BIOL 124 Flashcards
What is the difference between “discuss” and “describe” in essay titles?
Describe is to find and list the facts about that subject whereas describe is more talking around and about the subject and what it’s related to.
What types of signalling between cells are there?
Free diffusion between cells
Via cytoplasmic connections
Direct cell-to-cell contact
What are the 3 types of free diffusion signalling?
Autocrine (same cell, usually growth regulation)
Paracrine (nearby cells, coordination between cells)
Endocrine (distant cells via hormones)
How do cells signal via cytoplasmic connections?
The signals are transfered through pores in the membrane (fastest mode of signalling)
How do cells signal between cell-to-cell contact?
Interactions between surface proteins and receptor proteins.
What types of signalling molecules are there?
Local regulators and hormones
What are growth factors (local regulator)
Peptides or proteins that stimulate cell proliferation
What are nerve growth factors?
Small proteins that regulate growth of target neurones
How do gases act as local regulators?
Nitric acid can act by increasing vasodilation while only having a half life of 1-5 seconds
What are prostaglandins?
Modified fatty acids that have multiple functions such as exitability of the uterine wall in childbirth to induce labour
What type of signalling molecules are neurotransmitters?
local regulators
What are major glands of the endocrine system?
Pineal
Pituitary
Thyroid
Parathyroid
Thymus
Adrenal
Pancreas
Ovaries/testes
What are the two main classes of hormone?
Peptides and proteins (bind to cell surface receptors)
Steroids (cholesterol based so passes through membrane)
How does a signal binding to a receptor on the cell elicit a response?
Via the signal-transduction pathway
How does the complement of signalling proteins affect the response.
It can lead to a variety of different responses
What are the three stages of cell signaling?
Reception
Transduction
Response
What is reception in cell signalling?
When the signal molecule directly interacts with a receptor on cell surface or inside the cell
What are ligands in cell signaling?
They are signalling molecules that lead to a change in protein shape or aggregation of 2 or more receptors
What are G-protein-coupled receptors?
It is a plasma membrane receptor that spans the membrane as seven alpha hellices and they work with a G protein
What happens when GTP is bound to the G protein and what happens with GDP
When GTP is bound it is activated
When GDP is bound it is inactive
G protein also funcions ars GTPase
What are Receptor tyrosine kinases?
Membrane bound receptors with intrinsic enzyme activity
It adds phosphate residues onto other proteins that it gets from ATP molecules
They are involved in growth factors and division and can cause cancer if abnormal.
What are ligand-gated ion channels?
A receptor that acts as a gate in the plasma membrane which opens/closes in response to chemical messangers (e.g neurotransmitter synapse channel)
What are intracellular receptors?
Receptor proteins found in cytosol or nucleus of cell which are activated by small hydrophobic messengers that can travel through the cell membrane (e.g testosterone)
What are the main endocrine glands and organs?
Glands:
Hypothalamus
Pituitary
Pineal
Thyroid
Parathyroid
Adrenal
Organs:
Thymus
Pancreas
Ovary
Testis
What is the function of the hypothalamus?
It releases inhibitory and releasing hormones which conotrol the release of the anterior pituitary hormone.
It also synthesises ADH ad Oxytocin which is released in the posterior pituitary
It also provides neural control of adrenal gland via preganglionic motor fibres
What is unique about the thyroid?
It is the only gland to store hormones
What is the pathway of iodine through the thyroid?
It is trapped from the bloodstream before being oxidised into I2 and released into the follicular lumen where tyrosine molecules become iodised.
T1 and T2 join to make T3 or T4 which is reabsorbed and diffuse into the blood
Why is thyroid hormone important in development?
It is involved in amphibian metamorphosis
Also important in ovarian tissue development and egg release as well as brain and bone development
What happens if thryoid hormones are out of balance?
Hyperthyroidism:
Tachycardia
Yremors
Warm, moist skin
Proximal muscle weakness
Gynecomastia in males
Goiter
Hyperthyroidism
Slow heart rate + increased blood pressure
Low body temp
Dry hair/skin
Lethargy + weakness
Reduced alertness
Puffy face
Goiter
(can occur in gestation)
What are corticoids responsible for in general?
Homeostasis e.g glucortioids regulate glucose homeostasis
Why does signal transduction have multiple steps
To amplify signals
To add redundancyTo provide more coordination and regulation opportunities
How are signals transmitted in signal trandsuction pathways?
Often through a cascade of protein phosphorylation
what molecules phosphorylate and which dephosphorylate?
Protein kinases add phosphates and activate proteins and Protein phosphatases remove them switching off the protein
What is cAMP and what enzyme does it interact with?
It is formed from ATP by adenyly cyclase and is broken down by phosphodiesterase
It activates protein kinase
What are the key phases of development?
Pre-organogenesis: Cell devision has started with the formation of 2 layers (bilaminar germ disc)
Embryo: Trilaminar germ disc (gastrulation), Basic body plan
Fetus: Growth, refinement and cell function
What is different in cleavage compared to regular cell division?
There is no growth phase so the cells dont get any bigger (hyperplasia not hypotrophy)
What are the sections of the blastocyst and what do they develop into?
The outer cells of the blastocyst (epiblast) develop into the placenta whereas the inner cell mass (hypoblast) develops into the embryo.
What does the blastocyst develop into?
Gastrula (going from 2 layers to 3)
What are the 3 germ layers called and what are they responsible for?
Ectoderm (skin and nervous system)
Mesoderm (Internal organs/blood)
Endoderm (Internal linings ie stomach cells, lung cells and thyroid cells)
Germ cells are also there but they come from the yolk to make sex cells
How does gastrulation occur?
Lecture 7 slide 19
Describe the process of neurulation
1) Notochord develops from dorsal mesoderm
2) Induction of neural plate from ectoderm layer above notochord
3) A neural groove froms and neural folds form from dorsal ectoderm
4) Neural folds rise up, meet and fuse to form neural tube which eventually becomes the CNS
What happens to the neural crest cells after primary neurulation?
They migrate away from the neural tube and are important in lots of things such as cranial formation and the parasymphetic nervous system
What is induction and how does it affect cell behaviour?
Induction is contact between cells resulting in signals from neighboring or distant cells that will affect cell behaviour based on where the cell is in the body through gene expression.
What are morphogens and what do they do?
They are long range directional signals that create gradients where cells will behave differently depending on where in the gradient they are.
How do we confirm that morphogens are important?
You change the morphogen and see what happens.
E.g lecture 8 slide 23 addition of another ZPA causes digit duplication
or slide 26 where inhibition of shh gene causes cyclopia
How does sperm enter the egg?
When it makes contact with the jelly coat of the egg it releases hydrolytic enzymes from the acrosome which dissolve the jelly coat allowing the sperm to bind to receptors on the envelope allowing it to pass through.
How is polyspermy prevented?
Fast block:
Membrane depolarisation following first sperm prevents fusion
Slow block:
Cortical reaction (cortical granules fuse with plasma membrane and remove sperm-binding receptors) and fertilization envelope polymerises stopping passage.
What is pronuclei fusion?
Migration of female pronucleus to male pronucleus by microtubules from male centrosome.
What are the components of a sperm cell?
Flagellum
Spiral Mitochondrion
Centriole
Nucleus
Acrosome
(in that order)
Why does human fertilisation require multiple sperm to interact with the egg?
Because a single sperm does not cotain enough hyaluronidase to prenetrate into the egg.
What are the mammalian sperm-egg molecular interactions?
ZP3 binds to Beta 1-4-galactosytransferase and triggers acrosomal release.
Acrosomal enzymes and Beta-N-acetylglucosaminidase digest zona pellucida glycoproteins
CD9, JUNO, SPACA6 and Izumo1 are essential for membrane fusion.
What are the critical timings in development of a baby?
Fertilisation/conception 14 days counted from last menstural period (LMP)
Preograngogenesis 2-4 weeks LMP:
Possible death
Embryonic period 3-10 weeks LMP:
Major malformations
Fetal period 11+ weeks LMP:
Functional defect and minor malformations (e.g finger webbing)
What are the external risks in the first trimester?
Causes:
Teratogen exposure
Drugs
Alcohol
Workplace and environmental conditions
Diet
Results:
Miscarriage
Fetal alcohol disorder
Small for gestational age
Spina bifida (failiure of neural tube closure)
Limb and cardiac syndromes (thalidomide)
Systemic syndromes (rubella virus)
What are the maternal (mother) changes in pregnancy?
Organ squashing
Respiratory function increased (to keep up with increased metabolism)
Digestive problems
Weight gain
Increased heart rate and stroke volume (more volume to pump)
Increased urination and incontinence due to squashing and stress
Breast enlargement
What are the problems in implantation and placenta?
Gestational Trophoblasic Tumors (overgrowth of trophopblasts, lack of genetic material to form embryo)
Ectopic pregnancy
Implantation in uterine tubes with normal pregnany signs but with vaginal bleeding and must be terminated when detected to preseve mothers life
Pre-eclampsia
Hgh blood pressure and proteinura headache, vision problems, vomiting and swelling, pain below ribs, may induce early birth
Promblems with later pregnancy
Gestational diabetes (insulin resistance)
Gestational hyperthyroidism (decreased TSH levels)
Obstertric cholestasis: leaking of bile salts into blood, pruritis (itching)
Gestational transient thyrotoxicosis: persistent vomiting and weight loss
What occurs in implantation?
Blastocyst attatches to unterine wall
Blastocyst begins to differentiate making cytotrophoblast (densely packed cells will create villi) and syncytiotropoblast (outer, invasive cells which are loose and forms gaps and eventually vacuole).
Extraembryotic cavity grows
How does the placenta form?
Villi increase at the fetus forming chorion frondosum and the placenta
Maternal blood flows into intervillous lakes
Chorionic villi grow into lakes
Bloow flows into capllaries from the embrionic heart.
What problems occur in the first 4 weeks of pregnancy?
Embryo loss:
-Placental hormones not produces enough to maintiain placenta
-Genetic problems mean cells don’t replicate/surivive
What conditions arise from early events in pregnancy?
Caudal dysgenesis (lack of caudal mesoderm)
Sitrus inversus (internal organ reversal)
Sinus ambiguous partial malrotation (resposible for 3% of congenital heart disease)
Sacrococcygael Terratoma
What happens in week 4-6?
Embryogenesis:
Neurulation initiated in week 2-3
Somites develop
Formation of blood vessels and cells in yolk
Heart tube begins to beat in week 5
Neural tube closes
Heart valves start in week 6 limb bulbs apear between 5mm and 20mg in week 6
What problems arise from week 4-8?
Renal agenesis (kidney missing)
Polyhydramnios
Problem with lung bud / bronchi formation
Various cardiac problems
Limb malformations
What happens between week 8 and 12
Embryo transitions into fetus:
Tooth buds form
Ossification of long bones
Pituitary forms
Heart seperates into 4 chambers
Primitive germ cells arrive
Physiological hernia (pertrusion) as intestines form without room (retracted in week 11-12)
Thryoid + pancreas developed
Liver produces bile
Fetal reflexes
Key lung elements present.
What problems occur in week 8-12?
Congenital endocrine disorders
Cardiac septal malformations
Omphaocoele (intestines fail to retract)
Gut malrotation
Sexual development differences
What happens between 12-16?
Fetal development:
Antibody production
Face nearly fully developed
Muscles and nerves developing strength
Genetalia clearly visable
Pregnancy bump maybe visable
What problems happen 12-16 weeks
Eye problems
Ear problems
Teeth problems
Immune system problems
Brain development issues
How is labour stimulated?
Fetal and maternal oxytocin increase exitability of uterus triggering contractions.
