Chapter 11 Fundamentals of NS Anatomy exam 2

What are the 3 primary physiological functions of the nervous system?

Sensory input (monitoring changes), Integration (processing and interpreting input), and Motor output (executing a response).

How do the Central Nervous System (CNS) and Peripheral Nervous System (PNS) differ in structural components and functions?

CNS consists of the brain and spinal cord (interprets sensory input and dictates motor output); PNS consists of cranial and spinal nerves (transmits information between the CNS and the rest of the body).

What are the 2 main cell types in nervous tissue and their primary roles?

Neurons (excitable cells that generate and transmit electrical signals) and Neuroglia/Glial cells (non-excitable cells that support, insulate, and maintain neurons).

What are the 2 types of neuroglia in the Peripheral Nervous System (PNS) and their functions?

Satellite cells (surround and protect neuron cell bodies in PNS) and Schwann cells (form insulating myelin sheaths around PNS axons).

What are 3 special physiological characteristics shared by all neurons?

Extreme longevity (can function for a lifetime), Amitotic nature (cannot divide or replace themselves), and High metabolic rate (require continuous supplies of oxygen and glucose).

What are the structural functions of a neuron's cell body, dendrites, and axon?

Cell body (biosynthetic center that synthesizes proteins/neurotransmitters), Dendrites (receptive input regions that convey signals toward cell body), and Axon (conducting region that generates and transmits impulses away from cell body).

How do nuclei vs. ganglia and tracts vs. nerves differ in anatomical location?

Nuclei are clusters of neuron cell bodies in the CNS, while Ganglia are clusters in the PNS; Tracts are bundles of axons in the CNS, while Nerves are bundles of axons in the PNS.

What is the function of the myelin sheath, and how does impulse transmission speed differ between myelinated and unmyelinated axons?

Myelin electrically insulates axons to increase impulse conduction speed; myelinated axons undergo rapid saltatory conduction, whereas unmyelinated axons undergo slow continuous conduction.

What are myelin sheath gaps (nodes of Ranvier)?

Uninsulated, exposed regions of the axon membrane between adjacent Schwann cells or oligodendrocyte processes where voltage-gated ion channels are concentrated.

How do afferent, efferent, and interneurons differ in direction of impulse transmission?

Afferent (sensory) neurons transmit signals toward the CNS; Efferent (motor) neurons transmit signals away from the CNS to effector organs; Interneurons reside inside the CNS to integrate and route signals between sensory and motor neurons.

What is resting membrane potential, and what is its typical resting voltage in a neuron?

A difference in electrical charge across the plasma membrane at rest, typically sitting at -70 mV (inside negative relative to outside).

How do leakage, chemically-gated, voltage-gated, and mechanically-gated ion channels differ in opening triggers?

Leakage channels are always open; Chemically-gated open when a specific neurotransmitter binds; Voltage-gated open/close in response to membrane potential changes; Mechanically-gated open due to physical deformation of the receptor.

How do depolarization and hyperpolarization differ in membrane charge and effect on neuronal excitation?

Depolarization makes the cell interior less negative/more positive (-70 mV toward +30 mV), exciting the neuron and increasing action potential likelihood; Hyperpolarization makes the cell interior more negative than resting potential, inhibiting the neuron.

How do graded potentials and action potentials differ in distance, location, and strength variability?

Graded potentials are variable-strength, short-distance signals occurring on dendrites and cell bodies; Action potentials are constant-strength (-70 mV to +30 mV), long-distance signals occurring exclusively on axons.

What are the 4 sequential steps of an action potential and the ion channel movements in each?

1) Resting State (voltage-gated channels closed, K+ leakage open), 2) Depolarization (Na+ voltage-gated channels open, Na+ rushes in to +30 mV), 3) Repolarization (Na+ inactivation gates close, K+ voltage-gated channels open, K+ rushes out), 4) Hyperpolarization (excess K+ leaves, Na+/K+ pump restores resting ion balance).

What is the threshold voltage required to initiate an action potential at the axon hillock?

-55 mV.

How does the nervous system code for a strong versus a weak stimulus if all action potentials are the same strength?

By increasing the frequency (number per second) of action potentials generated, not by changing the amplitude/size of the action potential.

How do the absolute refractory period and relative refractory period differ in ability to generate a second action potential?

Absolute refractory period occurs during Na+ channel activation/inactivation when NO second AP can fire regardless of stimulus strength; Relative refractory period follows when an exceptionally strong stimulus CAN trigger a second AP.

What 2 physical factors increase the conduction speed of an action potential along an axon?

Larger axon diameter (less resistance to current flow) and Higher degree of myelination (enables saltatory conduction).

What are the 6 sequential steps of synaptic transmission across a chemical synapse?

1) AP arrives at presynaptic axon terminal, 2) Voltage-gated Ca2+ channels open and Ca2+ enters terminal, 3) Ca2+ causes synaptic vesicles to release neurotransmitter via exocytosis, 4) Neurotransmitter diffuses across cleft, 5) Neurotransmitter binds postsynaptic receptors to open ion channels, 6) Neurotransmitter is terminated via reuptake, enzymatic degradation, or diffusion.

How do Excitatory Postsynaptic Potentials (EPSPs) and Inhibitory Postsynaptic Potentials (IPSPs) differ in ion movement and effect on the postsynaptic neuron?

EPSPs cause local depolarization via Na+ influx (bringing membrane closer to threshold); IPSPs cause local hyperpolarization via K+ efflux or Cl- influx (driving membrane further from threshold).

What are the primary physiological roles of Acetylcholine (ACh), Norepinephrine, Dopamine, Endorphins, and GABA?

Acetylcholine (stimulates muscle contraction at neuromuscular junctions), Norepinephrine (mediates fight-or-flight ANS response), Dopamine (controls reward, learning, and motor control), Endorphins (natural opiates that reduce pain), and GABA (primary inhibitory neurotransmitter that hyperpolarizes neurons).

PNS Subdivisions

Somatic (voluntary to skeletal muscle) vs. Autonomic (involuntary to cardiac/smooth muscle and glands)

What are the 3 Structural Classification of Neurons

Multipolar (3+ processes, most common), Bipolar (2 processes, rare/special senses), and Unipolar (1 process, sensory in PNS)

Role of astrocytes

Most abundant; (CNS) nourish neurons, support blood-brain barrier, clean leaked K+ and neurotransmitters, guide neurons

microglia

the immune defense cells (uses phagocytosis)

Role of ependymal cells

Ciliated cells lining central cavities to beat and circulate CSF

Role of Oligodendocytes

Form fatty myelin sheaths around multiple CNS axons

Role of Schawnn Cells

myelinate axons in the PNS

Soma =1 Dendrites = 2; Axon =3; Axon terminal = 4

1. cell body

2. receptive region (increases surface area)

3. conducting region

4. secretory region (releases NT)