Lecture 5/6 - Cells of the nervous system

Like all organs in the body, the nervous system is composed of numerous WHAT

cells

We can infer their function by their WHAT, WHAT and their WHAT

We can infer their function by their LOCATION, SHAPE and their PARTS

How to visualize cells:

• WHAT

• Make WHAT

• WHAT it to reveal features

How to visualize cells:

• Fixed tissue

• Make THIN SLICES

• Stain it to reveal features

Fixation of tissue consists of two steps:

1. WHAT of normal life WHAT in the tissue (WHAT)

2. WHAT of the structure of the tissue (WHAT)

Fixation of tissue consists of two steps:

1. CESSATION of normal life FUNCTIONS in the tissue (KILLING)

2. STABILIZATION of the structure of the tissue (PRESERVATION)

Physiological cells:

• WHAT

Physiological cells:

• Unfixed tissue (live)

What basic elements are present in all cells

• Golgi body

• Lysosomes

• Cell membrane

• Mitochondria

• Endoplasmic reticulum

• Nucleus

• Nuclear membrane

What basic elements are present in neurons

• Axons

• Dendrites

• Dendritic spines

Cells are enclosed in a WHAT

Membrane

It forms a boundary between the WHAT and WHAT

It forms a boundary between the OTSIDE and INSIDE

Inside and outside of a cell is WHAT

Salt fluid

Fluid inside = WHAT

Cytoplasm

Fluid outside = WHAT

Extracellular fluid

Membrane is a WHAT barrier; only WHAT molecules and some WHAT can get through without aid

Membrane is a SMEI-PERMEABLE barrier; only FAT-SOLUBLE molecules and some GASES can get through without aid

The membrane contains WHAT that act as WHAT through which stuff (eg, ions) can (selectively) pass WHERE or WHERE of the cell

The membrane contains PROTEINS that act as CHANNELS through which stuff (eg, ions) can (selectively) pass INTO or OUT of the cell

Phospholipid:

• Head = WHAT

• Tail = WHAT

Phospholipid:

• Head = HYDROPHILIC (loves water)

• Tail = HYDROPHOBIC (fears water)

The phospholipid bilayer separates the two WHAT

Aqueous environments

Lipid character of bilayer limits WHAT across the cell membrane

Lipid character of bilayer limits DIFFUSION of WATER-SOLUBLE molecules across the cell membrane

The plasma-membranes hydrophobic (water fearing) interior prevents free (inward and outward) diffusion of WHAT (and other WHAT) substances, thus it constitutes as a WHAT membrane

The plasma-membranes hydrophobic (water fearing) interior prevents free (inward and outward) diffusion of CHARGED (and other HYDROPHILIC (water loving)) substances, thus it constitutes as a SEMI-PERMEABLE membrane

What are hydrophilic molecules

• Small inorganic ions (Na+, Ca2+, Cl-)

• Charged proteins

What are hydrophobic molecules

• Lipid-soluble hormones (NO, O2, CO2)

• Uncharged proteins

Golgi complex

Packaging and processing of proteins

Mitochondria

Converts sugar and oxygen into ENERGY, energy is in the form of adenosine triphosphate (ATP)

Endoplasmic reticulum and ribosomes

Site of protein synthesis

Nucleus:

• WHAT structure inside the cell body

• contain WHAT

Nucleus:

• MEMBRANE-BOUND structure inside the cell body

• contain DNA

DNA contains WHAT

Genetic information

DNA is the blueprint for all the WHAT a cell can make

protein

All neurons are interconnected to form WHAT

Coherent networks

How does information flow in a neuron

• input zone

• conduction zone

• Output zone

What are three neurons

• Multipolar

• Bipolar

• Monopolar

Neurons are the WHAT units of the brain

Information processing

Neurons play many roles:

• Receive information from WHAT receptors

• Relay information to other WHAT and WHAT

• Control WHAT → behaviour

• Releases WHAT

• Regulate local WHAT

• Hold instructions for WHAT → memories

• Regulate WHAT and WHAT

• Regulates WHAT → homeostasis

Neurons play many roles:

• Receive information from SENSORY receptors

• Relay information to other NEURONS and CELLS

• Control MUSCLES → behaviour

• Releases HORMONES

• Regulate local BLOOD FLOw

• Hold instructions for BEHAVIOR → memories

• Regulate THOUGHTS and EMOTIONS

• Regulates UNCONSCIOUS PHYSIOLOGY → homeostasis

Core region of the neuron called the WHAT or WHAT

Core region of the neuron called the CELL BODY or SOMA

Branching extensions of the neuron called WHAT, collect information from WHAT

Branching extensions of the neuron called DENDRITES, collect information from OTHER CELLS

The neurons main root is the WHAT, which carries messaged to other WHAT

The neurons main root is the AXON, which carries messaged to other NEURONS

neurons only has HOW MANY axon that can branch, most neurons have many WHAT

neurons only has ONE axon that can branch, most neurons have many DENDRITES

Neurons are the functional units of the WHAT, they WHAT, WHAT, WHAT and WHAT information

Neurons are the functional units of the CNS, they RECEIVE, PROCESS, INTEGRATE and RELAY information

The axon starts at the WHAT

Axon hillock (right under the cell body)

The axon can branch into WHAT

Axon collaterals

Near the end of the axon are branched called WHAT

Teleodendria

Each teleodendria ends with a WHAT aka WHAT or WHAT

Each teleodendria ends with a PRE-SYNAPTIC TERMINAL aka BUTTON or BOUTTON

Button is close to WHAT of the next neuron

Dendritic spine

The teleodendria and the dendritic spine don’t WHAT there is a small gap called the WHAT

The teleodendria and the dendritic spine don’t TOUCH there is a small gap called the SYNAPSE

HOW MANY primary dendrites per cell

1-20

Each dendrites WHAT numerous times

Branches

This branching increases the WHAT of the cell

Surface area

Each dendrite is covered in WHAT taht also increases the WHAT

Each dendrite is covered in DENDRITIC SPINES taht also increases the SURFACE AREA

Dendrites collect information from other WHAT

cells

More surface area means more WHAT

Information exchange

What are the three types of neurons

• Sensory neurons

• Interneurons (majority)

• Motor neurons

What do sensory neurons do

Input information to CNS

What are the two types of interneurons

• Local - projects WITHIN the brain (receive and project info in the same brain region)

• Projection - Projects BETWEEN the brain regions (receive and project info to other brain regions)

What do motor neurons do

Output signals from the CNS to the muscles

Morphology of a neuron can tell us about its WHAT

Function

The size of a neuron:

• Neurons with long extension likely WHAT

• Nuerons with short extensions likely WHAT

The size of a neuron:

• Neurons with long extension likely RELAY INFORMATION

• Nuerons with short extensions likely ENGAGE IN LOCAL PROCESSING

Shape of a neuron:

• Complex dendrites integrate information from a WHAT

• Simple dendrites integrate on a much smaller scale act as WHAT

Shape of a neuron:

• Complex dendrites integrate information from a WIDE AREA

• Simple dendrites integrate on a much smaller scale act as RELAYS

Sensory neurons:

• WHAT relay cells

• One simple WHAT

Dendrites can be:

• WHAT

• WHAT

Can be among the WHAT in the body

Sensory neurons:

• EFFICIENT relay cells

• One simple DENDRITE

Dendrites can be:

• SMALL (eg. bipolar cells in retina)

• LARGE (eg. sensory neurons for skin)

Can be among the LARGEST in the body

Technically every neuron between a sensory neuron and a motor neuron is a WHAT

Technically every neuron between a sensory neuron and a motor neuron is a INTERNEURON

What are the two types of interneurons

• Long-distance projection

• Local projection

What are the three most commonly studied interneurons:

• WHAT

• WHAT

• WHAT

What are the three most commonly studied interneurons:

• Stellate cell

• Pyramidal cell

• Purkinje cell

Stellate (star-shaped) cell:

• WHAT

• Many short WHAT extend around the WHAT

• Short WHAT

Stellate (star-shaped) cell:

• SMALL

• Many short DENDRITES extend around the CELL BODY

• Short AXON

Pyramidal cell:

• Has a long WHAT

• A pyramid-shaped WHAT

• two sets of WHAT, WHAT and WHAT

• Carries information from the WHAT to the rest of the WHAT and WHAT

Pyramidal cell:

• Has a long AXON

• A pyramid-shaped CELL BODY

• two sets of DENDRITES, APICAL and BASAL

• Carries information from the CORTEX to the rest of the BRAIN and SPINAL CORD

Purkinje cell:

• Extremely branched WHAT that form a WHAT shape

• Carried information from the WHAT to the rest of the WHAT and WHAT

Purkinje cell:

• Extremely branched DENDRITES that form a FAN shape

• Carried information from the CEREBELLUM to the rest of the BRAIN and SPINAL CORD

Motor neurons are located in the WHAT, WHAT and WHAT

Motor neurons are located in the CEREBRAL CORTEX, BRAINSTEM and SPINAL CORD

In motor neurons bushy dendrites collect WHAT

In motor neurons bushy dendrites collect INFORMATION

Motor neurons are usually have large WHAT and WHAT that connects to WHAT

Motor neurons are usually have large CELL BODY and AXON that connects to MUSCLES

All WHAT (outgoing) neural information must pass through WHAT to reach muscles

All EFFERENT (outgoing) neural information must pass through MORTOR NEURONS to reach muscles

Sensory neurons collect WHAT (WHAT) information from the body and connect to WHAT that process the information and pass it on to WHAT neurons

Sensory neurons collect AFFERENT (INCOMING) information from the body and connect to INTERNEURONS that process the information and pass it on to MOTOR neurons

The motor neurons efferent connections move WHAT and produce WHAT

The motor neurons efferent connections move MUCLES and produce BAHAVIOR

These three organizational aspects of neurons are this features of neuronal networks:

• WHAT

• WHAT

• WHAT

These three organizational aspects of neurons are this features of neuronal networks:

• INPUT

• ASSOCIATION

• OUTPUT

Information feeds into the WHAT

Dendrites

Dendrites feed information into the WHAT

Cell body

Information is relayed down the WHAT which branches at its ends

Axon

A neuron has thousands of WHAT (both WHAT and WHAT) but only a single WHAT

A neuron has thousands of INPUTS (both POSITIVE and NEGATIVE) but only a single AXON

The neuron processes and integrates the WHAT and (potentially) WHAT this information onwards depending on the average or summary of the WHAT

The neuron processes and integrates the INPUTS and (potentially) RELAYS this information onwards depending on the average or summary of the INPUTS

The axon terminals of the WHAT neuron come close to but do NOT contact the WHAT of the next WHAT cell forming a gap called a WHAT

The axon terminals of the PRE-SYNAPTIC neuron come close to but do NOT contact the DENDRITES of the next (POST-SYNAPTIC) cell forming a gap called a SYNAPSE

Terminal contains WHAT (WHAT and WHAT) that are released into the next cell to relay the signal

Terminal contains CHEMICALS (NEUROTRANSMITTERS and NEUROPEPTIDES) that are released into the next cell to relay the signal

In general the chemical synapse is WHAT: Only the WHAT cell influences the WHAT cell

In general the chemical synapse is UNIDIRECTIONAL: Only the PRE-SYNAPTIC cell influences the POST-SYNAPTIC cell

Most connections between neurons in an area are WHAT

local

Local interneurons

processing information

Axon collaterals can WHAT to regulate activity:

• Typically regulate level of its own WHAT

• turn off cell once it has WHAT its message

Axon collaterals can FEEDBACK to regulate activity:

• Typically regulate level of its own ACTIVITY

• turn off cell once it has SENT its message

Some cells send information to or receive information from other WHAT but most connections are WHAT

Some cells send information to or receive information from other BRAIN REGIONS but most connections are LOCAL

Signal from a pre-synaptic neuron either WHAT or WHAT the next post-synaptic neuron

Signal from a pre-synaptic neuron either EXCITES or INHIBITS the next post-synaptic neuron

The receiving neuron integrates all its various WHAT and determines the response:

• If there is more excitation the neuron will WHAT the signal (yes) (++,---,+++)

• If there is more inhibition the neuron will WHAT (no) (----, +++, ----)

The receiving neuron integrates all its various INPUTS and determines the response:

• If there is more excitation the neuron will RELAY the signal (yes) (++,---,+++)

• If there is more inhibition the neuron will REMAIN SILENT (no) (----, +++, ----)

What are the two views on how neurons code for behavior

1. Each neuron codes for a SPECIFIC aspect of behaviour

2. Neurons work together in COMPLEX NETWORKS to code for specific aspects of behavior (loss of one or more neurons would not effect behavior, network can still function)

Science favours which view

The network hypothesis

• Ears on either side of a moth are connected to WHAT on opposite sides of the body

• Side closest to a bat is WHAT the most

• This affects the WHICH wing to steer the moth away form the from the bat

• Ears on either side of a moth are connected to WING MUSCLES on opposite sides of the body

• Side closest to a bat is ACTIVATED the most

• This affects the OPPOSITE wing to steer the moth away form the from the bat

Neurons are not WHAT but change WHAT constantly:

• rewire, make new WHAT

Neurons are not STATIC ENTITIES but change SHAPE constantly:

• rewire, make new CONNECTIONS

Neurons are WHAT

Post-mitotic (can’t under go mitosis)

Most neurons are not WHAT this means most neurons live with you throughout your whole life

Most neurons are not REPLACED this means most neurons live with you throughout your whole life

Glial cells have between a WHAT to WHAT ratio with neurons 

Glial cells have between a 1:1 to 10:1 ratio with neurons (way more glial cells)

Like neurons, glial cells have multiple WHAT 

forms 

Like neurons, glial cells play multiple WHAT

Roles

Unlike neurons, glial cells are constantly WHAT throughout life 

Unlike neurons, glial cells are constantly RENEWED throughout life 

They play the “WHAT” role in the nervous system 

They play the “SUPPORTING ACTOR” role in the nervous system (neurons are still the main/ most important but need glial cells to help) 

What are the six types of glia cells and what nervous system are they apart of 

• Ependymal cells (CNS) 

• Microglia (CNS) 

• Astrocytes (CNS) 

• Oligodendrocytes (CNS) 

• Satellite glial cells (PNS) 

• Schwann Cells (PNS) 

Ependymal cells

• Line the VENTRICLES 

• Help generate CEREBROSPINAL FLUID (CSF) and create/assist the FLOW of the fluid

Microglia cells

• IMMUNE SYSTEM and REPAIR in the CNS

• Clear dead cells (including apoptotic neurons) 

• Activated by injury and toxins 

• Similar functions as WHITE blood cell (monocytes) and macrophages 

Extensive and essential WHAT between microglia and neurons, particularly in the WHAT 

Extensive and essential COMMUNICATION between microglia and neurons, particularly in the SYNAPSE  

Astroglia (Astrocyte)

• STAR shape 

• Provide STRUCTURAL support 

• Convey NUTRIENTS between BLOOD VESSELS and neurons 

• Regulate BLOOD flow 

• Part of the blood brain barrier 

• Can play a role in HEALING the brain after damage 

Satellite glial cells

• Small cells that SURROUND neurons’ CELL BODIES located in the AUTONOMIC nervous system (ie. PNS) 

• They resemble the ASTROCYTES of the CNS and assist in regulating the EXTERNAL chemical environment 

• Very sensitive to INJURY and may exacerbate (increase) PATHOLOGICAL pain