nervous coordination

Question 1

what are the series of steps involved in coordinating a nervous response

Answer 1

-stimulus - receptor - coordinator (CNS) - effector - response

-sensory neuron bwt receptor and coordinator
-relay neuron in CNS
-motor neuron in bwt coordinator and effector

Question 2

how can the nervous system be categorised

Answer 2

-Central nervous system - recive info, process info and send response back
-peripheral - nerves leading to and from the brain and spinal cord

these can then be further split into the somatic and autonomic system

Question 3

what is the somatic nervous system

Answer 3

controls skeletal muscles and external senory receptors - voluntary actions - conscious

Question 4

what is the autonomic system

Answer 4

automatic and not conscious and controls internal organs
can be further categorized into sympathetic and parasympathetic - antagonistic

Question 5

what is the sympathetic system

Answer 5

speeds up the system

Question 6

what is the parasympathetic system

Answer 6

slows down the system

Question 7

what are sensory neurons

Answer 7

carry impulses from receptors to the CNS

Question 8

what do all neurons contain

Answer 8

cell body
-contains nucleus most of the cytoplasm and organelles

Neurones have a long fibre known as an axon
-The axon of some neurones is insulated by a fatty sheath with small uninsulated sections along its length (called nodes of Ranvier) - stretched out cytoplasm

The sheath is made of myelin, a substance made by specialised cells known as Schwann cells
-Myelin is made when Schwann cells wrap themselves around the axon along its length

The presence of Schwann cells means that the electrical impulse does not travel down the whole axon, but jumps from one node to the next
-The ‘jumping’ of the electrical impulse between nodes of Ranvier is called saltatory conduction
This speeds up the conduction of the impulse and its transfer from one cell to another

Neurone cell bodies contain many extensions called dendrites
-This means they can connect to many other neurones and receive impulses from them, forming a network for easy communication

Question 9

what are motor neurons

Answer 9

carry impulses from the CNS to the effectors

Question 10

what are relay neurons

Answer 10

transmit impulses within CNS

Question 11

how to distinguish bwt motor and sensory

Answer 11

motor - cell body at the end
sensory - cell body in middle

Question 12

what is the reflex arc

Answer 12

shortest route nwt a receptor and an effector
designed to give a rapid response to limit damage

not conscious and does not need to be learned

Question 13

what are the electrical impulses like in a neuron

Answer 13

change in charge at the end of neuron caused by rapid movement of sodium and potassium ions into and out of the axon
-polarised

Question 14

what is the resting potential

Answer 14

-when a neuron is not conducting a nerve impulse
-uneven distribution of ions inside and out of the axon
-more +ve charge outside than in

Question 15

what is the value of the resting potential

Answer 15

-70 mV

Question 16

what are the 2 ways in which the resting potential of a neuron is maintained

Answer 16

-by active transport using sodium-potassium pump
-by facilitated diffusion using carrier proteins

Question 17

how does resting potential work

Answer 17

-in neuron there is a charge of -70 mV at rest
-sodium-potassium pump actively transports 3 Na+ out and 2 K+ in to the cell at expense of ATP
-K+ ions can diffuse back out of the cell via open gated K+ channels
-very few Na+ can diffuse back in the cell because Na+ gated channels are closed
-so net effect in the cytoplasm of the neuron is -ve charged compared with outside of the cell to a value of -70 mV

Question 18

what is the action potential

Answer 18

where a neuron is stimulated with an electric current and there is a sudden change in potential difference bwt -70 mV and +40 mV
and is said to be depolarised

Question 19

how to describe the action/resting potential graph

Answer 19

-Na+ gated channels open at the point of stimulation
-higher conc of Na+ outside the axon than inside - creating a conc gradient
-Na+ ions move along an electrical gradient and the axon becomes +ve charged to +40 mV
-at this point the increase in charge causes there to be a change in the tertiary structure of the channel protein and so the Na+ close and K+ open
-so K+ diffuse out of axon down conc gradient
-outward movement of +ve charge returns to normal and thus is repolarisation
-since the K+ ions leave the axon the pd becomes even more -ve than the normal resting value and causes a brief overshoot of -70 mV - hyperpolarisation
-K+ gates close and begins to act as normal

Question 20

what is the refractory period and why is it important

Answer 20

when both the Na+ and K+ channels remain closed and the membrane cannot be repolarised
-this keeps the action potential discrete
-ensure action potentials can only pass in one direction

Question 21

when will depolarisation take place

Answer 21

when the stimulus exceeds the threshold level required to open the Na+ channels -therefire it is called all or nothing law as it needs to be max to happen

Question 22

what happens when an action potential is stimulated

Answer 22

-Na+ gated channels in the axon membrane open
-Na+ pass into the axon down the electrochemical gradient
-reducing the potential difference across the axon membrane as the inside becomes less negative - depolarises - to +40 mV
-continues to allow more gated channels to open

Question 23

how are action potentials transmitted and why does it only go in one direction

Answer 23

-depolarisation causes Na+ to move in and they attract the -ve charge region
-depolarisation at the membrane of the stimulus/ first action potential causes Na+ to diffuse along the axon depolarising the next section of the axon - causes more Na+ channels to open
-the action potential can only go in one direction as the area behind it is still in the refractory period and is hyperpolarised so not able to generate another action potential

Question 24

what is the speed of a neuron transmission affected by

Answer 24

-diameter of axon - wide axons conduct impulses more quickly than narrow ones as there is less leakage of ions from wider neurons
-myelin sheath
-tempurature

Question 25

how does the myelin sheath affect transmission of a neuron

Answer 25

-myelinated neurons tend ot pass impulses ore quickly than unmyelinated ones -in non-myelinated the impulse is transmitted along the neuron when each section of the membrane causes the next to become depolarised - slow -myelinated nuerons conduct quickly because of the action potentials that only occur at the nodes of Ranvier -local currents are stet up in which Na+ move from one node to the next - saltatory conductin

Question 26

why is saltatory conduction more effiecient

Answer 26

ions only exchanged at the nodes -this greatly reduces the energy needed for the active transport of Na+ and K+ -wide myelinated neurons can carry impulses for as quick as 120 ms-1 whereas unmyelinated giant axons of the squid - 25 ms-1

Question 27

how does temperature affect the rate of transmission of neurons

Answer 27

-higher temp the faster the nerve impulses as the ions are bale to diffuse faster -if temp becomes too high the membrane proteins denature as will the enzymes of respiration which produce ATP that is required for the active transport by the Na-K pump impulses then fail

Question 28

what starts off an action potenital

Answer 28

-generated by a wide variety of stimuli such as light,sound,touch and temp or chemicals -structures which respond to these are sensory receptors -some are specialised cells found in sensory organs such as the rods and cones in the eye -other receptors are simply the ends of sensory neuron themselves eg the pacinian corpuscles found int the dermis of the skin

Question 29

how does the pacinian corpuscles work

Answer 29

-pressure is applied to the corpuscle the sensory neuron inside becomes deformed opening the Na+ and K+ channels -allows Na~+ in and K+ out causing depolarisation -the harder the pressure the more channels open until eventually the threshold value is reached and an action potential is triggered -as pressure increases action potentials are triggered more frequently

Question 30

what is the space in between 2 neurons known as

Answer 30

synapse that contains -synaptic cleft -pre-synaptic neuron -post-synaptic neuron -synaptic knob/bulb - this contains vesicles which have neurotransmitters in them

Question 31

what happens when an action potential reaches a synapse

Answer 31

arrives at pre-synaptic bulb and causes the release of the transmitter substance which then diffuses across the synaptic cleft and binds to receptors on the post-synaptic membrane causing it to become depolarised and triggering an action potential in the post-synaptic neuron

Question 32

describe the process of action potential transmission in a synapse

Answer 32

-action potential arrives at the pre-synaptic bulb -Ca2+ gated channels open in the pre-synaptic membrane -Ca2+ diffuse into the pre-synaptic bulb -causing vesicles containing neurotransmitters to move to and fuse with to pre-synaptic membrane -neurotransmitter binds to complementary receptors on the post-synaptic membrane -Na+ gated channel proteins in the post-synaptic membrane open so Na+ diffuse in -causing an action potential (depolarisation_ -enzyme breaks down neurotransmitter - sub for the specific neurotransmitter and enzyme - into component parts -these diffuse back across the synapse and are repackaged in the vesicles

Question 33

what are synapse and enzymes that use acetylcholine called

Answer 33

cholinergic synapse -enzyme that breaks this down is acetylcholinesterase

Question 34

what is the synapse called for noradrenaline

Answer 34

-adrenergic

Question 35

what are inhibitory synapses

Answer 35

-release of transmitter cause the post-synaptic membrane to be hyperpolarised -this is known as inhibitory postsynaptic potential -prevent impulses passing to the next nueron

Question 36

what is synapse fatigue

Answer 36

-when many action potentials arrive at the synapse in a short period of time the neuron runs out of transmitter substance -post-synaptic neuron will not be stimulated and the response will be lost -this is known as adaption and allows organisms to ignore repeated stimuli which are harmless

Question 37

what is the neuromuscular junction

Answer 37

-the post-synaptic membrane of the synapse is a muscle fibre membrane called the sarcolemma -synaptic transmission works in the same way

Question 38

how does the sarcolemma work

Answer 38

-depolarised when acetylcholine -released by the presynaptic membrane of the neuron diffuses across the synapse and binds to the protein receptors in the sarcolemma -this leads to the depolarisation of the membranes -causing muscle contraction

Question 39

what are the 3 roles of the synapse

Answer 39

-ensure one-way transmission of nerve impulse -increase possible range of actions in response to the stimuli -involved in memory and learning

Question 40

how does the synapse ensure one-way transmission

Answer 40

-only pass from pre-synaptic neuron to the post-synaptic neuron -this allows impulses to be directed to specific goals rather than randomly spreading throughout the nervous system

Question 41

how does the synapse increase the range of actions in response to a stimuli

Answer 41

-allow a wider range of behaviour then what would be possible if neurons were directly linked to each other -each neuron in the brain synapses thousands of other therefore thousands of different responses are possible

Question 42

what happens when the amount of neurotransmitter released by the pre-synaptic neuron is not enough to cause depolarisation

Answer 42

-spatial summation -temporal summation

Question 43

what is spatial summation

Answer 43

-several action potentials arrive at a synapse from different neurones at the same time -each release some neurotransmitter and the combined amount is now enough to depolarise the post-synaptic neuron an trigger an action potential;

Question 44

what is temporal summation

Answer 44

-action potentials arrive at the synapse from one neuron but in a very rapid succession -increase the amount od neurotransmitter release is enough to depolarise the post-synaptic neuron and trigger an action potential

Question 44

how do drugs affect transmissipn at synapse

Answer 44

Chemical or drugs can have a major impact on the functioning of the brain and nervous system Some prescription drugs can have a beneficial effect on those suffering from neurological disorders while recreational drugs can have a damaging or even fatal effect Many drugs have been found to produce a specific effect on synaptic transmission They can have different modes of action such as: -Stimulating the release of a neurotransmitter -Providing the chemicals needed to synthesise neurotransmitters -Acting in the same way as a neurotransmitter by binding to the same specific receptor -Preventing the reuptake of the neurotransmitter by the presynaptic neurone -Research is ongoing to further understand how several drugs work in the hopes that they can be used to treat nervous disorders

Question 45

what is the effect of dopamine on synapses

Answer 45

Dopamine is a neurotransmitter involved in muscle control Individuals that suffer from Parkinson's disease produce insufficient amounts of dopamine There are two types of drugs that are used to treat this disease A dopamine agonist - produces the same effect as dopamine by binding to the same receptors A dopamine precursor - this can be used to synthesise dopamine in the neurones

Question 46

what are the 2 types of neurotransmitters and their function

Answer 46

There are many different neurotransmitters that bind to specific receptor molecules They are often restricted to certain regions of the brain so that they have a specific function Some are excitatory and some are inhibitory Excitatory neurotransmitters result in the production of an action potential Inhibitory neurotransmitters prevent the production of an action potential. They do this by causing potassium ions to leave the postsynaptic membrane

Question 47

what is the effect of morphine

Answer 47

Dopamine also plays a vital role in pain relief Chemicals called endorphins which are produced in the brain can stimulate the release of dopamine The endorphins attach to opioid receptors found on presynaptic neurones that release dopamine molecules Exercise is a natural way to cause the release of endorphins Morphine is a chemical very similar in structure to endorphins and so it can provide pain relief by stimulating the release of dopamine

Question 48

what is the effect fo cocaine on synapse

Answer 48

Cocaine also affects levels of dopamine It binds to the dopamine transporter protein This prevents dopamine from binding to the transporter so it is not able to move through the membrane back into the presynaptic neurone As a result dopamine builds up in the synapses which can lead to feelings of pleasure

Question 49

what is the effect of cannabinoids on synapse

Answer 49

Cannabinoids are compounds found in cannabis Cannabinoid receptors are located in the pre-synaptic membrane of neuromuscular junctions When a cannabinoid molecule binds to its specific receptor, it closes the calcium ion channels This leads to decreased muscle contraction There is currently research investigating whether cannabinoids could be an effective drug in treating multiple sclerosis (MS) MS is a disease that involves damage to the myelin sheaths of neurones. Sufferers struggle to control muscle contraction

Question 50

what is the effect of MDMA on synapses

Answer 50

MDMA stimulates the release of multiple neurotransmitters most notably, serotonin Serotonin can affect people in many ways including their mood, anxiety and sleep When an individual takes MDMA they may feel extreme euphoria and enhanced touch and bodily sensations

Question 51

what is the affect of nicotine

Answer 51

-heightened activity in cholinegric pathways in the brain -improve reaction times -stimulation of cholinergic neurons promote release of neurotransmitter in reward passages for the brain -release og glutamate -enhances the connections bwt sets of neurons and increase memory by strengthening these connections

Question 52

how is resting potential maintained - exam answer

Answer 52

-sodium-potassium pump operates by active transport using ATP -3Na+ out and 2K+ in -gated Na+ ion channel closed -K+ ion gated channel open- some K+diffuse back out -70 mV maintained

Question 53

what is occuring when the resting potential is 0mV

Answer 53

-equal disrubution of Na+ and k+ either side of the membrane