Download Nervous Notes File

UNIT 7
Part 2:
The Nervous System
Key Questions
 1. How do humans coordinate all body systems?
 2. What parts make up the nervous system?
 3. What role do chemicals and receptors play in the nervous
system?
 4. How do organisms maintain dynamic equilibrium in response
to stimuli (internal/external)?
 5. How do feedback mechanisms allow organisms to maintain
homeostasis?
 6. What happens if there are disruptions in homeostasis
regarding the nervous system?

REMEMBER!!!!
REGULATION:
Control and coordination of
all life functions to maintain
homeostasis.
REMEMBER!!!
Human body systems that
involve regulation:
Nervous system and
Endocrine system
NERVOUS SYSTEM
 A. Definitions:
 Impulse: Electro-chemical signal
carried along a nerve pathway.
 Receptor: Specialized structures
that detect a stimulus.
RECEPTORS
Tons of
sensory
neurons
found
here!!!
NERVOUS SYSTEM
 Effector: Structure that carries out a
response (muscles, glands).
 Stimulus: Anything that causes a
response.
 Response: Reaction to a stimulus.
STIMULUS/RESPONSE
NERVOUS SYSTEM
 Neurotransmitter: Chemical
secreted to help to transmit
impulses from neuron to neuron.
 Reflex: A quick, automatic
response to a stimulus. Examples:
sneezing, blinking.
REFLEX
Normal reflex for
an infant when he
or she is startled or
feels like they are
falling. The infant
will have a
"startled" look and
the arms will fling
out sideways with
the palms up and
the thumbs flexed.
Videos
 Video – ‘Neuron’ – on server (part at beginning)
NOTES-NERVOUS SYSTEM
 A. Structures of the Nervous
System:
 Neurons: Basic unit of function
of the nervous system (See
Diagram).
NERVOUS SYSTEM
 Transmit
impulses in
one
direction.
NERVOUS SYSTEM
 PARTS OF THE NEURON: DCATS
 Dendrites: Connect stimuli to
neuron and generate
impulses toward cell body.
 Cell Body: Contains nucleus.
NERVOUSE SYSTEM
 Axon:
Fibers wrapped in myelin
sheath (fat coating)
Transmits impulses away
from cell body and toward
terminal branches.
NERVOUS SYSTEM
Terminal branches: End of
neuron. Secretes
neurotransmitters.
Dendrite on next nerve
catches the
neurotransmitter and
initiates signal again.
NERVOUS SYSTEM
Synapse: Space between
adjacent neurons.
Neuron Diagram
What is the ‘funny bone?!’
 http://kidshealth.org/kid/talk/qa/funny_bone.ht
ml
Video
 Video – ‘Nerve Impulses’ (server)
 Video – ‘Neurotransmitters’ (server)
NERVOUS SYSTEM
 FYI:
 You are born with all of the nerve cells you will ever
have. They cannot divide, so they cannot be
replaced.
 Many drugs affect the nervous system. Example:
Many pain killers block neurotransmitters from
being secreted, therefore the impulse is blocked,
and you do not feel pain.
NERVOUS SYSTEM
 3 Types of Neurons:
 1. Sensory Neuron –
 Transmits impulses from receptors to brain
and spinal cord.
 Sense organs = structures where sensory
neurons are concentrated (eyes, ears,
skin, tongue).
SENSORY NEURON
NERVOUS SYSTEM
 FYI: The Senses:
 The body has millions of neurons that respond to
stimuli in the environment.
 Sensory receptors react to specific stimuli by
sending impulses to other neurons and then to
the CNS.
 These receptors are concentrated in sense
organs, such as eyes, ears, nose, mouth, and
skin.
NERVOUS SYSTEM
 2. Interneurons –
 Relay messages from sensory
neurons to motor neurons.
 Found in brain and spinal cord.
NERVOUS SYSTEM
 3. Motor Neuron –
 Transmit impulses from central
nervous system (brain and spinal
cord) to effectors (muscles, glands).
NERVOUS SYSTEM

Define Reflex Arc: Pathway over
which nervous impulses travel.
 Step 1: A receptor receives a
stimulus (ex. hammer to knee).
 Step 2: Receptor initiates an
impulse in a sensory neuron, which
carries impulse to spinal cord.
NERVOUS SYSTEM
 Step 3: Within spinal cord, sensory
neuron synapses with interneuron,
which then synapses with motor
neuron.
 Step 4: Motor neuron transmits
impulse to effector (knee kicks out!)
REFLEX ARC
NERVOUS SYSTEM
C. Parts of the Human
Nervous System:
Nervous System
 The Nervous system is divided into
2 parts:
 The central nervous system
(CNS) and the
 Peripheral nervous system (PNS)
Nervous System
 All body functions are coordinated by
communication between the central
nervous system and the peripheral
nerves.
NERVOUS SYSTEM
1. Central Nervous
System (CNS):
 Brain and spinal
cord
 Relays messages,
processes and
analyzes
information
NERVOUS SYSTEM
 A. BRAIN
 Large mass of neurons located in cranial
cavity.
 Has about 100 billion neurons!
 Surrounded by skull for protection.
 Controls the other organ systems of the
body
 Activates muscles
 Causes secretion of chemicals (like
hormones)
NERVOUS SYSTEM
Brain continued:
 Allows organism to respond to changes
in the internal and external environment
 FYI: 1 of most active organs in body –
weighs only a few pounds, but receives
20% of blood pumped by heart!
 Made of 3 parts that control different
functions in body:
 Cerebrum, cerebellum, medulla
NERVOUS SYSTEM
 1. Cerebrum:
 Largest part of brain
 Center for VOLUNTARY (conscious)
activities.
 Where reasoning, memory, thinking
occur.
 Left hemisphere = (analytical, math
ability) and controls right side; right
hemisphere = (artistic ability,
creativity) and controls left side.
 Left vs. Right Brain Information!
 http://www.ucmas.ca/our-programs/whole-
brain-development/left-brain-vs-right-brain/
NERVOUS SYSTEM
 FYI: Cerebrum is made of 2 layers
 Outer layer
• Cerebral cortex – made of
gray matter
• Gray matter = densely
packed nerve cell bodies
 Inner layer
• Made of white matter =
bundles of axons with
myelin sheaths
NERVOUS SYSTEM
 2. Cerebellum:
 2nd largest region
 Controls and coordinates MOTOR
activities (movement) and aids in
maintaining balance.
NERVOUS SYSTEM
 3. Medulla:
 Also called brain stem.
 Connects brain with spinal cord.
 Controls involuntary activities
(breathing, heartbeat, blood
pressure, peristalsis)
 FYI: (Medulla oblongata = lower
portion of brain stem)
NERVOUS SYSTEM
Other parts of
brain:
Thalamus:
Relay station
for sensory
information
NERVOUS SYSTEM
 Hypothalamus:
 Below thalamus
 Controls coordination of
nervous and endocrine systems
 Helps to control body temp,
blood pressure, fatigue,
emotions, hunger.
NERVOUS SYSTEM
 B. Spinal Cord:
 Structure that is continuous with
brain.
 Protected by spinal column.
NERVOUS SYSTEM
 Spinal Cord continued:
 Coordinates activities between brain and
other structures.
 CENTER FOR REFLEX ACTIONS – PART OF
REFLEX ARC.
 Pathway from sensory neurons to
interneuron to motor neurons to
effector.
NERVOUS SYSTEM
 2. Peripheral Nervous System (PNS): All
nerves in body “around” or outside of the
CNS.
 Transmits impulses from sense organs to
central nervous system and from central
nervous system to muscles and glands.
NERVOUS SYSTEM
* The PNS is divided into 2
different systems based on
what each group of nerves
control.
NERVOUS SYSTEM
 A. Somatic Nervous System:
 Consists of nerves that coordinate
and control the VOLUNTARY
(conscious) muscles of the skeletal
system (we can control the actions
of these muscles)
NERVOUS SYSTEM
 B. Autonomic Nervous System:
 Consists of nerves that control
muscles which are
INVOLUNTARY (we cannot
control these muscles – they
are automatic)
NERVOUS SYSTEM
 Examples:
 Heartbeat = cardiac muscle
 Peristalsis = smooth muscle tissue
 Glands = secretion of hormones.
When Things Go Wrong:
Disruptions in Homeostasis
 1. Alzheimer’s Disease
 Brain disease that causes problems with memory,
thinking, and behavior
 Progressive disease – worsens over time
 No cure
http://www.alz.org/alzheimers_disease_4719.asp
When Things Go Wrong:
Disruptions in Homeostasis
 2. Stroke
 When blood supply to
part of the brain is
interrupted
 Deprives brain tissue of
food and oxygen
 Brain cells die
When Things Go Wrong:
Disruptions in Homeostasis
3. Spinal Cord Injuries
 Due to a blow or fracture that dislocates the
vertebrae
 Complete spinal cord injury – paralyzed below the
level of injury
When Things Go Wrong:
Disruptions in Homeostasis
 4. Multiple Sclerosis
 Disease in which body’s immune system eats away
at myelin sheath
 Interferes with body’s ability to communicate
 May result in deterioration of nerves
When Things Go Wrong:
Disruptions in Homeostasis
 5. Infections:
 Meningitis
 Disease caused by inflammation of the protective
membranes covering the brain and spinal cordmeninges.
 Usually caused by an infection of the fluid
surrounding the brain and spinal cord.
 May develop in response to a number of causes,
usually bacteria or viruses, but meningitis can also be
caused by physical injury, cancer or certain drugs.
When Things Go Wrong:
Disruptions in Homeostasis
 Botulism
 Botulinum toxin prduced by bacteria is one of most
poisonous substances known
 1 gram – if dispersed and ingested could kill 2
million people
 Toxin produces a protein that blocks release of
acetylcholine (neurotransmitter) that tells a muscle
to contract
When Things Go Wrong:
Disruptions in Homeostasis
 Botox –
 Drug that contains extremely dilute form of the
poison
 Has been found to be safe and effective for various
applications
http://www.botoxcosmetic.com/Why_Botox.aspx
Videos
 Video – ‘Synesthesia-The Man Who Tasted
Shapes’ (on server-12 min.)
 Video – Anancephaly (on server – 12 min.)
 Nova – ‘How the Brain Works’