1. Everything you need to know about a neuron
By: Akhil , David, Poom

2. Outline Introduction Structure of neuron Function of neuron
Psychology connection
Cool facts

3. Introduction

4. What is a neuron?
A neuron is a cell that is able to transmit messages around the body using chemical and electrical signals.
Found in most animals
Except sponges and other animals
Are Neurons???

5. Nervous system
The neuron is a core component of the nervous system and is found all over the body in neural networks.
Our brain is essentially full of neurons.

6. Structure of neuron

7. Structure A neuron consists of: A cell body Also called the soma
Dendrites
Axon
Myelin Sheath
Casparian strip
Nodes of Ranvier
Neuron is classified by having synapses and having electric conducting capabilities

8. Soma
Central part of neuron
Contains nucleus
Protein synthesis

9. Dendrites Thin structures that arise from the cell body
Neuron can contain multiple dendrites
Tend to branch out, forming complex webs
Used for reception of signals from outside

10. Axon Long slender-like structure
Conducts electrical impulses and propagates it
Cell body can have only one axon
Can be very long

11. Axon Area that axon leaves the cell body is called the axon hillock.
This area has the highest density of voltage dependent channels and thus are easiest to excite

12. Myelin sheath Electrically insulating material surrounding axon
Protects both the neuron and mitigates loss of electrical signal
Production of this is called myelination.
Schwann cells form the sheath
Nodes of Ranvier are small areas between Schwann cells on the axon
Neurons with myelin transmit messages faster than ones that don’t

13. Synapse
Gap between the axon of one neuron to usually the dendrite of another
Synapses can be excitatory or inhibitory if they increase or decrease the activity in the target neuron, respectively.

14. Glia Support cells of nervous systems Smaller than neurons
More abundant in brain and body than neuron

15. Types of Glia Astrocytes:
Wrap around the terminals of presynaptic terminals to take the chemicals released by the axon
Release the chemicals to be reused
Remove waste material of dead neurons

16. Types of Glia Oligodendrocytes: Occur in brain and spinal cord
Build myelin sheath
Make saltatory conduction possible

17. Post/Pre Synaptic neuron
Postsynaptic neuron is what releases neurotransmitters
Presynaptic neuron has the receptors that accept the neurotransmitters

18. Exceptions Some neurons don’t have dendrites, others don’t have axons
Others may have an axon-axon link, while others may have a dendrite-dendrite link

19. Types of neurons Two classes: Type 1 with long axons
Type 2 with short axons
Different functions:
Afferent or sensory neurons convey messages from tissues and organs to CNS
Efferent or motor neurons transmit messages from CNS to effector cells
Interneurons send messages between efferent and afferent neurons. Mostly in the CNS

20. Functionality of neuron

21. Synapse
Electric impulses are released by axons and accepted by dendrites
If a neuron is excited enough by a stimulus, it reaches a stage called the action potential. At this point it is ready to fire

23. Synapse
Once it fires, it sends the signal down the axon and to the next neuron.
The process of transfer of signal is called saltatory conduction that involves signal transmission on an axon with myelin

24. Synapse Has both electric and chemical characteristics
Like all cells, neurons have a lipid bilayer plasma membrane filled with electrically active proteins
These ion channels can be both activated by chemicals or even through a voltage difference between sides of the membrane through flooding of ions through the channels.
Once this voltage difference is obtained, the action potential is reached and the neuron fires.

25. Synapse
This electrical and chemical process is called neurotransmission
This process, that triggers the release of neurotransmitters, is called action potential
It essentially takes advantage of the electric excitability of the neuron
Also known as depolarization

26. Action on other neurons
A neuron affects other neurons by releasing a neurotransmitter that binds to chemical receptors.
The effect is determined by the neurotransmitter that can be seen as a key, where the lock is the receptor on the postsynaptic cell.

27. All or none principle A neuron either fires or it doesn’t
Bigger stimuli either affect more neurons in an area or increase the frequency but not the strength of signal

28. Neurological disorders
Alzheimers disease:
Neurodegenerative disease
Cognitive deterioration
Short-term memory loss
Further impairment can be significant in terms of memory, recognition, and decision-making

29. Neurological disorders
Parkinson’s disease:
CNS degeneration
Impairs motor skills and speech
Can lead to cognitive dysfunction
Demyelination:
Loss or absence of myelin in neurons
Detrimental as signals can be permanently lost which can lead to significant problems

30. Neurogenesis
Nerve regeneration or neurogenesis can sometimes occur in the adult vertebrate brain
Recent studies however show that majority of our neurons are before birth without replacement
It is possible for peripheral axons to regenerate if injured

31. Concept of reuptake
Reuptake is the process of reabsorption of neurotransmitters that have transmitted the neural impulse.
Essentially, recycling of neurotransmitters
Also regulates how long the neurotransmitter is in the neural cleft, ergo, effecting the duration of the signal.

32. Neurotransmitters

33. Neurotransmitters
Chemicals that transmit a message from a neuron to a target cell across a synapse
They are released into the synaptic cleft where they attach to receptors on the postsynaptic neuron

34. Neurotransmitters Can be characterized as:
Excitatory: Increase the rate of firing of neuron
Inhibitory: Reduce the rate of firing or transmission of message
In other words, a neuron’s capability depends on the neurotransmitter and the receptor that it works upon

35. Neurotransmitters GABA:
Found in majority of inhibitory synapses in brain
Prominent in sedatives/tranquilizers
Dopamine:
Regulation of motor behavior
Control of motivation and emotional arousal
Critical in the reward system
Deficient in Parkinson’s patients
Excessive in Schizophrenia patients

36. Neurotransmitters Serotonin:
Regulates appetite, sleep, memory, learning, temperature, mood, behavior, muscle contraction, and functionality of cardiovascular and endocrine system.
Known to have an effect on extreme emotions: depression or euphoria

37. Psychology connection

38. Connections Neurons are the backbone of feelings:
Example: people consume alcohol for anti-depression as it increases the action potential of neurons that pertain to depression and thus reduce depression
Other neurotransmitters like serotonin also affect emotion

39. Connections Neurons are the mediators between brain and body
Neurological disorders significantly affect cognitive abilities of individuals.
Open to discussion :)

40. Cool facts

41. Cool Facts
Average number of neurons in a human brain: 100 billion neurons
Rate of neuron growth during fetal development in utero = 250,000 neurons/minute
Diameter of a neuron = 4 to 100 microns
The number of ways information travels in the human brain is greater than the number of stars in the universe

42. Cool Facts
Each of the 100 Billion neurons in the brain have on average 7000 synaptic connections to other neurons.
There are as many neurons in the human brain as stars in the Milky Way
Length of giraffe afferent axon = 15 feet
Velocity of signal of a neuron: mph

43. Thank you for watching!