Chapter 6 Flashcards
When do hollow enclosed neural tubes form?
During the first month of human development
What are the first cells in human development? What do they exhibit? What does that mean?
Neural progenitor cells.
They only exhibit symmetrical cell division.
Each cell becomes two of the same type.
When does the symmetrical cell division period end? What happens after?
It ends 40 days after conception.
Asymmetrical cell division then starts.
What happens when a neural progenitor dies during the 85 day period?
It produces one neural progenitor and either one neuron or one glial cell.
What happens after 125 after conception? What’s special? Why?
There are over 100 billion neurons in the human neurons.
This is the most neurons we ever have .
Many die before birth, seemingly because they can’t find a place in the network.
What is neurogenesis?
The production of new neurons.
What do neural progenitor cells do when they undergo asymmetrical cell division?
They produce neurons
When does human neurogenesis stop?
4 months after conception
What is apoptosis?
A process of programmed cell death that occurs in multicellular organisms.
What does apoptosis ensure?
That a dying cell does not cause problems for its neighbours.
When do neural progenitor cells undergo apoptosis?
125 days after conception
What’s in the midbrain?
Tectum and tegmentum
What is the midbrain? What does it orchestrate?
A collection of nuclei that orchestrate complex reflexive behaviours, such as species typical responses to threat and pain as well as orienting responses to sounds and lights.
How does the tectum appear?
As two pairs of bumps on the dorsal surafce of the midbrain.
What are the bumps on the tectum? What are they involved in?
Top 2 bumps: superior colliculi, involved with orienting the animal to things seen in peripheral vision.
Bottom 2 bumps: inferior colliculi, involved with orienting to unexpected sounds
What is in the tegmentum? What do they coordinate and motivate?
It includes several structures .
Coordinate and motivate complex species-typical movements.
What do some areas of the tegmentum do?
Process pain and orchestrate behavioural responses to threats
What is the hypothalamus? What does it generally do?
A bilateral structure made up of several nuclei.
It generally regulates autonomic nervous system activity.
What is the hypothalamus critically involved in? What are the four F’s?
Behaviours that directly relate to survival (the four F’s).
Feeding, fighting, fleeing and fucking
What do different hypothalamic nuclei control?
Body temperature, sleep wake cycles, hunger and social behaviour
What is the most important function of the hypothalamus?
To link the nervous system to the endocrine system (release of hormones into the blood stream) via the pituitary gloand
What is a hormone?
A chemical substance that is released by an endocrine gland and that has an effects on target cells in other organs
What is the endocrine gland?
A gland that secretes chemical signals (hormones) into the blood stream.
What is much of endocrine system controlled by?
Hormones produced by cells in hypothalamus.
What is the thalamus? What does it do?
A bilateral structure that is divided into several nuclei, many of which relay ascending sensory information to different regions of the cerebral cortex.
What has many widespread cortical projections?
Many nuclei
What is the cerebral cortex structure?
How are the neurons interconnected between layers?
What are they thought to be?
A multi layered structure.
In a way that gives rise to cortical columns
Which are thought to be partially distinct functional units
What is the cerebral cortex the largest site of?
What does it play a key role in?
Neural integration in the central nervous system.
It plays a key role in attention, perception, awareness, thought, memory, language, decision making and consciousness
What is the surface of the cerebral hemispheres?
What is it highly convoluted with?
The cerebral cortex.
Sulci (small grooves)
Fissures (large or major grooves)
Gyri (ridges between sulci or fissures)
What do convulotions do?
Increase the surface are of the cerebral cortex
What is the outermost portion of the cerebral cortex called? Why?
Gray matter.
Because of the high concentration of cell bodies there
Where is white matter? What does it have?
Beneath the gray matter
A large concentration of myelinated axons and very few neurons
What does the longitudinal fissure do?
Seperate the two hemispheres
What does the lateral fissure do?
Separates front from the temporal lobe
What does the central sulcus do?
Provides a good landmark separating the rostral and caudal divisons of the cerebral hemisphere
What is unified in the two cerebral hemispheres? How?
Perceptions and memories.
The corpus callosum
What is the corpus callosum
A large band of axons that connects corresponding parts of association cortex of the left and right hemispheres
What are the 4 lobes of the cerebral cortex? What do they control/process?
Frontal lobe, controls movement
Parietal lobe, processes touch information
Occipital lobe, processes visual information
Temporal lobe, processes auditory information
Where are taste and smell processed
In the lateral fissure
Taste: insular cortex
Smell: piriform cortex
Where is the primary motor cortex? What does it contain?
In the frontal lobe
It contains motor neurons that synapse in the spinal cord
Where is the somatosensory cortex? What is it?
Parietal lobe
Where touch information first enters the cerebral cortex
Where is the primary visual cortex? What is it?
In the occipital lobe
Where visual information first enters the cerebral cortex
Where is the primary auditory cortex?
What is it?
The temporal lobe.
Where auditory information first enters the cerebral cortex
Where is the insular cortex? What is it?
In the lateral fissure.
Where gustatory information first enters the cerebral cortex.
Where does each primary sensory area of the cortex send information?
To adjacent regions called the sesnory association cortex.
What takes place in the sensory association cortex?
Perception and memories
What happens in the regions of the association cortexes that are located closest to primary sesnory area?
They receive information from only one sesnory system
What are the basal ganglia and limbic system often referred to as? Why?
Subcortical structures.
Because they sit beneath the cerebral cortex
What are the basal ganglia?
A collection of nuclei in the forebrain
Where is the basal ganglia located?
Beneath the lateral ventricles
What do basal ganglia do as a circuit?
Regulate intentional movements, motivation, reinforcement learning and habits.
Where do inputs to the basal ganglia come from?
All over the forebrain, especially from the frontal lobe and cerebral cortex
Where are the outputs from the basal ganglia?
Some descend to the midbrain and hindbrain nuclei that regulate movement.
SOme outputs ascend to the thalamuc and cerebral cortex which regulate sensory processing and decision making.
What are many neurological disorders associated with? (classic movement disorders)
Basal ganglia dysfunction
What does the limbic system regulate?
Emotions and episodic memories
What is the lymbic system comprised of? Including?
Several distinct, interconnected structures.
Includinh the hippocampus, amygdala and cingulate cortex
What does the cingulate cortex overlie?
What does this region do?
A large area that overlies the corpus callosum.
It interconnect many limbic areas of the brain.
Where are the hippocampus and amygdala located?
What do they contain?
They are in the temporal lobe of the cerebral cortex.
They each contain several distinct nuclei.
What is the hippocampus critical for?
Explicit memory formation
What is the amygdala critical for?
Feeling and recognizing emotions, particularly fear
What are receptor proteins?
A protein that is sensitive to and capable of communicating some signal
What types of receptors are there?
ionotropic and metabotropic
What is an ionotropic receptor?
A receptor protein that is an ion channel.
What are metabotropic receptors?
A receptor protein that is an ion channel?
What is the effect of the activation of a metabotropic receptor?
Quite large, but often delayed because they rely on signaling cascades and diffusion
What are g protein coupled receptors?
Metabotropic
What is the main excitatory neurotransmitter? Why?
Glutamate.
Because all ionotropic glutamate receptors let sodium in
What is the main inhibitory neurotransmitter? Why?
GABA
BEcause all ionotropic GABA receptors let chloride in
What are the main neuromodulators?
Dopamine
Norepinephrine
Acetylcholine
Serontonin
What do neuromodulators act on? What kind of influence do they have on post synaptic cell activity?
They act on metabotropic receptors
They tend to exert a modulatory influence on postsynaptic cell activity
What do more than 99% of neurons release?
EIther GABA or Glutamate
Glutamate
Excitatory /inhibitory?
IPSC’s or EPSC’s?
Membrane depolarization or hypolarization?
Agonists?
Antagonists?
Excitatory
EPSC
Depolarization / sometimes an action potential
Often cause seizures and excitotoxicity (kainic acid/NMDA)
Dissaciative anesthetics (ketamine, PCP)
GABA
Excitatory /inhibitory?
IPSC’s or EPSC’s?
Membrane depolarization or hypolarization?
Agonists?
Antagonists?
Inhibitory
IPSC
Hyperpolarization
Often cause seizures
anhesthetics, anticonvulsants, muscle relaxants, sleeping pills, anti anxiety
How are neuromodulators made?
Made in a small collection of neurons that send their axons out widely
Is a neuromodulator a classic neurotransmitter?
Yes
Why are neuromodulators distinguished?
- They don’t typically produce simple excitatory or inhibitory effects in the CNS
- most of their reactions are G protein coupled receptors, not ion channels
- they often diffuse short distances outside of the synapse and can influence the activity of neighbouring neurons
What do we consider when classifying a neurotransmitter?
- what type of molecule is it?
- How and where is the neurotransmitter made?
- How does it get released?
- What kind of receptor proteins does it bind to?
- How does it get cleared away after it is released?
What are conventional neurotransmitters mostly?
Amino acid derivatives
Conventional neurotransmitters:
main players?
synthasized where?
secreted from where?
generally active where?
typically?
Usually bind receptors where?
Act over how long of distance?
glutamate, gaba, dopamine, serontonin, norepinephrine, acetylcholine
in axon terminals
secreted from the small synaptic vesicles that dock very close to the site of Calcium entry in the axon terminal
generally activate ionotropic and metabotropic receptors
they are typically recaptured after secretion and reused
usually bind receptors directly across the synapse
they act over distances of tends to hundreds of micrometers
What are neuropeptides?
A short string of amino acids (a protein with only 10-30 amino acids)`
Neuropeptides:
examples
synthesized where?
secreted from what?
activate what?
does synaptic recycling occur?
diffuses over how long of a distance?
there’s over 70, oxytocin, vasopressin. enkephalin, prolactin, NPY, ghrelin, cCRH
in the cell soma, then transported down the axon while undergoing additional processing, and released just once
secreted from large dense core vesicles that dock a ways back from the calcium entry in the axon terminal
only activate metabotropic receptors
no synaptic recycling occurs
diffuses over long distances and exert action at a distance (non synaptic communication)
What are examples of lipid based signaling molecules?
cannabinoids anandamide and arachidonyl glycerol)
Lipid based signaling molecules:
synthesized and released?
Secreted?
Activate?
Synthesized and released on demand, as needed
secreted in a non vesicular manner, typically from post synaptic neurons
activate metabotropic receptors, typically located on the presynaptic axon terminal
Where do classical (conevntional) neurotransmitters get manufactured?
Where do they get the necessary stuff/what is the necessary stuff?
In axon terminals.
The necessary enzymes and raw ingredients (generally single amino acids) float around freely in the axon terminal
What happens after a neurotransmitter is made?
It gets packaged into vesicles by transporter proteins, which are on the membranes of synaptic vesicles
What do serontonin, dopamine and norepinephrine all have in common?
They are all monoamines, they have a very similar three dimensional structure, the protein that packages each of these neurotransmitters into synaptic vesicles is the same (the vesicular monoamine transporter)
What are the two different neurotransmitters in the monoamine category? What do they contain? What do they have? Which does?
Catecholamine - contains dopamine and norepinephrine
Indolamines (serontonin)
They each have their own reuptake transporter protein (SERT, DAT and NET)
Which traffics the neurotransmitter from the synapse back into the axon terminal
What does acetylcholine do
in the CNS?
in the PNS?
CNS: acetylcholine primarily acts as a neuromodulator, often at axoaxonic synapses
PNS: acetylcholine is released by moto neurons at the neuromuscular junction, where it activates the fast excitatory ionotropic receptors on muscle cells that cause contraction
What do motor neurons generally release as their main neurotransmitter?
sensory neurons?
Motor neurons: acetylcholine
Sensory neurons: glutamate
