Nerve tissue

Question 1

Nervous tissue

Answer 1

• Sends and receives electrochemical signal.
• Excitable: Membrane of neuron able to change membrane potential.
  Two major anatomical divisions:
• Afferent: Sends signal from peripheral nervous system to the central nervous system.
• Efferent: Sends signal from CNS to PNS.

Question 2

Main types of cells

Answer 2

Neurons: Do the job, send and receive signals.
Neuroglia: Support neurons in their functions.

Question 3

Neuroglia

Answer 3

• Most abundant.
• Unable to generate action potential in plasma membrane.
• Protect neurons
• Insulation
• Repair
• Regulation of extracellular fluid in CNS.
• Clearance of neurotransmitters.
• Metabolic exchange, between vascular system and nervous system.

Question 4

Neuron structure

Answer 4

• Soma (cell body) contain most organelles.
• Dendrites (spikes): Receive info
• Axon (long part): sends info, propagate, action potential (nerve impulse), electric signal.
• Axon hillock (beginning of axon): Integration signals. Initiate action potential ( nerve impulse).
• Axon terminal (end of axon): Release of neurotransmitters.
  Synapse: place of contact between neurons and a cell.

Question 5

Structural classification

Answer 5

Nr. of processes arising from cell body.

• Multipolar: Multiple processes, one axon, rest dendrites. Most common.
• Bipolar: Two processes from cell body (soma in middle).
• Pseudo-unipolar: One process, splits into two axons (soma in middle and out).

Question 6

Functional classification

Answer 6

• Sensory neurons/afferent: Bipolar and pseudo-bipolar.
• Efferent, send out commands: Multipolar.
• Interneurons, 99%, intergrade info: Multipolar.

Question 7

Synaptic transmission

Answer 7

1. Action potential invades terminal.
2. Rapid influx of Ca2+, opening of voltage gated Ca2+ channels.
3. Fusion of synaptic vesicles with plasma membrane.
4. Neurotransmitters released into synaptic cleft.
5. NT bind to receptors on membrane.
6. Ion channels open.
7. Conductance and membrane potential altered resulting in changes in excitability.

Question 8

PNS neuroglia

Answer 8

Schwann cells: Myelination of axon. Impulse and isolation.

Satellite cells: Sensory neurons around the cell body.

Question 9

CNS neuroglia

Answer 9

• Oligodendrocytes: Myelination of axon.
• Astrocytes: Help maintain blood brain barrier. Metabolic support for neuron. Modulate activity. Reuptake of N.T. Regulate composition of CSF.
• Microglia: Phagocytosis
• Ependymal cells: Produce and circulate CSF.

Question 10

Blood Brain Barrier

Answer 10

• Protects CNS from fluctuating levels of electrolytes, hormones, tissue metabolites circulating in blood vessels.
• Highly selective semi-permable membrane barrier that separates circulating blood from brain and cerebrospinal fluid.