A&P: ch 11 Nervous System & Tissue

Part 1/3

Nervous System Fundamentals

What are the two major structural divisions of the nervous system?

• Central nervous system (CNS)

• Peripheral nervous system (PNS)

• What structures make up the CNS?

• What is the main function of the CNS?

• Brain and spinal cord.

• Integrative and control centers

• What structures make up the PNS?

• What is the function of the PNS?

• Cranial nerves and spinal nerves.

• Communication lines between the CNS and the rest of the body.

• How many pairs of cranial nerves are there?

• How many pairs of spinal nerves are there?

• 12 pairs

• 31 pairs

Information Collection (PNS)

• What is the role of sensory receptors?

• What do afferent neurons do?

• Afferent neurons are also called what?

• They respond to stimuli

• Link receptors to the CNS.

• Sensory neurons.

• What are the two categories of sensory input?

• What does somatic sensory include?

• Somatic sensory and visceral sensory

• General senses and specialized senses

What does visceral sensory monitor?

Blood vessels and viscera

Information Evaluation (CNS)

• What is the integration center?

• What structures usually act as the integration center?

• The part of the CNS that determines the appropriate response to stimuli.

• Usually the brain, occasionally the spinal cord.

• What do efferent neurons do?

• Efferent neurons are also called what?

• What are effectors?

• Link the CNS to effectors

• Motor neurons

• Muscles or glands

• What are the two forms of motor output?

• What does the somatic motor system control?

• Is somatic motor control voluntary or involuntary?

• Somatic motor and autonomic motor

• Skeletal muscles

• Voluntary

• What does the autonomic motor system control?

• Is autonomic motor control voluntary or involuntary?

• Cardiac muscle, smooth muscle, and glands

• Involuntary

Cytology of Nervous Tissue — Neurons

• What is another name for the neuron cell body?

• What is the function of the cell body?

• What structures are found in the neuron cell body?

• Soma

• Integration center

• Nucleus, nucleolus, and chromatophilic substance

• What is the function of dendrites?

• Are dendrites usually short or long?

• Are dendrites single or multiple?

• What covers dendrites?

• Input/afferent function

• Generally short

• Multiple

• Dendritic spines

1. What is the function of the axon?

2. Are axons generally short or long?

3. What do axons form?

1. Output/efferent function

2. Generally long

3. Nerves

1. Does a neuron usually have one or multiple axons?

2. What are axon collaterals?

3. What is found in synaptic knobs?

1. Single axon

2. Branches of the axon

3. Neurotransmitters

Categories of Neurons

1. What structural type are most sensory neurons?

2. What characterizes pseudounipolar neurons?

• Pseudounipolar

• Single process and the nucleus is not the integrating center

• What structural type are neurons involved in specialized senses?

• What characterizes bipolar neurons?

• Bipolar neurons

• Two processes

• What structural type are most motor neurons?

• What characterizes multipolar motor neurons?

• Multipolar neurons

• Multiple short branched dendrites and a single long axon

• What structural type are most interneurons?

• What characterizes interneurons?

• Multipolar

• Highly branched with no long extensions

Glial Cells — PNS

• What glial cells form myelin in the PNS?

• What is another name for Schwann cells?

• What do Schwann cells form around axons?

• Schwann cells (neurolemmocytes)

• Neurolemmocytes

• Myelin sheath

• What are satellite cells?

• What is a ganglion?

• What is the function of satellite cells?

• Flattened cells wrapped around neuron cell bodies in ganglia

• A cluster of neuron cell bodies in the PNS

• Nutrient and waste exchange

Glial Cells — CNS

• What glial cells form myelin in the CNS?

• What is unique about oligodendrocytes?

• Oligodendrocytes

• They form myelin around multiple axons

• What is the function of microglia?

• Which glial cells are the least abundant?

• Phagocytosis

• Microglia

• Which glial cells are the most abundant?

• What do astrocytes look like?

• What major structure do astrocytes form?

• What is the function of the blood-brain barrier?

• Astrocytes

• They have star-like projections

• Blood-brain barrier

• Regulates passage of molecules from the blood

1. What type of epithelium are ependymal cells?

2. What do ependymal cells form?

3. What does the choroid plexus produce?

4. What is the function of ependymal cell cilia?

1. Simple cuboidal

2. Choroid plexus

3. CSF (cerebrospinal fluid)

4. Move CSF

Myelination

1. What is myelin made of?

2. Why does myelin appear white?

3. What is white matter?

4. What is gray matter?

1. Cell membrane with high lipid content.

2. Because of its high lipid content

3. Myelinated nervous tissue

4. Unmyelinated nervous tissue

• What effect does myelin have on nerve impulse conduction?

• What is salutatory conduction?

• What are the gaps in myelin called?

• It greatly increases the speed of action potentials down axons.

• The action potential “jumps” from gap to gap along the axon

• Nodes of Ranvier

• What is another name for nodes of Ranvier?

• Why does myelin increase conduction speed?

• Are action potentials faster in myelinated or unmyelinated axons?

• Neurofibril nodes

• Because impulses jump from node to node instead of traveling continuously

• Myelinated axons

Nerves

• What is a nerve?

• What is a mixed nerve?

• A bundle of fascicles surrounded by epineurium

• A nerve carrying both sensory and motor impulses.

• What is a fascicle?

• What else is found in fascicles?

• A bundle of axons surrounded by perineurium

• Blood vessels

• What is an axon in a nerve?

• What surrounds an individual myelinated nerve fiber?

• An individual myelinated nerve fiber surrounded by endoneurium

• Endoneurium

Nervous System Disorders

• What is multiple sclerosis?

• What causes multiple sclerosis?

• Why do symptoms of multiple sclerosis vary?

• Progressive destruction of myelin in the brain and spinal cord.

• Appears to be an autoimmune disease.

• Variable severity and areas affected.

Nerve Regeneration

• Can nerves regenerate in the PNS?

• What factors affect PNS regeneration?

• How do Schwann cells help regeneration?

• Yes, if the cell body is intact

• Amount of damage and distance from the innervated cell

• Release growth factors and provide tracks

• Is regeneration limited in the CNS?

• Why is CNS regeneration limited?

• What else limits CNS regeneration?

• Yes

• Oligodendrocytes do not release growth factors

• Axon density and scar tissue