S&F1 Nervous System Quiz

UCA- Hicks Fall 2025

Central Nervous System (CNS) Parts

Brain

Spinal Cord

(think center of the body)

Peripheral Nervous System (PNS)

Cranial Nerve

Spinal Nerves

Ganglia

(think anything that says nerve)

Neurons communicate using what 2 types of signals?

1) Electrical signals (Action Potentials)

2) Chemical Signals (neurotransmitters)

PNS: Sensory Input:

Info collected from receptors & delivered to the CNS by sensory Neurons

CNS: Interneurons

Where integration and processing of the sensory infor occurs

Motor Output

CNS causes a response by activating effector organs/tissues

Motor Neurons

(efferent) neurons that conduct signals from the CNS to effectors such as muscles and glands

Spinal Nerves

• 31 pairs that originate in the Spinal Cord

• carry sensory input into CNS + motor output to/from limbs & trunk (two lane highways)

Cranial Nerves

• 12 pairs that emerge from the brainstem

• serves structures of the head & neck

• exception = the vagus nerve (comes from the brain stem but goes to the body)

Sensory Nerves

carry info from receptors to the CNS (going in)

Somatic Sensory:

From receptors in skin, skeletal muscle, bones, & joints

Visceral Sensory:

from receptors in Smooth muscle (walls of hollow organs, blood vessels, etc), Cardiac muscle

• Hunger= Feeling hungry

• Nervousness= feeling heart pumping

Motor Nerves: 

carry infor from CNS to effectors to produce a response

Visceral motor:

to smooth muscle, heart & glands (autonomic nervous system)

• Sympathetic NS: stress response (“fight or flight”)

  • uses stored energy

• Parasympathetic NS: Recovery (“rest and digest”)

  • stores nutrients to get ready for SNS

  • Controls Digestions (“house keeping)

Somatic Motor:

To skeletal muscles & joints for voluntary movements

Neurons:

• Electrically excitable cell (generates Action Potential)

• Characteristics

  • Longevity: good lifestyle = Neurons living you whole life

  • Amitotic= Can’t divide

  • Increased Metabolic Activity (high metabolism = demands O₂ & glucose all the time)

• Nuclei: Collection of neurons (cell bodies) in the CNS

• Ganglia: (ganglion= singular) in PNS

Nuclei

Groups of Neurons that work together to perform something in the brain

Synapse:

Junction at the end of an axon where it stimulates another cell

• where neuron comes into contact with the target cell

Pre-synaptic Terminal:

Electrical signal converted to a chemical signal

• The “sending Cell”

Post-synaptic cell

The target cell that receives signals from the pre-synaptic terminal, typically through neurotransmitter binding at receptors.

Nerves

Bundles of Axons, surrounded by connective tissue (CT) in the PNS

• Carries info into the CNS

• “Myelinated”

Tracts:

Bundles of Axons in the CNS.

• No CT wrapping. 

• Carries info within the CNS (ex, between brain regions or up/down the spinal cord)

Neuroglial Cells of the PNS

Schwan Cell

• Function: myelinate certain axons in the PNS (wrap their bodies around the axon- around & around until it becomes the myelin sheath which is primarily lipids)

Satellite Cell

• Surround and support cell bodies (the somas of the neurons)

Myelinated Axons

20% protein, 80% lipid 

• There are organelles and Cytoplasm in the sheath

• Babies need fat from regular milk to form the sheath (which is why skim is bad for them)

Neuroglial cells of the CNS

Astrocyte (star-shaped) - more common than the others

• Anchor Neurons and blood vessels

• regulate the extracellular environment

• Facilitates the formation of the blood-brain barrier

• Repair damaged tissue/ form scar tissue

Microglial

• Act as phagocytes (can wander!)

• like garbage trucks that wander looking for stuff that doesn’t belong

Ependymal 

• line cavities (ventricles in brain)

• Cilia Circulate Fluid (CSF- cerebral spinal fluid)- making new all the time to be circulated around the brain and Spinal cord

• around brain and spinal cord

• some secrete this fluid

Feed the Neurons!

Glucose turned into lactate (neurons really like lactate)

Nerve Growth Factor

essential to keep neurons alive

Astrocytoma

Tumor of the astrocytes

• most tumors are glial cells because they can divide while neurons can’t

Diameter impact on Neuron Speed

Bigger diameter = faster neuron

• more membrane for more ion channels 

Multiple Sclerosis (MS)

Oligodendrocytes are attacked by the immune system, which causes myelin to be impaired

• some might go blind or struggle with movement

How do Neurons communicate?

AP causes the release of Neurotransmitters, which bind to their receptors to produce a response. 

2 main types of Neurotransmitters

• Excitability NTs: causes something to happen (stimulates AP)

• Inhibitory NTs: inhibit the post-synaptic cell (turns the neuron off)

If neurons can’t generate the AP, they won’t work (which is why APs are important)

What causes the electrical signals of neurons?

movement of ions across cell membranes (ion channels)

Chemically gated ion channels (ligand-gated)

open in response to binding of the appropriate neurotransmitter (closed until a chemical binds them and opens them- most commonly NTs). 

• neurotransmitters, drugs, odor molecules, etc. 

Voltage-gated Ion Channels (charge)

open in response to changes in the membrane potential (opened by a change in charge)

• charge in membrane voltage (charge)

leak Channels

leak ions like a drippy faucet

Mechanically-gate channels

opened by physical force (pressure, stretch, etc.)

• Potential: difference in charge across the membranes (inside and out)

• current: the flow of charge down the axon

• RMP: resting membrane potential (the difference in charge across a membrane in an unstimulated neuron. 

Sodium and potassium levels in the ECF

NA⁺ = 145 mEq/L

K⁺ = 4 mEq/L

Sodium and potassium levels in the ICF

Na⁺ = 12 mEq/L

K⁺ = 150mWq/L

Depolarized/ Depolarization

inside of the cell becomes less negative or full on positive

• due to the influx of positive ions

• anytime you depolarize the cell you have to repolarize it.

Repolarized/ repolarization

Due to the influx of negative ions or the efflux of positive ions.

Hyper Polarized

membrane potential gets more negative than resting membrane potential

Local Potential

any change in charge in the dendrites or some due to the opening of chemically-gated Na⁺ channels

• decremental: decreases as it moves away from the stimulus (ions have more space to go out)

• Reversible: presence of stimulus = LP, remover or stop the stimulus then the LP stops

how do we repolarize?

K channels start opening when ICF become more positive

• ICF becomes negative by the effect of positive charges (losing positive charge as it leaves) “repolarization phase”

• the sodium potassium pump restores the electrochemical gradient

refractory

Neuron has to be fully repolarized before generating another AP

Characteristics of an Action Potential

• all or none (always an AP if you reach the threshold)

• non decremental

• irreversible

Lidocaine

inhibits voltage-gated NA⁺ channels

• The dentist injects lidocaine to stop pain

• Dr. hicks is scared of going to the dentist because of the shot (she goes every months tho)

Hyperkalemia

high elevated extracellular K⁺

• increased RMP

• increased NM excitability

Hypokalemia

Low extracellular K⁺ 

• decreased RMP

• decreased NM excitability

Contiguous Conduction

Unmyelinated axon (like stepping on every tile)

Saltatory Conduction

Myelinated Axon (like skipping across a room)

• has nodes of Ranvier

How does the signal stop?

• Diffusion away from synapse

• degradation of NT through Enzymes

• Reuptake: NY goes back into the neuron that released it via protein transporters (not at NT do this)

  • SSRIs: selective serotonin Reuptake inhibitors→ block reuptake process