Transcript Nervous System and Senses

Chapter 23
 Nervous System – rapid response to environmental
changes
 Via electrical signals
 Endocrine System – chemical signals via blood
 Hormones
 Response is slower, but changes can be more long term
 Nerve cell = Neuron
 Cells of all types are
irritable and can spread
an electrical signal
 Neurons are specialized
for role
 When a neuron is not
firing = resting potential
 -70mV (inside relative
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
to outside)
Ion concentrations across
membrane create it
K+ move freely down
concentration gradient
Na+ are blocked
Active transport – uses
energy
 Na+ K+ pump
 Once charge difference is
great enough, the +
charge outside the axon
stops the movement of
K+ out and maintains the
charge difference at the
balance point of -70mV
a) Concentration gradient of Na+ and the attractive
negative charge inside the axon membrane
b) Concentration of K+ and the number of proteins
inside the axon membrane
c) Concentration gradient of Na+ and the attractive
negative charge outside the axon membrane
d) Concentration of K+ and the sodium pump
 Myelin sheath speeds up conduction of electrical signal in
mammals
 Depolarization actually jumps from node to node
between the Schwann cells
 Saltatory transmission is 2-20X faster
 All or none response
 Variation in intensity of signal is then reflected in the
number of action potential spikes/ sec
Time
Time
a) Neurotransmitter receptors are in dendrite
membrane only.
b) Neurotransmitter receptors are in axon membrane
only.
c) Neurotransmitter is released from the cell body of
only one neuron.
d) Matching neurotransmitters are released by the
synaptic terminal of one neuron and dendrites of a
second neuron.
 Sensory Neuron –
picks up info from a
sensory receptor
 Interneuron – in CNS
 Integrates info
 Can be excitatory or
inhibitory
 Motor Neuron –
carries response to
muscle or gland
(effector)
a) Motor neuron, sensory neuron, interneuron
b) Interneuron, motor neuron, sensory neuron
Sensory neuron, interneuron, motor neuron
d) Sensory neuron, motor neuron, interneuron
c)
Presence of nerves –
absent in sponges
2. One-way synapse – 2
way in Cnidarian nerve
nets
3. Centralization –
concentration of nerves
along the midline and
the development of a
major region of
integration, the brain
4. Sheathing – insulation
+ speed
1.
 Central Nervous System
 Brain
 Spinal cord
 Peripheral Nervous
System
 Cranial nerves
 Ganglia outside CNS
 Spinal nerves
 Hindbrain –
 Medulla & Pons
 Passes info between
brain + nerve cord
 Vital centers for heart,
blood pressure,
respiration
 Cerebellum
 Coordinates equilibrium
and movement
 Midbrain –
 Sends sensory data to
higher brain centers
 Forebrain –
 Cerebrum
 Sensory + motor
association
 Intelligence + memory
 Written and spoken
language
 Thalamus –
 sensory integration
 Hypothalamus –
 Emotional states
 Temperature regulation
 CNS link to endocrine
system
Pituitary Gland – Master Gland
• Controlled by Hypothalamus
a) Synaptic terminals,
dendrite, myelin
sheathing
b) Neuron cell body,
dendrite, synaptic
sheathing
c) Dendrites, axon,
myelin sheathing
d) Axons, dendrite, cell
body
A
C
B
 All neurons that pass in and out of the CNS
 Includes:
 Sensory neurons
 Voluntary motor neurons
 Autonomic nervous system (involuntary motor ns)
 Parasympathetic system
 Sympathetic system
 Enteric division
a) The neuron’s action
potential
b) +40 mV
c) The neuron’s resting
potential
d) The movement of
sodium ions into the
neuron.
 Sensory receptors are our window on the world.
 Depending on the species, this window can be very
different
 Heat sensors linked to visual pathways in snakes
 Chemical landscape of army ants
 Transduction
 Sensory receptors register an external phenomenon
such as light, heat, movement, chemicals in water or air
and translate it into an electrical signal in the nervous
system.
 Detect chemicals in air or dissolved in liquid
 May be hair or pit with pores for letting chemicals in
air or liquid into a sensory receptor cell or directly to
the dendrite of a sensory neuron
 Sensory receptor cell/sensory neuron have specific
receptors for specific chemicals
 When chemical binds to the receptor , sodium channels
get leaky = receptor potential
 Strong enough signal causes an action potential in the
sensory neuron – communicating with CNS
 Wavelengths – visual spectrum, ultraviolet, infrared,
electrical fields
 Photoreceptors – eyes
 Take light and convert to an electrical signal
 We’ll cover these and other sensory systems in lab
 Many animals have a totally different perspective of
the world because they have different sensory
receptors
More about the
Skeletal System
will be covered
in lab.
 Endocrine glands
 Ductless
 Secrete hormone
 Hormone signal travels via
the circulatory system
 Target cells/organs have
receptors specific for
hormone
 Produces a response –
longer term change than NS
 Negative Feedback Loop
 Nerve cell – capable of
receiving and sending an
electrical signal down its
axon
 Also makes + secretes
hormone that then
travels in the blood
 Located in
hypothalamus of brain
 Can be exciters or inhibitors of a change
 Some regulate the internal environment
 Water balance or metabolic rates
 Some regulate changes in the body
 Sexual maturity and pregnancy
 Some regulate responses to gradual environmental
changes
 Migratory behavior, hibernation, rhythmic behavior
such as feeding, sleeping, etc.
 Hypothalamus –
 Region of brain
 Neurosecretory cells
 Nerve cells go to
posterior pituitary
 Hormone connection to
anterior pituitary
 Pituitary = Master Gland
of Endocrine System
Posterior Pituitary
Anterior Pituitary
 TRH – TSH releasing
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hormone
Thyroxine secreted by
Thyroid
Increases metabolic rate
of cells
Production of thyroxine
and its activity inhibit
production of TRH +TSH
Thyroxine secretion
slows
 Parathyroid –
embedded in
back of thyroid
 Parathyroid
hormone
(PTH)
stimulates
release of
Ca++ ions
from bone
 Adrenal cortex –(outer layer) – hormone action:
 Carbohydrate, protein and lipid metabolism
 Salt and water balance
 Adrenal medulla –(inner core) – hormone action:
 Regulates blood sugar, dilates blood vessels, heart rate
 Pancreas – insulin and glucagon – hormone action:
 Lowers blood sugar, stimulates glycogen storage
 Stimulates the breakdown of glycogen and increase of
blood sugar
 Gonads – testes and ovaries – hormone action:
 Sexual characteristics, pregnancy, egg + sperm
development
 Pineal Gland- melatonin – regulates circadian rhythms