Feb 28 - Organization of the Nervous System

What are the divisions of the Nervous System and what structures are associated with each?

1. Central Nervous System

   1. brain

   2. spinal cord

2. Peripheral Nervous System

   1. all other nerves throughout the body

What are the divisions of the PNS and what do they do?

Autonomic Nervous System

• communicates with internal organs and glands

Somatic Nervous System

• communicates with sense organs and voluntary muscles

What are the divisions of the Autonomic Nervous System and what do they do?

1. Sympathetic Divison (Arousing)

2. Parasympathetic Division (Calming)

What are the divisions of the Somatic Nervous System and what do they do?

1. Sensory Nervous System

   1. Sensory input - Afferent

2. Motor Nervous System

   1. Motor output - Efferent

Neuron

transfers and processes information

multipolar, bipolar, unipolar

excitable tissue

Neuroglia

supporting cells

• protect the neuron

• non-excitable tissue

• phagocytes

Phagocytic

A cell that engulfs and digests particles(debris, dead cells, pathogens)

Excitable vs Non-Excitable Tissue

Excitable Tissue:

• specialized tissue

• generate and transmit electrochemical signals(ATP)

• movement, sensation and perception, coordination and control

• eg. nervous and muscle tissue

Non-Excitable Tissue

• can not generate and transmit electrical signals

• eg. epithelial and connective tissue

Nerve

bundle of fibres that can send and receive electrochemical signals (ATP)

Dendrites

branched extension of nerve cells that receive impulses from other cells at synapses

Axons

cord connecting cell body to axon terminal

Myelin Sheath

sheets of myelin that insulates the axons of neurons

allows electrical signals to travel quicker and efficiently

Compare and contrast Neurons from Neuroglia

Neurons:

• Transfers, conduct, and processes information

• Typical structure(nucleus, cell body, dendrites, axon, etc.)

• Multipolar, Bipolar, Unipolar

• Excitable Tissue

Neuroglia

• Supporting cells

• Protect the neuron

• Phagocytic roll

• Non-Excitable Tissue

Compare and contrast Neurons from Nerves

Neurons

• Cell of the NS that transmits information

Neve

• Many axons bundled together in PNS

Compare and contrast Nuclei from Ganglion

Nuclei

• Group of neuron cell bodies in CNS

Ganglion:

• Group of neuron cell bodies in PNS

• relay stations for transmitting info

White Matter

Transmits information → quicker bc myelinated

Tissue made up of myelinated nerve cells

Grey Matter

Processes and interprets information

Unmyelinated cell bodies

Ependymal Cells

line ventricles of brain

• assist in production and circulation of CSF

• help form choroid plexus

Astrocytes

• contribute to blood brain barrier

• structural + metabolic support to CNS

• repair damage to nerve cells in CNS

Oligodendrocytes

• support and insulation to axons in CNS(via myelin sheaths)

Microglia

defend neurons from pathogens

Functions:

• removal of damaged neurons, infectious, neuroglia

• prevention of inflammation by removing infectious agents right away

Satellite Cells

• covers neuron cell bodies in ganglia in PNS

• separate cellbodies from interstitial fluid

• regulate nutrient exchange and waste btwn nucleus and environment

Schwann Cells

• forms myelin sheaths around PNS axons

What are the two types of neuroglia in the PNS?

Satellite Cells, Schwann Cells

What are the four types of neuroglia in the CNS?

Ependymal Cells, Astrocytes, Oligodendrocytes, Microglia

Synapse

Junction between a neuron and another cell allowing the transmition of info

• initiating neuron → presynaptic membrane

• Recieving membrane → postsynaptic membrane

Neuroglandular Synapse

synapse between a neuron and gland cell

Neuromuscular synapse

synapse between neuron and muscle cell

What are the two types of Synapses? Compare and contrast the two

Chemical Synapse and Electrical Synapse

Chemical Synapse

synaptic vesicles that relay impulses

impulse conveyed in one direction

Electrical Synapse

linked to a postsynaptic cell by gap junctions

impulses conveyed in any direction

List the steps in the polysynaptic reflex arc. Define which steps are part of the ascending and descending pathway

Ascending:

1. stimulus activate sensory receptors

2. info travels along afferent sensory neuron

3. neuron enters spinal cord via interneuron

4. Information splits

   1. immediate response → synapse with motor neuron

   2. slow response —> synapse with interneurons that synapse with ascending pathways to higher brain centres

Descending:

5. motor neuron exits spinal cord via interneuron

6. travels to effector muscle

7. effector muscle contracts