Study Guide for Exam 1
● Identify the main divisions of the nervous system
○ CNS
■ Brain
■ Spinal cord
○ PNS
■ Somatic nervous system: voluntary control of skeletal muscles and sensory information
■ Autonomic nervous system: involuntary regulation of organs and glands
● Sympathetic: “fight or flight”
● Parasympathetic: “rest and digest”
● Identify the different cells of the nervous system and the functions of the supporting cells
○ Neurons
○ Supporting Cells of CNS:
■ Astrocytes: structural support, maintain the blood-brain barrier, regulate
neurotransmitters, and repair after injury
■ Oligodendrocytes: form myelin around multiple axons (CNS ONLY)
■ Microglia: immune defense, remove debris/damaged cells (phagocytosis)
○ Supporting Cells of PNS:
■ Schwann cells: form myelin around a single axon (PNS ONLY)
● Identify the structures of neurons and their general functions
○ Soma (cell body): contains nucleus and organelles; integrates incoming signals
○ Dendrites: receive information from other neurons (input)
○ Axon hillock: decision point where action potentials are initiated
○ Axon: conducts an electrical signal (action potential) away from the soma
○ Myelin sheath (from oligodendrocytes in CNS, Schwann cells in PNS): insulates axon, speeds
signal conduction
○ Nodes of Ranvier: gaps in myelin where ion exchange occurs; allow saltatory conduction (signal
“jumps”)
○ Axon terminals / terminal buttons: release neurotransmitters into the synaptic cleft
○ Synapse: a connection point where a signal is passed to the next neuron or muscle/gland cell
○
● Recognize the features and importance of the blood-brain barrier
○ Supported by astrocytes (glial cells) that maintain barrier integrity
○ Selective permeability: allows essential nutrients (glucose, oxygen) while blocking toxins and
pathogens
■ Protects the brain from harmful substances (e.g., bacteria, toxins)
■ Maintains a stable environment for neural function
■ Helps regulate neurotransmitter and ion balance, which is critical for signaling
■ Also poses challenges for drug delivery (many medications can’t easily cross)
● Recognize the general steps involved in neural communication in withdrawal reflexes (with and without
inhibition)
○ With inhibition:
■ Painful stimulus detected → Same as above
, ■ Sensory neuron → interneurons in the spinal cord
■ One interneuron excites flexor motor neurons (to contract the biceps, pulling the arm
away)
■ Another interneuron inhibits extensor motor neurons (to relax the triceps, preventing
opposition)
■ Motor output → Coordinated action — one muscle contracts, the antagonist relaxes
■ Effector response → Smooth withdrawal from pain source
● The brain tells the muscles not to drop the hot cup*
○ Without inhibition:
■ Painful stimulus → Nociceptors (pain receptors) in the skin detect the hot iron
■ Sensory neuron activated → Action potentials travel to the spinal cord (dorsal root)
■ Interneuron in the spinal cord → Excites the motor neuron
■ Motor neuron fires → Sends a signal to the flexor muscle
■ Muscle contracts → Arm pulls away from the hot iron (withdrawal)
⚡ This pathway bypasses the brain initially → makes it very fast (spinal reflex)
● Recognize how resting potentials, hyperpolarization, depolarization, and the action potential in neurons
work
○ Resting potentials: A neuron at rest has a negative charge inside compared to outside
■ Typical value: ~ –70 mV
Maintained by:
● Diffusion
● Electrostatic pressure
● Na/K pumps
● Composition of intracellular and extracellular fluid
○ Hyperpolarization: After repolarization, K⁺ channels stay open slightly too long, and the
membrane potential becomes more negative than resting (~ –80 mV)
■ This is the refractory period → a neuron cannot fire another action potential
immediately
○ Depolarization: When a stimulus reaches threshold (~ –55 mV)
■ Voltage-gated Na⁺ channels open
■ Na⁺ rushes into the neuron (down its electrochemical gradient)
■ Inside the cell becomes more positive (up to +30 mV)
■ This rising phase = the start of the action potential
○ Action potentials: All-or-none response: if the threshold is reached, the full spike occurs; if not,
nothing happens
■ Sequence:
Depolarization (Na⁺ influx).
Repolarization:
Na⁺ channels close.
Voltage-gated K⁺ channels open → K⁺ exits → inside becomes negative
again.
After-hyperpolarization (undershoot).
Travels down the axon via propagation:
In myelinated axons, it “jumps” node-to-node (saltatory conduction) =
faster.
In unmyelinated axons, it moves continuously = slower
● Recognize how diffusion, electrostatic force, and the sodium–potassium pump establish membrane
potential
○ Diffusion: Ions naturally move from areas of high concentration → low concentration
■ Inside the neuron: lots of K⁺ (potassium)
● Identify the main divisions of the nervous system
○ CNS
■ Brain
■ Spinal cord
○ PNS
■ Somatic nervous system: voluntary control of skeletal muscles and sensory information
■ Autonomic nervous system: involuntary regulation of organs and glands
● Sympathetic: “fight or flight”
● Parasympathetic: “rest and digest”
● Identify the different cells of the nervous system and the functions of the supporting cells
○ Neurons
○ Supporting Cells of CNS:
■ Astrocytes: structural support, maintain the blood-brain barrier, regulate
neurotransmitters, and repair after injury
■ Oligodendrocytes: form myelin around multiple axons (CNS ONLY)
■ Microglia: immune defense, remove debris/damaged cells (phagocytosis)
○ Supporting Cells of PNS:
■ Schwann cells: form myelin around a single axon (PNS ONLY)
● Identify the structures of neurons and their general functions
○ Soma (cell body): contains nucleus and organelles; integrates incoming signals
○ Dendrites: receive information from other neurons (input)
○ Axon hillock: decision point where action potentials are initiated
○ Axon: conducts an electrical signal (action potential) away from the soma
○ Myelin sheath (from oligodendrocytes in CNS, Schwann cells in PNS): insulates axon, speeds
signal conduction
○ Nodes of Ranvier: gaps in myelin where ion exchange occurs; allow saltatory conduction (signal
“jumps”)
○ Axon terminals / terminal buttons: release neurotransmitters into the synaptic cleft
○ Synapse: a connection point where a signal is passed to the next neuron or muscle/gland cell
○
● Recognize the features and importance of the blood-brain barrier
○ Supported by astrocytes (glial cells) that maintain barrier integrity
○ Selective permeability: allows essential nutrients (glucose, oxygen) while blocking toxins and
pathogens
■ Protects the brain from harmful substances (e.g., bacteria, toxins)
■ Maintains a stable environment for neural function
■ Helps regulate neurotransmitter and ion balance, which is critical for signaling
■ Also poses challenges for drug delivery (many medications can’t easily cross)
● Recognize the general steps involved in neural communication in withdrawal reflexes (with and without
inhibition)
○ With inhibition:
■ Painful stimulus detected → Same as above
, ■ Sensory neuron → interneurons in the spinal cord
■ One interneuron excites flexor motor neurons (to contract the biceps, pulling the arm
away)
■ Another interneuron inhibits extensor motor neurons (to relax the triceps, preventing
opposition)
■ Motor output → Coordinated action — one muscle contracts, the antagonist relaxes
■ Effector response → Smooth withdrawal from pain source
● The brain tells the muscles not to drop the hot cup*
○ Without inhibition:
■ Painful stimulus → Nociceptors (pain receptors) in the skin detect the hot iron
■ Sensory neuron activated → Action potentials travel to the spinal cord (dorsal root)
■ Interneuron in the spinal cord → Excites the motor neuron
■ Motor neuron fires → Sends a signal to the flexor muscle
■ Muscle contracts → Arm pulls away from the hot iron (withdrawal)
⚡ This pathway bypasses the brain initially → makes it very fast (spinal reflex)
● Recognize how resting potentials, hyperpolarization, depolarization, and the action potential in neurons
work
○ Resting potentials: A neuron at rest has a negative charge inside compared to outside
■ Typical value: ~ –70 mV
Maintained by:
● Diffusion
● Electrostatic pressure
● Na/K pumps
● Composition of intracellular and extracellular fluid
○ Hyperpolarization: After repolarization, K⁺ channels stay open slightly too long, and the
membrane potential becomes more negative than resting (~ –80 mV)
■ This is the refractory period → a neuron cannot fire another action potential
immediately
○ Depolarization: When a stimulus reaches threshold (~ –55 mV)
■ Voltage-gated Na⁺ channels open
■ Na⁺ rushes into the neuron (down its electrochemical gradient)
■ Inside the cell becomes more positive (up to +30 mV)
■ This rising phase = the start of the action potential
○ Action potentials: All-or-none response: if the threshold is reached, the full spike occurs; if not,
nothing happens
■ Sequence:
Depolarization (Na⁺ influx).
Repolarization:
Na⁺ channels close.
Voltage-gated K⁺ channels open → K⁺ exits → inside becomes negative
again.
After-hyperpolarization (undershoot).
Travels down the axon via propagation:
In myelinated axons, it “jumps” node-to-node (saltatory conduction) =
faster.
In unmyelinated axons, it moves continuously = slower
● Recognize how diffusion, electrostatic force, and the sodium–potassium pump establish membrane
potential
○ Diffusion: Ions naturally move from areas of high concentration → low concentration
■ Inside the neuron: lots of K⁺ (potassium)
