The nervous system - neurons - ch 12 Flashcards
Describe neurons?
specialised nerve cells
What are neurons responsible for?
- commicating information in both chemical and electrical forms
Do neurons vary in size, shape and characteristics depending on their function and role?
yes
Name the three parts neurons have?
- cell bodies
- dendrite
- axon or nerve fibre
What do cell bodies contain?
nucleus
Describe dendrites and their role?
- hair-like structures that surround the cell body and which manage and direct incoming signals
What is the role of the axon and nerve fibre?
they guide the outgoing signals from the neuron.
What are axons covered in?
fatty sheath called myelin which acts to insulate the axon and facilitates the transmission of impulses.
How do neurons communicate?
by transmitting information both within the neuron and from one neuron to the next.
Where do neurons dendrites receive information from?
sensory receptors or other neurons
Where is the information from the the dendrites transferred to?
the cell body and then travels down the length of the axon in the form of an electrical signal known as an action potential. The point at which the message passes between two nerve cells is called a synapse.
Describe a synapse?
a small gap across which chemical neurotransmitters diffuse or electrical impulses connect to pass instructions to the dendrites of other neurons or to activate specialised sites called receptors on a target cell.
Is the target cell a specialised part of a muscle cell or a gland?
Yes
Can the electrical signal on occassion instantaneously connect across the space between the neurons and continue along its path?
Yes
What is the role of the chemical messenger (neurotransmitter)?
(neurotransmitter) diffuses across the synapse to reach the receptor sites of other neurons in a process that is slower than the electrical signal
Around how many neurotransmitter types are there?
around one hundred
Name 3 neurotransmitters?
- acetylcholine
- endorphins
- dopamine
What is the role of acetylcholine (neurotransmitter)?
it works with memory, muscle contractions and learning.
If a lack of acetylcholine in the brain is correlated, what is the name of the diagnosis?
Alzheimers disease
What is the role of endorphins?
They are connected with emotions and the perception of pain, fear and trauma. They reduce pain.
What is the role of dopamine?
This neurotransmitter relates to thought and feelings of pleasure
What is a deficit in dopamine related to?
Parkinson’s disease, excessive amounts are thought to be linked to schizophrenia
How classes of neurons are there?
three
Name the three classes of neurons?
- sensory neurons
- interneurons
- motor neurons
What is the role of a sensory neuron?
to receive information from the body’s internal and external sensory receptors and convert the messages received into electrical impulses for transfer to the central nervous system.
What is the role of the external sensory?
the external sensory receptors react as we look, listen, smell, taste, touch and feel
What is the role of the internal sensory?
the internal sensory receptors report on the condition of the internal organs, such as state of the bladder, the digestive system, blood pressure and osmolality.
Are there other receptors that respond to the positio of the body and its movements?
yes
What is the role of the interneurons?
to transfer messages and impulses to and from the sensory neurons and to and from other interneurons. Branching from the end of the interneurons are dendrites, which receive information by means of signals sent from the axon of another neuron.
true or false? Can interneurons only transmit information in one direction?
Yes
What is the role of motor neurons?
to send messages from the central nervous system to the muscles and glands to initiate an action or carry out a response.
What are most motor neurons stimulated by?
interneuronss, but some receive direct stimulation from sensory neurons.
