The Peripheral Nervous System

What is the peripheral nervous system?

Transmits information to and from the CNS

contains the somatic nervous system and autonomic nervous system

What is the somatic nervous system?

• Controls voluntary responses (Consciously controlled)

• Responsible for relaying sensory and motor information between the outside environment and the CNS.

• Any muscle movement or voluntary motor output uses the somatic nervous system

What is the autonomic nervous system?

• Controls involuntary responses (Unconsciously controlled)

• Mediates involuntary movement in the body

• innervates internal organs

• Controls vital functions:

  • Heart rate

  • Respiration and breathing

What is the layout of the somatic nervous system?

Transmits a nervous impulse from CNS to an end target organ (eg. skeletal muscle)

Only one neurone

What is the layout autonomic nervous system?

Transmits a nervous impulse from CNS to an end-target organ (eg. smooth muscle)

Two neurones

What are the divisions of the autonomic nervous system?

• sympathetic branch

  • primarily concerned with preparing the body for emergencies (fight or flight)

• parasympathetic branch

  • primarily concerned with replenishing stores, conserving energy and non-emergency tasks (rest and digest)

What are the functions of the autonomic nervous system?

• Control of involuntary activity and vital functions

• It innervates smooth & cardiac muscle, and secretory, glandular tissues e.g.

• Control of heart rate

• Control of airway diameter

• Control of secretions & motility in the gastro-intestinal tract

• Control of micturition (urination) through the urinary bladder

• Control of pupil diameter in the eye

• Control of glandular secretions (e.g. salivary, sweat, adrenal medulla)

• The autonomic nervous system is regarded as purely motor (efferent)

How is the autonomic nervous system organized?

• The preganglionic neuron releases acetylcholine (ACh), which binds to nicotinic ACh receptors on the postganglionic neuron.

• The postganglionic neuron then releases:

  • Noradrenaline (norepinephrine) in the sympathetic system, which binds to adrenergic receptors (α and β types).

  • Acetylcholine in the parasympathetic system, which binds to muscarinic ACh receptors.

How does the adrenal gland function in relation to the autonomic nervous system?

• The adrenal gland has two parts: an outer cortex and an inner medulla.

• The medulla acts as a sympathetic ganglion and is innervated by preganglionic neurons.

• It releases the catecholamine hormone adrenaline (epinephrine) into the bloodstream.