Nervous System

Question 1

What parts can the nervous system be divided into based on gross anatomy?

Answer 1

1. Central nervous system - brain & spinal cord
2. Peripheral nervous systen - 12 pairs of cranial nerves (arise directly from the brain), 31 pairs of spinal nerves (which arise from the spinal cord)

Question 2

What parts can the nervous system be divided into functionally?

Answer 2

1. Somatic nervous system - control of voluntary activities. ‘Motor’- control of skeletal muscles, ‘sensations’ which reach consciousness
2. Autonomic nervous system - control of involuntary activities. ‘Motor’ - to glands, blood vessels, heart etc., ‘sensory’ - blood pressure, CO2 in blood, how full is the duodenum etc.
   Autonomic nervous system is further divided into the 2 opposing systems: sympathetic (fight/flight) and parasympathetic (rest/digest)

Question 3

What 3 components is the brain divide into?

Answer 3

Cerebrum - cerebral hemispheres
Cerebellum
Brainstem - midbrain, pons, meddulla

Question 4

What are the cerebral hemispheres divided into?

Answer 4

Surface - frontal, parietal, temporal and occipital lobes

Deeper - basal ganglia, thalamus, internal capsule etc.

Question 5

what are sulci and gyri?

Answer 5

gyri - folds of cerebrum

sulci - valleys separating gyri

Question 6

what is the difference between white and grey matter?

Answer 6

white - myelinated neurones, found on the inside, where information is transmitted from one place to another
grey - unmyelinated neurones, found on the surface, where processing takes place

Question 7

what are the roles of the brain stem?

Answer 7

transmits signals from the brain to the body (motor) and from the body to the brain (sensory).
Predominantly white matter.

Question 8

What is the role of the cerebellum?

Answer 8

uses sensory information from the body to refine the motor instruction which the brain sends to the muscles - this produces coordinated movement

Question 9

where is the central sulcus found? what is its role?

Answer 9

running across the part of the brain that lies under the parietal bone is the central sulcus, in front of which is the corresponding sensory gyrus. Role is control of muscles of the opposite side of the body; the motor cortex

Question 10

Where are the meninges found? brief function & names of layers

Answer 10

The meninges are 3 protective layers lying between the skull and the brain itself. They have 3 main functions:
to protect the brain
to provide a framework for the blood supply
to enclose the fluid filled subarachnoid space
Layers are (in order closest - furthest from skull):
1. the dura
2. the arachnoid
3. the pia

Question 11

Describe the ‘spaces’ between the meningeal layers

Answer 11

1. Outside the dura - the extradural/epidural space (does not exist in the absence of pathology)
2. The subdural space - between the dura and the arachnoid, does not exist in the absence of pathology
3. The subarachnoid space - between the arachnoid and the pia mater - exists in healthy individuals and is filled with cerebrospinal fluid (CSF)

Question 12

what is the role of CSF? How is it produced?

Answer 12

clear fluid providing nutrients to the brain and maintaining the balance of extracellular fluid.
Protects the brain by providing a cushion against trauma & prevents the delicate nervous and vascular structures from becoming compressed against the internal surface of the skull. Produced by a tissue called choroid plexus found within the ventricles of the brain.

Question 13

Describe the ventricular system of the brain

Answer 13

The brain can be divided into 4 interconnected ventricles:
The right and left lateral ventricles - lie within the cerebral hemispheres, one on either side.
The third ventricle - in the midbrain.
The fourth ventricle - lies between the pons and medulla and in from of the cerebellum.
Cerebrospinal fluid flows from the lateral ventricles –> 3rd ventricle –> cerebral aqueduct –> fourth ventricle –> subarachnoid space, where it is absorbed into the venous sinuses and venous system

Question 14

Describe the blood supply to the brain

Answer 14

2 internal carotid arteries and 2 vertebral arteries supply the brain. At the base of the brain these arteries form a ring of blood vessels called the Circle of Willis.
The Circle of Willis has 6 major branches, 3 on each side, including the anterior, middle and posterior arteries, each of which supplies a particular part of the cerebral hemispheres.

Question 15

A clot in which vessel will cause a stroke?

Answer 15

the middle cerebral artery supplies most of the motor and sensory cortex and a blood clot in this vessel will cause that part of the brain to infarct, causing a stroke.

Question 16

Describe the cranial nerves.

Answer 16

Nerves that arise directly from the substance of the brain. 12 pairs - some sensory, some motor, some mixed and some with autonomic function.

Question 17

What is the function of the following cranial nerves (motor&/sensory, autonomic?):
1 Olfactory
2 Optic
3 Oculomotor

Answer 17

1 sensory (smell)
2 sensory (sight)
3 motor, movement of the eye. Autonomic to pupil and lens.

Question 18

What is the function of the following cranial nerves (motor&/sensory, autonomic?):
4 Trochlear
5 Trigeminal
6 Abducens

Answer 18

4 motor, movement of the eye
5 sensory from the face, nose and oral cavity.
motor - chewing muscles.
6 motor, lateral (outward) movement of the eye

Question 19

What is the function of the following cranial nerves (motor&/sensory, autonomic?):
7 facial
8 vestibulocochlear
9 glossopharyngeal

Answer 19

7 motor of facial expression
  sensory - taste
  autonomic to salivary glands
8 sensory (balance and hearing)
9 sensory from the tongue and pharynx
  autonomic to salivary glands

Question 20

What is the function of the following cranial nerves (motor&/sensory, autonomic?):
10 Vagus
11 Accessory
12 Hypoglossal

Answer 20

10 autonomic motor to thoracic and abdominal organs
autonomic sensory from thoracic and abdominal organs
11 motor to head, shoulders, pharynx, larynx and soft palate
12 motor to tongue

Question 21

There are 12 cranial nerves which are usually examined together.
Briefly outline the examination of the cranial nerves:

Answer 21

1 olfactory - ask about/test sense of smell
2 optic - test coloured vision/visual acuity/visual fields. Ophthalmoscopy to visualise the optic disc.
3 oculomotor, 4 throchlear, 6 abducens - ask pt to look at and follow your finger, make an H movement
5 trigeminal - sensory: test all sensory modalities at the 3 main branches (ophthalmic, maxillary, mandibular)
motor: test the temporal and master muscles by asking pt to clench their teeth
7 facial nerve - ask pt to shut their eyes as tight as posssible, raise their eyebrows then smile and whistle. Also test sensation on anterior 2/3 tongue.
8 vestibulocochlear - whisper in ear and ask them to repeat. Ring&Weber tests.
9 glossopharyngeal nerve, 10 vagus - tickle back of pharynx and look for gag reflex.
11 accessory - ask pt to shrug shoulders against resistance(trapezius muscle) and turn head on each side against resistance (sternocleidomastoid)
12 hypoglossol - tongue out as far as poss, is it straight or deviated to one side?