part 1 biology 12. an integral part of your body’s communication system. it plays an important...
TRANSCRIPT
THE NERVOUS SYSTEM An integral part of
your body’s communication system.
It plays an important role in the smooth functioning of the body.
The nervous system is a complex network of cells which are specialized in function.
HOMEOSTASIS & NERVOUS SYSTEM The Nervous System allows the body to
respond to changes in the internal and external environments.
Communication comes in the form of electrochemical messages relayed to and from the brain, or a series of chemical messengers carried in the blood.
Through a series of adjustments, all systems of the body are regulated to maintain the internal environment within safe limits (homeostasis).
TWO DIVISIONS... The nervous system has
two main divisions: Central Nervous System
(CNS)Peripheral Nervous
System (PNS)
CENTRAL NERVOUS SYSTEM Consists of the nerves of the brain and
spinal cord.Brain is known as the “cerebrum”
Acts as a coordinating centre for incoming and outgoing information.
THE CEREBRUM (BRAIN)
The brain consists of millions of nerve cells that cluster together and interact with each other through the process of neurotransmission.
It controls most of the bodily functions like movements, thoughts, speech, sensations and memory.
THE SPINAL CORD The spinal cord is a
continuation of the brain and is surrounded by the vertebral bodies that form the spinal column.
The spinal cord is divided into four main segments; reach transferring signals to different parts of the body.
VIDEO CLIP http://
www.youtube.com/watch?v=vGxho71tScM&NR=1
PERIPHERAL NERVOUS SYSTEM
Consists of nerves that carry information between the organs of the body and the central nervous system.
It can be further divided into:Somatic nervous systemAutonomic nervous system
NERVE CELLS
Information about your body is continuously relayed to your brain for processing and storage.
The cells that transfer these messages to the brain and around the body are nerve cells.
CELLS OF THE NERVOUS SYSTEM Nerve cells gather & transmits electro-
chemical signals.
DID YOU KNOW???? Neurons cannot be repaired Some last a life time Approximately 1000 die each day!!!
NEURON NOTABLES Average number of neurons in the
human brain = 100 billion Nerve “highway” in the human body
contains 100 billion neurons 1000 impluses/sec
TYPES OF NEURONS SENSORY
Carries signals FROM periphery (outside) TO central nervous system for processing
Information FROM environmentNOTE: detect external stimuli (light, sound,
touch, heat, smell, & taste) or internal conditions (blood pressure, CO2 level & muscle tension)
TYPES OF NEURONS MOTOR
Carries signals FROM central nervous system TO body part (e.g. muscles, skin, glands)
Respond to sensory neuronsResponsible for movement
TYPES OF NEURONS INTERNEURONS
Connects sensory or motor neurons to central nervous system
Carries messages in-between neuronsMajority of neurons in the brain are
interneurons
PARTS OF A NEURON Cell Body
Contains all organelles, including a nucleus
DendritesProjections off cell bodiesMake connections with other cells
PARTS OF A NEURON Axon
Long cable like projection off cell bodySends messages (nerve impulses)
Myelin SheathFatty protein that covers/insulates most
nerves Increases speed of transmission Formed by Schwann cells
Nodes of RanvierExposed axon between myelin sheath
PARTS OF A NEURON Synaptic knob
End of axon branches Comes near dendrites of adjacent neuronsPasses messages across synapse (the space
between neurons)
Figure 27.3
Signal direction Dendrites
Cell body
Nucleus
AxonSupportin
g cell
Myelin sheath
Signal pathway
Nodes of Ranvier
Synaptic knobs
Cell body
DIRECTION OF MESSAGE Moves in only one direction From dendrite to cell body, axon, then
synaptic knob
Figure 27.3
Signal direction Dendrites
Cell body
Nucleus
AxonSupportin
g cell
Myelin sheath
Signal pathway
Nodes of Ranvier
Synaptic knobs
Cell body
NEURONS IN ACTION The three interconnected functions of
the nervous system are carried out by the three types of neurons
Sensory input
Sensory receptor
Sensory neuron
Integration
Interneuron
Brain and spinal cord
Central nervous system (CNS)
Motor neuron
Motor output
Peripheral nervous system
(PNS)
Effector
Figure 27.2
LET’S REVIEW: VIDEO CLIPS Nervous System explained Nervous System Rap How Neurons Work
TASK Draw a large motor neuron on a
white piece of paper. Label
Cell bodyNucleusDendritesaxon
Myelin sheathSchwann cellsNode of RanvierSynaptic knob
Then draw arrows to show the message direction
Identify the motor neuron functions