Nervous System and Conditions

What are the three main functions of the Nervous system?

• Sensory Function (perception)

• Information Transfer and Processing

• Motor function

Describe how the nervous system is seperated

Split into the Central (CNS) and Peripheral (PNS).

• CNS includes brain and spinal cord. Receives information from nerves, analyses and processes this information and responds by sending impulses via nerves across the body to have an effect

• PNS is network of peripheral nerves originating from brain or spinal cord.

The PNS is then separated into the Sensory (afferent) and Motor (efferent) division.

• Sensory (afferent) division transmits impulses from the body to the CNS. It is composed of sensory receptors in the skin. Their nerve impulses are conveyed by somatic sensory fibres, as well as internally all around the body.

• Motor (efferent) division transmits impulses from CNS to the body.

The Motor (efferent) division is again split into the Somatic and Autonomic divisions.

• Autonomic (controls self regulation action of internal organs and glands)

• Somatic (controls voluntary movement of skeletal muscles).

The Autonomic System is ALSO split into the Sympathetic (fight or flight) and Parasympathetic (rest and digest). Also the enteric division (neurons in GI tract, pancreas and gall bladder enable monitoring and modification of motility and secretions of the gut a controls diameter of blood vessels there).

What is a Neuron and what does it consist of?

The cells in the nervous system that generate electrochemical impulses enabling nervous system to function.

Consists of:

• One Cell Body (where nucleus and other cellular organelles found)

• Many Dendrites (receiving or input portions)

• One Axon (thin, long portion transmits electrical signals from cell body to axon terminals. Neurons communicate with each other via chemicals called neurotransmitters, which are released from the synaptic end bulbs at the end of the axon.

What are Myelin Sheaths and Nodes of Ranvier?

Some axons are covered in myelin sheaths which can conduct electrical impulses much faster than those that do not, and also helps to protect the nerve cells.

Myelin sheaths are formed by concentric Schwann cells. Nodes of Ranvier sit in between segments of Myelin Sheath to assist in the rapid transmission of nerve impulses.

What are Neuroglia?

The supporting, non impulse generating cels in the nervous system:

• Provide structural support for neurons

• Create blood brain barrier

• Restrict movement of substances between blood and tissue fluids within the CNS

What is the cranial vault occupied by and what are the four major sections the brain is divided into?

Cranial vault occupied by

• Brain 80%

• Cerebral blood 12%

• Cerebral Spinal Fluid 8%

Four major sections of the brain

• Brain stem (Midbrain, Pons, Medulla oblongata)

• Cerebellum

• Diencephalon (Consists of Thalamus and Hypothalamus)

• Cerebrum

Describe the structure of the Brain Stem and what each component of the brain stem is responsible for

Consists of, moving from top to bottom:

• Midbrain:

  • Relays motor output from cerebral cortex and sensory input from spinal cord to thalamus

  • Controls and coordinates movement

  • Contains origin of two cranial nerves

• Pons:

  • Relays nervous impulses from one side of cerebellum to other and between medulla and midbrain

  • Contains origins of a number of cranial nerves

  • Contains centres to regulate breathing

• Medulla Oblongata

  • Relays sensory and motor input between other parts of brain and spinal cord

  • Together with pons and midbrain, controls level of consciousness

  • Contains centres to manage HR, BP and Breathing

Describe the structure and function of the Cerebellum

• Hemispheric, located posterior to brain stem and inferior to cerebrum

• Responsible for coordinating complex and skilled movements

• Regulates posture and balance

Describe the structure and function of the Diencephalon

• Located deep within brain under cerebrum

• Connects cerebrum with brain stem

• Link between nervous system and endocrine system

• Comprised of thalamus and hypothalamus

What is the function of the Thalamus

• relays sensory input to the cerebral cortex

• Provides perception of touch, pressure, pain and temperature

Describe the structure and function of the Cerebrum

• Hemispheric, largest part of the brain

  • Outer rim of grey matter (contains the cerebral cortex which contains billions of neurons) and internal region of white matter

• Split into four lobes

  • Frontal

  • Parietal

  • Temporal

  • Occipital

• Allows you to read, write, speak

• Various regions responsible for a range of other functions, including sensory perception, motor control, personality, memory and intelligence

Describe the structure and function of the Cerebrum

• Hemispheric, largest part of the brain

  • Outer rim of grey matter (contains the cerebral cortex which contains billions of neurons) and internal region of white matter

• Split into four lobes

  • Frontal

  • Parietal

  • Temporal

  • Occipital

• Allows you to read, write, speak

• Various regions responsible for a range of other functions, including sensory perception, motor control, personality, memory and intelligence

What is CSF?

Cerebrospinal Fluid

• Clear, colourless fluid

• Protects brain and spinal cords from physical and chemical damage

• Carries O2, glucose and other nutrients essential for normal brain function

• Removes waste products

What is CSF?

Cerebrospinal Fluid

• Clear, colourless fluid

• Protects brain and spinal cords from physical and chemical damage

• Carries O2, glucose and other nutrients essential for normal brain function

• Removes waste products

Describe the spinal cord and spinal nerves

Spinal Cord:

• Consists of a vertebral column consisting of 33 vertebrae, providing physical protection for spinal cord

• The cord itself is cylindrical in shape, with a average diameter of 12mm

• Extends from medulla oblongata to superior border of 2nd lumbar vertebrae, where it tapers to form a cone like shape called the conus medullaris. The nerves extending distal from the conus medullaris form the cauda equine (horses tail)

• Contains both afferent and efferent fibres

Spinal nerves

• 31 pairs of spinal nerves branch out from the spinal cord

Describe the spinal cord and spinal nerves

Spinal Cord:

• Consists of a vertebral column consisting of 33 vertebrae, providing physical protection for spinal cord

• The cord itself is cylindrical in shape, with a average diameter of 12mm

• Extends from medulla oblongata to superior border of 2nd lumbar vertebrae, where it tapers to form a cone like shape called the conus medullaris. The nerves extending distal from the conus medullaris form the cauda equine (horses tail)

• Contains both afferent and efferent fibres

Spinal nerves

• 31 pairs of spinal nerves branch out from the spinal cord

What does the Sympathetic Nervous System do?

‘Fight or flight” prepares body to respond to stress and facilitate sudden strenuous exerciser and increased vigilance

• Stimulates cardiac activity

• Opens the airways

• Dilates skeletal blood vessels

• Reduces gastric activity

What does the Parasympathetic Nervous System do?

‘Rest and digest”

• General ‘peacemaker’ effect

• Stimulates digestion and obstruction of food

• Slows down cardiac and respiratory activities

Describe Dementia

• Disease that affects memory, thinking and daily life

• 1/14 over age of 65 have it

• Risk groups are age, genetics, lifestyle

• Controlled by medication but no known cure

• Includes Alzheimer’s

Describe Parkinson’s Disease

• Causes parts of brain to become damaged over many years

• 1/500 in UK

• Men slightly more at risk of developing, though unclear what causes condition to occur

• Treated with medication and physiotherapy

Describe Multiple Sclerosis (MS)

• Affects brain and spinal cord, stopping nerve impulses from travelling correctly

• Over 130000 in UK

• Affects mainly woman and common disability in younger adults

• Managed by medication but no cure

Describe Ataxia

• Group of disorders affecting balance, coordination, speech

• Mainly hereditary but can develop later in life

• No cure, responds well to physiotherapy and medication

Describe paralysis

• Defined as partial or complete loss of muscles function

• Other terms include

  • -plegia (paralysis)

  • -paresis (muscle weakness or incomplete loss of muscle function)

• Terms used to identify areas affected

  • Monoplegia - one limb

  • Hemiplegia - one side of body

  • Quadriplegia/tetrapelgia - all 4 limbs

  • Paraplegia - both lower limbs

What is a CVE and describe the different types and how they are differentiated

Cerebrovascular Event (CVE)

• Stroke or TIA

• Risk factors include Age, Sex, Ethnicity, Family Hx, Smoking, AF, Diabetes, Obesity, previous CVE or MI, Cholesterol, Diet, Hypertension

• Stroke

  • Blood supply to brain interrupted

  • Signs and symptoms develop rapidly, last at least 24 hours

  • Bleed or blockage

• TIA

  • Signs and symptoms of stroke but resolves within 24hrs

  • Anyone with continuing neurological signs during management - treat as stroke

• Signs and symptoms

  • Numbness

  • Weakness or paralysis

  • Slurred speech

  • Blurred vision

  • Confusion/inability to communicate

  • Severe headaches

• Management

  • FAST

  • If major ABC - nearest ED

  • If not but FAST+ HASU (If >10

Describe types of convulsions, fitting disorders and how they are managed

Convulsions are involuntary contractions and retractions of the muscles.

Generalised convulsion

• Affect large part of cerebral cortex

• Bilateral Tonic-Clonic seizures (BTCS)

  • Tonic phase - body wide rigidity, falls, crying out, tongue biting, jaw clenching

  • Clonic phase - regular jerking movements which eventually slow and stop - sometimes accompanied by incontinence

  • Prolonged period of confusion, disorientation, sleepiness or unconsciousness after convulsion called Post-Ictal phase

Absent convulsion

• Staring/daydreaming/absent period

• May be accompanied by repetitive motions

• Last a few seconds with immediate recovery

Partial convulsion

• Affects localised part of cerebral cortex, though may progress into generalised tonic clonic

• Patient may be conscious or altered level of consciousness

• May be changes in behaviour or mood

• May be localised tonic clonic activity

Epilepsy

• Uncontrolled firing of neurons in brain

• Some well managed by medication, other struggle to manage

• Can significantly limit cognitive development in children

• Generally tonic clonic

• Can progress to Status Epilepticus

  • Continuous convulsion lasting over 5mins

  • Series of convulsions (3 or more in an hour) close together with no recovery period in between

Non-epileptic seizures

• FND (Functional Neurological Disorder) and PNES (Psychogenic non-epileptic seizures)

  • Usually last a lot longer

  • Usually triggered by psychological trauma

  • No tonic clonic period

  • Generally does not affect breathing or circulation

• Other causes for non epileptic seizures

  • Hypoglycaemia

  • Kidney failure

  • Tumour

  • Infection

  • Alcohol

  • Eclampsia

  • Stroke

Management using the Primary Survey

R - if actively consulting, put on high-flow O2 and call for paramedic backup. If reduced LOC protect from injury and recovery position

A - Jaw may be clenched (trismus), may have bitten tongue, may be impossible to assess. Do NOT use OP if actively convulsing. Attempt NP if possible.

B - administer high flow, consider Capnogrophy if ventilating

C - oximetry may be difficult but can assess skin colour, tone, cap refill

D - reassess AVPU, any improvement? Convulsion caused by head injury? Check BM now! Could be Hypoglycaemia

E - look for medic alert bracelet, signs of underlying injection, obvious injury, protect pat from injury and protect dignity

Time critical if:

• Major ABCD problem

• Serious head injury

• Status EP

• Underlying infection

Remember when attending seizures

• First, worst or longest should attend hospital

Describe meningococcal disease, symptoms of meningitis and septicaemia, and management

Bacterial infection of meninges caused by meningococcus bacteria. Presents as Meningitis, Septicaemia or combination of both. Can be fatal.

Meningitis symptoms:

• Fever, vomiting, severe headache, rash (particularly non blanching rash), stiff neck, photophobia, sleepy/vacant, confusion/delirium, seizures

Septicaemia symptoms:

• Fever/vomiting, limb/joint pain, cold and shivering, DIB, rash, sleepy/vacant, confusion/delirium

Management

• Standard primary survey approach, look particularly for rash in E (however absence of rash does not exclude meningitis)

Time critical if

• any major ABCD problem

• Non-blanching rash

• Any suspicion of meningitis/septicaemia

Describe coma and management

Coma is described as absence or loss of consciousness

• GCS of 8 or below

• May not always find cause, management is supportive

• Causes

  • Stroke, convulsion, inadequate airway, inadequate breathing, hyper/hypoglycaemia, OD, meningitis, arrhythmias, carbon monoxide etc

Time critical if any major ABCD problem

Management

• comprehensive obs, GCS, pupils

• Thorough secondary survey

• 12 lead

• Reassess

• Scene for clues, med alerts, needle marks, consider trauma