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Health & Social Care level3
Nervous system & Neurones
Learning outcomes
• At the end of this session, you will be able to:• Describe how parts of the nervous system
communicate• Remember that there are three types of
neurone• Consider how the reflex arc works• Examine the para sympathetic and
sympathetic nervous systems function
Neurones
• The nervous system is composed of nerve cells, or neurones
• There are 3 types:
• Motor neurones • Sensory neurones • Interneurones • http://www.youtube.com/watch?v=i-NgGKSNiNw&f
eature=related
Motor Neurone:Moving toward a central organ or point
Relays messages from the brain or spinal cord to the muscles and
organs
Sensory Neurone: Moving away from a central organ or point
Relays messages from receptors to the brain or spinal cord
Interneuron (relay neurone):
Relays message from sensory neurone to motor neurone
Sensory neuron Interneuron Motor Neuron
Length of FibersLong dendrites and short axon
Short dendrites and short or long axon
Short dendrites and long axons
LocationCell body and dendrite are outside of the spinal cord
Entirely within the spinal cord or CNS
Dendrites and the cell body are located in the spinal cord; the axon is outside of the spinal cord
FunctionConduct impulse to the spinal cord
Interconnect the sensory neuron with appropriate motor neuron
Conduct impulse to an effector (muscle or gland)
Structure of Neurones
Structure of Neurones • A neurone has a cell body with extensions leading off it.
• Dendron's and dendrites provide a large surface area for connecting with other neurones, and carry nerve impulses towards the cell body.
• Axon carries the nerve impulse away from the cell body.
• Schwann cells, which wrap their cell membrane around the axon many times in a spiral to form a thick insulating and conductive lipid layer called the myelin sheath.
• Nerve impulse can be passed from the axon of one neurone to the Dendron of another at a synapse.
interneuron
Remember!
Humans have three types of neurones:
Sensory neurones: have long axons and transmit nerve impulses from sensory receptors all over the
body to the central nervous system.
Motor neurones: also have long axons and transmit nerve impulses from the central nervous system
to effectors (muscles and glands) all over the body.
Interneurones: (also called connector neurones or relay neurones) are usually much smaller cells,
with many interconnections.
The Reflex Arc • The three types of neurones are arranged in circuits and
networks, the simplest of which is the reflex arc
• In a simple reflex arc, such as the knee jerk, a stimulus is detected by a receptor cell, which synapses with a sensory neurone.
• The sensory neurone carries the impulse from site of the stimulus to the central nervous system (the brain or spinal cord), where it synapses with an interneuron.
• The interneuron synapses with a motor neurone, which carries the nerve impulse out to an effector, such as a muscle, which responds by contracting.
The Reflex Arc
Reflex arc can also be represented by a simple flow diagram
Organisation Of The Human Nervous System:
The human nervous system is far more complex than a simple reflex arc, although the same stages still apply. The organisation of the human nervous system is shown in this diagram:
• Central nervous system (CNS): Consists of the brain and spinal cord & is effectively the centre of the nervous system, it processes information received from the peripheral nervous system.
• Peripheral nervous system (PNS): portion of the nervous system that is outside the brain and spinal cord. Connected the CNS, to sensory organs & other organs of the body, muscles, blood vessels and glands.
• Somatic nervous system (SNS): part of the PNS that regulates body movement through control of skeletal (voluntary) muscles and also relates with the environment through the reception of external stimuli, such as through the senses of vision, hearing, taste, and smell.
• Autonomic nervous system (ANS): controls the bodies internal environment. Vital in the process of homeostasis and helps control the heart rate, blood pressure, digestion, respiration, blood pH and other bodily functions. Controls are done automatically below the conscious level.
• Sympathetic & Parasympathetic nervous system: Part of the ANS and responsible for control. Essentially speeding up or slowing down of processes, linked to ‘fight or flight’.
overview
• http://www.youtube.com/watch?v=cqvoV4R7T2g
• The basic nervous system• http://www.youtube.com/watch?v=eKAObu3
v9cA&feature=related• This might (or might not) help
Central, Peripheral & Autonomic Nervous Systems
Organ Sympathetic System Parasympathetic System
Eye
Tear glands
Salivary glands
Lungs
Heart
Gut
Liver
Bladder
Dilates pupil
No effect
Inhibits saliva production
Dilates bronchi
Speeds up heart rate
Inhibits peristalsis
Stimulates glucose production
Inhibits urination
Constricts pupil
Stimulates tear secretion
Stimulates saliva productionConstricts bronchi
Slows down heart rate
Stimulates peristalsis
Stimulates bile production
Stimulates urination
Sympathetic & Parasympathetic Control
Sympathetic & Parasympathetic Control
overview
• Produce an overview in your own words on the nervous system