal muscle made up of
Large bundle of long cells called muscle fibres
334
What is the cell memebrane of muscle fibre cells called
SarcoLemma
335
What is the msucle cells cytoplasm called
Sarcoplasm
336
What do bits of the sarcolemma do in msucle cells
Fold inwards across muscle fibres and stick into the sarcoplasm
337
What are folds in the sarcolemma called
Transverse tubules
338
What do transverse tubules do
Help spread electrical impulses throughout the sarcoplasm
339
What stores and releases calcium ions needed for msucle contraction r
Sarcoplasmic reticulum
340
Features of msucle fibre
1) lots of mitochondria to provide the ATP that’s needed for muscle contraction
2) multinucleate (contain many nuclei)
3) lots of myofibrils
341
What are myofibrils
Long cylindrical organelles that are highly specialised for contraction
342
What do myofibrils contain and what do they don
Contain bundles of thick and thin myofilaments that move past each other to make muscles contract
343
What are thick myofilaments made of
Protein myosin
344
What are thin myofilaments made of
The protein actin
345
What would you see if you look at myofibril under an electron microscope
A pattern of alternating dark and light bands
346
What causes the dark bands in an electron microscope of myofibril
Dark bands contain the thick myosin filaments and some overlapping then actin filaments _ these are called A-bands
347
What causes the light bands in an electron microscope of myofibril
Light bands contain thin actin filaments only - these are called I-bands
348
A myofibril is made up of many short units called …..
Sacromeres
349
What are the ends of each sacromere marked with
A z line
350
What is in the middle of each sacromere
M-line
The M-line is the middle of the myosin filaments
351
What is around the M-line in a muscle
The H-zone
352
What does the Hzone contain
Only myosin filaments
353
The myofilaments don’t contract
What actually happens to make a msucle condtarxt
Myosin and actin filaments slice over one another to make the sacromeres contract
354
The simultaneous contraction of lots of sacromeres means …..
The myofibrils and muscle fibres contract
355
Do sacromere return to their origional length as the muscle relaxes
Yes
356
What theory explains muscle contraction
Sliding filament theory
357
Describe what happens to the A band, I band and H zone during msucle cosntaction
Aband stays the same length
I band gets shorter
H zone gets shorter
358
What are the 3 types of muscles
Cardiac
Smooth or involuntary
Striated or skeletal
359
What is smooth or involuntary muscles
Controlled by automatic NS
360
What is striated or skeletal
Under conscious control, oftern attached to bone - enables movement
361
Functions of the skeleton
Support - forms shape of body
Protection
Movement
362
What are bones joined by
Ligaments
363
How are muscles joined to bones
By tendons
364
Why do muscles work in groups
They can only contract So they work as antagonistic pairs
365
In an antagonistic muscle pair,
What is the contractinfand relaxed pair called
Contracting - agonist
antagonist - relaxed
366
What are the 2 types of skeletal muscles fibres
Slow twitch
Fast twitch
367
Describe slow twitch fibres
Contract slowly, provide less powerful contractions over a long period of time, adapted from enduracne
368
Where are slow twitch fire we found
Postural muscles such as calf
369
What are aerobic fibres suited for ( respiration(
Aerobic
370
What are contained in slow twitch fibres
Large stores of myoglobin for O2 storage
Glycogen for energy, lots of mitchorcondia to produce ATP , rich blood supply to deliver O2 and glucose
371
Descirbe fast twitch fibres
Contract rapidly and produce powerful contractions for a short period of time, quoted from intense exercise
372
Where a fast twitch fibres commonly found
Biceps
373
What do fast twitch fibres contain
They are thicker with more myosin filaments
Contain lots of enzymes involved in aerobic respiration. Contain a store of phosphocreatine to provide energy for muscle contractions
374
What is it called where a motor neurone connects to a muscle
Motor end plate
375
What tissues is a muscle composed of
Muscle tissue, connective tissue
376
What is muscle tissue composed of
Muscle fibres
377
What is each muscle fibre packed with
Organelles called myofibrils
378
What are myofibrils composed of
Mainly of two muscle filaments called actin and myosin
379
What is a functional unit of a myofibril called
Sacromere
380
What is thicker actin or myosin
Myosin
381
What is the dark section of a muscle called
Anisotropic
382
What is the light section of a msucle called
Isotopic
383
Describe actin
Main protein in think filaments.
Individual actin molecules twist around one another to from a filament
The two are reinforced by a protein called tropomyosin.
Attached to each tropomyosin are troponin complexes made of 3 polypeptides
384
Describe myosin filaments
Composed of polypeptide chains twisted around each other with 2 globular heads on the end, many of these polypeptides intertwined to from thick filaments
385
Describe the differences between neuromuscular junctions and choloergenic synapses
1) NJ are only excitatory , C can be excitatory or inhibitory
2) NJ are neurons to muscles , C can be neurons to neurons or neurons or effectors
3) NJ only motor Neuroms, C motor, sensory , intermediate
4) NJ the ap ends here, C ap may be produced along the next neurone
5) NJ acetylcholine binds to receptors on memebrane of muscle fibre, C the acetyl choline binds to receptors of Na+ ion channels
386
Desicbe how an AP can cause a muscle contraction
1) AP arrives at motor plate , causes release of acetyl choline into plasma membrane of muscle fibre ( called sarcolemma). Causing depolarisation to spread over sacrolemma and into muscle fibre infoodimfs ( T - Tubules) , this causes a release of Ca 2+ ions from sacroplasmic reticulum
2) ca2+ ions attach to troponin complexes and causes a change in shape wich pulls the tropomyosin out of the e myosin binding sites
3) myosin attaches to the actin, ATP- ADP+ Pi, this releases energy which provided energy for contraction / power stroke. The energy released from ATP causes myosin head to bend, pulling actin along.
4) myosin, locked onto actin contracts - pulling the actin filament. The 2 filament slide past each other
5) ATP causes release of myosin head from actin by breaking the actin myosin cross bridge
( the myosin head detaches from actin filament after it has moved)
6) the myosin head then reattaches to a different binding site further along the actin filament. A new actin myosin cross bridge is formed and the cycle repeats
Many cross bridges form a break very rapidly pulling the actin filaments along
387
After ATP causes release of myosin head in muscle contraction, if the Ca 2+ remains what happens
the cycle repeated and muscle contraction continues
388
After ATP causes release of myosin head in muscle contraction, if the ca 2+ is returned to sacroplamic reticulum what happens
The muscle relaxers
389
How is ATP supply maintained
1) aerobic respiration in muscle cells , this needs a supply of respitory substrate and o2
2) anaerobic respiration - this also produced lactate and can lead to msucle fatigue and cramp
3) creatinine phosphate - a chemcial present in mucosa cells can donate its phosphate to recharge ADP back toATO
390
What is the period between individual contractions called
Refractory period
391
What is summation in msucle contractions
Released impulses - leading to enhanced contractions
392
What is tetanus - muscle contractions
Series of quick impulses leading to a state of maximum contraction . The msucle would eventually fatigue
393
Desicbe the features of a myosin filament
globular heads that are hinged, so they can move back and forth.
Each myosin head has a binding site for actin and a binding site for ATP
394
Describe the features of actin filaments
have binding sites for myosin heads , called actin-myosin binding sites.
another protein called tropomyosin is found between actin filaments, it helps myofilamentd move past each other
395
In a resting muscle, why can’t myofilaments slide past each other
the actin myosin binding site is blocked by tropomyosin
So the myosin heads can’t bind to the actin- myosin bidning site on the acting filaments
396
What is the bond between a myosin head and an actin filaments called
Actin-myosin cross bridge
397
What happens when a msucle stops being stimulated
Calcium ions leave their binding sites and are moved by active transport beaks into the sarcoplasmic reticulum ( this needed ATP.)
This causes tropomyosin molecule to move back. So they block the actin-myosin bidning sites again
Muscles arnt contracted because no myosin heads are attached to actin filaments
Actin filaments slide back to their relaxed position, which lengthens the sacromere
398
When is aerobic respiration good for for muscle contraction
long periods of low intensity exercise
399
what is most ATP generated by
Oxidative phosphorylation in the cells mitochondria
400
When is anaerobic respiration for muscle contraction best for
short periods of hard exersize
401
how is ATP made by phosphocreatin system
ATP is made by phosphorylating ADP- adding a phosphate taken form PCr
PCr is stored inside cells and the ATP-PCr system generates ATP very quickly
402
When is ATP phosphocreatine system used and why
During short burst of very vigorous exercise as PCr runs out after a few seconds
403
What 2 words describe ATP-PCr system
Anaerobic
Alactic ( doesn’t form any lactate )
404
HOMEOSTASIS
405
What is homeostasis
Maintaining a constant internal environment despite external changes
406
What needs to be maintained in homeostasis
Temp
Blood glucose concentration
Blood salt concentration
Water potential of blood
Blood pressure
Co2 concentration
407
What is negative feedback
The reversing of a change in the internal environment
408
Describe negative feedback
Optimum condition
Change away from optimum
Receptor detects change
Communicating system informs effector
Effectors reacts to reverse change
Return to optimum
409
What is positive feedback
Increases original chmage detected by receptor
410
Describe positive feedback ( general)
Optimum
Chmage
Receptor detected
Communication system in form effector
Effector reacts ri increase chnageb
411
What is a harmful example of positive feedback
Body temp faLls
enzymes become less active
Less heat released
Temp continues to fall
412
Uses of positive feedback
Labour
Cervix open
Oxytocin released
Oxytocin inc contractions
Cervix stretches more
413
Compare negative and positive feedback
1) positive feedback is less common
2) positive feedback has a positive correlation between stimulus + prodouct or process whereas negative feedback has a negative correlation
3) positive is less associated with stability
4) positive enhances a change whereas negative resists change.
5) positive has a wider range m negative has a narrow range
6) positive might require external interruption
414
Why is it important to keep your internal environment stable
Vital for cells to function normally and to stop them being damaged
Particularly important to maintain core body temp and blood ph. As they effect enzyme activity, and enzymes control the rate of metabolic reactions
415
What happens if body temp is too high
Enzymes may become denatured. As the enzymes vibrate too much, breaking h bonds. Active site chmages and the enzyme no longer works as a catalyst. So metabolic reactions are less efficient.
416
What happens if body temp is too low
Enzyme activity is reduced, slowing rate of metabolic reactions
417
What happens if ph of blood is too high or too low
Enzymes become denatured. The hydrogen bonds that hold them in their 3D shape are broken so shape of enzyme active site chmages and no longer works as a catalyst so metabolic reactions are less efficient
418
Why is it important to maintain the right conc of glucose In blood
As cells need glucose for energy. Blood glucose conc also affects the water potential f blood.
419
What happens if blood glucose conc is too high
Water potential of blood is reduced to the point where water molecules diffuse out of cells into the blood by osmosis. Thus can cause cells to shrivel up and die
420
What happens if blood glucose conc is too low
Cells are unable to carry out normal activities becuase there isn’t enough glucose for respiration to provide energy
421
Why does homeostasis involve multiple negative feedback mechanisms for each thing being controlled
As having more than one mechanism gives more control over changes in your internal environment
You can actively increase or decrease a level back to normal
If you only had one negative feedback mechanism, all you could do would be turn it on or off
422
Only one negative feedback mechanism means …..
Slower response and less control
423
Explain how positive feedback is linked with blood clotting.
Platelets become activated and release chemcial that trigger more platelets to be activated
Platelets very quickly form a blood clot
The process ends with negative feedback when the body detect the blood clot has been formed
424
What are endotherms / homotherms
Mammals and birds that regulate their body. Temperature
They get heat from metabolism
425
What are ectotherms / poikilotherms
They are cold blooded animals who are the same temp as their surroundings
They get heat from the surroundings
426
Explain temperature regulation in ectotherms
- exposure to sunlight - they maximise their Sa of body in contact with the sun
- shelter in burrows - prevents over heating
-gain warmth from ground by pressing body agasit warm ground
-small amount of metabolic heat is generated form respiration
- colour variation eg. Lizards in colder environments are darker than in hotter environments
427
Temp regulation in endotherms for the cold (adaptations(
Small Sa:vol ratio
Fur
Blubber /fat
Small extremities
428
Temp regulation in endotherms for the hot (adaptations(
Large Sa: vol
Large extremities
Wiry fur
429
What do animals do if they are too hot
Sweat
Vasodilation
Reduction in metabolic rate
Erector pilli muscles relax so hairs lie flat
Stretch out / wear less clothes
Pant
430
What do animals do if they are too cold
No sweat
Vasoconstriction
Erector pilli contract so hairs stand up trapping a layer of warm hair
Skeletal muscles constarcr ( shiver)
Inc in metabolic rate
431
What is the controller in temp control
Thermorecpetros in hypothalamus
432
What are the effectors in temp control
Skin - vasodilation, sweating and lowering hair
433
Where are hormones made
In endocrine glands
434
How are hormones carried and to where
In blood plasma to target cells they have complementary specific. Receptors
435
Desicbe the second messager model
1) adrenaline binds to a transmembrane prOtien in muscle c liver cells
2) Aden hl Cyclades is activated wich converts ATP -> cAMP
3) the cAMP acts as a second messenger that binds to kinase enzyme. Which catalysis the conversion of glucagon to glucose
4) glucose moves out of liver by FD through channel proteins into the blood
436
What hormones are involved in control of glucose and where are they from
glucagon and insulin
Pancrease
437
What are the cells called that are involved in blood sugar control
Islets of langerhans
438
What cells produce glucagon
Alpha
439
Which cells produce insulin
Beta
440
What type of cells is the liver made from
Hepatocytes
441
What is glycogenesis
Making glycogen
442
What is glycogenolysis
Breaking down glycogen
443
What is gluconeogenesis
Making new glucose
444
What is the normal glucose levels in the blood
5 mmol dm3
445
Blood glucose levels fluctuate depending on….
How long since organism ate and level of physical activity
446
Describe insulins role in glucose control
B cells have receptors which detect a stimulus of a rise in glucose. They release insulin
Insulin binds to glycoproteins
At low insulin concentrations glucose carrier proteins are as vesicles
At high insulin conc vesicles become fused with the CSM, thus increases the number of glucose transport channels
Insulin also activates an enzyme in the liver and muscle cells to convey glucose ot glycogen
The cells are able to store glycogen in their cytoplasm as a source of energy
447
How is blood glucose level lowered
Inc rate of absorbtion of glucose in cells ( especially muscles)
Inc rate of respiration
Inc rate of glucose -> glycogen
Inc rate of conversion if glucose -> fat
448
Almost all body cells have glycoproteins wich bind with insulin,
What is the exception
RBC
449
How is glycogen involved in blood glucose levels
Alpha cells detect fall in glucose conc, glucagon released:
This attaches to protien receptors on CSM of liver cells
Activation enzymes which coneceds glycogen to glucose
Glucagon also Activates enzymes which converts AA + glycerol into glucose
Glucagon dec rate or respiratuon
450
What is the conc of glucose in the blood normal per 100cm3 of blood
90mg
451
What organ monitors blood glucose
Pancreas
452
The process of forming glycogen form glucose is called….
Glycogenesis
453
The process of breaking down glycogen is called
Glycogenlysis
454
The process of forming glucose form non carbohydrates is called..
Gluconeogenesis
455
Hormones are …….. than neutrons but have ……… effects
Slower
Longer lasting
456
Explain in detail how insulin makes glucose transporters available for facilitated diffusion
1) skeletal and cardiac muscles cells contain channel proteins called GLUT4.
2) when insulin levels are low GLUT5 is stored at vesicles in the cytoplasm of cells
3) when insulin binds to receptors in the CSM it triggers movement if GLUT 4 to the memebrane
4( glucose can then be transported into the cells through GKUT4 protein by FD
457
Where are the adrenal glands located
just above your kidneys
458
When is adrenaline secreted
When there is a low conc of glucose in your blood, , when your stressed and when your exersizing
459
What does adrenaline do
1) binds to receptors on CSM of liver cells
- activates glycogenolysis
- inhibits glycogenesis
2) activates glucagon secretion and inhibits insulin secretion , which increases glucose conc
460
What happens in type one diabetes
immune system attacks beta cells in the islets of langerhans so they can’t produce insulin .
461
What happens in type one diabetes after eating
The blood glucose level rises and stay high . This is called hyperglycaemia . And can result in death if left untreated . The kidneys can’t r absorb all the glucose so some is excreted in the urine
462
How is type one diabetes treated
Insulin therapy
Regular insulin injections , or insulin pump
This has to be carefully controlled as too much insulin can produce a dangerous drop in glucose levels called hypoglycaemia
Also
Eastinf regularly and controlling carb intake helps to avoid sudden rise in glucose
463
What is though to have caused thpe 2 diabetes
Obesity
More likely with a family history
Risk factors: lack of exersize, age , poor diet
464
Why does type 2 diabetes occur
When b cells don’t produce enough insulin or when body cells don’t repsond properly to insulin
Cells don’t respond properly because insulin receptors on their memebrane don’t work properly so the cells don’t take yp enough glucose . So bloof glucose is higher than normal
465
How can type 2 diabetes be treated
Eating helthy balanced diet , loosing weight, regular exersize
Glucose monitoring medication
466
Why is type 2 diabetes becoming increasingly common in the uk
Linked to levels if obesity
Unhealthy diets and low levels of physical activities
467
Type 2 diabetes can cause additional health proberlrm inc ….
Visual impairment and kidney failure
468
To reduce the risk of type 2 diabetes health aduvidors recommend that ….
- eat a diet that’s low in fat, sugar and slat, plenty of whole grain , fruit and veg
- regular exersize
- loose weight if necessary
469
UKs response to rise in type 2 diabetes
NHS - aims to educate people on how to have a healthier lifestyle
Health advisers challenged food industry to reduce advertising on junk food and import be nutritional value and clearer labelling
470
Page 151 practical not flashcard ex yet
471
THE KIDNEYS
472
What is the function of the kidneys
Excrete waste products such as urea
Regulate water potential of the blood
473
Describe the basic idea of ultrafiltration in the kidneys
As the blood passes through capillaries in the cortex of the kidneys, substances are filtered out of the blood and into long tubules that surround the capillaries
474
Describe the basic ideas of selective re absorption in the kidneys
Usefull substances such as glucose and the right amount of water are then re absorbed back into t the blood
475
What happens to the remaining unwanted substances in the kidneys
Pass aloft the bladder and excreted as urine
476
What is the long tube along the bundle of capillaries where the blood is filtered are called….
Nephrons
477
Around how many nephrons are in each kidney
1 million
478
How does blood enter the kidneys
Blood from the renal artery ene tear the small arterioles in the cortex of the kidneys. Each arterioles splits into a structure called glomerulus
479
What is glomerulus
A bungle of capillaries looped inside a hallow ball called a bowman capsule
480
Where does ultrafiltration take place
in the bow,ans capsule
481
The arterioles that takes blood into each glomerulus is called …….. arteriole, and the arteries that takes the filtered blood away from the glue us is called the ……… arteriole
Afferent
Efferent
482
What is different between the Afferent and efferent arteriole and why
Efferent is smaller in diameter so the blood pressure in the glomerulus is under high pressure
483
Why does the blood need to be high pressure in theglomerulus
The High pressure forces liquid and small molecules in the blood out of the capillaries and into the bowman’s capsule
484
The liquid and small molecules pass though …. Layers to get into the bow,and capsule and entered …..
3
Nephron tubules
485
What are the 3 layers that liquid and small molecules have to pass though to get pt the bowman’s capsule
Capillary wall
Memebrane ( called basement membrane)
Epithelium Of the bowman’s capsule
486
Do large molecules pass though into the bowman’s capsule
No, such as large blood cells are proteins so they stay in blood
487
What are the substances that Exeter the bowman’s capsule known as
The glomerate filtrate
488
What happens to the glomerate filtrate
Passes along the rest of the nephron and usefull subatnces are reabsorebed along the wat
Finally the filtrate flows thought the collecting duct and passes out og the kidney along the ureter
489
When does selective reabsorptun take place
As the glomerate filtrate flows along the proximal convoluted tubule (PCT) thought the loop of Henle and along the distal convoluted tubule (DCT)
490
Usefull substances leave the tubules of the ……. And Enter..?
Nephrons
Enter the capillary network that’s wrapped around them
491
Describe the epithelium wall of the PCT
Microvilli to provide a large SA for the reabsorption of usefull materials form the glomerate filtrate into the blood
492
How are useful solutes like glucose reabsorbed
Along the PCT by active transport and facilitated diffusion
493
How does water after the blood
By osmosis because the water potential of the blood is lower than if the filtrate.
Water is reavsorbed form the PCT, loop of Henle, DCT, and the collective duct
494
The filtrate that remains is ….. , which passes along the ….. to the ….
Urine
Ureter
Bladder
495
What is urine usually made up of
Water and dissolved salts
Urea
Other substances such as hormones and excess vitamins
496
What does urine not usually contain and why
Proteins and blood cells - they’re too big to be filtered out go the blood
Glucose becuase it’s actively reabsorbed back into the blood
497
How do mammals loose water
Urea ( and other waste products) in solution
Water is lost during excretion.
Lost In Sweat
498
Kidneys regulate the water potential of the blood, what is this call3d
Osmoregulation
499
What happens if the water potential is too low
More water is reabsorbed by osmosis into the blood form the tubules if the nephrons
This means the urine is more concentrated, so less water is lost during excretion
500
What happens if the water potential of the blood is too high
Less water is reabsorbed by osmosis into the blood form the tubules of the nephrons. This ,Sam’s the urine is more dilute, so more water is lost during excretion
501
Where can water be reabsorbed into the blood
Along almost all if the nephron
502
Where does the regulation of water potential mainly take place
In the loop of Henle, DCT and collecting duct
503
What is the volume of water reabsorbed by the DCT and collecting duct controlled by
Hormones
504
Where is the loop of Henle located
In the medulla
505
What is the loop of Henle made up of
Two limbs
The descending limb
Ascending limb
506
What do the limbs of the loop of Henle control
The movement of sodium ions so that water can be reabsorbed by the blood
507
Describe how movement of sodium ions are involved in controlling wage potential
1)Near the top of the ascending limb, Na+ ions are pumped out into the medulla using active transport. The ascending limb is impermeable to water, so the water stays inside the tubule.
This creates a low water potential in the medulla, because there's a high concentration of ions.
2)Because there's a lower water potential in the medulla than in the descending limb, water moves out of the descending limb (which is permeable to water) into the medulla by osmosis. This makes the filtrate more concentrated (the ions can't diffuse out — the descending limb isn't permeable to them). The water in the medulla is reabsorbed into the blood through the capillary network.
3)Near the bottom of the ascending limb
Nat ions diffuse out into the medulla, further lowering the water potential in the medulla.
The ascending limb is impermeable to water, so it stays in the tubule.
4)water moves out of the DCT) by osmosis and is reabsorbed into the blood.
5)The first three stages massively increase the ion concentration in the medulla, which lowers the water potential. This causes water to move out of the collecting duct by osmosis.
As before, the water in the medulla is reabsorbed into the blood through the capillary network.
508
The volume of water reabsorbed into the capillaries is controlled by….
by changing the permeability of the DCT and the collecting duct
509
The water potential of the blood is monitored by cells called….. in part of the brain called…..
Osmoreceptors
Hypothalamus
510
When the water potential of the blood decreases, what happens with osmoreceptors
Water will move out of the osmorecepor cells by osmosis. This causes the cells to decrease in volume . This sends a signal to other cell in the hypothalamus, which sends a signal to the posterior. Pituitary gland . This causes the posterior pituitary to release a hormone called anti diuretic hormone into the blood
511
What does ADH do
Makes the walls of the DCT and collecting duct more permeable to water
So more water is reabsorbed form these tubules into the medulla and into the blood by osmosis .a small amount of conc urine is produced, which means less water is lost form the body
512
What happens to blood ADH when your dehydrated
1) the water content of the blood drops so it’s water potential drops
2) thus is detected by osmoreceptors in the hypothalamus
3)the posterior pituitary gland is stimulated to release more ADH into the blood
4) more ADH means that the DCT and collecting duct become more permeable, so more water is reabsorbed into the blood by osmosis
5) a small amount of highly concentrated urine is produced and less water is lost
513
What happens other than blood ADH when your hydrated
1) the water content if the blood rises do it’d water potential rises
2) This is detected by the osmoreceptors in the hypothalamus.
3) The posterior pituitary gland releases less ADH into the blood.
4) Less ADH means that the DCT and collecting duct become less permeable, so less water is reabsorbed into the blood by osmosis.
5) A large amount of dilute urine is produced and more water is lost.
514
What is the epithelium of renal capsule made of
Podocytes
515
Describe the structure of the endothelium of blood capillaries and what’s does it provide a barrier for
Thin
Perforated with thousands of pores
Provides a barrier for cells but not plasma proteins
516
Descirbe the structure of basement mebrane and what’s does it filter out
Mesh work of collagen and glycoprotein and fibres
Water + small molecules to pass through
Proteins are too large and are repelled by negative charges on fibres
517
Describe a podocyte
Each cell has many foot like extensions projecting from its surface, the extension wrap around capillaries of the glomerulus and interlink with extension form neighbouring cells
These extensions fit together loosely leaving filtration slits , filtered fluids pass through these slits
518
Give some examples of what forms the glomerate filtrate
Water
Glucose
Amino acids
Vitamins
Drugs
519
Adaptations of the PCT epithelium cells
Microvilli and infloldings at their base which give a higher SA to transfer substances back to the capillaries
A high density og mitrochondia to provide ATP for active transport
520
Describe the process in the proximal convoluted tubule
• Na+ pass out of cells lining PCT by active transport into blood
capillaries which carry them away. Na+ content of cells lowered.
• Na+ now diffuse down conc. Gradient from lumen out of PCT into
epithelial cells through special carrier proteins by FD.
• These carrier proteins also carry another molecule e.g. glucose,Amino
acids WITH the Na+ . This is co- transport.
• The molecules which have been co transported into the cells of the
PCT then diffuse into the blood.
• All the glucose and most other valuable molecules are reabsorbed.
521
Describe the hairpin countercurrent multiplier system
This arrangement is known as the hairpin countercurrent multiplier system.
It increases the efficiency of salt transfer from the ascending limb to the descending limb
Thus, causing a build up of salt in the surrounding tissue fluid
‘
So….’ Water moves out of the descending limb, making the fluid in the tubule very salty. Salt then diffuses out of the base of the ascending limb as it is at high concentrations (very negative water potential), and then is transported out using active transport at the top of the ascending limb The removal of ions from the ascending limb makes the urine very dilute and water can then be reabsorbed by the body from the distal tubules and collecting ducts….
522
What happens in the DCT
From, the top of the ascending limb the tubule fluid passes through the DCT, AT adjusts conc of various salts in the tubule
523
What happens in the collecting duct
When the fluid reaches the collecting duct it has a high water potential (less negative).
• The collecting duct carries fluid back into the medulla, which contains a lot of salts
(low/very negative water potential)
• Therefore, as the fluid passes through, water moves by osmosis, from the tubule fluid into the surrounding tissue.
• It then enters the blood capillaries by osmosis and is carried away
524
What is the permeability of the collecting duct walls controlled by
ADH - anti diuretic hormone
525
How does ADH work
Cells in the wall have membrane bound receptors for ADH
• The ADH binds to these receptors and causes a chain of enzyme controlled
reactions inside the cell
• The end result is to insert vesicles containing water permeable channels (aquaporins) into the cell surface membrane
• This makes the walls more permeable to water
• More ADH in the blood means more aquaporins are inserted allowing more water to be reabsorbed, and less, more concentrated urine with a lower (more
negative) water potential
526
What does less ADH cause
The cell surface membrane folds inwards to create new vesicles that remove the aquaporins from the membrane
• The wall is less permeable and more water passes out in urine with a higher (less negative) water potential
