0. PRIMER TO THE NERVOUS SYSTEM
1. STRUCTURE AND FUNCTION OF THE NERVOUS SYSTEM
➢ The nervous system is responsible for the reception and processing of sensory information from
both the external and internal environments
➢ The nervous system has two major divisions
o CNS – consisting of the brain and the spinal cord
o PNS – consisting of nerves lying outside the CNS
➢ The nervous system has three specific functions
o Receiving sensory input Sensory receptors → PNS →
o Information processing and integration CNS →
o Generating motor output PNS → muscles, glands and organs
Figure 1
The two divisions of the nervous system. a. The central nervous system (CNS) consists of the brain and spinal cord.
The peripheral nervous system (PNS) consists of the nerves, which lie outside the CNS. b. The red arrows are the
pathway by which the CNS receives sensory information. The black arrows are the pathway by which the CNS
communicates with the somatic nervous system and the autonomic nervous system, two divisions of the PNS.
, 2. NERVOUS TISSUE
➢ Nervous tissue contains two types of cells
o Neurons – transmit nerve impulses between parts of the nervous system
o Neuroglia/glial cells – support and nourish neurons
▪ Microglia – help remove bacteria and debris
▪ Astrocytes – provide metabolic and structural support
▪ Schwann cells – form the myelin sheath in the PNS
▪ Oligodendrocytes – form the myelin sheath in the CNS
3. NEURON ATONOMY
➢ The three types of neurons
o Sensory neurons – takes nerve signals from an sensory receptor to the CNS
o Interneurons – sum up all in the information received in the CNS
o Motor neurons – takes nerve impulses away from the CNS to an effector
➢ All neurons have three distinct structures: a cell body, dendrites and an axon (= nerve fiber)
➢ Long axons are covered by a protective myelin sheath
o Nodes of Ranvier – gaps where there is no myelin sheath
o Plays an important role in the rate at which signals move through the neuron and in nerve
regeneration within the PNS
o White matter – myelinated axons vs. gray matter – no myelinated axons
o Multiple sclerosis – break down of the myelin, which makes it more difficult for the neurons to
transmit information (MS ‘’short-circuits’’ the nervous system)
Figure 2
The structure of sensory neurons, interneurons, and motor
neurons. a. A sensory neuron has a long axon covered by a myelin
sheath that takes nerve impulses all the way from dendrites to the
CNS. b. In the CNS, some interneurons, such as this one, have a short
axon that is not covered by a myelin sheath. c. A motor neuron has
a long axon covered by a myelin sheath that takes nerve impulses
from the CNS to an effector.
1. STRUCTURE AND FUNCTION OF THE NERVOUS SYSTEM
➢ The nervous system is responsible for the reception and processing of sensory information from
both the external and internal environments
➢ The nervous system has two major divisions
o CNS – consisting of the brain and the spinal cord
o PNS – consisting of nerves lying outside the CNS
➢ The nervous system has three specific functions
o Receiving sensory input Sensory receptors → PNS →
o Information processing and integration CNS →
o Generating motor output PNS → muscles, glands and organs
Figure 1
The two divisions of the nervous system. a. The central nervous system (CNS) consists of the brain and spinal cord.
The peripheral nervous system (PNS) consists of the nerves, which lie outside the CNS. b. The red arrows are the
pathway by which the CNS receives sensory information. The black arrows are the pathway by which the CNS
communicates with the somatic nervous system and the autonomic nervous system, two divisions of the PNS.
, 2. NERVOUS TISSUE
➢ Nervous tissue contains two types of cells
o Neurons – transmit nerve impulses between parts of the nervous system
o Neuroglia/glial cells – support and nourish neurons
▪ Microglia – help remove bacteria and debris
▪ Astrocytes – provide metabolic and structural support
▪ Schwann cells – form the myelin sheath in the PNS
▪ Oligodendrocytes – form the myelin sheath in the CNS
3. NEURON ATONOMY
➢ The three types of neurons
o Sensory neurons – takes nerve signals from an sensory receptor to the CNS
o Interneurons – sum up all in the information received in the CNS
o Motor neurons – takes nerve impulses away from the CNS to an effector
➢ All neurons have three distinct structures: a cell body, dendrites and an axon (= nerve fiber)
➢ Long axons are covered by a protective myelin sheath
o Nodes of Ranvier – gaps where there is no myelin sheath
o Plays an important role in the rate at which signals move through the neuron and in nerve
regeneration within the PNS
o White matter – myelinated axons vs. gray matter – no myelinated axons
o Multiple sclerosis – break down of the myelin, which makes it more difficult for the neurons to
transmit information (MS ‘’short-circuits’’ the nervous system)
Figure 2
The structure of sensory neurons, interneurons, and motor
neurons. a. A sensory neuron has a long axon covered by a myelin
sheath that takes nerve impulses all the way from dendrites to the
CNS. b. In the CNS, some interneurons, such as this one, have a short
axon that is not covered by a myelin sheath. c. A motor neuron has
a long axon covered by a myelin sheath that takes nerve impulses
from the CNS to an effector.
