Download Neurons

Neurons and the
Nervous System
Nervous System
– Central nervous system (CNS):
• Brain
• Spinal cord
– Peripheral nervous system (PNS):
• Sensory neurons
• Motor neurons (somatic and
autonomic)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
The Nervous System
The Nervous System
Central Nervous System (CNS)
Brain
Peripheral Nervous System (PNS)
Spinal Cord
•
Motor Neurons
Somatic Nervous System
voluntary movements via
skeletal muscles
Sympathetic
- “Fight-or-Flight” responses
•
Sensory Neurons
Autonomic Nervous System
organs, smooth muscles
Parasympathetic
- maintenance
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Divisions of the autonomic nervous system
The Nervous System
• A physical organ system like any
other
• The main cell of the nervous
system are:
–Neurons
The Neuron
• The basic functional
unit of the nervous
system.
• Function: Send
impulses to and from
the CNS and PNS
Neuron Structure
• 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.
– Conduction of the impulse. (Situation
where speed of an impulse is greatly
increased by the message ‘jumping’ the
gaps in an axon).
Types of Neurons
• There are 3 types of neurons.
1. Sensory Neurons  Neurons located near receptor
organs (skin, eyes, ears).
 Function:
receive incoming stimuli from the
environment.
2. Motor Neurons  Neurons located near effectors
(muscles
and glands)
 Function:
Carry impules to effectors to initiate a
response.
3. 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
Sensory vs. Motor
sensory nerve
e.g., skin
Neurons that send signals from the senses,
skin, muscles, and internal organs to the CNS
motor nerve
Neurons that transmit commands from the
CNS to the muscles, glands, and organs
Gray’s Anatomy 38 1999
e.g., muscle
Nerves
• Nerves  Collections of neurons
that are joined together by
connective tissue.
• Responsible for transferring
impulses from receptors to CNS
and back to effectors.
Neuron Anatomy and Neural
Communication
Neurons
Dendrites
Cell Body
Myelin
Sheath
Axon of another
neuron
Axon
Dendrites of
another neuron
Neural Anatomy and
communication
 Synapse
 junction between the axon tip of
the sending neuron and the
dendrite or cell body of the
receiving neuron
 tiny gap at this junction is called
the synaptic gap or cleft
Specific Parts: The Neuron
Structure
Specific Parts: The Neuron
Function
1.
3.
2.
Neurons = 3 functions: Reception, Conduction, Transmission
Communication
• Impulse releases
neurotransmitter from
vesicles
• Neurotransmitter
enters synaptic gap
• Neurotransmitter
binds to receptors on
the receiving neuron
Place of the PNS in the structural organization of the nervous system
CNS
PNS
Motor division
Sensory division
Sympathetic
division
Parasympathetic
division
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Autonomic
nervous
system
Somatic
nervous
system
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Central Nervous System
The Brain
• cerebral cortex: the covering,
where most mental processes
take place
• The brain is divided into two
halves (cerebral hemispheres)
separated by a deep fissure
– hemispheres control
opposite side of body (e.g.
right-handers’ writing is
controlled by the left
hemisphere)
Our Divided Brain
• cerebral
hemispheres
connected by the:
– corpus callosum,
a large band of
neural fibers that
transmits
messages
between
hemispheres
Structure of the Cortex
• cerebral cortex divided
into lobes, or regions of
the brain
– Each lobe is (roughly)
responsible for
different higher-level
functions, but
remember that they
do not work merely in
isolation.
Structure of the Cortex
• occipital lobe: brain
lobe at the back of the
head
– responsible
primarily for vision
Structure of the Cortex
• temporal lobe: the brain
lobe under the temples, in
front of the ears
– many functions,
including receiving and
processing sounds,
comprehending
language committing
information to long term
memory, emotion
Structure of the Cortex
• parietal lobe: brain
lobe at the top and
center/rear of the
head
–involved in
registering spatial
location, body
awareness, touch
and pressure, taste
Structure of the Cortex
• frontal lobe: the brain lobe
located behind the forehead
– Movement of body,
personality, concentration,
planning, problem solving,
meaning of words, emotional
reactions, speech and smell.
– In many ways, the frontal
lobe is what makes us
uniquely human.
Our Divided Brain
• cerebral
hemispheres
connected by the:
– corpus callosum,
a large band of
neural fibers that
transmits
messages
between
hemispheres