Download The Nervous System

The Nervous System
Page 897
The Nervous System
Page 897
• The nervous system is an intricate
communication network that coordinates and
controls functions throughout the body,
responding to internal and external stimuli.
• Tiny jolts of energy called impulses travel
along this network at tremendous speeds.
(243 mph recorded between cells.)
• Messages travel over many routes carrying
information about both the external
environment and the internal environment.
Receptors
Cells and organs that receive internal and
external messages are called receptors.
They receive information from the environment
(internal and external) and convey the
information to the nervous system.
They take on form of energy and convert it to
another.
Receptors are constructed to receive only
certain kinds of energy and they are categorized
based on this ability
Location of receptor
Stimulus
Photoreceptors
light
mechanoreceptors
Touch, pressure,
movement, sound
thermoreceptors
temperature
Chemical reaction on
Produces
chemoreceptors
Tastes, smells
nose
smell
All vertebrates
have a nervous
system (NS) made
up of a:
- central nervous
system (CNS) and
a
- peripheral
nervous system
(PNS).
Central nervous system (CNS)
1. CNS:
-
consists of nerves of
the brain and the
spinal cord.
-
coordination center for
ingoing and outgoing
information.
- covered by three
protective
membranes. These
membranes are called
the meninges. (With
meningitis, these
membranes swell.)
- Between the inner two
layers is a clear fluid
called cerebrospinal
fluid which:
- absorbs shock
- transfers nutrients to
the brain
- removes wastes from
the brain
CNS is composed of:
a. Brain:
- control center
- covered in grey matter (cerebral cortex)
which has many deep folds in it called
fissures. (These increase the surface area.)
- also protected by skull
The Brain
• There are over 100 billion nerve cells in the
brain.
b. Spinal cord:
- carries sensory messages from receptors
to the brain and motor messages from brain
to muscles and glands
- also controls many reflex responses
- white matter on the outside; grey on the
inside
- protected by the vertebrae
Developing
fetus at 10.5
mm
Parts of the brain
• Cerebrum (p. 902):
- largest and most
highly developed
- intelligence, thinking,
creativity, reasoning,
memory
- voluntary activities of
the body
Each hemisphere has 4
lobes:
• Frontal lobe: controls
speech, motor activities
(muscles), learning,
judgement, creativity,
organization
• Parietal lobe:
perception, recognition,
touch, temperature,
memory
• Occipital lobe: vision,
interpretation
• Temporal lobe: senses
(smell, taste, hearing),
some memory
THE CEREBRUM IS ALSO DIVIDED INTO TWO
LAYERS:
– Outer, cerebral cortex, gray matter which consists
of tightly packed nerve cell bodies.
– Inner, white matter, consists of bundles of axons
with myelin sheaths.
– Connects the cerebral cortex and the brain stem.
The cerebrum is divided
into two hemispheres
(right and left, each
controlling and
receiving information
from the opposite side
of the body)
• Corpus callosum:
- Connects the two hemispheres
• Brain stem:
- Consists of the medulla oblongata, pons Varolii,
and midbrain, that connect the spinal cord to the
cerebrum.
• Pons:
– Bridge between the
cerebrum and the
cerebellum
• Cerebellum:
– Balance, muscle tone
• Medulla Oblongata
– Involuntary muscles
– Internal organs
– Heart rate,
respiration
• Thalamus:
-Part of the brain that lies
just below the cerebrum
- Acts as a relay station by
receiving impulses from
most of the sensory
neurons and directing
these impulses to the part
of the brain where each
will be interpreted.
-Screens out less
significant stimuli
(prevents sensory
overload)
• Hypothalamus:
– Coordinates NS and endocrine system
The Spinal Cord
• Carries thousands of messages at once
• Main communication link between brain and
the rest of the body
• Thirty-one pairs of spinal nerves branch out
from the spinal cord
• Certain kinds of information, including some
reflexes, are processed directly in the spinal
cord.
Peripheral Nervous System
• Consists of all the nerves and associated cells
which are not part of the central nervous
system.
• Is divided into the:
– Sensory division: transmits impulses from sense
organs to the CNS
– Motor division: transmits impulses from the CNS
to the muscles or glands.
Somatic and Autonomic Nervous Systems
The motor division is further divided into the
somatic nervous system and the autonomic
nervous system.
• The somatic nervous system regulates
activities that are under conscious control (ie.
the movement of the skeletal muscles)
(Some somatic nerves are also involved with
reflexes and can act without conscious
control.)
Autonomic Nervous System
• The autonomic nervous system regulates
body activities that are automatic or
involuntary.
(ex. When a person is running, the autonomic
nervous system speeds up heart rate and
blood flow, stimulates sweat and adrenal
glands, and slows down the contractions of
the smooth muscles of the digestive system.)
The autonomic nervous system is
further subdivided into two parts:
–sympathetic nervous system
–parasympathetic nervous system
which have opposite effects on the
same organ system. (Think gas and brake
when driving a car.) (Sympathetic
nervous system speeds up heart rate;
parasympathetic slows it down.)
• http://www.youtube.com/watch?v=iNgGKSNiNw
Neurons
• The messages carried by the nervous system are
called impulses.
• Neurons (the cells that carry these impulses) are
classified into three types, depending on the
direction the nerve impulse travels along them:
– Sensory neurons - sense organs (receptors) carry
impulse to spinal cord and brain
– Motor neurons - carry impulse from brain and spinal
cord to muscles and glands
– Interneurons - connect sensory and motor neurons
and carry impulses between the two of them
The Nervous System - page 897
Draw and label the diagram of neuron from
the board.
• All organisms respond to changes in their
environment. A reaction to stimulus is called
a response.
• A stimulus is a change in the environment that
induces a response. These stimuli are
received through specialized receptors.
Receptors are classified in many different
ways. One way is by the type of stimulus
detected.
• Mechanoreceptors respond to physical force
such as pressure (touch or blood pressure) and
stretch.
• Photoreceptors respond to light.
• Thermoreceptors respond to temperature
changes.
• Chemoreceptors respond to dissolved chemicals
during sensations of taste and smell and to
changes in internal body chemistry such as
variations of O 2, CO 2, or H + in the blood.
• Nociceptors respond to a variety of stimuli
associated with tissue damage. The brain
interprets the pain.
• The parts of the body that respond to
messages coming from the brain and spinal
column (muscles, glands) are called effectors.