Download Nervous System - IB BiologyMr. Van Roekel Salem High School

Nervous System
IB Biology 2 – Van Roekel
BILL
• What is the part of your body that controls
everything else? What are the two parts of
this system?
• Nervous System
• Central Nervous System (brain and spinal
cord) and Peripheral nervous system (sensory
and motor neurons)
Bill
• What are the cells used in the nervous system called?
Name two different types of these cells.
• Neurons
• Sensory neurons send signals from sensory receptors
all over the body to the central nervous system.
• Motor neurons sends signals from the central nervous
system to effectors (muscles and glands) all over the
body.
• Interneurons (also called connector neurons or relay
neurons) are usually much smaller cells, with many
interconnections.
• 6.5.1 State that the nervous system consists
of the central nervous system (CNS) and
peripheral nerves, and is composed of cells
called neurons that can carry rapid electrical
impulses.
Central Nervous System
• Spinal cord receives
sensory information
from peripheral nervous
system and sends
message to brain.
• Spinal cord also receives
MOTOR signal from
brain and signals
peripheral nervous
system.
Somatic Nervous System
• Receives
external stimuli
and stimulates a
response
• Voluntary
control of
muscle
movement
Autonomic Nervous System
• Maintains homeostasis
• Responsible for
involuntary control
• Divided into two sub
levels:
– Sympathetic – “fight or
flight”
– Parasympathetic –
“rest and digest”
– Enteric – controls
digestive system
Autonomic Nervous System
• Sympathetic: takes
over in emergency
situations
• Parasympathetic:
important in
returning body to
normal state
Sympathetic Nervous System
• Excitatory response that uses noradrenaline as
neurotransmitter to release certain chemicals
(epinephrine, norepinephrine, adrenaline, etc)
• Associated with “Fight or Flight” response
• Increases heart rate
• Dilates bronchi to give more oxygen
• Dilates pupils
• Restricts blood flow from digestive system
Parasympathetic Nervous System
• Inhibitory response system with
neurotransmitter acetylcholine
• Associated with relaxed state of body
• Returns the system to normal by:
– Constricting pupils and bronchi
– Slowing heart rate
– Increasing blood flow to digestive system
Pathway of Pupil Reflex
• Pupils are controlled by parasympathetic
responses using acetylcholine
– Optic nerve receives message from retina in back of
eye (retina contains photoreceptors that respond to
stimulus of light)
– Optic nerve connects with pretectal nucleus of brain
stem
– Message is sent to and from brain using Oculomotor
nerve
– Oculomotor nerve synapses with ciliary ganglion
– Axons of ciliary ganglion stimulate circular muscle
contraction of iris causing it to contract
Review of Nervous System
• Central Nervous System: Consists of spinal
cord and brain, receives and interprets signals
from body
• Peripheral Nervous System: two parts
– Somatic System: takes info from sensory receptors
to CNS and sends back motor commands to
effectors
– Autonomic System: Involuntary and regulates
activities of glands, smooth muscle, and heart.
BILL - What are the different parts of
the nervous system?
• Central Nervous System (CNS) – consists of spinal cord
and brain, receives and interprets signals from body
• Peripheral Nervous System (PNS) – two parts
– Somatic System - takes info from sensory receptors to CNS
and sends back motor commands to effectors
– Autonomic - Involuntary and regulates activities of glands,
smooth muscle, and heart
• Sympathetic - Excitatory response that uses noradrenaline as
neurotransmitter to release certain chemicals, associated with
emergency situations.
• Parasympathetic - Inhibitory response system with
neurotransmitter acetylcholine, associated with relaxed state of
body
• 6.5.2 Draw and label a diagram of the
structure of a motor neuron.
Biology of the Neuron
Neuron
• Neuron, or nerve cell has:
– Cell body – contains nucleus and other organelles
– Dendrites – short, highly branched processes that receive
chemical messages from other cells
– Axon – carries nerve impulse away from the cell body.
Typically much longer than dendrites
Schwann Cells
• Schwann cells are individual cells that wrap
around the axon to provide insulation during
chemical signaling. A layer of Schwann cells
forms the Myelin Sheath.
Node of Ranvier
• Gaps between the layers of
Schwann Cells. They
function to allow gaps in
action potential so the
chemical signal essentially
“jumps” down the axon.
Synaptic Terminals
• Synaptic Terminals – relay signals from the
neuron to other cells, using neurotransmitters
• Synapse – site of contact between synaptic
terminal and its target cell.
3 Main Types of Neurons
• Sensory neurons have long axons and transmit nerve
impulses from sensory receptors all over the body to
the central nervous system.
• Motor neurons also have long axons and transmit
nerve impulses from the central nervous system to
effectors (muscles and glands) all over the body.
• Interneurons (also called connector neurons or relay
neurons) are usually much smaller cells, with many
interconnections.
• When many individual neurons group together, they
form a single structure called a nerve
Types of Nerves
• 2 categories of peripheral nerves
• Spinal Nerves:
– 31 pairs (left and right side) that emerge directly from
spinal cord.
– Mixed nerves – some sensory, some motor neurons
• Cranial Nerves
– 12 pairs emerge from area of brain called brain stem
– Ex: Optic nerve – carries visual information from
retina to the brain
• 6.5.3 State that nerve impulses are
conducted from receptors to the CNS by
sensory neurons, within the CNS by relay
neurons, and from the CNS to effectors by
motor neurons.
• http://www.youtube.com/watch?v=xRkPNwq
m0mM
Nerve Impulse
• Nerve impulses are conducted along the axon
of a neuron
• Result from the change in concentrations of
sodium and potassium ions across the
membrane of a neuron
• Consists of Resting potential and Action
Potential
Nerve Impulse Pathway
• Receptors transform stimulus into action
potential
• Chain of sensory neurons carry potential to CNS
• Interpretation occurs in appropriate area in brain
using relay neurons
• Response is carried back through CNS with relay
neurons and the PNS using motor neurons to
area of stimulus by neurons
• Potential is carried to effector cells, which
stimulate a response
The Reflex Arc
• 6.5.4 Define resting potential and action
potential (depolarization and repolarization)
Resting Potential
• Resting potential is the
electrical potential across the
plasma membrane when the
nerve is at rest and not
conducting a nerve impulse.
• Characterized by active
transport of Sodium ions
(NA+) out of axon cell, and
potassium ions (K+)
transported into cell
• Results in a net positive
charge outside the cell and a
net negative charge inside the
cell
Action Potential
• Action potential is the positive
electrochemical charge generated at the nerve
impulse. Normally this is seen as the 'marker'
of the nerve impulse position
• Depolarization is a change from the negative
resting potential to the positive action
potential inside the cell
– Sodium ions diffuse into the cell and potassium
ions diffuse out of the cell when NA+ & K+
channels open
• Re-polarization is the
change in the electrical
potential from the
positive action
potential back to the
negative resting
potential inside the cell.
• http://highered.mhedu
cation.com/sites/00724
95855/student_view0/c
hapter14/animation__t
he_nerve_impulse.html
BILL
• Draw a structure of a neuron from memory,
including the following: dendrites, cell body,
axon, schwann cells, myelin sheath, and
synaptic terminal
• Explain how a nerve impulse passes through a
neuron
Neuron
Nerve Impulse
• Resting potential creates electrical chemical gradient
between external and internal environments of
neuron, creating membrane potential
• Depolarization occurs, where Na and K ions diffuse in
and out of membrane channels, creating nerve impulse
• Self-propagating action, travels down the axon
• Repolarization occurs, where charges return to resting
state
• Refractory period- when neuron cannot carry another
nerve impulse until fully returned to resting potential
• 6.5.5 Explain how a nerve impulse passes
along a non-myelinated neuron.
http://www.youtube.com/watch?v=ifD1YG07fB
8
Resting and Action Potential in Na/K
ATPase
Resting Potential
• Chemical imbalance,
resulting from resting
potential, between inside
and outside of cell creates
electrical difference
(Membrane potential).
• Creates concentration
gradient of Na+ and K+
• Area of neuron is polarized
Action Potential
• Arrival of action potential from a
stimulus causes the Na+ to enter
neuron, creating a current/initial
impulse
• If current is strong enough,
protein channels (voltage-gated
channels) open Na+ diffuse in
and K+ out of axon via because
of concentration gradient
• Depolarization of adjacent
sections of neuron occurs.
Diffusion of ions results in
continuing nerve impulse, or
action potential
Repolarization
• Neurons send dozens of
actions potentials in a short
period of time
• After one impulse is sent out,
that area of axon cannot send
another impulse until ions are
restored to resting potential
• Time period for this to occur is
the refractory period
• To return to resting potential,
active transport pumps Na+
out of cell and K+ into cell
repolarization
Depolarization
Repolarization
• Resting Potential – electricity
generated before application
of a stimulus.
• Action Potential – brief
depolarization/repolarization
caused by application of
stimulus
• 6.5.6 Explain the principles of synaptic
transmission.
Synaptic Transmission
• Synapse: chemical communication between
neurons in a sensory pathways
– Occurs between terminal buttons of presynaptic
neurons and dendrites of postsynaptic neurons
• Uses neurotransmitters to pass information
between neurons
– Neurotransmitters are any chemicals used for
synaptic transmission i.e. acetylcholine
Synaptic Transmission
• Sensory Pathways are unidirectional and
consists of many patterns
Mechanism of Synaptic Transmission
• Action potential reaches the terminal buttons on a Neuron.
1. Calcium Ions (Ca2+) diffuse into terminal buttons of presynaptic
neuron
2. Vesicles containing neurotransmitter fuse w/ plasma membrane and
release neurotransmitter
3. Neurotransmitter diffuses across synaptic gap
4. Neurotransmitter binds w/ receptor protein on postsynaptic neuron
5. Binding results in channel opening and Na+ diffusing through channel
6. Initiates action potential in postsynaptic neruon
7. Neurotransmitter is degraded by enzymes and released from
receptor protein
8. Ion channel closes to sodium ions
9. Neurotransmitter diffuse back across synaptic gap to terminal button
in presynaptic neuron
http://www.youtube.com/watch?v=LT3VKAr4roo
Studying our Senses
•
•
•
•
•
Read 1st page of Studying our senses lab
Partner up (2 per group)
Each group must wipe down lab table using Lysol
Each person must use Germ-X
Each partner needs their own spoon and 6 different
jellybeans held in a Dixie cup
• ONLY TIME YOU WILL BE ALLOWED TO EAT
• Other interesting visuals
– http://blogs.discovermagazine.com/badastronomy/2009/0
6/24/the-blue-and-the-green/
– http://www.psy.ritsumei.ac.jp/~akitaoka/cataloge.html
Bill
• Explain how a nerve impulse passes through a neuron
• Resting potential creates electrical chemical gradient
between external and internal environments of neuron,
creating membrane potential
• Depolarization occurs, where Na and K ions diffuse in and
out of membrane channels, creating nerve impulse
• Self-propagating action, travels down the axon
• Repolarization occurs, where charges return to resting state
• Refractory period- when neuron cannot carry another
nerve impulse until fully returned to resting potential
Resting Potential
• Chemical imbalance,
resulting from resting
potential, between inside
and outside of cell creates
electrical difference
(Membrane potential).
• Creates concentration
gradient of Na+ and K+
• Area of neuron is polarized
Action Potential
• Arrival of action potential from a
stimulus causes the Na+ to enter
neuron, creating a current/initial
impulse
• If current is strong enough,
protein channels (voltage-gated
channels) open Na+ diffuse in
and K+ out of axon via because
of concentration gradient
• Depolarization of adjacent
sections of neuron occurs.
Diffusion of ions results in
continuing nerve impulse, or
action potential
Repolarization
• Neurons send dozens of
actions potentials in a short
period of time
• After one impulse is sent out,
that area of axon cannot send
another impulse until ions are
restored to resting potential
• Time period for this to occur is
the refractory period
• To return to resting potential,
active transport pumps Na+
out of cell and K+ into cell
repolarization
The BRAIN
Parts of the Brain
• Cerebral Hemispheres: integrating center for high complex
functions such as learning, memory, and emotions
• Hypothalamus: maintains homeostasis, coordinates nervous
and endocrine systems, secretes hormones of posterior
pituitary, and releases regulating factors in anterior pituitary
• Cerebellum: “little brain” coordinates unconscious functions
such as movement and balance
• Medulla: controls automatic and homeostatic activities, such
as swallowing, digestion, vomiting, breathing, and heart rate
• Pituitary Gland: stores and releases hormones produced by
hypothalamus and anterior pituitary, secretes regulating
hormones
Left & Right Hemispheres
• Left Hemisphere: contains areas important for
all forms of communication. If damaged,
person may have difficulty speaking or
complicated movements with hands
• Right Hemisphere: Specializes in receiving and
analyzing information which comes from our
senses. Damage results in difficulty identifying
faces and locating an object correctly in space