Lecture 1: Neurones and the Nervous System Flashcards
Monday 6th January 2025
What does the nervous system do?
1) Sensory system: Receives and interprets information about the internal and external environments of the body
2) Integrating system: Makes decisions about the information received.
3) Motor system: Organises and carries out actions. Conscious and unconscious control of information.
What parts are included in the sensory system?
Sense organs, sensory nerves, central sensory areas
What does the integration system include?
making decisions from sensory input and stored record of previous experience (memories)
What does the motor system include?
Motor neurones, central motor areas, all muscles and ducted glands of the body. These control movement both consciously and unconsciously.
What are the units of the nervous system ?
Neurones
Describe the Neuron doctrine (circa 1894)
1) The neuron is the structural and functional unit of the nervous system
2) Neurons are individual cells, which are not continuous to other neurons
3) The neuron has three parts: dendrites, soma (cell body) and axon
4) Conduction takes place in the direction from dendrites to soma, to the end arborisations of the axon
Is the golgi stain still in use and if so, what is it used for?
Yes, and it is used to visualise the morphology of individual neurones in the brain tissue. distinguishes individual neurones by only staining a small number.
Are neurones continuous to other neurones?
No, they are one individual cell
What are the 3 main parts of a neurone?
- Dendrites
- Soma (cell body)
- Axon
What resulted in the findings of the neurone doctrine?
Anatomical investigation
What do the end aborisations of the axon make contact with?
The end aborisations of the axon makes contact with tissues or other neurones.
What is the function of the dendrites?
To increase surface area and to receive inputs
What is the function of the axon?
To carry information over distances
What is the function of the myelin?
To coat the axon and improve conduction [the speed of]
What are nodes of ranvier
breaks in the myelin sheath
How should we classify neurones?
- Morphology (multipolar, unipolar etc)
- Interneurones vs principle neurones
- By the neurotransmitter that they release i.e. cholinergenic, glutamateric, GABAergic etc
What is one problem that is unique to neurones?
How to get material from the cell body to the terminals, where the neurotransmitter is released, particularly because neurones can be so long.
How is the problem of getting material from the body to the terminals resolved?
- Through Anterograde transport. Goes from the soma, down the axon, and to the terminals. Can be either rapid or slow (larger proteins or organelles). (kinesin)
- Through Retrograde transport. From terminals to soma (i.e worn out organelles for degradation). (dynactin + dynein)
Describe the mechanism of axonal transport
- Transport proteins utilise the microtubule network that’s found inside neurones.
- These transport proteins move with the microtubules. Polarity of the microtubules will allow proteins to move to their destination.
- Movement in both transport systems is powered by ATP.
What are glial cells?
non-neuronal cells in the nervous system that provide support, protection, and maintenance for neurons. They play crucial roles in structural support, insulation, nutrient supply, and immune defence. Unlike neurons, glial cells do not generate electrical impulses but are essential for overall brain and spinal cord function.
What are the different types of glial cells?
- Oligodendrocytes
- Astrocyte’s
- Microglial cells
- Ependymal Cells
What do Oligodendrocytes do?
- Produce the myelin sheath around CNS axons to enhance signal transmission.
- In the PNS, they produce Schwann cells
What do Astrocyte’s do?
- They play a supporting role
- They have neurotransmitter receptors to ‘mop’ them up
- They can release their own chemical messenger to influence other neurones
- They can engulf blood vessels in the brain
- They provide metabolic fuel for other neurones.
- They release gliotransmitters (ATP, glutamate, D-serine)
- They regulate ion and nutrient balance
- They maintain the blood-brain barrier.
What do Microglial cells do?
- They phagocytose dead cells
- They launch an immune response (surveillance cells)
What do Ependymal Cells do?
- Line the ventricles of the brain and central canal of the spinal cord.
- Produce and circulate cerebrospinal fluid (CSF).
Do we still have ganglia ?
Yes
What is the nervous system structure?
- Nerve nets -> Nerve rings -> Ganglia -> Fusion of
ganglia
Describe structures that make up the invertebrate ganglia
- Cell body
- Axon in tracts
- Ganglion sheath
- Neurophil (dense regions of nerve fibers devoid of cell bodies
) - axons in neuropil
Describe further nervous system development
- Fusion of ganglia
- Brain and nerve cord
- Vertebrates
encephalization
“We have lots of folds in our brain, but the brains of other species can be smooth”. Is this statement true?
Yes
“Humans have the highest “encephalisation quotient” (7-8): comparison
of human brain size relative to mammalian reference species (cat)”. Is this true?
Yes
“Brain size scales with body weight, with common anatomical features across species”. Is this true?
Yes
Describe the composition of the Verterbate Nervous System
- Made up of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
- The CNS consists of the brain and the spinal cord.
- The PNS consists of the Autonomic (involuntary) Nervous System and the Somatic (voluntary) Nervous System.
-
Where is the spinal cord located?
in the vertebral canal
What are the spinal cord segments?
Cervical
Thoracic
Lumbar
Sacral
are brain structures determined by embryology?
Yes
Describe the brain structure by embryology
- The brain consists of the Forebrain prosencephalon and the brainstem.
- The Forebrain
prosencephalon consists of the diencephalon and telencephalon - The diencephalon consits of the thalmus and the hypothalmus
- The telencephalon consists of the Cerebrum, basal ganglia, and the hippocampus
- The brainstem consists of the Midbrain
mesencephalon and the Hindbrain
rhombencephalon. - The Midbrain
mesencephalon consists of the nf. Colliculus, Sup Colliculus, and the Ret Formation - The Hindbrain
rhombencephalon consists of the Medulla, cerebellum, and the Pons
Is it true that after 6 weeks, the Prosencephalon further differentiates into the Diencephalon and the Telencephalon?
Yes
Describe the 3 primary structures of the brain
- Forebrain (Prosencephalon) → Associated with higher cognitive functions, sensory processing, emotions, and voluntary movement.
- Brainstem → Connects the brain to the spinal cord and controls automatic functions like breathing and heart rate.
- Hindbrain (Rhombencephalon) → Responsible for motor control, balance, and involuntary functions.
Describe a lumbar puncture
- The image at the bottom right shows the process of a lumbar puncture, a procedure to collect CSF for analysis.
- The needle is inserted between L3-L4 or L4-L5 vertebrae into the subarachnoid space to withdraw CSF.
- This procedure helps diagnose infections (like meningitis), bleeding (hemorrhage), or neurological conditions.
Describe the meninges
Surrounds the CNS and the brain is suspended in a jacket of cerebrospinal fluid
What are the 3 layers of the meninges?
Tough outer layer: Dura mater
Arachnoid mater
Pia mater
What is the ventricular system the principle source of?
Fluid-filled cavities that are found in the brain that are the principle source of CSF
What are the functions of the ventricular systems?
- Removes waste products, such as excess neurotransmitter
- Supplies brain & spinal cord with nutrients
- Buffers changes in blood pressure and protects brain
- Supplies brain with fluid during dehydration
- Allows the brain to remain buoyant
What colour is healthy cerebrospinal fluid?
Clear and Colourless
If there is blood in the cerebrospinal fluid, what is this an indicator of?
a subarachnoid haemorrhage
If the cerebrospinal fluid is yellow, what is this an indicator of?
old blood
or jaundice
How many hemispheres does the brain have?
2, these are linked by the corpus callosum
Midbrain - visual, auditory information, motor control, sensation
Pons - links with cerebellum, modifies medulla output
Medulla - respiration, cardiovascular function
Cerebellum - balance, gait, fine movement, posture (back of brain)
Thalamus- integrates sensory information (LGN vision, MGN hearing)
Thalamus- integrates sensory information (LGN vision, MGN hearing)
Hypothalamus- autonomic control, appetitive drives
Hypothalamus- autonomic control, appetitive drives reproductive behaviour, homeostasis, endocrine control
Summary
The brain and nervous systems integrate sensory information to arrive at an appropriate motor output
The various cellular elements of the nervous systems (neurons and glial) underlie this ability
The highly morphologically-polarised nature of neurons creates obstacles to transport of molecules overcome by active processes
The development and structure of the human brain and nervous systems share similarities with other animals
Brain and spinal cord regions are arranged into highly-defined areas, each with their own specialised cellular components, anatomical connections and functions
