Brain anatomy Flashcards
What is a receptor protein?
- A protein that is sensitive to signals and is able to transfer a signal
- They are either ionotropic or metabotropic
What is an ionotropic receptor?
- Receptor protein that is an ion channel
What is a metabotropic receptor?
- receptor protein
- IS NOT AN ION CHANNEL
What is the mode of operation of a metabotropic receptor?
- Triggers an intracellular signaling cascade that involves G Proteins
- triggers intracellular signals to catalyze chemical reactions
What are the most frequent effects of the action of metabotropic receptors?
- change in gene expression
- opening or closing of g protein-gated ion channels
- secretion of substance from the cell
- Cell division
What is the metabolism?
- ensemble of chemical reactions that occur inside of the cell
What is a G-Protein?
- A protein that uses GTP instead of GDP as a source of energy
What does it mean for a g protein to be “on”?
- bound to GDP
- Can trigger chemical reactions
When is a g-protein considered as being “off”?
- when it has transformed the GDP in GTP
How does GTP become GDP?
The g-protein pries off the third phosphate groupe to use it as a source of energy
What is the course of action of metabotropic receptor signaling?
1) A metabotropic receptor binds to its ligand
2) the conformation of the receptor changes and it becomes favorable for the g-protein’s exhange of GDP for GTP
3) exchange occurs
4) the g-protein dissociates its alpha subunit, which bears the GTP
5) The alpha unit diffuses away
6) the alpha unit now activates downstream enzymes to allow metabolic reactions. It can also activate g-protein gated ion channels
7) the gtp molecule is metabolized into gdp
8) Deprieved of its supply of energy, the alpha subunit goes back to the rest of the molecule
What is a g-protein ion channel?
- ion channel that is gated by g proteins
How is a g-protein gated ion channel opened?
1) a neurotransmitter binds to the metabotropic recepor
2)Activated g proteins transmit the message intracellularly
3) The neighbouring ions channels therefore know they need to open
Where can the different types of synapses form?
1) dendrites (dendritic shafts)
2) dendritic spines
3) soma (cell body)
4) axoaxonic synapses
Where are situated the synapses that can have the greater impact on neuronal activity?
- on the soma (can override everything that happens in the axon)
Which emplacement of synapses have as a goal to cause an action potential?
- dendrites
- dendritic spine
- soma
What are axoaxonic synapses?
- synapses that are created by the apposition of one neuron’s terminal button on another neuron’s terminal button
What is the purpose of an axoaxonic synapse?
- Regulate the amount of neurotransmitters the second neuron will release (the one on whose terminal button of the other neuron is appositioned)
What are the two possible effects of an axoaxonic neuron?
- Presynaptic inhibition
- Presynaptic facilitation
What is presynaptic inhibition?
- hyperpolarization of the axon terminal of the neuron that is supposed to independently release neurotransmitters
- voltage gated calcium channels either do not open or open much less than normally when an action potential arrives
What is the net effect of presynaptic inhibition?
- reduce neurotransmitter release when the downstream terminal button receives action potential
What is the metod of action of presynaptic inhibition?
Entry of Cl-
What is presynaptic facilitation?
- depolarization of the axon terminal of the neuron supposed to independently release neurotransmitters
- voltage-gated calcium channels are more likely to open when an action potential arrives
What is the net effect of presynaptic facilitation?
- increase neurotransmitter release
What is the method of action of presynaptic facilitation?
- entry of sodium ions
- facilitates the entry of calcium ions
What is an autoreceptor?
- receptor located on the presynaptic membrane
When does an autoreceptor get activated?
- the cell releases its own neurotransmitter
What type of protein are autoreceptors?
- metabotropic receptors
- inhibitory
What is the function of autoreceptors?
- presynaptic inhibition
- detect when the cell has released enough neurotransmitters
What is the method of action of autoreceptors?
- enables g-protein to open metabotropic inhibitory receptors to hyperpolarize the neurone and stop the release of neurotransmitters
What is the neuraxis?
imaginary line that cuts the CNS in half
What are the only senses that are ipsilateral?
- Taste
- Smell
What are the brain nuclei?
Collection of neurons that are clusteres together and all work together to serve some brain function
What composes the central nervous system?
Everything in the brain, as well as the spinal chord
What composes the peripheral nervous system?
Any part of the nervous system that isnt inside the brain or the spinal chord (nerves)
Where are situated sensory neurons and motor neurons?
Span on both regions
What are the main differences between the CNS and the PNS?
- in the cns, myelin is created by oligodendrocytes, whereas it is created by schwann cells in the pns
- The CNS is protected by the blood-brain barrier
What are the differences between schwann cells and oligodendrocytes?
- schwann cells only myelinate one axon each
- schwann cells are in the pns
What is the extracellular fluid of the brain?
the cerebrospinal fluid
What is particular of the blood capillaries that pass through the brain and spinal chord?
the do not have gaps in them (blood brain barrier)
What are the meninges?
- protective connective tissues that surround the brain
What are the layers of the meninges?
- pia mater
- arachnoid membrane
- dura mater
What is the dura mater?
- outer layer of the meninges
- thick, tough, unstretchable tissue
What is the arachnoid membrane?
- middle layer of the meninges
- soft and spongy
- web-like appearance
What is the pia mater?
- layer of the meninges that is closest to the brain
- filled with blood vessels
What is the subarachnoid space?
- between the arachnoid membrane and the pia matter
- filled with CSF and blood vessels
What is the choroid plexus?
- tissue found in each of the brain ventricles
- found in all of the ventricles
- makes CSF
What is the half-life of CSF?
- 3 hours (it is half replaced every three hours)
Where are the lateral ventricles?
under the cerebrum
Where is the third ventricle?
Between the two thalamic nuclei
Where is the fourth ventricle?
between the pons and the cerebellum
What is the cerebral aqueduct?
- long, tube-like structure
- connects the third and fourth ventricle
What is an interneuron?
- A neuron of the CNS
- ONLY in the CNS
- The axon stays local
- communicates with cells in the vicinity
What are motor neurons?
- neurons that have a cell body in the spinal chord and the axon in the PNS
- efferent fibers
What are the functions of motor neurons?
- control muscle contractions
- control gland secretions
What are sensory neurons?
- afferent fibers
- cell bodies are just outside of the spinal chord
- detect changes in the external and internal environment
- send the info about the changes in the environment to the CNS
What are efferent fibers?
- brings information away from the CNS
What are the afferent fibers?
- brings information toward the CNS
What is a nerve?
- sheath of tissue that encases a bundle of individual nerve fibers
- peripheral nervous system
How do the brain and spinal chord communicate with the rest of the body?
via nerves
What are the spinal nerves?
- attach to the spinal chord
- one pair for each vertebrae
What are the cranial nerves?
- Serve sensory and motor functions of head and neck region
What is the structure of the spinal chord?
- long conical structure
- white matter outside, grey matter inside