Nervous-Structures-and-the-Nervous-System (1).pdf

MODULE 2: Coordination and Control Christine Cherry E. Solon, Ph.D. COORDINATION and CONTROL Organisms respond to stimuli. That is one of the characteristics of life, referred to as responsiveness or irritability. The simplest unicellular living forms can already...

MODULE 2: Coordination and Control Christine Cherry E. Solon, Ph.D. COORDINATION and CONTROL Organisms respond to stimuli. That is one of the characteristics of life, referred to as responsiveness or irritability. The simplest unicellular living forms can already react appropriately to stimuli. Since this ability is already inherent in the cell, multicellular structures that are formed when these cells group together can produce more specialized functions that separate cells cannot do by themselves. Department of Biological Sciences, College of Science and Mathematics 1  COORDINATION and CONTROL Invertebrates are animals without backbone. They do not really have intricate nervous systems; they have simple nervous structures enough to make them capable of responding to stimuli. Cnidarians and sponges have structures that do not have associative activity Flatworms are the first animals to have one. These structures help them survive in their respective habitats. Fig. 1. Nervous Structures of some invertebrates. Department of Biological Sciences, College of Science and Mathematics 2 COORDINATION and CONTROL Fig. 2. Closer look at the nervous structures of some invertebrates. Arthropod nervous systems resemble that of annelids but ganglia are larger and sense organs are more developed. Department of Biological Sciences, College of Science and Mathematics 3 COORDINATION and CONTROL In vertebrates, coordination and control are functions of the nervous and endocrine systems. Both systems are composed of various organs. The main type of tissue comprising the vertebrate nervous system is the nervous tissue. This is based on the main functions of the system itself. The endocrine system will be discussed later, in part 2. Department of Biological Sciences, College of Science and Mathematics 4 COORDINATION and CONTROL: The Nervous System The nervous tissue is one of the types of somatic tissues in the animal body. They grow by undergoing mitosis. The nervous system is composed of cells called neurons and neuroglia. The former comprise about 10% of the total number of cells of the nervous system while the latter make up the rest. Fig. 3. The cells of the vertebrate nervous system. Source: https://www.quora.com/Which-one-is-larger-a-neuroglial-cell-or-a- nerve-cell Department of Biological Sciences, College of Science and Mathematics 5  COORDINATION and CONTROL: The Nervous System Neuroglia or glial cells are special cells associated with neurons. They come in many different types, and they perform many different functions. FUNCTIONS: 1. support for the brain (physically) 2. assist in nervous system repair and maintenance (prune neurons) 3. assist in the development of the nervous system Fig. 4. Types of neuroglia. Take note of how they 4. provide metabolic functions for associate with a neuron. neurons (attach them to blood vessels) Department of Biological Sciences, College of Science and Mathematics 6 COORDINATION and CONTROL: The Nervous System Types of Neuroglia: Microglia are small, ovoid phagocytes that monitor the health of neurons. Astrocytes are the most abundant; they are highly branched. They cling to neurons and their synaptic endings, and cover capillaries. Fig. 5. Microglia and astrocytes. Source: https://jonlieffmd.com/wp-content/uploads/2013/12/fig_3.gif Department of Biological Sciences, College of Science and Mathematics 7 COORDINATION and CONTROL: The Nervous System Types of Neuroglia: Oligodendrocytes are glial cells that have processes that wrap around the nerve fibers of the central nervous system. Fig. 6. Oligodendrocytes Schwann cells wrap around the & Schwann cells. nerve fibers of the peripheral nervous system. Both of them produce or form myelin sheath. Department of Biological Sciences, College of Science and Mathematics 8  COORDINATION and CONTROL: The Nervous System Ependymal cells are glial cells which are Types of Neuroglia: ciliated squamous to columnar, and which line central CSF-filled cavities of brain and Satellite cells are glial cells that spinal cord. They play an active role in surround and support neuron moving cerebrospinal fluid (CSF). cell bodies in the peripheral nervous system ganglia. Fig. 7. Ependymal cells. Fig. 8. Satellite cells Source: http://medical-dictionary.thefreedictionary.com/ Department of Biological Sciences, College of Science and Mathematics 9 COORDINATION and CONTROL: The Nervous System Take note of how the peripheral nervous system (PNS) and the central nervous system (CNS) differ in the types of glial cells that they have. Fig 9. The glial cells of the PNS and CNS. Department of Biological Sciences, College of Science and Mathematics 10 COORDINATION and CONTROL: The Nervous System Neuron or nerve cell: the basic structural and functional unit of the nervous system electrically excitable unusually long compared to other cell types; even considered longest cells in some cases Function: transmission of nerve impulse Fig. 10. The neuron. Department of Biological Sciences, College of Science and Mathematics 11 COORDINATION and CONTROL: The Nervous System Parts of a myelinated neuron: 1. cell body or soma or perikaryon or cyton - contains the nucleus and others 2. dendrites – short, branched, processes extending from cell body; they carry impulses toward the cell body 3. axon – long process extending from cell body; carries impulses away from the cell body 4. node of Ranvier – gap in the myelin sheath Fig. 11. A myelinated neuron. between adjacent Schwann cells or The light blue lipid material that is wrapped around the oligodendrocytes; present in myelinated neurons axon is produced by the Schwann cell and is called myelin sheath. Department of Biological Sciences, College of Science and Mathematics 12  COORDINATION and CONTROL: The Nervous System More than 99% of neurons are multipolar. Fig. 12. Types of neuron according to structure. Department of Biological Sciences, College of Science and Mathematics 13  COORDINATION and CONTROL: The Nervous System Types of Neurons according to function: 1. sensory neurons or afferent neurons - neurons from receptor cells 2. motor or efferent neurons - neurons to effectors 3. interneurons or associative neurons or intermediate Neurons - connect sensory to motor neurons Fig. 13. Functional types of neurons. Source: https://www.ncbi.nlm.nih.gov/books/ NBK21535/figure/A6110/ Department of Biological Sciences, College of Science and Mathematics 14 COORDINATION and CONTROL: The Nervous System The resting neuron is in a polarized state (net positive charge outside and net negative charge inside). It has a resting membrane potential of -70 to -60 millivolts. (The outside is 70-60 mv positive relative to the inside or the inside is 70-60 mv negative relative to the outside.) The resting membrane potential is the potential difference across the membrane of a resting neuron. It is brought about by the concentration difference of positively-charged and negatively-charged ions in the extracellular and intracellular fluids. In a resting neuron, the Na+-K+ pump actively transports 3 Na+ out in exchange for 2 K+ that it pumps in. There Fig. 14. A resting neuron. Note that are K+ leak channels that allow outward diffusion of K+. there is higher concentration of Na+ outside and more K+ inside. Department of Biological Sciences, College of Science and Mathematics 15 COORDINATION and CONTROL: The Nervous System Key Na+ Sodium- Potassium Resting potassium Sodium K+ pump channel channel membrane OUTSIDE potential is CELL generated by the OUTSIDE [K+] CELL 5 mM Na+ 150 mM [Cl–] 120 mM different INSIDE K + [Na+] [A–] concentrations mM [Cl–] CELL 140 mM 15 10 mM 100 mM INSIDE of Na+, K+, Cl- CELL and protein (a) (b) anions (A-). Fig. 15. The basis of membrane potential. Remember the role of the Na+-K+ pump in maintaining the polarization of the neuron. Department of Biological Sciences, College of Science and Mathematics 16 COORDINATION and CONTROL: The Nervous System When a stimulus is applied to a neuron, the plasma membrane at the point of stimulation undergoes permeability changes. This changes the direction of transport of ions across the membrane. Na+ channels on the membrane allows diffusion of Na+ into the cell (1) causing depolarization of the membrane at that portion (+ charge inside, - charge outside). This is followed by K+ channels facilitating the diffusion of K+ outward (2). This leads to the repolarization at that part (+ charges outside and – charges inside). This action potential is self- propagating, thus it will continue towards the end of the neuron. Fig. 16. Nerve impulse transmission along a neuron. Department of Biological Sciences, College of Science and Mathematics 17 COORDINATION and CONTROL: The Nervous System Phases of Action Potential: 1. Resting (polarized) phase: -70 to -60 mv - voltage-dependent ion channels closed 2. Depolarizing phase: - Entry of Na ions until Na channels are inactivated 3. Repolarizing phase: - Na channels still inactive - K ions continuously move out (K channels all open) till the outside becomes positive 4. Hyperpolarizing phase: due to excess exit of K ions Department of Biological Sciences, College of Science and Mathematics 18 COORDINATION and CONTROL: The Nervous System Fig. 17. Synaptic transmission. These are the series of events that happen as the wave of action potential sweeps along the axon, reaches the axon terminal and is transmitted across the synaptic gap or synaptic cleft or simply synapse via checmical transmitters, on to the next cell, which could be another neuron. Department of Biological Sciences, College of Science and Mathematics 19 COORDINATION and CONTROL: The Nervous System If the gap after the axon terminal is a neuromuscular junction, the neurotransmitter (e.g. acetycholine) is released into the gap and will stimulate the membrane of the effector (reacting organ), which in this case, is a skeletal muscle. Just like what was shown in the synaptic transmission, there will be stimulation of the ion channels of the muscle tissue which will ultimately lead to the response of the muscle which is muscle contraction. This will be followed up in the discussion of muscle contraction in the next Fig. 18. The neuromuscular junction is a small gap between the axon of a neuron and module. the membrane of the muscle cell. Transmission of impulses across this gap is through chemical transmitters. Department of Biological Sciences, College of Science and Mathematics 20 COORDINATION and CONTROL: The Nervous System Neurotransmitters are brain chemicals that communicate information throughout our brain and body. They relay signals between nerve cells and between nerve cells and effectors. Excitatory neurotransmitters: Inhibitory neurotransmitters: Dopamine Dopamine Glutamate Serotonin Acetylcholine Gamma-Amino Butyric Acid Norepinephrine Epinephrine Department of Biological Sciences, College of Science and Mathematics 21  COORDINATION and CONTROL: The Nervous System Factors that affect rate of impulse conduction: 1. electrical properties of the axon plasma membrane large neurons (e.g. in squid) have low resistance so ion currents are fast, impulses go fast small neurons have higher resistance so ion currents are slower, impulses are slower Fig. 19. Axons with larger diameter conduct impulses faster. Yellow portion represents myelin sheath. The red fiber is non-myelinated. Source: https://faculty.washington.edu/chudler/cv.html Department of Biological Sciences, College of Science and Mathematics 22 COORDINATION and CONTROL: The Nervous System Factors that affect rate of impulse conduction: 2. distance between nodes of Ranvier (myelin sheath) Nerve impulse conduction is faster in myelinated neuron than in non-myelinated neuron. The farther the nodes are from each other, the faster the nerve impulse will travel because it follows a saltatory type of conduction. See how the two types of neurons differ by looking at the time and how far along the Fig. 20. How myelination of a neuron affects axon has the action potential travelled. the rate of nerve impulse transmission. source: slidepayer.com Department of Biological Sciences, College of Science and Mathematics 23 COORDINATION and CONTROL: The Nervous System Nerve – group of nerve fibers outside CNS A nerve tissue is formed when Ganglion – group of cell bodies outside CNS cells of the nervous system are Tract – group of nerve fibers within CNS grouped together. Because of Nucleus – group of cell bodies within CNS the unique shape, cell bodies tend to group together while nerve fibers (axons and dendrites) also group together. The tissues formed are named differently, whether they can be a b found within or outside of the brain and spinal cord. Fig. 21. (a) Ganglion versus nucleus, and (b) tracts versus nerves. Department of Biological Sciences, College of Science and Mathematics 24 SELF-CHECK: 1. The concentration of potassium on the inside of a nerve cell membrane is higher than the concentration of sodium on the outside of the membrane. Yet the inside of the membrane (where the cation concentration is higher) is negative to the outside. Explain this observation in terms of the permeability properties of the membrane. 2. What ionic and electrical changes occur during the passage of an action potential along a nerve fiber? 3. ________ is released by motor nerve endings onto muscle. a. Acetylcholine b. Norepinephrine c. Dopamine d. Serotonin 4. A(n) ________ neuron has one axon and one dendrite extending directly from the cell body. a. unipolar b. bipolar c. multipolar d. pseudounipolar 5. How are neurons similar to other cells? How are they unique? 25 COORDINATION and CONTROL: The Nervous System Definition of terms: STIMULUS - any physical or chemical change capable of exciting an organism or its parts RECEPTOR - a cell or organ having a special sensitivity to some particular kind/kinds of stimuli EFFECTOR - cell, tissue or organ which reacts to stimuli Department of Biological Sciences, College of Science and Mathematics 26 COORDINATION and CONTROL: The Nervous System CENTRAL NERVOUS PERIPHERAL NERVOUS SYSTEM (CNS) SYSTEM (PNS) Anatomic Divisions Spinal SOMATIC NERVOUS AUTONOMIC NERVOUS brain cord SYSTEM (SNS) SYSTEM (ANS) Physiologic Divisions PARASYMPATHETIC SYMPATHETIC NERVOUS NERVOUS SYSTEM SYSTEM Fig. 22. Divisions of the Vertebrate Nervous System. CNS and PNS are anatomic divisions because their names are based on their location in the body. SNS and ANS are the physiologic divisions because they are named based on their functions. Department of Biological Sciences, College of Science and Mathematics 27 COORDINATION and CONTROL: The CNS Central Nervous System Components: brain and spinal cord General function: serves as information processing center and central command post Fig. 23. The components of the CNS. Department of Biological Sciences, College of Science and Mathematics 28  COORDINATION and CONTROL: The CNS The BRAIN is protected by the cranium and the spinal cord is protected by the vertebral column. Under the bones as 3 membranes called meninges (dura mater, arachnoid mater and pia mater). The spaces between meninges and the cavities within the CNS are filled with cerebrospinal fluid (CSF), which also serves as Fig. 24. Bones, meninges and CSF provide protection to the CNS. shock absorber. Department of Biological Sciences, College of Science and Mathematics 29  COORDINATION and CONTROL: The CNS There are 3 divisions of the brain: Forebrain Midbrain Hindbrain Each is shown in the picture as composed of specific parts. Only the major parts are labelled. The embryonic brain has 3 divisions. The adult brain has 5 divisions because the forebrain and hindbrain subdivide. Fig. 25. The divisions and major parts of the brain. The parts of the brain will be studied with reference to the 3 original divisions. Department of Biological Sciences, College of Science and Mathematics 30 COORDINATION and CONTROL: The CNS The Forebrain The CEREBRUM is the largest part of the brain. It controls somatosensory, motor, language, cognitive thought, memory, emotions, hearing, and vision. The cerebrum is divided into the left and right hemispheres by a deep longitudinal fissure; the two hemispheres remain in contact and in communication with one another by the corpus callosum. Each hemisphere further subdivides into a frontal, parietal, occipital, and Fig. 26. The corpus callosum, a wide thick nerve tract temporal lobe. Each lobe carries out different connecting the 2 functions. cerebral hemispheres. Department of Biological Sciences, College of Science and Mathematics 31 COORDINATION and CONTROL: The CNS Interpretation of what is perceived is a function of the cerebrum. Fig. 27. The lobes of the cerebral cortex and their functions. Source: https://ib.bioninja.com.au/options/option-a-neurobiology-and/a2-the-human-brain/brain- sections.html Department of Biological Sciences, College of Science and Mathematics 32  COORDINATION and CONTROL: The CNS Function of thalamus: acts as relay station for impulses travelling to and from spinal cord, brainstem, cerebellum and cerebrum Functions of hypothalamus: 1. monitors water concentration, hormone concentrations and body temperature 2. associated with feelings of rage, aggression, hunger and thirst. 3. plays an important role as an intermediary between the nervous system and the Fig. 28. The thalamus is located on top of endocrine system the hypothalamus. Both are parts of the forebrain, largely covered by the cerebral hemispheres. Department of Biological Sciences, College of Science and Mathematics 33 COORDINATION and CONTROL: The CNS Functions of amygdala: 1. involved in the processing of emotions such as fear, anger and pleasure 2. determines what memories are stored and where the memories are stored in the brain Functions of hippocampus: 1. Formation, storage and organization of new autobiographical and fact memories 2. Emotional responses Fig. 29. The Limbic System. It is composed of 3. Navigation parts of the forebrain, including the 4. Spatial orientation hypothalamus , amygdala and hippocampus. Department of Biological Sciences, College of Science and Mathematics 34 COORDINATION and CONTROL: The CNS The Midbrain is the small region of the brain that connects the forebrain with the hindbrain. Though small, it is so important as it allows continuity of relay of information from the forebrain to the hindbrain or in the opposite direction. Main parts/functions of midbrain: 1. Superior colliculi (vision) 2. Inferior colliculi (hearing) 3. Tegmentum (consciousness) 4. Cerebral peduncle (motor function) Fig. 30. The parts of the midbrain. 5. Red nucleus (motor function) 6. Substantia nigra (motor function) Department of Biological Sciences, College of Science and Mathematics 35  COORDINATION and CONTROL: The CNS The TheHindbrain HINDBRAIN is the most posterior region of the brain. One of its parts is the cerebellum, the second largest part of the brain. Functions of the cerebellum: helps control posture and balance coordinates voluntary movements Functions of the pons: serves as a bridge between the cerebellar hemispheres also involved in production of chemicals the body needs for sleep Functions of the medulla oblongata: controls breathing, heart rate, and a variety of reflexes relay of nerve signals between the brain and spinal cord Fig. 31. The Hindbrain. Dorsal is the coordination of body movements cerebellum. Ventral are the pons Function of reticular formation: and medulla oblongata. The reticular formation can only be acts as regulatory system for sleep, waking, and alertness seen in sections like in this picture. Department of Biological Sciences, College of Science and Mathematics 36 COORDINATION and CONTROL: The CNS The brainstem is composed of the midbrain, pons and medulla oblongata. It contains centers that regulate several functions that are vital for survival, which include blood pressure, heartbeat, respiration, digestion, and certain reflex actions such as swallowing and Fig. 32. The Brainstem controls vital vomiting. processes of the body. Department of Biological Sciences, College of Science and Mathematics 37 COORDINATION and CONTROL: The CNS The SPINAL CORD is an elongate tube that extends from the base of the brain to the lumbar region of the vertebral column. It is protected by the vertebral column, meninges and CSF. a Functions of the spinal cord: connects brain with PNS controls responses that do b not involve the brain (e.g. Fig. 33. The spinal cord provides continuity of relay reflex act) of information from the lower parts of the body to the brain (a). Like the brain it is protected by bones, membranes and fluid (b). Department of Biological Sciences, College of Science and Mathematics 38 COORDINATION and CONTROL: The CNS Reflexes or reflex acts are immediate responses to stimuli. The response is so quick that the person only realizes what happened after the instant act has been done. It is protective in nature and it is mediated by the spinal cord. A reflex act follows a path called a reflex arc, which always starts with a receptor and involves message relay from sensory neuron to interneuron to motor neuron to effector. Fig. 34. A reflex arc. The stimulus is pain from a needle which pricked the skin. It is felt by the sensory neurons (skin receptors) which transmit nerve impulses to the spinal cord (blue line). Within the spinal cord are interneurons that relay the impulses to the motor neurons which innervate the effector (skeletal muscle), which contracts and withdraws the skin from the needle. Department of Biological Sciences, College of Science and Mathematics 39 COORDINATION and CONTROL: The CNS b a Fig. 35. Examples of spinal reflexes. (a) The stimulus is heat that is felt by the skin receptors which started a cascade of nerve transmission to the spinal cord (green line) which proceeds to the muscles of the arm which is the effector (blue line) ending with the quick withdrawal of the finger from the heat. (b) The knee- jerk reflex (forward movement of the lower leg) is generated from tapping of the patellar tendon in the knee with a reflex hammer. Department of Biological Sciences, College of Science and Mathematics 40  COORDINATION and CONTROL: The CNS Regions of the brain and spinal cord: Notice how the brain and spinal cord differ White matter – dense collections of in terms of where the white matter and myelinated fibers gray matter are located. Gray matter – mostly soma and unmyelinated fibers Fig. 36. Cross section of the brain (a), and spinal a b cord (b). Department of Biological Sciences, College of Science and Mathematics 41 COORDINATION and CONTROL: The PNS Components of the PNS: Cranial nerves (12 pairs) arise from the surface of the brain. Spinal nerves (31 pairs) arise from the spinal cord. Fig. 37. The peripheral nerves. Department of Biological Sciences, College of Science and Mathematics 42 COORDINATION and CONTROL: The PNS Fig. 38. The cranial nerves, their functions and the organs that they innervate. Note that some are purely sensory, some are purely motor in function while some perform both sensory and motor functions. Sensory cranial nerves arise from the surface of the brain and innervate sense organs. Motor cranial nerves innervate effectors. While those which have mixed functions can cause sensation as well as responses like movements and/or secretion. Department of Biological Sciences, College of Science and Mathematics 43  COORDINATION and CONTROL: The PNS a b c Fig. 39. The trigeminal nerve is the largest cranial nerve (a); vagus nerve is the longest (b); and olfactory nerve is the shortest (c). Department of Biological Sciences, College of Science and Mathematics 44 COORDINATION and CONTROL: The PNS Spinal nerves connect the spinal cord to the different parts of the body. They are named by region: cervical nerves (8 pairs) thoracic nerves (12 pairs) lumbar nerves (5 pairs) sacral nerves (5 pairs) coccygeal nerves (1 pair) Fig. 40. The spinal nerves are named according to the region of the spinal cord where they arise. Department of Biological Sciences, College of Science and Mathematics 45 COORDINATION and CONTROL: The PNS As shown by the involvement of the cranial and spinal nerves in both sensory and motor functions, we can imagine how it is possible for signals to travel to the CNS from receptors and from CNS to effectors. However, it is not possible for all of the processes to be under the direct control of the cerebrum since that would mean more energy expenditure. Thus, the motor division of the PNS is divided into an Autonomic Fig. 41. The divisions of the PNS. The motor division is divided into an SNS which Nervous System and a Somatic Nervous controls all voluntary movements and an System. Only the latter is under conscious ANS which takes care of involuntary control. responses. Source: https://ib.bioninja.com.au/ options/option-a-neurobiology-and/a2-the-human-brain/brain- sections.html Department of Biological Sciences, College of Science and Mathematics 46  COORDINATION and CONTROL: The PNS > ANS Fig. 42. The divisions of the ANS. The ANS, referred to as ‘the system that never sleeps,’ is composed of nerves which have opposite effects on various parts of the body involved in involuntary activities. It is composed of a Parasympathetic and Sympathetic Nerves. The former is composed of cranial and sacral nerves (cranio- sacral), and referred to here as having a “rest and digest” effect. The latter is composed of thoracic and lumbar nerves (thoracolumbar) and has a “fight or flight” effect. Note that what one stimulates, the other inhibits. In other words, they correct each other, making sure that only necessary activities should be allowed. Department of Biological Sciences, College of Science and Mathematics 47 COORDINATION and CONTROL: The PNS > ANS Fig. 43. The divisions of the Autonomic Nervous System and how their proper functioning is responsible for attaining homeostasis. The seesaw presentation reflects their alternate functioning since they regulate each other. Department of Biological Sciences, College of Science and Mathematics 48 COORDINATION and CONTROL: The PNS > SNS In contrast with ANS, the Somatic Nervous system controls voluntary responses like skeletal muscle contraction. Whenever you move, you know it!!! Functions: 1. controls the exchange of information between receptors, CNS and the skeletal muscle 2. controls all voluntary responses Fig. 44. The SNS controls skeletal muscles which are voluntary muscles. Department of Biological Sciences, College of Science and Mathematics 49  COORDINATION and CONTROL: The PNS > SNS Fig. 45. How SNS controls the activities of skeletal muscles (somatic-motor) and the responses of sense organs (somatic-sensory). Note that for both of these, the response is known to the organism. The person is aware that there is movement and what kind of movement is produced. The person is aware of the sensation and can identify it but much later since the response has already taken place (as mediated by the spinal cord) before the interpretation is produced by the brain. Department of Biological Sciences, College of Science and Mathematics 50 COORDINATION and CONTROL: The Nervous System Disorders of the Nervous System > Neurodegenerative disorders: Fig. 46. Alzheimer’s disease is the most common cause of dementia in the elderly. Department of Biological Sciences, College of Science and Mathematics 51 COORDINATION and CONTROL: The Nervous System Disorders of the Nervous System > Neurodegenerative disorders: Fig. 47. Parkinson’s disease, a neurogenerative disease, involving neurons that release dopamine. Source: https://parkinsonsnebraska.org/understanding-parkinsons-disease/ Department of Biological Sciences, College of Science and Mathematics 52  COORDINATION and CONTROL: The Nervous System Disorders of the Nervous System > Neurodevelopmental disorders: a Fig. 48. Characteristics of persons having (a) ASD and (b) ADHD. Both conditions are more prevalent in b males. Department of Biological Sciences, College of Science and Mathematics 53 COORDINATION and CONTROL: The Nervous System Disorders of the Nervous System > Mental illnesses: Fig. 49. Schizophrenia and depression. Schizophrenia is a serious and often debilitating mental illness. Depression is one of the most common mental disorders. Department of Biological Sciences, College of Science and Mathematics 54 SELF-CHECK: 1. The ________ lobe contains the visual cortex. a. frontal b. parietal c. temporal d. occipital 2. The ________ connects the two cerebral hemispheres. a. limbic system b. corpus callosum c. cerebellum d. pituitary 3. Neurons in the ________ control motor reflexes. a. Thalamus b. spinal cord c. parietal lobe d. hippocampus 4. Activation of the sympathetic nervous system causes: a. increased blood flow into the skin c. an increased heart rate b. a decreased heart rate d. increased digestion 5. Parkinson’s disease is a caused by the degeneration of neurons that release ________. a. Serotonin b. dopamine c. glutamate d. norepinephrine 55 COORDINATION and CONTROL RECEPTORS are cells, tissues or organs having a special sensitivity to some particular stimulus. They act as transducers, converting the energy of a stimulus into the electrochemical energy of a nerve impulse. There are 2 ways to classify receptors: based on location or source of stimulus and based on the type of stimulus that they can detect. Department of Biological Sciences, College of Science and Mathematics 56 COORDINATION and CONTROL A. Types of receptors according to B. source (location) of stimulus: 1. Exteroceptors – sensitive to stimuli from external environment 2. Interoceptors – sensitive to stimuli from internal environment 3. Proprioceptors – sensitive to both external and internal stimuli and are responsible for relaying information about our body's spatial position to the brain (muscle length and tension, limb position) Baroreceptors are sensitive to pressure changes and are considered mechanoreceptors. Department of Biological Sciences, College of Science and Mathematics 57  COORDINATION and CONTROL: Sense Organs a b Sense Organs are sites of sensory receptors which Fig. 50. (a) Exteroceptors and (b) interoceptors. collect information from the external environment and relay it to the NS then to the effectors. Department of Biological Sciences, College of Science and Mathematics 58 COORDINATION and CONTROL: Sense Organs SKIN: sense of touch Fig. 51. Skin receptors. Take note that there are receptors that are situated close to the surface (outer part of dermis) and those that are located in the deeper parts. Department of Biological Sciences, College of Science and Mathematics 59  COORDINATION and CONTROL: Sense Organs Cutaneous (skin) receptors are located within the skin or underlying tissues. Free nerve endings: sensitive to heat, cold or pain (thermoreceptors, nociceptors and mechanoreceptors). Meissner’s corpuscles (tactile corpuscles): respond to touch and low-frequency vibration. Ruffini endings: detect stretch, deformation with joints, and warmth (sensitive to pressure). Root hair plexus: very sensitive mechanoreceptor for touch that is located at the base of the hair. Pacinian corpuscle: the largest skin receptor, very quick to adapt to skin displacement (sensitive to pressure). Krause end bulbs: mechanoreceptors, sensitive to cold, more superficially located than Ruffini endings Fig. 52. Skin receptors. Merkel’s disks: located superficially in the dermis, react slowly to pressure (sustained pressure) Department of Biological Sciences, College of Science and Mathematics 60 COORDINATION and CONTROL: Sense Organs Problems in sensation involving skin: Anesthesia – total or partial loss of feeling Paresthesia – sensation of pricking and tingling followed by numbness Hyperesthesia – An abnormal or pathological increase in sensitivity to sensory stimuli, as of the skin to touch Analgesia - a deadening or absence of the sense of pain without loss of consciousness Hyperalgesia - exaggerated sense of pain Based on your own observations, what proof can you provide to support the fact that mechanoreceptors are not evenly distributed in the skin? Department of Biological Sciences, College of Science and Mathematics 61 COORDINATION and CONTROL: Sense Organs EYE: sense of sight Fig. 53. Parts of the human eye. Department of Biological Sciences, College of Science and Mathematics 62 COORDINATION and CONTROL: Sense Organs The EYE is composed of: - 3 distinct layers of tissue: 1. Fibrous coat 2. Vascular coat 3. Retina, and - a lens Fig. 54. Longitudinal section of the eye, showing the lens and the 3 layers of tissue. Department of Biological Sciences, College of Science and Mathematics 63 COORDINATION and CONTROL: Sense Organs Layers of the Eye: FIBROUS COAT - thick fibrous connective tissue that forms the outer layer of the eyeball Parts: Sclera – the white of the eye Cornea – the transparent front part; covered by a thin conjunctiva Fig. 55. Longitudinal section of the eye. The parts of the fibrous coat are underlined. Department of Biological Sciences, College of Science and Mathematics 64 COORDINATION and CONTROL: Sense Organs Layers of the Eye: VASCULAR COAT - the highly vascular, opaque and incomplete layer between the retina and the sclera Parts: Choroid – pigmented part at the back of the eyeball that is rich in blood vessels Ciliary body - layer inner to the junction of sclera and cornea; has muscles that control the size of the eyeball Iris – the colored part of the eye; has a pupil and Fig. 56. Longitudinal section of the eye. muscles (radial and circular) that regulate The parts of the vascular coat are the diameter of the pupil underlined. Department of Biological Sciences, College of Science and Mathematics 65 COORDINATION and CONTROL: Sense Organs The pupil is the opening (circular black area) in the center of the iris. Its diameter changes in response to light. Observe a cat’s pupils under bright light. Do they look the same as the pupils of humans? Why or why Fig. 57. Pupillary changes in response to light. The not? increase or decrease in the diameter of the pupil is caused by the contraction of the muscles of the iris. Department of Biological Sciences, College of Science and Mathematics 66 COORDINATION and CONTROL: Sense Organs LENS - biconvex, circular, transparent structure behind the pupil - an elastic structure; its shape can be varied to adjust to objects at varying distances The lens is held in place with the help of ligament called the suspensory ligament. Function of LENS: serves to focus the light on the retina Fig. 58. Changes in the shape of the lens during focusing (accommodation) is caused by contraction of ciliary muscles. Notice how the lens is thicker for closer focus and thinner for distance focus. Department of Biological Sciences, College of Science and Mathematics 67 COORDINATION and CONTROL: Sense Organs The lens and suspensory ligament divide the eyeball into: aqueous chambers (anterior & posterior chambers) and vitreous chamber, which are filled with aqueous and vitreous humor, respectively. Functions of HUMOR: 1. serves to refract the light 2. gives shape to the eyes 3. supports the lens 4. maintains the intra-ocular pressure to keep the eye ball Fig. 59. Section of the eyeball showing the anterior inflated aqueous chamber and vitreous chamber. Both contain humor, watery in the former and thick in the latter. Department of Biological Sciences, College of Science and Mathematics 68  COORDINATION and CONTROL: Sense Organs Layers of the eye: RETINA - Composed of 3 layers of cells: photoreceptor layer : rods & cones intermediate layer: bipolar neurons internal surface: ganglia Photoreceptors: RODS : for scotopic vision; peripheral vision (humans: ~120M ) CONES: for photopic vision; detailed central vision; (humans: ~5 M) Fig. 60. Longitudinal section of the eye showing the retina (photoreceptors enlarged). Department of Biological Sciences, College of Science and Mathematics 69 COORDINATION and CONTROL: Sense Organs Rods are used for peripheral vision where the image produced is not sharp and in shades of gray, while cones are used for photopic vision, capable of color vision and are responsible for high spatial acuity. 3 different types of cones: S cones (short wavelength): detect blue Fig. 61. The photoreceptors. Rods are sensitive M cones (medium wavelength): detect green to dim light while cones, to bright light. L cones (long wavelength): detect red Department of Biological Sciences, College of Science and Mathematics 70 COORDINATION and CONTROL: Sense Organs blind spot (optic disc) - the point on the retina where the optic nerve leaves the eye - no rod or cone (so no image is formed) Want to check your blind spot? Go to: https://visionaryeyecare.wordpress.com/2008/08/04/ eye-test-find-your-blind-spot-in-each-eye/ Fovea centralis contains the densest concentration of cones and is responsible for sharp central vision like what is needed when reading or doing Fig. 62. The blind spot and fovea anything that requires visual detail. centralis are located at the posterior portion of the retina. Department of Biological Sciences, College of Science and Mathematics 71  COORDINATION and CONTROL: Sense Organs Some Problems in Vision: a b Fig. 63. Comparison of normal vision with myopia or nearsightedness, and hyperopia or farsightedness (a). Concave lenses for correction of myopia to diverge or spread out light so when it passes through the lens system it comes into focus on the retina and convex lens for hyperopia to converge or concentrate the light so when it passes through the lens system, it comes into focus on the retina (b). Department of Biological Sciences, College of Science and Mathematics 72  COORDINATION and CONTROL: Sense Organs Some Problems in Vision: Astigmatism is a condition where the cornea or lens is irregularly shaped so that it prevents light from focusing properly on the retina, thus causing blurred vision. It is corrected with cylindrical lens. Presbyopia is a condition where the shape of the lens changes causing difficulty in focusing. It is corrected with bifocal lenses (top for distance vision and bottom for near vision) or with Fig. 64. Presbyopia and astigmatism and the appropriate corrective lenses for them. progressive lens. Department of Biological Sciences, College of Science and Mathematics 73 COORDINATION and CONTROL: Sense Organs Some Problems in Vision: Fig. 65. Glaucoma is a group of eye diseases Fig. 66. Cataract is a condition characterized by that can cause vision loss and blindness opacity of the lens. This causes by damaging the optic nerve. The most scattering of light instead of focusing common cause is high intraocular them to the retina. pressure. Department of Biological Sciences, College of Science and Mathematics 74 COORDINATION and CONTROL: Sense Organs Some Problems in Vision: Fig. 67. Nystagmus is a vision condition in which the eyes make repetitive, Fig. 68. Types of strabismus (crossed uncontrolled movements. eyes). Department of Biological Sciences, College of Science and Mathematics 75  An owl can see a mouse moving over 150 ft away with light no brighter than a candle. An ostrich has eyes that are two inches across. Each eye weighs more than the brain. Most people blink TAPETUM LUCIDUM – every 2-10 secs (0.3 tissue layer behind sec shut) retina of many A chameleon's vertebrates acting as eyes can look mirrors that reflect in opposite light aiding them in directions at night vision the same time. Department of Biological Sciences, College of Science and Mathematics 76 COORDINATION and CONTROL: Sense Organs The sense of smell is called olfaction. NOSE: Sense of Smell It involves perception of chemicals in air by chemoreceptors in the epithelium lining the nasal cavity. Fig. 69. The olfactory receptors in the olfactory epithelium. Department of Biological Sciences, College of Science and Mathematics 77 COORDINATION and CONTROL: Sense Organs If you have been using the Some Disorders in Olfaction: same soap for a long time now, then suddenly you decide to change into a new brand or Anosmia - inability to detect odors variant. Which one will have a Hyposmia - decreased ability to detect odors more distinguishable scent, the one that you are currently Hyperosmia – very strong sense of smell using, or the new one? Dysosmia - distorted identification of smell Try it and observe. Parosmia - altered perception of smell in the presence of an odor, usually unpleasant Phantosmia – perception of smell without an odor present Agnosia - inability to classify or contrast odors, although able to detect odors Department of Biological Sciences, College of Science and Mathematics 78 COORDINATION and CONTROL: Sense Organs Pheromones are chemicals released by animals that affect the behavior or physiology or animals of the same species. These chemicals are recognizable by other animals through inhalation. Some animals release pheromones into their urine or as a secretion of a gland. Aside from attracting potential mates, they can also be repellants to potential competitors. Some also play roles in mother-infant attachment. Some can affect timing of puberty, modify reproductive cycles and even prevent embryonic implantation. Generally from the nose, signals are sent to the amygdala and continues to the hypothalamus and results to some changes in reproductive physiology and behavior. Department of Biological Sciences, College of Science and Mathematics 79  Wear your mask properly!!! -friendlyreminder.me- Women can smell more scents than men. Sneezing is called sternutation, and when you sternutate, air rushes out your nose at a rate of Humans can detect 100 miles per Babies instinctively around 10,000 scents. hour! know their mothers by Dogs can smell up to their scents. twenty times as many. Department of Biological Sciences, College of Science and Mathematics 80 COORDINATION and CONTROL: Sense Organs TONGUE: Sense of Taste Taste buds are found inside most Fig. 70. The parts of the tongue. Gustation is the sensory function papillae, the projections on the of the tongue. It is possible due to the taste buds which surface of the tongue. They can also detect chemicals dissolved in water. That is why for taste to be found in the surrounding areas. be perceived the tongue should be kept moist. Department of Biological Sciences, College of Science and Mathematics 81 COORDINATION and CONTROL: Sense Organs TONGUE also perceives temperature and along with the rest of the mouth, helps determine a food's texture, oiliness, chewiness, viscosity and density and even pain like what is felt when food is too hot. Fig. 71. The 5 basic taste sensations. Gustation and olfaction are functions of chemical sensory systems that make up the tongue and the nose. The former required chemicals to be dissolved in water while the latter detects chemicals in air. Department of Biological Sciences, College of Science and Mathematics 82 COORDINATION and CONTROL: Sense Organs Some Disorders in Gustation: Compare how soup tastes if it is consumed while still hot Ageusia - inability to taste to soup that is consumed Hypogeusia - decreased ability to taste when cold. Which one tastes better? Why? Dysgeusia – distorted ability to taste Parageusia – a bad taste in the mouth Why can’t a person with colds, taste food well when What is the main reason for the colds primarily affect the anatomical positioning of the nose? nose close to the mouth? Department of Biological Sciences, College of Science and Mathematics 83  We have almost 10,000 taste buds inside our mouths; even on the roofs of our mouths. Fish can taste with their fins and tail as well as their mouth. Insects have the most highly developed sense of taste. They Taste is the have taste organs on their weakest of the feet, antennae, and mouthparts. five senses. Department of Biological Sciences, College of Science and Mathematics 84 COORDINATION and CONTROL EAR: Sense of Hearing Regions of the ear: 1. Outer ear 2. Middle ear 3. Inner ear The OUTER EAR is composed of: Pinna – the earflap or auricle Auditory Canal or auditory tube or auditory meatus - narrow tube running from the Fig. 72. The regions of the ear. The most external part of the outer ear (pinna or auricle) is designed to pinna to eardrum capture sound and direct it to the auditory canal. Department of Biological Sciences, College of Science and Mathematics 85  COORDINATION and CONTROL: Sense Organs MIDDLE EAR Eardrum or tympanic membrane - consists basically of very thin sheet of skin and connective tissue - ultimately converts and amplifies vibration in air to vibration in fluid Ossicles or ear bones - malleus (hammer) - incus (anvil) - stapes (stirrup) The middle ear is connected to the Fig. 73. The middle ear and its parts. Sound waves beat against pharynx by Eustachian tube, which the eardrum, causing vibrations of the ossicles, which permits pressure equalization on act as lever system to increase the force of vibration, both sides of the eardrum. ending with the stapes pushing against the inner ear with greater force. Department of Biological Sciences, College of Science and Mathematics 86 COORDINATION and CONTROL: Sense Organs INNER EAR Cochlea - a small fluid-filled, snail-shaped channel through the temporal bone - contains the receptors for transduction of the mechanical wave into an electrical signal Semicircular canals Fig. 74. The inner ear and its parts. Take note that - half-circular, fluid-filled tubes in the inner ear has connection to the brain the vestibular labyrinth via the auditory (vestibulocochlear) nerve. Department of Biological Sciences, College of Science and Mathematics 87  COORDINATION and CONTROL: Sense Organs 3 canals of the bony labyrinth of inner ear: a. Vestibular canal c b. Semicircular canals c. Cochlear canal INNER EAR a b Fig. 75. Closer look at sections of the cochlea showing the 3 fluid-filled canals. The fluid inside these canals are affected by the vibrations caused by the stapes hitting the oval window. Department of Biological Sciences, College of Science and Mathematics 88 COORDINATION and CONTROL: Sense Organs INNER EAR Fluids in the canals: Perilymph - the fluid within the space (scala tympani and scala vestibuli) separating the membranous and bony labyrinths of the ear Endolymph - The fluid contained in the membranous labyrinth of the inner ear (cochlear duct) Fig. 76. Section of the inner ear showing the fluid-filled cavities. Disturbance of this fluid creates vibration that leads to generation of nerve impulse in the organ of Corti. Department of Biological Sciences, College of Science and Mathematics 89  COORDINATION and CONTROL: Sense Organs Organ of Corti - the receptor organ for hearing located in the mammalian cochlea. - contains the hair cells (receptors) that give rise to nerve signals in response to sound vibrations. Disturbance of the fluids in the spaces moves the hair cells and start the INNER EAR nerve impulse conduction to the brain via the auditory nerve. Fig. 77. The organ of Corti and its hair cells lying on the basilar membrane and covered by a tectorial membrane. Hair cells “sway” when the fluid inside the ducts vibrate. Department of Biological Sciences, College of Science and Mathematics 90 COORDINATION and CONTROL: Sense Organs Ever wonder why dogs are afraid or agitated during new year’s eve when firecrackers are exploding loud around the neighborhood? Department of Biological Sciences, College of Science and Mathematics 91 COORDINATION and CONTROL: Sense Organs In invertebrates: Statocysts – specialized sense organs for monitoring gravity and low-frequency vibrations present from cnidarians to arthropods - simple sacs lined with hair cells and containing statolith (calcareous structure) Fig. 78. Organs for static balance in representative invertebrates. Department of Biological Sciences, College of Science and Mathematics 92 COORDINATION and CONTROL: Sense Organs The vertebrate ear is also involved in balancing. The vestibular system has otolith organs: saccule and utricle. While each of the three semi-circular canals is responsible for a specific direction of head movement, the otolith organs also have similar function but in addition to fluid, they also contain ear stones or otoliths, which make the otolith organs capable Fig. 79. Saccule and utricle which contain otoliths, of detecting acceleration. Our ability calcium carbonate crystals that are to keep our balance depends on this. sensitive to vertical and horizontal acceleration, respectively. Department of Biological Sciences, College of Science and Mathematics 93 COORDINATION and CONTROL: Sense Organs a b Fig. 80. (a) Top view of the otolith organ, showing location of hair cells relative to otoliths. (b) When the position of the head changes, position of utricle (and otoliths) changes. Department of Biological Sciences, College of Science and Mathematics 94 COORDINATION and CONTROL: Sense Organs Some Problems in Hearing: Fig. 82. Otitis media, inflammation of the middle ear, could be with or without infection. Fig. 81. Hearing loss Department of Biological Sciences, College of Science and Mathematics 95 COORDINATION and CONTROL: Sense Organs Some Problems in Hearing: Fig. 84. Ruptured Fig. 83. Earwax or cerumen is eardrum. a secretion of the ceruminous glands of the ear. Ruptured eardrum Department of Biological Sciences, College of Science and Mathematics 96 COORDINATION and CONTROL: Sense Organs Perceived Attributes of Sound: Pitch corresponds to frequency of vibration, Timbre or quality of tone is produced measured in Hertz (Hz). High-frequency by the pattern of hair cells (≥15.000Hz) sounds are higher-pitched (short stimulated by sympathetic vibration. wavelength) than low-frequency (long wavelengths; It describes the sound’s quality and ≤100Hz) sounds. Most humans can perceive sounds with frequencies character without regard for its between 30 and 20,000 Hz. pitch or volume. This enables us to Women are typically better at hearing high frequencies, distinguish voices of people we know but everyone’s ability to hear high frequencies from those of strangers as well as decreases with age. sounds of different musical Dogs detect up to about 40,000 Hz; cats, 60,000 Hz; instruments. bats, 100,000 Hz; and dolphins 150,000 Hz, and American shad (Alosa sapidissima), a fish, can hear Loudness or amplitude of a tone 180,000 Hz. Those frequencies above the human range depends on the number of hair cells are called ultrasound. stimulated. Volume is measured in decibels (dB). Louder sounds have greater amplitude. The softest sound that a human can hear is the zero point. Humans speak normally at 60 decibels. Department of Biological Sciences, College of Science and Mathematics 97  You get a new ear canal every year! The Dolphins have the ear canal skin is best sense of constantly growing hearing among outward at a rate of animals. They are 1.3 inches every able to hear 14 year. If it didn’t fall times better than off, you’d have a two humans. foot string hanging out of your ear by the time you are 20! Your ear drum is less than 0.7 inches (17.5 mm) in diameter. It moves less than a billionth of an inch when hearing. Your ear never stops working, even when you’re asleep. Children have more It continues to hear sensitive ears than adults. sounds, but your brain They can recognize a wider simply shuts them out. variety of noises. Department of Biological Sciences, College of Science and Mathematics 98  The whole area of the middle ear is no bigger than an M&M. (regular size) Which ear do you use for taking phone calls? That is your dominant ear. Check for the difference in sensitivity of your ears by doing the watch-tick test. Choose a watch that produces a ticking sound. Start by putting it closer to your ear. Then gradually move it away. Take note of the farthest distance of the watch from your ear where you can still hear its ticking sound. Ask somebody to measure that distance for you. Do the same in your other ear. Now you see the difference! Be sure to do this when it is quiet around you. The three bones in the ear are the smallest bones in The smallest muscle in the body is the the body, and all STAPEDIUS, located in the middle ear. It is only three could fit 1/20th of an inch long and controls the smallest together on a 25- bone in the body, the STAPES. While the stapes centavo coin. is twice the size of the muscle, it’s still only about 1/10th of an inch long. Department of Biological Sciences, College of Science and Mathematics 99  COORDINATION and CONTROL: Sense Organs SENSORY ADAPTATION: when sensory receptors reduce their sensitivity to a continuous, unchanging stimuli Getting used to certain temperature Getting used to certain taste Getting used to Getting used to the certain smell feel of fabric on skin Department of Biological Sciences, College of Science and Mathematics 100 COORDINATION and CONTROL: Sense Organs Any sensation when carried to the extreme can produce the sensation of pain (nociception). Nociceptors help signal pain that is related to temperature, pressure and chemicals. This signal is protective in nature. Department of Biological Sciences, College of Science and Mathematics 101 SELF-CHECK: 1. All sensory signals except _ travel to the _ in the brain before the cerebral cortex. a. vision; thalamus c. vision; cranial nerves b. olfaction; thalamus d. olfaction; cranial nerves 2. If you were to burn your epidermis, what receptor type would you most likely burn? a. free nerve endings c. Pacinian corpuscle b. Ruffini endings d. hair receptors 3. Auditory hair cells are indirectly anchored to the _____. a. basilar membrane b. oval window c. tectorial membrane d. ossicles 4. Why is it easier to see images at night using peripheral, rather than the central, vision? a. Cones are denser in the periphery of the retina. b. Bipolar cells are denser in the periphery of the retina. c. Rods are denser in the periphery of the retina. d. The optic nerve exits at the periphery of the retina. 102 REFERENCES: Campbell, N.A. and J.B. Reece. (2008). Biology. 8th ed., San Francisco: Pearson Education Inc., 1465 pp. Clark, M.A., J. Choi and M. Douglas. (2020). Biology 2e. Texas: OpenStax, 1447 pp. Hickman, C.P. Jr., L.S. Roberts and A. Larson. 2001. Integrated Principles of Zoology, 11th Ed., New York: McGraw-Hill, 899 pp. Hickman, C.P., L.S. Roberts, S.L. Keen, A. Larson, H. I’Anson and D.J. Eisenhour. (2008). Integrated Principles of Zoology, 14th ed, New York: McGraw-Hill, 936 pp. https://material.io/design/sound/sound-attributes.html#timbre https://www.aoa.org/ https://www.dartmouth.edu/~dons/part_1/chapter_6.html https://www.ncbi.nlm.nih.gov/books/ 103 COORDINATION AND CONTROL UP NEXT!!! Part 2: Hormones and the Endocrine System