Download Endocrine and Nervous system

Endocrine and Nervous system
Hormones
 Hormones: chemical signaling molecules used in all
organisms to communicate.




Bacteria
Fungi
Plants
Animals
 Can be used to communicate over short distances or
long distances
 Can be used to communicate within an organism or
organism to organism

Pheromones
Pheromones
 Pheromones: Type of hormone that is released into
the external environment.
 Ex:




Ants path
Ant or bee releases it to cause an attack reaction in others
Sex hormones: ‘in heat’,
Menstrual synchrony (debated in humans, occurs in rats)
Figure 45.3
Endocrine System
 Endocrine system: regulates homeostasis by
releasing hormones into the blood stream.
 Are 8 endocrine glands in the human body that all
release different hormones.
Endocrine vs exocrine
 Endocrine: hormones directly to blood stream
 Exocrine: secret into ducts. Ex. Salivary glands,
sweat glands, mammary glands, pancreas (both
endocrine and exocrine)
Figure 45.9
Pineal gland
Hypothalamus
Figure 45.9a
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pancreas
Ovaries (female)
Testes (male)
Figure 45.9b
Figure 45.9c
Feedback loops
 Hormones can act in positive or negative feedback
loops.
Simple endocrine pathway
Example: secretin signaling
Figure 45.10
Low pH in
STIMULUS
duodenum
Negative feedback
Endocrine
cell
Hormone
Target
cells
RESPONSE
S cells of duodenum
Secretin (•)
Pancreatic cells
Bicarbonate release
Simple neuroendocrine pathway
STIMULUS
Example: oxytocin signaling
Figure 45.11Suckling
Sensory neuron
Positive feedback
Hypothalamus/
posterior pituitary
Neurosecretory
cell
Neurohormone
Target
cells
RESPONSE
Oxytocin (▪)
Smooth muscle in
mammary glands
Milk release
 Many endocrine glands work together to maintain
homeostasis.
 Ex. Metabolism: pituitary gland and thyroid gland.
STIMULUS
1 Thyroid hormone
levels drop.
Figure 45.16
Sensory
neuron
Negative feedback
Hypothalamus
Neurosecretory
cell
TRH
2 The hypothalamus secretes
TRH ●into the blood. Portal
vessels carry TRH to anterior
pituitary.
3 TRH causes anterior pituitary
to secrete TSH▲ .
TSH
Anterior
pituitary
Circulation
throughout
body via blood
Thyroid
gland
4 TSH stimulates endocrine
cells in thyroid gland to
secrete T3 and T4 ■.
Thyroid
hormone
6 Thyroid hormone blocks TRH
release and TSH release
preventing overproduction
of thyroid hormone.
Circulation
throughout
body via blood
RESPONSE
5 Thyroid hormone levels
return to normal range.
Figure 45.16a
STIMULUS
1 Thyroid hormone
levels drop.
End product of cascade,
thyroid hormone, creates
negative feedback.
Sensory
neuron
Hypothalamus
Neurosecretory
cell
TRH
2 The hypothalamus secretes
TRH ●into the blood. Portal
vessels carry TRH to anterior
pituitary.
3 TRH causes anterior pituitary
to secrete TSH ▲.
TSH
Anterior
pituitary
FigureTSH45.16b
TSH circulation
throughout
body via blood
Thyroid
gland
Thyroid
hormone
6 Thyroid hormone
blocks TRH release
and TSH release
preventing overproduction of
thyroid hormone.
4 TSH stimulates
endocrine cells in
thyroid gland to
secrete T3 and T4 ■.
Circulation
throughout
body via blood
RESPONSE
5 Thyroid hormone
levels return to
normal range.
Goiter
 Tropic: to bend or turn (also grow)
 Gonad: sex organs.
 Gonadotrophic hormone: hormone that causes
gonads to release hormones

Ex. Follicle-stimulating hormone FSH released by pituitary
gland stimulates ovaries to release estrogen or progesterone.
Pituitary giant
Dwarfism
Achondraplasia
Pituitary dwarfism
Melatonin
Nervous System
Neurons
A. Neuron: nerve cell
Transfer information within the body through electrical signals
(long distance) and hormones (short distance).
 Can be over a meter long

B. Glial cell (glia): specialized cells that support the
neuron, nourish and insulate the neuron.
Nerve cell structure
A. Dendrites: many branched extensions that
B.
C.
D.
E.
__________
information
receives
Nucleus
Cell body: where the __________
is located
transmits
Axon: only one long extension that __________
signals.
Synapse (synaptic terminal): located at the end of
the axon, chemical messengers travel from one
axon to another cell to send signals at the synaptic
terminal.
Neurotransmitters: hormones that send
messages from neurons
Figure 48.2
Dendrites
Nucleus
Cell
body
Presynaptic
cell
Synapse
Neurotransmitter
Axon
hillock
Axon
Synaptic
terminals
Postsynaptic cell
Synaptic
terminals
Nervous System
A. Central Nervous system (CNS):

Includes the brain and spinal cord
B. Peripheral nervous system (PNS):
 Includes all nerves throughout body
Types of Neurons
A. Sensory Neurons:
Located in the PNS
 Transmit information to brain regarding light, touch, smell, blood
pressure, muscle tension, etc.

B. Interneurons

Located in the brain, connect neurons in the brain
C. Motor neurons

Transmit signals to muscles cells, causing them to contract
Figure 48.4
Siphon
Sensory input
Integration
Sensor
Motor output
Proboscis
Processing center
Effector
Neuron Resting Potential
A. Membrane potential: potential energy, due to a
difference in charge from the inside to the outside of a
neuron.
Creates a voltage
 Similar concept to a battery, difference in charge creates a voltage, 9V,
12V, etc.
 Created by the movement of Na, K, in and out of the cell and the
impermeability of Cl ions inside the cell
 Only some ion channels (called leak channels) are always open to
allow the flow of Na and K in and out of the cell.
 Cell is negative inside, positive outside

B. Resting Potential: potential energy in a resting
neuron (not sending a signal) typically -60 t0 -90 mV
Figure 48.6
Key
Na concentration
Na+
K+
OUTSIDE OF CELL
is HIGH
Sodiumpotassium
pump
Potassium
channel
Sodium
channel
INSIDE OF CELL
K concentration is
HIGH
Sodium-Potassium Pump
A. Na-K Pump: pumps Na out of the cell and K into
the cell against concentration gradients to maintain
a high concentration gradient.
Sending a Nerve Impulse Vocabulary
A. Gated ion channels: ion channels that open or
close in response to a stimuli

The opening the ion gated channels allows the movement of ions,
which alters the membrane potential.
B. Depolarization: occurs when gated sodium
channels are opened, allowing sodium to quickly
move into a cell.
C. Voltage Gated ion channels: open channel due
to a change particular change in membrane
potential.
D. Threshold: particular value of membrane
potential that must be reached in order to send
signals down nerves and create an action potential
E. Action Potential: Massive change in membrane
potential
Once threshold is reached, many voltage gated ion channels open
at once, creating a massive change in the membrane potential,
leading to the action potential
 Have a constant magnitude and can travel long distances
 Can spread along axons
 Action potentials either occur fully or do not occur at all, so they
are ‘all or none’

Membrane potential (mV)
(c) Action potential
Strong depolarizing stimulus
triggered by a
Figure+50
48.10c
depolarization that
Action
reaches the threshold
potential
0
−50
Threshold
Resting
potential
−100
0 1 2 3 4 5 6
Time (msec)
Figure 48.9
Ions
Change in
membrane
potential
(voltage)
Ion
channel
Gate closed: No ions
flow across membrane.
Gate open: Ions flow
through channel.
Very Small Stimulus
A small stimulus causes a small change in the
membrane potential
2. Causes a small electrical current
3. But because the change in the membrane potential
did not reach the threshold, the signal decays with
time and distance from the source. Only travels a
short distance.
1.
48.10b
+50
Membrane potential (mV)
(b) Graded depolarizations
produced by two stimuli
Figure
that increase membrane
permeability to Na+
Stimulus
0
−50
−100
Threshold
Resting
potential
Depolarizations
0 1 2 3 4 5
Time (msec)
Larger stimulus
1.
2.
3.
4.
5.
6.
Stimulus causes a change in the membrane potential.
If stimulus is large enough, it causes the membrane
potential to reach the threshold
Once the membrane potential reaches the threshold,
voltage-gated ion channels open, resulting in a large influx
of Na ions into the neuron, creating a large change in the
membrane potential.
Causes the inside of the cell to become more positive
At a certain point, the voltage gated Na channels close,
potassium channels open, causing the inside to once again
become negative.
The sodium potassium pump moves the Na back out of the
cell and the K back into the cell, returning the cell back to
it’s beginning membrane potential.
Membrane potential (mV)
(c) Action potential
Strong depolarizing stimulus
triggered by a
Figure+50
48.10c
depolarization that
Action
reaches the threshold
potential
0
−50
Threshold
Resting
potential
−100
0 1 2 3 4 5 6
Time (msec)
Key
Figure 48.11
Na+
K+
3 Rising phase of the
action potential
4 Falling phase of the
action potential
Membrane potential
(mV)
+50
Action
potential
−50
2 Depolarization
OUTSIDE OF CELL
INSIDE OF CELL
Inactivation loop
1 Resting state
−100
Sodium
channel
3
0
2
4
Threshold
1
5
1
Resting potential
Time
Potassium
channel
5 Undershoot
Figure 48.11f
Membrane potential
(mV)
+50
Action
potential
3
0
−50
−100
2
4
Threshold
1
Resting potential
Time
5
1
Key
Figure 48.11a
Na+
K+
OUTSIDE OF CELL
INSIDE OF CELL
Inactivation loop
1 Resting state
Sodium
channel
Potassium
channel
 When an action potential is generated
2.
3.
4.
Voltage-gated Na+ channels open first and Na+
flows into the cell
During the rising phase, the threshold is crossed,
and the membrane potential increases
During the falling phase, voltage-gated Na+
channels become inactivated; voltage-gated K+
channels open, and K+ flows out of the cell
5.
During the undershoot, membrane permeability
to K+ is at first higher than at rest, then voltagegated K+ channels close and resting potential is
restored
Key
Figure 48.11e
Na+
K+
5 Undershoot
Figure 48.12-1
Axon
Action
potential
Na+
Plasma
membrane
Cytosol
Figure 48.12-2
Axon
Plasma
membrane
Action
potential
Cytosol
Na+
K+
Action
potential
Na+
K+
Figure 48.12-3
Axon
Plasma
membrane
Action
potential
Cytosol
Na+
K+
Action
potential
Na+
K+
K+
Action
potential
Na+
K+
Sending signals: speed
 Ultimately, the movement of Na into a cell and K out
of a cell is what sends signals down a neuron.
 Wider axons lead to faster transmission of impulses.
 To speed up transmission in narrow axons, some
neurons are covered in a myelin sheath
Myelin Sheath
A. Myelin Sheath: created by cells (glial cells) that
insulate the axon, speeding up transmission of a
nervous signal.
Oligodendrocytes: cells that cover the axon in the CNS
 Schwann cells: cells that cover the axon in PNS

B. Nodes of Ranvier: gaps in the myelin sheath that
allow for transmission of nervous impulse
Figure 48.14
Schwann cell
Depolarized region
(node of Ranvier)
Myelin
sheath
Cell body
Axon
Communication from nerve to other cells
 In most cases, electrical signals are NOT transmitted
from neurons to other cells.
Some cells do contain “gap junctions” that allow electrical current
to flow from one neuron to another
 Most synapses use chemical messengers (neurotransmitters) to
communicate from a neuron to another cell in synapses

Synapses: Vocabulary
A. Presynaptic neuron: neuron sending the signal.
B. Postsynaptic neuron: neuron receiving the
signal.
C. Synaptic cleft: gap that separates the presynaptic
neuron from the postsynaptic neuron.
D. Synaptic vesicle: membrane enclosed
compartments in the presynaptic neuron that
contain neurotransmitters
Presynaptic cell
1
Axon
Figure
48.16
Postsynaptic
cell
Synaptic vesicle
containing neurotransmitter
Synaptic
cleft
Postsynaptic
membrane
Presynaptic
membrane
3
K+
4
Ca2+ 2
Voltage-gated
Ca2+ channel
Ligand-gated
ion channels
Na+
Synapses: communicating with another cell
When the action potential reaches the synaptic
terminal, the plasma membrane depolarizes,
allowing Ca ions to enter.
2. The increase in the CA concentration causes
synaptic vesicles to fuse to the presynaptic cell’s cell
membrane allowing neurotransmitters to be
released into the synaptic cleft
3. The neurotransmitter travels and binds to the
postsynaptic cell’s receptor protein, leading to a
cellular response (such as opening the Na gated
channel).
1.
Presynaptic cell
1
Axon
Figure
48.16
Postsynaptic
cell
Synaptic vesicle
containing neurotransmitter
Synaptic
cleft
Postsynaptic
membrane
Presynaptic
membrane
3
K+
4
Ca2+ 2
Voltage-gated
Ca2+ channel
Ligand-gated
ion channels
Na+
Stopping communication
 The neurotransmitter can either be
Broken down by enzymes
 Retaken up by the presynaptic cell

Figure 48.18a
PRESYNAPTIC NEURON
Neurotransmitter
Neurotransmitter
receptor
Inactivating enzyme
POSTSYNAPTIC NEURON
(a) Enzymatic breakdown of neurotransmitter in the
synaptic cleft
Figure 48.18b
Neurotransmitter
Neurotransmitter
receptor
Neurotransmitter
transport
channel
(b) Reuptake of neurotransmitter by presynaptic neuron
Neurotransmitters
A. Acetylcholine:
Muscle stimulation, memory, learning
 Botox: blocks acetylcholine release

B. Dopamine:

Affect sleep, mood, attention, learning, emotions
C. Serotonin:
Affect sleep, mood, attention, learning, emotions
 Lack of serotonin may lead to depression
 Prozac: SSRI: selective serotonin reuptake inhibitors

D. Endorphins:
Produced during times of physical or emotional stress to reduce pain
and produce euphoria
 Ex: child birth, accidents, etc.
 Morphine and heroin: act like endorphins

Reflexes
Figure 49.7
Cell body of
sensory neuron in
dorsal root ganglion
Gray
matter
Quadriceps
muscle
Spinal cord
(cross section)
Hamstring
muscle
Key
Sensory neuron
Motor neuron
Interneuron
White
matter
Which combination of axon features should lead an axon to
communicate with downstream cells most slowly? An axon that is
1. long.
2. short.
3. wide.
4. thin.
5. myelinated.
6. nonmyelinated.
A.
1, 3, and 5
B.
1, 3, and 6
C.
1, 4, and 6
D. 2, 3, and 5
E.
2, 4, and 6
In a typical motor neuron, what is the correct sequence in which
these structures usually become involved in transmitting an
electrical current?
1. cell body
2. axon
3. axon hillock
4. dendrites
5. synaptic terminals
A.
4, 1, 3, 2, 5
B.
5, 4, 1, 3, 2
C.
4, 3, 1, 2, 5
D. 5, 4, 1, 2, 3
E.
4, 1, 2, 3, 5
Resting potential is mostly due to ion movements
through which two of the following?
1. Na+/K+ pumps
2. voltage-gated Na+ and K+ channels
3. ligand-gated Na+ and K+ channels
4. voltage-gated Ca2+ channels
5. Na+ and K+ leak channels
A. 1 and 2
B. 1 and 3
C. 1 and 5
D. 2 and 3
E. 4 and 5
Which is most directly involved in causing
neurotransmitter release from the presynaptic
membrane?
A. Na+
B. K+
C. Cl+
D. Ca2+
E. large, proteinaceous anions