Neural & Hormonal Systems

Module 3

What are neurons, and how do they transmit information?

• The nervous system consists of billions of individual cells called neurons.

• A neuron receives signals from other neurons through its branches (dendrites) and cell body (soma). They combine these signals in the cell body (soma) and transmit an electrical impulse (action potential) down its axon.

How does a neuron communicate with other cells to influence our

behavior?

• When electrical signals reach the end of the axon, they stimulate the release of chemical messengers (neurotransmitters).

• These molecules pass on their excitatory or inhibitory messages as they traverse the synaptic gap between neurons and combine with receptor sites on neighboring neurons.

Neurotransmitters

• Researchers are studying neurotransmitters to discern their role in behavior and emotion.

• Dozens of different neurotransmitters are now well understood.

• Learning about endorphins, the feel-good neurotransmitters, has helped us understand how drugs affect our brain chemistry.

Neurons & How They Work!

What are the elementary components of our nervous system, and what are

the functional divisions of that system?

• Neurons are the elementary components of our nervous system, our body’s speedy electrochemical information system.

• Two main divisions of the nervous system:• Central Nervous System• Peripheral Nervous System

Central Nervous System

• The spinal cord is an information highway connecting the peripheral nervous system to the brain.

• Ascending neural tracts send up sensory information, and descending tracts send back motor-control information.

• Spinal cord neurons = interneurons.

Peripheral Nervous System

• Has two main divisions:• Somatic nervous system – directs voluntary

movements and reflexes of skeletal muscles• Autonomic nervous system – through its

sympathetic and parasympathetic divisions, controls our involuntary muscles and glands. • Sympathetic – Arousing• Parasympathetic – Calming

How does the endocrine system deliver its messages?

• “The body’s slower communication system.”

• Hormones released by the glands of the endocrine system travel through the bloodstream and affect other tissues, including the brain.

• The endocrine system’s master gland, the pituitary, influences hormone release by other glands.

• The adrenal glands are activated in stressful times by the autonomic nervous system.