APSC 530 Nervous System Part 1

12

______ pairs of cranial nerves emerge from the base of the brain through foramina of the skull.

axons

A nerve is a bundle of hundreds or thousands of ________, each of which courses along a defined path and serves a specific region of the body.

31

_____ pairs of spinal nerves emerge from the spinal cord, each serving a specific region of the body.

neurons

Ganglia are groups of cell bodies of ________ located outside the brain and spinal cord

Sensory (Afferent) Neurons

-sense changes in the internal and external environment through sensory receptors

-transport sensory information from skin, visceral organs, muscles, etc. to CNS

Association/ Interneurons

-analyze sensory information, store some aspects, and make decisions regarding appropriate behaviors

-~90% of all neurons

-connect sensory to motor neurons

Motor (Efferent) Neurons

-respond to stimuli by initiating action

-send motor nerve impulses to muscles and glands

Neurons

-functional cells of the nervous system.

-Transmit information from one part of the body to another.

-unique ability to transmit action potentials

Neuroglia

—support cells.

–Half of the volume of the CNS

–Smaller cells than neurons

–Fifty times more numerous than neurons

Cells can divide

Gliomas

tumors that result from rapid mitosis of neuroglia

Cell Body

central part of the neuron that contains the nucleus and most of the organelles.

Also composed of:

-nissl bodies= assist in protein synthesis

-neurofilaments= for shape & structure

-microtubules= for material mvmt

Dendrites

-extensions that come off the cell body

-Conduct impulses towards the cell body

-Typically short, highly branched and unmyelinated

-Contains neurofibrils and Nissl bodies

Axons

-extensions that come off the cell body

-Conducts impulses away from cell body

-Long, thin cylindrical process of cell

Myelin Sheath

-A multilayered lipid and protein covering that surrounds the axons of most neurons

-is produced by Schwann cells and oligodendrocytes.

-electrically insulates the axon and increases the speed of nerve impulse conduction

Neurolemma

is the cytoplasm and nucleus
of the Schwann cell

Oligodendrocytes

myelinate axons in the CNS

Leakage Channels

gates open and close constantly allowing specific ions to diffuse through

–specific types we’ll consider: Na, K, and Ca

–nerve cells have more K⁺ than Na⁺ leakage channels

–as a result, membrane permeability to K⁺ is higher

–explains resting membrane potential of -70mV in nerve tissue

Gated Channels

•open and close in response to a stimulus

–specific types we’ll consider: Na⁺, K⁺, and Ca²⁺

–results in neuron excitability

Active Transport Channels

–Na⁺/K⁺ ATPase pump

Voltage-gated channels

Ion Channels

respond to a direct change in the membrane potential

Ligand-gated Channels

Ion Channels

•respond to a specific chemical stimulus. Fig. 12.11 b

•Type we’ll consider: Na⁺ channels responding to the neurotransmitter acetylcholine

Mechanically Gated Ion Channels

Ion Channels

respond to mechanical vibration or pressure.

Slow Axonal Transport

Axonal Transport Systems

-movement in one direction only-: AWAY from cell body

- 1-5 mm per day

Fast Axonal Transport

Axonal Transport Systems

moves organelles and materials along surface of

microtubules

• 200-400 mm per day

• transports in either direction

• substances to be used/recycled in cell body

Is also the route toxins and pathogens reach neuron cell bodies!

Tetanus

This disease disrupts motor neurons causing painful muscle spasms

1. Sensory (afferent) neurons

2. Interneurons/ Association Neurons (90% of all neurons)

3. Motor (efferent) neurons

Name 3 the types of neurons

Myelin Sheath

-Produced by oligodendrocytes and schwann cells

-surrounds axons

Neurolemma

The cytoplasm and nucleus of the Schwann cell

White

Myelinated axons are _____matter

Multiple Sclerosis

Diabetes Mellitus

What diseases can cause degeneration of myelin sheaths?

Unmyelinated Axons

-rest in invaginations of Schwann cells or

oligodendrocytes.

– gray matter

1. Dendrites

2. Axon Terminals

3. Neuroglia

4. Nerve Cell bodies

5. Bundles of unmyelinated axons

What are 5 examples of gray matter?

1. Action Potentials

2. Graded Potentials

2 types of electrical signals

________ can travel long distances

________ local membrane changes only

-70 mV

What is the value for resting membrane in nerve tissue?

POlarized

Positive Outside

At rest the membrane is polarized: POPO meaning

Depolarization

causes the inside of the cell to become less negative and the outside to become more positive

Hyperpolarization

-membrane has become more negative than it was at rest.

-MORE polarized than it was before

Dendrites; Cell body

Graded potentials most often occur in the ______ and __________ of a neuron.

1. Mechanical Stimulation of mechanically gated ion channels due to PRESSURE

2. Chemical Stimulation of ligand gated channels due to NEUROTRANSMITTERS

The 2 sources of stimuli are