biopsychology- neurons and synaptic transmission

Question 1

neuron definition

Answer 1

the basic building blocks of the nervous system, neurons are nerve cells that processes and transmit messages through electrical and chemical signals

Question 2

sensory neurons definition

Answer 2

these carry messages from the PNS (peripheral nervous system) to the CNS. they have long dendrites and short axons

Question 3

relay neurons definition

Answer 3

these connect the sensory neurons to the motor or other relay neurons. they have short dendrites and short axons

Question 4

motor neurons definition

Answer 4

these connect the CNS to effectors such as muscles and glands. they have short dendrites and long axons

Question 5

sensory neuron function

Answer 5

-send information to the brain regarding the senses ( also known as afferent neurons)
-carry information from the peripheral nervous system to the central nervous system
-they keep the brain informed about the external and internal environment via processing information coming from eyes, ears, nose, skin and tongue
-can only transmit messages so are unipolar

Question 6

where does sensory neuron transmit information from and to

Answer 6

from peripheral nervous system to central nervous system

Question 7

structure of a sensory neuron

Answer 7

-long dendrites
-relatively short axons
-cell body is usually to the side of the cell

Question 8

motor neuron function

Answer 8

-carry signals from the central nervous system towards the organs, muscles and glands in the body
-in this respect there are efferent (as away from brain) neurons as they carry information away from CNS to PNS
-they can both transmit and receive messages, so are known as multipolar neurons

Question 9

where do motor neurons transmit information to and from

Answer 9

from CNS to PNS

Question 10

motor neurons structure

Answer 10

-short dendrites
-relatively long axons

Question 11

what is motor neuron known as if connected to a muscle

Answer 11

motor end plate

Question 12

relay neurons function

Answer 12

-known as interneurons as can take on the role of sensory and motor neurons in the nervous system
-connect sensory neurons to motor neurons
-they are based in the CNS ans carry signals/messages across this part of the nervous system
-can both transmit and recieve messages so are multipolar neurons

Question 13

relay neuron structure

Answer 13

-short axons
-short dendrites
-no mylein sheath

Question 14

synaptic transmission definition

Answer 14

the process by which neighboring neurons communicate with each other by sending chemical messages across the synapse that separates them apart

Question 15

neurotransmitter definition

Answer 15

brain chemicals released from synaptic vesicles that relay signals cross the synapse from one neuron to another. neurotransmitters can broadly be divided into those that perform and excitatory and inhibitory function

Question 16

how many neurons are there in the human nervous system

Answer 16

100 billion neurons

Question 17

what percentage of nervous system neurons are in the brain

Answer 17

80%

Question 18

how do neurons provide nervous system with primary means of communication

Answer 18

transmitting signals electrically and chemically

Question 19

neurons size

Answer 19

vary in size from less than 1mm to a metre long

Question 20

basic structure of a neuron

Answer 20

-cell body which includes a nucleus which contain genetic material of the cell
-branchlike structures called dendrites protrude from the cell body
-these carry nerve impulses form neighbouring neurons away from the body
-the axon carries impulses away from the cell body down the length of the neuron. the axon is covered in a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse
-the myelin sheath is segmented by gaps called nodes of raviner which speed up the transmission of impulse by forcing it to jump across gaps along the axon as if myelin sheath was continuous would slow down electrical impulse
-at the endo of the axon are the terminal buttons that communicate with the next neurone in the chain across a gap called the synapse

Question 21

motor neuron location

Answer 21

-cell bodies in CNS but long axons form part of PNS

Question 22

sensory neuron location

Answer 22

-located outside the CNS, in the PNS in clusters known as ganglia

Question 23

relay neuron location

Answer 23

make up 97% of neurones and most are found within the brain and visual system

Question 24

how does electrical transmission- the firing of a neuron

Answer 24

when a neuron is in a resting state inside of the cell is negatively charges compared to outside. when a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing action potential to occur. this creates an electrical impulse that travels down the axon towards the end of the neuron

Question 25

synaptic transmission - chemical transmission

Answer 25

-neurons communicate within groups known as neural networks.
each neuron is separated form the next by an extremely tiny gap called a synapse
-signals within neurons are transmitted electrically however, signals between neurons are transmitted chemically across the synapse
-when the electrical impulse reaches the end of the neuron (presynaptic terminal) it triggers release of neurotransmitters from tiny air sacs called synaptic vesicles

Question 26

what are neurotransmitters

Answer 26

chemicals that diffuse across the synapse to the next neuron in the chain

Question 27

what happens once neurotransmitter crosses the synapse

Answer 27

it is taken up by the postsynaptic receptor site on the dendrites of the next neuron (axons take signals to the synapse, dendrites take signals away). here, the chemical message is converted back into an electrical back into an electron impulse and the processes of transmission begins again in this other neuron

Question 28

travel direction of neurotransmitter

Answer 28

one-way. this is because neurotransmitters are released from the presynaptic neuron terminal and removed by postsynaptic neuron (receptor sites)

Question 29

types of neurotransmitter

Answer 29

-several dozen types of neurotransmitter have been identified in the brain (as well in the spinal cords and some glands). each neurotransmitter has its own specific molecular structure that fits perfectly into a postsynaptic receptor site, similar to a lock and key. neurotransmitters also have specialist functions. for instance acetylcholine is found at each point where a motor neuron meets a muscle, and upon its release, it will cause muscles to contract

Question 30

excitation and inhibition

Answer 30

neurotransmitters have either an excitatory or inhibitory effect on neighbouring neuron. for instance serotonin causes inhibition on the receiving neuron, resulting in neuron becoming more negatively charged and less likely to fire. in contrast adrenaline (an element of the stress response which is both a hormone and neurotransmitter) causes excitation of postsynaptic neuron by increasing positively charged making it more likely to fire

Question 31

what decides if a postsynaptic neuron fires

Answer 31

processes of summation

Question 32

summation

Answer 32

the excitatory and inhibitory influences are summed: is the net effect on the postsynaptic neuron is inhibitory than the postsynaptic neuron is less likely to fire. if the net effect is excitatory it is more likely to fire (the inside of the postsynaptic neuron momentarily becomes positively charged) once the electrical impulse is created it travels down the neuron
-therefore, the action potential of the postsynaptic neuron in only triggered if the sum of excitatory and inhibitory signals at any one time reaches the threshold