Nervous system

A system that controls all of the activities of the body. The nervous system is made of: The spinal cord The brain The nerves The senses

THE NERVOUS SYSTEM The nervous system consists of two parts: Central Nervous System Peripheral Nervous System

Central Nervous System Central Nervous System: is composed of the brain and spinal cord. - The brain and spinal cord serve as the main "processing center" for the entire nervous system, and control all the workings of your body.

Peripheral Nervous System Peripheral Nervous System:  nerves that extends from the brain and spinal cord. 12 cranial nerves 31 spinal nerves

Peripheral Nervous System It connects all parts of the body to the central nervous system. The peripheral nervous system is further divided into two parts called the somatic nervous system  the autonomic nervous system.

Peripheral Nervous System (Somatic) The somatic nervous system (SNS) is the portion of the nervous system responsible for voluntary body movement and for sensing external stimuli. A person’s sense of touch, taste, sight, sound and smell are controlled by the somatic nervous system.

Peripheral Nervous System (Somatic) Also, the somatic nervous system is what causes the body to feel heat, cold, and pain. Reflex reactions of skeletal muscle however are an exception. These are involuntary reactions to external stimuli.

Peripheral Nervous System (autonomic) Autonomic nervous system or visceral nervous system: controls and regulates the body internally. It controls involuntary muscles such as smooth muscles and cardiac muscles. This system is also called the involuntary nervous system.  

Sympathetic vs. Parasympathetic Nervous System The autonomic nervous system is comprised of the sympathetic and parasympathetic nervous syste ms.

Sympathetic Nervous System The sympathetic nervous system allows body to function under stress. - Fight or Flight response: is our body's automatic response to "fight" or "flee" from perceived attack, harm or threat to our survival.

Parasympathetic Nervous System The parasympathetic nervous system is responsible for stimulation of activities that occur when the body is at rest. E.g. salivation, lacrimation and digestion.

These two systems generally act in opposition to each other. PERIPHERAL NERVOUS SYSTEM (sympathetic and parasympathetic nervous systems) These two systems generally act in opposition to each other. E.g. A stimulation by the sympathetic system on the heart would increase contractions, while a stimulation of the parasympathetic system would decrease heart contraction. These systems operate simultaneously (one may be operating at a higher level of activity)

PERIPHERAL NERVOUS SYSTEM Somatic Nervous Autonomic Nervous System System Parasympathetic Sympathetic

To Do List Follow instructions on handout (1,3 and 4) Find a partner. Build two models of the brain using modeling clay. Label your brain model. Make Q cards. Test your partner. Go over PowerPoint slides as a class.

Brain Model #1 Brain Model #2

Cerebrum: Frontal lobe Responsible for thinking and creativity

Cerebrum: Parietal lobe Control memory of objects and their uses, and direction

Cerebrum: Motor Area & Sensory Area

Cerebrum: Temporal lobe Control hearing, speech and memory

Cerebrum: Occipital lobe Nerve impulses from the eyes are received and turned into images.

Cerebrum: Insular lobe Located under the other four lobes – it cannot be seen without pushing aside the frontal and temporal lobes It may control behaviour related feelings

Cerebellum “Little Brain” This structure controls movement, posture and balance It also may play a role in learning

Contains thalamus, hypothalamus, optic tracts, part of the pituitary gland, and the pineal gland

Brain Stem Connects to the spinal cord Divided into three parts

Neurons Also called nerve cells – are the cells of the nervous system. A neuron is made up the following parts:

Dendrites Are branchlike extensions of the neuron that receive impulses and carry them towards the cell body. Receives signals from other neurons. Dendrites Axon

Cell Body Contains the nucleus and many organelles

Axons Is an extension of the neuron that carries impulses away from the cell body and toward neurons, muscles and glands.

Parts of the Axon Nodes of Ranvier: gaps formed between myelin sheath cells along the axons. Schwann Cells: cover the axons and form the myelin sheath. Myelin Sheath: insulates axon

Nodes of Ranvier Gaps between insulation

Schwann Cells Forms the insulating myelin sheath

Myelin Sheath Myelin Sheath: consists of fat containing cells that insulate the axon from electrical activity. - Fat is a very good insulator and speeds the rate of transmission of an electrical impulse along the axon. - The myelin sheath gives the axon a white appearance(white matter) PS: the absence of myelin in masses of neurons accounts for the grayish colour(gray matter) in the brain.

White Matter vs. Grey Matter

Neurons transmit information as electro-chemical signals to and from the brain. Unlike most other cells in the body, neurons are amitotic, meaning they cannot divide or reproduce

3 Main Types of Neurons Sensory Neuron Interneuron Neuron Motor Neuron

Sensory Neuron Carries impulses from the body(sense organs) to the spinal cord and brain. E.g. pain receptors in skin to the CNS (brain or spinal cord)

Interneurons Interneurons are found within the brain and spinal cord. An interneuron acts as links between sensory neuron and a motor neuron. It also receives information from other interneurons and from sensory neurons.

Motor Neurons Carries the response impulses away from the brain and spinal cord to a muscle or gland.

Nerve Impulse Travels down the axon

Membrane Potential A nerve impulse is generated when there is a change in electro-chemical charges of the cell membrane

A nerve impulse results from a change in membrane potential

The Synapse

The Synapse is made up of: Presynaptic cell (axon terminal) Contains neurotransmitters that are stored within vesicles Synaptic Cleft

The Synapse is made up of: Synaptic cleft The gap in between the axon of one neuron and the dendrite of another or between the axon of a neuron and a muscle fibre. Synaptic Cleft

The Synapse is made up of: Postsynaptic cell (dendrite or muscle fibre) Contains receptor sites for neurotransmitters to bind Synaptic Cleft

Vocabulary Intervention Vesicles – little sacks found within cells that are surrounded by a membrane

When a neuron is activated by a nerve impulse, vesicles containing neurotransmitters migrate towards the membrane at the presynaptic ending and are released through a process called ____________________. The binding initiates a nerve impulse in the adjacent neuron, muscle or gland. exocytosis

Recall: Exocytosis Transport materials out of the cell. “exo” meaning exit Important for expulsion of waste materials and to secrete important macromolecules such as, enzymes and hormones.

Neurotransmitters Are chemicals made in neurons Diffuses across the synaptic cleft and binds to the receptors on the dendrites, muscles or glands.

Neurotransmitters After binding to the receptor sites, neurotransmitters need to be inactivated. This can be done by re-uptake into the presynaptic cell or degradation by enzymes.

Types of Neurotransmitters: 1) Dopamine Produces feelings of pleasure and euphoria Shortage – Parkinson’s Disease Overabundance - Schizophrenia

Types of Neurotransmitters: 2) Epinephrine Another term for adrenaline Acts on sympathetic nervous system

Types of Neurotransmitters: 3) Serotonin Play a role in sleep and regulation of mood Shortage – Depression

Types of Neurotransmitters: 4) Acetylcholine First neurotransmitter to be discovered Released in neuromuscular junctions (between neurons and muscles) Activates muscles

What is a Drug? A substance that affects the functioning of the brain and body It affects the communication of information between neurons and between neurons and other cells of the body.

Drugs can have the following effects on neurotransmitters: Can inhibit or increase the release of neurotransmitters Block the reuptake or degradation of neurotransmitters Bind to the receptors on dendrites

Neurons do not touch each other Neurons do not touch each other. They have gaps in between them called synaptic clefts. A synapse is between the axon endings of one neuron and the dendrites of another neuron or a muscle fibre or gland.

A synapse is made up of: A presynaptic ending (axon terminal)

To complete the signal, a neurotransmitter is released at the gap to signal the next neuron. Receptors on the dendrite receives the chemical signal.