Transcript Nervous system 1 - Spanish Point Biology

Human Responses
Nervous system
Endocrine System (hormones)
The Nervous System
 Organisms must be aware of what is happening around them,
as this affects their survival chances.
 Co-ordination of an organism’s activities is
carried out by the nervous system and the
endocrine system.
 A nervous system allows an organism to
detect and respond to stimuli in its internal
or external environment.
 A stimulus is any change in your
internal or external environment
e.g. a flash of light, a noise, increase
in blood concentration.
2
 The nervous system relies on
electrical signals, carried by
specialised cells [neurons], and
is involved in fast responses.
 The central nervous system (CNS)
is your brain and spinal cord.
 The brain keeps a check on
internal organs and activities,
such as the level of carbon
dioxide or water in the blood.
 The peripheral nervous system
(PNS) is the nerves branching out
from the CNS to all parts of the
body.
3
NS ----- Co-ordination & Response
 A stimulus is any change in your .....environment….
 A receptor is a nerve cell that detects the stimulus
 A neuron is a specialised cell that carries electrical messages
(impulses) around the body.
 An impulse is an electrical message that is carried along a
4
neuron.
The Brain
 The brain is composed of over 100 billion neurons, each
receiving messages simultaneously from thousands of other
neurons.
 The brain is
protected by the skull
bones, meninges
(three membranes)
and cerebrospinal
fluid.
5
 The cerebrum is our
conscious brain, with
different parts having
different jobs to do –
memory, emotion,
hypothalamus
learning….
 The hypothalmus
controls
homeostasis –
osmoregulation
cerebrum
pituitary
 The pituitary ‘[master] gland secretes hormones that stimulate
other glands to release their hormones.
6
7
 The cerebellum = co-ordination, movement, balance
Medulla
oblongata
cerebellum
 The medulla oblongata co-ordinates involuntary,
automatic processes — such as breathing, heartbeat.
8
Conscious actions
A conscious action is one where the brain makes a considered response. Here’s
what happens:
4) The brain
decides to move
away the hand
3) Here another sensory neuron
carries the signal to the brain
5) This impulse is
sent by MOTOR
NEURONS to the
hand muscles (the
effectors) via the
spinal chord…
2) The impulse is carried by
SENSORY NEURONS to the
spinal chord
1) Receptors in
your skin detect a
stimulus
6) Which then
moves the hand
away
Stimulus
Receptor
Motor Neuron
Sensory Neuron
Effector
Coordinator
Response
9
There are three types of Neuron :
 Sensory neuron –carries
messages from the sense
organ to the central nervous
system (CNS).
 Interneuron –connects
sensory and motor neurons
and so carries messages
within the CNS.
 Motor neuron –carries
impulses from the CNS to
muscles and glands.
10
11
12
Where are
the
synaptic
knobs?
Cell body
location
within CNS
or not
Direction
of impulse
Where are
the
synaptic
knobs?
13
Differences between Motor and Sensory Neuron
1. Direction of impulse – to or away from CNS
2. Position of cell body – at start or along length
3. Location of cell body - within CNS or outside CNS
in ganglion
14
Neuron structure
 The cell body contains the nucleus and other organelles and
produces neurotransmitter chemicals.
 A dendrite is a short fibre that receives impulse (information)
and carries it towards the cell body.
 The axon is a very long fibre that conducts impulses away
from the cell body.
15
 Many Schwann cells wrap their fatty cell membranes
around an axon, forming a myelin sheath.
 The myelin sheath insulates the neuron from electrical
impulses flowing in other neurons.
 Synaptic Knobs (containing neurotransmitter vesicles) –
produce, store and release neurotransmitter chemicals e.g
16
acetylcholine
LEARNING CHECK
• Name the 5 main parts of the brain and one
function of each.
• How is the brain protected?
• What is meant by “conscious action”?
• What does the term “involuntary” mean?
• Distinguish between the cerebrum and the
cerebellum.
17