Meeting 1 Nervous System PDF

The Nervous System By: Rahmad Abdillah  Kontrak Perkuliahan 1. Toleransi keterlambatan 10 menit 2. Aktif selama proses perkuliahan a. Mahasiswa yang berinisiatif menjawab pertanyaan akan otomatis memperoleh point keaktifan, termasuk mahasiswa yang bertanya. b. Mahasiswa...

The Nervous System By: Rahmad Abdillah  Kontrak Perkuliahan 1. Toleransi keterlambatan 10 menit 2. Aktif selama proses perkuliahan a. Mahasiswa yang berinisiatif menjawab pertanyaan akan otomatis memperoleh point keaktifan, termasuk mahasiswa yang bertanya. b. Mahasiswa yang ditunjuk untuk menjawab pertanyaan, point keaktifan tergantung ketepatan jawaban 3. Bahan perkuliahan dalam B.Inggris Grading MID SEMESTER EXAM: 50% KEAKTIFAN : 25% TUGAS : 25%  PROFIL Live in Padang Minangnese apt. Rahmad Abdillah., M.Si Education: Magister Pharmacology & Toxicology Affiliation Faculty of Pharmacy 198910242019031014 Universitas Andalas Objective After studying this chapter, you should be able to: Understand the divisions of the nervous system and the parts of each, and state the general functions of the nervous system. Describe the electrical nerve impulse, and describe impulse transmission at synapses. Describe the types of neurons, nerves, and nerve tracts. State the functions of the parts of the brain; be able to locate each part on a diagram Explain how the sympathetic division of the autonomic nervous system enables the body to adapt to a stress situation. Explain how the parasympathetic division of the autonomic nervous system promotes normal body functioning in relaxed situations. Introduction  The nervous system is one of the regulating systems the endocrine, the electrochemical impulses of the nervous system make it possible to obtain information about the external or internal environment and do whatever is necessary to maintain homeostasis. “Some of this activity is conscious, but much of it happens without our awareness” Nervous System Division The nervous system has two divisions. The central nervous system (CNS): consists of the brain and spinal cord. The peripheral nervous system (PNS): consists of cranial nerves and spinal nerves. The PNS includes nerves to and from skin and skeletal muscles. It also includes the autonomic nervous system (ANS)  Nerve Cell Nerve cells are called neurons, or nerve fibers, all neurons have the same physical parts. The cell body contains the nucleus and is essential for the continued life of the neuron. Neuron cell bodies are found in the central nervous system or close to it in the trunk of the body, In these locations, cell bodies are protected by bone. Nerve Impulses The events of an electrical nerve impulse are the same as those of the electrical impulse generated in muscle fibers.  Nerve Impulses Neurons that transmit impulses to other neurons (or to effector cells) do not actually touch one another. The small gap or space between the axon of one neuron and the dendrites or cell body of the next neuron is called the synapse. Within the synaptic knob (terminal end) of the presynaptic axon is a chemical neurotransmitter that is released into the synapse by the arrival of an electrical nerve impulse The neurotransmitter diffuses across the synapse, combines with specific receptor sites on the cell membrane of the postsynaptic neuron, and there generates an electrical impulse that is, in turn, carried by this neuron’s axon to the next synapse, and so forth. Neurotransmitter  Neurotransmitter  Neurotransmitters are chemical messengers that transmit signals from a neuron to a target cell across a synapse.  Target cell may be a neuron or some other kind of cell like a muscle or gland cell.  Necessary for rapid communication in synapse.  Neurotransmitters are packaged into synaptic vesicles - presynaptic side of a synapse Types of Neurotransmitters EXCITATORY INHIBITORY BOTH Glycine Acetylcholine Glutamate GABA Nor epinephrine Aspartate Serotonin Nitric oxide Dopamine TYPES OF NEURONS Neurons are classified into three groups: 1. Sensory neurons Sensory neurons/afferent neurons carry impulses from receptors to the CNS. Receptors detect external or internal changes and send the information to the CNS in the form of impulses by way of the afferent neurons. The central nervous system interprets these impulses as a sensation. 2. Motor neurons/efferent neurons Carry impulses from the CNS to effectors. The two types of effectors are muscles and glands. In response to impulses, muscles contract or relax and glands secrete. Motor neurons linked to skeletal muscle are called somatic. 3. Interneurons Found entirely within the CNS. They are arranged so as to carry only sensory or motor impulses, or to integrate these functions. Some interneurons in the brain are concerned with thinking, learning, and memory.  NERVES AND NERVE TRACTS A nerve is a group of axons and/or dendrites of many neurons, with blood vessels and connective tissue. Sensory nerves are made only of sensory neurons, example: optic nerves for vision and olfactory nerves for smell are examples of nerves with a purely sensory function. Motor nerves are made only of motor neurons; example: autonomic nerves are motor nerves. A mixed nerve contains both sensory and motor neurons. Most of our peripheral nerves, such as the sciatic nerves in the legs, are mixed nerves. The term nerve tract refers to groups of neurons within the central nervous system. All the neurons in a nerve tract are concerned with either sensory or motor activity. These tracts are often referred to as white matter because the myelin sheaths of the neurons give them a white color; this term is used for parts of both the brain and spinal cord. Reflex Arc A reflex arc is the pathway that nerve impulses travel when a reflex is elicited, and there are five essential parts: 1. Receptors—detect a change (the stimulus) and generate impulses. 2. Sensory neurons—transmit impulses from receptors to the CNS. 3. Central nervous system—contains one or more synapses (interneurons may be part of the pathway). 4. Motor neurons—transmit impulses from the CNS to the effector. 5. Effector—performs its characteristic action. For example : the Patellar reflex Flexor reflexes Known as withdrawal reflexes Another type of spinal cord reflex for stimulus that is something painful and potentially harmful, and the response is to pull away from it. Example: If you inadvertently touch a hot stove, Flexor reflexes are three-neuron reflexes because sensory neurons synapse with interneurons in the spinal cord, which in turn synapse with motor neurons. Again, however, the brain does not have to make a decision to protect the body; the flexor reflex does that automatically The Brain The Brain The brain is made of approximately 100 billion neurons and contains trillions of synapses, all of which function as an integrated whole. The major parts of the brain are: Medulla, Pons, Midbrain (collectively called the brainstem), the cerebellum, the hypothalamus, the thalamus, the cerebrum. All of these part are interconnected, by way of those trillions of synapses, and work together. The Brain All part of the brain will be discussed in this section: VENTRICLES The ventricles are four cavities within the brain: two lateral ventricles, the third ventricle, and the fourth ventricle. The ventricles are lined with ciliated ependymal cells and filled with cerebrospinal fluid (CSF). Cerebrospinal fluid is the tissue fluid of the central nervous system. The Brain MEDULLA The medulla extends from the spinal cord to the pons and is anterior to the cerebellum. Its functions to regulate the “vital signs”. The medulla contains cardiac centers that regulate heart rate, vasomotor centers that regulate the diameter of blood vessels and, thereby, blood pressure, and respiratory centers that regulate breathing. Human cannot survive without the medulla, because medulla also in the medulla are reflex centers for coughing, sneezing, swallowing, and vomiting. PONS Within the pons are two respiratory centers that work with those in the medulla to produce a normal breathing rhythm. The many other neurons in the pons (pons is from the Latin for “bridge”) connect the medulla with other parts of the brain. The Brain MIDBRAIN The midbrain extends from the pons to the hypothalamus and encloses the cerebral aqueduct, a tunnel that connects the third and fourth ventricles. Several different kinds of reflexes are integrated in the midbrain, including visual and auditory reflexes. The ability to read depends in part on the coordinated movement of the eyeballs from word to word; this is scanning and is another reflex mediated by the midbrain. CEREBELLUM The cerebellum is separated from the medulla and pons by the fourth ventricle and is inferior to the occipital lobes of the cerebrum. The functions of the cerebellum are concerned with movement. These include coordination, regulation of muscle tone, the appropriate trajectory and end point of movements, and the maintenance of posture and equilibrium. The Brain HYPOTHALAMUS Located superior to the pituitary gland and inferior to the thalamus, the hypothalamus is a small area of the brain with many diverse functions: 1. Production of antidiuretic hormone (ADH) and oxytocin; these hormones are then stored in the posterior pituitary gland. ADH enables the kidneys to reabsorb water back into the blood and thus helps maintain blood volume. Oxytocin causes contractions of the uterus to bring about labor and delivery. 2. Production of releasing hormones (also called releasing factors) that stimulate the secretion of hormones by the anterior pituitary gland. The hypothalamus produces growth hormone–releasing hormone (GHRH), which stimulates the anterior pituitary gland to secrete growth hormone (GH). 3. Regulation of body temperature by promoting responses such as sweating in a warm environment or shivering in a cold environment. 4. Regulation of food intake; the hypothalamus is believed to respond to changes in blood nutrient levels, to chemicals secreted by fat cells, and to hormones secreted by the gastrointestinal tract. For example, during a meal, after a certain duration of digestion, the small intestine produces a hormone that circulates to the hypothalamus and brings about a sensation of satiety, or fullness, and we tend to stop eating. 5. Integration of the functioning of the autonomic nervous system, which in turn regulates the activity of organs such as the heart, blood vessels, and intestines. The Brain 6. Stimulation of visceral responses during emotional situations. When we are angry, heart rate usually increases. Most of us, when embarrassed, will blush, which is vasodilation in the skin of the face. These responses are brought about by the autonomic nervous system when the hypothalamus perceives a change in emotional state. The neurologic basis of our emotions is not well understood, and the visceral responses to emotions are not something most of us can control. 7. Regulation of body rhythms such as secretion of hormones, sleep cycles, changes in mood, or mental alertness. This is often referred to as our biological clock, the rhythms as circadian rhythms, meaning “about a day.” If you have ever had to stay awake for 24 hours, you know how disorienting it can be, until the hypothalamic biological clock has been reset The Brain CEREBRUM The largest part of the human brain, which consists of two hemispheres separated by the longitudinal fissure. At the base of this deep groove is the corpus callosum, a band of 200 million neurons that connects the right and left hemispheres. The cerebral cortex is divided into lobes that have the same names as the cranial bones external to them. Therefore, each hemisphere has a frontal lobe, parietal lobe, temporal lobe, and occipital lobe. These lobes have been mapped; that is, certain areas are known to be associated with specific functions The Brain Parietal Lobes Temporal Lobes The olfactory areas in the temporal lobes receive impulses from The general sensory areas in receptors in the nasal cavities for the sense of smell. The olfactory the parietal lobes receive association area learns the meaning of odors such as the smell of sour milk, impulses from receptors in the skin and feel and interpret the or fire, or brownies baking in the oven, and enables the thinking cerebrum cutaneous sensations. The left to use that information effectively. area is for the right side of The auditory areas, as their name suggests, receive impulses from the body and vice versa. The receptors in the inner ear for hearing. Part of it is concerned with the largest portions of these meanings of words we hear. Other parts are for the interpretation of areas are for sensation in the sounds such as thunder during a storm, an ambulance siren, or a baby hands and face, crying. Without proper interpretation, we would hear the sound but would not know what it meant or be able to integrate it with other senses and could not respond appropriately. Occipital Lobes Impulses from the retinas of the eyes travel along the optic nerves to the visual areas in the occipital lobes. These areas “see.” The visual association areas interpret what is seen and enable the thinking cerebrum to use the information. The Brain Basal Ganglia The basal ganglia are paired masses of gray matter within the white matter of the cerebral hemispheres. Their functions are certain subconscious aspects of voluntary movement, and they work with the cerebellum. The basal ganglia help regulate muscle tone, and they coordinate accessory movements such as swinging the arms when walking or gesturing while speaking. Gestures and facial expressions. The most common disorder of the basal ganglia is Parkinson’s disease Corpus Callosum As mentioned previously, the corpus callosum is a band of nerve fibers that connects the left and right cerebral hemispheres. This enables each hemisphere to know what the other is doing. The Brain The Brain MENINGES AND CEREBROSPINAL FLUID The connective tissue membranes that cover the brain and spinal cord are called meninges. The thick outermost layer, made of fibrous connective tissue, is the dura mater (Latin for “tough mother”), which lines the skull and vertebral canal. The middle arachnoid membrane (arachnids are spiders) is made of web-like strands of connective tissue. The innermost pia mater (Latin for “gentle mother”) is a very thin membrane on the surface of the spinal cord and brain. Between the arachnoid and the pia mater is the subarachnoid space, which contains cerebrospinal fluid (CSF), the tissue fluid of the central nervous system Thank You