WEEK 3 LECTURE + TUTORIAL Flashcards
SUPPORTING THE BRAIN (32 cards)
Meninges
Tough connective tissue which covers the CNS and some of the PNS
Prevents brain displacement
Impermeable to fluid, stops CSF leakage
Dura Matter
Outer layer, thick, tough and flexible
Arachnoid membrane
Middle layer, located between the dura matter and pia matter, soft and spongey
Pia Matter
Clings to the surface of the brain and spinal cord, thin delicate
-smaller surface blood vessels found here
Subarachnoid Matter
Fluid-filled space between arachnoid membrane and pia matter, cushions the brain
CNS + Meninges
Covered by three layers of meninges
Dura matter, arachnoid membrane and pia matter
PNS + Meninges
two layer fuse
Dura and Pia matter fuse
sheath protects spinal and cranial nerves and the autonomic ganglia
Arachnoid membrane not present
Ventricular System
-Ventricles: Hollow spaces within the brain, filled with cerebrospinal fluid
-CSF: clear fluid, similar to blood plasma
-Brain floats in a pool of CSF
Four ventricles
-Lateral Ventricles: sited in the centre of the telencephalon
-3rd ventricle: sited at the midline of the centre of the diencephalon
-Cerebral Aqueduct: Long tube in mesencephalon connects 3rd and 4th ventricles
-4th ventricle: found between the cerebellum and pons
Two main functions of Ventricles
- Production and flow of CSF
- Protection of the CNS and maintenance
*CSF produced by tissue inside ventricle walls called chloride plexus, filters CSF from blood plasma
Cerebrospinal Fluid/ CSF
- Extracted from blood
-Contains ions, water, protein and glucose
-Produced constantly from choroid plexus - Total volume of CSF is -125ml
-Takes 3 hrs for half of CSF to be replaced
CSF Flow
- Produced by the choroid plexus of lateral ventricles
-Flows to 3rd ventricle where more is produced
-Flows through cerebral aqueduct to 4th ventricle
-Leaves ventricles to flow into subarachnoid space around CNS- where it is reabsorbed into bloodstream through arachnoid granulations
CSF Vital Functions
-Protection (reduces shock caused by sudden head movement)
-Buoyancy (reduces the weight on the base of the brain, allowing floating)
-Waste Reduction (Provides immunological protection to the brain, removes harmful chemicals
-Transport (Transports hormones through the brain)
Too much CSF issues / Hydrocephalus
-Leads to ventricular dilation
Classified into two types:
1. Obstructive hydrocephalus
2. Communicating hydrocephalus
Amyotrophic lateral sclerosis (ALS) : Lou Gehrig’s disease
- Most common form of motor neuron disease
-Attacks nerve cells
-Loses all voluntary muscle control
Glia
- Supporting cells for the NS
- Several types:
1. Astrocytes
2. Microglia
3.Oligodendrocytes
4.Schwann Cells
Astrocytes
- Physical support, neuron glue
-Nourish neurons, wrap blood vessels to receive, store and release nutrients
-Helps control chemical composition of extracellular fluid
-Surround and isolate synapse which helps limit the dispersion of neurotransmitters that are released during a synapse by the terminal buttons
-Known as the ‘star cell’
-Phagocytosis (engulf) clean up debris in the brain
Microglia
- Smallest glial cells
-Phagocytes
-Representative of immune system in the brain
-Responsible for inflammatory reaction in response to brain damage
-Thought to have a role in Neurodegenerative disorders
Oligodendrocytes + Schwann cells
- Oli = CNS
- Schwann = PNS
-Contains fatty tissue called myelin that wraps around neuron axons
Forms insulating coating: Myelin Sheath
Schwann = Wrap individual axons
Oli = Wrap several axons
Basic Blood Functions
- Blood brings materials necessary for the brain to function
-oxygen, nutrients hormones - Blood removes materials from the brain
-Carbon dioxide
-Lactate
-Hormones
-Ammonia
-
*Helps maintain homeostasis
Blood Brain Barrier (BBB)
- Semi-permeable barrier between blood and the brain
-Capillaries are lined with endothelial cells, small spaces exist between each endothelial cell so substances can move across capillary walls
BBB main functions
- Protects the brain from ‘foreign substances’ in blood which may injure the brain
- Protects the brain from hormones and neurotransmitters in the rest of the body
- Maintains a constant environment for the brain
Substances and BBB
- lipid soluble molecules can penetrate through BBB relatively easily via lipid membranes of cells
-Water soluble molecules can only use specialised carrier-mediated transport mechanisms
-Active transport allows some substances to move across capillary walls
-Barrier is weak in some areas
Meningitis Symptoms
- Inflammation of the meninges, neck stiffness, fever, confusion, altered mental status, headaches, nausea, sepsis, cold hands and feet, red rash, breathing faster than usual
