Anatomy of brain nervous system

Question 1

Where is grey matter located?

Answer 1

Outer edges of the brain
CEREBRAL CORTEX

Question 2

Where is white matter located?

Answer 2

Inner part of the brain

Question 3

Function of white matter

Answer 3

White matter- myelinated axons (nerve
cell fibres) which connect various grey
matter areas of the brain to each other.
They carry nerve impulses between
neurons.

Question 4

The function of grey matter

Answer 4

Grey matter- nerve cell bodies and unmyelinated axons.
Handles muscle control and sensory perception such as seeing,

hearing, memory, emotions, speech, decision making and self-
control.

Question 5

Structure of grey matter

Answer 5

Made of multiple folds and
grooves known as sulci and gyri
* This increases surface area
much like the bowel

• Gryrus- Folds in the cortex
• Sulcus- Small inlets between the
  folds, contains CSF

Question 6

Cerebrum info

Answer 6

Divided by a deep cleft called the longitudinal
cerebral fissure

• This separates the cerebrum into a right and a left
  hemisphere, each contains a lateral ventricle
• Hemispheres are connected by a mass of white
  matter (nerve fibres) called the corpus callosum

Question 7

Lobes of the brain

Answer 7

Frontal
Temporal
Parietal
Occipital

Question 8

Cerebellum

Answer 8

Motor control
 Coordination of voluntary
muscular movement, posture
and balance

 Damage to cerebellum causes
clumsy uncoordinated
muscular movement,
staggering gait and an
inability to carry out steady
and precise movements

Question 9

The meninges, what are they

Answer 9

(Outside to in)–
Dura Mater, Arachnoid
mater, Pia Mater

Question 10

Dura matter

Answer 10

Made up of 2 layers of dense fibrous
tissue

 Inner surface of skull and protective
covering for the brain

 Forms the Falx Cerebri, Falx Cerebelli and
Tentorium Cerebelli

Question 11

Arachnoid mater

Answer 11

Delicate layer

 CSF flows in the subarachnoid
space

 Arachnoid villi in venous sinuses
allow CSF to exit subarachnoid
space and enter the bloodstream

Question 12

Pia mater

Answer 12

Impermeable to fluid

 Works with other Dura to
protect and cushion the
brain

 Allows passage of blood
vessels to brain

Question 13

Ventricles

Answer 13

Lateral Ventricles
Third ventricles
Fourth ventricles

Question 14

What is CSF?

Answer 14

Created in the choroid plexus in the lateral ventricles
Fluid contained in the central canal of spinal cord, subarachnoid space and cerebral ventricles

Clear, colourless, transparent fluid
 Water (99%)
 Mineral Salts (sodium, calcium, potassium, amongst others)
 Glucose
 Amino Acids
 Creatinine/Urea (trace amounts)
 Lymphocytes

Question 15

Absorption of CSF

Answer 15

Mostly absorbed by Arachnoid Villi on the Arachnoid Mater into the Dural (Venous) Sinuses

 The absorption is determined by the pressure differences on each side of the villi walls.

  CSF pressure, venous pressure, CSF passes into blood

  venous pressure,  CSF pressure, arachnoid villi collapse preventing passage of Blood
constituents into CSF

 Consistent volume c. 120 ml

Question 16

What are Glial Cells (neuroglia)?

Answer 16

Support cells insulate, protect and support neurones

Question 17

Resting neuron charges

Answer 17

When a neurone is resting, the nerve cell membrane is polarised due to differences in the
concentrations of ions across the plasma membrane. This means there is a different
electrical charge on each side of the membrane.

• At rest the charge on the outside of the cell is positive, inside it is negative. It is negative
  due to a high number of negatively charged ions.

Question 18

Stimulation, depolarisation

Answer 18

When stimulated the nerve cell membrane becomes more permeable to the ions.

• Sodium channels open up which allows the +ve sodium ions to move into the neurone from
  outside the cell. This causes rapid depolarisation which creates an action potential or a nerve
  impulse.
• movement of sodium and potassium is done by Active Transport as the cells are moving against
  a concentration gradient. This is done with pure glucose. (which is why you need sugar when
  you are studying as your brain is using it so much!!)

Question 19

Repolarisation

Answer 19

Due to the influx of Sodium into the neurone, channels open up in the cell membrane for
potassium to use.

• Potassium ions move out of the neurone due to the influx of Sodium which returns the
  membrane potential to its resting state.
• Although the cell is now repolarised, the potassium and sodium are in the wrong place so the
  sodium-potassium pump begins to pump the sodium back out and the potassium back in (again
  by active transport).
• The neurone is back to its resting membrane potential ready to receive another impulse.

Question 20

What is Sensory (Afferent)

Answer 20

Sensory receptors on dendrites of
nerves generate Action Potential

 Transmitted to the spinal cord by
sensory nerve fibres.

 Impulses pass to brain or to reflex
arcs in spinal cord

Question 21

Motor (Efferent)

Answer 21

Action Potential originates in brain
or spinal cord

 Transmitted to effector organs e.g.
muscles and glands

 Somatic & Autonomic

Question 22

4 types of glial cells which support the
neurones of the CNS.

Answer 22

 Unlike neurones these can replicate

 Neuroglia- Do not transmit impulses

 Astrocytes- star shaped, control the blood brain barrier
 Oligodendrocytes- support and insulate axons
 Microglia- Immune defence cells
 Ependymal Cells- CSF production

Question 23

The blood-brain barrier function

Answer 23

Semi-permeable

 Oxygen and Carbon Dioxide pass quickly across the barrier, as do alcohol, barbiturates
and glucose

 Larger molecules including drugs, inorganic ions and amino acids pass more slowly
from the blood to the brain.

 Maintains constant environment (homeostasis) for the neurones in the CNS

 Protects the brain from potential toxins in the blood

 Prevents the escape of neurotransmitters from the CNS into general circulation

Question 24

What affects the permeability of
the blood brain barrier?

Answer 24

1) Hypertension
2) Development
3) Microwaves
4) Infection
5) Trauma, Ischemia, Inflammation and Raised Pressure
(Intracranial Pressure)