Lecture 4 Flashcards
A neuron receives 547 EPSP and 526 IPSP. This neuron will be:
A. Depolarized
B. Inhibited
C. Neither depolarized nor inhibited
B. 548-526=21, in order for a neuron to be depolarized, it requires 50-100 EPSPs.
What is myelin formed by?
Cell membrane of glial cells (Schwann cells in PNS, oligodendrocytes in CNS)
*Made of fat
Where do ion channels cluster on neurons?
Nodes of Ranvier (gaps in myelin sheath)
At what speed are AP’s transmitted in myelinated axons?
Avg 100m/sec
At what speed are AP’s transmitted in un-myelinated axons?
Avg 1m/sec (way too slow)
Which axon will conduct action potentials faster?
A. Large diameter
B. Small diameter
A
Which axon will conduct action potentials faster?
A. Thick myelin sheath
B. Thin myelin sheath
A
Explain the role of myelin in Multiple Sclerosis
- The immune system attacks oligodendrocytes in the brain and spinal cord (CNS)
- Damages axons in later states of the disease
- Forms “sclerotic plaques” visible on MRI
- Overall decreased transmission of action potential
Explain the role of myelin in Guillain-Barre Syndrome
- The immune system attacks schwann cells in the PNS (cranial nerves and spinal nerves)
- Some variants damage axons
- Autoimmune disease, usually preceded by an infection
What type of glial cell creates the Blood Brain Barrier? How do they do this?
Astrocytes
-Have processes called “endfeet” that surround capillaries in the brain and spinal cord –> these direct the capillary endothelial cells to create the BBB
What type of glial cells remove dead cells?
Microglia
-CNS phagocytes
What type of glial cells produce and secrete cerebrospinal fluid (CSF)?
Ependymal cells
What are the three stages of development of the nervous system in the first 28 days gestation?
- Neural plate
- Neural fold
- Neural tube (neural crest)
What does the neural crest form?
- Sympathetic trunk
- Dorsal root ganglia
- Adrenal medulla
- Enteric nervous system (GI tract neurons)
What does the neural tube form?
- Brain
- Spinal cord
What are the two types of neural tube defects?
- Anencephaly
- Spina bifida
Which neural tube defect is incompatible with life? Why?
Anencephaly. The neural fold does not fully close into the neural tube in the cranial direction (brain/spinal cord don’t form)
What happens to the neural tube in spina bifida?
The neural fold doesn’t close into the neural tube in the caudal direction
What can reduce the risks of neural tube defects?
Folic acid
What parts of the brain form from the cranial direction?
Forebrain, midbrain, hindbrain
What parts of the brain form from the caudal direction?
Spinal cord
What structures does the forebrain form?
- Right and left cerebral hemispheres
- Diencephalon = thalamus and hypothalamus
What structures form from the hindbrain?
- Cerebellum
- Pons
- Medulla
Where is cerebrospinal fluid produced?
Ventricles
Where does CSF move around?
Subarachnoid space
What is the order of meninges from deep to superficial?
-Pia mater, arachnoid (subarachnoid space in between these two), dura mater
What is the flow of ventricles from cranial to caudal?
Right and Left lateral ventricles –> 3rd –> cerebral aqueduct –> 4th –> subarachnoid space* or central canal
*After subarachnoid space –> dural sinuses –> heart
