Neuroanatomy Flashcards
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.
Microglia
Prime state
The state when microglia sense a foreign body/foreign waste. They grow large and digest/”swallow” the foreign bodies.
Limitation: Can’t fight things like meningitis well
Schwann Cells
Schwann cells create myelin sheaths that speed up action potentials’ travels along a single axon (PNS only).
i.e. They wrap themselves along a single axon.
A type of macroglia
Oligodendrocytes
Myelin creating cells (CNS only). Myelinate several different axons. Myelin speeds up the travel of action potentials.
A type of macroglia
Astrocytes
Glial cells that stablize the blood-brain barrier/are wrapped around blood vessels/maintain the environment in the brain. They provide neurons with oxygen, glucose, and other nutrients. They can buffer ions (sodium/potassium) in axons, adding/removing them in gap junctions. They can influence neurons at the synapse, increasing or reducing standard transmission.
Summary: Astrocytes are part of the blood brain barrier, provide neurons nutrients and influence neurons and ions.
Glial scarring is collections of [answer].
Glial scarring is collections of astrocytes.
Astrocyte Pores/Gap Junctions
Astrocytes come into contact with other astrocytes, and there they have specialized proteins that create pores. Anything small inside one cell can flow directly to the inside of the next cell through the pores.
Things can be diffused/spread out through this network.
Tripartite synapse
Refers to the communication between three parts of the synapse (“A conversation of three”). Astrocytes shape synaptic conditions/wrap around the synapse & the pre- and postsynaptic terminals communicate. Astrocytes regulate neurotransmitter levels, modulate synaptic transmission, etc.
Astrocytes also can promote formation and stability of synapses, play a role in synaptic pruning, respond to brain injury, and help with calcium signalling.
The Three Communications in a Tripartite Synapse
- Axon releases neurotransmitters (presynaptic)
- Dendrites receive neurotransmitters via receptors (postsynaptic, usually means dendrites)
- Astrocytes wrap around the synapses to protect the environment and also release chemical signals themselves (gliotransmission)
- They maintain the synaptic environment
- Also receive signals from the neurons
Grey matter
Where cell bodies of neurons are as well as where the dendrites are. Grey matter is where info is being sent and received & processes sensory information.
Grey matter makes up the outer layer of the brain.
White matter
Contains myelinated axons. The myelin is what gives white matter its colour.
White matter is found in the inner layers (subcortical tissues) of the brain.
Structural MRI - Drawback
We can’t use it for a lot of things because not everything appears on a structural MRI/the MRI does not show certain damage.
Nissl (cresyl violet) Staining
Stain binds to cell bodies (shows grey matter). Stains cell bodies in the brain a bluish-purple.
Fibre stain
Stains glial cells, so one can see where white matter in the brain is (shows you the myelinated axons).
Some areas fuzzier for the grey area (ha ha) between grey and white matter
Golgi Stain
The birth of modern neuroscience!
This stain is only taken up by a subset of neurons - 10%. For the first time, we can see individual neurons!
Can help show differences in schizophrenia, autism, etc.
Thyroxine hydroxylase
Enzyme involved in dopamine synthesis. Used as a marker for dopamine-related neurons in the brain when brain staining.
Neuraxis
The spine-to-brain path.
Anterior
Towards the front of the brain.
Posterior
Towards the back of the brain.
Superior
Higher/above in the brain.
Usually we do not use superior/inferior for humans
Inferior
Lower/below in the brain.
Usually we do not use superior/inferior for humans
Rostral
Towards the front of the brain in humans and animals. Points up the spinal curvature in humans.
Anterior and rostral are exact synonyms in quadrupedal creatures
Caudal
Towards the “tail” (so for animals, towards the back of the brain, but for humans is both referring to towards the back of the brain and downwards on the axis of the brainstem/spinal cord).
Posterior and caudal are exact synonyms in quadrupedal creatures.
Dorsal
Towards the back. To humans, points to the top of our brain, but points sideways on our back. If a human had a fins like a fish, those would be visual indicators of the dorsal directions.
Ventral
Towards the belly. In humans, points to the bottom of the brain and to the belly on the spinal axis.
Medial
Towards the middle (of the brain).
Lateral
Towards the edge (of the brain).
Left Lateral
On the (patient’s) left side
Right Lateral
On the (patient’s) right side.
Coronal Plane
Vertical plane that divides anterior and posterior sections of the brain.
Coronal section: Cutting so the front and back of brain separated
Sagittal Plane
Vertical plane that divides the brain into left and right sections. Is called a midsagittal plane if it divides the brain directly in half.
Sagittal section: Slicing the brain into left and right halves but not right down the middle
Mid-sagittal section: Slicing the brain into its left and right halves right down the middle
Horizontal Plane
Divides the brain into superior (upper) and inferior (lower) sections.
Horizontal section: Cutting at the horizon of the brain
Peripheral Nervous System (PNS)
Somatic Nervous System
Sends voluntary motor signals from the CNS to muscles in the body. Collects sensory information from the body and sends it to the CNS.
Peripheral Nervous System (PNS)
Autonomic Nervous System
Controls involuntary bodily functions. Heavily oriented towards internal organs/the internal bodily system
Subsystems in Autonomic Nervous System (ANS)
Sympathetic Nervous System
Activate’s the body’s “fight or flight” response. Stimulates secretion of adrenaline (epinephrine) and norepinephrine.
Shuts down the digestive system so the energy can be used elsewhere.
Elevates one’s heartbeat, and stimulates glucose production/release.
Subsystems in Autonomic Nervous System (ANS)
Parasympathetic Nervous System
Activates the “rest and digest” aspects of the nervous system. Conserves energy, slows one’s heart rate, and stimulates digestion.
Related to Subsystems in Autonomic Nervous System (ANS)
Sympathomimetic drugs
Drugs that act on the sympathetic nervous system by mimicking its endogenous agonists. Essentially, these drugs activate the same bodily functions as our “fight or flight” response: Raised blood pressure, heart rate, and so on.
The spinal cord narrows/tapers from the [answer] area (closest to brain) to the [answer] area (furthest from brain).
The spinal cord narrows/tapers from the cervical (closest to brain) area to the sacral/coccygeal area (furthest from brain).
The spinal cord frays into a bunch of [answer] at the bottom. These nerve roots are called the [answer].
The spinal cord frays into a bunch of axons at the bottom. These nerve roots are called the cauda equina.
In the spinal cord, all [answer] matter is inner, and all [answer] matter is area surrounding it.
In the spinal cord, all grey matter is inner, and all white matter is area surrounding it.
Ganglion
A cluster of neurons in the PNS.
Gyrus/gyri
The bumps/ridges in the brain.
Sulcus/sulci
The dips/valleys in the brain.
Longitudinal fissure
This fissure separates the left and right hemispheres.
Sylvian (lateral) fissure
This fissure separates the temporal lobe from frontal lobe and parietal lobes.
Forebrain
Where complex cognitive activities are performed. Very large in humans.
Hypothalamus
An older part of forebrain, regulates sleep, body temperature, heart rate, hunger, sex drive, and thirst. Also regulates the endocrine system.
Limbic system
Forms a barrier around cortical/non-cortical structures.
Nucleus accumbens
Play an important role in addiction. Play a key role in our reward system overall.
Hindbrain
Controls our vital survival functions (the medulla in the hindbrain controls breathing & heart rate, for example).
Lots of lethal drugs have effects on the hindbrain.
Basal ganglia
Composed of caudate nucleus and putamen. Are part of controlling voluntary movement.
Which arteries supply blood to the brain?
Four arteries supply blood to the brain. The left and right carotid arteries, and the vertebral arteries.
If an artery is blocked, that blood flow is gone and cannot reach the brain by any other route. This is part of why strokes are so harmful.
Blood-brain barrier (BBB)
Tightly packed astrocytes wrapped around tightly packed capillaries, protects the brain from foreign entities.
Meninges
Three layers of membranes that protect the brain and spinal cord.
Pia mater, arachnoid mater, dura mater
4 total, including the skull
Layers that protect the brain and spinal cord
Skull -> Dura Mater -> Arachnoid mater -> Pia mater
Cerebrospinal fluid (CSF)
Fluid that flows in and around the hollow/empty spaces of the brain and spinal cord. The brain produces CSF for nutrients, to remove waste, etc. but also is like an “airbag” in case we bump our heads.
Polymorphisms
The presence of multiple variant forms of a specific DNA sequence among individuals/populations.
Epigenetics
Enviromental factors that affect how genes work/express themselves. Can be passed down multiple generations, but epigenetic changes do not change the DNA sequence, just how it is expressed.
Central Dogma of Molecular Biology
Genetic information flows only in one direction: DNA codes for (m)RNA, (m)RNA codes for protein (it can also be from RNA directly to protein).
DNA -> RNA = transcription
(RNA -> DNA) = reverse transcription
RNA -> Protein = translation
Memory - Physical Basis
A change in the structure and function of your synapses.
For this change you need different collections/amounts of proteins.
So proteins are super important
Mitochondria’s Job
To produce the energy we use in a cell - ATP - adenosine triphosphate
To make this energy: Sugar and oxygen
Byproduct: ATP and CO2
What happens when we do not have enough oxygen to get the ATP we need?
- Anaerobic respiration
- Which requires energy storage
- Brain does not have energy storage
- So if you lose sugars/oxygens arriving to your brain, you are screwed
- Brain cells will die within a few minutes
Cytoskeleton - Function
- Can be used as a “highway”
- Long axon has cytoskeleton aiding its travel
- The only component of the cytoskeleton discussed in PSYC 301 - microtubules - relevant to Alzheimer’s, etc.
Central Nervous System (CNS)
What it consists of
Brain and spinal cord
Peripheral Nervous System (PNS)
What are the two sub-systems of the PNS
- Somatic nervous system
- Autonomic nervous system
Somatic Nervous System:
Internal or External?
Conscious or Unconscious?
Function?
- External, (mostly) conscious system
- Afferent side senses environmental sensations
- Efferent side controls muscles attached to skeleton
Autonomic Nervous System:
Internal or External?
Conscious or Unconscious?
Function?
- Internal body environment, (mostly) unconscious
- We do not have most of the info/control consciously of the ANS (excluding information like distress from internal pain)
Motor (E) vs. Sensory (A) Neurons
Know their “formal” names
Efferent (motor neurons): Carry signals from the brain to the body
Afferent (sensory neurons): Carry signals from the body to the brain
Autonomic Efferent Neurons
Two systems & their roles
Two Systems: Sympathetic and Parasympathetic Nervous System
Sympathetic Nervous System: For fight, flight, and preparing you for immediate activity/energetic demands
Parasympathetic Nervous System: For storing energy (glycogens, fats), “rest and digest,” slows breathing
The two systems can work in tandem (eg. sex)
Nucleus
Brain context
A cluster of cells in the brain
Ganglion/Ganglia
Don’t forget exception
Cluster of cells/axons in PNS
Exception: Striatum - Basal Ganglia
