Nervous System Learning Package PDF

**[Nervous System]** ================================ **OVERVIEW** ------------ Control and integration are very important functions because body systems work together to maintain homeostasis. In this unit, you will learn about the two systems of the body whose main responsibilities are to organiz...

**[Nervous System]** ================================ **OVERVIEW** ------------ Control and integration are very important functions because body systems work together to maintain homeostasis. In this unit, you will learn about the two systems of the body whose main responsibilities are to organize cellular activities and body system activities to promote homeostasis: the nervous system and the endocrine system. The rapid response system, the nervous system, is similar to an early detection warning system. The nervous system is constantly monitoring the body's internal and external environment through sensory information and it relays the information to the appropriate control centers. After interpretation of the information, the control centers send out commands to initiate appropriate physiological responses to restore homeostasis. The endocrine system is slower to respond to changes in the internal and external environments, yet is capable of producing long lasting effects to these changes. The endocrine system functions by the influence of hormones from the nervous system, and also synthesizes and secretes various hormones. Endocrine hormones effect target organs and tissues, causing changes in an effort to maintain internal homeostasis. **LEARNING OBJECTIVES** ----------------------- Throughout this package you will develop knowledge and understanding of: - the structure and function of the nervous system including: - components of the nervous system -- neuron, brain, spinal cord - the subdivisions of the nervous system - cranial nerves and spinal nerves - impulse transmission - chemical transmitters and cerebrospinal fluid **PRE-CLASS ACTIVITIES** ------------------------ When studying the nervous system, it is helpful to understand its overall functions and fit your knowledge into the schema that evolves from its functions. These overall functions can be summarized as follows: a\) to sense information from either the external environment or the internal environment b\) to interpret this information and decide upon a response c\) stimulates cells, tissues, organs or systems to elicit a response Nerve cells are called *neurons*; they are specialists in nerve impulse transmission. 1\. Complete the following chart describing components of a typical neuron: +-----------------------------------+-----------------------------------+ | Neuron | Description (structure, function, | | | location) | | component | | +===================================+===================================+ | axon | | +-----------------------------------+-----------------------------------+ | axon terminals | | +-----------------------------------+-----------------------------------+ | cell body | | +-----------------------------------+-----------------------------------+ | dendrite | | +-----------------------------------+-----------------------------------+ | myelin sheath | | +-----------------------------------+-----------------------------------+ | node of ranvier | | +-----------------------------------+-----------------------------------+ 2\. Describe the following types of cells of the nervous system: a\) Purkinje neuron b\) glia c\) astrocyte d\) oligodendrocyte e\) microglia f\) ependymal g\) satellite h\) Schwann Neurons specialize in impulse conduction in the form of an electrical current. For our purposes, at this point it is sufficient to know that a nerve impulse is a wave of electro-negativity passing along a neuron cell membrane. Nerve impulses can travel in [only] one direction. There are three kinds of neurons: *sensory, association* and *motor* neurons. 3\. Complete the following chart differentiating the three types of neurons: Type of neuron Description (structure, function, location, direction of impulse transmission) ---------------- -------------------------------------------------------------------------------- association motor sensory 4\. In order for the nerve impulses to travel from one neuron to another and to effectors, they must travel across *synapses.* Define the term *synapse*. Neurotransmitter chemicals are important substances necessary for impulse transmission across synapses. *Acetylcholine* and *norepinephrine* are two examples of neurotransmitters you will learn. 5\. Neurotransmitter chemicals carry messages from one neuron to another. What stimulates the release of neurotransmitters? How do neurotransmitter chemicals facilitate impulse transmission? 6\. Neurotransmitter chemicals differ highly throughout the body. Although they can be very different, they have one characteristic in common -- they each have their own specific receptors that they bind to. Describe the characteristics of the following neurotransmitter classifications: a\) amino acids b\) biogenic amines c\) cholinergic d\) neuropeptides Structurally, the nervous system is divided into the *central nervous system* (CNS) and the *peripheral nervous system* (PNS). The brain and spinal cord make up the CNS. The peripheral nervous system is made up of the *somatic nervous system* and the *autonomic nervous system*. Both branches of the peripheral nervous system have a *sensory (afferent)* component and a *motor (efferent)* component. The autonomic nervous system is comprised of the *sympathetic nervous system* and the *parasympathetic nervous system*. 7\. Which division of the nervous system senses information from internal and external environments? 8\. Which division of the nervous system interprets this information and decides upon a response? 9\. Which division of the nervous system stimulates a response to the information? **[Central Nervous System]** 10\. Describe the blood-brain barrier. 11\. Complete the following chart [briefly] describing the various components of the central nervous system (brain and spinal cord): +-----------------------------------+-----------------------------------+ | Neuron | Description (structure, function, | | | location) | | component | | +===================================+===================================+ | cerebrum | | +-----------------------------------+-----------------------------------+ | cerebral hemispheres | | +-----------------------------------+-----------------------------------+ | cerebral cortex | | +-----------------------------------+-----------------------------------+ | frontal lobe | | +-----------------------------------+-----------------------------------+ | parietal lobe | | +-----------------------------------+-----------------------------------+ | temporal lobes | | +-----------------------------------+-----------------------------------+ | occipital lobe | | +-----------------------------------+-----------------------------------+ | basal ganglia | | +-----------------------------------+-----------------------------------+ | diencephalon | | +-----------------------------------+-----------------------------------+ | thalamus | | +-----------------------------------+-----------------------------------+ | hypothalamus | | +-----------------------------------+-----------------------------------+ | brain stem | | +-----------------------------------+-----------------------------------+ | midbrain | | +-----------------------------------+-----------------------------------+ | pons | | +-----------------------------------+-----------------------------------+ | medulla | | +-----------------------------------+-----------------------------------+ | cerebellum | | +-----------------------------------+-----------------------------------+ | ventricles | | +-----------------------------------+-----------------------------------+ Continuing downward from the brain is the second organ of the CNS, the spinal cord which is situated within the vertebrae from the skull downward to end at the second lumbar vertebrae. The spinal cord has two main functions: a\) it acts as a pathway for nerve impulses to and from the brain b\) it acts as an interpretive center for some basic responses (known as *reflexes*) 12\. Complete the following chart [briefly] describing the various components of the spinal cord: +-----------------------------------+-----------------------------------+ | Spinal cord | Description (structure, function, | | | location) | | component | | +===================================+===================================+ | a\) ascending tracts | | +-----------------------------------+-----------------------------------+ | b\) anterior horn | | +-----------------------------------+-----------------------------------+ | c\) central canal | | +-----------------------------------+-----------------------------------+ | d\) descending tracts | | +-----------------------------------+-----------------------------------+ | e\) dorsal nerve root | | +-----------------------------------+-----------------------------------+ | f\) foramen magnum | | +-----------------------------------+-----------------------------------+ | g\) lateral horn | | +-----------------------------------+-----------------------------------+ | h\) posterior horn | | +-----------------------------------+-----------------------------------+ | i\) ventral nerve root | | +-----------------------------------+-----------------------------------+ Vital to survival, the brain and the spinal cord require special protection from trauma so are carefully protected by the *meninges* and *cerebrospinal fluid.* 13\. What is decussation and why does it occur? 14\. Name the bony coverings of the brain and of the spinal cord. 15\. Covering the surface of the brain and spinal cord are three consecutive tissue coverings, the *meninges.* Describe each meningeal layer. 16\. State the location of the epidural, subdural and subarachnoid spaces. 17\. *Cerebrospinal fluid* (CSF) is produced, circulated and reabsorbed inside the CNS. What structures make cerebrospinal fluid? Where are they located? 18\. Describe the characteristics and location of CSF. 19\. What are the functions of cerebrospinal fluid? 20\. Through what structure is cerebrospinal fluid reabsorbed? **[Peripheral Nervous System]** The peripheral nervous system performs sensory and motor functions for the body. It is composed of cranial and spinal nerves, and the autonomic nervous system and the somatic nervous system. 21\. Describe the sensory (afferent) division of the peripheral nervous system. What is a receptor? 22\. Describe the motor (efferent) division of the peripheral nervous system. What is an effector? 23\. Complete the following charting differentiating the somatic nervous system and autonomic nervous system: Nervous system Type of control Effectors that are innervated ---------------- ----------------- ------------------------------- Somatic Autonomic **[Cranial and Spinal Nerves]** The *spinal nerves* contain sensory and motor fibers. They send messages from receptors to the spinal cord, and take messages from the spinal cord to effectors. They are named in relation to the vertebral level at which they enter and exit the spinal cord. Spinal nerves carry sensory information to the CNS to be interpreted, and motor messages which cause a response from the spinal cord to the effector. The *cranial nerves* contain sensory and/or motor fibers. Cranial nerves send messages from receptors to the brain, and take messages from the brain to the effectors. They are numbered from one to twelve (I-XII). Cranial nerves usually receive input from and send messages to structures in the head and neck. For example, cranial nerves pick up sensations about taste, sight, and smell; they send messages to muscles which cause eye movement, facial expression and swallowing. See Appendix A for a more complete description of the cranial nerves. **[Negative Feedback]** A negative feedback mechanism is a response which allows the body to return to a steady state. In other words, when an activity in the body causes an increase in the presence of a certain variable, a negative mechanism will assist the body to remove that variable. Similarly, if there is a deficit in the body of a certain variable, the body will respond in such a way that there is an increase in the presence of that variable. The thermostat in your home is an example of a negative feedback mechanism. You set the temperature in your thermostat at a certain point. That represents homeostasis. When the temperature falls below that temperature the furnace comes on and the temperature in the house rises until it is above the set point. Then the furnace turns off. In that way the temperature in your house stays balanced. There are many similar examples in the body. **[Autonomic Nervous System]** Some peripheral nerves, as well as being sensory or motor, also contain *autonomic nerve fibres* or *neurons.* These neurons send messages to smooth muscle, cardiac muscle, or glands. The *autonomic nervous system (ANS)* has two divisions - the *sympathetic nervous system* and the *parasympathetic nervous system*. 24\. Why is the sympathetic system referred to as the "fight or flight" division? 25\. Why is the parasympathetic system referred to as the "rest and digest" division? The two branches of the autonomic nervous system are in a constant balancing act. At certain times, the sympathetic branch is dominant; at other times, the parasympathetic division is in control, however, neither is ever turned off. The two divisions of the autonomic nervous system are continuously working to maintain a homeostatic internal environment. 26\. Remembering these general effects of each part of the autonomic nervous system, complete the following chart describing the effect of each branch on various organ functions: +-----------------------+-----------------------+-----------------------+ | **Effector** | ### Effect of sympath | Effect of | | ------------ | etic nervous system | parasympathetic | | | | nervous system | +-----------------------+-----------------------+-----------------------+ | heart rate | | | +-----------------------+-----------------------+-----------------------+ | smooth muscle of | | | | bronchi | | | +-----------------------+-----------------------+-----------------------+ | smooth muscle in | | | | blood vessels of | | | | | | | | - abdominal organs | | | | | | | | - skin | | | +-----------------------+-----------------------+-----------------------+ | smooth muscle in | | | | blood vessels of | | | | | | | | - skeletal muscle | | | | | | | | - heart | | | +-----------------------+-----------------------+-----------------------+ | smooth muscle of | | | | digestive tract | | | +-----------------------+-----------------------+-----------------------+ | glands in digestive | | | | tract | | | +-----------------------+-----------------------+-----------------------+ | smooth muscle of | | | | urinary bladder | | | +-----------------------+-----------------------+-----------------------+ | internal sphincter of | | | | urinary bladder | | | +-----------------------+-----------------------+-----------------------+ | blood glucose level | | | +-----------------------+-----------------------+-----------------------+ The sympathetic and parasympathetic divisions of the ANS both *innervate* all of the tissues and organs in the body. Each system uses different *neurotransmitters* at the neuro-effector junction; the *sympathetic nervous system* generally releases *norepinephrine*, while the *parasympathetic* *nervous system* releases *acetylcholine*. Two important words to learn at this time are *adrenergic* and *cholinergic*. *Adrenergic* means "like the sympathetic nervous system". *Cholinergic* means "like the parasympathetic nervous system". These words will be used when learning about drugs which mimic the sympathetic or parasympathetic nervous systems. 27\. Over time, there are changes in the nervous system and the special senses that produce memory lapses, and diminished sensory functioning and motor functioning. Describe the changes of aging in the nervous system that account for slower reflexes and response times, and short-term memory loss. Appendix A ###### **CRANIAL NERVES** +-----------------+-----------------+-----------------+-----------------+ | CRANIAL NERVE | SOMATIC MOTOR | AUTONOMIC MOTOR | SENSORY | | | FUNCTION | FUNCTION | FUNCTION | +-----------------+-----------------+-----------------+-----------------+ | I Olfactory | | | Smell | +-----------------+-----------------+-----------------+-----------------+ | II Optic | | | Vision | +-----------------+-----------------+-----------------+-----------------+ | III Oculomotor | Moves eyelid, | Pupil | | | | eyeball | constriction | | | | | | | | | | Accommodation | | | | | of lens | | +-----------------+-----------------+-----------------+-----------------+ | IV Trochlear | Moves eyeball | | | +-----------------+-----------------+-----------------+-----------------+ | V Trigeminal | Chewing | | Sensations from | | | | | face, nose, | | | | | eyes, mouth | +-----------------+-----------------+-----------------+-----------------+ | VI Abducens | Moves eyeball | | | +-----------------+-----------------+-----------------+-----------------+ | VII Facial | Facial | Lacrimal Glands | Taste | | | expression | - Tears | | | | | | injury called | | | | Salivation | Bell\'s palsy | +-----------------+-----------------+-----------------+-----------------+ | VIII | | | Hearing and | | Vestibulocochle | | | equilibrium | | ar | | | | +-----------------+-----------------+-----------------+-----------------+ | IX | Motor fibers to | Salivation | Taste buds | | Glossopharyngea | tongue and | | | | l | pharynx for | | | | | swallowing | | | +-----------------+-----------------+-----------------+-----------------+ | X Vagus | Motor fibers to | Digestive | Sensation from | | | pharynx & | tract: smooth | organs in the | | | larynx, for | muscle movement | chest and | | | speech and | & glandular | abdomen | | | swallowing | secretions | | | | | | Taste buds | | | | Slows heart | | | | | rate | | | | | | | | | | Constricts | | | | | bronchioles | | +-----------------+-----------------+-----------------+-----------------+ | XI Accessory | Swallowing -- | | | | | larynx, | | | | | pharynx, soft | | | | | palate. | | | | | | | | | | Movement of | | | | | head & neck | | | | | through | | | | | sternocleidomas | | | | | toid | | | | | & trapezius | | | | | muscles | | | +-----------------+-----------------+-----------------+-----------------+ | XII Hypoglossal | Muscles of | | | | | tongue for | | | | | speech | | | +-----------------+-----------------+-----------------+-----------------+