A&P II: The Neural System

Tract

Part of CNS

Equivalent of nerves

Nucleus

Part of CNS

Equivalent of ganglia

Afferent

towards CNS

Efferent

away CNS

Ganglia

Part of PNS

Neuron cells that connect nerves

Nerves

Part of PNS

Bundles of axons that carry signals

Axon Hillock

Origin of the axon

Initial segment

region right after axon hillock

Axolemma

plasma membrane of an axon

Telodendria

branches of an axon

Axon terminal

ends of axon branches

Two axon segments responsible for reaching threshold

Axon Hillock and Initial Segment

Cell Body

Nissi body = rough ER + ribosomes

__ caries energy towards the cell body to neurotransmitters

Dendrites

Somatic nervous system

Skeletal muscle

Ex. movement, sensory information from skin, muscle, joints

Autonomic Nervous System

Automatic organ tissue

Ex. Muscle, fat tissue, glands

Sympathetic division

mobilizing body for activity

Parasympathetic division

Used during rest / digestion

Sympathetic and parasympathetic division are part of which nervous system class?

autonomic

Enteric Nervous System

Controls digestive tract

3 Receptor types

1. Interoreceptors

2. Exteroreceptors

3. Proprioceptors

Proprioceptors

Monitor where the body is in space

Gray vs white matter (in the brain)

Processing vs communication

Gray matter composed of

1. Neuron cell bodies

2. Dendrites

3. Synapses

4. Axons

White matter composed of

1. myelinated axons

multipolar neurons

many dendrites + 1 axon

bipolar neurons

1 dendrite + 1 axon + cell body

Unipolar neurons

one main process from the cell body

Anaxonic neurons

multiple processes and NO axon

Function classes of neurons

1. Sensory

2. Motor

3. Interneurons

Sensory neurons

Afferent

Motor neurons

efferent

Interneurons are

in the CNS

Astrocytes

1. Part of CNS

2. Regulate blood-brain barrier

Oligodendrocytes

1. Part of CNS

2. Myelinate CNS

Microglia

1. Part of CNS

2. ‘CNS Immune defense’

Ependymal cells

1. Part of CNS

2. Produces cerebrospinal fluid

Cerebrospinal fluid (CSF)

provides protection, waste transport, and chemical environment to the brain

Myelin

fat, insulating material that catalyzes conduction in the nervous system

Nodes vs Internodes

Gaps in myelinated regions vs myelinated regions

Schwann Cells

1. Part of PNS

2. Myelinate neurons in PNS

How do Shwann cells myelinate neurons in the PNS?

1. Schwann cells surround and wrap around a portion of the axon

2. Wrap repeatedly to form myelin sheath

**Schwann cells can surround without myelination

Satellite cells

1. Part of PNS

2. Surround neurons in ganglia to regulate neurotransmitter, oxygen, and CO2 levels

__ Nerve regeneration is faster

PNS

Process of PNS nerve regeneration

1. Axon injured

2. Nerve breakdown

3. Schwann cells multiple rapidly

4. Macrophages clean up

5. Surviving proximal axon grows

6. Axon surrounded by schwann cells

Distal degeneration

nerve breakdown

Membrane potential

difference in charges between extracellular and cytosol

resting membrane potential of neuron

-70 mV

Potassium is pushed __ a cell by membrane potential

Out

Sodium is pushed __ a cell by membrane potential

in

Sodium potassium pump uses 1 ATP to transport __ NA+ per every __ K+

3 ; 2

Depolarizing

membrane gets less negative and closer to action potential

hyperpolarizing

Membrane gets more negative

repolarization

membrane potential moves back toward resting value after depolarization

Threshold (definition + value)

1. Voltage for action potential

2. -60 mV

Graded potentials are located in

dendrites / cell bodies

action potentials are located in

axons

Graded potential uses what type of ion channel?

Ligand gated

Continuous conduction

1. In unmyelinated axons

2. Slower

saltatory conduction

1. I myelinated axons

2. Depolarization jumps node to node = faster

absolute refractory period vs relative refractory period

1. The time after an action potential where another action potential is impossible

2. The time after an action potential where another action potential is possible but requires stronger stimulus