cell structure

What are the two main divisions of the nervous system?

Central nervous system (CNS) and peripheral nervous system (PNS)

What structures make up the central nervous system?

Brain and spinal cord

What structures make up the peripheral nervous system?

All nerves outside the CNS including somatic and autonomic systems

What are the two functional divisions of the PNS?

Afferent (sensory) and efferent (motor)

What does afferent mean in the nervous system?

Sensory information travelling toward the CNS

What does efferent mean in the nervous system?

Motor commands travelling away from the CNS

What is the basic functional unit of the nervous system?

Neuron

What property makes neurons unique compared to most cells?

They are electrically excitable

What are glial cells?

Non-neuronal cells that support and interact with neurons

What is another name for glial cells?

Neuroglia or glia

What are the four main structural regions of a neuron?

Cell body (soma), dendrites, axon, axon terminal

What is the primary function of the cell body (soma)?

Maintain cell and integrate incoming signals

Where is most of a neuron’s DNA located?

In the nucleus (nuclear DNA)

Where else can DNA be found in neurons?

In mitochondria (mitochondrial DNA)

What is the function of the nucleus in neurons?

Site of gene transcription (DNA to mRNA)

Why is genetics important in neuroscience?

Mutations can cause disease and are used to create transgenic models

What organelles are responsible for protein synthesis in neurons?

Rough ER, ribosomes, smooth ER, and Golgi apparatus

What is the role of the Golgi apparatus in neurons?

Modify, sort, and package proteins

What are the three main components of the neuronal cytoskeleton?

Microtubules, neurofilaments, microfilaments

Which cytoskeleton component is largest?

Microtubules

Which cytoskeleton component is smallest?

Microfilaments

What is the function of the cytoskeleton in neurons?

Maintains structure and transports cargo

What type of cargo is transported along the cytoskeleton?

Vesicles, proteins, organelles such as mitochondria

What protein stabilises microtubules in neurons?

Tau

What happens to tau in Alzheimer’s disease?

It becomes hyperphosphorylated and forms neurofibrillary tangles

What effect does tau dysfunction have on neurons?

Reduced microtubule stability and impaired transport

What is the function of mitochondria in neurons?

Produce ATP via cellular respiration

Why is ATP critical in neurons?

Maintains ion gradients and supports signalling

Why are neurons particularly vulnerable to mitochondrial dysfunction?

They have high energy demands

What is Huntington’s disease caused by?

A trinucleotide (CAG) repeat expansion

What protein is affected in Huntington’s disease?

Huntingtin protein (mutant mHtt)

Where does mutant huntingtin accumulate?

Primarily in the nucleus

What symptoms result from Huntington’s disease?

Motor, cognitive, and psychiatric symptoms

What are dendrites?

Branched extensions that receive input from other neurons

What is the main function of dendrites?

Receive synaptic input

How do dendrites increase their surface area?

Through branching and dendritic spines

What are dendritic spines?

Small protrusions that increase synaptic connections

Why are dendritic spines important for learning?

They are dynamically regulated and change with experience

What happens to dendritic spines in schizophrenia?

Reduced spine density

What is the consequence of reduced spine density?

Reduced synaptic input and cognitive deficits

What is the axon?

A long projection that transmits signals away from the cell body

What is the primary function of the axon?

Propagate action potentials

How many axons does a typical neuron have?

One

What are axon collaterals?

Branches of the axon

What is myelin?

A lipid-rich insulating sheath around axons

What is the function of myelin?

Increase speed of signal conduction

What is axonal transport?

Movement of materials along the axon

What is anterograde transport?

Movement from soma to axon terminal

What is retrograde transport?

Movement from axon terminal back to soma

Which protein is involved in anterograde transport?

Kinesin

What structure do motor proteins move along?

Microtubules

What disease is associated with axonal transport defects?

Charcot-Marie-Tooth disease

What type of damage occurs in CMT type 2?

Axonal degeneration

What is the axon terminal?

The end of the axon where communication occurs

What is the function of the axon terminal?

Release neurotransmitters

What are synaptic vesicles?

Membrane-bound structures containing neurotransmitters

What is the synaptic cleft?

The gap between two communicating cells

What happens when neurotransmitters are released?

They bind to receptors on the postsynaptic cell

What is the postsynaptic density?

A protein-rich region containing receptors

Why are mitochondria abundant in axon terminals?

High ATP demand for neurotransmission

What type of signalling occurs within neurons?

Electrical

What type of signalling occurs between neurons?

Chemical

What does botulinum toxin do at synapses?

Blocks neurotransmitter release causing paralysis

What is neuronal diversity?

Variation in shape and function of neurons

Name three neuron types based on structure

Unipolar, bipolar, multipolar

What is grey matter?

Regions rich in neuronal cell bodies

What is white matter?

Regions rich in myelinated axons

What is a nucleus in the CNS?

A group of neuronal cell bodies

What is a ganglion in the PNS?

A group of neuronal cell bodies

What is a tract?

A bundle of axons in the CNS

What is a nerve?

A bundle of axons in the PNS

What makes neurons unique in terms of lifespan?

They are postmitotic and long-lived

What does postmitotic mean?

They do not divide after development

What is neural plasticity?

Ability to change structure and function

Why do neurons have high energy demands?

Continuous signalling and ion gradient maintenance

What are glial cells traditionally thought to do?

Act as glue holding neurons together

Why is this view incorrect?

They have many active and essential roles

What is the approximate ratio of glia to neurons?

About 1:1

What are ependymal cells?

Ciliated glial cells lining ventricles

What is the function of ependymal cells?

Produce and circulate cerebrospinal fluid (CSF)

What is CSF?

Cerebrospinal fluid that cushions and supports the brain

What functions does CSF perform?

Shock absorption, buoyancy, transport, homeostasis

What is hydrocephalus?

Accumulation of CSF causing increased pressure

What causes hydrocephalus at the cellular level?

Dysfunction of ependymal cells and cilia

What are astrocytes?

CNS glial cells with many support functions

What is the tripartite synapse?

Interaction between neuron, astrocyte, and synapse

What roles do astrocytes play?

Support, neurotransmitter recycling, metabolic regulation

What is reactive astrogliosis?

Increase in astrocyte number or change in morphology after injury

What disease is associated with astrocyte dysfunction?

Epilepsy

What are satellite cells?

Glial cells surrounding neuron cell bodies in the PNS

What is the function of satellite cells?

Support and modulate sensory neurons

What role do satellite cells play in pain?

Modulate pain signalling

What are oligodendrocytes?

CNS glial cells that produce myelin

What are Schwann cells?

PNS glial cells that produce myelin

What are nodes of Ranvier?

Gaps in myelin sheath

What type of conduction occurs at nodes of Ranvier?

Saltatory conduction

Why does myelin increase conduction speed?

Action potentials jump between nodes

What is multiple sclerosis?

Demyelinating disease of the CNS

What happens during demyelination?

Loss of myelin slows or blocks signal transmission

What are microglia?

Immune cells of the CNS