The peripheral nervous system, contains nerves and ganglia that operate outside of the brain and spinal cord. The central nervous system connects to the peripheral nervous system, and vicea versa. The peripheral nervous system has sensory nerous receptors.

The peripheral nervous system

The peripheral nervous system lacks the protection that the central nervous system, unlike the CNS it has no skull or vertebral column.

The peripheral nervous system is divided into the autonomic nervous system, and the somatic nervous system. The somatic system can be controlled voluntarily. The autonomic nervous system has been described as ‘self regulating’.

The autonomic nervous system is divided into sympathetic and parasympathetic functions.

The PNS has mechano and nocioceptors. The nocioceptors are also known as ” pain receptors”. The proces sis called ” nociception”. Nocioceptros were discovered by Charles Scott Sherrington in 1906. Sometimes pain is referred to as the perception of pain. As an example the nocioceptors on the reception of pain takes the signal through the spinal cord to the brain.

Once the pain signal reaches the spinal cord, the response is taken over by the efferent, or theneurons that take signals away from the CNS towards the muscle.

By contrast the afferent neurons are sensory neurons that carry nerve impluses from sensory stimuli towards the CNS.

The sympathetic nervous system can communicate with many different things at once, where as the parasymmpehtic tends to communicate more dierectly ?

The sympathetic nervous sytem is the bodies involunatry response to dangerous or stressful situations. We are all familiar with the symptoms of sympathetic nervous system activity: our heart rate increases, our breathing increases, and we may sweat.

The physiological response of the sympathetic of the nervous system for low level every day threats we exeprience has been compared to creating the same reaction as when we’re in survival.

A involuntary and rapid response to pain are called innate, or intrinsic reflexive actions. There’s also learned, or acquired reflexes that are built by experience.

Stretch receptors in a muscle are called ” muscle spindles”. Their role is to detect changes in the length of a muscle. These spindles communicate with the CNS via afferent nerve fibres. When these spindles are stimulated it triggers a contraction in the muscle to prevent it from stretching further.

Some neurons have channels that open when the membranes are stretched. This is called “mechanically gated” channels. A physical stimulus may do this.

There’s lignand gated channels that open when histamine or potassium ions which are released by dmaged tissues bind to the receptors.

Stimuli in the PNS is converted into electrical energy. At a certain level of electrical energy, an action signal

In the PNS there are:

satellite cells
schwann cells

A resting neuron is

In the perihperal nervous system, which is one of the two components that make up the nervous sytems in bilateral animals we’ve got satelite and schwann cells, which is the connectin between the braind and psinal cpord to the rest of the body.

The CNS is protected by the vertebral column, and skill, and blood-brain barrier.

The brain is resource intesive and consumed about 20% of the energy through it’s activity of th ebody.

TASTE

SMELL
Also called the gustraotry sense, or gustatory.