Ch. 11 A&P I

what does the nervous system do?

controls how you sense the world, move, think, and maintain body balance (homeostaiss like heart rate, temp, breathing)

CNS vs PNS

CNS = brain + spinal cord (processing center)

PNS = all nerves outside CNS (communication lines)

3 functional divisions of nervous system

1. Sensory (afferent) → brings info IN

2. Integrative → processes info

3. Motor (efferent) → sends commands OUT

Somatic vs Visceral sensory

• Somatic = skin, muscle, senses (touch, sight, etc..)

• Visceral = internal organ (heart, stomach)

Somatic vs Autonomic motor

• Somatic = volunatry (skeletal muscle)

• Autonomic = involuntary (organs, glands)

3 main parts of a neuron

• Dendrites (receive)

• Cell body (process)

• Axon (send)

what is the soma (cell body)

Control center; makes proteins + keeps neuron alive

What are Nissl bodies

Rough ER → makes proteins

Dendrites function

Receive signals and send them to cell body

Axon function

Sends electrical signals away from cell body

Axon hillock

“Decision point” - where action potentials start

Axon terminals

Release neurotransmitters to next cell

Multipolar neuron

Many dendrites, one axon (MOST neurons)

Bipolar neuron

One dendrite + one axon (special senses)

Pseudounipolar neuron

One branch that splits → sensory neurons

Functional neuron types

Sensory → to CNS

Interneurons → within CNS

Motor → away from CNS

What do neuroglia do`

Support, protect, and help neurons

Astrocytes

Support neurons + help form blood-brain barrier

Oligodendrocytes

Make myelin in CNS

Microglia

Immune defense (eat debris/pathogens)

Ependymal cells

Make & circulate cerebrospinal fluid

Schwann cells

Make myelin in PNS

Satellite cells

Support neuron cell bodies in PNS

Myelin sheath function

Insulates axon → speeds up signals

Node of Ranvier

Gap in myelin where signal “jumps”

White vs gray matter

White = myelinated axons

Gray = cell bodies + dendrites

Resting memebrane potential

-70 mV (inside is negative)

Why is cell polarized?

Unequal charge across membrane

Na+/K+ pump?

Pumps 3 Na+ out 2K+ in (uses ATP)

Leak channels

Always open

Ligand-gated channels

Open when chemical binds

Voltage-gated channels

Open when voltage changes

Mechanically-gated channels

Open with pressure/stretch

Depolarization

Becomes LESS negative (Na+ enters)

Hyperpolarization

Becomes MORE negative

Local potentials

Small, short distance changes

Action potential

Big signal that travels entire axon (all-or-none)

Depolarization phase?

Na+ rushes in → positive

Repolarization phase?

K+ leaves → back to negative

Hyperpolarization phase

Too negative before returning to rest

How does ana ction potential travel?

Domino effect down axon (one triggers next)

Electrical synapse

Direct connection (gap junctions, fast)

Chemical synapse

Uses neurotrasmitters

Steps of Chemical Synapese

1. Action potential reaches axon terminal

2. Ca²+ enters

3. Vesicles release neurotransmitter

4. Neurotrasmitter binds receptor

5. Ion channels open

6. New signal starts in next cell