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288 Cards in this Set
- Front
- Back
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What is the difference between a eukaryote and prokaryote?
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Eukaryotes – one or more cell organism with a distinct nucleus.
Prokaryote – single celled microorganism, lacking a well defined membrane enclosed nucleus. |
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Function of the mitochondria
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site of aerobic respiration
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Function of nucleus
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contains genetic material
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Function of endoplasmic reticulum
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lipid and protein synthesis
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function of golgi apparatus
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protein packaging
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function of cell membrane
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phospholipid bilayer, cell structure
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function of ribosomes
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protein synthesis
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What are lysosomes?
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enzyme filled vesicles
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What are peroxisomes?
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self replicating organism
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What is the cytoskeleton?
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internal scaffold of the cell
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What is the centrosome?
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microtubule organising centre
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Basic characteristics of viruses
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replicates in a host, nucleocapsid + lipid membrane
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Basic characteristics of prions
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infectious abnormally folded protein, replicates in a host without the need for genetic material. induces normal proteins to abnormally fold
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Prone, Supine
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Face up, down
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What is the anatomical position?
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standing position
head, palms, feet facing forward |
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median plane (midsigital)
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biscuits body in two equal halves
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sagital plane
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lies in parallel to median
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coronal plane
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right angle to sagittal
bisects body into anterior and posterior |
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transverse plane
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horizontal, bisects body into inferior and superior
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superficial
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shallow
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deep
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deep
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proximal
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close
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distal
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far
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superior
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upper/above
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inferior
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lower/below
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anterior (ventral)
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front
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posterior (dorsal)
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back
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medial
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middle
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lateral
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side
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what is a reflection
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anatomical fold in a membrane
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relations
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position/association
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visceral
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pertains to organs
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parietal
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pertains to walls
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What are the 3 parts that make up the sternum?
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manubrium, sternal body, xiphoid process
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at what level is the suprasternal notch?
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T2
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at what level is the sternal angle?
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T4
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at what level is the xiphoid process?
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T9/10
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which ribs are true?
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ribs 1 – 7
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which ribs are false?
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ribs 8 – 10
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which ribs are floating?
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ribs 11 – 12
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at what level does the trachea bifurcate?
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T4/5
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how many lobes does the left lung have?
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2 – superior and inferior
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how many lobes does the right lung have?
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3 – superior, middle and inferior
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how many fissures does the left lung have?
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1 – oblique
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how many fissures does the right lung have?
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2 – horizontal and oblique
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what impressions can be found on the posterior of the right lung?
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cardiac and azygos
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what impressions can be found on the posterior of the left lung?
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cardiac, aortic, lingula
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what is the pleural membrane?
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double layered membrane surrounding the lungs
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what are the layers of the pleural membrane?
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visceral (inner) and parietal (outer)
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what is the pleural cavity?
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found between the visceral and parietal layers of the pleural membrane
contains pleural fluid |
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what is a pneumothorax?
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air in the pleural cavity
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what is a pleural effusion?
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fluid in the pleural cavity
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what is a haemothorax?
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blood in the pleural cavity
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what is a chylothorax?
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lymph in the pleural cavity
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describe the role of amino acids in protein synthesis
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amino acids linked to each other with a peptide bond, forming polypeptide chain.
order of amino acids determines protein structure and function |
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describe the primary structure of proteins
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simple chain of amino acids, peptide bonds
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describe the secondary structure of proteins
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intramolecular hydrogen bonding – alpha helix
intermolecular hydrogen bonding – beta helix |
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describe the tertiary structure of proteins
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electrostatic, hydrogen, hydrophobic, covalent bonding – 3D configuration of protein
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describe the quaternary structure of proteins
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protein complex,
single polypeptide chain is a subunit of a larger structure |
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Structure of DNA
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double stranded chain of nucleotides,
hydrogen bonds between base pairs covalent bonds between sugar phosphates |
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Function of DNA
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contains genetic material,
codes for proteins |
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Structure of RNA
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single stranded chain of nucleotides
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Function of RNA
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converts information stored in DNA into protein
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what is mRNA?
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messenger RNA, copies gene data when protein coding gene is expressed
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what is tRNA?
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transfer RNA, translates between genetic code and protein structure
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what is rRNA?
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ribosomal RNA, forms the ribosomes
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what is small RNA's?
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form small cellular organelles
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what is small regulatory RNA?
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acts as cell components for helping control gene expression
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what is large non coding RNA?
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form components of chromatin used in controlling gene expression
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what is transcription?
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DNA into RNA
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what is translation?
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RNA into proteins
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what is a chromosome?
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tightly coiled DNA
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what is a gene?
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section of genetic material on a chromosome
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what is PCR?
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polymerase chain reactions,
use or primers or machinery to replicate a specific region of one gene |
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what does helicase do in DNA replication?
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unzips the DNA molecule creating replication fork.
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what does primase do in DNA replication?
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creates a RNA primer – starting point for replication
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what does DNA polymerase do in DNA replication?
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binds to primer adding DNA bases
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what order does the DNA polymerase run along the DNA strand in DNA replication?
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5 to 3
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what is the leading strand in DNA replication?
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the DNA polymerase runs continuously down the strand without stopping
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what is the lagging strand in DNA replication?
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there are multiple primers on the DNA strand.
DNA polymerase has to keep stopping and starting |
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what does exonuclease do in DNA replication?
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removes all the primers
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what happens once the primers are removed in DNA replication
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DNA polymerase fills them in with bases
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what does DNA ligase do in DNA replication?
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seals up the daughter strands
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what enzyme is responsible for unzipping the DNA molecule in replication? |
DNA helicase |
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what enzyme creates the RNA primer in DNA replication |
primase |
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what enzyme in DNA replication binds to the primer added bases |
DNA polymerase |
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what enzyme removes the primers in DNA replication? |
exonuclease |
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what enzyme seals up the DNA strands in DNA replication? |
DNA ligase |
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what are the steps of DNA replication? |
DNA molecule unwinds unzipped by DNA helicase Primase creates RNA primer, starting point DNA polymerase binds to primer, adds on DNA bases running direction 5-3 in the lagging strand there is multiple primers Exonuclease removes all primers DNA polymerase fills in spaces left by primers DNA ligase seals up strands DNA molecules wind up |
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what is RNA polymerase 1?
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enzyme used to make rRNA
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what is RNA polymerase 2?
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enzyme used to make mRNA
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what is RNA polymerase 3?
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enzyme used to make tRNA (+sRNA)
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where does transcription occur?
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in the nucleus
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describe the post transcriptional processing of RNA
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cap added to 5 end,
poly A tail added to 3 end gene splicing of introns |
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what is the role of splicing in transcription?
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removes introns, turns pre RNA into RNA
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what happens after splicing in transcription?
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RNA leaves the nucleus, into the cytoplasm
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what happens to tRNA once it leaves the nucleus in transcription?
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folds, aminocycl tRNA synthatase joins 1 tRNA to 1 amino acid
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describe transcription of ribosomes
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occurs in nucleolus
RNA polymerase 1 transcribes pre rRNA splicing to form small rRNA + large rRNA leaves the nucleolus folding into small subunit + large subunit leaves nucleus into cytoplasm attachment to mRNA as ribosome |
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what enzyme is used to make rRNA |
RNA polymerase 1 |
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what enzyme is used to make mRNA |
RNA polymerase 2 |
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what enzyme is used to make tRNA |
RNA polymerase 3 |
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what enzyme is used to make sRNA |
RNA polymerase 3 |
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what are the steps of transcription? |
RNA polymerase binds to DNA molecule with transcription factors, creating the transcription initiation complex the transcription initial complex is activated by activator proteins RNA polymerase used the DNA molecule as a template to make a pre RNA molecule splicing removes introns, creating a RNA molecule RNA molecule leaves the nucleus |
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describe the translation of the genetic code into a polypeptide chain
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ribosome unit attaches to one end of mRNA and moves along attaching tRNA (codons to complementary anticodons)
amino acids are released by tRNA to make the polypeptide chain |
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conversion of genetic code into amino acids
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DNA to RNA
A – U T – A C – G G – C |
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what type of mutations can exists
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point shift and frame affect amino acids,
disease |
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how are genes packed in the nucleus |
active genes are lightly packed (euchromatin) inactive genes are densely packed (heterochromatin) |
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what are monosaccharides?
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simple sugars
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what are disaccharides?
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2 monosaccharides
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what are oligosaccharides?
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2 – 10 monosaccharides
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what are polysaccharides?
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10+ monosaccharides
aldehydes or ketones |
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what is the functional group is aldehydes?
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(aldoses)
O = C – H |
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what is the functional group of ketones?
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(ketoses)
– C = O |
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what is sucrose made of?
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glucose + fructose
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what is lactose made of?
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glactose + glucose
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what is maltose made of?
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glucose + glucose
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what kind of bonds do disaccharides have?
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O – glycosidic bond, formed between two –OH groups from each sugar.
results in elimination of H2O |
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where can the O – glycosidic bond be positioned?
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1,2
1,4 1,6 alpha or beta |
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what glycosidic bonds can be found on the different disaccharides?
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maltose – alpha – 1,4
lactose – beta – 1,6 sucrose – alpha – 1,4 |
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what are the two forms of starch?
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amylose alpha – 1,4
amylopectin (alpha – 1,6 and alpha - 1,4) |
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what enzyme can break down alpha - 1,4 bonds?
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amylase
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what bonds can be found in cellulose
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beta – 1,4 D linked glucose
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what bonds can be found in glycogen?
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mainly alpha – 1,4 bonds
some alpha – 1,6 bonds which allow for branching |
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what is a glycoprotein?
how are they formed? |
oligosaccharides + proteins
by glycosylation of proteins |
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how are the sugars linked to the proteins in glycoproteins?
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by asparagine (N linked)
by threonine or serine (O linked) |
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what is the main function of mucus?
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protective layer on epithelial surfaces
airways – traps foreign particles digestive tract – lubrication + protection reproductive – (cervical) prevents infection |
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structure of mucin
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highly O – glycosylated protein backbone, attracts and retains water
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formation of hydrated lattice gel in a mucin
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by polymerisation via disulphide bond (SS)
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where is protein synthesis initiated?
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cytosol
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how is protein destination determined?
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by location of ribosome during translation
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what type of proteins are formed from free ribosomes?
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cytosolic, mitochondrial, nuclear, peroxisomal
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how are ER ribosome proteins formed?
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translation begins
SRP binds to ribosome, translation is paused SRP + ribosome unit bind SRP receptor SRP released, translation proceeds |
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difference between rough ER and smooth ER
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rough ER – ribosome coated, entry point for proteins
smooth ER – no ribosomes, lipid and lipid membrane biosynthesis |
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Role of ER in intracellular transport of proteins
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folding of transmembrane proteins,
post translational modification |
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Role of Golgi Apparatus in intracellular transport of proteins
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proteins sorted
entry Cis face exit Trans face vesicular transport – exocytosis |
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three types of coated vesicles
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clathrin – from plasma membrane, between enosomal and golgi compartments
coat protein I (COPI) from golgi compartment coat protein II (COPII) from ER to golgi |
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where does quality control mechanism of secretory pathway occur
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ER, biosynthetic arrest of misfolded proteins
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what is the functions of epithelia in different cell types
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protection
exchange (alveoli) filtration (kidney tubules) absorption (intestines) sensation (taste buds) secretion (glands) |
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how are the epithelial layers attached to the basal lamina and each other
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tight junctions
anchoring junctions channel forming junctions |
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what are tight junctions
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membrane proteins that seal adjacent cells together
prevent leakages generate polarity |
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what are anchoring junctions
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provide mechanical stability
allows functioning as a cohesive unit |
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what type of anchoring junctions are found in actin filament for cell to cell
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adherens junctions
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what type of anchoring junctions are found in actin filament for cell to basal lamina
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focal junctions
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what type of anchoring junctions are found in intermediate filament for cell to cell
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desmosomes
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what type of anchoring junctions are found in intermediate filament for cell to basal lamina
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hemidesmosomes
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what are gap junctions/channel forming junctions
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cell to cell
allow diffusion and communication |
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what is the basement membrane
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basal lamina and reticular lamina
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function of basement membrane
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anchoring of epithelial cells to connective tissue below
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function of simple squamous cells
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absorption
filtration minimal barrier to diffusion |
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location of simple squamous cells
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capillaries
alveoli abdominal + pleural cavities |
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function of simple cuboidal cells
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secretion + transport
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location of simple cuboidal cells
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glands and ducts
kidney tubules covering of ovary |
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function of simple columnar cells
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absorption
protection secretion |
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location of simple columnar cells
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digestive tract
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function of stratified squamous cells
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protection
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location of stratified squamous cells
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mouth
skin upper throat oesophagus |
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function of pseudo stratified columnar cells
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absorption
protection |
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location of pseudo stratified columnar cells
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upper respiratory tract,
trachea |
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function of transitional cells
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stretchable layer
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location of transitional cells
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bladder
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function of microvilli
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increase surface area,
increase absorption |
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function of keratinised surface of skin
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inert protective layer
phospholipid around upper layer of cells, waterproofing |
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function of ciliated pseudo stratified columnar cells
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coordinated beating of cilia sweeps mucus up and out of airways
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location of ciliated pseudo stratified columnar cells
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airways
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where found you find adherent junctions |
actin filament, cell to cell |
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where would you find focal junctions |
actin filament, cell to basal lamina |
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where would you find desmosomes |
intermediate filament, cell to cell |
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where would you find hemidesmosomes |
intermediate filament, cell to basal lamina |
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major fluid compartments of the body
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intracellular (30–40%) 25L
extracellular (20%) – interstitial (16%) 13L – plasma (4%) 3L –transcellular (1–3%) 1–2L |
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what is osmolarity
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total concentration of dissolved particles in a litre of solution
osmol/L |
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what is osmolality
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measure of amount of particle and molecules that attract water
osmol/Kg |
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what is the major cation in extracellular fluid compartment
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Na+
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what is the major anion in extracellular fluid compartment
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Cl– HCO–3
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amount of protein in extracellular fluid compartment
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small
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what is the major cation in intracellular fluid compartment
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K+
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what is the major anion in intracellular fluid compartment
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inorganic phosphate
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amount of protein in intracellular fluid compartment
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big
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what is isotonic solution |
concentration of solute is the same when compared to another solution |
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what is hypotonic solution |
concentration of solute is lower another solution |
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what direction does water move if a cell is placed in a hypotonic solution |
water moves in |
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what is a hypertonic solution |
concentration of solute is higher than another solution |
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what direction does water move if a cell is placed in a hypertonic solution |
water moves out |
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what is a iso-osmolar cell |
a cell with the same osmotic pressure as the cells around it |
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what is a hypo-osmolar cell |
a cell with a lower osmotic pressure than the cells around it |
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what direction does water if a cell is hypo-osmolar |
water moves out |
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what is a hyper-osmolar cell |
a cell with a higher osmotic pressure than the cells around it |
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what direction does water move if a cell is hyper-osmolar |
water moves in |
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without proteins, in what direction will substance move across membranes |
from area of high concentration to area of low concentration |
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what is relative permeability of the membrane to hydrophobic particles |
high permeability |
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what is the relative permeability of the membrane to small uncharged polar particles, without proteins |
medium level permeability |
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what is the relative permeability of the membrane to large polar particles, without proteins |
low permeability |
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what is the relative permeability of the membrane to ions, without proteins |
impermeable |
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how do molecules move through the membrane in passive diffusion |
directly through lipid bilayer, down concentration gradient |
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how do molecules move through the membrane in facilitated diffusion |
through the membrane through pores, channels and carriers (uniports) |
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how do molecules move through the membrane in active transport |
through the membrane against concentration gradient, energy is required |
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how do molecules move through the membrane in secondary active transport |
co transport (symporters) - movement of a solute is coupled to the movement of another in the same direction counter transport (antiporters) - movement of two or more solutes in opposite directions |
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what is the driving force in passive diffusion |
the electrochemical gradient |
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what is a non gated channel |
integral membrane proteins that allow direct access to cell |
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examples of non gated channels |
porins in bacteria mitochondrial porins nuclear pore complex aquaporins |
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what is a gated channel |
the opening of the channel is dependent on voltage, mechanical or ligand binding |
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examples of gated channels |
ENaC, K+ channels, Ca++ channels, most ions |
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how does a carrier mediated channel (uniport) work |
carrier opens solute enters + binds outer gate closure inner gate closes solute released inner gate closes |
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what is the driving force in secondary active transport |
kinetic energy provided by electrochemical gradient |
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example of symporter |
Na+/glucose transporter (SGLT) |
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example of antiporter |
Na+/H+ |
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mechanism of action of active transport |
transport against concentration gradient by hydrolysis of ATP |
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what is a P type ATP transporter |
ATP binds to protein, phosphate is released energy released is used to transport molecules across membrane example - Na+/K+ pump |
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what is an ABC transporter |
ATP Binding Casette Transporter binding of ATP releases energy allowing for transport of small molecules |
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what are tracts |
bundles of axons in CNS |
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what are nuclei |
groups of neuronal cell bodies in the CNS |
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what are bundles of axons in the CNS known as |
tracts |
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what are groups of neuronal cell bodies in the CNS known as |
nuclei |
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what are nerves |
bundles of axons in the PNS |
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what are ganglia |
groups of neuronal cell bodies in PNS |
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what are bundles of axons in the PNS known as |
nerves |
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what are groups of neuronal cell bodies in the PNS known as |
ganglia |
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what are the components of the CNS |
brain - centralised control centre spinal cord - connects brain to PNS grey matter - cell bodies white matter - fibre tracts |
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what is the role of the enteric nervous system |
nerve supply to and from the gut, can work independently of the CNS |
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what is the role of the PNS |
nerve supply to the rest of the body |
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what are the different types of nerves within the PNS |
afferent - toward the CNS, sensory modalities efferent - away from CNS, motor modalities |
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what are the different types of neurones within the PNS, (multipolar or unipolar)? |
motor - multipolar sensory - unipolar |
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what is the difference between sensory and motor neurones? |
motor neurones - cell bodies in spinal cord, fast, myelinated sensory neurones - cell bodies in dorsal root ganglia, different types with different speeds, myelinated and unmyelinated |
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what are the components of a neurone |
soma (cell body) contains nucleus dendrites (branches off cell bodies, contain information) axon hillock (main conducting component) node of ranvier (little space between the two squares) terminal bouton (axon terminals) |
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what type of poles can you get in different types of neurones (uni, multi, bi) |
multipolar and unipolar - motor + sensory neurones bipolar neurone - interneurones |
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where is myelin on an axon in PNS |
myelin surrounding axon in swhann cell |
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where is myelin on an axon in CNS |
oligodendrocyte myelinated sections of axons |
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what is multiple sclerosis? |
autoimmune disease caused by patchy destruction of myelin in the CNS |
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what factors can affect conduction speed in axons |
temperature, axon diameter, myelination |
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what is the composition of myelin |
lower protein content than most cells (25-30%) more lipids (70-75%) |
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what function is related to myelin containing basic protein |
structural |
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what function is related to myelin containing glycoprotein |
signalling |
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what are the main lipids in myelin |
cholesterol and phospholipids phophatdylserene phosphatidylinositol sphingomyelin |
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describe the formation of myelin |
membrane wraps + winds around axon contraction to squeeze out the cytoplasm multilayer membrane |
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what determines resting membrane potential |
distribution of ions (mostly sodium and potassium) across the membrane |
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what does the nearest equation predict |
equilibrium membrane potential based on concentration gradient of an ion across membrane |
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how is an action potential triggered in CNS |
neurone responds to stimuli from neurotransmitter (acetylcholine, serotonin, gamma amino butyric acid) |
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how is an action potential triggered in PNS |
neurone responds to particular stimuli (mechanical or chemical) |
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what happens when an action potential is triggered in CNS or PNS |
open ion channels in stimulated neurones to alter membrane premeability |
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what are the different types of synapses |
axodendritic - dendritic spine connects to neurone, new dendritic spines grow as we learn and make connections in the brain axosomatic - axons making connections to cell bodies directly through synapses axoaxonal - one axon acts on another before it synapses with the active zone |
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what is the mechanism of action in triggering an action potential |
action potential reaches the synaptic bouton, neurotransmitter is released electrical signal becomes chemical acts on receptors in post synaptic neurone opens channels permeable to sodium |
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describe the generation and conduction of an action potential |
stimulus opens ion channels threshold is reached (VG Na+ opens) triggering beginning of action potential depolarisation (potential difference goes from negative to positive) VG Na+ closes, VG K+ opens after depolarisation (VG K+ closes) after hyperpolarisation (potential difference dips below normal resting potential before levelling out) |
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what is the difference between generation and conduction of an action potential in a myelinated and unmyelinated cell |
myelinated acts as insulator, membrane below is unable to depolarise conduction velocity is greater in myelinated and more energy efficient membrane depolarisation jumps between nodes of ranvier in myelinated |
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what is the synapse |
point of contact between two neurones |
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how does the arrival of an action potential at the terminal bouton stimulate release of neurotransmitter |
neurotransmitter is contained within a vesicle on the presynaptic bouton impulse causes increase in permeability of Ca++ at end of neurone stimulated release of neurotransmitter my exocytosis neurotransmitter binds to receptor, neurotransmitter broken down or taken up, stimulates increased ion conductance in post synaptic cleft generation of EPSP or IPSP |
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what is an inotropic receptor |
neurotransmitter binds directly to ion channel allows for fast selective movement of ion |
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what is a metabotropic receptor |
neurotransmitter binds to receptor and triggers intracellular signalling, slower than metabotropic |
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action of acetylcholine on inotropic and metabotropic receptors |
inotropic - nicotinic - excitatory response (depolarisation) metabotropic - muscarinic - inhibitory response (hyperpolarisation) |
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what is EPSP |
excitatory post synaptic potential depolarisation of post synaptic neurone increased likelihood of cell reaching threshold |
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what is IPSP |
inhibitory post synaptic potential hyper polarisation of post synaptic neurone decreased likelihood of cell reaching threshold |
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what is the primary function of the ANS |
controls visceral function maintain homeostasis and control of the internal environment of the body (HR, breathing, blood pressure, rate of digestion) |
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describe the different ganglia found in the parasympathetic and sympathetic nervous system |
para sympathetic has long pre ganglionic and short post ganglionic chains sympathetic has short pre ganglionic and long post ganglionic chains |
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how are the adrenal glands innervated |
directly by pre ganglionic neurones of the sympathetic nervous system |
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where do the ganglia of the parasympathetic system stem from in the spinal column |
carniosacral division carnival nerves III, VII, IX, X S2, 3, 4 |
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where do the ganglia of the sympathetic system stem from in the spinal column |
thoracolumbar division T1 - L2 |
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what type of receptors are found in pre ganglionic synapses |
ligand gated ion channels nicotinic (cholinergic) |
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what type of synapses are found in post ganglionic synapses |
g protein coupled receptors parasympathetic - muscarinic (cholinergic) sympathetic - alpha 1,2 beta 1,2,3 (adrenergic) |
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what type of receptors are g protein coupled |
metabotropic, muscarinic cholinergic or adrenergic |
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what type of receptors are ligand gated ion channels |
inotropic, nicotinic cholinergic |
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what neurotransmitter stimulates pre ganglionic synapses |
acetylcholine |
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what neurotransmitter stimulated post ganglionic synapses |
sympathetic - noradrenaline parasympathetic - acetylcholine |
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what different types of muscarinic receptors are there and where are they found |
M1 - neural M2 - heart M3 - glandular M4 & M5 |
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which muscarinic receptors are linked to Gq proteins |
M1, M3, M5 |
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which muscarinic receptors are linked to Gi proteins |
M2, M4 |
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what is the mechanism of action of Gq protein coupled receptors. |
ligand binds to receptor conformational structural change alpha unit activates 2nd messenger system PIP2 splits into DAG and IP3 IP3 disassociates from membrane, mobilises intracellular calcium DAG activates protein kinase C |
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what is the mechanism of action of Gi protein coupled receptors |
ligand binds to receptor conformational structural change alpha unit activates 2nd messenger system deactivation of adenylate cyclase decrease in cAMP, decrease in Protein Kinase A |
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what is the mechanism of action of Gs protein coupled receptors |
ligand binds to receptor conformational structural change alpha unit activates 2nd messenger system activation of adenylate cyclase increase in cAMP, increase in Protein Kinase A |
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what are the different types of adrenergic receptors and where are they found |
alpha 1 - many tissues alpha 2 - pancreas and nerves beta 1 - heart beta 2 - many tissues beta 3 - muscle and adipose tissue |
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what adrenergic receptors are linked to Gq proteins |
alpha 1 |
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what adrenergic receptors are linked to Gi proteins |
alpha 2 |
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what adrenergic receptors are linked to Gs proteins |
beta 1 and 2 |
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what innervates smooth muscle |
ANS, endocrine and paracrine factors |
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what feature of smooth muscle allows it to function as a single unit |
external lamina |
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what feature of smooth muscle allows Ca++ entry |
caveoli |
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what is contraction of smooth muscle cells initiated by |
chemical neurotransmitter, paracrine factors, electrical excitation |
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how can electrical signal spread through smooth muscle cell |
by neuromuscular synaptic transmission or electrical coupling, initiated by increase in Ca++ levels in the cell |
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what is neuromuscular synaptic transmission (as a means of spreading electrical signals through the smooth muscle cell) |
each synapse with the muscle from the neurone, increases the neuro axon diameter causing varisocities which contain neurotransmitters |
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what is electrical coupling (as a means of spreading electrical signals through the smooth muscle cell) |
electrical activity on few smooth muscle cells excite the membrane, opening gap junctions, innervating nerve cells by ion movement |
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what is unitary contraction |
a single neurone branches to few cells, signalling through gap junctions cells can contract independent of nervous system |
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what is multi unit contraction |
each cell receives nervous input, cells are electrically isolate, act independently of each other |
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what are actin and myosin |
actin are thin filaments myosin are thick filaments contractile proteins, anchored by dense bodies |
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what happens to actin and myosin during smooth muscle contraction |
actin and myosin slide past each other, pulling cells inwards filaments shorten, muscle contracts external lamina helps cells contract together |
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what is cross bridge cycling (in smooth muscle contraction) |
myosin head attaches to actin (requires ATP) |
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what is the calcium sensor in smooth muscle |
calmodulin |
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what is the calcium sensor in skeletal muscle |
troponin |
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how does calcium enter the cell (3 routes) |
voltage independent routes - from sarcoplasmic reticulum - through ligand gated ion channels voltage dependent route - voltage gated ion channel in response to graded depolarisations or action potentials |
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describe the mechanism of action of smooth muscle contraction |
tigger calcium causes calcium to enter the cell through voltage gated channels (action potential) Ca++ (from outside the cell) acts as ligand, allows Ca++ to leave sarcoplasmic reticulum Ca++ binds to calmodulin activates myosin light chain kinase (MLCK) MLCK breaks down ATP, phosphorylation of myosin head - cross bridge cycling muscle tension |
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describe the mechanism of action of smooth muscle relaxation |
Ca++ pumped out of cell, or back into sarcoplasmic reticulum Ca++ bound to calmodulin released, deactivating MLCK myosin head dephosphorylated, decreasing myosin ATPase activity |
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what is the latch phase in smooth muscle relaxation |
when myosin does not immediately disassociate with actin |
