Lecture 1: Neurones and the Nervous System

Question 1

What does the nervous system do?

Answer 1

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.

Question 2

What parts are included in the sensory system?

Answer 2

Sense organs, sensory nerves, central sensory areas

Question 3

What does the integration system include?

Answer 3

making decisions from sensory input and stored record of previous experience (memories)

Question 4

What does the motor system include?

Answer 4

Motor neurones, central motor areas, all muscles and ducted glands of the body. These control movement both consciously and unconsciously.

Question 5

What are the units of the nervous system ?

Answer 5

Neurones

Question 6

Describe the Neuron doctrine (circa 1894)

Answer 6

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

Question 7

Is the golgi stain still in use and if so, what is it used for?

Answer 7

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.

Question 8

Are neurones continuous to other neurones?

Answer 8

No, they are one individual cell

Question 9

What are the 3 main parts of a neurone?

Answer 9

• Dendrites
• Soma (cell body)
• Axon

Question 10

What resulted in the findings of the neurone doctrine?

Answer 10

Anatomical investigation

Question 11

What do the end aborisations of the axon make contact with?

Answer 11

The end aborisations of the axon makes contact with tissues or other neurones.

Question 12

What is the function of the dendrites?

Answer 12

To increase surface area and to receive inputs

Question 13

What is the function of the axon?

Answer 13

To carry information over distances

Question 14

What is the function of the myelin?

Answer 14

To coat the axon and improve conduction [the speed of]

Question 15

What are nodes of ranvier

Answer 15

breaks in the myelin sheath

Question 16

How should we classify neurones?

Answer 16

• Morphology (multipolar, unipolar etc)
• Interneurones vs principle neurones
• By the neurotransmitter that they release i.e. cholinergenic, glutamateric, GABAergic etc

Question 17

What is one problem that is unique to neurones?

Answer 17

How to get material from the cell body to the terminals, where the neurotransmitter is released, particularly because neurones can be so long.

Question 18

How is the problem of getting material from the body to the terminals resolved?

Answer 18

• 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)

Question 19

Describe the mechanism of axonal transport

Answer 19

• 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.

Question 20

What are glial cells?

Answer 20

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.

Question 21

What are the different types of glial cells?

Answer 21

• Oligodendrocytes
• Astrocyte’s
• Microglial cells
• Ependymal Cells

Question 22

What do Oligodendrocytes do?

Answer 22

• Produce the myelin sheath around CNS axons to enhance signal transmission.
• In the PNS, they produce Schwann cells

Question 23

What do Astrocyte’s do?

Answer 23

• 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.

Question 24

What do Microglial cells do?

Answer 24

• They phagocytose dead cells
• They launch an immune response (surveillance cells)

Question 25

What do Ependymal Cells do?

Answer 25

- Line the ventricles of the brain and central canal of the spinal cord. - Produce and circulate cerebrospinal fluid (CSF).

Question 26

Do we still have ganglia ?

Answer 26

Yes

Question 27

What is the nervous system structure?

Answer 27

- Nerve nets -> Nerve rings -> Ganglia -> Fusion of ganglia

Question 28

Describe structures that make up the invertebrate ganglia

Answer 28

- Cell body - Axon in tracts - Ganglion sheath - Neurophil (dense regions of nerve fibers devoid of cell bodies ) - axons in neuropil

Question 29

Describe further nervous system development

Answer 29

- Fusion of ganglia - Brain and nerve cord - Vertebrates encephalization

Question 30

"We have lots of folds in our brain, but the brains of other species can be smooth". Is this statement true?

Answer 30

Yes

Question 31

"Humans have the highest “encephalisation quotient” (7-8): comparison of human brain size relative to mammalian reference species (cat)". Is this true?

Answer 31

Yes

Question 32

"Brain size scales with body weight, with common anatomical features across species". Is this true?

Answer 32

Yes

Question 33

Describe the composition of the Verterbate Nervous System

Answer 33

- 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. -

Question 34

Where is the spinal cord located?

Answer 34

in the vertebral canal

Question 35

What are the spinal cord segments?

Answer 35

Cervical Thoracic Lumbar Sacral

Question 36

are brain structures determined by embryology?

Answer 36

Yes

Question 37

Describe the brain structure by embryology

Answer 37

- 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

Question 38

Is it true that after 6 weeks, the Prosencephalon further differentiates into the Diencephalon and the Telencephalon?

Answer 38

Yes

Question 39

Describe the 3 primary structures of the brain

Answer 39

- 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.

Question 40

Describe a lumbar puncture

Answer 40

- 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.

Question 41

Describe the meninges

Answer 41

Surrounds the CNS and the brain is suspended in a jacket of cerebrospinal fluid

Question 42

What are the 3 layers of the meninges?

Answer 42

Tough outer layer: Dura mater Arachnoid mater Pia mater

Question 43

What is the ventricular system the principle source of?

Answer 43

Fluid-filled cavities that are found in the brain that are the principle source of CSF

Question 44

What are the functions of the ventricular systems?

Answer 44

- 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

Question 45

What colour is healthy cerebrospinal fluid?

Answer 45

Clear and Colourless

Question 46

If there is blood in the cerebrospinal fluid, what is this an indicator of?

Answer 46

a subarachnoid haemorrhage

Question 47

If the cerebrospinal fluid is yellow, what is this an indicator of?

Answer 47

old blood or jaundice

Question 48

How many hemispheres does the brain have?

Answer 48

2, these are linked by the corpus callosum

Question 49

Midbrain - visual, auditory information, motor control, sensation

Question 50

Pons - links with cerebellum, modifies medulla output

Question 51

Medulla - respiration, cardiovascular function

Question 52

Cerebellum - balance, gait, fine movement, posture (back of brain)

Question 53

Thalamus- integrates sensory information (LGN vision, MGN hearing)

Answer 53

Thalamus- integrates sensory information (LGN vision, MGN hearing)

Question 54

Hypothalamus- autonomic control, appetitive drives

Answer 54

Hypothalamus- autonomic control, appetitive drives reproductive behaviour, homeostasis, endocrine control

Question 55

Summary

Answer 55

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