Topic 8 Flashcards
What is the peripheral nervous system made up the
Sensory nerves
Motor nerves
Relay neurone
What is the peripheral nerves system divided into
Autonomic nervous system (involuntary)
Somatic nervous system
Voluntary stimulates skeletal muscles
What is the autonomic nervous system divided into
Sympathetic nervous system stimulated the body for fight or flight response ie increase heart rate
Parasympathetic nervous system
Prepares body for rest and digest
Distinguish between nerve and neurone
Neurone is single cell
Nerve is a group of neurones working together and
What are dendrites and axons
Dendrites- conduct impulses toward cell body
Axon transmit impulses away from cell body
What are the 3 types of neurone and state their function
Motor neurone they conduct impulses from the CNS to effectors
Sensory neurone- they carry impulses from sensory cells to CNS
Relay neurone- they are found in the CNS and they connect with other nerve cells
What the myelin sheath and what is it made from
They are around the axon and it’s a fatty insulating layer made up of Schwann cells
They enable the nerve impulses to happen faster
State the stages in the reflex arcs
A stimulus is detected by receptors and it generates a nerve impulse
Sensory neurones conducts a nerve impulse to the CNS
Sensory neurone enter the spinal cord through dorsal route
Synapse former between sensory and relay neurone
Relay neurone forms a synapse with motor neurone
Motor neurone carries impulses to an effector hormones which produces s response either bicep moving from flame
What controls the size of a pupil and state the two antagonistic muscles involved
Iris
Radial and circular muscles and these muscles are controlled autonomic nervous system
What controls the radial and circular muscles
Radial- sympathetic reflex
Circular muscles control parasympathetic reflex
State what each muscle is doing when the pupil constricts
Radial muscles relax
Circular muscles contract
State the role of each muscle when the pupil dilate
Radial muscles contract
Circular muscles relax
What is the resting potential of an axon and why is the membrane said to be polarised
-70mv
The inside of the axon is more negative than the outside
What is the role of the sodium potassium pump and how is it driven and what does it create
It’s role is to pump carry sodium out of the cell and potassium into the cell which creates polarisation
And it creates a concentration gradient and it driven by the energy from the hydrolysis of ATP
How was the resting potential of the an axon found
Experiments hodges placed two electrodes one in the bathing solution and one across the axon membrane and they found a potential difference of -70 mv
With the inside of the axon being more negative than the outside ( hence its polarised
Describe the process results in the resting potential of an axon to be -70 mv
The na/k pump creates a concentration gradient across the membrane
K plus diffuses out of the cell down the k concentration this action causes the outside of the memebrane to be more positive than the inside and it results in a potential difference being created as
The potential difference means some k ions willl be pulled back into the cell(some cl ions move out of the cell to balance the charge due to the pd )anions build up in the cell
When the pd across the membrane is around -70 mv the electrical and chemical gradient balance out and there no move movement of k
What is the chemical gradient and electrical gradient in resting potential
Chemical gradient is k going out via the pump
Electrical gradient- k being pulled in and cl going out
State the permeability of the membrane towards k and na ions
The membrane is permeable to potassium as it can go through a channel
It’s impregnable to sodium
What is depolarisation
This is when pd across the membrane is locally reversed with the outside of the axon now becoming negative and the inside being positive +40mv
What is repolarisation
When resting potential returns back to -70mv
What is action potential
The large change in voltage across the memebrane
What are the 3 stages in the generation of action potential
Depolarisation
Repolarisation
Restoring resting potential for
What are voltage dependant gated channels
They are channels that open as a result of changes in voltage across a membrane they block passage of na and k channels
What occurs in depolarisation
Due to stimulation The shape of the sodium gate changes shape due to change in PD across the membrane this opens some voltage dependant sodium ions channels
This causes na ions to flow inside the axon,meaning depolarisation increases which causes positive feed back meaning more sodium channel gates to open once a certain pd threshold is reached
This eventually leads to reverse in polarity meaning the PD across the memebrane reached +40 mv
What is meant by all or nothing
It means that actions potential either occur or not
What occurs in repolarisation
After 0.5ms the voltage dependant na channels close spontaneously
The voltage dependant k channels open meaning potassium ions move out of the axon by diffusion down an electrochemical gradient
As they flow outside of the cell the inside again becomes negative
How is resting potential restored
The voltage dependant k channels close and k ions begin to diffuse into the axon and it aids in restavlishing the rest potential
Furthermore the sodium potassium Pumps aids in restoring the original ion concentration across the CSM
What is hyperpolarisation
It is when the potential difference is more negative than the normal resting potential in a membrane
Describe each stage in transmission of action potential known as propagation
When stimulated the voltage dependant na+ channels open and this causes Na* ions to flow into the axon causing depolarisation of the memebrane and it causes localised electric currents to be generated
This in turn causes na+ ions to move to the adjacent polarised region and PD to changes across that part of the memebrane
The change in the potential difference in the membrane adjacent to the first action potential initates a second action potential at the site the first action potential the membrane because depolarised
The second action potential Iniates a 3rd action potential(electric currents cause nerve impulse move along the axon
What is meant by refractory period and what does this mean
A period after stimulation in which nerve impulse is unresponsive to further stimulation means action
Potential can’t be propagated backwards
What does refractory period mean for action potential direction
It means that it only goes in one direction as action potential can’t be generated in the same section
How long does refractory period last
Until resting potential is restored and na and k channels have returned ri their normal resting states
Where are the nodes of ranvier and what happens there
They occur at intervals in the myelin sheath and it’s where depolarisation takes place
What is the role of the myelin sheath
It acts as an electrical insulator and it prevents ions moving across the membrane
Describe the process of saltatory conduction
In depolarisation ions flow across the memebrane at one node,this sets up a circuit which reduces PD at the next node triggering an action potential
This result in a faster wave of depolarisation
What is meant by a synapse and synaptic cleft
Synapse is when two neurone meant
Synaptic cleft is the gap between them
Name the 3 main stages in synaptic action
Neurotransmitter release
Stimulation of post synaptic memebrane
Inactivation of neurotransmitters
Describe the process of neurotransmitter releases
An action potential depolarises a pre synaptic membrane and it increases its permeability to ca ions
There is a greater concentration outside the cell of ca ions and so Thei diffuse into the cytoplasm across the membrane
The increased ca ions cause the synaptic vesicles which contain acetylcholine to fuse with the pre synaptic membrane this causes them to release their contents by exocytosis into the synaptic cleft
Why are ca ions important in the release of a neurotransmitter
When they increase in concentration they cause synaptic vesicles to fuse and it results in them releasing their contents by exocytosis
Describe the process in stimulation of a post synaptic membrane
Acetylcholine molecule binds to a protein receptor on the post synaptic membrane causeing it to change shape
This makes it more permeable na ions the flow of na ions across the postsynaptic memebrane causes depolarisation and if it’s sufficient an action potential is produced which is propagated
Where are the nodes of ranvier and what happens there
They occur at intervals in the myelin sheath and it’s where depolarisation takes place
What is the role of the myelin sheath
It acts as an electrical insulator and it prevents ions moving across the membrane
What factors affect depolarisation of the post synaptic membrane
Depends on the amount of acetylcholine that reaches the post synaptic membrane
Functioning receptors on the post synaptic membrane
Why are na ions important in stimulation of the post synaptic membrane
It’s causes depolarisation of the post synaptic membrane meaning an action potential can occur
How does neurotransmitter become inactived
Acetylcholinesterase breaks down the acetylcholine so it can’t bind to receptors
Some of the broken down products are reabosred by the pre synaptic membrane to be reused
State the role of acetyl cholinesterase in inactivation of the postsynaptic neurone
It breaks down acetylcholine meaning it can’t bind to receptors
State the two types of synapses
Excitatory and inhibitory
What do excitatory synapses do
They make the post synaptic memebrane more permeable to sodium ions
As a result of summation
What is summation and state the two types and what they are
Summation is the adding up of the effect of impulses
Spatial summation - this is when lots of different neurones are producing impulses
Temporal summation- when several impulses arrive at a synapse after travelling along one neurone one after the other
What is meant by an inhibitory synapse
These synapses mean it’s less likely that an action potential will result in the post synaptic membrane
Describe how inhibitory synapses work
A neurotransmitter from these synapse causes chloride channels in psm to open which enables cl ions and k + ions to move down their diffusion gradient with cl going into the cell and k going out
These cause hyperpolarisation of membrane in which theirs a greater pd with the membrane being more negative inside
This means depolarisation is less likely to occur
In inhibitory synapse what does the movement of cl and k ions result in and what effect does this have
They cause hyperpolarisation of the membrane in which the inside of the membrane is more negative meaning depolarisation in that membrane is less likely to occur
Describe how pupil size is controlled
When light strikes photo receptors in the retina it causes nerve impulses to pass along the optic nerve to sites in the CNS , group of co ordinating cells
These cells send impulses along the pns via motor neurotransmitter they go to the circular muscles of the iris which causes them to contract and at the same time radial muscles relax
Thus action causes the pupil to construct
Compare the differences in nervous and hormonal co ordination
Nervous control:electrical transmissions by nerve impulses and chemical transmission
Fast acting
Short term muscle contraction
Responses are local
Neurones carry action potentials with connections to specific cells
Hormonal control
Chemical transmission via blood
Slower acting
Longer term changes
Responses tend to be widespread
Blood carries hormone to all cells
What is IAA and state it’s function
Indoleacetic acid and it’s an auxin, it stimulates growth which results in cell elongation
Where are auxins produced in a plant
The meristem tissue in the tip
Why in the face of unilateral light will the shoot bend towards the light
In The shaded area of the plant more auxin passed down that side and the increase in concentration on that side results cell elongation in the shaded area
Cell elongation is inhibited in the unshaded side of the plant due to sunlight and so there’s a reduced amount of auxin concentration
This results in shooting bending towards the light
Why when the tip of the shoot is discarded cell elongation is inhibited
The tip contains meristem tissue that produces IAA which causes cell elongation
What is phototropism
Growth of a plant in response to light
What is tropism
It’s the response of a plant to a direct stimulus
What is the difference between positive and negative tropism
Positive is growth towards the stimulus
Negative is growth away from the stimulus
In propagation of a nerve impulse what causes the sodium ions to move to the adajecent membrane
The localised currents that are generated
In an action potential why do the voltage-dependant potassium channel gates open
Due to the depolarisation of the membrane
When the membrane is hyperpolarised give ways as to which the normal potential difference is restored
The closing of the voltage dependant k channels
And potassium ion diffusion into the axon
The work of the sodium potassium pump with na+ pumped out of membrane and k into it
In a nerve impulse state the role of the localised electrical current
They cause a wave of depolarisation to occur as they cause Na+ ions to move into the adajecent resting region stimulating depolarisation to occur their this imitating an action potential
In synaptic transmission describe the role of acetylcholine
It binds onto specfic receptor proteins and causes it to change shape which allows cation channels to open making it more permeable to sodium ions
This leads to depolarisation
Where are auxins like IAA synthesised
In growing root and root tips(meristems
How is IAA transported
In the phloem for long distances and via specific carried proteins in the cell membrane for short distances
Explain how auxins work in changes in the target cells
They bind on to protein receptors in the target cells
This action activates second messenger signal molecules which activate the transcription of auxin regulated genes
These genes produce proteins that bring about metabolic changes in the cells
What must happen to a cell wall before it can expand and describe this process up to expansins
It must first loosen its thought that the auxin causes acidification of the cell wall
As they stimulated the activity of proton pump that move H+ ions out of the cytoplasm into the cell wall it creates a low ph which activates proteins called expansins
State what expansins do and how it leads to expansion of the cell wall
They disrupt the bonds that hold cellulose microfibrils and hemicelluloses together this causes loosening of the cell wall
There’s a slippage of polysaccharides resulting in bonds reforming in new locations this enables expansion of the cell
How does cell elongation occur
The potential difference across the membrane increases due to acidification of the cell wall
This results in osmosis as the uptake of ions into the cell causes water uptake to take place this cause the cell to swell causing cell elongation
How does cell wall acidification take place
Auxin stimulates the proton pump to move h ions out of the cytoplasm into the cell wall causing a low ph
What are the two types of photoreceptors in the human retina
Rods and cones that are both sensitive to light
What is the difference between rods and cones
Cones allow colour vision in bright light
Rods only give black and white vision but they work in both dim and bright light
What is rhodopsin
It’s a photochemical pigment that absorbs light which results in chemical changes it can be found in the outer segment in vesicles
State the parts of the eye and their function
Choroid-black layer prevents internal reflection of light
Vitreous humour-transparent jelly
Retina-contains light sensitive light
Lens-focuses light on the retina
Iris-controls the amount of light that enters the eye
Clilairy muscles-they alter the thickness of the lens
Blind spot-no light sensitive cells are here
What are the 3 layers of cells that make up the retina and state their arrangement
Bipolar neurone cells,ganglion neurones,rod cell
Ganglion cell-bipolar cell-rod They form synapses with them
What axons make up the optic nerve
Biopolar neurone which in synapses with ganglion neurones
Describe what happens to rod cells in the dark
Sodium ions flow into the outer segment through non specific cation channels
They move down a concentration gradient into the inner segment where they are pumped out it of the cell
This pumping out of Na causes depolarisation of the cell which triggers the release of a ns called glutamate from rod cells
This happens continousley in the rod cells and it binds to the bipolar cells which stops it depolarising
Describe the process that happens in the rod cells in the presence of light
Light falls on rhodopsin causing it to break down into retinal and Opsin
Opsin causes a range of reactions to happen which results in the hydrolysis of a molecule which binds to the cation channel that’s attached in the outer segment
The breakdown of molecule causes the cation channels to close
This means less sodium ions enter the rod cells but the inner segment continues to pump Na out this results in hyperpolarisation and glutamate isn’t released
This means the bipolar cell can depolarise and it results in an action potential being produced in the optic neurones
State the role of Opsin
It causes a series of membrane bound reactions that results in the breakdown of a molecule that attaches to and closes cation channels that
In the presence of light how does hyperpolarisation occur
The closing of the cation channels makes the inside of the inner segment more negative as more Na is pumped out but no Na is coming in
What is the outer layer of the brain called and what is it made up of
It’s called grey matter it’s mainly made of nerve cell bodies,synapses and dendrites
Why is white matter white and what does it contain
It’s contains nerve axons that connect neurones in different parts of the brain
It’s white because of the axons myelin sheath
What are the four lobes in the brain
Frontal
Parietal
Occipital
Temporal
What is the function of the thalamus
It routes all incoming Sensory information to the correct part of the brain via axons of the white matter
What is the function of the frontal lobe and what does it contain
It’s concerned with higher brain functions like descion making,reasoning and consciousness of emotions
The motor cortex
State the function of the motor cortex
It sends info to the body via motor neurones to carry our movements
What is the function of parietal lobe
It’s concerned with sensation(pain)as well as orientation
What is the role of the occipital lobe and what does it contain
It contains the visual cortex and so is associated with processing visual info
What is the role of the temporal lobe
It’s concerned with processing auditory information
Where is the hypothalamus and what does it contain and describe some of its features
It lies below the thalamus and it’s contain the thermoregulatory centre
It also acts as an endocrine gland as it secretes hormones
What is the function of the hippocampus
It’s involved in long term memory
What is the basal ganglia responsible for
They are responsible for selecting and initiating stored programmes for movement
Explain how the right and left hemisphere are able to communicate with one another
White matter known as the corpus callosum enables them to communicate with each other
What is the cerebellum responsible
It’s responsible for balance
Coordinates movements as they are being carried out as it receives info from the primary motor cortex
State where the brain stem extends from
The midbrain to the medulla oblongata
What is the function of the midbrain.
It relays info to the cerebral hemispheres ie auditory info
What is the role of the medulla oblongata
It regulates bodily processes that we don’t control consciously ie heart rate,breathing and blood pressure
What is neural plasticity
That as a result of experience or damage the brain is able to change in structure and function
Give the 4 types brain imaging research
FMRI
PET
MRI
CT
What is a phytochrome
It’s a light absorbing pigment molecule that has a protein component bonded to non protein
What are the two non protein components had two forms
Pr-which absorb red light
Pfr-they absorb far red light
State how CT scans are performed
It uses lots of narrow beam of X-rays that are rotated around an individual so it passes through tissues at different angles
The X-rays are detected and they at used to produce an image of thin brain structure
How are CT scans performed
They can be used to diagnose medical issues like damaged areas of the brain
Ie the location of bleeding on the brain
Blood has different density so appears lighter
Give some issues with CT scans
They have a limited resolution
Only look at structures not function
X-rate create issue of cancer
How do MRI work
The magnetic field is placed on a person as they pass through a tube
Another magnetic field is superimposed by the radio waves
The two combined fields cause the direction and frequency of the hydrogen nuclei to spin and change as they absorb energy from the radio waves
They release the energy once the radio waves are turned of and this energy release is detected and a signal sent to a computer and an image is produced
What is dark adaptation
This is when the rhodopsin rebuilds its self after being broken down by light
Compare the structures of the neurones ie describe
Motor neurone and relay neurones have many short dendrites carry
Motor neurone have long axons the others don’t
Sensory neurone have long dendron,relay neurones Have short dendrites
