Anatomy of brain nervous system Flashcards
Where is grey matter located?
Outer edges of the brain
CEREBRAL CORTEX
Where is white matter located?
Inner part of the brain
Function of white matter
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.
The function of grey matter
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.
Structure of grey matter
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
Cerebrum info
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
Lobes of the brain
Frontal
Temporal
Parietal
Occipital
Cerebellum
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
The meninges, what are they
(Outside to in)–
Dura Mater, Arachnoid
mater, Pia Mater
Dura matter
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
Arachnoid mater
Delicate layer
CSF flows in the subarachnoid
space
Arachnoid villi in venous sinuses
allow CSF to exit subarachnoid
space and enter the bloodstream
Pia mater
Impermeable to fluid
Works with other Dura to
protect and cushion the
brain
Allows passage of blood
vessels to brain
Ventricles
Lateral Ventricles
Third ventricles
Fourth ventricles
What is CSF?
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
Absorption of CSF
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
What are Glial Cells (neuroglia)?
Support cells insulate, protect and support neurones
Resting neuron charges
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.
Stimulation, depolarisation
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!!)
Repolarisation
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.
What is Sensory (Afferent)
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
Motor (Efferent)
Action Potential originates in brain
or spinal cord
Transmitted to effector organs e.g.
muscles and glands
Somatic & Autonomic
4 types of glial cells which support the
neurones of the CNS.
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
The blood-brain barrier function
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
What affects the permeability of
the blood brain barrier?
1) Hypertension
2) Development
3) Microwaves
4) Infection
5) Trauma, Ischemia, Inflammation and Raised Pressure
(Intracranial Pressure)
