Units 1, 2 and 3 Exam Review

What are the 2 major divisions of the nervous system?

Central nervous system (CNS) and Peripheral nervous system (PNS)

What does the CNS consist of?

Brain and spinal cord

What does the PNS consist of?

Cranial nerves and spinal nerves

How many pairs of cranial nerves are there and what is unique about them?

12 pairs; they BYPASS the spinal cord

What is the difference between somatic and autonomic nervous system?

Somatic = voluntary (sensory info + body movements); Autonomic = involuntary (controls organs)

What are the 2 divisions of the autonomic nervous system?

Sympathetic and Parasympathetic

What does the sympathetic division do?

Fight or Flight responses

What does the parasympathetic division do?

Rest and Digest (Rest and Restore)

What are the 5 major types of glial cells?

Oligodendrocytes, Schwann cells, Microglia, Astrocytes, Radial glia

What do oligodendrocytes do?

Form myelin around axons in the CNS (for faster signals)

What do Schwann cells do?

Produce myelin in the PNS (peripheral nerves)

What do microglia do?

Remove debris from damaged/dead neurons (brain's immune system)

What do astrocytes do

Star-shaped; store nutrients; form blood-brain barrier

What do radial glia do?

Form scaffolding to guide migrating neurons to destinations

What advantage does myelination provide?

Faster signal transmission along axon

What is membrane potential?

The charge inside compared to outside the neuron

What does it mean when a neuron is polarized?

Inside and outside of neuron are very different in charge

What is the resting potential of most neurons?

About -70 mV (more negative inside)

What happens when Na+ ions enter a polarized neuron?

The neuron becomes depolarized (less negative)

When is a neuron most likely to fire?

When its membrane potential reaches the action potential threshold

How are neurotransmitters cleared from the synapse?

1) Reuptake into presynaptic neuron, 2) Degradation by enzymes

What are the 2 factors that cause sodium to pass through ion channels?

Diffusion and Electrostatic pressure

When action potential arrives at axon terminal, what happens?

Ca++ channels open and Ca++ rushes in

What does the inflow of Ca++ cause?

Neurotransmitter-filled vesicles fuse with membrane (exocytosis)

What is an EPSP?

Excitatory Postsynaptic Potential - a depolarization that increases likelihood of firing

What is an IPSP?

Inhibitory Postsynaptic Potential - a hyperpolarization that decreases likelihood of firing

If membrane potential changes from -70 to -68, is this EPSP or IPSP?

EPSP (less negative = depolarization)

If membrane potential changes from -70 to -73, is this EPSP or IPSP?

IPSP (more negative = hyperpolarization)

What is spatial summation?

Inputs at different locations of neuron add together

What is temporal summation?

Inputs in rapid succession at same location add together

What is a fast-firing neuron?

A neuron that generates action potentials frequently

How many times per second can rapid-firing neurons fire in humans?

Up to 1,000 times per second

What are recurrent connections?

Neurons activate each other in loops; maintain activity over time (working memory)

Which brain region shows sustained activity during working memory delay?

DLPFC

What are divergent connections?

Few neurons → many recipients. Ex: VTA dopamine → millions; alpha motor neuron → thousands of muscle fibers

What are convergent connections?

Many neurons → few recipients. Ex: Rods → bipolar cells; cortex → striatum

What does the Na+/K+ pump do?

3 Na+ for every 2 K+ imported

What provides energy for the Na+/K+ pump?

ATP (adenosine triphosphate)

What are 4 ways psychoactive drugs affect neurotransmission?

1) Synthesis, 2) Release, 3) Binding to receptors, 4) Blocking reuptake

What does L-DOPA do?

Increases synthesis of dopamine

What does MDMA do?

Increases release of serotonin

What does Heroin do?

Mimics effects of endogenous opioids

What do SSRIs (Zoloft, Prozac) do?

Block serotonin reuptake, increasing serotonin in synapse

What is an agonist?

A drug that mimics or enhances neurotransmitter activity

What is an antagonist?

A drug that blocks or reduces neurotransmitter effects

Give 3 examples of agonist drugs.

L-DOPA, MDMA, Heroin, SSRIs, Ritalin (any 3)

Give an example of antagonist drug.

Haldol (blocks dopamine receptors)

What are 5 features ALL sensory systems share?

1) Sensory receptors, 2) TRANSDUCTION, 3) Neural pathways, 4) Primary cortical area, 5) Higher cortical areas

What is TRANSDUCTION?

Conversion of physical energy into neuronal activity

What are sensory receptors in vision?

Photoreceptors (Rods and Cones)

What are the 2 types of photoreceptors?

Rods and Cones

Where are rods located and what do they do?

Periphery of retina; low light/night vision and motion

Where are cones located and what do they do

Fovea (center); color vision and high acuity/detail

Why do cones provide high acuity

One-on-one communication with bipolar cells

Why do rods produce blurry vision?

Many rods converge onto fewer bipolar cells

How many types of cones and what wavelengths?

3 types: Blue (short), Green (medium), Red (long)

Visual pathway from light to optic nerve?

Light → Cornea → Pupil → Lens → Retina → Photoreceptors → Bipolar → Ganglion (optic nerve)

What is optic disk and why is it the blind spot?

Where optic nerve exits; no photoreceptors there

What is a receptive field

The visual stimuli that a neuron responds to

What is lateral inhibition and why important?

Photoreceptors suppress neighbors via horizontal cells; enhances edge detection/contrast

What cells do lateral inhibition?

Horizontal cells

What does the dorsal stream process?

object location

What does the ventral stream process?

WHAT - color and shape

What are sensory receptors in audition?

Hair cells

Auditory pathway from cochlea to cortex?

Cochlea → Auditory Nerve → Cochlear Nucleus (medulla) → Superior Olive (pons) → Inferior Colliculus (midbrain) → MGN (thalamus) → Auditory Cortex

Describe auditory transduction.

Sound → eardrum → ossicles → cochlea fluid → hair cells bend → K+ enters → glutamate released → auditory nerve

When hair cells bend, which ion enters?

K+ (potassium)

What neurotransmitter do hair cells release?

Glutamate

2 mechanisms for sound localization?

Interaural timing difference and Interaural intensity difference

What is interaural timing difference?

Difference in time for sound to reach left vs right ear

What is interaural intensity difference?

Difference in loudness between left and right ear

Which brain regions process sound localization?

Superior olive (pons) and Inferior colliculus (midbrain)

What are the 3 ossicles (small bones) in the ear?

Malleus, Incus, Stapes

What is tonotopical organization?

Cells that respond to different sound frequencies (low to high pitch) are located in different places; maintained from cochlea to auditory cortex

2 types of sensory receptors in skin?

Mechanoreceptors (touch/pressure) and Nociceptors (pain)

Somatosensory pathway from skin to cortex?

Sensory receptors → Spinal cord → Thalamus (ventral posterior nucleus) → Somatosensory cortex (parietal)

What are the 4 types of mechanoreceptors?

Merkel's disks (light touch), Meissner's corpuscles (touch/slow vibration), Ruffini endings (stretch/warmth), Pacinian corpuscles (deep pressure/rapid vibration)

What is the homunculus?

: Distorted sensory map showing body parts represented in somatosensory cortex (larger areas = greater sensitivity)

What determines two-point discrimination ability?

Size of receptive fields and receptor density

What are the 5 types of taste?

Salty, Sweet, Bitter, Sour, Umami

What % of taste comes from smell?

Approximately 80%

What cranial nerves carry taste signals?

Facial, Glossopharyngeal, Trigeminal, Vagus

Motor control flow from goal to movement?

PFC (goal) → Premotor/Primary Motor → Spinal Cord → Muscles. Also: Parietal (feedback), Cerebellum (accuracy), Basal ganglia (automaticity)

What does PFC do in motor control?

Generates goal to make movement (or stop it)

What do Premotor & Primary Motor Cortex do

Translate goal into action via signals to spinal cord

What does spinal cord do in motor control?

Communicates directly with skeletal muscles to move body

What does parietal cortex do in motor control?

Adjusts fine movements based on sensory feedback

What does cerebellum do in motor control?

Modifies movements for accuracy and timing

What do basal ganglia do in motor control?

Modify movements for automaticity/habitual actions

If cervical spinal cord severed, can you move hand?

NO hand, NO foot (nothing below cut)

If lumbar spinal cord severed, can you move hand? Foot?

YES hand, NO foot (things above cut work)

What do alpha motor neurons release at neuromuscular junction?

Acetylcholine (ACh)

What receptors on muscle fiber?

Nicotinic receptors

When ACh binds muscle fiber, what happens?

Na+ channels open → muscle contraction

How many muscle fibers can one alpha motor neuron target?What connection type?

Thousands; Divergent connection

What are Central Pattern Generators (CPGs)

Neurons in spinal cord/brainstem that control automatic rhythmic behaviors without conscious awareness

Give 3 examples of CPG-controlled behaviors.

Walking, Chewing, Breathing

Can higher brain regions override CPGs?

YES; holding breath, chewing to a beat, changing walking pattern

What does direct pathway in basal ganglia do?

Maintenance of thoughts, emotions, habitual actions

What does indirect pathway in basal ganglia do?

Interruption/redirection of thoughts, emotions, actions