Structure And Function Of Neurons Flashcards
Neurones
Specialised cells that carry nervous impulses around the body
Allows the senses to communicate with the brain and the brain to coordinate responses
What do neurones consist of?
- a cell body
- with one or two axons extending from the cytoplasm
- The axons are wrapped in sheaths of myelin protein
- In addition, tiny branches extend from the end of axons and from the cell bodies of motor neurones called Dendrites
Cell body
The cell body controls the nucleus
Axons
Carries nerve impulses away from cell body AND transmits the pulse over LONG distances
Dendrites
Receives nerve impulses and sends them towards body
What does white matter mostly consist of?
Axons
What does grey matter mostly consist of?
Dendrites
Glial cell
Provides structural support
Sensory neurones
Takes messages from sensory receptors in skin/specialised sense organs to the brain.
The cell body sits half way along the axon and there are no dendrites on the cell body
Motor neurones
Have many dendrites protruding from cell body.
Adapted to take impulses from CNS to effectors
Interneurones
Neurones that connect the sensory neurones to the motor neurones.
They are entirely contained within one structure, the brain
What does the cell body consist of?
- nucleus and cytoplasm
- Has many ribosomes which make proteins that act as neurotransmitters at gaps called synapses.
- Synapses may allow or prevent signals passing from one neurone to the next.
- Many mitochondria - provides energy for active transport which helps maintain electrical potential and reabsorb neurotransmitters.
Neurotransmitters
Protein messengers that jump synapses
What are axons bundled together to form?
Nerves
What are axons surrounded by?
A myelin sheath - wrapped like a Swiss roll!
The sheath insulates the axon and increases the speed of impulse conduction from node to node
What would happen if an Axon leaked out signals?
Confusion would arise as signals jumped from neurone to neurone
- the signals would become weaker and weaker as they travelled along the axons
What happens to the signals along the axons - what happens next?
Electrical impulses transmit signals along the axons
Neurotransmitters take the information from one dendrite of one cell across the synapse to the dendrite of the next axon.
What are nodes
At short intervals, myelin is pinched into sausage shaped pieces called nodes
What is the function of nodes? (Myelin)
Speeds up nervous transmission, the electrical impulses travel much faster by jumping from node to node.
Myelin stops sodium and potassium ions crossing the membrane, so the impulses rush along the tiny gap in the myelin where ion exchange can occur.
Complete the sentence :
The larger the …. the faster the … travels
Diameter
Impulse
What happens to the nerve connections when the myelin sheath develops?
Nerve connection improves
Can lack of myelin have severe consequences?
Yes - multiple scleorosis
What is the function of glial cells?
Cleans out debris and excess materials
(Removes debris by phagocytosis)
Supports neurones by providing support and nutrition
Produces myelin sheath
Maintains a homeostatic environment around the neurones.