Intro to Psych: Neurons, The Actions of Neurons

Philosophical Dualism

the philosophical idea that the mind and body are fundamentally different

Philosophical Materialism

philosophical idea that mental states is reducible to physical phenomena

Characteristics of Modern ECT Treatments

• last for about one minute

• are typically given 2-3 times per week for several weeks

• incorporate the use of muscle relaxant drugs, so the only sign of the controlled seizure is that their foot shakes

Neurons

cells in the nervous system that communicate with each other to perform information processing tasks

Glial Cells

support cells found in the nervous system, which have a variety of critical roles in the nervous system

Function of the Glial Cells

• digest parts of dead neuron

• provide physical and nutritional support for neurons

• form the myelin

Sensory Neurons

neurons that receive information from the external world and convey this information to the brain via the spinal cord

Characteristics of Sensory Neurons

• They have specialized endings on their dendrites that receive signals for light, sound, touch, taste, and smell. 

• They are typically unipolar 

Interneurons

neurons that connect sensory neurons, motor neurons, or other interneurons

Characteristics of Interneurons

• They are typically multipolar 

Motor Neurons

carry signals from the spinal cord to the muscles to produce movement

Neurons’ Three Broad Roles

1. Sensory Input: the sense and signals that the nervous system receives

2. Integration: determines your reaction

3. Motor Output: your reaction

Purkinje Cells

a type of interneuron that carries information from the cerebellum to the rest of the brain and the spinal cord

• These neurons have a dense, elaborate dendrites that resemble bushes

Pyramidal Cells

found in the cerebel cortex, have a triangular cell body and a single, long dendrite among many smaller dendrites

Bipolar Cells

a type of sensory neuron found in the retinas of the eye, have a single axon and single dendrite.

Receptors

a specialized cell that detects stimuli and converts them into electrical signals for the brain

Dendrites

the “tree branches” part a neuron, the area where neurons receive most of their information and relay it to the soma

Soma

also known as the cell body, the largest component of the neuron that coordinates the information processing tasks and keeps the cell alive (integrates information at the axon hillock)

The Function of the Soma

• Functions such as protein synthesis, energy production, and metabolism occur here 

• Contains a nucleus: where chromosomes are housed that contain your DNA 

• integrates information at the axon hillock

Axon Hillock

the area where the information from the dendrites goes

Axon

carries information to other cells, muscles, and glands (carries electrical signals from the soma to the terminals)

Ion Channels

protein pores in the neuron's membrane that regulate ion like movement, enabling electrical signaling, action potentials, and synaptic communication

Myelin Sheath

a fatty, protective layer that insulates nerve fibers (axons), enabling electrical impulses to travel quickly and efficiently along neurons

Nodes of Ranvier

breakpoints in between clumps/the ion channels

Axon Terminals (terminal buttons)

where the neurotransmitters are released

Synapse

the gap or the region between the axon of one neuron and the dendrites or cell body of another 

Neurotransmitters

chemicals that transmit information across the synapse to a receiving neuron’s dendrites

Autoreceptors

a receptor on the membrane of a nerve cell that responds to the same neurotransmitter that the cell itself releases, forming a negative feedback loop to regulate the release and/or synthesis of that neurotransmitter

Transporters

a transmembrane protein that removes neurotransmitters from the synaptic cleft, terminating their signal and preventing buildup

Acetylcholine (ACh)

is involved in voluntary motor control and is present at synapses where neurons connect to muscles (it is also involved in memory and attention)

Dopamine (DA):

regulates motor behavior, motivation, pleasure, and emotional arousal (in response to rewarding behaviors, neurons in the brain release dopamine)

Glutamate

the primary excitatory neurotransmitter in the brain

GABA (gamma-aminobutyric acid)

the primary inhibitor neurotransmitter in the brain, it can reduce or prevent excitatory postynaptic potentials that would otherwise trigger action potentials

Norepinephrine

is involved in the states of vigilance and heightened alertness of danger (fight or flight)

Serotonin

plays many roles in the nervous system, this transmitter affects sleep, wakefulness, eating, happiness, and confidence

Endorphins

generally, act within pain pathways and emotional centers of the brain

Agonists

drugs that increase action of a neurotransmitter 

• Ex. Prozac, Cocaine, Amphetamine 

Antagonists

drugs that decrease or completely block the function of a neurotransmitter 

• Ex. Opioids, Propranolol 

Beta Blockers

drugs that obstruct receptor sites in the heart for norepinephrine, a neurotransmitter that increases one’s heartbeat

Conduction

when the nerve impulses travel from the dendrites at one end of a neuron to the axon terminals at the opposite end

Resting Potential (resting state)

the difference in electrical charge between the inside and outside of a neuron’s cell membrane before a nerve impulse is sent

What happens during Resting Potential?

1. The cell is polarized; the inside is more negative than the outside 

2. Inside the neuron are negatively charged proteins ions that are too large to cross the cell membrane 

3. The voltage is –70mV, there are a lot of charged sodium ions outside the cell 

4. For the sodium channels to open, the axon must have a voltage value of -55mV 

Action Potential (nerve impulse)

an electric signal conducted from the axon hillock along the length of an axon to the axon terminals

What happens during the Action Potential stage?

1. As an action potential travels down the axon, each segment depolarizes, the electrical charge is briefly more positive inside than outside 

2. Sodium channels open and sodium ions rush into the axon 

3. During this stage the voltage is 40mV 

Refractory Period

occurs immediately after the sodium ions rush in during the action potential 

What happens during the Refractory Period?

1. A nerve impulse cannot be initiated until the electrical and chemical balance of the neuron is restored 

2. An axon’s segment is restored when potassium channels open and positively charged potassium ions rush out, shifting the voltage to +40mV (action potential) to –70mV (resting potential). 

3. The chemical balance in each axon segment must be restored, to fully restore the resting state sodium ions must be concentrated outside the cell and potassium ions must be concentrated inside 

4. The sodium-potassium pumps in the cell’s membrane to restore chemical balance by removing sodium ions and returning potassium ion

Ligand-Gated Sodium Channels

open when a neurotransmitter binds to a receptor on the exterior of the channel, changing the shape of the channel and allowing sodium into the cell.

Post Synaptic Potentials (PSPs)

electrical signals that travel from the dendrites through the soma to the axon hillock

• depend on ligand-gated sodium channels 

Voltage-Gated Sodium Channels

open are sensitive to the voltage of the cytoplasm at their location and open when the neuron’s interior becomes more positive

Action Potential (depolarization)

a positively charged electrical impulse that travels down the axon

• Action potentials depend on voltage-gated sodium channels

Status of ions channels during the process

• Resting Potential: sodium and potassium channels are closed

• Action Potential: sodium ion channels open

• Recovery: potassium ion channels open (polarzarization)