Homeostasis (B10, B11, B12) Flashcards
What two organs make up the CNS? (central nervous system)
Brain and spinal cord
Why are reflex actions important?
For fast reactions to ensure survival
Why are reflexes so fast?
- Only 2 synapses (3 neurones)
- Unconscious action
What is homeostasis?
Keeping the internal conditions of an organism constant
What are three main conditions controlled by the body?
- Blood sugar
- Body temperature
- Water levels
Describe the general pathway of a control system
Stimulus –> Receptor –> CNS –> Effector –> Response
What is an effector?
Muscles or glands that bring about a response
What is a receptor?
Cells that detect stimuli
What is the coordination centre?
Areas that receive and process information (usually the CNS)
What is a synapse?
A gap between two neurones, allowing impulses to cross
What do neurones do?
Carry electrical impulses around the body
Describe the structure of a neurone
- Dendrites (carry impulses towards the cell body)
- Axon (carries impulses away from the cell body)
- Myelin sheath (around axon to speed up impulses)
Describe the 3 types of neurone
- Motor neurone
- Sensory neurone
- Relay neurone
Compare sensory and motor neurones
- Sensory neurones have cell bodies on their sides, whereas motor neurones have cell bodies on the end
- Sensory neurones connect to receptors, whereas motor neurones connect to effectors
- They both have axon
- They both have myelin sheaths, etc.
What are nodes of Ranvier?
Gaps along the myelin sheath, aid the transmission of impulses along the axon
What is the cornea?
A clear, tough coating on the front of the eye