Nat5 Biology - Key Area 2.1 and 2.2

What is mitosis?

Mitosis is the process of cell division.

What must any new cell that is formed carry?

Any new cell that is formed must carry the same genetic information as the parent cell to form a multicellular organism. This ensures each cell carries the information for growth and the development of all the characteristics of its species.

What are the five stages of mitosis?

Interphase, Prophase, Metaphase, Anaphase, Telophase

What happens in interphase?

Chromosomes replicate so that each is now double-stranded and made up of two identical chromatids attached at the centromeres.

What happens in prophase?

The nuclear membrane breaks down, and the double-stranded chromosomes become visible.

What happens in metaphase?

Chromosomes assemble at the equator of the cell and spindle fibres attach at the centromeres.

What happens in anaphase?

Spindle fibres contract, separating the sister chromatids to opposite poles of the cells.

What happens in telophase?

Sister chromatids are now called chromosomes. The cytoplasm divides and a new nuclear membrane forms. Two identical daughter cells are produced.

What is the purpose of mitosis?

Growth, Repair of damaged tissues, Replacement of dead or damaged cells

What does mitosis ensure?

Mitosis also ensures that the diploid chromosome complement of the cell is maintained.

What is the chromosome complement?

The chromosome complement is the number of chromosomes within the cells of different species.

What are diploid cells?

Diploid cells (every other cell other than sex cells) have two matching sets of chromosomes which are replicated during cell division.

What are stem cells?

Stem cells are cells in animals which are unspecialised.

What does it mean for a cell to be unspecialised?

This means that they have no specific role within the organism but have the potential to become many different cell types.

What can stem cells do?

Stem cells can become specialised cells or can divide to self-renew (produce more stem cells)

What are stem cells used for?

Stem cells are used in the growth and repair of organisms.

Where do stem cells come from?

Stem cells are obtained from embryos at a very early stage of development. These cells can then be used to treat a variety of conditions within the body. Tissue stem cells can also be found in different parts of the body throughout life. Unlike embryonic stem cells, they are limited to the type of cells they can produce.

E.g Blood stem cells can only replace the various types of cells in the blood.

What are specialised cells?

Specialised cells are cells that have specific functions within an organism. E.g red blood cells

Level of organisation

specialised cell ---> tissue ---> organ ---> organ system ---> organism

What are tissues?

Tissues are groups of specialised cells that carry out particular functions.

What are organs?

Organs are body parts that are made of several different types of cells/tissues and carry out one or more particular functions.

What are organ systems?

Organ systems are groups of organs which can work together in organ systems such as the circulatory system or the respiratory system.

What is the Central Nervous System made of?

The brain and the spinal cord.

How are messages sent from all over the body to the Central Nervous System?

Via electrical impulses and this is incredibly rapid.

What is the brain made up of?

Several different regions, each with its own specialised functions.

What does the brain control?

Overall activity within the organism.

Cerebrum

Controls conscious thought, memory and intelligence

Cerebellum

Controls muscle co-ordination and balance

Medulla

Controls breathing and heart rate

What are the three types of neurons?

Sensory neurons, inter neurons, motor neurons (SIM)

What type of impluses carry messages along these neurons?

Electrical

Sensory Neurons function

Sensory neurons pass the information to the CNS

Inter Neurons function

Inter neurons operate within the CNS, which processes information from the senses that requires a response

Motor Neurons function

Motor neurons enable a response to occur at an effector (muscle or gland)

First stage in reflex arc

The sensory neurons pass the information in the form of an electrical impulse to the CNS.

Second stage in reflex arc

CNS processes information from the senses which require a response. Electrical impulses are sent through inter neurons which are only found in the CNS.

Third stage in reflex arc

The appropriate response is sent as an electrical impluse from the CNS via a motor neuron to produce a response in the effector.

What is a synapse?

Gap between neurons

How does information pass across a synapse?

An electrical impulse travels along the neuron until it reaches the end of the cell. The electrical impulse is converted into a chemical impulse which diffuses across the synapse. When the chemical reaches the next neuron, it is converted back into an electrical impulse.

What is the purpose of reflexes?

Reflexes are there to protect the body from harm. Reflexes do not involve the brain as this slows down the reaction rate.

What are hormones?

Hormones are chemical messengers that are released by endocrine glands and travel in the bloodstream.

What is a target tissue?

A target tissue has cells with complementary receptor proteins for specific hormones, so only the target tissue will be affected by these hormones.

Endocrine glands

Pancreas, Testes, Ovary

What hormone does the pancreas gland produce?

Insulin

What hormone does the testes gland produce?

Testosterone

What hormone does the ovary gland produce?

Oestrogen

What is the target organ for insulin?

Liver

What is the target organ for testosterone?

Various

What is the target organ for oestrogen?

Uterus

What is the effect of insulin on the body?

Control of blood glucose regulation

What is the effect of testosterone on the body?

Control of male sexual development

What is the effect of oestrogen on the body?

Repairs uterus lining following menstruation

What would make blood glucose increase?

A meal

What would make blood glucose decrease?

Exercise

Response to an increase in blood glucose

Blood glucose level increases. The pancreas receptor cells detect this and release insulin into the blood. Insulin binds to target cells in the liver and glucose is converted to glycogen which is stored in the liver. Blood glucose level returns to normal.

Response to a decrease in blood glucose

Blood glucose level decreases. The pancreas receptor cells detect this and produce glucagon which is released into the blood. Glucagon binds to target cells in the liver and glycogen is broken down into glucose. Blood glucose level returns to normal.

low blood glucose memory aid

when glucose is gone you need glucagon

high blood glucose memory aid

to turn glucose into glycogen, what you need is insulin