Nervous System Functions, Structure, and Impulse Transmission

What are the 3 main functions of the nervous system?

Sensory input, integration, motor output

What does sensory input do?

Detects changes (stimuli)

What does integration do?

Processes information and makes decisions

What does motor output do?

Stimulates muscles and glands

What makes up the CNS?

Brain and spinal cord

What makes up the PNS?

Cranial nerves and spinal nerves

What is the function of the afferent division?

Carries sensory info TO CNS

What is the function of the efferent division?

Carries motor signals FROM CNS

What does the somatic nervous system control?

Voluntary skeletal muscles

What does the autonomic nervous system control?

Involuntary organs and glands

What is the cell body (soma)?

Contains nucleus and organelles

What is the function of dendrites?

Receive signals

What is the function of the axon?

Sends signals

What is the axon hillock?

Where the axon begins

What do axon terminals do?

Release neurotransmitters

What is myelin?

Insulating layer around axons

What is the function of myelin?

Speeds up impulse conduction

Who makes myelin in the PNS?

Schwann cells

Who makes myelin in the CNS?

Oligodendrocytes

What are nodes of Ranvier?

Gaps in myelin sheath

What is the structure of a multipolar neuron?

Many dendrites, one axon

What is the structure of a bipolar neuron?

One dendrite, one axon

What is the structure of a unipolar neuron?

One process with two branches

What is the function of a sensory neuron?

Carry signals to CNS

What is the function of a motor neuron?

Carry signals to muscles/glands

What is the function of an interneuron?

Connect neurons within CNS

What is the function of neuroglia?

Support, protect, nourish neurons

What is the function of astrocytes?

Blood-brain barrier, support

What is the function of microglia?

Immune defense

What is the function of ependymal cells?

Help regulate CSF

What is the function of satellite cells?

Support neuron bodies in PNS

What is membrane potential?

Electrical charge across membrane

What is the resting membrane potential value?

-70 mV

Where is Na⁺ concentration higher?

Outside the cell

Where is K⁺ concentration higher?

Inside the cell

What does the Na⁺/K⁺ pump do?

Moves ions to maintain gradients

What is the exact movement of the Na⁺/K⁺ pump?

3 Na⁺ out, 2 K⁺ in

Does the Na⁺/K⁺ pump require energy?

Yes (ATP)

What is an action potential?

Electrical impulse in a neuron

What is threshold?

-55 mV

What causes depolarization?

Na⁺ entering cell

What causes repolarization?

K⁺ leaving cell

What is hyperpolarization?

Membrane becomes more negative than resting

What restores resting potential?

Na⁺/K⁺ pump

What is the all-or-none law?

Action potential either fully happens or not at all

What is a local potential?

Small, graded change in membrane

What is the refractory period?

Time when neuron cannot fire again

What is the absolute refractory period?

Cannot generate another action potential

What is the relative refractory period?

Requires stronger stimulus