Bio 224 theme 5

Brain and spinal cord in vertebrates

(PNS) All neurons and projections of their plasma membranes that are outside of the CNS

• the major component of the CNS, consisting of:
• –Neuronal cell bodies, dendrites and axons;
• –Glial cells;
• –Capillaries;
• 
  

• mostly contains myelinated axon tracts
• –The color difference arises mainly from the whiteness of myelin.

• Generate, send and receive information
• through electrical and
• chemical signals;
• to and from other neurons or other cells throughout the body

sponges

neurons, muscle cells, and endocrine cells, as well as in some plant cells

• +30mV
• -50mV
• -70mV

• -an action potential is the first step in the chain of events leading to a contraction
• -release of insulin

Plasma membrane

the cell body or soma

Branched projections of a neuron that conduct the electrochemical stimulation received from other neural cells.

• -Long, slender projection of neurons
• -Conducts electrical impulses away from the soma;
• -rich in voltage-gated ion channels

• -place of transmission of neurotransmitters/electrical impulse, from axon to dendrite
• -full of neurotransmitter vesicles
• -Dendrite receptor is loaded with ligand gated ion channels

• •Non nervous cells of the NS
• –commonly known as the glue of the NS

• roughly 1:1
• in cerebellum 3:2

• 1.Astrocytes
• 2.Microglia
• 3.Ependymal cells
• 4.Oligodendrocytes
• 5.Satellite cells
• 6.Schwann cells

–star-shaped glial cells–provision of nutrients–maintenance of extracellular ion balance; –repair and scarring process of the brain and spinal cord; and–biochemical support of endothelial cells

• •A separation between the circulating blood and the brain extracellular fluid;
• •Consist of tight junctions around the capillaries that do not exist in normal circulation;
• –Restrict the diffusion of microscopic objects, e.g.•bacteria and large or hydrophilic molecules into CSF;
• •while allowing the diffusion of small hydrophobic molecules (O2, CO2, hormones).
• –Actively transport metabolic products such as glucose

• •The principal glia cells of the PNS
• -Wrap around axons of motor and sensory neurons to form the myelin sheath

• •;An electrically inulating material that forms a layer around axons
• •Essential for the proper functioning of the nervous system;
• •Composed of:
• – ~ 80% lipids, primarily the glycolipids galactocerebroside
• –~20% protein
• •myelin basic protein (MBP),
• •myelin oligodendrocyte glycoprotein (MOG), •proteolipid protein (PLP).

Schwann cells myelinate the PNS Oligodendrocytes myelinate the CNS

• •Interneurons or Association Neurons
• •Motor neurons
• •Sensory neurons

• –Form interconnections between other neurons in the CNS;
• –Tend to have many dendrites;
• –Axons are typically short and highly branched allowing them to form complex connections with other cells

–Efferent: send signals away from CNS to elicit response

• –Afferents: detect information from the outside world or internal body conditions & transmit to the CNS;
• –Usually a large axon that bypasses the cell body and goes directly to the CNS

• •The stimulus from sensory neurons is sent to the CNS, but there is little or no interpretation of the signal;
• –Few interneurons are involved
• •The signal is then transmitted to motor neurons, which elicit a response, such as a knee jerk