Download The nervous system

Physiology, drugs and disease
The Nervous System
Fd(Sc) FISM
Year 2
08/01/2010
Objectives
• Describe the levels of organisation in the
nervous system.
• Outline the functions of the nervous
system.
• Describe the structure and function of a
nerve cell or neuron
• Research the affects of stimulants on the
nervous system
Introduction
• The nervous system is the master
controlling and communicating system of
the body.
• Cells of the nervous system communicate
through electrical signals, which are rapid,
specific and usually immediate.
The Nervous System
• Major division –
Central and Peripheral
• Central or CNS –
brain and spinal cord
• Peripheral –
nerves connecting CNS
to muscles and organs
Central Nervous System
Peripheral Nervous System
Peripheral Nervous System
• The nervous system has 3
overlapping functions
– motor
– sensory
– integration
• Motor -
– CNS to muscles and gland
• Sensory –
– sensory receptors to CNS.
Provides sensation or information
about internal and external
environment
• Integration –
– Processes and interprets sensory
information and coordinates
activities.
Brain
Spinal
Cord
Nerves
Autonomic System
• Two divisions:
– Sympathetic – fight or flight! Mobilises the body
during emergency situations.
– Parasympatheitic – Conserves energy. Nonemergency situations
• Control involuntary functions
–
–
–
–
–
heartbeat
blood pressure
respiration
perspiration
digestion
Sympathetic
CENTRAL NERVOUS SYSTEM SYMPATHETIC
Brain
• “ Fight or flight”
•
•
•
•
response
Release adrenaline
and noradrenaline
Increases heart rate
and blood pressure
Increases blood flow
to skeletal muscles
Inhibits digestive
functions
Dilates pupil
Stimulates salivation
Relaxes bronchi
Spinal
cord
Salivary
glands
Lungs
Accelerates heartbeat
Inhibits activity
Heart
Stomach
Pancreas
Stimulates glucose
Secretion of adrenaline,
nonadrenaline
Relaxes bladder
Sympathetic Stimulates ejaculation
ganglia
in male
Liver
Adrenal
gland
Kidney
Parasympathetic
CENTRAL NERVOUS SYSTEM PARASYMPATHETIC
• “ Rest and
response ”
system
• Calms body to
conserve and
maintain energy
• Lowers heartbeat,
breathing rate,
blood pressure
Brain
Contracts pupil
Stimulates salivation
Spinal
cord
Constricts bronchi
Slows heartbeat
Stimulates activity
Stimulates gallbladder
Gallbladder
Contracts bladder
Stimulates erection
of sex organs
Summary of autonomic
differences
Autonomic nervous system controls physiological arousal
Sympathetic
division (arousing)
Pupils dilate
Decreases
Parasympathetic
division (calming)
EYES
Pupils contract
SALVATION
Increases
Perspires
SKIN
Dries
Increases
RESPERATION
Decreases
Accelerates
HEART
Slows
Inhibits
DIGESTION
Activates
Secrete stress
hormones
ADRENAL
GLANDS
Decrease secretion
of stress hormones
• So how do the various divisions and
systems of the nervous system
communicate with each other and the rest
of the body?
• The next few slides illustrate the structural
units of the nervous system that enable
information to be conducted throughout
the body.
Nervous tissue
Nerve cells or neurons
• Structural units of the nervous
system. Specialised cells that
conduct messages in the form
of impulses to one part of the
body to another.
Dendrites
• Receive small electrical signals
from other neurons and
conducts electrical signals
(graded potentials) toward the
cell body.
The cell body (Grey matter)
• Collects the electrical signals
together. It decides whether to
respond with a large electrical
signal called the action
potential.
• The AXON (white matter) conducts
the action potential or electrical
impulse to the AXON TERMINAL.
• Any long axon is called a NERVE
FIBER. A bundle of fibres is called a
NERVE (myelinated)
• The axon terminals make contact
with other nerve cells, muscle cells
or glands.
• A SYNAPSE is the structure at the
point of contact of an axon and
another cell.
• An action potential travelling along
an axon is called a nerve impulse
and carries information as follows:
Transmission of a nerve impulse
• Electricity is the key!!! Neurons are
irritable and when stimulated by an
electrical impulse are conducted along the
length of the axon.
• The transmission is quite a complicated
procedure, but it basically involves
changing the inside of a cell’s axon from
being negatively charged to being
Transmission of a nerve impulse
continued….
• At rest, the inside of the nerve
axon is negatively charged and
the outside is positively
charged – RESTING
POTENTIAL.
• When the CNS stimulates a
nerve, the inside of an axon
becomes positively charged
and outside becomes
negatively charged. This
change is called the ACTION
POTENTIAL.
Transmission of a nerve impulse
continued…
• When the CNS stops stimulating the
nerve, the axon is negatively charged and
the outside is positively charged. This
process is called REPOLARISATION.
Reflex action
• Many of the body’s control systems belong
to the general category of stimulusresponse sequences known as reflexes.
• Reflexes are used to protect the body
without having to think about what is
happening.
A reflex is a rapid, predictable motor
response to a stimulus. It is unlearned and
Knee jerk reflex
• Knee jerk is a well known reflex.
• It is called a MONOSYNAPTIC reflex which means there is only one
synapse in the circuit.
• The movement it produces is very rapid as there is only one
synapse. (allows reflex actions to occur relatively quickly by
activating spinal motor neurons without the delay of routing signals
through the brain)
• The reflex works by tapping just below the knee, which makes the
quadriceps muscle stretch. This information travels to the spinal
cord. There, after one synapse in the spinal cord, the information is
sent back out to the muscle making it contract and the knee
extends.
Central Nervous System
Brain
• Consists of the brain and
spinal Cord.
• Brain
Processes and coordinates sensory
data and motor commands.
Higher functions – intelligence,
learning, memory and emotion.
• Spinal Cord
– Relays information to and from brain
– Performs less complex integration
Spinal
Cord
Brain has 2 Hemispheres
• Left & Right sides are
separate
• Corpus Callosum : major
pathway between
hemispheres
• Some functions are
lateralised
– language on left
– math, music on right
• Lateralisation is never 100%
Corpus Callosum
Right
Hemisphere
Left
Hemisphere
Each hemisphere is
divided into 4 lobes
Frontal –
Personality,
Emotion
Cognitive
Parietal –
Motor
Sensory
Occipital –
Vision
Temporal –
Speech
Memory
Contra-lateral Motor Control
• Movements controlled
•
•
•
by motor area
Right hemisphere
controls left side of
body
Left hemisphere
controls right side
Motor nerves cross
sides in spinal cord
Motor Cortex
Somatosensory Cortex
Temporal Lobe
 Contains primary
auditory cortex
• Inputs are auditory,
Auditory
Cortex
visual patterns
–
–
–
–
speech recognition
face recognition
word recognition
memory formation
Temporal
Lobe
Parietal Lobe
• Inputs from multiple
senses
 Outputs to Frontal lobe
 hand-eye coordination
 eye movements
 attention
Somatosensory
Parietal
Cortex
Lobe
Frontal Lobe
• Contains primary
motor cortex
• Important planning
and sequencing areas
Frontal
Lobe
Working
Broca’s
Memory
Area
Motor
Cortex
The Nervous System:
Summary
• Major structures of the
nervous
– CNS, Somatic, Autonomic
– Two hemispheres & 4 lobes
• Organization
– contralateral input & output
– primary sensory areas
– motor areas
• Localization of functions
Central Nervous System
Peripheral Nervous System
Research
• Research information on central nervous
system stimulants and sports
• Include amphetamines and cocaine
• Present your info to the rest of the group.