Topic 2: Body Balance Flashcards
What does the endocrine system do?
- maintains balance in the body through the
action of hormones
What is the endocrine system?
The endocrine system is made up of endocrine glands that secrete hormones which travel through the bloodstream to cells everywhere in the body. This allows for the maintenance of the internal environment in the body, or internal homeostasis
What does the endocrine system do?
It regulates, coordinates and controls:
1. growth and development
2. male and female development
3. how your body uses energy
4. Appetite
What is an endocrine gland?
A gland that secretes hormones into the bloodstream for transport around the body.
- same in males and females, except for the ovaries and testes.
What is a hormone?
chemical messengers that are secreted from the endocrine glands into the bloodstream for transport around the body
How do hormones “know” which cells are their target cells?
It is because target cells have special receptors that recognise the hormones and allow them to influence that cell.
What controls internal signalling?
Nerve Cells - are short acting but send a message quickly
Hormones - are long-acting but slower to be received.
What are target cells?
have receptors on the cell membrane of a cell that recognise hormones to initiate a response. It responds to the hormone when it binds to its receptors, triggering a specific cellular response
Role of the hypothalamus
- monitors the body for temperature, pH, and other conditions.
- signals the pituitary gland if conditions need to be corrected.
Role of the pituitary gland
- signals other glands to produce their hormones when needed
- found in the brain and receives signals from the hypothalamus.
Hormones released: pituitary gland
- Growth Hormone
- Too much - gigantism
- Too little - dwarfism - Antidiuretic hormone - stimulates kidneys to keep water
Role of the thyroid gland
- regulates metabolism and energy balance
Hormones released: thyroid gland
- Thyroxine - regulates body energy usage
- Calcitonin - regulates calcium and phosphate in the blood.
What does the thyroxine do?
- controls the rate of metabolic processes in the body and influences physical development.
Hormone Released: Adrenal Glands
- Adrenaline - stimulates heart rate, increases blood pressure, and dilates pupils (acts on multiple tissues).
- Cortisol: increases mental stimulation, and breaks down fat and protein to glucose. Involved in response to stress and anxiety
Role of Pancreas
- regulates blood sugar levels in the blood.
Define homeostasis
The body’s ability to regulate and maintain a stable condition inside your body, regardless of changes to the external environment
Name the 2 body systems that coordinate all the functions of the body
- the nervous system
- the endocrine system
3 Examples of homeostasis:
- body temperature at 37ºC
- the amount of water inside our body
- blood sugar levels
Why is it so important to maintain temperature?
The human enzymes work best at 37ºC, so if the body temperature changes too much, it could result in:
- heat stroke
- hyperthermia
- dehydration
- death
Why is it so important to maintain water levels?
If the amount of water in the body is wrong, cells can be damaged because too much water enters and leaves them, affecting their ability to function properly.
Why is it so important to maintain carbon dioxide levels?
increased CO2 levels would alter the concentration of CO2 and O2 and the cells wouldn’t receive enough oxygen which means they wouldn’t function properly.
SRBERN
Stimulus - what has happened?
Receptors - name the type of receptor
Brain - hypothalamus
Effector - fixes the problem
Response - counter-acts the problem
Negative Feedback - don’t want it to keep happening
What are the effectors involved if the body temperature is too low?
- Blood vessels will constrict
- Muscles will contract ( they will begin to shiver)
What are the effectors involved if the body temperature is too high?
- Sweat glands produce sweat
- Blood vessels dilate to release heat
What are the effectors involved if the blood-sugar levels are too high?
The pancreas produces more insulin which uptakes excess glucose from the blood to be stored as glycogen
What are the effectors involved if the blood sugar levels are too low?
The pancreas releases glucagon, which causes the liver to convert glycogen into glucose
how does the body maintain homeostasis?
- receptors - detect the changes
- control centre - recieve info and control the response
- effectors to produce a response
What is a negative feedback loop?
It is a response triggered by changed conditions and counteracts the change. It occurs to remove the original stimulus to maintain homeostasis.
Problem in Type 1 Diabetes
The immune system has destroyed beta cells, so no insulin is produced in the bloodstream to uptake excess glucose.
Problem in Type 2 Diabetes
The body cells that should take in glucose don’t, as they are resistant, causing glucose to remain in the bloodstream.
What is a positive feedback loop?
When a process keeps increasing its activity. It makes things happen faster or stronger until something big happens to stop it
Example of a positive feedback loop
Childbirth - The baby’s head pushing on the cervix leads to stronger contractions, which helps the baby to be born. Once the baby is born, the loop stops because the stimulus is no longer present
What controls the release of hormones?
- External Stimuli - via the nerves from the sensory organs in the nervous system
- Internal Stimuli - via nerves and other hormones from inside the body
Examples of Internal Stimuli
- Haven’t eaten for 6 hours
- Sick and develop a fever
- Pain from an injury
Examples of External Stimuli
- Hearing a loud noise
- Touching a sharp or hot object
- Tasting something sour
What goes wrong in hyperthyroidism
Too much thyroxine is produced which speeds up the body’s metabolism, leading to a range of symptoms:
- weight loss
- increased heart rate
- anxiety and irritability
Name the main phases of the cell cycle
- Interphase
- Mitosis
- Cytokinesis
Brief overview of what occurs in Interphase
- the cell grows, copies its DNA, and carries out normal functions
- makes preparations for mitosis
Why do cells divide?
In order to replace dead, damaged or infected cells. New cells are needed for growth, repair, and replacement
Define Cell Cycle
the series of events that cells undergo to divide and create two identical daughter cells
What happens in G1?
- the growth period before DNA synthesis
- makes proteins
- increases in size (getting bigger in mass)
What happens in S phase?
- all genetic materials are synthesised or replicated
- chromosomes are doubled but are still attached at the centromere
What happens in G2?
- period after DNA synthesis
- cell increases in size but by making organelles like mitochondria
How long is the interphase
Around 23 hours
How long does mitosis take?
Around 1 hour
Brief overview of what happens in mitosis
the division of genetic material to produce two cells with the same DNA
List 4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
What occurs in Prophase
- the nuclear membrane and nucleolus disappears
- centrioles migrate to poles of the cell
- chromosomes become visible
What happens in Metaphase?
- the duplicated chromosomes line up across the equator of the cell
- checkpoint at this stage
What happens in Anaphase?
- the sister chromatids separate
- they are pushed towards opposite ends of the cells by spindle fibres
- each chromatid moves away from its sister chromatid
What happens in Telophase
- the chromosomes begin to uncoil
- nuclear membrane reforms
- separation of chromosomes is completed
What happens in Cytokinesis
the division of the cytoplasm and organelles after mitosis.
Cytokinesis in Animals
cleavage furrow
Cytokinesis in Plants
A cell plate forms that will form into a cell-wall
What is the result of mitosis?
- two daughter cells that are genetically identical
- diploid
- have the same number of chromosomes as the parent cell
centriole
produces spindle fibres
What is semi-conservative replication?
In each new DNA double helix, one strand is from the original molecule, and one strand is new.
When is mitosis a bad thing
When cells reproduce when they are not needed
- these cells can take over but don’t function properly
- make copies without any control
- can result in cancer
What is asexual reproduction?
The process by which a single parent reproduces by itself
How is the cell cycle regulate to deal with problems?
The cell cycle has checkpoints that prevent cell division if the:
- Cell is short of nutrients
- DNA within the nucleus has not been replicated
- DNA is damaged
How do mutations result in a lack of control of the cell cycle?
Mutations in genes controlling checkpoints result in an out-of-control cycle. This unregulated cell cycle can result in uncontrolled division of cells leading to cancer
Cancer cell features
- large and abnormal nuclei
- not specialised (serve no functions)
- attract blood vessels and can grow in masses called tumours
When does DNA replication occur?
During the S phase
Why does DNA replication occur
To ensure that each daughter cell gets a copy of the genome, and therefore, successful inheritance of genetic traits.
Define Helicase
An enzyme that untwists the double helix of DNA by breaking hydrogen bonds.
Define DNA Polymerase
An enzyme that uses a parent strand of DNA to build a new daughter DNA strand
What is the name of the original DNA strands?
Template Strand
What is the name of the new DNA strand?
Daughter Strand
What is produced at the end of the process of DNA replication?
two DNA molecules which are identical to the original DNA
Define Chromosome
a strand or molecule of DNA
Define Gene
a segment of DNA that codes for a specific protein. A gene determines the traits of an organism
Define genome
an organism’s complete set of DNA, including all of it’s genes.
What is DNA?
a long, double-stranded molecule that contains the genetic information for living things.
Shape of DNA? What is it held together by?
- Basic Shape of a double helix/twisted ladder
- held together by hydrogen bonds
What are nucleotides? What is it composed of?
are the building blocks of DNA
One nucleotide is composed of:
- phosphate group
- deoxyribose sugar
- nitrogenous base
List the Base Pairings
Adenine + Thymine
Guanine + Cytosine
What is RNA?
a single-stranded molecule that plays a key role in the production of proteins
Where is RNA located
on a ribosome in the cytoplasm
Differences between RNA and DNA
- RNA is single-stranded whereas DNA is double-stranded
- RNA has ribose sugar whereas DNA has deoxyribose sugar
- RNA has the nitrogenous base Uracil, and DNA has Thymine
Similarities between RNA and DNA
- Both have four nitrogenous bases
- Both exhibit a phosphate backbone
- Both DNA and RNA are types of nucleic aids, which are essential for storing and transmitting genetic information
Define Proteins
are chains of amino acids that fold into specific structures that functions for a particular part of the body
Function of proteins
- give cells and tissues their shape and support
- speed up chemical reactions
- move substances in and out of the cell
What occurs in transcription?
DNA is copied into a molecule of RNA, called mRNA, by an enzyme called DNA polymerase
What occurs in translation?
It occurs on a ribosome in the cytoplasm where mRNA is decoded into amino acids, forming proteins essential for life functions
What are spindle fibres
Protein threads produced during mitosis to pull chromatids apart
What is DNA replication?
the process where a cell makes a complete copy of its DNA, before cell division, so that genetic information can be passed on from the parent cell to the daughter cell.
