Neurons Flashcards
What is special about nervous tissue?
- It is densely packed with cells such as neurons (less than 25% extracellular space).
What surround the neurons in the nervous system?
Glial cells.
What is the function of glial cells?
Provide support, nutrition, insulation and aid synaptic transmission in the nervous system.
What is the lifespan of neurons in the cerebral cortex?
They will live as long as you do (most of the time).
Most neurons are amitotic, what does this mean?
Once they specialise and take their given roles they lose the ability to divide, meaning they are irreplaceable.
What makes neurons irreplaceable?
They are amitotic (cannot divide once specialised so the number is fixed).
Describe the metabolic rate of neurons:
Very high, they require an abundant supply of glucose and oxygen, (25% of daily calories are consumed by the brains activity).
What is the basic structure of a neuron?
- Cell body,
- Dendrites,
- Axons,
What is the function of the cell body?
Contains cellular components found in typical cells such as mitochondria, ribosomes, cytoplasm, nucleus, ER’s and golgi.
What is the function of the dendrites?
Receive messages from other neurons and allow them to travel to the cell body.
What is the function of the axon?
Carry electrical impulses from the cell body to the axon terminals, (where neurotransmitters are released into the synapse).
What are the branch-like structures protruding from the cell body.
Dendrites.
Where is the nucleus of the nervous cell?
In the cell body.
How is the dendrite adapted to increase Surface Area?
They have small dendritic spines to increase SA.
What are the long tube-like structures that protrude from the cell body?
Axons.
Bipolar neuron cells are rare, where might they be found?
In the retina of the eye.
Where would unipolar neuron cells be found?
In sensory receptors.
What is the function of a sensory neuron?
To transmit impulses from sensory receptors towards the CNS.
Most sensory neurons are what ____polar?
Uni(polar) as they transmit electrical impulses one way.
What is the function of a motor neuron?
To move and impulse from the CNS to the rest of the body.
Motor neurons are mostly _____polar?
Multi(polar) as they
What is the fatty layer surrounding the axon?
The myelin sheath.
Which type of neuron transmits impulses towards the CNS?
Sensory receptors.
What is the function of the nucleus?
Controls cell function and contains all cellular DNA.
What is the function of the Schwann cell?
To produce the myelin that will form the sheath.
What part of the neuron acts as insulation to minimise the dissipation of electrical impulses?
The myelin sheath.
What part of the neuron speeds up electrical transmission?
The myelin sheath.
What are the functions of the myelin sheath?
To speed up electrical transmission by minimising the dissipation of electrical impulses.
What biological molecule is myelin?
Lipid (fat).
What are the gaps in the myelin sheath called?
The nodes of ranvier.
Relay neurons are mostly ___polar:
Bi(polar), as they act as a messenger between other neurons.
Which type of neurons are found in receptors such as the eyes, ears, tongue and skin?
Sensory neurons.
Match the following:
- Unipolar
- Bipolar
- Multipolar
- Relay
- Motor
- Sensory
Sensory = Unipolar. Relay = Bipolar. Motor = Multipolar.
Where are relay neurons found?
Between the sensory and motor neurons, in the brain and spinal cord.
What is the function of the relay neurons?
To allow other neurons to speak to each other, a messenger (bipolar).
What happens when the motor neurons are stimulated?
They send signals to the muscles causing them to contract and movement occurs.
Which type of neuron is directly responsible for muscle movement?
Motor neurons.
Describe the length of an axon:
The length has a high variation, can be very small or large enough to be seen by the human eye.
How do the nodes of ranvier speed up transmission?
They force the impulse to ‘jump’ across the gaps in the axon.
Roughly how many neurons does a human have and how many of these are in the brain?
Roughly 100 billion neurons, 80% of which are located in the brain (80 billion).
What is the general variation in size for a neuron?
Less than a millimetre to a metre long.
How quickly is information passed through neurons?
Information can travel through neurons at speeds exceeding 100 meters per second.
