The Peripheral Nervous System

PNS – yep it sounds like your saying penis

If you liked that one you will love the ANS -anus

The Peripheral Nervous SystemTalk or chew and not bite our tonguesUse right and left hands to play pianoUse right and left hands to tie a shoelace

All examples of different activities done simultaneously.

The co-ordination by the brain of different parts of our nervous system enables us to perform all these behaviours in a fluent way.e.g. Neurons carrying messages from the brain about jaw movement stay in close contact with those that convey information about tongue muscle movements.

CNS and the PNSRoles of CNS are to integrate and co-ordinate all incoming neural

information and to initiate messages sent to different parts of the body. It does NOT have direct contact with the outside world.

The CNS relies on the PNS to provide it with information about both the external world and the body’s internal environment and to carry messages from the CNS to various parts of the body.

“Peripheral” means outlying or surrounding.

The PNS is the entire network of nerves located outside the CNS.

The PNS extends from the top of the head, throughout the body to the tips of the fingers and toes and to all parts of the skin.

Central vs Peripheral

Central NS is includes the brain and the spine

Peripheral NS includes everything outside of the CNS

Two main functions of PNSTo carry information

from the sensory organs and internal organs to the CNS.

To convey information from the CNS to the muscles, organs and glands.

The PNS enables communication between the CNS and all other

parts of the body outside the brain and spinal cord.

The Peripheral Nervous SystemIn the human nervous system, messages can only travel in one

direction along the neuron.

To accommodate this, the PNS has 2 different pathways for communicating information to and from the CNS.One of these pathways consists of a set of neurons

- the sensory neurons –that carry information from sensory organs, muscles and internal organs to the CNS.

The other pathway consists of a set of neurons- the motor neurons – that carry instructions or messages from the CNS to muscles, organs and glands.

The messages carried by motor neurons enable us to move our muscles, cause glands to release hormones and activate internal organs such as the lungs to expand and contract so we can breathe.

The Nervous SystemCentral Nervous

SystemPeripheral

Nervous System

Somatic Nervous System

Autonomic Nervous System

Brain Spine

Motor function

Sensory function

Sympathetic Nervous System

Parasympathetic Nervous

System

The Somatic BranchThe word soma means body!

Motor information from the brainVoluntary movement

Sensory information to the brainSense data from skin, body etc.

Afferent – to the brain

Efferent – from the brain

SAME – sensory nerves are afferent, motor nerves are efferent

The Somatic Nervous SystemFeel heat of wood fire due to co-ordination of PNS and CNS.

Heat from fire is received by sensory neurons (“receptors”) in the skin which are part of the PNS.

The sensory neurons then transmit the info to the CNS.

The somatic nervous system is a subdivision of the PNS that controls the skeletal muscles attached to our bones. e.g. Enabling us to perform voluntary functions – scratch an itch, talk, ride a surfboard, dance, chew, wriggle toes.

These muscles typically produce observable bodily movement as they expand or contract in response to messages received from the CNS.

The Somatic Nervous SystemThe neural message begun in the CNS is carried along a network of

motor neurons to the muscle(s).

When the neural message reaches the muscle, a neurotransmitter is released.

Neurotransmitters are chemical substances that, in this instance, assist in the transmission of a neural message from the neuron to the muscle.

The release of the neurotransmitter onto the muscle causes the muscle to expand or contract, resulting in the required movement.

Skeletal muscles are completely inactive in the absence of neural input (i.e. Neural messages from motor neurons).

The Somatic Nervous SystemResearch studies on people who’ve permanently lost limbs in

accidents provide valuable information about the somatic nervous system.

Paraplegia results when the spinal cord prevents any communication between the somatic nervous system and the CNS.

Damaged spinal cord nerves do not regenerate so the loss of voluntary movement to and sensory messages from all parts of the body below the point of severing is permanent.

Paraplegia - loss of voluntary control of lower part of body – both legs, some cases loss of bowel and urinary bladder control.

Quadriplegia results when the spinal cord is severed above the spinal nerves that control the arms and legs, thus preventing movement below the neck.

The Autonomic Nervous SystemThe Autonomic Nervous System is the other subdivision of

the PNS that is actively involved when experiencing emotions such as fear, anger and excitement at very intense levels.

The Autonomic Nervous System is a network of nerves that connects the CNS to the body’s internal organs (e.g. heart, stomach, liver) and glands (e.g.sweat, salivary and adrenal) providing feedback to the brain about their activities.

The ANS is called “autonomous” because many of the organs, glands and processes under its control are self-regulating and not usually under voluntary control.e.g. Heartbeat, breathing, digestion, perspiration

The Autonomic Nervous SystemThe muscles involved in activity of internal organs

and glands (called “visceral muscles”) have built-in mechanisms for generating activity and are not dependent on voluntary control by the brain.

The ANS functions continuously – whether awake or asleep, active or under anaesthetic or in a coma.

Regardless of our level of awareness, the ANS keeps the vital organs and systems of our body functioning, thus maintaining our survival.

The Autonomic Nervous SystemThe somatic nervous system initiates

skeletal muscle movement.

The autonomic nervous system regulates the activity of the visceral muscles, organs and glands.

The messages carried between CNS and the visceral muscles, organs and glands either increase or decrease their respective activities to meet varying demands placed on the body.

The Autonomic Nervous SystemThe ANS is not completely self-regulating. There are

a few responses we can voluntarily control at certain times. e.g. blinking, heartbeat, breathing rate.

Some people have learned techniques to control specific autonomic responses. e.g. Yogis in India (Hindu men who practise yoga) increased heartbeat from a normal 75 bpm to 300 bpm without any physical activity or can slow it down to 50 bpm. Some can control their body temperature where one side of hand is warm and the other side cold.

BIOFEEDBACK Biofeedback training is a technique to learn to control autonomic

responses.

Biofeedback is a process by which a person receives information (“feedback”) about the state of an internal bodily activity that normally occurs automatically and then uses thought processes to exert control over that activity.

A monitoring device connected to the person provides feedback about the state of the autonomic response being controlled.

The person learns a strategy such as relaxation and/or visualisation to control the autonomic response.

It has been used to help people manage stress related problems such as high blood pressure, chronic pain and migraine headaches.

http://www.youtube.com/watch?v=A_Xh8vv1Dds&feature=related

The Autonomic Branch Connected to internal organs, not consciously

controlled. Keeps us alive – automatically.

Sympathetic branch controls arousal, fight or flight response / fires us up. Release of adrenaline, heart up, breathing up etc.

Parasympathetic calms back down, keeps at stable level. Digestion resting etc.

Sympathetic Nervous SystemPart of the ANSActivates internal muscles, organs and glands to

prepare the body for vigorous activity, or to deal with a stressful or threatening situation.

Enhances survival by providing an immediate response, in a split second, to any kind of emergency.

Perceive emergency; neurons in sympathetic nervous system activate target organs and glands to respond in required way.

Glands activated are two adrenal glands (located just above both kidneys).

Sympathetic Nervous SystemThe adrenal glands secrete hormones adrenaline and

noradrenaline into the bloodstream which then circulate around body complementing and enhancing effects of sympathetic nervous system by activating various muscles, organs and other glands (e.g. Sweat) in preparation for dealing with the emergency.

Heart rate increases Blood pressure increases Breathing rate increases to get more oxygen in Sugar and fat released from storage for instant energy to skeletal

muscles Pupils dilate to allow more light to enter eye and enhance vision Sweat glands increase production of sweat to cool the body Digestive process is slowed down

GOOSEBUMPS and BLUSHING!

Parasympathetic Nervous SystemPart of ANSCounterbalances activites of the sympathetic

nervous systemHas 2 main functions:

keeps systems of body functioning efficientlyIn times of minimal stress and in absence of

threats, helps body to maintain internally a steady, balanced state of normal functioning (known as homeostasis)Restores body to a state of calm, once the need for the sympathetic nervous system has passed.

Parasympathetic Nervous SystemDominates over sympathetic nervous system most of the time.

Operates when:e.g.Eat – stimulates stomach and intestine to digest foodProtects visual system through production of tears or pupil

constriction in bright light

Once danger has passed, the parasympathetic nervous system takes over and enables body systems to gradually return to normal.

Return to normal takes longer than activation of sympathetic nervous system which is immediate. This is due to the lingering presence of hormones released by sympathetic nervous system activation. They remain in the bloodstream for some time after the threat has passed.

Autonomic function – sympathetic and parasympathetic

Living while brain dead… thanks to the PNS Carol Ann Quinlan April 1975 became unconscious after

coming home from a party Consumed sedatives and alcohol stopped breathing twice for 15

minutes or more Went into a persistent vegetative state Kept alive on a ventilator for several

months Removed from mechanical ventilation

during 1976 Persistent vegetative state for almost

a decade until her death from pneumonia in 1985.

Autonomic branch of the ANS kept her ‘alive’

Living while brain dead… thanks to the PNS Terri Schiavo Heart attack on February 25,

1990 massive brain damage due to lack

of oxygen two and a half months in a coma Diagnosed as a persistent

vegetative state Kept alive via a feeding tube Court case lasted 7 years before

her husband won the right to have her feeding tube disconnected

Terrie died on March 31 2005 The Autonomic branch of the ANS

kept her ‘alive’

Left: CT scan of normal brain; Right: Schiavo's 2002 CT scan, showing loss of brain tissue. The black area is liquid, The small white piece in the right image is the Thalamic stimulator implanted in her brain to help suppress tremors and spasms

Persistent Vegetative statesPatients in a vegetative state may have

‘awoken’ from a comaPatient has NOT regained awareness Patients can open their eyelids occasionally

and demonstrate sleep-wake cyclesCompletely lack cognitive functiondiagnosis, made after numerous neurological

and other tests, that due to extensive and irrevocable brain damage a patient is highly unlikely ever to achieve higher functions above a vegetative state

What can a person in PVS do?PVS patients' eyes might be in a relatively fixed position, or

track moving objects, or move in a disconjugate (i.e. completely unsynchronized) manner

They may experience sleep-wake cycles, or be in a state of chronic wakefulness

They may exhibit some behaviours that can be construed as arising from partial consciousness, such as grinding their teeth, swallowing, smiling, shedding tears, grunting, moaning, or screaming without any apparent external stimulus

Individuals in PVS are seldom on any life-sustaining equipment other than a feeding tube because the brainstem, the centre of vegetative functions (such as heart rate and rhythm, respiration, and gastrointestinal activity) is relatively intact

Fight or FlightIt is sympathetic arousal!In response to a real or imagined threatPhysical or psychological danger