The Nervous System 6 Lesson 6.1: Overview of the Nervous System Lesson 6.2: Transmission of Nerve Impulses Lesson 6.3: Functional Anatomy of the Central Nervous System Lesson 6.4: Functional Anatomy of the Peripheral Nervous System Lesson 6.5: Injuries and Disorders of the Nervous System

Overview of the Nervous System Chapter 6: The Nervous System Lesson 6.1 Overview of the Nervous System

Do Now Pick three words and write the definition of each. All words are on page 201. Central Nervous System Peripheral Nervous System Afferent Nerves Efferent Nerves Somatic Nervous System Autonomic Nervous System

Today’s Objectives Differentiate between the central nervous system and peripheral nervous system, and explain the function of each. Explain the differences between afferent and efferent nerves. Describe the functions of the somatic and autonomic branches of the nervous system. Identify the general role of the glial cells. Describe the anatomical structure of a typical neuron.

Nervous System Overview The nervous system controls voluntary movement by activating skeletal muscle, but also directs the involuntary functions of smooth muscle in internal organs and cardiac muscle. By automatically controlling the functions of smooth muscle and cardiac muscle, the nervous system ensures that these life functions are able to occur without conscious thought.

Nervous System Overview organization of the nervous system two major divisions categorized by: Structural Functional the efferent nerves nervous tissues neuroglia neurons

Organization of the Nervous System Two major divisions Central nervous system (CNS) Peripheral nervous system (PNS) Peripheral nervous system divided into subdivisions: sensory receptors afferent (sensory) nerves efferent (motor) nerves

Two Major Divisions

Major Divisions Central Nervous System (CNS) Peripheral Nervous System Includes the brain and spinal cord. The CNS directs the activity of the entire nervous system. Peripheral Nervous System Includes spinal nerves that transmit information to and from the spinal cord Cranial nerves transmit information to and from the brain. Also includes sensory receptors which respond to stimuli such as pressure, pain, or temperature.

Afferent Nerves Efferent Nerves Nerves that transmit impulses from the sensory receptors in the skin, muscles, and joints to the CNS Efferent Nerves Nerves that carry impulses from the CNS out to the muscles and glands.

The Efferent Nerves There are two functional subdivisions of the efferent (motor) nerves somatic nervous system Stimulates skeletal muscles causing them to develop tension. Voluntary control autonomic nervous system Controls the cardiac muscle of the heart and the smooth muscles of the internal organs. Involuntary control Includes two separate branches sympathetic parasympathetic

Nervous Tissues 2 Categories of tissues neuroglia neurons also known as glial cells support the neurons protect the neurons neurons transmit nerve impulses

Neuroglia astrocytes microglia ependymal oligodendrocytes Within the central nervous system there are 4 types of glial cells. astrocytes microglia ependymal oligodendrocytes

Central Nervous System Glial Cells Astrocytes Positioned between neurons and capillaries. Protect the neurons from any harmful substances in the blood. Microglia Absorb and dispose of dead cells and bacteria Ependymal Form protective coverings around the spinal cord and central cavities within the brain. Oligodendrocytes Wrap around nerve fibers and produce a fatty insulating material called myelin.

Neuroglia peripheral nervous system includes 2 forms of glial cells Schwann cells Form the fatty myelin sheaths around nerve fibers satellite cells Serve as cushioning support cells

Neurons Glial cells provide support and protection for the nervous system, but it is the neurons that transmit information in the form of nerve impulses. Typical neuron has a long, tail-like projection called an axon. dendrites send information to cell body cell bodies Includes a nucleus and mitochondria axons send information away from cell body

Neuron Types by Function sensory neurons (afferent) send impulses toward CNS Impulses from the skin and organs to the spinal cord and brain. Provides information about the external and internal environments. motor neurons send impulses away from CNS Transmits impulses from the brain and spinal cord to the muscles and glands, directing body actions. interneurons bridges between neurons

Neuron Structures bipolar unipolar multipolar one axon and one dendrite unipolar one axon multipolar one axon and many dendrites

Review and Assessment Match these words with 1–4 below: sympathetic nervous system, myelin, synapse, axon. 1. high alert 2. transmits impulses away from cell body 3. fatty insulating material 4. gap between neurons

END

Exit Ticket Which of the following is not a major division of the nervous system? a. Central Nervous System b. Peripheral Nervous System c. Afferent Nervous System

2) T or F: The central nervous system has afferent nerves that carry impulses TOWARDS muscles and glands. 3) When sending nerve impulses, the purpose of the myelin sheaths are to: a. Decrease the speed of the transmission. b. Increase the speed of the transmission. c. Block any messages being sent. d. None of the above.

Transmission of Nerve Impulses Chapter 6: The Nervous System Lesson 6.2 Transmission of Nerve Impulses

Do Now Work on the “Learning the Key Terms” Worksheet Chapter 6 Lesson 2 begins on page 202, or use the glossary which begins on page 579. You have 8 minutes to complete the worksheet. Turn the worksheet into Mr. B when you are finished.

Today’s Objectives Lesson 6.2 Transmission of Nerve Impulses Define action potential and explain how action potentials are generated. Explain the factors that influence the speed of neural impulse transmission. Describe how impulses are transmitted across the synapse. Discuss the roles played by neurotransmitters. Describe the three types of reflexes and explain how they work.

Intro Neurons have one behavior property in common with muscles: Irritability – the ability to respond to a stimulus. However, neurons have an aspect of irritability that muscles DO NOT have: converting stimuli into nerve impulses. Nerve impulse = a tiny electrical charge that transmits information between neurons.

Transmission of Nerve Impulses Action Potentials When a neuron is inactive, there are potassium ions (K+) inside the cell and sodium (Na+) ions outside the cell membrane. Inside of the membrane is more negatively charged than the outside (Polarized). When a stimulus is involved it changes the charge so the inside is more positive (Depolarized) This change in charge is known as an Action Potential. Following the discharge of the action potential, it goes back to it original charge (Repolarization)

Transmission of Nerve Impulses Impulse Transmission 3 factors the sped at which a nerve impulse travels: Myelin sheath The presence of a myelin sheath acts as an electrical insulator and causes the action potentials to “jump”. This increases the speed in which an impulse travels. Diameter of Axon The larger the axon, the more ions available to conduct the current. Example: A large diameter pipe moves more water compared to a small diameter pipe.

Impulse Transmission Transmission at Synapses Neurotransmitters Chemical messengers excitatory effect Activates muscle fibers Inhibitory effect Blocks pain messages

Transmission of Nerve Impulses Temperature Warm temperatures increase ion diffusion rates. This increases the speed at which impulses will travel. Cold temperatures decrease diffusion rates. Example: when you hold an ice cube you have a numbing sensation. The cold area takes longer to send information about touch, pain, pressure, and temperature to your brain.

Reflexes Simple, rapid, involuntary, programmed responses to stimuli. 2 Categories of reflexes: Somatic Involve the skeletal muscles. Example: withdrawing your hand quickly from something hot even before you realized that it was hot. Autonomic Reflexes Send involuntary stimuli to the cardiac muscle of the heart and the smooth muscle of internal organs. Stimulates involuntary muscles.

Review and Assessment Fill in the blanks with: reflexes, saltatory conduction, neurotransmitter, or action potential. 1. A(n) _______________ is an all or none response. Action Potential Saltatory conduction 2. _______________ occurs only in myelinated axons. Reflexes neurotransmitter 3. _______________ are rapid, involuntary responses. 4. The axon terminal has tiny vesicles filled with _______________.

END

Exit Ticket Some factors that can influence the speed of a nerve impulse are: a. body temperature b. diameter of the axon c. presence of a myelin sheath d. all of the above e. none of the above

2) T or F: An action potential is generated when an electrical charge produced in a nerve or muscle fiber through stimulation. 3) Reflexes are ___: a. complex, slow, and voluntary responses b. complex, fast, and involuntary responses c. simple, rapid, and involuntary responses d. simple, slow, and voluntary responses.

4) Somatic reflects involve which type of muscles and which type of action? a. Skeletal muscle, involuntary b. Skeletal muscle, voluntary c. Cardiac, voluntary d. Cardiac, involuntary

Functional Anatomy of the Central Nervous System Chapter 6: The Nervous System Lesson 6.3 Functional Anatomy of the Central Nervous System

The Brain cerebrum diencephalon brain stem cerebellum meninges blood-brain barrier

Cerebrum cerebral cortex lobes primary motor cortex gyrus sulcus fissure lobes frontal parietal occipital temporal primary motor cortex primary somatic sensory cortex

Cerebrum

Diencephalon thalamus hypothalamus epithalamus

Brain Stem midbrain pons medulla oblongata

The Brain cerebellum meninges blood-brain barrier dura mater arachnoid mater pia mater

Spinal Cord

Review and Assessment True or False? 1. The gyri divide the brain into 4 regions. 2. The hypothalamus regulates blood pressure. 3. The meninges has 3 layers. 4. The cerebellum coordinates balance. 5. The pons is also called the interbrain.

Functional Anatomy of the Peripheral Nervous System Chapter 6: The Nervous System Lesson 6.4 Functional Anatomy of the Peripheral Nervous System

Functional Anatomy of the Peripheral Nervous System nerve structure cranial nerves spinal nerves and nerve plexuses autonomic nervous system

Nerve Structure endoneurium perineurium epineurium covers axons bundles fascicles epineurium wraps nerves

Cranial Nerves

Spinal Nerves and Nerve Plexuses 31 pairs dorsal root ventral root dorsal ramus ventral ramus plexuses

Autonomic Nervous System preganglionic and postganglionic neurons sympathetic nerves fight-or-flight action parasympathetic nerves resting or digesting action

Review and Assessment Match these words with 1–4 below: efferent, ganglion, optic, perineurium. 1. wraps fascicles 2. motor 3. a cranial nerve 4. enlarged junction

Injuries and Disorders of the Nervous System Chapter 6: The Nervous System Lesson 6.5 Injuries and Disorders of the Nervous System

Injuries to the Brain and Spinal Cord traumatic brain injury cerebral palsy spinal cord injury

Traumatic Brain Injury violent impact to head mild moderate severe

Cerebral Palsy damage to brain motor function impairment before birth during birth during infancy motor function impairment

Spinal Cord Injuries C1–C3: usually fatal C1–C4: quadriplegia C5–C7: paralysis of lower extremities T1–L5: paraplegia Corepics/Shutterstock.com

Common Diseases and Disorders of the CNS meningitis multiple sclerosis epilepsy Parkinson’s disease dementia and Alzheimer’s disease

Review and Assessment Match these words with 1–4 below: quadriplegia, multiple sclerosis, dementia, cerebral palsy. 1. inflammation destroys myelin sheath 2. loss of memory and thinking 3. loss of function below the neck 4. may begin before birth