Unit 5. The Interaction Function: The Nervous and Endocrine System

INDEX

1. The interaction function
2. Coordination systems: Nervous system and endocrine system:
teamwork
3. The nervous system
a. The neuron and synapse
b. Anatomy and physiology of the nervous system
c. Reflex action and voluntary action
4. Diseases of the nervous system
5. The endocrine system

BEFORE STARTING ...

. Do you recognize the picture on the right? What is it? What is it its function?
.What happens to a person in a wheelchair? Why can't they walk?
Why is the heartbeat faster when we start running?
·If we touch a pot of boiling water with our hand, how do we react? Does the same thing
happen if we are thirsty and see a glass on the table?
.How do we feel when we parachute for the first time? Do we feel the same if we are on the
couch watching a comedy? Why?

THE INTERACTION FUNCTION

The interaction function allows living
beings to capture stimuli from the internal
and external environments, respond to
them and adapt to changes. It involves
three processes:
STIMULI DETECTION
INFORMATION PROCESSING
AND RESPONSE
ELABORATION
RESPONSE EXECUTION

COORDINATION SYSTEMS

STIMULI

Changes produced in the external
environment or in the body: sound,
pain, light, temperature, pressures
changes, taste ...
Specialised cells that perceive stimuli and
send information to the coordination
systems.
EFFECTOR
ORGANS
MUSCLES
GLANDS
They execute the response sent by coordination systems:
Muscles: movement (contraction and relaxation)
Glands: They produce and release substances (saliva, digestive juices ... )
SENSORY RECEPTORS

NERVOUS SYSTEM

ENDOCRINE SYSTEM

They process information sent
by senses and elaborate a
response to send to effector
organs.STIMULI DETECTION

ACTIVITIES

Exercise 1: Analyze Situations

Exercise1. Analyze the following situations and indicate:
A) The stimuli that are perceived
B) The receptor that captures the stimuli
C) How the information is processed
D) The response produced by the body
INFORMATION PROCESSING
AND RESPONSE
ELABORATION
I
RESPONSE EXECUTION
1
2
3
You pass by a pastry shop
and see a cake. You buy a
piece and eat it.
You walk through a field
and approach a flower with
a pleasant fragrance
You pricked a finger while
sewing with a needle, and
some bees are trying to sting
you
ne

COORDINATION SYSTEMS: TEAMWORK

Coordination in mammals is carried out by two systems: The nervous system and
the endocrine system
Information
from the
receptors
Response
execution
NERVOUS SYSTEM
ENDOCRINE SYSTEM
Information processing

ACTIVITIES

Exercise 2: Comparing Nervous and Endocrine Responses

You go to the zoo, and a lion
comes out of the cage and is
about to run towards you
Exercise 2. We compare the coordinated responses of the nervous
and endocrine systems. Analyze the situation and compare the
responses elaborated by both coordination systems. Read the notes
and complete the chart.
Receptors in your eyes perceive the lion, and
those in the ears perceive its roar. They send
the information through nerves to the
central nervous system, composed of organs
such as the brain or spinal cord, which send
responses to the effector organs. Signals are
very fast, in the form of nervous or
electrical impulses, allowing to coordinate
quick and brief responses: the contraction
and relaxation of leg muscles: it causes
movements: you escape running and find
safety by climbing a tree.

ACTIVITIES

Exercise 2: Endocrine System Response to Adversity

You go to the zoo, and a lion
comes out of the cage and is
about to run towards you
Exercise 2. We compare the coordinated responses of the nervous
and endocrine systems. Analyze the situation and compare the
responses elaborated by both coordination systems. Read the notes
and complete the chart.
Hypophysis (pituitary
gland)
ACTH hormone
O
Adrenal gland
Adrenalin
In the face of adversity, the endocrine system also
generates a response. In this case, the pituitary gland
produces a hormone that is released into the blood. The
hormone travels slowly through the blood until it reaches
the target cells: the adrenal gland (located on top of
both kidneys). When activated, this gland produces
adrenaline (stress hormone). It is released into the blood,
travels slowly through the body, and acts on the target
organs: it increases the heart and breathing (respiratory)
rates, it increases blood pressure, it stimulates glucose
release into the bloodstream (liver), it enhances efficiency
of muscle contraction, it dilates the pupil (alertness), it
increases sweat production ... This stress situation is very
intense and lasts more; you don't calm down quickly.

ACTIVITIES

Exercise 2: Comparing Nervous and Endocrine Systems Characteristics

You go to the zoo, and a lion
comes out of the cage and is
about to run towards you
Exercise 2. We compare the coordinated responses of the nervous
and endocrine systems. Analyze the situation and compare the
responses elaborated by both coordination systems. Read the notes
and complete the chart.
Characteristics
Nervous system
Endocrine System
What is the signal that is
transmitted?
Through where are the
signals transmitted?
Speed of the response
Duration of the response
Level of specificity: high or
low? Does the response
involve many or few
effectors?
+
VS

THE NERVOUS SYSTEM: A) THE NEURON AND SYNAPSE

.The anatomical and functional unit of the nervous system is a highly specialised cell:, the neuron.
Although the neuron has the same structure as other eukaryotic cells (cell membrane, cytoplasm
with all the organelles and nucleus), its shape is elongated and has numerous ramifications. It
is specialised in performing a specific function: para realizar unha función moi especial:
transmitting the nervous (electrical) impulse.
Myelin sheaths. They
act as an insulator so
that the electrical signal
is not interfered with.
They are formed by
Schwann cells.
Nodes of Ranvier. They
are the gaps between
myelin segments.
Cytoplasm
. Cell membrane
Dendrites. They are thin and
numerous projections of the
cytoplasm.
Synaptic buttons: small
swellings that are found at
the terminal ends of axons,
where neurotransmitters
are stored in vesicles.
· Nucleus
Axon. They are elongated projections of
the cytoplasm with numerous and thin
branches at their ends.
Neuronal body or soma: it contains
most of the cytoplasm and cellular
organelles.
Nucleus
Cytoplasm
0
Axon
*
Schwann cells. They
cover the axons of
the neurons and
insulate them
electrically. They
contain myelin.

THE NEURON AND SYNAPSE

.The nervous impulse propagates only in one direction: it
enters through the dendrites, runs through the cell body
and the axon, until it reaches the synaptic buttons on the
opposite end.
The speed of propagation of nerve impulses is higher if
the axon is surrounded by special cells called Schwann
cells, which form myelin sheaths.
. When the electrical wave reaches the synaptic buttons on
the axon end, SYNAPSE takes place: neurotransmitters are
released into the synaptic cleft, and they bind to the
postsynaptic neuron through specific receptors on its cell
membrane, producing the electrical wave on its dendrites.
The electrical signals
of the nerve impulse
are transmitted at a
rate of 100 m/s
dendrite
axon
nucleus
To the next
neuron
Direction of
impulse
myelin sheaths
Stimulus
Presynaptic
neuron
Propagation
of the
electrical
wave
2
Synaptic
cleft
3
Postsynaptic
neuron
4
Neurotransmitters
Neurotransmitter
receptor
SYNAPSE
Video nervous impulse
Video synapse
Neurons under microscope
Reel: neuronal connections and learning

1
Synaptic
buttonneuron
axon
axon
nerve
nerve
Nerve
fibre
Axons of several neurons bundle up together to
form nerve fibres.
Nerve fibres grouped in nerves.
axon
axon
In nervous tissue, neurons are
accompanied by glial cells.
They have a defensive function,
provide nutrients and give
support to the neurons.
*
*
*
*
*

dendrites
r
soma

ACTIVITIES

Exercise 3: Neuron Analysis and Functioning

Exercise 3. Analyze the neuron and its functioning
A) Identify in these pictures the parts of a neuron and the elements of a synapse.
A
G
F
B
E
G
A
F
B
E
C
D
D
C

ACTIVIDADES

Exercise 3: Electrical Impulse Direction and Speed

Exercise 3. Analyze the neuron and its functioning.
B) Draw the direction of the electrical impulse on the neurons. From where to where
does it go? In which of the neurons does the nerve impulse travel faster? Why?
FREEP !!
FREEPIK
FREE
FREEPIK

ACTIVITIES

Exercise 4: Analgesics and Pain Relief

Synaptic
cleft
Postsynaptic neuron
Exercise 4. There are medications that we
take
to relieve pain: analgesics or
painkillers. To prevent pain, they can work in
different ways:
A) Drugs that prevent neurotransmitters from
releasing into the synaptic space.
B) Drugs that block neurotransmitter
receptors in the postsynaptic neuron, so
neurotransmitters cannot bind to them.
Using the image, explain how they work and
why we don't feel pain if we take them.
Presynaptic neuron
electrical
wave
electrical
wave
Synaptic button
Neurotransmitter
Neurotransmitter
receptor
3

TYPES OF NEURONS

According to their function, neurons are classified as:
.Sensory neurons. They transmit the stimuli from the sensory organs to the nervous system. They are
located in organs called nerves.
.Association neurons or interneuron: They connect sensory and motor neurons.
integrated into the nerve centres (spinal cord and brain).
Motor neurons: They transmit the responses from the nervous system to the effector organs. They
are also found in nerves.
Stimulus
on a sensory
organ
Interneuron
7
Sensory neuron
Response
(for example, pain
flexion reflex)
Motor neuron

ACTIVITIES

Exercise 5: Identifying Neuron Types and Impulse Order

Exercise 5. Identify the types of neurons in the following neural network.
A) What order does the electrical impulse follow from the perception of the stimulus to the
execution of the response?
B) How many synapses are represented?
1
O
J
Stimulus
Receptor
2
Brain
3
Response
Effector

ANATOMY AND PHYSIOLOGY OF THE NERVOUS SYSTEM

Our nervous system is divided into 2 large
anatomical and functional regions:
Central nervous system (CNS): It is made up of
the brain and the spinal cord; these organs are
the higher nerve centres.
Peripheral nervous system (PNS): It is made up
of nerves that put the central nervous system in
contact with the receptor (they perceive stimuli)
and effector (they execute the response) organs.
Central
Nervous
System
Peripheral
Nervous
System