| The two main functions of coordination in animals | - The nervous system
- The hormonal system |
| The nervous system | - Uses nerve cells to pass electrical impulses
- Stimulate target cells by secreting neurotrans. directly on to them |
| The hormonal system | - Produces hormones that are transported in the blood plasma to target cells
- Target cells have specific receptors on cell-surface membrane
- Change in the conc. of hormones stimulates them |
| Hormonal system Vs nervous system (HORMONAL SYSTEM) | - Communication by chemicals, hormones
- Transmission by the blood system
- Transmission slow
- Response slow
- Response widespread
- Response long-lasting
- Effect may be permanent + irreversible |
| Hormonal system Vs nervous system (NERVOUS SYSTEM) | - Communication by nervous impulses
- Transmission by neurons
- Transmission rapid
- Response rapid
- Response localised
- Response short-lived
- Effect is usually temporary + reversible |
| Neurones meaning | - Specialised nerve cells
- Adapted to rapidly carry electrochemical changes called nerve impulses from 1 part of the body to another |
| What motor neurones are made up of in mammals | - A Cell body
- Dentrons, dendrites
- An axon
- Schwann cells
- A myelin sheath
- Nodes of Ranvier |
| A cell body | - Contains all the usual cell organelles
- Nucleus + rough endoplasmic reticulum
- Associated with the production of proteins + neurotransmitters |
| Dentrons, dendrites | - Extensions of the cell body which subdivide into smaller branched fibres, dendrites
- Carry nerve impulses towards the cell body |
| An axon | - Single fibre that carries nerve impulses away from the cell body |
| Schwann cells | - Surround axon, wrap themselves around it many times
- Protecting it + providing electrical insulation
- Carry out phagocytosis (the removal of cell debris), play part in nerve regeneration |
| A myelin sheath | - Forms a covering to the axon
- Made up of membranes of the Schwann cells
- These membranes are rich in a lipid, myelin
- Neurones with a myelin sheath are called myelinated neurons |
| Nodes of Ranvier | - Constriction between adjacent Schwann cells
- Where there is no myelin sheath
- Constrictions are 2-3 micrometers long
- Occur every 1-3 mm in humans |
| Different types of neurones | - Sensory neurones
- Motor neurones
- Intermediate or relay neurones |
| Sensory neurones function | - Transmit nerve impulses from a receptor to motor neurone
- Have 1 dendron that is often very long
- Carries impulse towards the cell body
- 1 axon that carries it away from the cell body |
| Motor neurones function | - Transmits nerve impulses from a relay neurone to an effector
- Have long axon, many short dendrites |
| Intermediate or relay neurones function | - Transmit impulse between neurones
- Like from sensory to motor neurones |
