Lesson 1: Neurons and Neural Communication Flashcards
purpose of the nervous system
to transmit information
- tells what’s going on outside yourself (sensory information)(feeling that it’s getting too hot)
- allows you to access memories and make decisions by transmitting information about the past and current conditions (information processing)(decide to change the temp)
- passes on information to muscles so you can move (motor)(move muscles to walk to thermostat)
basic cell types of the nervous system
neurons (transmit info) and glia (don’t transmit info)
types and functions of glia cells
- astrocytes: transfer from blood to CNS neurons; provide structure
- satellite cells: absord dead cells; regulate nutrients
- oligodendrocites: myelinate axons in Central Nervous System
- Schwann Cells: peripheral nervous system myelination
- ependymal cells: regulate cerbrospinal fluid
- migroglia: remove debris through absorption
general structure of a neuron
- cell body (aka soma): main part of cell containing nuleus
- nucleus: contains DNA
- dendrites: part of neuron that receives info
- axon: part of neruon that sends info
- axon hillock: point at base of soma where action potential is generated
- myelin sheath: insulation covering some axons
- terminal buttons- branching endpoints of axons
neural firing and communication
- synaptic cleft: space in between each neuron
- synapse: the terminal button of neuron 1, the space, and the receptor of neuron 2
- when the neuron fire, it releases neurotransmitters into the synaptic cleft
- the receptors receiving the neuron pick up the neurotransmitter (excitatory/ inhibitory)
resting potential
when the neuron isn’t excited or inhibited
mechanisms of the resting potential
- membrane: a protective covering that separates the inside from outside (like skin)
- selective permeability: some ions can pass through the membrane more easily than others. Membrane has pores that can open or close to let some ions in and keep other out
- polarization: difference in charge between inside and outside (at rest when more negative inside w/ more potassium)
- sodium-potassium pump: maintains polarization by transporting 3 sodium ions out while transporting 2 potassium ions in (K is more negative than Na)
selective permeability (more in depth)
2 major ways to move across membrane:
- passive transport: gradients (gravitate toward opposite; where your kind is less concentrates,seek balance)
- active transport: processes that require energy
2 major stars of show: Sodium and Potassium
forces moving neuron away from resting potential
- electrical gradient: distribution of charge between inside and outside
- concentration gradient: the distribution of ions across the membrane
action potential
- nerve impulse starts when neuron moves from resting potential to action potential
- the polarization reverses and becomes more positive inside the neuron
- hyperpolarization: increased polarization
- depolarization: reduction of polarization toward 0
- threshold of excitation: point that produces a sudden and massive depolarization
- action potential: rapid depolarization and reversal of usual polarization
- all or none law: the amplitude, velocity of an action potential is always the same no matter how intense the initial stimulus was
- frequency can change
- refractory period: neuron is unlikely to produce action potentials (absolute: can not, Na is closed; relative: unlikely, K is open)
myelination and saltatory conduction
- myelinated axons: covered with an insulating substance called myelin sheath (connvey action potentials at super speed; typically found in neurons regulating primary survival processes)
- saltatory conduction: jumping of the action potential from node of ranvier to node of ranvier
processes at the synapse
the action potential is an all-or-nothing process along the axon, but activity in the dendrites and soma are far from all-or-nothing
synaptic cleft
gap between one neuron and the next
pre-synaptic
1st (sending) neuron
post-synaptic
2nd (receiving) neuron
synapse
includes pre-synatic neuron, synaptic cleft, and post-synaptic neuron
What is happening in post-synaptic membrane
- temporal summation: postsynaptic neuron receives messages close together (will add together and have cumulative effect)
- spatial summation: postsynaptic neuron receives simultaneous information at many locations (has cumulative effect)
- EPSP: excites, depolarization (increases probability of action potential)
- IPSP: inhibits, hyperpolarization (reduces probability of action potential)
what does the exciting/inhibiting
neurotransmitters:
- glutamate
- GABA
- acetylcholine
- serotonin
- catecholamines: important class of neurotransmitters (dopamine, norepinepherine, epinepherine)
where do neurotransmitters come from?
food:
- acetylcholine: choline in milk and cauliflower
- serotonin: typtophan in turkey
- dopamine: phenylalanine in chicken or liver
how do neurotransmitters get released?
neurotransmitters are stored in vesicles (little sacs). When the action potential reaches the axon terminal, calcium gates open which allows vesicles to bind to the neuron and excrete neurotransmitters into the synapse (exocytosis: releasing NT into the synaptic cleft)
how do the postsynaptic receptors get activated?
- neurotransmitters are elitist (only bind with their own receptors)
- when they bind with the receptor, they open gates for some ions (Glutamate opens sodium - is excitatory; GABA opens chloride - inhibitory)
- ionotropic effects: NT immpediately opens gates for some ion and polarization is immediately changed (immediate and short lived)
- metabotropic effects: bends protein which reacts with other molecules and increases the concentration of another substance (called a second messenger) (slower and longer lived)
what stops the neurotransmitters)
- as long as the NT i s bount to the receptor, activation or inhibition is occurring
- this is sometimes broken down by an enzyme (inactivation)
- sometimes transports take the NT back to the presynapse to get recycled (reuptake) (how SSRI antidepressants work on serotonin)
antagonist drug
block effects of neurotransmitter
agonist
increases effects of neurotransmitter (if it acts on an inhibitory neurotransmitter, the result is a lower likelihood of reaching action potential
affinity
binds to the receptor
efficacy
activates the receptor
hormone
secreted by a gland and conveyed by blood to other organs. they coordinate long lasting changes in multiple parts of the body unlike NTs
oxytocin
hormone that regulates uterine contractions, mmilk release, and bonding behavior from the posterior pituitary gland
melatonin
hormone that regulates sleep forom the pineal gland
thyroxine
hormone that regulates sleep from the thyroid
cortisol
hormone that regulates blood sugar and metabolism from the adrenal cortex in the kidneys
insulin
hormone that regulates blood sugar from the pancreas
