Nerves and Muscle Flashcards
Identify the key features and cells in the histological section of the three muscle types.
skeletal - peripheral and multinucleated, striated, t-tublules present, no cell to cell junctions
smooth - spindle shaped, no striations, single nucleus, calcium for contraction, gap junctions
cardiac - gap junctions and intercalated disks, cross striations, branched
Measure conduction velocity in human motor neurones.
The nerve conduction velocity (speed) is then calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes. A related procedure that may be performed is electromyography (EMG).
Describe the design, strengths and limitations of case-control studies
compares people with and without disease, no follow up, efficient for rare diseases, multiple exposures can be studied, prone to bias, needs precise case definition
Describe how to select case and control groups
case - need to decide whether to use incident or prevalent cases, source and eligibility criteria needs to be considered
control - best controls are from the same pool as cases, more controls increase precision of odds ratio
Describe types of bias which may affect epidemiological studies, including selection bias, recall bias, response bias and interview bias
selection bias - proper randomization is achieved
recall bias - participants may recall their exposures differently based on if they’re a case or control.
response bias - participants respond to questions about their exposure in the way they think is expected.
interviewer bias - person collecting exposure data introduces their own bias.
Recognise the basic ways in which muscle proteins are degraded and their involvement in cachexia.
muscle proteins can be degraded by the ubiquitin proteasome degradation system, by autophagy via the lysosome, or by calcium activated proteases.
cachexia - muscle breakdown exceeds synthesis, muscle atrophy occurs
Explain the concept of nitrogen balance.
when in balance, nitrogen intake is equal to output. it can be positive in growing children and pregnant women, and negative during starvation or illness.
Recognise the requirement for essential amino acids.
essential amino acids must come from our diet as they cannot be synthesised.
Explain the processes of transamination (requiring pyridoxal phosphate as a cofactor) and oxidative deamination, in order to produce ammonium ions.
transamination - alpha amino acid + alpha ketoglutarate >< alpha keto-acid + glutamate
oxidative deamination - forms ammonium ion from glutamate
Describe how urea is synthesised.
through the urea cycle (google)
Explain the concept of glucogenic and ketogenic amino acids.
glucogenic - carbon skeletons increase the concentration of glucose
ketogenic - carbon skeletons increase the concentration of ketone bodies
Explain the relevance of the genetic code.
Genetic code is the amino acid basis for all organisms
Explain why the genetic code must be at least three bases per codon.
A doublet code of 2 bases per codon would be insufficient as this would lead to 16 doublets when 20 amino acids are needed. A triplet code is sufficient, which gives 64 different triplets of bases. A triplet code allows amino acids to be specified by more than one codon - it is degenerate.
Explain why the genetic code is degenerate but not ambiguous.
specific amino acids code for specific proteins.
Explain the relevance of nonsense codons.
Stop codons are also called nonsense codons because they do not code for an amino acid and instead signal the end of protein synthesis.
