Brain Bee chapter 1

Central nervous system vs Peripheral nervous sytem

Central nervous sytem is the brain and spinal cord, it is what makes the reactions and processes info. PNS is the communication network that connects CNS to rest of the body.

What are the subdivisions of the PNS?

 Somatic: Voluntary movements and carries sensory info
Autonomic: Involuntary movements; includes sympathetic (prepares body for "fight or flight" and parasymapthetic (calms body down for rest).  

What is white matter in brain?

Connects different parts of grey matter; has myelin insulation

What is myelin?

A protective, fatty-protein layer that wraps around axon. 
CNS: Oligodendrocytes
PNS: Schwann cells

Name the basic parts and functions of a neuron

Axon: Conducts electrical impulses (action potentials) away from cell body and toward other neurons, muscels, or glands. 
Axon terminal: End of axon; release neurotransmitters
Soma: Cell body, is the control center, provides nutrients to drive cellular activites
Synapse: the small space between neurons
Dendrite: recieve incoming chemical and electric signslas and carry towards cell body. 

What is a nerve network and what is it's function?

A group of nerve tracts connecting a series of regions in the brain. 
Route signals through the brain in a linear pathway, analyzing and organizing different types of information. 

Nerve fibre vs nerve tract vs neural network

A nerve fibre is an individual extension of a nerve cell (mostly the axon), a nerve tract is a bundle of these fibres inside the central nervous system (route signals) and is white matter, and a neural network is a functional web of connected neurons that process information.

what is the thalamortical loop?

2-way circuit that connects thalamus with parts of cortex. 

What are the patterns that feedback loops produce called? 

Brain waves! Identified by a electroencephalograph. 

4 types of brain waves, their frequencies and occurence

Alpha: Brain relaxed; parietal and occiptal lobes. 8-13HZ
Beta: Processes input; frontal and parietal lobes. 14-30HZ
Theta: Light sleep or rest; deep in brain, hippocampus. 4-7HZ
Delta: Deep sleep; thalamus, cerbral cortex.-3.5HZ

Neural Circuits? Function, definition, and other. 

Localized interconnected neurons that turn entering signals into output patterns that can be sent out to other regions of the brain. 
They perform specifc taks and are organized like shelves in a bookcase.
Columns form connections and each time a signl is passed on, the connections alter the signal making more complicated processes.
Columns can influence other columns, helps react flexibily.  

What are excitatory neurons and what is the most common?

Sends signals that push other neurons into firing. ~80%.
Pyramidal cell is the most common type, glutamate is the most commmon neurotransmitter. 

Inhibatory Neurons?

Sends signals that suppress the activity of neighboring neurons and regulate activity of a circuit. ~20%
GABA (gamma-aminobutyric acid) is the most common neurotransmitter. 

Feed forward inhibatory circuit?

Inhibatory neurons connect circuits in a way that excitatory signals in one coumn simultaneously inhibit activites of adjacent columns. 

Feedback inhibation loop?

Neurons send signals to downstream excitatory neighbors and to interneurons that reach back and inhibit preceeeding layers of the same circuit. 

Glia Cells! Function, types and definition?

Support cells, ratio of glia:neurons vary tremendously. 
Astrocytes: Form a network that helps regulate ion concentration, provides nutrients, and regulate formation of new connections between neurons. 
Oligodenrocytes: Make myelin in the CNS
Microglia: "immune cells" 
Ependymal: Produce, circulate, and filter cerebrospinal fluid maintaining fluid balance and brain health.
Schwann: Make myelin in the PNS

Frontal lobe's functions?

Voluntary movements
Speech
Memory
Emotion
Higher cognitive skills: planning, problem solving
Personality

Parietal Lobes

Integrate sensory information from skin, taste, and some visual 

Temporal Lobes?

Visual processing and auditory information
Language
Memory
Emotion

Occipatal Lobes?

Process and recognize visual information to understand sequences

Cerebellum

Under occipital lobe
Voluntary movements, motor, perception.

Cerebrum

Largest regions
2 hemispheres
Thinking
Sensory
Motor

Corpus Callosum

Bundle of nerve fiber
Bridge between the 2 cerebrum hemispheres

Thalamus

Integrates and relays sensory information

Hypothalmaus

"Homeostasis"
Links nervous system to endocrine system via pituitary gland

Basal ganglia

Collection of structures; regulates body movements

Pituitary Gland

Hormonal regulation, master gland
produces essential hormones and controls other glands

Amygdala

Integrates memory and emotion

Diencephalon

Located deep inside between the cerebral hemispheres and above the brainstem
Thalamus, hypothalamus, epithalamus, and subthalmus. 
Sensory relay, homeostasis, and hormone control. 

Brainstem

Connecting the brain to the spinal cord and controlling essential, life-sustaining automatic functions.
Midbrain, pons, medulla

Midbrain

Process sight and sound, coordinates movement, and manages reflexive responses. 
Connects forebrain and hindbrain

Pons

Unconsicous functions like breathing, posture and sleep.

Medulla

Connects the brain to spinal cord
Autonomic control and reflexes

Hippocampus

Located deep in temporal lobe
long-term memory and new memories.

Forebrain

Telencephalon: cerebrum, white matter, and limbic system (amygdala, thalamus, hypothalamus, and hippocampus) and basal ganglia. 
Diencephalon: thalamus, hypothalamus, epithalamus, and subthalamus.

Hindbrain

Glucose regulation, motor coordination and other autonomic functions
Cerebellum, pons, and medulla. 

Limbic System

Regulate emotion and motivation
Hippocampus, amygdala, hypothalamus, and thalamus. 

Cerebral cortex

Deeply folded outer layer of nerve tissue
Houses the different lobes

What are the 3 parts of a synapse?

Synaptic cleft
Dendrite of neuron 1
Axon of neuron 2

What is neurotransimssion? 

The process by which nerve cells, called neurons, communicate with each other annd make CHEMICAL signals that cross the synapse

Neurotransmitters vs action potential

An action potential is an electrical signal that travels inside a single neuron, while a neurotransmitter is a chemical messenger that carries the signal between different neurons. 
Very connected as action potentials trigger release of NT

Membrane potential? Definition and what is the resting?

Difference in electric charge between inside and outside of the cell
Ions cause the difference
Usually at -70mV

What are the 4 major ions, their charge, and location?

Sodium: Positive, in the cell at rest
Potassium: Positive, in the cell at rest
Chloride: Negative, outside the cell at rest 
Calcium: Positive, outside the cell at rest

How are action potentials created?

When NT bind to receptors, they deploraize the cell. this allows sodium ions to flood into the cell, causing massive depolarization. this is called the "rising phase" of the action potential. This depolarization creates an electrical signal, action potential. Eventually, it peaks and potassium channels open, meaing the positive ions leave, repolarization. But it overshoors and hyperpolarizes the neuron making it less likely to fire the next few times. 

Process of neurotransmission? 

At the presynaptic axon terminal, the action potential arrives. This cuases voltage-gated calcium channels to open in the terminal membrane. Ca+ ions flood in causing NT vesicles to fuse with the membrane and release NT into the synaptic cleft. 

How are neurotransmitters and action potentials linked? 

Action potnetials stay in the neuron and when they arrive at the axon terminal, they trigger the release of neurotransmitters. 

Excitory NT vs Inhibatory NT

Excitatory neurotransmitters increase the likelihood that a postsynaptic neuron will fire an action potential, whereas inhibitory neurotransmitters decrease that likelihood.
Depends on the receptor it binds to on the target cell.

The 3 ways NT can be removed

Diffusion : Neurotransmitter molecules passively drift away from the synapse and out of the synaptic cleft into the surrounding extracellular fluid
Enzymes: Specific enzymes located in the synaptic cleft break down the neurotransmitter into inactive fragments
Reuptake: Transporter proteins on the presynaptic neuron pumps the NT back into cell

Ionotropic vs metabotropic receptors

Ionotropic: When neurotransmitters (NT) bind to ionotropic receptors, the receptor acts directly as an ion channel and opens. If the channel allows positively charged ions to flow into the cell, it causes a small depolarization called an Excitatory Postsynaptic Potential (EPSP). Many EPSPs must summate  to depolarize to threshold

Metabotropic: Neurotransmitters bind to the extracellular side of the metabotropic receptor (often called a G-Protein Coupled Receptor). The binding changes the receptor's shape, which activates a G-protein attached to the inside of the cell membrane. The G-protein detaches and activates an enzyme, which produces small signaling molecules called second messengers. These second messengers go on to perform several cellular jobs: Open or Close Ion Channels, Activate Enzymes, Change Gene Expression.

What does the axon terminal membrane do after NT are released?

They cycle back into the soma as new vesicles, which are refilled with NT molecules.

Substances acting as NT?

Amino Acids
Neuropeptides
Gas
Small organic chemicals
Short peptides

What can and can't neurons synthesize in the axon terminal.

Can: small non-peptides like dopamine or acetylcholine
Can't: build proteins =, so peptide-based NT are built in ribosome-rich soma.

Microtubules?

Tiny, hollow tubes made of proteins that act as both the structural skeleton and the railway system inside neurons.
found throughout cell body, extending into axons and dendrites. 

Where are NT receptors found?

Outer surface of dendrite. Thick or dense, called post-synaptic density. 

Glutamate

Half the excitatory synapses use this

Bind to several inotropic receptors, AMPA (fast), and NMDA (slow) crucial for learning and memory

GABA (gamma-aminobutyric acid

Inhibitory NT

Bind to 2 groups

Ionotropic: Ion channels let CL- enter

Metabotropic: Ion channels release P+.

Both; Membrane potential down, stops firing

What are the types of molecules that can change the way neurons function?

Hormones: Send the brain specific cues about the condition and activity of distant tissues in the body

Neuromodulators: Neuromodulators diffuse over larger areas and alter how neurons respond. Suppress NT

Postaglandins: Small lipids that change the brain’s response (increasing sensitivity) to pain and inflammation

How do the molecules and receptors react to hormones + neuromodulators?

Individual neurons have receptors for different subsets of hormones and neuromodulators. Process starts when molecule binds to receptor.

1) If receptor on surface on the surface, molecule changes shape of the receptor and starts a chain of intercellular reactions. Signal changes neural function by changing ion balance or activity of specific enzymes.

2) If molecule can diffuse through membrane, receptor may be protein in the soma. When the hormone binds, the complex can transform into something that is capable of entering the nucleus, binding to genes and changing their activity.

Gene expression

Differences in neurons result from difference in genes that direct cellular activities.

Chromatin

The complex on DNA and protein that compactly packages the long DNA molecule in the nucleus.

How is Tay-Sachs disease formed?

A fatal degenerative condition

Mutation in gene that codes for part of a fat-metabolizing enzyme called beta-hexosamindase A. Doesn’t break down fats, build up = toxic.