Anatomy of the Nervous System Nervous and Endocrine

Anatomy of the Nervous System

Nervous and Endocrine Systems work together to maintain homeostasis • • Nervous System Electrical signals FAST – milliseconds Short activity duration • Specific! • Endocrine System • Chemical signals – Hormones • Slow– sec. to hours • Longer activity duration • Travels through blood stream – not specific!

Functioning of the NS • Nerve impulses travel in 2 directions • Each direction uses a different set of nerves – Motor Nerves – Efferent (descending) • Take info AWAY from brain – Sensory Nerves – Afferent (ascending) • Take info TO the brain • The integrative function analyzes the sensory data and produces a response.

Nervous Tissue • Neurons (nerve cells) – Cell Body – Dendrites – Axon • Myelinated vs. Unmyelinated Saltatory impulses

Nervous Tissue (cont. ) • Neuroglial Cells (“nerve glue”) – Hold the structure of the nervous system together.

4 types of Neuroglial Cells • Microglial – • Small, phagocytic cells - go to injury/clean and engulf debris • Astrocytes – • stars – hold neurons together. Form bridges between neurons and capillaries.

Neuroglial Cells continued. . • Oligodendroglial – produce myelin sheath (protection) over neurons in CNS • Ependymal – line cavities, lubricates and protects. Produces and moves cerebrospinal fluid

A detailed look at the structure of a neuron… Motor Neuron

And a sensory neuron…

• What is the importance of the myelin sheath? • What are nodes of Ranvier?

Homework for WEDNESDAY • Read 237 -244 in your book • Do concept check questions on page 237! • We may have a short reading quiz tomorrow to check in!!!

Nerve Impulses • Axon membrane is POLARIZED when not active (at rest). – Potassium ions inside axon – Sodium ions outside axon – Negative organic ions inside

• Action potential = nerve impulse – Change in polarity flows down the axon’s membrane. – Depolarization – Na ions move into axon – Repolarization – K ions move out of axon

How does the info pass from one neuron to another? ? ? • Through the SYNAPSE – Gap between one neuron’s axon (synaptic knob) and another’s dendrite – This gap is called the SYNAPTIC CLEFT • Neurotransmitters (like acetylcholine and norepinephrine) pass the impulse from one neuron to the next

Neurological Disorders • Neurotransmitter imbalances – Huntington’s disease – nervous system degeneration (GABA dysfunction in brain) – Parkinson’s Disease – dopamine deficiency, tremors, unblinking expression – Alzheimer’s Disease – loss of neurons that use ACh

Reflex Arc • Unconscious motor response to a sensory stimulus. • Stimulation of sensory receptors evokes APs that are conducted into spinal cord. – Synapses with association neuron, which synapses with somatic motor neuron. • Conducts impulses to muscle and stimulates a reflex contraction. – Brain is not directly involved. Figure 8 -28