Transcript The Nervous System

The Nervous System
Control Center for Maintaining
Homeostasis
Nervous System
The nervous system coordinates the activities of
all of the body’s organ systems so that they work
in concert with one another
What systems must cooperate during exercise?
What do we use to respond to changes in the
external environment?
Do the senses operate individually?
Components of the Nervous System
Two main sections
The Central Nervous System
 Brain and spinal cord
 coordinating center for incoming and outgoing
information
Peripheral Nervous system
 Nerves that extend to the rest of the body
 Carries information between organs and the CNS.
Two basic types of Nerves
sensory or afferent nerves
Carry signals to CNS
motor or efferent nerves
Carry signals from CNS
Peripheral Nervous System (PNS)
Somatic nerves
connect skin, skeletal muscles and bones to
CNS
Autonomic nerves
Connect visceral organs
Somatic nerves
control skeletal muscles, bones and skin
Voluntary
 Sensory to CNS
 CNS to Motor
Reflexes
Autonomic nerves
Special motor nerves that control the internal organs
Comprised of two divisions that work in opposition
 Sympathetic nerves
• Fight or flight response (survival)

Parasympathetic nerves
• Active when body is at rest
• “resting and digesting”
Autonomic
Broken into two different divisions (systems)
the Parasympathetic and Sympathetic
Parasympathetic


House keeper division
Uses acetylcholine (neurotransmitter)
Sympathetic


Excitatory division
Uses norephinephrine (neurotransmitter)
What is a Nerve
A Collection of nerve fibers in the peripheral
nervous system
Cells of the Nervous System
Two type of cells that make up
nerve fibers
Neurons
Supportive cells
 Neuroglia
 Schwann cells
Nerve Cells
Neurons transmit electrochemical signals
along their length

cell body

dendrites

Axon

axon terminals
Cell Body
The Cell body contains all of the cell organelles.
Such as the:
Nucleus
Mitochondria…
Important in the manufacturing
of Neural transmitters.
Dendrites
The Branching structure that
receives signals from other
Nerves or if they are sensory
Neurons receive signals
externally.
Conducts the nerve impulse to
towards the cell body.
Axon
the long extension of a neuron that carries
nerve impulses away from the body of the
cell.
Link the Nerve to either the next nerve
(sensory or interneuron) or to a muscle
(motor neuron)
Axon
Usually much longer than a Dendrite and usually
covered with a insulating layer called the myelin
sheath.
axon terminals - the the hair-like ends of axon
Release chemicals (neurotransmitters) to transmit
signal to next neuron in junction
Junctions between neurons and another cell called a
synapse
Supportive Nerve Cells
Glial Cells supporting cells that usually form a
type of protection and insulation for electical
conduction
Proper names for CNS and PNS
Neuroglia in CNS
Schwann cells in PNS
Glial Cells in PNS
Myelin Sheath
Myelin is the fatty substance that wraps around
axons and protects/insulates them
Formed by Schwann Cells in the PNS,
gaps called Nodes of Ranvier are left between the
myelin
Myelination and the Nodes of Ranvier increase the
speed that the electrical signal moves down the
axon.
Myelin Sheath
New research suggest that the electrical wave
that travels down the axon actually jumps from
one node to another. Thereby increasing the
speed of transmission.
Multiple sclerosis is caused by the destruction of
the myelin sheath
Neurilemma
All nerves in the peripheral nervous system
contain a thin membrane called the neurilemma.
It surrounds the axon and promotes regeneration
of damaged axons.
Neurilemma
Nerves in the brain that contain myelin sheath
and neurilemma are called white matter and
those that aren’t is the gray matter. Damage to
the gray matter is permanent.
Different Types of Neurons
They all carry electro-chemical nerve signals, but differ
in structure
(the number of processes, or axons, emanating from the cell
body) and are found in different parts of the body.

Sensory neurons

Motor-neurons

Interneurons
Interneurons
form all the neural wiring within the CNS.
have two axons (instead of an axon and a
dendrite).
one axon communicates
with the spinal cord
Other one with either
the skin or muscle.