CMB1004-L12: the central and peripheral nervous systems

what are the 2 main division of the human nervous system

1. central nervous system( CNS)- brain and spinal cord

2. peripheral nervous system (PNS)- cranial nerves, nerve ganglia and peripheral nerves

what are the 3 functional types of neurones

1. motor/efferent neurones

2. interneurons/multipolar in the CNS

3. sensory/afferent neurones, which can be pseudo-unipolar or bipolar

what are the unique properties of neurons

1. do not divide, they lose mitotic ability after fetal development

2. longevity, can last a lifetime

3. high metabolic rate, requiring abundant oxygen and glucose

what are the 2 main types of electrical signals in neurons

1. action potentials; large, uniform depolarizations that travel long distances without losing strength; all or nothing response

2. graded potentials; variable strength signals that travel short distances and lose strength

where do graded potentials occur in neurons

in dendrites, cell bodies or axon terminals, not in axons like APs

how are graded potentials different from action potentials

graded potentials are proportional to the strength of the stimulus, wheras action potentials are all or none response

what is a depolarizing graded potential called

an excitatory postsynaptic potential (EPSP)

what causes hyperpolarizing graded potentials

influx of Cl^- ions or efflux of K⁺ ions

what is a hyperpolarizing graded potential called

an inhibitory postsynaptic potential (IPSP)

what determines the size or amplitude of a graded potential

• Large stimulus → strong graded response

• Small stimulus → weak graded response

what is the equivalent of a graded potential in muscle cells

the end plate potential (EPP)

what is subthreshold EPSP

failing to reach threshold

what is suprathreshold

reaches threshold