The Nervous System Objectives – What you will need to know from this section Outline the nervous system components: central nervous system (CNS) and the peripheral nervous system (PNS) Receptor messages are carried through these systems by nerve cells or neurons. Outline the structure & function of the neuron including: cell body, dendrites, axon, myelin sheath, schwann cell, and neurotransmitter vesicles & synaptic cleft Outline impulse movement & synapse. Explain activation & inactivation of neurotransmitter.

2 The Nervous System The structure and function of a neuron: variation in size and shape. Neuron -- Three part structure: > dendrite(s) receive information and carry it towards the cell body, > the axon conducts nerve impulses away from the cell body, > the cell body contains the nucleus and other organelles and produces neurotransmitter chemicals. Explain the role & position of 3 types of neuron -- sensory/motor/inter Movement of nerve impulse. (Detailed knowledge of electrochemistry not required.

The Nervous System 3 Knowledge that the conduction of nerve impulses along a neuron involves movement of ions (details not required). Outline the senses with the brain as an interpreting centre.  Outline the CNS, brain & spinal cord. State location & function of cerebrum / hypothalamus / pituitary gland / cerebellum / medulla oblongata Label &/or draw diagrams of spinal cord (cross section) indicating : white matter, grey matter, central canal, 3 layer protective tissue-meninges. Spinal nerves containing dorsal and ventral roots that project from the spinal cord

The Nervous System 4 Outline disorders from NS disorders: paralysis/Parkinson's including: Cause/Prevention/Treatment Outline PNS including the location nerve fibres & cell bodies. State the role, structure & mechanism of the Reflex arc/action.

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 The nervous system relies on electrical signals, carried by specialised cells [neurons], and is involved in fast responses. The central nervous system (CNS) is your 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) is the nerves branching from the CNS to all parts of the body.

Comparison of the endocrine and nervous systems - 1 The Nervous System 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 The Nervous System Comparison of the endocrine and nervous systems - 1 Endocrine Nervous 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 The Nervous System 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 The Nervous System Comparison of the endocrine and nervous systems -- 2 Endocrine Nervous Speed of transmission Usually slow Rapid Effects Can be widespread Localised usually Duration long-lasting (hours) Usually brief (seconds)

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? List the main differences between the endocrine and nervous systems.

The Nervous System NS ----- Co-ordination & Response 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.

The Nervous System Neuron structure The cell body contains the nucleus and other organelles and produces neurotransmitter chemicals. A dendron is a short fibre that receives information and carries it towards the cell body. The axon is a very long fibre that conducts impulses away from the cell body.

The Nervous System Neuron structure A dendron is a short fibre that receives information and carry it towards the cell body. Dendrites are small branches of a dendron. Many Schwann cells wrap their fatty cell membranes around an axon, forming a myelin sheath. The myelin sheath insulates the neuron from electrical impulses flowing in other neurons.

The Nervous System There are three types of Neuron : Sensory neuron –carries messages from the sense organ to the central nervous system (CNS). Interneuron –connects sensory and motor neurons and so carries messages within the CNS. Motor neuron –carries impulses from the CNS to muscles and glands.

The Nervous System

Synapse—region where two neurons come into close contact. The Nervous System Synapse—region where two neurons come into close contact. SYNAPS E Synaptic cleft—the gap between two neurons, bridged by chemicals (neurotransmitters). Neurotransmitter—chemical released across a synaptic cleft to carry a signal from one neuron to another. The chemical is then destroyed or removed

LEARNING CHECK What is a stimulus? What is a receptor? 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?

The Nervous System 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 Nervous System The Brain The cerebrum is our conscious brain, with different parts having different jobs to do. cerebrum hypothalamus pituitary The hypothalmus is the centre for the regulation of the internal organs. The pituitary ‘[master] gland secretes hormones that stimulate other glands to release their hormones.

The Nervous System

The Nervous System 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

The Nervous System The cerebellum co- ordinates processes that we have learned to do automatically, such as speaking. cerebellum Medulla oblongata The medulla oblongata co-ordinates involuntary, automatic processes — such as breathing, heartbeat.

LEARNING CHECK Name the 3 main parts of the brain and one function of each. How is the brain protected? What is meant by “conscious action”? What does the term “involuntary” mean? Distinguish between the cerebrum and the cerebellum.

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

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

The Nervous System Grey matter contains cell bodies and dendrites (regions of a neuron that have no white myelin covering). Outside the grey matter, the spinal cord consists of white matter (containing axons only).

The Nervous System 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 nerve fibres carrying information into the spinal cord from the senses. The dorsal root ganglion is a swelling that consists of the cell bodies of the sensory neurons.

The Nervous System The ventral root consists of nerve fibres carrying information out 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. The spinal cord transmits impulses to and from the brain and controls many reflex actions.

The Nervous System REFLEX ACTION --- The Reflex Arc A reflex action is a quick, automatic response to a particular stimulus. Interneuron

Suppose you touch a hot flame. The Nervous System REFLEX ACTION --- The Reflex Arc Suppose you touch a hot flame. Inter neuron Almost instantly you pull your hand away. In this brief instant, a message has been carried by a sensory neuron from pain receptors in the skin to the spinal cord.

The Nervous System In the spinal cord, the message is passed on to an interneuron and then to a motor neuron, and so into muscles that respond by contracting and pulling your hand from the flame. Interneuron

This response saves the body from injury. The Nervous System Interneuron This response saves the body from injury. The response is called a reflex action, as it does not involve conscious control, and is predictable and automatic. Many of the activities of the body, such as breathing and keeping our balance, are regulated by reflex actions.

LEARNING CHECK How is the spinal cord protected? Distinguish between grey and white matter. Distinguish between dorsal and ventral root What is meant by reflex action? Give some examples of reflex action> What is an interneuron? Distinguish between cell bodies and ganglions.

Nervous System Disorder The Nervous System Nervous System Disorder Parkinson’s disease is a nervous system disorder, normally seen in older people, in which muscles become rigid and movement is slow and difficult, with persistent tremors [shaking]. It is caused by the brain reducing the normal amount of dopamine that it makes. There is at present no means of preventing it, but giving L-dopa (which the body changes into dopamine) can relieve the symptoms in many patients.