Disability

Question 1

Cranial Contents

Answer 1

1. Brain (80%)
2. CSF (10%)
3. Blood (10%)

Question 2

Cerebrospinal Fluid

Answer 2

Clear fluid produced in choroid plexus and absorbed by arachnoid villi. Circulates through subarachnoid space (approx. 80-150ml) and bathes spinal cord and brain to provide protection (shock absorption/buoyancy), deliver nutrients (glucose, proteins, lipids, and electrolytes) and remove waste products.

Question 3

Meninges
Definition
Layers

Answer 3

Three membrane layers covering the brain and spinal cord providing protection for cranial contents and support for blood vessels and lymphatics.
* Brain parenchyma
1. Pia mater
2. Arachnoid mater
* Subdural space (potential space)
3. Dura mater
* Epidural space
* Skull

Question 4

Pia Mater

Answer 4

The thin/delicate innermost layer; tightly adhered to brain and spinal cord; contains CSF and maintains stiffness of spinal cord.

Question 5

Arachnoid Mater

Answer 5

The thin/spiderweb-like middle layer; connective tissue projects adhere to pia mater.

Question 6

Dura Mater

Answer 6

The thick/tough outer layer; composed of two connective tissue layers adhering to skull and arachnoid mater; contains drainage system to allow entry of blood and exit of CSF.

Question 7

Brain

Answer 7

Composed of approx. 100billion neurons. Relies on constant supply of glucose and oxygen (approx 20% total O2 usage).

Question 8

Cerebral Autoregulation

Answer 8

The ability of the cerebral vasculature to maintain stable blood flow despite changes in cerebral perfusion pressure (corresponding to altered MAP).
Elevated MAP > vasoconstriction to limit blood flow.
Decreased MAP > vasodilation to increase blood flow.

Question 9

Intracranial Pressure
Definition
Normal range

Answer 9

The pressure exerted within the skull and meninges by the intracranial contents.
ICP = 0-10mmHg
Abnormal = >15mmHg

Question 10

Monro-Kellie Hypothesis

Answer 10

The sum of intracranial volumes of blood, CSF and brain is constant. Therefore, an increase in the volume of any of these contents must be offset by a decrease in one/more of the others.

Question 11

Cerebral Perfusion Pressure
Definition
Formula
Normal Range

Answer 11

The blood pressure gradient across the brain generated by cerebral blood flow (an indication of cerebral perfusion).
CPP = MAP - ICP
(Therefore increased ICP = decreased CPP)
CPP < 60mmHg = neuronal hypoxia.

Question 12

Primary Brain Injury
Definition
Types

Answer 12

Sudden and profound injury to the brain that is considered complete at the time of impact.
1. Concussion
2. Contusion
3. Laceration
4. Diffuse Axonal Injury

Question 13

Secondary Brain Injury
Definition
Types

Answer 13

The adverse changes within the brain (cells, chemicals, tissues or vessels) that evolve over a period of hours/days following a primary brain injury and contribute to further tissue destruction.
1. Cerebral Oedema
2. Hematoma
3. Raised ICP
4. Ischaemic/Hypoxic injury

Question 14

Neurological Level of Injury

Answer 14

The lowest part of the spinal cord that remains undamaged which determines which functions remain intact.

Question 15

Central Nervous System

Answer 15

Composed of the brain and spinal cord.

Question 16

Peripheral Nervous System
Definition
Systems

Answer 16

Composed of nerves that branch from the brain and spinal cord.

Somatic - somatic afferent/efferent system - transmits sensory input to brain and voluntary motor impulses to skeletal muscles.

Autonomic - visceral efferent system - transmits involuntary motor impulses to visceral organs.
* Sympathetic - fight or flight responses - e.g. cardiac muscle, endocrine glands, bronchial muscle.
* Parasympathetic - rest and digest responses - e.g. GIT smooth muscle.

Question 17

Nerves
Definition
Types

Answer 17

Bundles of nerve fibres (axons and dendrites) surrounded by connective tissue sheath.
Sensory - afferent fibres (dendrites of sensory neurons).
Motor - efferent fibres (axons of motor neurons).

Question 18

MET Criteria

Answer 18

Sudden drop in GCS >2 points.
Seizure activity.
Suspected stroke.