15.1 Flashcards
What happens as species evolved?
Their cells become adapted to perform specialist functions
By specialising in one function , cells lost the ability to perform some other functions
What do different groups of cells each have?
Carry out their own function
Makes cell dependent upon each other to cary out functions they aren’t specialised in
Example of cells working together
Cells in reproduction
Depend on other cells to obtain oxgen for their respiration to provide glucose or remove their waste products
What are the two forms of coordination in animals as a whole?
- The nervous system
- The hormonal system
What does the nerve system use?
- They use nerve cells to pass electrical impulses along their length
- They stimulate their target cells by secreting chemicals known as neurotransmitter directly on them
- Results in rapid communciation betwen part of organisms
- Responses produced are often short-lived and restrictied to localised reigon of body
What is an example of nervous coordination?
Reflex action
e.g withdrawl of hand fom an unpleasant stimulus
What is the hormonal system?
- Produce chemicals (hormones) that are transported in blood plasma to their target cells
- The target cells have specific receptors on their cell-surface membrane - change of concentration of hormones stimulate them
- This results in slow, less specific form of communication between parts of organism
- Responses are often long-lasting and widespread
An example of hormonal coordination
Control of blood glucose concentration
Produces a slower response but has amore long term and widespread effect
Comparison of nervous system
- Communication by nerve impulses
- Transmission is by neurones
- Transmission very rapid
- Nerve impulses travel to specific parts of the body
- Response is localised
- Response is rapid
- Response is short-lived
- Effect is usually temporary and reversible
Comparison of hormonal system
- Communication is by chemicals called hormones
- Transmission by blood system
- Transmission is usually relatively slow
- Hormones travel to all parts of body , only target cells respond
- Response is widespread
- Response is slow
- Response is often lasting
- Effect may be permanent and irreversible
What are neurones?
(nerve cells)
Specialised cells adapted to rapidly carrying electochemical changes called nerve impulses from one part of the body to another
What are the parts of motor neurone?
- Cell body
- Dendrons
- Axon
- Schwann cells
- Myelin sheath
- Nodes of Ranvier
What cell body?
Contains all the usual cell organelles including a nucleus and large amounts of RER
This is associated with production of proteins and neurotransmitters
What is dendrons?
Extension of the cell body which subdivide into smaller branched dibres called dendrites that carry nerve impulses towards the cell body
What axon?
A single long fibre that carries nerve impulses away from the cell body
What is schwann cells?
This surround the axon
Protecting it and providing electrical insulation
They also carry out phagocyotsis (removal of cell debris)
Play a part of nerve regneration
Schwann cells wrap themselves around the axon many times so the layers of membrane build up around it
What is myelin sheath?
Forms of covering to the axon and is made up of the membranes of Schwann cells
These membranes are rich in lipid called myelin
Neurones with myelin sheath are called myelinated neurones
What is nodes of ranvier?
Constructions between adjacnet Schwann cells where there is no myelin sheath
The constructions are between 2 - 3 μm long
Occur every 1-3mm in humans
Whar are the three different neurones?
- Sensory neurone
- Motor neurone
- Intermediate or relay neurones
What are sensory neurones?
Transmit nerve impulses from receptor to an intermediate/motor neurone
They have one dendron that is often long
It carries impulses towards the cell body and one axon carries it away from cell body
What is motor neurones?
Transmit nerve impulses from an intermediate or relay neurone to an effector such as a gland or muscle
Motor neurone have long axon and many short dendrites
What is intermediate or relay neurone?
Transmit impulses between neurones
e.g sensory neurone to motor neurone
They have many numerous short processes
Diagram of labelled motor neurone
