chapter 25 nervous control (sec. 2 up to pg. 719 & sec 1)
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The Role of the Nervous System What is the nervous system? a system that lets an animal detect changes & respond to them nerve cells, sense organs, & brain Which characteristic of life is an organism’s nervous system related to? response to stimuli Most animals can quickly detect changes that take place around them. Usually, they respond quickly… A response is the action of an organisms b/c of a change in its environment. Receives information from internal and external stimuli – and responds (by sending a message to an “effector” such as a muscle or gland)TRANSCRIPT
Chapter 25 Nervous Control (sec. 2 up to pg. 719 & sec
1)
Unit 17: Nervous Control 300 Chapter 25 Nervous Control (sec. 2 up
to pg. 719 & sec 1) How do we see unity within diversity in
relation to nervous control??? How does form follow function???
Kids Health website The Role of the Nervous System
What is the nervous system? a system that lets an animal detect
changes & respond to them nerve cells, sense organs, &
brain Which characteristic of life is an organisms nervous system
related to? response to stimuli Most animals can quickly detect
changes that take place around them. Usually, they respond quickly
A response is the action of an organisms b/c of a change in its
environment. Receives information from internal and external
stimuli and responds (by sending a message to an effector such as a
muscle or gland) Comparison of Nervous Systems Nervous Systems in
Unicellular Organisms
Euglena light-sensitive structureunder the eye-spot allows Euglena
to swim in direction of light Paramecium can respond to obstacles
in path turns 30 & moves forward again Continues to do this
until passes object seems to be under chemical control Nervous
Systems in Invertebrates
radially symmetrical organisms have no center for nervous control
many short neurons form nerve net no definite nerve pathways ex.
Hydra bilaterally symmetric animals have a primitive control
center(s) (ganglia) & specific nerve pathways ex. Planaria
Nervous Systems in Invertebrates
other bilaterally symmetric animals also have brains ex. earthworm
cerebral ganglia (slightly larger ganglia) ex. grasshopper brain
divided into specialized areas protocerebrum deutocerebrum In
arthropods such as the grasshopper, the brain is divided into
specialized areas, including the protocerebrum (controlling vision)
and the deutocerebrum (processing antenna signals). The
stomatogastric system regulates digestion. Nervous System in Fish
lateral line system electrical sense
can sense the slightest movements (vibrations) in water electrical
sense Ampullae of Lorenzini sense changes in electrical fields
Being highly complex life forms fish need a brain and a nervous
system to control their body's actions. The nervous system of fish,
much like ours, is composed of a central co-ordinating brain, a
spinal cord and many, many nerves. The Brain:- Generally speaking
fish have small brains in relationship to their overall body
weight. Elasmobranchs (Sharks and Rays) in general have a slightly
larger brain for the same body mass as Teleosts (Bony Fish),
however there is great variety within the teleosts scientists have
learned something quite surprising about the Elephantnose Fish
(Gnathonemus petersii). The Human Nervous System
The human nervous system is divided into 2 main parts. 1. central
nervous system (CNS) Which includes the brain spinal cord 2.
peripheral nervous system (PNS) Which includes the body nerves CNS
serves as control centers info brought from PNS analyzed by means
of interneurons in the CNS & impulses then carried to
appropriate effectors by motor neurons of PNS PNS sensory &
motor neurons connected to the CNS.Info about animals environment
gathered by receptors & brought to CNS by sensory neurons What
do the 3 Major Parts of the Brain Do?
What does the cerebrum control? speech, reasoning, emotions What
does the cerebellum control? balance, posture, muscle tone What
does the medulla control? involuntary actions of internal organs
heart rate, breathing rate, peristalsis, etc. cerebrum cerebellum
medulla (brain stem) spinal cord Cerebrum sensory inputs are
interpreted & motor impulses started Cerebellum coordinates
impulses sent out from cerebrum think of Belle dancing w/ the
Beast. Her balance, posture, muscle tone. Medulla oblongata part of
brain stemcontrols involuntary actions of internal organs (heart
rate, breathing rate, peristalsis, etc.)Youd be dull & lifeless
w/o it Nerve Tissue What is a nerve? many neurons bundled
together
can be compared to a cable bundle of neurons Different types of
neurons differ in structure & direction in which they carry
impulses Can be compared to a cable made of many wires bunched
together, thick Nerve Tissue What is a neuron?
specialized cell that transmits nerve impulses (carries messages)
through the body can compare to electrical wires Different types of
neurons differ in structure & direction in which they carry
impulses the main part of the nervous system can be compared to
electrical wires: very thin & long, carry messages &have a
covering of insulation around them, usually connect 2 things
Different Types of Neurons
What are the types of neurons involved in the pathway of impulses?
sensory neurons transmit incoming impulses (stimuli) from receptors
to control center interneurons transfer impulses within control
centers (brain & spinal cord) from sensory to motor neurons
motor neurons transmit outgoing impulses from control center to
effectors muscles, glands, organs Sensory neuron Motor neuron
interneuron Stimulus response interpretation Different types of
neurons differ in structure & direction in which they carry
impulses Sensory neurons transmit incoming impulses from receptors
to a coordination center where impulses are interpreted
Interneuronstransfer impulses from sensory to motor neurons (in
brain & spinal cord) Motor neurons once incoming impulses have
been analyzed, the brain or spinal cord will send out a response
motor neurons transmit outgoing impulses to effectors Neuron
Structure What are the main parts of a neuron? dendrites
receive impulses & move them toward cell body cell body (soma)
nucleus, organelles, & cytoplasm axon carries impulses away
from cell body towards end branch terminal buttons/end branch of
axon help send impulses to next neuron or effector (muscle, organ,
gland) Terminal buttons/ end branch of axon dendrites highly
branched fibers; receive impulses from end brush of previous
neuron; conduct impulses toward cell body cell body portion of
neuron that most resembles other types of cells. contains nucleus
& cytoplasm Axon long, narrow portion of cell; carries impulses
away from cell body to terminal buttons/end branch of axon (end of
axon that divides into many filaments then impulse travels to
dendrites of next neuron or to effector). Axons are often covered
with myelin sheath (insulating lipid material). Myelin allows
impulse to move very rapidly consists of many layers made of
Schwann cells wrapping around & around axon Schwann cells help
provide nourishment to the axon & aids in axon
regeneration.Between Schwann cells the axon is left uncovered.These
bare areas are called nodes of Ranvier & help transport
impulses quickly b/c the impulse is able to move from node to node
instead of continuously along membrane. Neurons What are the other
parts of a neuron? myelin sheath
fatty layer surrounding axon that protects it & allows impulses
to move quickly Schwann cells make myelin Nodes of Ranvier sections
of axon between Schwann cells not covered in myelin sheath help
transport impulses quickly dendrites highly branched fibers;
receive impulses from end brush of previous neuron; conduct
impulses toward cell body cell body portion of neuron that most
resembles other types of cells. contains nucleus & cytoplasm
Axon long, narrow portion of cell; carries impulses away from cell
body to terminal buttons/end branch of axon (end of axon that
divides into many filaments then impulse travels to dendrites of
next neuron or to effector). Axons are often covered with myelin
sheath (insulating lipid material). Myelin allows impulse to move
very rapidly consists of many layers made of Schwann cells wrapping
around & around axon Schwann cells help provide nourishment to
the axon & aids in axon regeneration.Between Schwann cells the
axon is left uncovered.These bare areas are called nodes of Ranvier
& help transport impulses quickly b/c the impulse is able to
move from node to node instead of continuously along membrane.
Neurons dendrites terminal buttons (end branch) nucleus
cytoplasm
cell body (soma) axon terminal buttons (end branch) cytoplasm
nucleus dendrites myelin sheath nodes of Ranvier cell body (soma)
terminal buttons/ end branch of axon Dendrites Direction of impulse
dendrites highly branched fibers; receive impulses from end brush
of previous neuron; conduct impulses toward cell body cell body
portion of neuron that most resembles other types of cells.
contains nucleus & cytoplasm Axon long, narrow portion of cell;
carries impulses away from cell body to terminal buttons/end branch
of axon (end of axon that divides into many filaments then impulse
travels to dendrites of next neuron or to effector). Axons are
often covered with myelin sheath (insulating lipid material).
Myelin allows impulse to move very rapidly consists of many layers
made of Schwann cells wrapping around & around axon Schwann
cells help provide nourishment to the axon & aids in axon
regeneration.Between Schwann cells the axon is left uncovered.These
bare areas are called nodes of Ranvier & help transport
impulses quickly b/c the impulse is able to move from node to node
instead of continuously along membrane. The Pathway of
Impulses
How do messages movealong a neuron? an electrical charge movesalong
the axon in onedirection from dendrites tothe end branch of the
axon So, what are the 2 pathwaysthat messages follow? sensory
receptor to controlcenter (brain/spinal cord) control center to
effector(muscle, gland, organ) Virtually all nerve impulses must
travel through many neurons before reaching their targets Impulse
is transmitted in only one direction nerve impulse or action
potential results from changes in ion concentration inside/outside
neuron plasma membrane The Pathway of Impulses
Do neurons touch each other? No, they are separated by a synapse.
small, fluid-filled space between end branch of axon (of one
neuron) and dendrites of next neuron So, how do messages get from
one neuron to the next? neurotransmitters chemical messengers that
help move impulses across a synapse Virtually all nerve impulses
must travel through many neurons before reaching their targets
Impulse is transmitted in only one direction How do the PNS &
CNS Work Together in Nervous Response?
Detection of stimulus by sensory receptors Transmission of impulse
along sensory neuron (PNS) Interpretation & analysis of
impulses in control center (CNS) Transmission of impulse along
nerve (PNS) Response by effector muscle, gland, organ 1. Detection
of stimulus by sensory receptors (Ex. touch-sensitive cells in skin
or cells that form part of sense organ such as eye or ear) convert
input into electrical impulse Ex. Touch hot stove & sense too
much heat 2. Transmission of impulse along sensory neurons of PNS
to CNS Ex. signal sent along sensory neurons to brain or spinal
cord 3. Interpretation & analysis of impulses ininterneurons of
CNS (brain or spinal cord) Ex. brain or spinal cord interprets
& processes signal in interneuron 4. Transmissionof impulse
from CNS to motor neuron of PNS to effector (muscle, gland, organ)
5. Appropriate response by effectors (Muscles, glands, organs that
cause the actual response to the stimulus.) Ex. motor neurons
transmit outgoing impulses to the effectors which respond (pull
hand away from hot stove) The Senses Adaptations to sense a variety
of stimuli 5 major senses
receptor or sense organ sends impulses to particular parts of brain
where interpreted then act on info provided 5 major senses vision
hearing smell taste pain, pressure, heat, cold touch Reflexes What
is a reflex? involuntary/automatic response to stimuli
Involve CNS, but does NOT require conscious control or decision
making b/c determined by fixed pathways some through brain (ex.
blinking) others through spinal cord (ex. touch cactus &
respond) known as reflex arc interneuron 5 Steps of the Reflex Arc
& the Initial Response
Reflex Arc Animation Reflex Arc Animation 2 What are the 5 steps of
the reflex arc? Receptors detect stimulus & are activated
Sensory neuron transmits impulse towards spinal cord Impulse
crosses synapse to interneuron in spinal cord From spinal cord
impulse crosses synapse to motor neuron & leaves spinal cord
Impulse activates effectors (muscle, gland, organ) which responds
appropriately Does the reflex arc involve the brain? NO! Reflex arc
Receptors activated (ex. feel excess heat) Sensory neuron transmits
impulse towards spinal cord Impulse crosses synapse to interneuron
in spinal cord Impulse crosses synapse to motor neuron & leaves
spinal cord Impulse activates effectors which respond
appropriately(ex. pull hand away) Does NOT involve brain Takes a
fraction of a second Saying to help you remember Receive sensory
input; move effectively. 5 Steps of the Reflex Arc & the
Initial Response
2. Sensory neuron transmits impulse towards spinal cord 3. Impulse
crosses synapse into interneuron in spinal cord where interpreted
& analyzed 4. impulse crosses synapse from spinal cord motor
neuron & leaves spinal cord 1. Sensory receptor receives
stimulus & is activated. 5. Impulse received by effector (which
responds appropriately) interneuron Reflex arc Receptors activated
(ex. feel excess heat) Sensory neuron transmits impulse towards
spinal cord Impulse crosses synapse to interneuron in spinal cord
Impulse crosses synapse to motor neuron & leaves spinal cord
Impulse activates effectors which respond appropriately(ex. pull
hand away) Does NOT involve brain Takes a fraction of a second
Reflex Arc Reflex arc Receptors activated (ex. feel excess
heat)
Sensory neuron transmits impulse towards spinal cord Impulse
crosses synapse to interneuron in spinal cord Impulse crosses
synapse to motor neuron & leaves spinal cord Impulse activates
effectors which respond appropriately(ex. pull hand away) Does NOT
involve brain Takes a fraction of a second Interneuron =
association nerve The Secondary Response: After the Reflex
Arc
Since reflex actions (arcs) dont involve the brain, how does your
brain become aware? Some spinal cord interneurons that receive
sensory impulses connect with the brain This path is slower than
the reflex arc So, brain becomes aware of what has happened after
your body has already responded. secondary response You yell,
Ouch!. & grab thumb, foot, etc.