Chapter 33 The Nervous System

Syllabus The structure and function of the human nervous system. Describe the structure of the neuron. Outline impulse movement between nerves. Name & give the role of the 3 types of neuron -- sensory/motor/inter. Outline the nervous system components: central nervous system (CNS).

State location & function of hypothalamus, cerebellum & medulla oblongata Draw a labelled diagram of a cross section through the spinal. Describe the peripheral nervous system. State the mechanism & function of the Reflex arc/action. Outline disorders from NS disorders: paralysis/Parkinson's including: Cause/Prevention/Treatment

The Nervous System Organisms must be aware of what is happening around them as this affects their survival chances. Co-ordination of an organism’s activities is carried out by the nervous system and the endocrine system. A nervous system allows an organism to detect and respond to stimuli in its internal or external environment. A stimulus is any change in your environment e.g. a flash of light, a noise, a fly landing on your nose.

The nervous system is divided into: the central nervous system (CNS) = brain and spinal cord. The brain keeps a check on internal organs and activities, such as the level of carbon dioxide or water in the blood.

the peripheral nervous system (PNS) = the nerves branching from the CNS to all parts of the body.

Nervous coordination involves: A stimulus is any change in your environment A receptor is a nerve cell that detects the stimulus A neuron is a specialised cell that carries electrical messages /impulses around the body. An impulse is an electrical message that is carried along a neuron. A response is a muscle or gland carries out the effect.

A neuron is a nerve cell. There are three types of neurons. Sensory neurons carry messages from the sense organ to the CNS. Motor neurons carry impulses from the CNS to muscles and glands. Interneurons connect motor and sensory neurons in the CNS. The nervous system

Neurons or nerve cells - Structure function and types of neurons 4:09mins

LEARNING CHECK Co-ordination of an organism’s activities is carried out by what 2 body systems? Distinguish between the CNS and PNS. What is a neuron? What is an impulse? What is a stimulus? What is a receptor? Explain what is involved in Nervous coordination.

The main parts of a neuron: The cell body contains the nucleus and other organelles and produces neurotransmitter chemicals. A dendron / dendrites is a fibre that receives information and carry impulses towards the cell body. The axon is a long fibre that carries nerve impulses away from the cell bodies.

Schwann cells form a myelin sheath. The myelin sheath insulates the electrical impulses flowing in the neurons.

Neuron structure

A nerve impulse involves A Synapse — region where two neurons come into close contact. A Synaptic cleft—the gap between two neurons, bridged by chemicals (neurotransmitters).

The central nervous system

How are electrical messages carried from one neuron to the next: Neurotransmitter swellings / synaptic knobs produce neurotransmitters (chemicals) such as acetylcholine (ACh). that are released & diffuse across the synaptic cleft causing the production of an electrical impulse at the other side They are eventually broken down / destroyed by enzymes.

SYNAPSE & NEUROTRANSMITTERS

Nerve impulse transmission: There is a threshold for the minimum stimulus needed for an impulse to travel. The ‘all or nothing’ law says that: - if the threshold is reached, an impulse travels - if the threshold is not reached, no impulse travels. The synapse

LEARNING CHECK Name the main parts of a neuron and give one function of each. Distinguish between a sensory and motor neuron. Distinguish between synapse and synaptic cleft. What are neurotransmitters? Explain the Nerve impulse transmission.

The Brain The brain is composed of over 100 billion neurons, each receiving messages simultaneously from thousands of other neurons. The brain is protected by the skull bones, meninges (three membranes) and cerebrospinal fluid.

The cerebrum controls sight, Hearing, Intelligence & Memory cerebrum

The hypothalamus controls Homostasis - the regulation of the internal organs.

The cerebellum co-ordinates voluntary muscles & balance

The medulla oblongata co-ordinates involuntary muscles e. g The medulla oblongata co-ordinates involuntary muscles e.g. the diaphragam. Medulla oblongata

LEARNING CHECK Name the 4 main parts of the brain. State the location of the 4 main parts of the brain. State the function of cerebrum, hypothalamus, cerebellum, & medulla oblongata.

The spinal cord is well protected by the vertebrae, meninges (three membranes) and cerebrospinal fluid. It transmits impulses to and from the brain & controls many reflex actions.

A cross-section through the spinal cord shows a small central canal, filled with cerebrospinal fluid, surrounded by an area of grey matter, shaped like the letter H.

The spinal cord: In humans, 31 pairs of spinal nerves branch off from the spinal cord. Each spinal nerve has a dorsal root and a ventral root. The dorsal root consists of sensory neurons carrying information from the senses into the spinal cord. The dorsal root ganglion is a swelling that contains the cell bodies of the sensory neurons. The dorsal root ganglion white matter contains axons.

The ventral root consists of motor neurons carrying information from the spinal cord to the muscles and glands. The cell bodies of the motor neurons are positioned within the grey matter of the cord. interneurons connect sensory and motor neurons.

REFLEX ACTION --- The Reflex Arc Interneuron

A reflex action is an automatic response to a stimulus A reflex action is an automatic response to a stimulus. Reflex actions are: fast responses designed to protect the body

Suppose you touch a hot flame. The route taken along a receptor → sensory neuron → spinal cord → interneuron → motor neuron → effector, causes you almost instantly to pull your hand away. Interneuron

Knee Jerk Reaction The Nervous System ( Animation )

Nervous System Disorder Parkinson’s disease is a nervous disorder caused by a lack of dopamine in the brain results in trembling limbs, a rigid body and inability to walk properly cannot be prevented is treated by physiotherapy and drugs – Levadopa.

Conscious actions A conscious action is one where the brain makes a considered response. Here’s what happens: 4) The brain decides to move away the hand 3) Here another sensory neuron carries the signal to the brain 5) This impulse is sent by MOTOR NEURONS to the hand muscles (the effectors) via the spinal chord… 2) The impulse is carried by SENSORY NEURONS to the spinal chord 1) Receptors in your skin detect a stimulus 6) Which then moves the hand away Stimulus Receptor Sensory Neuron Coordinator Motor Neuron Effector Response

LEARNING CHECK Draw a labelled diagram of a cross section through the spinal. State the mechanism & function of the Reflex arc/action. Distinguish between grey and white matter. Distinguish between dorsal and ventral root. What is meant by reflex action? Outline a disorder from the NS. What is it’s Cause/Prevention/Treatment?

Quiz Human Responses (The Nervous system) Sensory neurons transmit impulses to the _______ 2. Motor neurons transmit impulses to the_____ 3. The gap separating two neurons is called a ____ 4. An impulse is carried across this gap by a _____ 5. There are 3 types of neurons - sensory, motor and ____ 6. Impulses are carried to the nerve cell body by a ____ 7. Impulses are carried away from the cell body by an ____ 8. Schwann cells make _________________ 9. The membrane covering the brain is called the ____ 10. A reflex action is an automatic response to a ______

Human Responses (The Nervous system) 1. CNS (Central Nervous System) 2. Muscles/Glands 3. Synapse/ synaptic cleft 4. Neurotransmitter 5. Autonomic 6. Dendrite 7. Axon 8. Myelin/ Myelin sheath 9. Meninges 10. Stimulus

Comparison of the endocrine and nervous systems - 1 Target organ Received by Blood Carried by Gland Cells involved Cells throughout the body Message sent to Chemical (Hormone) Message Endocrine

Comparison of the endocrine and nervous systems - 1 Cells involved Gland Sense receptor Message Chemical (Hormone) Electrical(Impulse) Carried by Blood Nerve cell Message sent to Cells throughout the body A specific cell or tissue Received by Target organ Effector (muscle or gland)

Comparison of the endocrine and nervous systems -- 2 long-lasting (hours) Duration Can be widespread Effects Usually slow Speed of transmission Endocrine

Comparison of the endocrine and nervous systems -- 2 Speed of transmission Usually slow Rapid Effects Can be widespread Localised usually Duration long-lasting (hours) Usually brief (seconds)

http://www. youtube. com/watch http://www.youtube.com/watch?v=YRwPMICvbT4&feature=youtube_gdata_player The Nervous System- Animation-Video for Kids