Introduction to the nervous system and resting membrane potential Flashcards
What is the Nervous system divided into?
The central nervous system (brain and spinal cord)
The peripheral nervous system (cranial nerves, spinal nerves and ganglia)
What are the further divisions of the PNS?
The afferent division brings sensory info to the CNS (to bring in)
The efferent division consists of motor commands from the CNS (to bring out)
What are the further divisions of the Efferent system?
- Somatic nervous system (voluntary) consists of skeletal muscles
- Autonomic nervous system (involuntary) consists of smooth muscle, cardiac muscles and glands
The autonomic nervous system then divides into the sympathetic system (fight or flight) and parasympathetic system (rest and digest)
What are Neurons and neuroglia?
Neurons are excitable cells that transmit electrical signals. They communicate via synapses and are a functional unit of the nervous system. 100 billion exist in the human brain
Neuroglia are supporting cells for neurons. They support and insulate, and are more numerous than neurons (10 x 100 billion in the human brain)
What features are in the structure of a Neuron?
- Cell body, or Soma (nucleus and organelles)
- Dendrites (receive information)
- Axons (send information as electrical signals, or action potentials)
- Axon hillock (where action potentials start)
- Axon terminals (releases neurotransmitters to communicate with other cells)
What can Neurons be classified into?
Bipolar neurons have two processes (axon and dendrite; dendrite connect directly to cell body), and are present in special senses (retina and olfactory system)
Unipolar neurons have a single fused process (axon and dendrites), with the cell body placed to the side (axons on either side). Most of the process is based on the axon, and are present as mostly sensory neurons
Multipolar neurons have multiple processes (two or more dendrites and one axon; dendritic branches connect directly to cell body) and are present as mostly motor neurons
What are the classifications of Neurons by their function?
- Sensory/afferent (neurons sending sensory info to the CNS)
- Motor/efferent (neurons sending sensory info from the CNS)
- Interneurons (link sensory and motor neurons together, mostly in the CNS)
What is the difference in terminology between the PNS and CNS?
Bundles of axons in the PNS is called nerves, and in the CNS is called tracts
Clusters of neuronal cells bodies in the PNS is called ganglia, and in the CNS is called nuclei
What are the types of Neuroglia and where are they found?
Schwann cells and satellite cells are found in the PNS
Oligodendrocytes, astrocytes, ependymal cells and microglia are found in the CNS
What is Myelin?
Myelin protects and electrically insulates axons, and increases the speed of electrical conduction
It is created by Schwann cells in the PNS and oligodendrocytes in the CNS
One Schwann cell can myelinate an axon in the PNS, whereas one oligodendrocyte can myelinate as many as 60 axons in the CNS. Overall, many Schwann cells or oligodendrocytes are needs to myelinate an axon
What is Resting membrane potential, and what creates it?
Resting membrane potential is a balance between concentration gradient, electrical gradient and permeability for each ion, or the voltage all body cells have (a separation of opposite charges across the plasma membrane)
It can range anywhere from -50 to -100v depending on the cell. The voltage is negative because the inside of the cell is negative compared to the outside
The ICF and ECF are electrically neutral, so the voltage is only present on each surface of the cell membrane
Diffusion of ions (especially K+ ) through ‘leakage channels’ creates the resting membrane potential (the plasma membrane has more leakage channels for K+ than Na+)
What are the basic principles of electrical activity?
- Opposite charges (+ or -) are attracted to each other; charges of the same type repel each other (+ and +)
- Separating opposite charges requires energy
- Opposite charges can move freely towards each other through a conductor (water)
- Opposite charges are prevented from moving towards each other through an insulator (the plasma membrane)
What is the Resting membrane potential when the K+ gradient becomes balanced?
-90mv (the membrane is highly permeable to K+, so can easily flow in and out)
What is the Resting membrane potential when Na+ moves back into the cell?
-70mv (reduces the potential slightly by creating small Na+ permeability)
Why is the Resting membrane important?
From the potentials, neurons and muscle cells can have energy to do “work”
These are called excitable cells
They do this by changing the permeability of the plasma membrane to Na+ and K+ to disrupt the membrane potential
