Nervous System

Functions of Nervous System• The nervous system is the major controlling,

regulatory, and communicating system in the body.

• It is the center of all mental activity including thought, learning, and memory.

• Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis.

• Through its receptors, the nervous system keeps us in touch with our environment, both external and internal.

Central Nervous System (CNS)• Includes Brain and

Spinal Cord• Responsible for

integrating motor and sensory information

• Seat of intelligence memory and emotion

Peripheral Nervous System (PNS)• Includes all nerve

tissue outside the CNS– Afferent division –

brings sensory information TO CNS

– Efferent division – sends commands FROM CNS to muscles and glands

Somatic Nervous System (SNS)• Part of the efferent

system of the PNS• Voluntary control

over skeletal muscles

A. Central nervous system B. Peripheral nervous systemB1. Somatic nervous systemB2. Autonomic nervous system

Diagram :

Autonomic nervous system (ANS)• Part of the PNS • Automatic regulation of smooth muscle, cardiac

muscle and gland activity or secretions

Cellular Organization in Neural Tissue

Neuron with synapse

Classes of Neurons

Neuron transmission – sending & receiving

Cellular Organization in Neural Tissue• Neuroglia

– Regulate environment around neuron

– Provide support for neural tissue

– Act as phagocytes– Aka glial cells– More numerous than

neurons

Neuroglia, aka glial cells

Diagram pg 201 (black book)• Interaction of neurons and glial cells

Neuroglia- Astrocytes• Most numerous• Maintain the blood brain

barrier• Repair damaged neural tissue

Neuroglia- oligodendrocytes• Create myelin• Improves the speed of impulse conduction on an axon

Neuroglia- microglia• Smallest and rarest• Phagocytic white blood cells• Protect neurons

Neuroglia- ependyma• Produce cerebral spinal fluid (CSF)

Neuroglia- Schwann cells• Most important glial cells• Also create myelin

Neurotransmitters• Chemical that send messages from neuron to

neuron or from neuron to other tissues– Ach – stimulates muscle contraction– Norepinephrine – creates an excited state in the

organism– Dopamine and serotonin – effects are inhibitory

Dopamine and CocaineCocaine is a mood-altering drug that interferes with normal transport of the neurotransmitter dopamine, which carries messages from neuron to neuron. When cocaine molecules block dopamine receptors, too much dopamine remains active in the synaptic gaps between neurons, creating feelings of excitement and euphoria.

Blood Brain Barrier• Maintained by astrocytes• Cause capillaries of CNS to

become impermeable to many compounds

• Example: some antibiotics can not help heal brain infections because they can’t cross the barrier

Great Animations to help

An Unbelievable Brain!!!