Chapter 10 - NS Flashcards
Cells in the NS
- Neurons: respond to neural stimulus
- Neuroglia: protect, support, insulate and nourish neurons
- Don’t conduct electrical impulses but are much more numerous
Sensory:
- afferent neurons
- Detects sensory information, converts it into impulses and conducts it to the CNS
Motor
- Efferent Neurons
- Receives information from the CNS, transmits the message to effectors and causes action
Migranes
Occurs due to a period of excitation followed by unresponsiveness in particular neurons which stimulates the production of pain sensation in areas at base of the brain
- Signs: pounding head, nausea, light or sound sensitivity
- Can be caused by bright light, certain foods, lack of sleep, stress
Treatment:
Neuron Structures
- Cell body(soma): contains nucleus, cytoplasms
- Dendrites: branched receptor surfaces
- Axon: s
○ Axon hillock: cone shaped area of cell body from which axon arises
○ Collaterals: branches of axon
○ Axon terminal
- Synaptic knob: rounded ending
Schwann Cells
neuroglia of the PNS that wrap around some axons in layers
○ Myelin: mixture of fats and proteins
○ Myelin sheath
- Nodes of ranviers: gaps of nonmyelinated axons
Myelinated Axons
- Coated by a myelin sheath
- Makes up white matter in the CNS
- Produced by oligodendrocytes(brain) and Schwann cells(spinal cord)
- Makes up white matter in the CNS
Multiple Sclerosis
autoimmune disease in which the destruction of myelin sheaths leave scars(scleroses) behind which stop neurons from conducting impulses
2 types of Classifications of Neurons
Structural Classification: how many
- Multipolar
- Bipolar
- unipolar
Functional Classification: direction of impulse transfer
- Sensory
- Interneurons: link neurons within the CNS
- motor
Functions of Neuroglia
- Provide support for neurons
- Guide neurons into position
- Produce GF to nourish neurons
- Help support synapsis building
Types of Neuroglia
- Astroctyes: connect neurons to blood vessels
○ Part of the blood brain barrier- Oligodendorcytes: myelinate axons in the CNS and provide structural support
- Microglia: phagocytic cells which also provide structural cells
- Ependyma: help regyulate and circulate spinal fluid
- Schwann cells: produce myelin sheath and speed up nerve signal transmission
- Ganglia: support clusters of neuron cell bodies
Neuron Regeneration in the CNS
- Do not regenerate as there is no neurilemma acting as a guiding sheath
- Oligodendrocytes do not regenerate
Neuron Regeneration in the PNS
- Peripheral nerons can regenerate due to the presence of shwann cells and neurilemma which can provide the guiding sheath for a regrowing axon
Action Potential
a sequence of electrical events in an excitable cell involving changes in membrane potential to allow communication between cells
- cell membrane is normally polarized or internally negatively charged
Process of ACtion Potential
Resting membrane potential:
- About -70mV
Due to greater potassium inside the cell and greater sodium outside the cell
Depolarization:
- Stimulus of some sort opens up sodium channels, allowing a flood of Na into the cell
As NA moves into the cell, it stimulates nearby channels to open up, creating a moving action potential down the axon
Repolarization:
- Flood of Na into the cell stimulates K to move to the outside of the cell
- Creates a positive membrane potential inside the cell temporarily
Hyperpolarization:
- Na/K pump restores resting membrane potential back to a negative charge inside the cell, allowing the cell to be restimulated again
- Does this by moving 3Na outside the cell for every 2K moved inside
