1: Introduction to the Nervous System Flashcards
Neuron: Nerve
Bundle of axons of neurons wrapped in connective tissue.
Neuron: Dendrites
Sensory information comes in through these.
Neuron: Axon
Where electrical impulse is generated and propagates down the axon.
Neuron: Myelin
Fatty sheath/insulator which helps speed up the rate at which the electrical impulse is passed down the axon.
Integration in the Nervous System
A single neuron integrates all its many inputs (some inhibitory, some excitatory) to produce a single response in the form of a nerve impulse or action potential. This allows the NS to process a huge amount of info very quickly and produce appropriate responses.
Glial Cells: Role
Protective and supportive role to the neurons. 6 types - 4 in the CNS and 2 in the PNS.
CNS Neuroglia: Astrocytes
- Largest and most numerous
- Physically support neurons
- Wrap around capillaries and form the blood-brain barrier
CNS Neuroglia: Ogliodendrocytes
- Form a myelin sheath along axons in the CNS
- Myelinated axons permit faster transmission of information
CNS Neuroglia: Microglia
Help protect CNS via phagocytosis of waste, debris and pathogens.
CNS Neuroglia: Ependymal Cells
- Line the ventricles of the brain and the central canal of the spinal cord
- Secrete cerebrospinal fluid (CSF)
- Monitor composition of CSF and help circulate it
PNS Neuroglia: Schwann Cells
- Wrap around PNS axons
- Multiple Schwann cells form myelin sheath
- Also encases non-myelinated axons`
PNS Neuroglia: Satellite Cells
- Surround cell bodies of axons in the PNS
- Provide structural support
- Regulate passage of material between neutron soma and interstitial fluid
Membrane Potential
The inside surface of the membrane has a negative charge compared to the outside.
Comes about because intra and extracellular fluids have a different composition - creating concentration gradients.
Higher concentration of Na+ ions OUTSIDE cells compared to inside and vice versa for K+ ions.
Resting Membrane Potential
Potential difference when a cell is at rest, with the inside of the cell membrane negative with respect to the outside.
Depolarisation
The rapid reversal of the membrane potential from the inside negative at rest to inside positive and is what allows neurons to signal.
Open sodium channels.
Repolarisation
The return of the membrane potential to normal and the readiness to pass on another signal.
Open the potassium channels.
Nerve Impulse Conduction
A wave of depolarisation followed by repolarisation then moves rapidly along the axon as more and more sodium channels open.
Neurotransmitters
Chemical communication between neurons.
Synapse
The small gap between the axon of one neurone and the dendrite of another.
CNS: Brain
- Externally, grey matter (cell bodies) visible
- Internally, white matter (axons) interconnecting different areas of the brain
CNS: Spinal Cord
- Externally, white matter visible
- Grey matter in the centre of the cord
PNS: Spinal and Cranial Nerves
- 12 pairs of cranial nerves
- 31 pairs of spinal nerves
Sensory NS
Processes sensory information e.g. vision, hearing, somatic sensation (touch), taste and smell.
Motor NS
Contains motor nerves which conduct impulses from the CNS and PNS to the muscles, organs and glands e.g. peristaltic wave.
