Chapter #12 - Coordination & Response Flashcards
Stimuli
Changes in the enviornment that can be detected by organisms.
Receptors
Cells or groups of cells that can detect stimuli.
Effectors
Parts of the body that respond to stimulus (e.g. muscles and glands)
Coordination
The way that receptors detect stimuli and pass informationto effectors.
What are the 2 ways that most animals pass on information?
Nerves and hormones
Nerves
The fastest method. Part of the nervous system.
Hormones
Slower, but still important. These chemicals are part of the endorcine system that we will learn about later.
What are neurones?
Specialised cells in the human body which conduct electrical impulses quickly. There are several types.
Motor neurone
Transmits electrical impulses from the central nervous system to an efector.
What are the features of motor neurons?
- Typically long
- Have thin fibres of cytoplasm that streach out from the body.
What is the longest fiber in the motor neuron?
The axon
What is the shortest fiber in the motor neuron?
Dendrites
How long can axons be?
1 meter
What is the function of dendrites in motor neurons?
Dendrites pick up electrical signals called nerve impulses from other neurones nearby.
What is the function of myelin sheath?
Insulates the nerve fibres so they can carry signals even faster.
What are the 2 nervous systems which all mammls have?
- Central nervous system (CNS)
=> The brain and the spinal chord - Peripheral nervous system (PNS)
=> Other nerves in the body
What is the main function of (CNS)?
To coordinate the electrical impulses travelling through the nervous system?
What does CNS stant for?
Central nervous system
What does PNS stand for?
Peripheral nervous system
What is the PNS made of?
It is made of nerves that that spread out from the CNS. Each nerve contains hundreds of neurones. It also includes the receptors in our sense organs.
Reflex arcs
The pathway along which an electrical impulse is passed (sensory neurone/relay neurone/motor neurone).
What are important notes about reflex arcs?
- They are involuntary.
- They are as useful as they are fast.
- Your brain is made aware of them, but you only realise what is happening after the impulse has been sent to your muscles.
What is the explanation of a reflex arc very simply?
- Receptor
- Sensory neuron
- Direction of travel of electrical impulse
- motor neuron
- effector
Explain the reflex arc of touching a hot plate.
- Hand touches hot plate.
- Sensory receptor in hand detects the hot stimulus.
- Receptor starts off an electrical impulse.
- Electrical impulse travels to the spinal chord along the axon from receptor cell.
- This cell is called a sensory neuron because it is carrying an impulse fromfrom a sensory receptor.
- In the spinal chord, neuron passes impulse to several other neurons. These are called relay neurons because they pass on the impulses.
- relay neurons pass the impulse to the brain, as well as the motor neuron that will pass it on as to an effector.
- Impulse passes down axon of a motor neuron to arrive at effector.
- Arm muscle contracts.
- Hand is pulled away.
What is the description of a sensory neuron?
Long dandrites, short axons
What is the function of a sensory neuron?
Takes informations from our sences to the CNS.
What is the description of a motor neuron?
Short dandrites, long axons.
What is the function of a motor neuron?
Carry impulses away from CNS, towards PNS.
What is the description of a relay neuron?
Short dendrites
What is the function of a relay neuron?
Only in eyes, brain and spinal chord.
Synapse
A junction between 2 neurons in order for a nerve impulse to be passed from one neuron to the next, it needs to cross a synaptic gap (a tiny gap between two neurons at a synapse).
What is inside the axon?
Inside the axon there are hundreds of tiny ventricles (very small vacuoles).
What do vesicles in the axon contain?
Vesicles contain neurotransmitters - chemical molecules that diffuse acrossthe synaptic gap to set up ans electrical impulsefor the next neuron.