Neurons and Synaptic Transmission

Question 1

What is a neuron?

Answer 1

a cell that carries electrical impulses throughout the body

Question 2

What are dendrites? (3)

Answer 2

-Extensions at the beginning of a neuron that increase the surface area of the cell body
-receive info from other neurons and transmit electrical stimulation to the cell body
-covered with receptors

Question 3

What does the cell body (soma) do? (2)

Answer 3

-Produces proteins for the dendrites, axons and synaptic terminals
-Provides energy to trigger an action potential

Question 4

What is the axon?

Answer 4

-The main conducting unit of the neuron, capable of conveying electrical signals along distances that range from as short as 0.1 millimetre (in the brain) to as long as 1 metre (from the spinal cord to big toe).

Question 5

What do many axons do?

Answer 5

split into several branches, thereby conveying information to different targets

Question 6

What are many axons wrapped in?

Answer 6

protective myelin sheath (fatty tissue that speeds up transmission) which are broken at various points by the nodes of Ranvier.

Question 7

What is the axons job?

Answer 7

Transmits impulses to glands/muscles

Question 8

Where is the axon terminal located?

Answer 8

on one end of a neuron.

Question 9

What is the axon terminal? (2)

Answer 9

-the final part of a neuron to receive an electrical impulse
-is also the area where the impulse is converted to a chemical signal.

Question 10

What does the axon terminal do?

Answer 10

transfers information from its neuron into another neuron, though it does not come into physical contact with the other neuron.

Question 11

What are the features of a neuron?

Answer 11

-Dendrite
-Nucleus
-cell body
-Axon
-Myelin sheath
-Schwann cell
-Axon terminal
-Nodes of ranvier

Question 12

What are the types of neurons?

Answer 12

Sensory
relay
motor

Question 13

Where are sensory neurons found?

Answer 13

in the sensory organs associated with 5 different primary senses

Question 14

Where is the cell body found in a sensory neuron?

Answer 14

extends from the axon

Question 15

What does the cell body on a sensory neuron not have?

Answer 15

dendrites

Question 16

What does the cell body on a sensory neuron not have?

Answer 16

dendrites

Question 17

What are the features of a sensory neuron?

Answer 17

-Unipolar - cell body has one branch
-No dendrites on cell body
•Long dendrites connect to axon
• Myelin covers axon

Question 18

What are the features of a sensory neuron?

Answer 18

-Unipolar - cell body has one branch
-No dendrites on cell body
•Long dendrites connect to axon
• Myelin covers axon

Question 19

why she is sensory neuron unipolar?

Answer 19

because they only send a message one way

Question 20

What is the function of a sensory neuron?

Answer 20

Afferent nerve cell that carries sensory impulses from the sense organs (e.g. skin) to the CNS

Question 21

Where are relay neurons found?

Answer 21

brain and spinal chord

Question 22

What are the features of relay neurons?

Answer 22

-Multipolar - cell body has many branches (recives and sends info)
• Short dendrites
• Several dendrites
• Short axon
• No myelin on axon
• Entirely within the CNS

Question 23

What is the function of a relay neuron?

Answer 23

Enables sensory neurons and motor neurons to communicate

Question 24

What are the features of a motor neuron?

Answer 24

• Multipolar - cell body has many branches
• Short dendrites
• Several dendrites
• Long axon
• Myelin covers axon.

Question 25

What is the function of a motor neuron?

Answer 25

Efferent nerve cell that transmits nerve impulses from the CNS to muscles or glands

Question 26

What is synaptic transmission?

Answer 26

process by which neuron’s communicate with each other

Question 27

What is a synapse?

Answer 27

the junction between the axon of one neuron and the dendrites of another

Question 28

what are the main main features of a synapse?

Answer 28

vesicles in the axon terminal of the pre-synaptic neuron, which are sacs filled with neurotransmitters (chemical messengers).

Question 29

What is the synaptic gap/cleft?

Answer 29

the tiny gap between the two neurons

Question 30

What do the receptors on the dendrites post synaptic neuron do?

Answer 30

receive the neurotransmitters.

Question 31

What is the process of synaptic transmission?

Answer 31

-Info is passed down the axon of the pre-synaptic neuron as an electrical impulse known as an ap.
-ap reaches the axon terminal and triggers release of nt’s from vesicles.
-nt’s diffuse across the synaptic gap to carry the chemical signal from the presynaptic neuron to the post-synaptic neuron.
- nt’s bind to receptor sites on the post-‘ synaptic neuron.
-(summation) Stimulation of post-synaptic receptors can result in excitation or inhibition of the post-synaptic membrane.

Question 32

how does information travel at the synapse (synaptic transmission)

Answer 32

it travels in one direction

Question 33

What is only present in the pre synaptic membrane?

Answer 33

Vesicles containing neurotransmitters

Question 34

What is only present on the post synaptic membrane?

Answer 34

Receptors for neurotransmitters

Question 35

Why does info only travel in one direction at the synapse? (3)

Answer 35

-Vesicles containing neurotransmitters are only present in the pre-synaptic membrane.
-Receptors for neurotransmitters are only present on the post-synaptic membrane.
-During diffusion, neurotransmitters travel from levels of high concentration at the pre-synaptic membrane to levels of low concentration at the post-synaptic membrane.

Question 36

What happens once neuron transmitters bind to a receptor on the post synaptic neuron and what does this determine?

Answer 36

they have an excitatory or inhibitory effect.
-determines whether an action potential is fired from the neuron’s cell body, which then travels along its axon.

Question 37

What does excitation do? (3)

Answer 37

-Increases neural activation in the postsynaptic neuron (creates an excitatory post-synaptic potential).
• Makes the post-synaptic neuron more likely to fire.
• Increases the activity of other neurotransmitters.

Question 38

What are is an example of excitation neurotransmitters?

Answer 38

Glutamate
• Necessary for cognition, memory and learning.
• High levels can over-excite neurons until they die, causing brain disorders such as Alzheimer’s disease.

Question 39

What does inhibition do? (4)

Answer 39

-Decreases neural activation in the postsynaptic neuron (creates an inhibitory post-synaptic potential).
• Makes the post-synaptic neuron less likely to fire.
• Decreases the activity of other neurotransmitters.
-Balances periods of excitation.

Question 40

What does the firing of an action potential in the post synaptic neuron depend on?

Answer 40

the summation (combination) of all the excitatory post-synaptic potentials and inhibitory post-synaptic potentials.

Question 41

what happens if there is more excitation than inhibition?

Answer 41

a new action potential is created in the postsynaptic neuron.

Question 42

what happens if there is more inhibition than excitation?

Answer 42

new action potential is not created.

Question 43

What are the differences between neurotransmitters and hormones?

Answer 43

Neurotransmitters are produced within neurons and pass very quickly from one neuron, across the synaptic cleft, to another nearby neuron whereas hormones are secreted by glands and travel less quickly through the bloodstream to often quite distant target organs.