Exam 5: Study Guide Chapter 12 & 13

What makes up the Central nervous system (CNS)

Brain and spinal cord

What makes up the Peripheral nervous system (PNS)

Ganglion and nerve

What is the function of the PNS?

Carries information to and from the CNS

What kind of cells send and receive signals in both CNS and PNS?

Neurons

What are the two divisions of the PNS?

Sensory (afferent) and Motor (efferent)

What is the function of the CNS?

Integration (processes information and decides responses)

What are efferent (motor) neurons?

Neurons that send signals away from the CNS to target organs

What is the result of motor output?

Muscle contraction and/or gland secretion

What does the sensory (afferent) division do?

Sends signals TO the CNS

What does the motor (efferent) division do?

Sends signals AWAY FROM the CNS

What are the two parts of the motor division?

Somatic Nervous System and Autonomic Nervous System

What does the somatic nervous system control?

Voluntary movements (skeletal muscles)

What does the autonomic nervous system control?

Involuntary functions (organs, glands)

What are the two divisions of the autonomic system?

Sympathetic and Parasympathetic

What are the 3 basic functions of the nervous system?

Sensory input, Integration, Motor output

What is sensory input?

Detecting stimuli (internal or external)

What is integration?

Processing and interpreting information

What is motor output?

Response by muscles or glands

What are the two main types of cells in the nervous system?

Neurons and neuroglia (glial cells)

What is the function of neurons?

Send and receive electrical signals

What is the function of neuroglia?

Support, protect, and nourish neurons

What are the main parts of a neuron?

Dendrites, cell body, axon

What do dendrites do?

Receive incoming signals

What does the axon do?

Sends signals away from the cell body

What is the difference between afferent and efferent neurons?

Afferent = sensory (to CNS), Efferent = motor (away from CNS)

What type of neuron is most common?

Multipolar neuron

Structure of a multipolar neuron?

One axon, multiple dendrites

What is axonal transport used for?

Moving materials (proteins, organelles) along the axon

What is anterograde transport?

Movement from cell body → axon terminal

What is retrograde transport?

Movement from axon terminal → cell body

Which CNS glial cells line ventricles and circulate CSF?

Ependymal cells

Functional difference between gray and white matter?

Gray = processing, White = signal conduction

What triggers an action potential?

Reaching threshold

What does “all-or-none” mean?

Signal either fully happens or not at all

What cellular property allows neurons to respond to stimuli?

Excitability

What cellular property allows neurons to transmit signals?

Conductivity

What are effectors?

Muscles or glands that respond to neural signals

What type of ion channels are always open?

Leak channels

What do gated ion channels do?

Open or close in response to stimuli

What are the three types of gated ion channels?

Chemically (ligand), voltage, and mechanically gated

Which ion channels open in response to neurotransmitters?

Chemically gated ion channels

Which ion channels open in response to membrane potential changes?

Voltage-gated channels

Which ion channels open in response to physical deformation?

Mechanically gated channels

Which ion channels are mainly involved in graded potentials?

Chemically gated channels

Which ion channels are mainly involved in action potentials?

Voltage-gated ion channels

What is the resting membrane potential (RMP)?

The electrical charge difference across the membrane at rest (~ -70 mV)

Why is the inside of the neuron negative at rest?

More K⁺ inside and negatively charged proteins

What ion is most responsible for the resting membrane potential?

Potassium (K⁺)

How do leak channels contribute to RMP?

K⁺ leaks out more than Na⁺ leaks in

What does the sodium-potassium pump do?

Pumps 3 Na⁺ out and 2 K⁺ in

Why is the sodium-potassium pump important for RMP?

Maintains ion gradients

What two main factors maintain RMP?

Ion gradients + selective permeability of the membrane

How is a graded potential generated?

By opening gated ion channels that allow ions to flow across the membrane

What determines the strength of a graded potential?

The strength of the stimulus

What happens when Na⁺ enters during a graded potential?

Depolarization (membrane becomes less negative)

What happens when K⁺ leaves or Cl⁻ enters?

Hyperpolarization (membrane becomes more negative)

Why are graded potentials called “graded”?

Their size varies with stimulus strength

What must happen for a graded potential to trigger an action potential?

It must reach threshold at the trigger zone

What are the 3 main phases of an action potential?

Depolarization, Repolarization, Hyperpolarization

What happens during depolarization?

Voltage-gated Na⁺ channels open → Na⁺ rushes in

What happens during repolarization?

Na⁺ channels close, K⁺ channels open → K⁺ leaves cell

What causes hyperpolarization?

K⁺ channels stay open too long → membrane becomes more negative than resting

What is the correct order of events in an action potential?

Threshold → Depolarization → Repolarization → Hyperpolarization → Resting

Why does an action potential only move in one direction?

The previous segment of the membrane is in its refractory period, preventing immediate reactivation

What is the refractory period?

Time when a neuron cannot (or is less likely to) fire another action potential

How are action potentials propagated?

Local currents depolarize the next segment of the axon

What increases the speed of action potential conduction?

Myelination and larger axon diameter

What is saltatory conduction?

Action potentials “jump” between nodes of Ranvier

What type of synapse is most common?

Chemical synapse

What does Ca²⁺ do at the synapse?

Triggers neurotransmitter release

What is an EPSP?

Excitatory postsynaptic potential (depolarizes neuron)

What is an IPSP?

Inhibitory postsynaptic potential (hyperpolarizes neuron)

What determines if the postsynaptic neuron fires?

Summation of EPSPs and IPSPs

What is spatial summation?

Signals from multiple neurons at the same time

What is temporal summation?

Rapid signals from the same neuron over time

Example of an excitatory neurotransmitter?

Acetylcholine or glutamate

Example of an inhibitory neurotransmitter?

GABA or glycine

What are the two main classes of neurotransmitters?

Small-molecule neurotransmitters and neuropeptides

What determines the effect of a neurotransmitter (excitatory vs inhibitory)?

The receptor it binds to

What is the function of neurotransmitters?

Transmit signals across synapses

What is the most common excitatory neurotransmitter?

Glutamate

What is the most common inhibitory neurotransmitter?

Gamma-aminobutyric acid (GABA)

What are the 4 main types of neural circuits?

Diverging, converging, reverberating, parallel after-discharge

What is a diverging circuit?

One neuron → many neurons (spreads signal)

What is a converging circuit?

Many neurons → one neuron (integrates signals)

Why is regeneration limited in the CNS?

Inhibitory environment + lack of repair support

How do peripheral nerves repair themselves?

Schwann cells guide axon regrowth

What is plasticity?

Ability of the brain to change/adapt

What is neurogenesis?

Formation of new neurons

Example of a nervous system disorder?

Conditions like multiple sclerosis or Parkinson's disease

What protects the spinal cord?

Vertebrae, meninges, and cerebrospinal fluid (CSF)

What is the basic structure of the spinal cord?

A cylindrical structure made up of nervous tissue, surrounded by protective vertebrae. It consists of gray matter, white matter, and is organized into segments corresponding to spinal nerves.

How are spinal nerves connected to the spinal cord?

By dorsal (sensory) and ventral (motor) roots

What is the function of the dorsal root?

Carries sensory input into the spinal cord

What is the function of the ventral root?

Carries motor output out of the spinal cord

What is a spinal nerve made of?

Both sensory and motor fibers (mixed nerve)

What is a plexus?

Network of intersecting nerves

What are the major spinal nerve plexuses?

Cervical, brachial, lumbar, sacral

What is a dermatome?

Area of skin supplied by one spinal nerve

Why are dermatomes clinically important?

They help in diagnosing nerve damage and conditions affecting specific spinal nerves