Case 1.1 Flashcards
Function of mitochondria?
Contain DNA, Site of ATP synthesis (energy production)
Where is mitochondrial DNA inherited from?
Mother
Function of lysosomes?
Destroy unwanted proteins and chemicals, Contain enzymes to perform this function, Break down small food molecules
Function of peroxisome organelle?
Breakdown of long chain fatty acids, which are then further broken down in mitochondria, Detoxifies harmful substances like hydrogen peroxide
Function of smooth endoplasmic reticulum?
Site of lipid and steroid synthesis
Why are there lots of smooth endoplasmic reticulum’s in the cells of the ovaries and testes?
Steroid hormone production
Functions of plasma membranes?
Retains cytoplasm, maintains cellular homeostasis, selective permeability, interacts with other cells with receptors
What is function of Golgi apparatus?
Modifies proteins by attaching carbohydrates to them, Packages proteins and some lipids received from the endoplasmic reticulum into vesicles
What is the function of the rough endoplasmic reticulum?
Coated in ribosomes, Site of protein synthesis, folding, modification and transport
What is the function of the nucleus?
Contains chromosomes, containing DNA, Site of DNA replication, transcription and RNA processing
What does DNA stand for?
Deoxyribonucleic acid
What does RNA stand for?
Ribonucleic acid
Function of ribosomes?
Site of protein synthesis, Interpret mRNA and assemble amino acid chains
Where are ribosomes found in the cell?
Free floating in the cytoplasm or attached to the rough endoplasmic reticulum
What is cytosol?
The liquid component of cytoplasm
Label a mammalian cell?
Insert photo
What are the 3 main areas of the sperm?
Head, Mid/connecting piece, Flagellum (tail)
What is contained in the head of the sperm?
Acrosome - tip of sperm’s head, Most of the sperm’s head is the nucleus
What is contained in the mid piece of the sperm?
Lots of mitochondria (to provide energy - ATP for sperm movement)
What is the flagellum of the sperm?
‘Tail’ like structure for movement
Label a sperm cell?
Insert image here
What is Zona pellucida?
A layer surrounding ovum. It contains lots of glycoproteins
What is the function of zona pellucida?
Protects egg from damage, Only allows one sperm through to fertilise the egg, Contains proteins the sperm can identify so they attach to the egg
What is corona radiata?
Layer of cells surrounding zona pellucida of ovum
Function of corona radiata?
Provides essential nutrients and hormones to developing egg to support it, Serves as additional protective layer, Guides and supports sperm as it approaches ovum, Regulates development and maturation of ovum
What are cortical granules?
Structures found in the cytoplasm of an ovum cell, Prevent multiple sperm entering the egg
What is perivitelline space?
Area between zona pellucida and plasma membrane of an ovum, Cortical granules release enzymes in here to prevent polyspermy (multiple sperm entering egg)
Draw an egg cell?
Insert an image here
What is spermatogenesis?
Sperm production in testes
Process of Spermatogenesis?
1) Mitotic proliferation: At puberty 2 types of spermatogonia proliferated Type A spermatogonia - Stem Cells (2n) Type B spermatogonia - These differentiate into primary spermatocytes (2n)
2) Meiotic differentiation
Type B spermatogonia -> primary spermatocytes (2n) via differentiation
Primary spermatocytes -> 2 x secondary spermatocytes (2n) via 1st meiotic division
2 x Secondary spermatocytes -> 4 x Spermatids (n) via 2nd meiotic division
3) Spermiogenesis (Round) Spermatids develop into spermatozoa (sing. Spermatozoon) They are remodelled and acrosome and flagellum develop. Nuclear condensation and cytoplasm shedding makes it more streamlined.
What is oogenesis?
Creation of ovum (inside follicle). The creation of the ovum (oogenesis) is a separate process to the development of the follicle around it (Folliculogenesis)
Describe process of oogenesis?
Inside embryo 1) Primordial germ cells from the yolk sac of the female embryo move to the developing ovaries. 2) These divide by mitosis to form millions of oogonia 3) Oogonia start first meiotic division, though stop at the diplotene stage of prophase 1, becoming primary oocytes. They stay this way throughout childhood until puberty. After puberty 6) Between birth and puberty many primary oocytes die via apoptosis 7) Hormone cycles of LH and FSH cause a small number of primary oocytes to be recruited each month, though usually only one fully matures 8) The primary oocyte completes first meiotic division and divides into a larger secondary oocyte and a polar body 9) A singular secondary oocyte is released from ovaries every month and waits in the ovarian tube to be fertilised by a sperm. 10) If a sperm penetrates the secondary oocyte, it will complete the 2nd meiotic division, producing a mature ovum and a small polar body. 11) The ovum can now fuse with sperm to form a zygote
What is folliculogenesis?
Development of the follicle which surrounds the oocyte
What is a follicle?
Contains an oocyte surrounded by granulosa and theca cells
What does a follicle look like?
Insert photo
Function of follicle?
Hormone production, Provides necessary environment for development and growth of oocyte, Releases secondary oocyte into ovarian tube (ovulation), After ovulation, the ruptured follicle forms the corpus luteum
Describe process of folliculogenesis
1) Primordial follicle: A primary oocyte surrounded by a single layer of squamous (flat) granulosa cells 2) Primary follicle: Hormonal changes at puberty (mostly FSH) stimulate primordial follicle to activate. Granulosa cells change from squamous to cuboidal. Zona pellucida forms around oocyte 3) Secondary follicle: Granulosa cells proliferate and theca layer forms. Small fluid filled gaps between granulosa cells form. 4) Tertiary (Antral) follicle: Follicle continues to mature and fluid filled gaps merge, forming antrum (a cavity) 5) Graafian follicle (mature): It is fully matured and ready to release secondary oocyte inside in response to LH surge
Describe process of sperm meeting ovum?
1) Sperm in seminal fluid enters vagina 2) Contractions of uterine muscles caused by prostaglandins encourage sperm into uterus 3) Peristaltic action of oviduct wall moves ovum along uterine tube into ampulla (middle) 4) Sperm and ovum meet 5) Acrosome of sperm uses enzymes to break down zona pellucida of ovum (outer layer) 6) Sperm goes through perivitelline space of ovum before fusing 7) Sperm nucleus merges with ovum nucleus, forming a 46 chromosome zygote 8) Ovum releases enzymes from cortical granules into zona pellucida in order to prevent additional sperm entering (polyspermy)
What is a zygote?
A single cell organism formed when a sperm fertilises an ovum
How many chromosomes in: Sperm, ovum, normal cell, zygote?
Sperm-23, Ovum-23, Normal cell-46, Zygote-46
Give a very simplified step by step process of the first 3 weeks of pregnancy?
Day 1 - Fertilisation and zygote formation, Day 2-3 - Cleavage divisions (mitosis), Day 3-4 - Morula formation (8 cells), Day 4-5 - Blastocyst formation (32-64 cells), Day 5 - Blastocyst hatching, Day 6-7 - Implantation of blastocyst in endometrial lining of uterus, Week 2 - Bilaminar germ disc formation, Week 3 - Trilaminar germ disc formation
What is gastrulation?
Formation of trilaminar germ disc
Outline process of formation of a morula from a zygote?
Day 3-4 post fertilisation Zygote divides via mitosis into smaller cells called blastomeres (these are called cleavage divisions) Once there are about 8 cells they begin to compact and form a morula A morula is still within the zona pellucida so is about the same size as the original zygote The morula moves down the uterine tube towards the uterus
What is morula?
Collection of cells (8-16) formed from zygote during cleavage divisions
Outline process of formation of a blastocyst from a morula?
The morula continues dividing until it becomes a blastocyst (32-64 cells) The cells form a fluid filled cavity known as a blastocoel which starts to appear in the centre of the morula At this stage, the outer layer of the blastocyst will start to differentiate into trophoblast (which eventually becomes the placenta) and the inner layer becomes the embryoblast (which becomes the embryo)
What is a blastocyst?
A ball of cells (32-64) made of two distinct cell layers (trophoblast and embryoblast) surrounding a fluid filled cavity
What is the trophoblast?
Outer layer of cells which will become placenta
What is inner cell mass of blastocyst?
Group of cells which will form embryo
Outline process of hatching and implantation of blastocyst?
Day 5 - Zona pellucida hatches from zona pellucida; It attaches to endometrial lining of uterus; The trophoblast of blastocyst differentiates into cytotrophoblasts and syncytiotrophoblasts
What is cytotrophoblast?
Inner cell layer of trophoblast
What is syncytiotrophoblasts?
Outer cell layer which invades endometrium and establishes future connections for nutrient exchange (eg glands and capillaries)
Outline process of bilaminar disc formation from blastocyst?
Day 6-7 Blastocyst is implanted in endometrial lining of uterus; Day 7-8 Inner cell mass of blastocyst differentiates into: Epiblast - upper layer which will form trilaminar disc (then embryo); Hypoblast - lower layer which will form extra embryonic structures such as yolk sac; Day 8: Small fluid filled amniotic cavity forms above epiblast; Day 9-10: Yolk sac forms from hypoblast; Day 11-12: layer of extra embryonic mesoderm forms between trophoblast and newly formed aminon and yolk sac; Extraembryonic coelum (cavity) forms which surrounds amniotic cavity and yolk sac
Structure of bilaminar disc?
Top layer - epiblast (will form trilaminar disc and then embryo); Bottom layer - Hypoblast (will form extraembryonic structures such as yolk sac)
What is extraembryonic coelom/ chorionic cavity?
Fluid filled space which forms in early embryonic development and surrounds developing embryo; Plays significant role in separating different layers of extraembryonic tissues
What is extraembryonic mesoderm?
Plays crucial role in development of extraembryonic membranes that support placenta; Particularly placenta, yolk sac and Chorion
What is gastrulation?
Formation of trilaminar disc from bilaminar disc
Outline process of gastrulation?
Week 3; 1)Primitive streak formation: A line of thickened epiblast cells form on the top all the way along midline of the bilaminar disc; 2)cells in epiblast move towards streak and dive down into embryo and form 3 germ layers: endoderm, mesoderm, ectoderm; 3)Primative node forms at the head of of the primitive streak. It acts as a control centre for development of embryo
What are the 3 layers of the trilaminar embryonic disc?
Ectoderm (external), Mesoderm (middle), Endoderm (inside)
What is derived from Ectoderm (Outer)?
Mostly external and nervous structures; -Nervous system; -Epidermis, hair, nails; -Sweat and sebaceous glands; -Retina and lens of eye; -Inner ear; -Mucous membranes; -Tooth enamel
What is derived from mesoderm (Middle)?
-Muscle; -Bones and cartilage; -Heart, blood vessels and blood cells; -Kidneys; -Connective tissues (tendons and ligaments); -Lymphatic system
What is derived from endoderm (Inner)?
-Epithelial lining of GI tract; -Liver and pancreas; -Lining of resp tract; -Bladder and urethra; -Thyroid and parathyroid gland; -Thymus
What is an extra embryonic membrane?
Structures that form outside of the embryo during early stages of development in womb
Give examples of extraembryonic membranes ?
Yolk sac, Amnion, Chorion, Allantois
What is Yolk sac?
First site of blood cell formation; Provides nutrients to embryo before placenta is fully functional
What is amnion?
Surrounds embryo (makes cavity filled with amniotic fluid)
What is chorion?
Becomes part of the placenta
What is allantois?
Becomes vascular connection between embryo and placenta
What is homeostasis?
Maintainence of a relatively constant internal environment in response to environmental changes.; Maintains various ‘levels’ throughout body - eg blood glucose, water levels, temperature and pH; Uses both nervous and endocrine systems
How does nervous system work in homeostasis?
Acts quickly to restore balance; Involved in immediate responses - eg shivering/sweating to cold/hot
How does endocrine system work in homeostasis?
Works slowly; Releases hormones into blood which travel to target organs and cause long lasting effects; Eg blood glucose control
Ideal body temperature?
37c
What are the 2 part of the nervous system?
Central nervous system and peripheral nervous system
What is in Central nervous system?
Brain and spinal cord
What is In peripheral nervous system?
Connects brain and spinal cord to the rest of the body; Spinal and cranial nerves; Sensory, motor and autonomic nerves
What is negative feedback?
Response decreases the effect of the original stimulus (usually to maintain constant internal environment - homeostasis)
What is positive feedback?
Response increases effect of original stimulus
Outline the process of negative feedback?
1)Stimulus (initial change) occurs; 2)Receptors detect change; 3)Receptors send messages to the control centre (usually brain or endocrine gland); 4)Control centre responds by releasing chemicals or hormones which will reverse the change; 5)Effector (such as muscle, gland or organ) responds to counteract change, bringing the body back to normal; 6)Body returns to normal range and negative feedback loop ends
Outline the process of positive feedback?
1)Stimulus (initial change) occurs; 2)Receptors detect change; 3)Receptors send messages to the control centre (usually brain or endocrine gland); 4)Control centre responds by releasing chemicals or hormones which will amplify the change; 5)Effector (such as muscle, gland or organ) carries out response to amplify the original change; 6)The cycle repeats, further intensifying original stimulus
Function of hypothalamus?
-Produces releasing hormones (eg gonadotropin releasing hormone) and inhibiting hormones (eg growth hormone - inhibiting hormone) …which act on anterior pituitary; -Regulates homeostasis; -Controls autonomic functions (eg heart rate); -Plays a role in emotional regulation and behavioural stress response
Function of anterior pituitary?
-Produces and releases a wide range of hormones including growth hormone, thyroid-stimulating hormone, follicule-stimulating hormone and luteinizing hormone; -It is regulated by releasing-hormones and inhibiting-hormones which are released from hypothalamus
Function of posterior pituitary?
-It stores and releases hormones produced by hypothalamus (doesn’t produce hormones); -Hormones synthesised in hypothalamus are transported down the axons of hypothalmic neurons to posterior pituitary. They are released into blood stream as needed.; -Releases eg: Anti-diuretic hormone (ADH) and oxytocin
What type of feedback is regulation of body temperature?
Negative feedback
What type of feedback is childbirth?
Positive feedback
Describe the negative feedback response when body temperature is too high?
1)Increase in body temperature (stimulus); 2)Thermoreceptors in skin and hypothalamus detect change; 3)Thermoreceptors send nerve impulses to hypothalamus; 4)Hypothalamus releases substances to initiate negative feedback response; 5)Effects eg: Vasodilation, Sweating, Increased resp rate; 6)As body cools towards normal, signals from thermoreceptors to hypothalamus reduce in intensity
Describe the negative feedback response when body temp is too low?
1)Decrease in body temperature (stimulus); 2)Thermoreceptors in skin and hypothalamus detect change; 3)Thermoreceptors send nerve impulses to hypothalamus; 4)Hypothalamus releases substances to initiate negative feedback response; 5)Effects eg: Vasoconstriction, shivering, increased metabolism; 6)As body warms towards normal, signals from thermoreceptors to hypothalamus reduce in intensity
The five standard steps of cell signalling process?
1)Biosynthesis and release of signal; 2)Signal shared to target cell (disseminate); 3)Signal is detected by receptor and transduction occurs; 4)Cell phenotype is altered (cell responds to signal); 5)Signal is terminated (it has been responded to)
Dissemination meaning?
To spread widely throughout body’s tissues and organs
Transduction meaning?
Process of converting something (eg energy/message) into another form
Ligand meaning?
Chemical messenger/molecule that binds to another molecule (on receptor) to produce changes in the cell
Examples of signalling molecules?
Hormones (endocrine), neurotransmitters (synaptic), cytokines (immune), growth factors
What is paracrine signalling?
When a cell produces signalling molecules which affect nearby cells by binding to their receptors
What is autocrine signalling?
When a cell produces signalling molecules that bind to its OWN receptors
What is a paracrine gradient?
Concentration change of signalling molecule as you move away from the cell releasing them
Question
Answer
How does the paracrine gradient effect cells?
How close the cell is to the signalling cell effects the response it will have. Eg if it is closer it may have a stronger response, or in some cases eg development it may have a different response. Eg in development, the paracrine gradient controls what type of cell it will become.
What is sonic hedgehog (SHH) signalling?
Sonic hedgehog signalling pathway is used to control how cells grow, where they move, and what they become during development. It works through a gradient system where cells respond differently depending on how much SHH signal they receive. This ensures tissues and organs develop in the right place with the right structure.
What is endocrine signalling?
The release of hormones into the blood stream by endocrine glands which target cells throughout the body, causing a variety of effects eg. Sex hormones, growth hormones.
Steps of synaptic transmission?
1) Action potential arrives down pre-synaptic neurone causing depolarisation. 2) This triggers voltage gated calcium channels to open, allowing calcium ions into pre-synaptic terminal. 3) This prompts synaptic vesicles containing neurotransmitter to move towards presynaptic membrane and fuse with it. This causes neurotransmitters to be released into synaptic cleft. 4) Neurotransmitters diffuse across synaptic cleft and bind to receptors on post synaptic cell. 5) This binding triggers a response in post synaptic cell.
What is synaptic plasticity?
Synaptic plasticity is the ability of connections between neurones to change depending on how much they are being used. This is important for learning things and remembering information.
What is long term potentiation in terms of synaptic plasticity?
Long term potentiation is when you use a synapse a lot - eg studying or practicing a sport. The 2 neurones are activated together frequently, so synaptic strength increases. More receptors are created on the post synaptic membrane, enhancing the response created.
What is long term depression in terms of synaptic plasticity?
Long term depression is when you don’t use a synapse a lot. The number of receptors on the post synaptic membrane decreases, so the synapse is weakened.
What can happen if you have abnormal synaptic plasticity?
Neurological disorders such as autism, Alzheimer’s, Schizophrenia, depression, epilepsy.
Why must a neurotransmitter be removed from a synapse?
To prevent continuous stimulation of post synaptic neurone.
What are the 2 main methods of removing neurotransmitter from synapse?
Enzymic degradation - breaking down neurotransmitter with enzymes. Reuptake into presynaptic neurone.
What are ligand gated ion channels?
Proteins in cell membrane which are like gates which open/close to allow ions in and out of the cell.
How do ligand gated ion channels work?
Ligand (eg neurotransmitter) binds to the channel, causing it to change shape and let ions into the cell. This changes the charge inside the cell, causing effects such as nervous conduction or muscle contraction.
Is the effect of a ligand the same on different types of receptor?
No, ligands can have multiple functions depending on the receptor they interact with.