A&P I Chapter 11

Central Nervous System (CNS)

Brain & Spinal Cord

Peripheral Nervous System (PNS)

Cranial Nerves & Spinal Nerves and their branches

How many neurons does the brain have?

100 Billion

How many neurons does the spinal cord have?

100 million neurons

Cranial Nerves

12 pairs, travel to or from the brain

Spinal Nerves

31 pairs, travel to or from the spinal cord

Sensory Functions

Gather info about body’s internal and external environments. Sensory (Afferent) Division of PNS

Intergrative Functions

Analyze sensory input & decide on a response. Done by CNS (Mainly brain)

Motor Functions

Carry out the response. Done by the Motor (Efferent) Division of the PNS (Motor Efferent moves ME)

Somatic Senory Division

Signals from skeletal muscles, bones, joints, skin, and special senses

Visceral Sensory Division

Signals from visceral organs (heart, lungs, stomach, intestines, kidneys, urinary bladder)

About how much data is disregarded by the CNS after intergration?

99%

Somatic Motor Divison

Signals to skeletal muscle (voluntary motor division)

Visceral Motor Division (Autonomic Nervous System)

Signals to thoracic and abdominal viscera; controls smooth muscle, cardiac muscle, and some gland secretion (Involuntary Motor Division)

What is the split up of Nervous Tissue & ECM?

80% Nervous Tissue, 20% ECM

Neuroglial Cells

More numerous, smaller, supporting cells that don’t transmit signals

Cell Body

5–100 µm diameter; most metabolically active region; maintains cytoplasm and makes proteins

In Soma: What do free ribosomes and rough ER form?

Clusters called Nissl Bodies (proteins)

What is the cytoskeleton of intermediate filaments?

Neurofibrils (extend into dendrites and axon) help support the cell

Dendrites

–Receive input from other neurons and transmit it in the form of electrical impulses toward the cell body

–Possess most of the same organelles as the cell body

–Dendrites can grow and are “pruned” as a person matures and the demands on the nervous system change

Axons

Processes that can generate and conduct action potentials

Axon Hillock

Area of the cell body where the axon arises

Axon Collaterals

Branches of the axon

Telodendria

Fine branches of axon and its collaterals

Axon terminals

(Synaptic Knobs) Ends of telodendria, communicate with target cells (Typically 1000+)

Axolemma

Plasma membrane of the axon

Axoplasm

Cytoplasm of the axon, Contain mitochondria, intermediate filaments, vesicles, and lysosomes, but no protein making organelles.