Nervous System

 

Introduction

Learn all about the human nervous system. 

There are a total of 3 learning objectives, each learning objective contains information and questions to help prepare you for the upcoming lesson.

 

= For Therapists =

It is important for therapists to have a comprehensive knowledge of the nervous system in order to be able to understand the effects of treatments.

Some treatments may have the ability to stimulate nerves, others have the ability to relax. Having knowledge of the nervous system can help therapists to understand the effects of stress on the body.

Although the nervous system may seem a complicated system to study, it is essential to understand it as it is through the nervous system that therapists communicate with their clients.

 

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1. Describe the structure and function of the different type of nervous system

The Nervous System

The nervous system has two main parts which both possess unique structural and functional characteristics:

  • central nervous system (CNS) – this is the main control system that consists of the brain and the spinal cord
  • peripheral nervous system (PNS) – this system can be subdivided into the somatic nervous system and the autonomic nervous system.

What are the components in the Central Nervous System?

Spinal Cord

Structure: the spinal cord extends from the medulla oblongata through the spinal vertebrae ending at the first lumbar vertebra. It consists of white matter on the surface and grey matter inside branching off into 31 pairs of spinal nerves and part of one cranial nerve.

Function: the spinal cord carries motor and sensory nerve fibres along its length, sending messages to and from the body and brain.

  • the cranial nerves
  • the parasympathetic nervous systems
  • the brain
  • the spinal nerves
  • the sympathetic nervous systems
  • the spinal cord
You can choose more than one answer

Which part of the brain concerned with all forms of conscious activity?

Brain

The brain is the organ that fills the cranium (skull). It stops developing in the 15th year of life. It is the main mass exercising control over the body and mind and it has three different sections:

  • the cerebrum (also known as cerebral hemispheres)
  • the cerebellum
  • the brain stem.

Cerebrum

This is the largest part of the brain and is divided into two cerebral hemispheres, one on the right and one on the left.

The outer layer is made of folds of grey matter (i.e. cell bodies).

The folds increase the brain’s surface area and thus the number of cell bodies. Inside the grey matter is white matter (i.e. nerve fibres). These fibres connect different parts of the brain together.

Function:

  • controlling voluntary movement (i.e. the movements we choose to make)
  • interpreting and perceiving conscious sensations like pain, heat and cold
  • controlling mental activity, like memory, intelligence and reasoning.

Cerebellum

The cerebellum is a cauliflower-shaped structure located at the posterior of the cranium, below the cerebrum. It is the brain’s second largest region.

Like the cerebrum, it has two hemispheres and has an outer cortex of grey matter and an inner core of white matter. The cerebellum is concerned with muscle tone, the coordination of skeletal muscles and balance.

Function:

  • co-ordinating muscular activity, making sure movements are smooth and precise (damage to the cerebellum results in clumsy, uncoordinated movements).
  • subconsciously controlling and maintaining muscle tone and posture.
  • maintaining balance and equilibrium of body.

Hypothalamus

Helps with the regulation of body temperature, water balance and metabolism. Centre for drives and emotions such as thirst, appetite, sex, pain and pleasure.

It also regulates the pituitary gland thereby forming the main link between the nervous and endocrine systems. 

  • cerebrum
  • hypothalamus
  • medulla oblongata
  • thalamus

Fill in the blank

The part of the brain which helps to regulate body temperature is .

Which part of the brain contains vital control centres for the heart, lungs and intestines?

Brain Stem

The brain stem consists of three parts, the mid brain, ponds varolli and the medulla oblongata.

Mid-brain contains the main nerve pathways connecting the cerebrum and the lower nervous system.

It also contains certain visual and auditory reflexes that coordinate head and eye movements with things seen and heard.

Pons Varolii is below the mid-brain and relays messages from the cerebral cortex to the spinal cord and helps regulate breathing.

Medulla Oblongata is often considered the most vital part of the brain.

It is an enlarged continuation of the spinal cord and connects the brain with the spinal cord. Control centres within the medulla oblongata include those for the heart, lungs and intestines. The medulla also controls gastric secretions and reflexes such as sweating, sneezing, swallowing and vomiting.

  • hypothalamus
  • medulla oblongata
  • pons varolii
  • mid-brain

Which of the following is not one of the cranial nerves?

Peripheral Nervous System (PNS)

The peripheral nervous system concerns all the nervous system outside the central nervous system and contains motor and sensory nerves which transmit information to and from the body and brain.

It consists of:

  • 12 pairs of cranial nerves and
  • 31 pairs of spinal nerves.

Cranial Nerves are divided into 12 pairs and include sensory, motor and mixed nerves.

Trigeminal (5th Cranial nerve)

  • Opthalmic – sensory nerves supplying the lacrimal glands, conjuctiva of the eyes, eye lids, forehead, anterior part of the scalp and mucous membrane of the nose
  • Maxillary – sensory nerves supplying the lower eye lids, upper gums, upper teeth and cheeks
  • Mandibular – sensory and motor nerves. Supplying the teeth and gums of the lower jaw, ear and tongue. Motor supplying the muscles of mastication

Facial (7th Cranial nerve)

Motor supply the muscles of facial expression and sensory supply nerves of taste from the anterior part of the tongue.

Accessory (11th Cranial nerve)

There are two parts, cranial and spinal.

  • Cranial branches joining the vagus nerve to supply the pharynx and larynx
  • Spinal branches supplying the trapezius and sternocleido mastoid

  • cervical
  • facial
  • optic
  • trigeminal

What are the two major divisions of the nervous system?

  • the central nervous system (CNS)
  • the brain
  • the peripheral nervous system
  • the spinal cord
  • the autonomic nervous system
Choose 2 answer

Spinal Nerves

Spinal Nerves 

These nerves begin in the spinal cord and supply all parts of the body not covered by the cranial nerves. They are all mixed nerves.

Spinal nerves are divided into 31 pairs:

  • Cervical: 8 pairs
  • Thoracic: 12 pairs
  • Lumbar: 5 pairs
  • Sacral: 5 pairs
  • Coccygeal: 1 pair

Somatic / Autonomic Nervous System

The Somatic Nervous System conducts impulses from the CNS to the skeletal muscle fibres. This is the voluntary branch of the PNS and allows conscious control over the contraction of skeletal muscles.

The Autonomic Nervous System conducts impulses from the CNS to cardiac and smooth muscles. This is an involuntary system controlled by the hypothalamus. Its nerves arise from the medulla oblongata. The Autonomic Nervous System is further divided into Sympathetic and Parasympathetic divisions. Every organ in the body has a sympathetic and parasympathetic nerve supply with one division generating the opposite effect to the other.

Autonomic Nervous System

Sympathetic

Structure: Consists of nerves that arise from the spinal cord at the thoracic and lumbar region, form ganglia (bundles of nerve fibres) just outside the CNS and then extend to the organ or tissue they supply.

Functions: Prepares body for stressful situations such as excitement or physical activity (fight or flight system). Neurones release acetylcholine and noradrenaline which have the following effects:

  • accelerates action of heart, increasing rate and force of contraction.
  • vasodilation of coronary arteries, increasing blood supply to the heart muscle.
  • vasodilation of vessels supplying skeletal muscles, increasing oxygen and nutrient supply and waste removal.
  • causes sustained contraction of the spleen, thus increasing volume of blood circulating.
  • vasoconstriction of vessels that supply the digestive system and urinary system, increasing blood available for active muscles and brain.
  • dilation of bronchioles, increasing volume of air that can be inspired and expired.

Parasympathetic

Structure: Consists of nerves that arise from the brain and sacral region of the spinal cord, form ganglia near to or inside the organ or tissue they supply.

Functions: Predominant system in non-stressful situations and keeps normal body functions running when the body is at rest. Neurones release acetylcholine.

  • slows action of heart, decreasing rate and force of contraction
  • vasoconstriction of coronary arteries, decreasing blood supply to the heart muscle
  • vasodilation of vessels supplying the digestive system and urinary system with contraction of the bladder and rectal muscles, increasing digestion, nutrient absorption, micturition and defacation.
  • constriction of the bronchi, decreasing the volume of air

Reflex Arc

A reflex is an automatic (i.e. not controlled by the brain) movement produced by a sensory stimulus.

It is instant and involuntary. (e.g. a finger touching boiling hot water will immediately move away)

Several structures are involved in the production of a reflex and together they constitute the ‘reflex arc’:

  • a sense organ, like the skin or the nerve endings in muscles, tendons or organs
  • a sensory nerve travelling from the sensory organ
  • the spinal cord
  • a motor nerve starting in the spinal cord and travelling to the motor organ.

Function: reflexes are mostly protective and designed to stimulate the quickest motor responses (movements) possible.

They are reflexes which are automatic and do not require supervision, like the secretion of gastric juices when food reaches the stomach.

Fight or Flight

2. Describe the structure and function of Neurons

Functions of the Nervous system

The nervous system has three main functions:

  • It senses changes both within the body (the internal environment) and outside the body (the external environment).
  • It analyses the sensory information, stores some aspects and makes decisions as to how to respond. This is called integration.
  • It may respond to stimuli by initiating muscular contractions or glandular secretions.

Three types of Neurons

1. Sensory neurone

Sensory neurons inform the central nervous system of outside stimuli through the senses of touch, sight, hearing, taste and smell. By causing muscles to contract and relax

2. Mixed neurone

Mixed neurone (Interneurons) form the connections that enable communication between the sensory neurons and the motor neurons and also perform many other complex signaling functions within the nervous system.

3. Motor neurone

Motor neurons enable such involuntary muscle functions as the beating of the heart and the passage of food through the intestines, as well as voluntary skeletal muscle function

The junction where nerve impulses are transmitted from one neurone to another is called?

Nerve cell (Neuron)

The functional unit of the nervous system is a neuron which is a specialised nerve cell, designed to receive stimuli and conduct impulses. The nervous system contains billions of interconnecting neurons which are the basic impulse-conducting cells of the nervous system. 

Neurons also occur in groups called ganglia outside the central nervous system and as single cells, known as a ganglion, in the walls of organs.

Neurons have three basic parts:

  • Cell body – this has a central nucleus and is surrounded by cytoplasm and contains standard organelles such as mitochondria and a golgi body.
  • Dendrites – these are highly branched extensions of the nerve cell. These neural extensions receive and transmit stimuli towards the cell body.
  • Axon – this is long, single nerve fibre extending from the cell body. The function of an axon is to transmit impulses away from the cell body.

  • synapse
  • dendrite
  • axon
  • neurotransmitter

Name the parts

  • Axon
  • Axon Terminals
  • Cell Body
  • Dendrites
  • Nucleus

What is the fine, delicate membrane that surrounds the axon is called?

Axon / Myelin sheath

Fatty insulating sheath that covers the axon. Insulate the nerve and accelerate the conduction of nerve impulses along the length of the axon.

Axon membrane

Long, single nerve fibre extending from the cell body.  Transmit impulses away from the cell body.

Node of Ranvier

The myelin sheath has gaps at intervals of 2–3 mm along the length of the axon which are called the nodes of Ranvier. During neural activity impulses jump from one node to another, resulting in an increased rate of conduction.

Neurilemma

A fine delicate membrane that surrounds the axon and consists of a layer of one or more Schwann cells enclosing the myelin sheath. Plays an important role in the regeneration of peripheral nervous system (PNS) nerve fibres.

  • neuroglia
  • nodes of ranvier
  • neurilemma
  • synaptic knob

White matter / Grey matter

The Central Nervous System (CNS) has two kinds of tissue:

  • grey matter and
  • white matter

Grey matter

On the outside of the brain and the inside of the spinal cord. Contains the cell bodies, dendrites and axon terminals of neurons, so it is where all synapses are.

White matter

On the inside of the brain and the outside of the spinal cord. Made of axons connecting different parts of grey matter to each other.

3. Describe diseases and disorders of the nervous system

Bell’s Palsy

Injury or infection of the facial nerve which subsequently becomes inflamed

Effect: Facial paralysis.

Cerebral Palsy

Damage to the brain, caused during birth or resulting from a prenatal defect.

Effect: Affects motor system control.

Motor Neuron Disease

A rare progressive disorder, in which the motor neurones in the body gradually deteriorate

Effect: Weakness and wasting of muscles

Multiple Sclerosis

Also known as disseminated sclerosis.

Loss of the protective myelin sheath from nerve fibres in the central nervous system.

Effect: Causes muscular weakness, loss of muscular coordination, problems with skin sensation, speech and vision.

Myalgic Enchephalomyelitis (ME)

Also known as post-viral fatigue or chronic fatigue syndrome.

Effect: Exhaustion, general aches and pains, headaches and dizziness, inflammation of the brain and spinal cord.

Neuralgia

Various causes

Effect: Bouts of burning or stabbing pain along the course of one or more nerves.

Neuritis

Inflammation of a nerve, caused by infection, injury, poison, etc.

Effect: Pain along the nerve’s length and/or loss of use of the structures supplied by the nerve.

Parkinson’s Disease

Progressive disease caused by damage to basal ganglia of the brain and resulting in loss of dopamine (neuro-transmitter).

Effect: Causes tremor and rigidity in muscles, as well as difficulty and slowness with voluntary movement.

Sciatica

Pressure on the roots of the sciatic nerve often caused by degeneration of an intervertebral disc

Effect: Pain down the back and outside of the thigh, leg and foot

Stress

Stress is any factor that affects mental or physical well-being.

Emotions such as anxiety, fear and other negative feelings can affect the nervous system causing increased heart rate, breathing difficulties, sleep disturbances and stomach problems. All of these physical effects are caused by the nervous system overworking in response to stress.

Revision

What messages is the sensory nerve is responsible for sending?

  • from the brain and spinal cord
  • to the brain and spinal cord
  • to and from the brain and spinal cord
  • from the brain only

The junction where nerve impulses are transmitted from one neurone to another is called?

  • synapse
  • dendrite
  • axon
  • neurotransmitter

The spinal cord is an extension of which part of the brain?

  • brain stem
  • medulla oblongata
  • mid-brain
  • pons

Fill in the blank 1

The part of the brain which is responsible for memory is  .

Which part of the brain concerned with all forms of conscious activity?

  • cerebrum
  • hypothalamus
  • medulla oblongata
  • thalamus

Which of the following is not an effect of the parasympathetic nervous system?

  • increased peristalsis
  • decreased heart rate
  • contraction of the bladder
  • dilation of blood vessels

Which of the following is an effect of the sympathetic nervous system?

  • contraction of the bladder
  • decreased breathing rate
  • increased heart rate
  • pupil constriction

What disease of the central nervous system in which the myelin sheath covering the nerve fibres is loss?

  • cerebral palsy
  • multiple sclerosis
  • bell’s palsy
  • motor neurone disease

Fill in the blank 2

The part of the brain which helps to regulate body temperature is .

Which disease effect gives bouts of burning or stabbing pain along the course of one or more nerves?

  • Neuritis
  • Cerebral Palsy
  • Multiple Sclerosis
  • Neuralgia

What disease cause damage to the brain during birth or resulting from a prenatal defect?

  • Cerebral Palsy
  • Multiple Sclerosis
  • Motor Neuron Disease
  • Sciatica

What disease is often caused by degeneration of intervertebral disc?

  • Stress
  • Motor Neuron Disease
  • Sciatica
  • Parkinson’s Disease

The three basic parts of a neuron are?

  • axon
  • axon terminals
  • dendrites
  • cell body
  • motor neurone
  • nucleus
Choose 3 answers

Fill in the blank 3

Parkinson’s disease is caused by damage to the  of the brain.

What is the fine, delicate membrane that surrounds the axon is called?

  • neuroglia
  • nodes of ranvier
  • neurilemma
  • synaptic knob

What are the components in the Central Nervous System?

  • the cranial nerves
  • the parasympathetic nervous systems
  • the brain
  • the spinal nerves
  • the sympathetic nervous systems
  • the spinal cord
You can choose more than one answer

What is the sensory nerves supplying the lacrimal glands, conjuctiva, cornea of the eyes and eye lids?

  • Optic
  • Vagas
  • Opthalmic
  • Facial

Which region of the brain coordinate the skeletal muscle?

  • mid-brain
  • cerebrum
  • pons varolii
  • cerebellum

Which region of the brain concerned with interpreting and perceiving conscious sensations?

  • medulla oblongata
  • cerebellum
  • hypothalamus
  • cerebrum

Name the parts

  • Axon
  • Axon Terminals
  • Cell Body
  • Dendrites
  • Nucleus