Lecture 3 Flashcards
2 types of nerve cells
Neurons (86 billion): information processing
Glial cells (85 billion): support cells
Brain mass information (3 sections)
Cerebral cortex (82% brain mass)
- 16 billion neurons (19% brain neurons)
- 61 billion glial cells
Cerebellum (10% brain mass)
- 69 billion neurons (80% brain neurons)
- 16 billion glial cells
Rest of the brain (8% brain mass)
- 1 billion neurons (1% brain neurons
- 8 billion glial cells
Neurons consist of 3 main parts
- Dendrites: Many of them, and their function is to collect information from other neurons.
- Cell body (soma): There is 1, and it integrates information.
- Axon: There is 1, it sends information and branches out at the end.
What is the flow of information through neurons?
Input: dendrites
Integration: cell body (soma)
Output: axon
3 major types of neurons
- Sensory neurons (afferent)
- Interneurons (association)
- Motor neurons (output)
Sensory neurons
Bring information to the CNS
- Long dendrites, short axon.
- Dendrites and cell body outside CNS (cell body in dorsal root ganglion)
- Axon inside CNS
Interneurons
Associate sensory and motor activity in the CNS
- Short dendrites, short axon
- Dendrites, cell body, axon inside CNS (in brain and spinal cord.
Motor neurons
Send signals from the brain and spinal cord to muscles
- Short dendrites, long axon
- Dendrites and cell body inside CNS (in lower brainstem and spinal cord), axon outside CNS
Glial cells - support they provide
Aid neurons in processing information by providing
- Physical support, protection
- Nutrients
- Increase conduction (lit. glue neurons together)
NB: glial cells DO NOT transmit information themselves
5 types of glial cells
- Ependymal cells
- Astrocytes
- Microglia
- Oligodendroglia
- Schwann cells
Ependymal cell
- Small; ovoid
- Secretes cerebrospinal fluid.
Astrocyte
- Star shaped, symmetrical
- Nutritive and support function.
- Move nutrients and chemicals between blood vessels and neurons.
- Stimulate repair of damaged brain tissue
- Enable tight bond between blood-vessel cells and neurons (BLOOD BRAIN BARRIER)
Microglial cell
- Small, mesodermally derived
- Defensive function
- Originate in the blood as an offshoot of the immune system (type of macrophage) and migrate throughout the nervous system.
Oligodendroglial cell
- Asymmetrical
- Forms myelin around axons in brain and spinal cord
- Inside CNS
- Myelinate neurons to enhance neural transmission speed (insulate cells)
Schwann cell
- Asymmetrical
- Wraps around peripheral nerves to form myelin
- Outside CNS
- Myelinate neurons to enhance neural transmission speed (insulate cells)
- Encourage neuronal repair: cells in the PNS can be repaired after damage
Histology
Brain staining: Histology
- Main disadvantage of staining is that it only works in fixed brain tissue.
- More recent imaging techniques: DTI (Diffusion Tensor Imaging)
- Clarity: makes brain tissue transparent
- Brainbow: transgenic technique
Cell membrane
- Membrane surrounding the cell
- Consists of 2 layers of phospholipid molecules
- Separates the intracellular and extracellular fluid.
- Semi-permeable (only specific molecules can pass).
Channel: specific ions can pass
Gate: ions can pass if the gate is open
Pump: active transport (uses energy) some ions in, others out e.g., sodium/potassium pump (helps maintain resting state potential).
Nucleus
- Cell core, contains chromosomes and genes
- DNA is made of chemical building clocks called nucleotides.
Nuclear membrane
Surrounds nucleus
Ensoplasmic reticulum
Assembles proteins
Golgi bodies
Wraps, addresses and ships off proteins
Microtubules
Form then transportation network
The 2 layers of phospholipid molecules in the cell membrane
- Head: phosphate group: hydrophilic (binds to water)
- Tail: fatty acid (lipid): hydrophobic (does not bind to water)
3 parts of nucleotides
(+ 4 nitrogen bases)
- Phosphate group
- Sugar group
- One of four types of nitrogen bases: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).
Mutations in genes
- Neutral (most common): does nothing.
- Beneficial (rare): increase bone density, tetrachromacy.
- Harmful (rare): sickle cell disease, cystic fibrosis.
Alleles
Can be dominant or recessive, they can lead to a certain trait or not.
Laws of Mendel
A) Recessive gene: two copies required to exhibit trait
B) Dominant gene: only one copy required to exhibit trait
Genes
Genes are the ‘blueprints’ for protein synthesis in the endoplasmic reticulum (protein factory).
- The sequence of bases in the gene spell out the order in which amino acids - the constituent molecules of proteins - should be assembled to construct a particular protein.
The ‘bases’ of behaviour (genes)
Bases –> amino acids –> peptides –> proteins –> cells –> behaviour
Amino acids –> peptides –> proteins
Amino acids are encoded in sequences of 3 nucleotide bases (codons) on mRNA (single stranded).
Protein packaging and shipment procedure
Go from ER to golgi bodies through the microtube (where their attached to a motor molecule). Then they get sorted: enzyme (chilling in the cell), to the membrane (protein chain), or kicked out (exocytosis).
