Transcript The Nervous System - Marblehead High School

The Nervous System
35-2 & 35-3
What do YOU see here?
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By the end of this lesson
you should be able to:
1) Identify the functions of the nervous
system
2) Identify and label the parts of a neuron
3) Describe how a nerve impulse is
transmitted
Function of the Nervous
System:
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Body communication
Controls and coordinated body
functions
Responds to internal and external
stimuli
Carries messages (electrical impulses)
along nerve cell called neurons
Types of Neurons:
1) Sensory neurons - carry impulses
from the sense organs to the brain and
spinal cord
2) Motor neurons - carry impulses from
the brain and spinal cord to the
muscles and glands
3) Interneurons - connect sensor and
motor neurons
Structure of Neurons
Cell body - largest part containing the nucleus and cytoplasm
Dendrites - branched extensions that carry impulses to the
cell body
Axon - long fiber ending at the terminals that carries impulses
away from the cell body
Myelin sheath - protective membrane surrounding the axon
What do neurons do?
Transmit nerve impulses
Relies on electrical charges
Uses Sodium (Na+) and Potassium (K+)
to create a charge difference between
the nerve cell and its outer environment
The Neuron in Action
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1) Resting State of a
Neuron
Outside the nerve has a positive charge
Inside the nerve has a negative charge
Created because of Potassium (K+) flow
out of the nerve cell
2) Action Potential
An outside stimulus creates a nerve
impulse that travels down the axon
away from the cell body
The inside of the nerve cell is
temporarily more positive
Sodium (Na+) flow into the nerve cell
The impulse leaves through the terminal
and transmits to neighboring dendrites
3) Threshold
A nerve will only transmit an impulse if
the initial stimulus that is picked up at
the dendrites is larger than the
threshold
Threshold - the lowest level of stimulus
that will create an impulse
If the stimulus is weaker than threshold
NO IMPULSE will be produced
The Nerve Impulse
The Synapse
Occurs between one
axon and its
neighboring dendrite
Relies on chemical
called
neurotransmitters
Two Main Parts of the
Nervous System
1)
Central Nervous System (CNS) - the control
center of the body; consists of the brain and
spinal cord
1)
2)
3)
2)
Relays messages
Processes information
Analyzes information
Peripheral Nervous System (PNS) receives information from the environment
and sends commands from the CNS to the
organs and glands
Protection for the CNS
Skull and vertebrae
Meninges - three layers of connective
tissue that wrap the brain and spinal
cord
Cerebral spinal fluid - fluid
surrounding the brain and spinal cord
that acts as a shock absorber; also
allows fur nutrients and wastes to be
exchanges
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The Brain
Parts of the Brain
Cerebrum Largest part composed of folds and grooves that
make up the four major lobes
Responsible for voluntary activites
Site of learning, intelligence, and judgement
Left side (hemisphere) controls that right hand
side of your body and the reverse
Consists of two layers (1) outer cerebral cortex
made of only grey material and (2) inner white
matter
Parts of the Brain
Cerebellum Second largest brain region
Found at the back of the skull
Coordinates and balances muscle movement
Brain Stem Connects the brain to the spinal cord
Contains the pons and medulla oblongata
Responsible for blood pressure, heart rate,
breathing…
Parts of the Brain
The Hypothalamus
Recognizes hunger,
thirst, fatigue, anger, and
body temperature
Coordinates the nervous
and endocrine system
The thalamus Receives sensory
messages and sends
them to the cerebrum
Spinal Cord
Contains 31 nerves
that connect the
brain to the rest of
the body
Processes certain
reflexes - quick
automatic response
to a stimulus like
blinking
Peripheral Nervous System
1) Sensory Division - transmits impulses
from the sense organs to the CNS
2) Motor Division - transmits impulses
from the CNS to muscles or glands
composed of:
1) Somatic Nervous System
2) Autonomic Nervous System
The Somatic Nervous
System
Deals with activities that are under your
conscious control
Ex: Moving your pen, poking your
neighbor, and reflexes
Reflexes
Rapid responses
Follow a modified path
so they do not need to
go all the way to the
brain before a response
is produced
Reflex arc - includes a
sensory neuron, a
motor neuron, and an
effector (muscle)
The Autonomic Nervous
System
Responsible for
involuntary,
automatic
movements
1) Sympathetic
division
2) Parasympathetic
division
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The Autonomic Nervous
System
Deals with involuntary activities
Controls functions that are not under
your conscious control
Ex: heart rate, digestion, respiration
Sensory Receptors
1)
2)
3)
4)
5)
Pain receptors - respond to chemicals released
by damaged cells so the body can recognize
danger
Thermoreceptors - detect variations in
temperature
Mechanoreceptors - sensitive to touch, pressure,
sounds, motion and muscle stretching
Chemoreceptors - sensitive to chemical in the
external environment
Photoreceptors - sensitive to light
The Senses
35-4
Your Row will be assigned a sensory
function
Your group will work together in order
to write on the board:
1) The sense organs involved and their
functions
2) The basic method of operation - how
does it produce a response and what are
its major parts