psych unit 2.2

Functions of Neurons

• receive sensory input (sensory neurons)

• process info & integrate with prior experiences (interneurons)

• output to guide our actions (motor neurons)

Glial Cells (Glia)

Support neurons (stimulate growth, repair damage, keep them in place)

The Action Potential (Neural Impulse) (8)

1. Dendrites receive info from other neurons and send the info to the soma (cell body).

2. When a neuron is at its resting potential, the soma is polarized (highly neg. charge). The “message” causes the soma to depolarize (pos. ions come inside, the cell becomes less negative).

3. If the cell reaches its threshold, an action potential (electrical impulse) is fired.

4. Impulse moves down along the axon (sodium gates are opening in a chain reaction, allowing more pos. ions to enter... energy/impulse is pushed along the axon).

5. Vesicles are pushed down to the axon terminals where they release neurotransmitters (chemicals) into the synapse/synaptic cleft.

6. Neurotransmitters bind to receptors on the dendrites of the next neuron. 

7. after binding, the sending neuron reabsorbs the neurotransmitters back into the axon terminal in a process called reuptake. (recycling)

8. Refractory period occurs where the cell is going back to rest (becoming polarized again). During this time another action potential cannot fire.

   **All-or-none Principle: A cell is either firing an action potential or not firing.

Neurotransmitters & Receptors

a. Neurotransmitters are chemical messengers released from the terminal branches of a neuron. They bind to receptor sites on a neighboring neuron. 

b. Neurotransmitters bind in a ‘lock & key’ fashion (i.e. specific neurotransmitters bind to specific receptor sites)

Excitatory Signals (more pos. ions)

The neuron is more likely to fire an action potential (depolarizing and likely to reach threshold)

Inhibitory Signals (more neg. ions)

The neuron is less likely to fire an action potential (remains highly polarized)

Agonists

mimics a neurotransmitter (binds to receptor to activate), prevent reuptake, or increases production/release

Antagonist

blocks receptor sites, preventing neurotransmitter from binding, or decreases production/release

Acetylcholine

enables muscle action and memory; undersupply linked to alzheimer’s

Dopamine

Influences movement and experience of pleasure. Undersupply - Parkinson’s, oversupply - schizophrenia

Norepinephrine (noradrenaline)

helps control alertness & arousal

Serotonin

Affects mood; undersupply - depression, oversupply - manic. both is bipolar

GABA

Calming down

Glutamate

Excitatory neurotransmitter that helps to learn

Endorphins

Reduces pain

Substance p

Pain perception

Sensory Neurons 

Carry incoming sensory information from the body’s tissues and sensory receptors to the spinal cord/brain. 

Interneurons

Neurons within the brain and spinal cord that communicate internally and process information between sensory inputs and motor outputs.

Motor Neurons

Carry outgoing information from the brain and spinal cord to guide muscles

Peripheral Nervous System

The main function is to connect the CNS to the limbs and organs, essentially serving as a communicator between the brain and spinal cord and the rest of the body

Somatic Nervous System

Voluntary muscle movement

Autonomic Nervous System

Controls involuntary responses (organs & glands) e.g. heart rate, blood pressure, breathing, etc.

Sympathetic Nervous System

Increases the overall arousal of the body; fight-or-flight response; prepares body for action (increases activity: heart rate, respiration, etc)

Parasympathetic Nervous System

conserves body's resources; calms body back down (decreases activity: heart rate, respiration, etc)

Spinal Cord in CNS

*Sends information to and from the brain (via interneurons)

*Controls reflexes

Reflexes

A simple, automatic response to a sensory stimulus

What is the reflex process?

spinal reflex pathway is composed of single sensory neurons and single motor neuron. communicate through spinal cord interneuron