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Flashcards in Nervous System Deck (48):
1

Neurones are arranged so that they make up the CNS consisting of what? name items that make up CNS

Brain Spinal cord Peripheral nervous system Ganglia

2

The Nervous system is formed from specialist cells called what

Neurones

3


Neurones can be either

 sensory (afferent)

or

motor (efferent) in function

4

Sensory neurones take messages from where

Sensory neurones take messages from the environment via the skin, or sense organs like muscles and joints, and transmit them via the spinal cord to the brain

5

Motor neurones transmit impulses from where?

Motor neurones transmit impulses from the brain via the spinal cord to the effector, perhaps a muscle, to initiate movement.

6

There are three main component parts to a neurone:

what are they?

Cell Body

Axon

Dendrites

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There are how many types of neurones, all containing the three major components. However they have different appearances and functions

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8

Association neurones are responsible for what?

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Association neurones are responsible for joining sensory (aferent ) and motor (efferent ) neurones together.

They are found only in the brain and spinal cord and play an important role in reflex processes.

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Unipolar neurones

This type of neurone has only -------  ----------------- process, shared by both ------ and -----------.

They are -------------- in function and are found primarily within the --------- of --------- and  --------- nerves.

Unipolar neurones

This type of neurone has only one cytoplasmic process, shared by both axon and dendrite .

They are sensory (aferent ) in function and are found primarily within the ganglia of cranial and spinal nerves.

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Multipolar neurones

This type of neurone has many cytoplasmic processes, only one of which is an axon, there will be several more as dendrites .

These neurones are ------------------in function and the majority of neurones within the  -------and ---------  are of this type

Multipolar neurones

This type of neurone has many cytoplasmic processes, only one of which is an axon, there will be several more as dendrites .

These neurones are motor in function (efferent ) and the majority of neurones within the brain and spinal cord are of this type

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Bipolar neurones

This type of neurone has ------- ------------ processes, one ----and one ----------

Bipolar neurones are usually ---------------) and are found mainly in the -------- of the -------, the --------------( and the inner-----.

Bipolar neurones

This type of neurone has two cytoplasmic processes, one axon and one dendrite.

Bipolar neurones are usually sensory (afferent ) and are found mainly in the retina of the eye, the olfactory region (nose) and the inner ear.

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What do I need to know about neuroglia?

Neuroglia

Cells of the nervous system that are specialised to perform the functions of connective tissue.  The neuroglia of the central nervous system are the astrocytes, oligodendrocytes, microglia and ependyme; neuroglia of the peripheral nervous system include the neurolemmocytes (Schwann cells) and the ganglion satellite cells.  Also called glial cells.

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Neuroglia has two specific properties

 1 Irritability ability to generate impulses as a result of stimuli from inside or outside the body

2 Conductivity ability to transport the impulses from one part of the body to another

14

Synapses and neurotransmitters
 

Synapses and neurotransmitters
More than one neurone is required to transport an impulse from its origin to its destination, whether it is sensory (afferent) or motor (efferent ). However neurones are not anatomically joined in any way to each other, there is always a minute gap, the synaptic cleft, between them. The synaptic end bulb of each axon terminal is in close proximity to the dendrite receptors or cell bodies of the next neurone in the process, separated only by the synaptic cleft.

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 (afferent) means what?

sensory

16

 (efferent ).means what?

 motor

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Neurilemma

The fibres of the ---------- ----------are covered in a ---------- called neurilemma.

This neurilemma is responsible for the regeneration of fibres that have become injured.

Fibres of the ------- --------- ------------ do not have this layer and so do not have any powers of regeneration.

Neurilemma

The fibres of the peripheral nerves are covered in a membrane called neurilemma.

This neurilemma is responsible for the regeneration of fibres that have become injured.

Fibres of the central nervous system do not have this layer and so do not have any powers of regeneration.

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Myelin sheath

Some neuroglia produce a phospholipid substance called myelin sheath that surrounds the nerve fibres of the system.

Its function is to increase the -------- at which impulses travel along the fibres, whether they are --------- or -------.

The myelin sheath has gaps along its length called "------ of -------" which also help rapid transmission of impulses along the length of the fibre.

Myelin sheath

Some neuroglia produce a phospholipid substance called myelin sheath that surrounds the nerve fibres of the system.

Its function is to increase the speed at which impulses travel along the fibres, whether they are dendrite or axon .

The myelin sheath has gaps along its length called "nodes of Ranvier" which also help rapid transmission of impulses along the length of the fibre.

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Schwann cell

--------- and --------- are both formed from the same cell, the Schwann cell.

This Schwann cell encircles the fibre as it develops and continues to wrap itself around the fibre in a swiss roll effect. The nucleus and the cytoplasm of the cell are forced to the outside of the roll and it is this layer that forms the neurilemma.

The myelin sheath is merely many layers of Schwann cell membrane.

Schwann cell

Myelin sheath and neurilemma are both formed from the same cell, the Schwann cell.

This Schwann cell encircles the fibre as it develops and continues to wrap itself around the fibre in a swiss roll effect. The nucleus and the cytoplasm of the cell are forced to the outside of the roll and it is this layer that forms the neurilemma.

The myelin sheath is merely many layers of Schwann cell membrane.

20

The central nervous system is made up of the ----- and ----- ----, both of which are completely covered by three protective layers of tissue called the --------- . These are the ------ -------, the ------- -------- and the ----- ------

The central nervous system is made up of the brain and spinal cord, both of which are completely covered by three protective layers of tissue called the meninges . These are the dura mater, the arachnoid mater and the pia mater

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4 parts of the brain

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Cerebrum

The cerebrum is divided into ------  -------------- by the longitudinal fissure but is joined together by the -------- -------, a bunch of fibres formed of white matter. Each hemisphere is then divided into four lobes that correspond in name and position to the bones of the skull:

name the 4 brain lobes

Cerebrum

The cerebrum is divided into two hemispheres by the longitudinal fissure but is joined together by the corpus collosum, a bunch of fibres formed of white matter. Each hemisphere is then divided into four lobes that correspond in name and position to the bones of the skull:

Frontal lobe

Parietal lobe

Temporal lobe

Occipital lobe

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The cerebral surface is called the cortex and is formed of grey matter. It has many random convolutions (troughs and peaks) that increase the surface area. These convolutions are called gyri and sulci, where gyri are the peaks and sulci are the troughs. The white matter lies under this cortex and is formed in tracts. what are three types of tract within the cerebrum:

 

  1. Association tracts - transmit information from gyri to gyri
  2. Commissural tracts - communicate between opposite lobes or hemispheres
  3. Projection tracts - communicate between brain and spinal cord

24

There are three masses of grey matter within the white matter of the cerebrum. These masses are:

 

There are three masses of grey matter within the white matter of the cerebrum. These masses are:

Basal ganglia

Thalamus

Hypothalamus

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The parietal and frontal lobes are separated by the central sulcus, also known as the rolando fissure. There are motor centres to the front of this sulcus and sensory centres to the rear. The centres relating to inferior extremity function (ie feet and legs), are towards the superior aspect of the sulcus and the centres relating to superior extremities (ie arms and head), are towards the inferior aspect of the sulcus.

what are the functions of Cerebrum

  1. Functions
  2. Processing of sight, touch, smell and hearing
  3. Processing sensory impulses from the skin, muscles, bones and joints
  4. Control of voluntary skeletal muscle
  5. Intelligence
  6. Memory
  7. Ability to learn
  8. Reasoning
  9. Moral thought
  10. Extra sensory perception

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Cerebellum

The cerebellum is the second largest component of the brain. It lies inferior to the cerebrum  and posterior to the brain stem and is separated from the cerebrum by the transverse fissure . The cerebellum looks rather like a butterfly, the wings are called hemispheres and they are divided by the vermis.

The surface is called the cortex and consists of grey matter. It has convolutions (peaks and troughs) similar to those of the cerebral cortex - the gyri (peaks) and sulci (troughs). However cerebellar convolutions are more ridge-like and lie parallel to each other. The ridges are called folia and tend not to be as deep as gyri and sulci. The white matter lies deeply to the cortex and forms a tree-like structure.

There are masses of grey matter within the white matter called cerebellar nuclei. These nuclei are responsible for passing messages in and out of the cerebellum, to and from different parts of the brain. what are the functions cerebella?

  1. Coordination of subconscious movement
  2. Maintenance of balance and posture
  3. Muscle tone
  4. Sleek movements
  5. Sensations of anger and pleasure

27

Diencephalon

Thalamus
The thalamus consists of two masses of grey matter deep within the cerebrum . They are oval in shape and are approximately 3cm in length. They serve as a relay station for all sensory impulses entering the brain except those associated with the sense of smell. The thalamus is also the centre that interprets temperature, pain, light and touch. It is also thought that the thalamus has some connection with emotions and memory

Hypothalamus
The hypothalamus consists of two groups of grey matter within the cerebrum that lie inferior to the thalamus. It is connected to the pituitary gland and controls the output of hormones . The hypothalamus has several major functions: what are the functions

 

 

 

 

  1. Regulates hunger and food intake
  2. Regulates thirst and bodily water intake 
  3. Regulates body temperature
  4. Control of the autonomic nervous system
  5. Sensory area for sound, taste and smell
  6. Associated with rage and aggression
  7. Mind over body phenomenon

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Brain stem

Midbrain (mesencephalon)
The midbrain lies at the inferior aspect of the cerebrum and the superior aspect of the pons varolii. It acts as a relay station between the different component parts of the brain and houses the origin of two cranial nerves.

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Pons varolii
The pons varolii lies inferior to the midbrain and superior to the medulla oblongata. It basically acts as a bridge connecting all the parts of the brain together. It is the origin of four cranial nerves and its functions are:

 

  1. Pneumotaxic area - inhibits respiration and inspiratory volume
  2. Apneustic area - stimulates and prolongs inspiration, inhibits expiration

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Medulla oblongata
The medulla oblongata is situated inferior to the pons varolii and superior as a continuation of the spinal cord. It lies just inside the cranial vault, above the foramen magnum . It is approximately 2.5cm long and is shaped like a pyramid with its base uppermost. The outer surface is formed of white matter, the central part of grey matter. The white matter forms upwards and downwards tracts that pass messages between the rest of the brain and spinal cord. It is the origin of five cranial nerves and its function are:

Decussation of pyramids - crossing over of nerve fibres. This explains why the left side of the brain controls the right side of the body and vice versa.

 

  1. Reticular formation - responsible for arousal from sleep and consciousness.
  2. Cardiac centre - regulates force of contraction and heart rate.
  3. Rhythmicity centre - regulates respiratory rhythm.
  4. Vasomotor centre - regulates diameter of blood vessels around the body.

Other vital centres include:

  1. Swallowing
  2. Coughing
  3. Vomiting
  4. Sneezing
  5. Hiccuping

31

Dura mater what is it?

Dura mater

This is the tough fibrous outermost layer.

It lines the bones of the cranium and the canal formed by the vertebrae. It also lines the space between the two cerebral hemispheres. A fold of dura mater separates the cerebral hemispheres from the cerebellum.

The main veins inside the cranium lie in the dura mater.

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Arachnoid mater what is?

Arachnoid mater

This is a delicate membrane separated from the dura mater by the subdural space in which there is a thin film of serous fluid.

It encloses the subarachnoid space, which is criss-crossed by a fine network of connective tissue and which contains cerebrospinal fluid (CSF) and the larger blood vessels of the brain.

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Pia mater what is it

Pia mater

This is a very delicate inner membrane that closely covers the brain and spinal cord and supports a network of fine blood vessels, including those of the choroid plexuses  that roof the ventricles.

The pia mater follows every convolution of the surface of the nervous tissue and sheaths the roots of the cranial and spinal nerves.

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What is the peripheral nervous system?

The peripheral nervous system begins with a series of hollow spaces that exist within the brain - the ventricles

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The ventricles are lined with ciliated epithelium and the constant movement of the cilia keep the fluid in motion - the cerebrospinal fluid (CSF). This is produced by outgrowths of highly vascular tissue called choroid plexuses. In healthy people CSF is a clear liquid similar to tissue fluid but with different concentrations of the dissolved substances. For example there is far less protein and more sodium chloride

The ventricles are lined with ciliated epithelium and the constant movement of the cilia keep the fluid in motion - the cerebrospinal fluid (CSF). This is produced by outgrowths of highly vascular tissue called choroid plexuses. In healthy people CSF is a clear liquid similar to tissue fluid but with different concentrations of the dissolved substances. For example there is far less protein and more sodium chloride

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The functions of the CSF are to:

 

The functions of the CSF are to:

  1. support the delicate nervous tissue
  2. protect nervous tissue against trauma, eg changes in pressure
  3. maintain a uniform pressure around nervous tissue
  4. supply nervous tissue with food by direct bathing of the cells, where no blood vessels penetrate

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CSF fills the cavities of the brain and spinal cord and passes through the openings in the fourth ventricle to fill the subarachnoid spaces. Little fluid enters the spinal region, where constancy of composition is maintained by diffusion and posture changes. However there is a small flow into the cranial region where the fluid re-enters the blood through the arachnoid villi.

In addition to the ordinary motor (efferent ) nerve fibres, many of the cranial and spinal nerves contain autonomic fibres that control the involuntary muscles and glands of the body. This autonomic system is seen as two parts:

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What types of head injuries exist?

name 6

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Concussion

As the brain is able to move slightly within the skull, a sudden blow to the head will result in the brain being shaken causing either brief or partial loss of consciousness.

Signs and symptoms are:

 

Concussion

Signs and symptoms are:

  1. Amnesia of the event (before and during)
  2. Headache
  3. Nausea
  4. Dizziness
  5. Disorientation

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Compression

This is a serious condition requiring urgent medical attention. There are many causes including a cerebrovascular accident (stroke), fractured skull, tumour or infection.

The end result however will be bleeding or swelling within the brain, causing a build up of pressure within the skull (intracranial pressure). This rising pressure will cause abnormal brain function.

Signs and symptoms include:

 

Compression

This is a serious condition requiring urgent medical attention. There are many causes including a cerebrovascular accident (stroke), fractured skull, tumour or infection.

The end result however will be bleeding or swelling within the brain, causing a build up of pressure within the skull (intracranial pressure). This rising pressure will cause abnormal brain function.

Signs and symptoms include:

  1. Impaired or deteriorating level of consciousness
  2. Severe headache
  3. Slow full pulse
  4. Raised blood pressure
  5. Flushed complexion
  6. Unequal pupils
  7. History of head injury

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Contra coup

This type of head injury is caused by indirect trauma to the brain.

The force incurred sustaining an external skull injury is transferred through the brain causing trauma to the opposite side to the external wound.

The signs and symptoms may be any combination of those found in concussion or compression

Contra coup

This type of head injury is caused by indirect trauma to the brain.

The force incurred sustaining an external skull injury is transferred through the brain causing trauma to the opposite side to the external wound.

The signs and symptoms may be any combination of those found in concussion or compression:

  1. Amnesia of the event (before and during)
  2. Headache
  3. Nausea
  4. Dizziness
  5. Disorientation
  6. Impaired or deteriorating level of consciousness
  7. Slow full pulse
  8. Raised blood pressure
  9. Flushed complexion
  10. Unequal pupils
  11. History of head injury

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Haemorrhage

The haemorrhage that accompanies a head injury can occur in one of two ways depending on which side of the dura mater the haemorrhage takes place.

Haemorrhage resulting from a rupture or damage to an artery, usually the meningeal artery - which lies between the cranial bones and the dura mater - is termed an extra-dural haemorrhage. Initially bleeding will be quite profuse but will slow once clotting begins.

Haemorrhage below the dura mater is termed sub-dural and often involves a venous sinus, the associated haemorrhage is not so fierce, but tends to "flood" the brain tissue and is more widespread.

Haemorrhage

The haemorrhage that accompanies a head injury can occur in one of two ways depending on which side of the dura mater the haemorrhage takes place.

Haemorrhage resulting from a rupture or damage to an artery, usually the meningeal artery - which lies between the cranial bones and the dura mater - is termed an extra-dural haemorrhage. Initially bleeding will be quite profuse but will slow once clotting begins.

Haemorrhage below the dura mater is termed sub-dural and often involves a venous sinus, the associated haemorrhage is not so fierce, but tends to "flood" the brain tissue and is more widespread.

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Lucid interval

As a result of a blow to the head, someone may be initially unconscious but after a period of time regain consciousness.

Further on down the line, maybe minutes and hours later, the casualty will return to unconsciousness.

This period of regained consciousness is called a lucid interval and as a rule the shorter this period is the more serious the injury.

 

Lucid interval

As a result of a blow to the head, someone may be initially unconscious but after a period of time regain consciousness.

Further on down the line, maybe minutes and hours later, the casualty will return to unconsciousness.

This period of regained consciousness is called a lucid interval and as a rule the shorter this period is the more serious the injury.

 

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Shock

As a rule shock does not accompany a head injury. If a patient shows the signs and symptoms of shock then they usually have some other injury as well, like a wound.

When a head injury is associated with a wound, the wound will usually bleed profusely. Scalp wounds are traumatic to look at but are seldom life-threatening. Any wound should be treated in the normal way but a special effort must be made not to cover the eyes, as this will only add to the patient's discomfort and bewilderment

Shock

As a rule shock does not accompany a head injury. If a patient shows the signs and symptoms of shock then they usually have some other injury as well, like a wound.

When a head injury is associated with a wound, the wound will usually bleed profusely. Scalp wounds are traumatic to look at but are seldom life-threatening. Any wound should be treated in the normal way but a special effort must be made not to cover the eyes, as this will only add to the patient's discomfort and bewilderment

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Epilepsy is a very common illness that usually manifests itself in the form of fits. These fits can be very distressing to watch but are not usually life-threatening. Epilepsy can be caused in several different ways

name 3

  1. Genetic abnormality
  2. Brain injury
  3. Injury at birth

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Most patients who suffer from epilepsy have their condition controlled by medication and it is not uncommon for the cause of the epilepsy to remain a mystery. Epilepsy falls into three categories

what are they

Petit mal

The patient will not actually suffer a fit as such, but will experience a period of vagueness and may stare vacantly into space for a few seconds and then return to normal.

Grand mal

The process of grand mal is described in stages:

Stage I
The patient experiences an aura, or an inner feeling that something is going to happen. This aura is followed by sudden unconsciousness, the collapse is sometimes accompanied by a cry.

Stage II
This is the tonic stage where the patient's body goes completely rigid for a few seconds.

Stage III
This is the convulsive stage where the patient's whole body shakes violently. It is also possible for the chest muscles to go into spasmodic contraction that will embarrass the patient's breathing. Loss of bowel and bladder control coupled with biting of the tongue is also common.

Stage IV
This is the recovery stage when the patient gradually regains consciousness. Their pulse and respirations will be quite rapid at first and they will be extremely disorientated.

Status epilepticus

Status epilepticus is a development of grand mal in that the patient does not progress to stage IV, but instead experiences a continuous cycle of stage II and III.

This condition is extremely dangerous and requires immediate and urgent medical treatment, which will involve drug therapy

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There are two main types of mental illness:

Neuroses
Eg anxiety, depression, obsessions and phobias.

People who suffer from neuroses usually know that they have the problem and continue to live relatively normal lives

Psychoses
Eg schizophrenia and manic depression.

Patients who suffer from psychotic disorders often have their lives totally disrupted by their illness.

It is not unusual for the patient to lose complete contact with reality, resulting in abnormal behaviour that can be extremely distressing for the patient's relatives.

The patient will often experience both audible and visual hallucinations and appear to be living in a world of their own.

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cerebrum

cerebellum

thalamus

hypothalamus

midbrain

pons varolii

medulla oblongata

spinal cord

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