The nervous system(1)

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