Principles of Health Science 2012

Peripheral Nervous System

Peripheral nervous system is made of all of the nerves.

PNS consists of cranial nerves and spinal nerves.

•12 pairs and their branches•Originate in the brain

Cranial Nerves

Some are responsible for special senses such as sight, hearing, taste, and smell.

Some receive general sensations such as touch, pressure, pain, and temperature, and send out impulses for involuntary and voluntary muscle control

•31 pairs and their branches•Carry messages to and from the spinal cord•Both sensory (afferent) and motor (efferent) nerves

Spinal Nerves

•Consists of the following pairs:

•8 cervical•12 thoracic•5 lumbar•5 sacral•1 coccygeal

Each nerve goes directly to a particular part of the body or networks with other spinal nerves to form a plexus that supplies sensation to a larger segment of the body.

•Important part of the peripheral nervous system•Helps maintain a balance in the involuntary functions of the body BUT also allows the body to react in times of emergency

Autonomic Nervous System

There are two divisions of the ANS: Sympathetic

Parasympathetic

•Sympathetic and parasympathetic work together •Functions include:

1. Maintain a balanced state (homeostasis)

2. Control involuntary body functions at proper rates

•Acts in times of emergency: fight or flight•Prepares body to act•Increases heart rate and respirations•Raises blood pressure•Slows activity in digestive tract

Sympathetic Nervous System

•Counteracts actions of sympathetic after the emergency•Slows heart rate and respirations•Lowers blood pressure•Increases activity in digestive tract

Parasympathetic Nervous System