The nervous system

Question 1

Neurons

Answer 1

• cells that receive and transmit electrochemical signals
• 100 billion neurons
• each neuron connects with up to 10,000 other neurons
• we lose 85,000 neurons a day
• unipolar, bipolar, multipolar, interneurons
• interneurons: integrate neural activity within a specific structure

Question 2

The nervous system

Answer 2

• neurones conduct and transmit electrochemical signals through NS
• signals generated in resting neurons and transmitted across synapses

Question 3

The central nervous system

Answer 3

• NS division located in the skull and spine (brain, spinal chord)

Question 4

The peripheral nervous system

Answer 4

• division outside skull and spine
  Somatic nervous system: voluntary control of body movements (interacts with external environment)
  Afferent nerves: carry sensory signals from skeletal muscles, skin, joints, etc to CNS
  Efferent nerves: carry motor signals from the CNS to skeletal muscles
  Autonomic nervous system: regulates the body’s internal environment
  Afferent nerves: carry sensory signals from internal organs to CNS
  Efferent nerves: (carry sensory signals from CNS to internal organs
  Sympathetic nerves: stimulate, mobilise and organise energy in threatening situations (associated with arousal)
  Parasympathetic nerves: conserve energy (changes associated with relaxation)

Question 5

Meningies

Answer 5

the brain is protected by bone and three protective membranes (meninx)
1. Dura mater
2. Arachnoid membrane (below is the subarachnoid space: contains large blood vessels and cerebrospinal fluid)
3. Pia mater (adheres to the surface of the CNS)

Question 6

Ventricles and cerebrospinal fluid (CSF)

Answer 6

• CSF fills to subarachnoid space, central canal of spinal cord and cerebral ventricles of the brain
• cerebral ventricles: 4 large internal chambers of the brain
• CSF is produced but the choroid plexuses (network of capillaries from the Pia mater)
• CSF is absorbed into the dural sinuses and drains into the veins of the neck
• CSF supports and cushions the brain

Question 7

Blood brain barrier (BBB)

Answer 7

• made up of tightly packed cerebral blood vessels, which don’t allow large molecules (eg protein) to pass through to the brain
• blood vessels are not tightly packed in the rest of the body allowing molecules to pass easily
• still allows certain molecules especial for normal brain function to pass such as glucose
  impairment of BBB can lead to CSF disorders (eg MS)

Question 8

Glia cells

Answer 8

• equal number of neurons and glia cells
  4 types:
• Oligodendrocytes (CNS): wrap around axons, rich myelin which speeds up axonal conduction
• Schwann cells (PNS): constitutes in myelin, guides axonal regeneration
• Microglia: respond to injury or disease by multiplying and engulfing cellular debris
• Astrocytes: largest glia cell, star shaped, allow passage of some chemicals in CNS and blocking others

Question 9

Cell membrane

Answer 9

• lipid bilayer: two layers of fat molecules
• Channel proteins: allow certain molecules to pass through them
• Signal proteins: transfer a signal to the inside of a neutron when a molecule binds with them
• Phospholipids: hydrophilic heads, hydrophobic tails

Question 10

Neuroanatomical techniques

Answer 10

• neurons are tightly packed = difficult to see
  neural tissues can be prepared to see structure more clearly
• Golgi stain: silver chromate stain, make overall shape of neuron visible (not internally though)
• Nissl stain: gives indication of amount of neurons in an area, penetrates all cells but binds only to cell body
• Electron microcopy: can capture neuronal structures in great detail
• Tracing techniques: path of axons can be traced using anterograde (from cell body to terminal buttons) or retrograde