body balance Flashcards
what is homeostasis
The body’s ability to maintain a constant internal environment, even when there are changes in the external environment.
What are some of the conditions in the body that need to be kept constant?
body temperature at 37°C
the amount of water inside our body
blood sugar levels
How does the body maintain homeostasis?
the negative feedback loop
Describe an example of negative feedback
When it gets cold outside (stimulus) you shiver (response) and keep the temperature inside your body from dropping.
the stimulus response model order
stimulus, receptor, control centre, effector, responce
What is a Negative-Feedback Loop?
Aims to reverse the effects of a stimulus
What is a Positive-Feedback Loop?
Aim to increase the effects of a stimulus
what is the role of the endocrine system
to release hormones (chemical messengers), from endocrine glands, into the bloodstream.
hypothalamus
detects change and signals the pituitary gland
what does the endocrine system regulate
things like growth, water balance, reproduction and metabolism.
what are the endocrine glands
Adrenal gland, pituitary Gland, pancreas, Thyroid Gland, Ovaries, Testes
Adrenal gland
Hormones Released: Adrenaline and Cortisol
Function: Stress response, blood pressure, emergency response
Pituitary Gland “Master Gland”
Hormone Released: Releases many including Growth Hormone
Function: Works closely with Hypothalamus
Pancreas
Hormone Released: Insulin and Glucagon
Function: controls blood glucose levels.
Thyroid gland
Hormone released: Thyroxine
Function: Metabolism & body heat
Ovaries
Hormone released: Estrogen and Progesterone
Function: Menstruation and pregnancy
Testes
Hormone released: Testosterone
Function: Production of sperm
How do these hormones identify their target cells?
Cell surface receptors. Example: Glucagon is released by the pancreas when blood sugar levels drop. The glucagon recognise the receptors on the liver cells, instructing them to cause an increase in blood glucose.
Example of endocrine disorder
diabetes
DNA
contains the genes which code for a specific protein
What are Chromosomes
tightly coiled, organised pieces of DNA
What are genes
Genes are segments of DNA, they are made of nucleotide sequences.
What do genes code for?
proteins
What is the difference between a gene and a genome.
A gene is a specific segment of DNA, and a genome is the entirety of the genetic material inside an organism.
What is DNA made up of
made up of repeating monomers, called nucleotides
What is RNA
Is single-stranded and does not have to stay in the nucleus.
What is the structure of RNA?
RNA contains nucleotides, with ribose sugar instead of deoxyribose sugar in dna. the base pairs are A and U, C and G
What is the purpose of RNA
To read the DNA code, copy it and take the information out of the nucleus.To make proteins at the ribosomes !
DNA → RNA → Protein
transcription and translation
Transcription
it is in the nucleus, DNA → RNA
Translation
It is in the ribosome, RNA → protein(chain of amino acids)
RNA vs DNA
RNA: can leave the nucleus, Contains Uracil, Single stranded, Ribose sugar
DNA: Can NOT leave the nucleus, Contains Thymine, Double stranded, Deoxyribose sugar
What are the three main phases of the cell cycle
Interphase, mitosis, cytokinesis
Interphase
Longest period of cycle,
Normal cell functions (existing),
- G1
- S - replication of DNA
- G2
Mitosis
PMAT
-cell divides nuclear content
-prophase, metaphase, anaphase, telophase
Cytokenesis
Final split and formation of new, identical cells
G1
Growth of cell before the DNA is replicated
S
DNA replicated using DNA polymerase (enzyme)
G2
Final growth period before cell divides into two, through Mitosis
DNA replication is semi-conservative
Each new DNA molecule contains one of the original strands.
Mitosis (cell division)
Now that the cell contents have doubled, it is time for the cell to divide into two identical, daughter cells
Stages of mitosis
Prophase, metaphase, anaphase and telophase
Prophase
Chromosomes become visible
Nucleus membrane disappears
Centrioles begin to move to poles
Metaphase
Chromosomes line up at equator
Spindle fibres are attached to centromeres
Anaphase
Spindle fibres pull sister chromatids apart
Telophase
Chromosomes are separated
Nuclear membrane reforms Cell plate or cleavage furrow forms
Cytokinesis (final stage)
The final split.
in plants: Cell plate forms and will become the new cell wall
In animals: Cleavage furrow forms, pinching the cells apart
What is produced at the end of the process of DNA replication?
two identical new DNA molecules.
