Lecture 21 & 22 - Nervous System Flashcards
1
Q
Desc the 2 division of the the nervous system
A
- CNS:
- Composed of brain and spinal cord
- Contain interneurons (relay neurones) - Peripheral NS:
- Composed of peripheral/spinal/cranial nerves
- Motor and sensory neurones
2
Q
What is grey matter and white matter? Location of this is spinal cord and brain?
A
- Grey matter consists of nerve cell bodies, dendrites, non-myelinated axons, neuroglia (support cells)
- White matter consist of myelinated material (axons etc)
- In spinal cord: grey middle, white outside
- In brain: grey outside/dorsal (back), white inside/ventral
3
Q
What is the basic structure of a neuron?
A
- Contain many dendrites (to cell body, cytoplasmic projection) and one axon (away)
- Coated w myelin
- In CNS, myelin of axon produced by oligodendrocyte (insulate 50 axons)
- In PNS, myelin produced by Schwann cell (1 axon)
4
Q
What are the types of neurons? State location & function (jus know)
A
- Motor (CNS to periphery): send signals to effectors
- Sensory (periphery to CNS): send signals from receptors to CNS
- Integrative/interneuron (in CNS): integrate info
- Anaxonic (retina, no axons): act as relays (dendrite –> dendrite transmission)
- Pseudo unipolar, bipolar, postsynaptic autonomic cell bodies: OUTSIDE the CNS
- Purkinje and pyramidal cells & interneurons (majority of CNS but X confined to CNS): INSIDE CNS
- Reflex arc (sensory neurone –> interneuron –> motor)
5
Q
What is the features of neurone cell?
A
- ⬆️RER: contain Nissl bodies, basophilic (stain w basic dyes), ⬆️rRNA
- ⬆️Golgi
- Nucleus: stores tRNA (mRNA –> protein, translation)
6
Q
Desc structure of peripheral nerve (jus know, X in ILO)
A
- each are separated by connective tissue
- Endoneurium: (loose c.t) surrounds single axon
- Perineurium: (specialised c.t- transport proteins) surrounds clusters of axons (fascicles), maintain ionic comp.
- Epineurium: (dense irregular) sperate diff. nerves
- Paraneurium: separate nerve frm surrounding tissue
7
Q
PNS Histology
A
- Myelinated axons: blue rings, X myelin: white then thin blue
- Toluidine blue stains fat
- Small lumps of axon = Schwann cell cytoplasm
8
Q
What is an oligodendrocyte? Diff w Schwann Cell. How does it work?
A
- Myelinates axons in CNS
- Cytoplasmic processes form sheaths that wrap around each axon
- Diff: wrap around >1 axon
- VERY SMALL compared to v big Schwann cell (small black dot)
9
Q
What is the structure of unmyelinated axons?
A
- Axons engulfed by cytoplasm of Schwann cells (only in PNS) except for one region = intracellular space of mesaxon (very small gaps in axon border)
- Slower propagation of action potential
- Nucleolus contains rRNA
10
Q
What is the function of the support cell, Astrocyte? Structure?
A
- Structure: Star-like
- Function:
i) Control flow of nutrients in CNS (regulate own zone)
ii) Form part of blood-brain barrier
iii) Regulate nerve impulses by releasing glutamate
[located near node of Ranvier]
iv) Have ‘perineural feet’ (branches that touch nerve cells and blood) contain gap junctions: transport of nutrients (lactate) from blood to nerve cells
11
Q
What is a microglial cell? Functions?
A
- Large cell w elongated nucleus and few cytoplasmic projections
- Function:
i) Macrophage (Immune func): remove damaged nerve cells
ii) sense increase in K+ (v sensitive to changes)
12
Q
What is structure of an ependymal cell? Function and location?
A
- Line spinal canal (centre where the nerves are)
(derived from neural crest and looks like columnar epithelial cells) - Function: synthesise and secrete CSF
- Structure:
i) cilia: move CSF thru ventricles to spinal cord;
ii) microvilli: absorb CSF for removal of pathogens
[present pathogens to microglial cell]
iii) Modified tight junction control fluid release to brain/prevent leakage of CSF
[molecular and cellular contents of brain monitored through ‘spinal tap’]
13
Q
What is multiple sclerosis? Symptoms? Triggers?
A
- Autoimmune degradation of myelin
[axonal destruction & overgrowth of glial tissue also occurs in some cases] - A degenerative and relapsing disease
- Symptoms: spastic paralysis on both legs (most common), vision problems (diplopia), slurred speech, paraesthesia, muscle spasms, constipation & urinary retention
- Triggers: infection, stress, poor diet (omega-3 rich foods prevent flare ups), vaccination, heat
14
Q
What is Guillain-Barre syndrome? Mechanism behind and how is it diff to multiple sclerosis?
A
- Demyelination of axons of motor neurones
- T-cells and macrophages destroy myelin sheath: action potential delayed
- Diff to multiple sclerosis: can be cured if detected early
*Nerve cells X undergo mitosis, X replaced –> because highly complex
15
Q
Histology
A
- When looking at spinal cord, top part is dorsal (white matter)
- In cell body, dark staining regions of cytoplasm is RER, contain Nissl bodies
- Myelin is poorly preserved in histology bcs it is composed of lipid –> special fixatives (osmium tetroxide)
- When using MRI T1, water = black so CSF = black
