Neuroanatomy Flashcards
(94 cards)
Formaldehyde
Used to preserve brains and organs.
Weight of the human brain
3lbs, 2-3% of body weight
Amount of energy the brain consumes
The brain consumes 20% of our body’s energy.
Amount of neurons the brain has, and where most are located
The brain has <100 billion neurons, more than 50% of these are located in the cerebellum.
Neurogenesis
The process of formation of new neurons within the brain. Most neurogenesis happens within the womb, after we are born it happens in very small amounts only.
When we are born, we have the maximum amount of neurons we will ever have.
Very weak to no evidence for adult neurogenesis in humans (actually seems to only go up until 13).
Neuron
And what makes them special
Nerve cells that process and communicate messages and changes throughout the body.
Communication is direct, via axon, vs. being diffused (very fast communication with action potentials in mere milliseconds).
But they are in no way the only type of communicator cell (eg. glia do it too)
Flow of a neuron signal
The path a neuron signal travels (4 parts of a neuron)
Dendrite/input layer → cell body/soma → output layer/axon → terminals
Unidirectional
Dendrite
Parts of a neuron that receive information from other neurons.
Dendritic Spines
And high vs. low spine density
A unique, modifiable space. They are thought to create a modifiable connection with two neurons.
Spiny neurons almost always glutamate neurons.
Virtually all of the other neurons are non-spiny, but when we say non-spiny, we are usually referring to GABA.
Low spine density - Alzheimer’s (example)
High spine density - Autism (example)
Have massive effect on intellectual capacity, memory, etc.
Dendritic Spine Lifespan Timeline
Birth/Childhood: Synapse formation, dendritic spine number shoots up
Adolescence: Synapse number starts to decline (synaptic pruning)
Adulthood: Synapse number continues to decline
Autism: Much less synaptic pruning/dendritic spine maintenance overall
Schizophrenia: Much more synaptic pruning overall
Alzheimer’s Disease: Synaptic pruning is typical until onset of disease, then, much more synaptic pruning overall
Soma
The body of a neuron. Also contains the nucleus of the neuron.
Axon
The part of a neuron that sends neurotransmitters to other neurons.
Synapse
Components that make up the connection between neurons. Includes the axon terminals and synaptic cleft.
Synaptic Cleft
The gap between a pre- and post-synaptic neuron. Neurotransmitters travel along this gap.
Axon Terminals
Release neurotransmitters into the synaptic cleft to relay signals.
Nodes of Ranvier
Little gaps in between the myelin sheaths on an axon. They contain sodium that generates action potentials.
Projection Neurons
Neurons that extend from the neuronal cell body within the CNS to 1 or more distant regions of the CNS. Typically have a longer axon and fewer inputs/outputs than an interneuron.
Called projection neurons because they have a long axon that projects to a different brain area. Axons can be as long as you need them to be, the synapses interrupting them are so signals can be modulated and such (this is where the interneurons are).
Interneurons
Interneurons act as a bridge of communication between the CNS and PNS, transferring signals between the two. Help with synchronization of signals as well as timing of signals (eg. for motor skills). Can also help supress sensory information by inhibiting certain signals from sensory neurons.
Called interneurons because they have short axons that only project into the local area.
Create rhythms/oscillations in the brain.
Afferent Nerves/Neurons
Nerves/neurons that arrive at the CNS. They deliver sensory information to the brain. (A for arriving)
Efferent Nerves/Neurons
Nerves/neurons that deliver info from the CNS to muscles (in other words, they deliver motor signals). (E for exiting)
Pyramidal Neurons/Cells
Found in outer part of the brain/cerebral cortex
Stellate cells - star-like, in subcortical areas
Purkinje cells - Cells of the cerebellum, extraordinarily branched
Glia
Non-neuronal cells in the central and peripheral nervous system (CNS & PNS). Play a variety of roles (macroglia, microglia).
Macroglia
Myelinating glia. Schwann cells, oligodendrocytes, astrocytes. All glia except for the single type that is microglia. Maintain CNS homeostasis.
Microglia
Part of the brain’s immune response. Microglia surveil brain cells. When they sense foreign bodies, they go into a prime state.
Limitation: Cannot fight off things like meningitis easily.