overview of nervous sytem

Question 1

What are the three basic functions of the nervous system?

Answer 1

1. Sensory Input: Detects changes (stimuli) and sends information to the brain/spinal cord.
2. Integration: Processes and interprets sensory input to determine an appropriate response.
3. Motor Output: Activates effectors (muscles/glands) to respond to stimuli.

Question 2

What are the two structural divisions of the nervous system?

Answer 2

1. Central Nervous System (CNS): Brain and spinal cord; control center for processing and decision-making.
2. Peripheral Nervous System (PNS): Cranial nerves and spinal nerves; connects CNS to the body.

Question 3

What are the functional divisions of the peripheral nervous system (PNS)?

Answer 3

1. Sensory (Afferent) Division: Sends information to the CNS from sensory receptors.
2. Motor (Efferent) Division: Sends information from the CNS to effectors (muscles/glands).

Question 4

What are the subdivisions of the motor division of the PNS?

Answer 4

1. Somatic Nervous System (SNS): Voluntary control of skeletal muscles.
2. Autonomic Nervous System (ANS): Involuntary control of smooth muscle, cardiac muscle, and glands.

Question 5

What are the two subdivisions of the autonomic nervous system (ANS)?

Answer 5

1. Sympathetic Division: “Fight or flight” response.
2. Parasympathetic Division: “Rest and digest” activities

Question 6

Name the four types of neuroglia in the CNS and their functions.

Answer 6

1. Astrocytes: Support neurons, control extracellular environment, form blood-brain barrier.
2. Microglia: Phagocytic cells that remove debris, pathogens, and dead neurons.
3. Ependymal Cells: Produce and circulate cerebrospinal fluid (CSF).
4. Oligodendrocytes: Produce myelin sheath around CNS axons.

Question 7

Name the two types of neuroglia in the PNS and their functions

Answer 7

1. Satellite Cells: Support neuron cell bodies in ganglia; regulate chemical environment.
2. Schwann Cells: Form myelin sheath around axons in the PNS; aid in regeneration.

Question 8

Define a neuron and its role

Answer 8

A neuron is the basic structural and functional unit of the nervous system, specialized to conduct electrical impulses.

Question 9

List the major parts of a neuron and their functions.

Answer 9

Cell Body (Soma): Contains nucleus; metabolic center.

Dendrites: Receive signals from other neurons.

Axon: Transmits impulses away from the cell body.

Axon Hillock: Initiates action potentials.

Myelin Sheath: Insulates axon and increases speed of impulses.

Axon Terminals: Release neurotransmitters to communicate with other cells.

Question 10

Why is the myelin sheath important, and how is it formed?

Answer 10

Importance: Increases conduction speed of nerve impulses and insulates axons.

Formation:
CNS: Formed by oligodendrocytes.
PNS: Formed by Schwann cells.

Question 11

How are neurons classified by function?

Answer 11

Sensory (Afferent) Neurons: Transmit sensory information to CNS.

Motor (Efferent) Neurons: Carry instructions from CNS to muscles/glands.

Interneurons: Integrate and process information in CNS; connect sensory and motor neurons.

Question 12

Define resting membrane potential and explain its electrochemical basis.

Answer 12

Definition: Voltage difference across the resting neuron’s membrane (~ -70 mV).

Basis:
High Na⁺ outside; high K⁺ inside.

Membrane more permeable to K⁺ than Na⁺ → K⁺ leaks out, making inside negative.

Na⁺/K⁺ pump maintains this gradient (3 Na⁺ out, 2 K⁺ in).

Question 13

What are graded potentials?

Answer 13

Small, localized changes in membrane potential that vary in strength and diminish over distance.

Question 14

Describe the steps of action potential generation

Answer 14

1. Resting State: -70 mV, Na⁺ and K⁺ channels closed.
2. Depolarization: Na⁺ channels open; Na⁺ enters → membrane becomes more positive.
3. Repolarization: Na⁺ channels close, K⁺ channels open; K⁺ exits → returns toward negative.
4. Hyperpolarization: K⁺ channels remain open briefly → membrane becomes more negative than resting.

Question 15

How is an action potential propagated down the neuron?

Answer 15

Depolarization at one segment of the axon triggers the next segment to depolarize, creating a wave of electrical activity moving down the axon.

Question 16

Define absolute refractory period.

Answer 16

Time during which a neuron cannot fire another action potential, regardless of stimulus strength (Na⁺ channels inactivated).

Question 17

Define relative refractory period

Answer 17

Period during which a neuron can fire another action potential only if the stimulus is unusually strong (K⁺ channels still open).

Question 18

Differentiate between excitatory and inhibitory postsynaptic potentials

Answer 18

Excitatory (EPSP): Depolarize the membrane; increase likelihood of action potential.

Inhibitory (IPSP): Hyperpolarize the membrane; decrease likelihood of action potential.

Question 19

Define saltatory conduction and how it differs from continuous conduction.

Answer 19

Saltatory Conduction: Rapid transmission in myelinated axons; impulse “jumps” between nodes of Ranvier.

Continuous Conduction: Slow transmission in unmyelinated axons; impulse moves steadily along entire membrane.

Question 20

What is a neurotransmitter?

Answer 20

A chemical messenger that transmits signals across synapses between neurons or from neurons to effectors.

Question 21

List the major classes of neurotransmitters with examples.

Answer 21

Acetylcholine: Acetylcholine (neuromuscular junctions).

Biogenic Amines: Dopamine, Norepinephrine, Serotonin.

Amino Acids: GABA, Glutamate, Glycine.

Peptides: Endorphins, Substance P.

Purines: ATP, Adenosine.

Gases & Lipids: Nitric Oxide (NO), Carbon Monoxide (CO), Endocannabinoids.