Chapter 3 - Cell Anatomy and Physiology Flashcards
neurons
~86 billion
- process information
glial cells
~85 billion
- support neurons
- structural support, nutrients, protection
cerebral cortex cell make up
- 82% of the total brain mass
- contains 16 billion neurons (19% of all neurons)
cerebellum cell make up
- 10% of the brain mass
- 69 billion neurons (80% of all neurons)
neuron structure
- dendrites
- cell body (soma)
- axon
dendrites
collect information from other cells
- provides input
cell body (soma)
nucleus
- provides integration
axon
transmits messages to other neurons
- provides output
axon hillock
where the axon begins at the end of the cell body
telodendrions
the lower end of the axon can split into several smaller branches
end foot
the button at the end of each telodendrion
- is close to another dendrite or another part of a cell but does not touch it
synapse
the ‘near-connection’ containing the area from the end of the end foot to an adjacent dendrite
- forms the information carrier between neurons
sensory neurons
- input
- afferent
- have long dendrites outside the CNS
- cell body in the dorsal root ganglion
- short axon inside the CNS
bipolar neuron
in the eyes, has a short dendrite and a short axon
interneuron
- integrate sensory and motor information within the CNS
- short dendrites and short axons
- only located inside the CNS
- e.g. pyramidal cells and purkinje cells
motor neurons
- output
- efferent
- short dendrites inside the CNS
- large cell bodies inside the CNS
- long axons outside the CNS
ependymal cells
- glial cell
- on the walls of the ventricles
- produce and excrete CSF
astrocytes (scaffold cells)
- glial cells
- provide structural support to the CNS
- stimulate the repair of damaged brain tissue (scarring)
- form the blood-brain barrier (enhance brain activity)
blood-brain barrier
- protective barrier between blood vessels and the brain
- ensures that nutrients and certain chemicals can move between blood vessels and neurons, while harmful substances are kept out
microglia (defence cells)
- originate in the blood from the immune system and migrate throughout the nervous system
- monitor the health of the nervous tissue and take over the role of the immune system
oligodendroglia
myelinate neurons in the CNS (multiple neurons at once)
- myelinated neurons, whose axons are covered in an insulating sheath, transmit information much faster than neurons that are not myelinated
- do not encourage neuronal repair
schwann cells
myelinate neurons in the PNS (only one at a time)
- help in restoration of cells in the PNS
cell membrane
the ‘wall’ of a cell, consisting of 2 layers of phospholipids
- seperates the intracellular and extracellular fluid
phospholipids
consists of a hydrophilic head, which is in contact with the fluid inside and outside the cell, and a hydrophobic tail, which constitutes inside of the membrane
- prevents fluid from crossing it
nucleus
- ‘executive office’
- contains 23 pairs of chormosomes (long chains of DNA with a double-stranded helix structure)
- each strand contains a sequence of four nucleotide bases
the four nucleotide bases
A always with T, C always with G
“All Tigers Can Growl”
- adenine (A)
- thymine (T)
- guanine (G)
- cytosine (C)
genes
segments of DNA strands
- genetic blueprints for the cell’s proteins
transcription
important in protein synthesis because RNA can leave the nucleus whereas DNA cannot
- a gene segment of the DNA strand uncoils to expose its nucleotide base inside the nucleus
- allows nucleotides to bind to the exposed nucleotide bases, forming a complementary strand of RNA
- in RNA, a nucleotide base called uracil (U) takes the place of thymine (T)
- once formed the single strand of RNA detaches from the DNA
mRNA
the transcribed strand of RNA
- called mRNA because it carries the genetic code outside the nucleus into the endoplasmic reticulum
- protein structures in the endoplasmic reticulum called ribosomes read the genetic code contained in MRNA
translation
- ribosomes transform the sequences of nucleotide bases into sequences of amino acids
- chains of amino acids are called polypeptide chains, and proteins are folded-up polypeptide chains
- encoded in sequences of 3 nucelotide bases (codons) on mRNA (single-stranded)
- bound together by peptide bonds
enzymes
proteins that enhance chemical reactions within the cell
cell membrane proteins
proteins can regulate the flow of substances across the cell membrane (e.g. channels, gates, pumps)
messenger molecules
proteins can be expelled from the cell through exocytosis and move from one cell to another transporting information
summarized process of proteins
nucleotide bases -> amino acids -> peptides -> proteins -> cells -> behavior
golgi bodies
where synthesized protein molecules are wrapped in membranes and marked where they should go
- then transported through microtubules towards their destination
channels, gates, and pumps
- some ions are able to pass through channels (potassium ions)
- some ions are able to pass through a gate if the gate is open
- some ions are pulled in whereas others are pushed out with a pump
chromosomes
- the nucleus contains 23 pairs
- pairs 1 to 22 are autosomes and determine physical characteristics and behavioral functions
- pair 23 are the sex chromosomes (X or Y form)
- females have an XX pair, males have an XY pair
- each chromosome has thousands of genes
- the corresponding genes within a pair are called alleles (gene of the father and genes of the mother)
homozygous and heterozygous
- homozygous: when both alleles are the same (they encode the same protein)
- heterozygous: when the alleles are different (three situations may occur: only the allele from the mother or father is expressed, or both at the same time)
dominant and recessive alleles
- dominant alleles: alleles that are expressed
- recessive alleles: alleles that are unexpressed
- when paired with a dominant allele, a recessive gene is often not expressed but can still be passed on to offspring
mutations
when genes are passed on to offspring and there is an error in overwriting the information
- when its only a single nucleotide base, it’s called a ‘snip’ (SNP = single nucleotide polymorphism)
- can be neutral, beneficial (increased bone density), or harmful (sickle cell disease)
Mendel’s law
when parents are both carriers of a particular recessive gene that causes a disease, e.g. Tay-Sachs disease, there are 3 possible outcomes:
- inherit the wild type alleles, preventing the disease from developing
- inherit a normal allele and a Tay-Sachs allele, resulting in a carrier like their parents
- can inherit 2 Tay-Sachs alllels, causing the disease to develop
