Biology Unit 1 – Maintaining Dynamic Equilibrium II
Section 1 – Nervous System
The basic functional unit of the nervous system.
Function: Send impulses to and from the CNS and PNS and the effectors (muscles/glands)
Dendrite Fine hair-like extensions on the end of a neuron.
Function: receive incoming stimuli.
Cell Body or Soma The control center of the neuron.
Function: Directs impulses from the dendrites to the axon.
Nucleus Control center of the Soma.
Function: Tells the soma what to do.
Axon Pathway for the nerve impulse (electrical message) from the soma to the opposite end of the neuron.
Myelin Sheath An insulating layer around an axon. Made up of Schwann cells.
Nodes of Ranvier Gaps between schwann cells.
Function: Saltatory Conduction (Situation where speed of an impulse is greatly increased by the message ‘jumping’ the gaps in an axon).
There are 3 types of neurons.
Sensory Neurons Neurons located near receptor organs (skin, eyes, ears).
Function: receive incoming stimuli from the environment.
Motor Neurons Neurons located near effectors (muscles and glands)
Function: Carry impules to effectors to initiate a response.
Interneurons Neurons that relay messages between other neurons such as sensory and motor neurons. (found most often in Brain and Spinal chord).
Types of Neurons
Nerves Collections of neurons that are joined together by connective tissue.
Responsible for transferring impulses from receptors to CNS and back to effectors.
Neuron at Rest Resting Potential
Occurs when the neuron is at rest.
A condition where the outside of the membrane is positively(+) charged compared to the inside which is negatively(-) charged.
Neuron is said to be polarized.
Neuron has a voltage difference of -70 mV