The Nervous System Flashcards
What are the two divisions of the nervous system and what do they contain/what are their tasks?
Central nervous system: The brain and spinal cord
Receives information from the PNS. This information is either ignored, triggers a reflex or is evaluated.
Peripheral nervous system:
All nerves and ganglia outside of the brain and spinal cord. The PNS’s job is to relay information to the CNS via sensory neurons. Motor neurons in the PNS are used to relay information from the CNS to muscles and glands.
What are the three types of neurons and their characteristics?
Multipolar neurons:
- many dendrites and a single axon
- most motor neurons
Bipolar neurons:
- one dendrite and one axon
- common in sensory organs
Pseudo-unipolar neurons:
- has a single process extending from the cell body
- it divides into two: one extends to the periphery, the other to the CNS
What is a glial cell and what are the 4 types in the CNS?
Mention the single relevant type in the PNS.
Glial cells are supporting cells of the PNS and CNS and do not conduct action potential. They have the ability to divide.
Astrocytes:
- participate in the blood vessel endothelium forming the blood brain barrier
Ependymal cells:
- line the fluid-filled cavities in the CNS
- some produce cerebrospinal fluid, others use cilia to help move the CS fluid through the CNS
Microglia:
- immune cells of the CNS, protect the brain by removing bacteria and debris
Ogliodendrocytes:
- Provide myelin for insulation of axons
Schwann cells in the PNS produce the myeling sheaths of the axons.
What is white and gray matter?
White matter: bundles of parallel axons with their myelin sheaths. White matter of the CNS form nerve tracts, while white matter of the PNS consists of bundles of axons ++ that form nerves.
Gray matter: groups of neuron cell bodies and their dendrites, very little myelin. Grey matter in the CNS could be for example the brain cortex. Grey matter in the PNS: ganglion (clusters of cell bodies)
What is a synapse?
A junction where the axon of one neuron interacts with another neuron or with cells of effector organ (eg: muscle or gland)
Describe what happens at the presynaptic terminal.
When action potential reaches the terminal, voltage-gated Ca^2+ channels open. Influx of Ca^2+ causes the release of neurotransmitters by exocytosis from the presynaptic terminal.
The neurotransmitters then diffuse across the synaptic cleft and bind to specific receptor molecules on the postsynaptic membrane.
The binding of neurotransmitters can cause chemically gated channels for Na+, K+ or Cl- to open or close, depending on which neurotransmitter is released.
Outline the consequences of the opening of the chemically gated channels for Na+, K+ and Cl- in the postsynaptic membrane.
Opening of the Na+ channels would cause the membrane to depolarize as Na+ would rush into the cell.
Opening of K+ would cause K+ to rush out, making the inside of the cell hyperpolarized. Opening of Cl- would also hyperpolarize the cell, as it would rush in and make the inside of the cell more negative.
What is the function of a myelin sheath and which glial cells produces it?
Myelin sheaths insulate the axons and prevents ion movement across the cell membrane. The ion movement can therefore only occur at the nodes of Ranvier. Myelination of axons increases the speed and efficiency of action potentials.
Describe the reflex arc that activates if you touch a hot stove.
Sensory receptors sense the pain, and an action potential is produced. The action pot. is conducted by sensory neurons to the spinal cord. The sensory neuron will synapse with an interneuron, which will then convey the information to a motor neuron. The motor neuron brings the action potential to muscles in your arm that will contract to pull away from the stove.
Describe the two simplest neuronal pathways.
Diverging pathways:
- one neuron (axon) diverges and leads its action potential into two postsynaptic neurons
Converging:
- two or more neurons synapse with the same postsynaptic neuron
Describe summation and the two types of summation.
Sometimes a single presynaptic action potential isnt enough to reach the threshold in the target cell. Summation of signals in neuronal pathways allows integration of multiple subthreshold local potentials. They can then add up to trigger the threshold.
Temporal summation:
- a single input fires rapidly enough that its action potentials add up to reach the threshold
Spatial summation:
- local potentials from different locations on the postsynaptic neuron meet, eg. from a converging pathway
What are the basic similarities and differences between the sympathetic and parasympathetic nervous system?
They are both a part of the autonomic nervous system, ie. the part of the nervous system that is not controlled by will. Sympathetic = fight or flight - faster heart rate and breathing rate - releases glucose - digestion and bladder less active - dilates pupils
Parasympathetic = rest and digest
- slower heart- and breathing rate
- stores glucose
- digestion and bladder more active
What is a ganglion?
A cluster of neuron cell bodies in the PNS
