Organisation of the Nervous System

Flashcards covering key definitions and concepts related to the organization of the nervous system, including its divisions, major structures, cell types, and historical milestones, based on the provided lecture notes.

Nervous System Divisions

Includes the brain, spinal cord, and peripheral nervous system.

Sympathetic Nervous System

A division of the autonomic nervous system responsible for 'Fight or Flight' responses, characterized by thoraco-lumbar outflow.

Parasympathetic Nervous System

A division of the autonomic nervous system responsible for 'Rest and Digest' functions, characterized by cranio-sacral outflow.

Neuroglia (CNS)

Main cell types in the Central Nervous System including ependymal cells, oligodendrocytes, astrocytes, and microglia.

Neuroglia (PNS)

Main cell types in the Peripheral Nervous System including satellite cells and Schwann cells.

Neuron

The basic structural and functional unit of the nervous system, responsible for transmitting electrical and chemical signals.

Myelin

A fatty sheath that insulates axons, increasing the speed of nerve impulse transmission.

Synapse

The junction between two neurons where electrical or chemical signals are transmitted from one neuron to another.

Broca's Area

A region in the left frontal lobe of the brain crucial for speech production.

Phineas Gage

A railway worker whose personality and character dramatically changed after a tamping iron passed through his frontal lobe in 1848, providing early insights into brain localization.

Phrenology

An 1800s theory proposed by Franz Joseph Gall, suggesting that brain regions are specialized and their growth could be observed on the skull surface.

Cerebral Cortex

The outermost layer of the cerebrum, responsible for higher brain functions like thought and voluntary action.

Gyrus

A ridge or fold on the surface of the cerebral cortex.

Sulcus

A groove or furrow on the surface of the cerebral cortex.

Brainstem

Connects the cerebrum and cerebellum to the spinal cord, responsible for vital functions such as breathing and heart rate. Comprises midbrain, pons, and medulla.

Cerebellum

Located at the back of the brain, primarily involved in motor control, coordination, and balance.

Spinal Cord

A long, thin, tubular bundle of nervous tissue and support cells that extends from the brainstem to the lumbar region, transmitting signals between the brain and the rest of the body.

Grey Matter

Composed primarily of neuron cell bodies, dendrites, and unmyelinated axons, involved in processing information.

White Matter

Composed primarily of myelinated axons, connecting different regions of grey matter and facilitating communication.

Ventricles

Fluid-filled cavities within the brain that produce and circulate cerebrospinal fluid (CSF).

Frontal Lobe

Responsible for personality characteristics, decision-making, movement, smell recognition, and speech (Broca's area).

Parietal Lobe

Processes sensory information, involved in identifying objects, spatial awareness, pain/touch sensation, and understanding speech (Wernicke’s area).

Occipital Lobe

Primarily responsible for processing visual information.

Temporal Lobe

Involved in short-term memory, speech, musical rhythm, and smell recognition.

Corpus Callosum

A large bundle of nerve fibers connecting the two cerebral hemispheres, allowing them to communicate.

Thalamus

A major relay station for sensory information reaching the cerebral cortex.

Hypothalamus

Regulates vital bodily functions such as temperature, hunger, thirst, and hormone release.

Medulla Oblongata

The lowest part of the brainstem, controlling essential involuntary functions like heart rate and breathing.

Cerebrospinal Fluid (CSF)

A clear fluid that cushions the brain and spinal cord, absorbs shocks, and facilitates nutrient and waste exchange. Produced by the choroid plexus and ependymal cells.

Central Nervous System (CNS)

Consists of the brain and spinal cord.

Peripheral Nervous System (PNS)

Encompasses all nervous tissue outside the brain and spinal cord, including cranial nerves, spinal nerves, ganglia, enteric plexuses, and sensory receptors.

Somatic Nervous System

A division of the PNS responsible for voluntary control of skeletal muscles and relaying sensory information from the body to the CNS.

Autonomic Nervous System (ANS)

A division of the PNS that controls involuntary visceral functions, maintaining the body's internal environment (homeostasis).

Homeostasis

The ability of an organism to maintain stable internal conditions despite changes in the external environment, controlled by the ANS.

Rostral

Directional term meaning towards the front or head end.

Caudal

Directional term meaning towards the tail or posterior end.

Dorsal

Directional term meaning towards the back (or top in the brain).

Ventral

Directional term meaning towards the belly (or bottom in the brain).

What is the main function of the nervous system?

To take in information from the environment interact with it and make predictions.

What is the brain often described as?

A prediction machine that forecasts opportunities threats and future events.

Can life exist without a nervous system?

Yes—e.g.amoebae live without one, but they can’t perform complex tasks like playing tennis

How many neurones does the human brain have?

~86 billion.

Are neurones replaced regularly like skin or blood cells?

No you’re born with them and they last a lifetime (unless damaged).

Why are neurones fragile?

They are long-livedform complex connections, and can’t easily be replaced if lost

What is the challenge with growing new neurones in therapy?

New neurones struggle to integrate into existing pathways.

Why is it difficult to get drugs into the brain?

Protective mechanisms (like the blood-brain barrier) restrict entry.

What consistency does the brain have in real life?

Very soft—like a pudding; it cannot hold its shape without CSF and meninges.

What is CSF and why is it important?

Cerebrospinal fluid—surrounds and cushions the brain helping it float.

What is the earliest known written reference to the brain?

Ancient Egypt (~4000 years ago).

What was phrenology?

A pseudoscience claiming skull bumps reflect abilities or traits.

Why is phrenology important historically?

It introduced the idea of brain regions having specialized functions.

What is Broca’s area responsible for?

Producing spoken language.

Do brain regions change shape when you learn new skills?

No the number of neurones stays constant, but their connections change

What is the prefrontal cortex responsible for?

Forward thinking planning decision-making, and goal-directed behavior.

Who was Phineas Gage and why is he important?

A railroad worker who survived a frontal lobe injury; his personality changed dramatically showing the link between brain damage and behavior.

What happened to Gage’s behavior after his injury?

He became unreliable addicted to alcohol/gambling neglectful of family and had a personality shift.

What happens if you damage or remove part of the brain?

Function is lost; brain operates under natural laws (like a machine).

What did Darwin’s 'On the Origin of Species' contribute to neurobiology?

Opened the door to comparative biology allowing animal models for brain and drug research.

What are neurones?

Excitable cells that send electrical and chemical messages allowing complex functions.

Why are neurones vulnerable?

They must last a lifetime and can be very long (up to 1.5 m) making them fragile.

What role do glial cells play?

They support nourish and protect neurones—like cookie dough holding chocolate chips.

How many glial cells exist compared to neurones?

About 10 times as many—around a trillion in total.

Which glial cells form the blood-brain barrier?

Astrocytes.

Why don’t neurones contact the blood supply directly?

Astrocytes form a barrier so substances must cross glia to reach neurones.

Why is the blood-brain barrier a challenge for pharmacology?

It prevents many drugs in the blood from reaching neurones.

Which glial cells respond to infection and inflammation?

Microglia.

Which cells produce cerebrospinal fluid (CSF)?

Ependymal cells in the ventricles.

What are the three functions of ependymal cells?

1) Produce CSF 2) Form a barrier to prevent CSF leakage 3) Move CSF with cilia to maintain flow.

Why is CSF important?

It cushions the brain provides nutrients and removes waste.

What is myelin?

A fatty insulating layer around axons that speeds up electrical signal transmission.

Which cells produce myelin in the CNS?

Oligodendrocytes.

Which cells produce myelin in the PNS?

Schwann cells.

Why is myelin important for neurone function?

It allows long axons to transmit signals quickly (needed for fast actions like running or playing tennis).

Can neurones transmit signals without myelin?

Yes but transmission is much slower.

What would happen if long axons had no myelin?

Signal transmission would take too long making movement (e.g. walking or running) very slow and inefficient.

Are glial cells and microglial cells the same?

No. Glial cells are the broad category of support cells and microglia are one specific type of glial cell.

What are the main types of glial cells?

Astrocytes oligodendrocytes Schwann cells ependymal cells and microglia.

What is the role of astrocytes?

They support neurones regulate the extracellular environment and form the blood-brain barrier.

What is the role of oligodendrocytes?

They produce myelin in the central nervous system (CNS).

What is the role of Schwann cells?

They produce myelin in the peripheral nervous system (PNS).

What is the role of ependymal cells?

They line the ventricles produce cerebrospinal fluid (CSF), create a barrier, and move CSF with cilia.

What is the role of microglia?

They act as immune cells of the CNS responding to infection injury and inflammation.

Which glial cells are involved in forming the blood-brain barrier?

Astrocytes.

Which glial cells are involved in producing myelin?

Oligodendrocytes (CNS) and Schwann cells (PNS).

Which glial cells are involved in CSF production?

Ependymal cells.

Which glial cells are involved in immune defense?

Microglia.

Basic Structure of a Neuron

Consists of a cell body (soma), dendrites (receive signals), an axon (transmits signals), and axon terminals (form synapses with other neurons).

When a neurone fires an action potentialwhere does the signal go?

Down the axon and into all of its branches, sending the message to all connected targets.

What is the axon hillock?

The start of the axon where action potentials are generated.

Where does a neurone generate its first electrical signals?

At the axon hillock/initial segment.

What are the nodes of Ranvier?

Gaps in the myelin sheath where action potentials are regenerated.