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Anatomy & physiology. Part 1: The Nervous System. Three Functions of the Nervous System:. Sensory Input : Gathers stimuli (receives information) Integration : Processes and interprets information Motor Output : Causes a response to muscles or glands. ?.

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anatomy physiology
Anatomy & physiology

Part 1:

The Nervous System

three functions of the nervous system
Three Functions of the Nervous System:
  • Sensory Input:
    • Gathers stimuli (receives information)
  • Integration:
    • Processes and

interprets information

  • Motor Output:
    • Causes a response

to muscles or glands

organization of the nervous system
Organization of the Nervous System:

Structural Classification:

Functional Classification:

  • Central Nervous System (CNS): brain & spinal cord
  • Peripheral Nervous System (PNS): spinal & cranial nerves
  • Sensory Division (a.k.a. Afferent): nerves carrying info to the CNS from the body
  • Motor Division (a.k.a. Efferent): nerves carrying info from the CNS to the muscles or glands
  • This includes:
    • Somatic Nervous System: voluntary control (skeletal muscles)
    • Autonomic Nervous System (ANS): involuntary control (smooth & cardiac). This includes: sympathetic & parasympathetic.
supporting cells of the nervous system
Supporting Cells of the Nervous System:

1. Microglial cells:support neurons & carry out phagocytosis

2. Oligodendrocytes: form myelin within the brain; occur in rows along nerve fibers

3. Astrocytes: found between neurons & bv’s; support, regulate [nutrients] & [ions], & form scar tissue following a CNS injury.

4. Ependymal cells: membrane like structure that covers parts of the brain(choroid plexuses) & forms inner linings of brain (ventricles) & spinal cord(central canal).


neurons nerve cells
Neurons: Nerve Cells
  • Neurons vary in size, shape & function
  • Mature neurons do NOT divide
  • All neurons have:
    • A cell body is the main component of a neuron. It contains cytoplasm, a cell membrane,

a nucleus, &


    • The ER of a cell body

is called the




(perform protein


neuron anatomy
Neuron Anatomy:
  • Dendrites and axons are nerve fibers that attach to the cell body (most neurons have these).
  • Dendrites (usually more than 1 on a cell body) are the communication means of one neuron to the next. They receive messages. These are short branched fibers.
  • Axonstake impulses away from the cell body. They are usually one fiber with side branches.

Large axons have a covering sheath called a myelin sheath (a membrane of lipoprotein).

  • The myelin sheath is composed of Schwann cells (neuroglial cells).
  • The gaps between the myelin sheaths are called nodes of Ranvier.
  • In the CNS, white matter are the fibers that are myelinated while gray matter are the fibers that are unmyelinated.
  • Nuclei: clusters of cell bodies in the CNS
  • Ganglia: small clusters of cell bodies in the PNS (outside the CNS)
  • Tracts (or nerve tracts): bundles of nerve fibers running through the CNS
  • Nerves: fibers running through the PNS
  • White Matter: myelinated fibers
  • Gray Matter: unmyelinated fibers
types of neurons structural classification
Types of Neurons: Structural Classification:

1. Bipolar neurons: 2 nerve fibers, one at each end (1 axon & 1 dendrite). Found in the nose, eyes, & ears.

2. Unipolar neurons: 1 nerve fiber from the cell body that has 2 branches (1 branch acts as a dendrite & the other branch acts as an axon).

3. Multipolar neurons: many nerve fibers, 1 axon and many dendrites. Found in the brain & spinal cord.

types of neurons functional classification
Types of Neurons: Functional Classification:

1. Sensory neurons: carry impulses from peripheral body parts to brain & spinal cord (from PNS to CNS). Most are unipolar, some bipolar.

2. Interneurons: carry impulses between neurons. Multipolar neurons.

3. Motor neurons: carry impulses from the brain & spinal cord to the effectors (muscles & glands outside of the NS) to carry out a response. Multipolar.

nerve impulses
Nerve Impulses:
  • An unmyelinated nerve fiber carries an impulse slower than a myelinated nerve fiber.
  • Nerve impulses range in speed according to their diameter (thicker=faster). Ex: skeletal muscle travels ~120 meters/second
  • Nerve impulses respond in anall-or-none response.
  • More stimuli= more impulses (per second), not stronger intensity of impulses.
nerve impulses1
Nerve Impulses:
  • A synapse is a junction between 2 communicating neurons. The neurons are NOT connected.
  • A synaptic cleft is the gap between these 2 neurons.
  • A nerve impulse must jump this gap.
  • A neurotransmitter is a chemical that enables the impulse to jump the synaptic cleft.

  • There are 2 types:
    • Excitatory (increase membrane permeability) -impulse will likely occur
    • Inhibitory (decrease membrane permeability) -impulse will not likely occur
  • There are at least 50 known neurotransmitters, including these groups:
    • Acetylcholine (stimulates skeletal muscles)
    • Monoamimes (epinephrine, norepinephrine, dopamine, & serotonin)
    • Several amino acids
    • Peptides
  • These are rapid, involuntary responses
  • A reflex arc is the simplest nerve pathway that contains only a few neurons.
  • The withdrawal reflex is a protective reflex (pulling your finger away from a hot pot) b/c it limits tissue damage. In addition to this reflex, interneurons also trigger a response to pain.
  • Somatic reflexes includeskeletal muscles(pulling your hand away from a hot stove).
  • Autonomic reflexes include smooth and cardiac muscles as well as glands (pupils dilating, mouth ‘watering’)
  • The knee-jerk reflex is a nerve pathway involving only 2 neurons (1 sensory & 1 motor).

Withdrawal Reflex: