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The Nervous System. Nervous systems Perform the three overlapping functions of sensory input, integration, and motor output Perform the three overlapping.

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Presentation on theme: "The Nervous System. Nervous systems Perform the three overlapping functions of sensory input, integration, and motor output Perform the three overlapping."— Presentation transcript:

1 The Nervous System

2 Nervous systems Perform the three overlapping functions of sensory input, integration, and motor output Perform the three overlapping functions of sensory input, integration, and motor output Peripheral nervous system (PNS). Peripheral nervous system (PNS). Sensory receptors a responsive to external and internal stimuli. Sensory receptors a responsive to external and internal stimuli. Such sensory input is conveyed to integration centers. Such sensory input is conveyed to integration centers. Where in the input is interpreted an associated with a response. Where in the input is interpreted an associated with a response.

3 Fig. 48.1

4 Motor output is the conduction of signals from integration centers to effector cells. Motor output is the conduction of signals from integration centers to effector cells. Effector cells carry out the bodys response to a stimulus. Effector cells carry out the bodys response to a stimulus. The central nervous system (CNS) is responsible for integration. The central nervous system (CNS) is responsible for integration. The signals of the nervous system are conducted by nerves. The signals of the nervous system are conducted by nerves.

5 Networks of neurons Neuron Structure and Synapses. Neuron Structure and Synapses. The neuron is the structural and functional unit of the nervous system. The neuron is the structural and functional unit of the nervous system. Nerve impulses are conducted along a neuron. Nerve impulses are conducted along a neuron. Dentrite cell body axon hillock axon Dentrite cell body axon hillock axon Some axons are insulated by a myelin sheath. Some axons are insulated by a myelin sheath.

6 Fig. 48.2

7 Axonal Endings Axon endings are called synaptic terminals. Axon endings are called synaptic terminals. They contain neurotransmitters which conduct a signal across a synapse. They contain neurotransmitters which conduct a signal across a synapse. A synapse is the junction between a presynaptic and postsynaptic neuron. A synapse is the junction between a presynaptic and postsynaptic neuron.

8 A Simple Nerve Circuit – the Reflex Arc. A Simple Nerve Circuit – the Reflex Arc. A reflex is an autonomic response. A reflex is an autonomic response. Fig. 48.3

9 A ganglion is a cluster of nerve cell bodies within the PNS. A ganglion is a cluster of nerve cell bodies within the PNS. A nucleus is a cluster of nerve cell bodies within the CNS. A nucleus is a cluster of nerve cell bodies within the CNS.

10 Neurons differ in terms of both function and shape Fig. 48.4

11 Types of Nerve Circuits Single presynaptic neuron several postsynaptic neurons. Single presynaptic neuron several postsynaptic neurons. Several presynaptic neurons single postsynaptic neuron. Several presynaptic neurons single postsynaptic neuron. Circular paths. Circular paths.

12 Supporting Cells (Glia) There are several types of glia. There are several types of glia. Astrocytes are found within the CNS. Astrocytes are found within the CNS. Structural and metabolic support. Structural and metabolic support. By inducing the formation of tight junctions between capillary cells astrocytes help form the blood-brain barrier. By inducing the formation of tight junctions between capillary cells astrocytes help form the blood-brain barrier. Like neurons, astrocytes communicate with one another via chemical signals. Like neurons, astrocytes communicate with one another via chemical signals.

13 Myelin Sheath Oligodendrocytes are found within the CNS. Oligodendrocytes are found within the CNS. Form a myelin sheath by insulating axons. Form a myelin sheath by insulating axons. Schwann cells are found within the PNS. Schwann cells are found within the PNS. Form a myelin sheath by insulating axons. Form a myelin sheath by insulating axons. Fig. 48.5

14 Every cell has a voltage Membrane potential, across its plasma membrane Membrane potential, across its plasma membrane A membrane potential is a localized electrical gradient across membrane. A membrane potential is a localized electrical gradient across membrane. Anions are more concentrated within a cell. Anions are more concentrated within a cell. Cations are more concentrated in the extracellular fluid. Cations are more concentrated in the extracellular fluid.

15 Measuring Membrane Potentials. Measuring Membrane Potentials. Fig. 48.6a An unstimulated cell usually have a resting potential of -70mV. An unstimulated cell usually have a resting potential of -70mV.

16 Maintaining a Membrane Potential Cations. Cations. K+ the principal intracellular cation. K+ the principal intracellular cation. Na+ is the principal extracellular cation. Na+ is the principal extracellular cation. Anions. Anions. Proteins, amino acids, sulfate, and phosphate are the principal intracellular anions. Proteins, amino acids, sulfate, and phosphate are the principal intracellular anions. Cl– is principal extracellular anion. Cl– is principal extracellular anion.

17 Ungated ion channels allow ions to diffuse across the plasma membrane. Ungated ion channels allow ions to diffuse across the plasma membrane. These channels are always open. These channels are always open. This diffusion does not achieve an equilibrium since sodium-potassium pump transports these ions against their concentration gradients. This diffusion does not achieve an equilibrium since sodium-potassium pump transports these ions against their concentration gradients. Fig. 48.7

18 Changes in the membrane potential Excitable cells have the ability to generate large changes in their membrane potentials. Excitable cells have the ability to generate large changes in their membrane potentials. Gated ion channels open or close in response to stimuli. Gated ion channels open or close in response to stimuli. The subsequent diffusion of ions leads to a change in the membrane potential. The subsequent diffusion of ions leads to a change in the membrane potential.

19 Gated Channels Types of gated ions. Types of gated ions. Chemically-gated ion channels open or close in response to a chemical stimulus. Chemically-gated ion channels open or close in response to a chemical stimulus. Voltage-gated ion channels open or close in response to a change in membrane potential. Voltage-gated ion channels open or close in response to a change in membrane potential.

20 At the Dendrites Graded Potentials: Hyperpolarization and Depolarization Graded Potentials: Hyperpolarization and Depolarization Graded potentials are changes in membrane potential Graded potentials are changes in membrane potential

21 Hyperpolarization. Hyperpolarization. Gated K + channels open K + diffuses out of the cell the membrane potential becomes more negative. Gated K + channels open K + diffuses out of the cell the membrane potential becomes more negative. Fig. 48.8a

22 Depolarization. Depolarization. Gated Na + channels open Na + diffuses into the cell the membrane potential becomes less negative. Gated Na + channels open Na + diffuses into the cell the membrane potential becomes less negative. Fig. 48.8b

23 The Action Potential: All or Nothing Depolarization. The Action Potential: All or Nothing Depolarization. If graded potentials sum to -55mV a threshold potential is achieved. If graded potentials sum to -55mV a threshold potential is achieved. This triggers an action potential. This triggers an action potential. Axons only. Axons only. Fig. 48.8c

24 Chemical or electrical communication between cells occurs at synapses Electrical Synapses. Electrical Synapses. Action potentials travels directly from the presynaptic to the postsynaptic cells via gap junctions. Action potentials travels directly from the presynaptic to the postsynaptic cells via gap junctions. Chemical Synapses. Chemical Synapses. More common than electrical synapses. More common than electrical synapses. Postsynaptic chemically-gated channels exist for ions such as Na +, K +, and Cl -. Postsynaptic chemically-gated channels exist for ions such as Na +, K +, and Cl -. Depending on which gates open the postsynaptic neuron can depolarize or hyperpolarize. Depending on which gates open the postsynaptic neuron can depolarize or hyperpolarize.

25 Fig

26 Neural integration occurs at the cell Excitatory postsynaptic potentials (EPSP) depolarize the postsynaptic neuron. Excitatory postsynaptic potentials (EPSP) depolarize the postsynaptic neuron. The binding of neurotransmitter to postsynaptic receptors open gated channels that allow Na + to diffuse into and K + to diffuse out of the cell. The binding of neurotransmitter to postsynaptic receptors open gated channels that allow Na + to diffuse into and K + to diffuse out of the cell.

27 Inhibitory postsynaptic potential Inhibitory postsynaptic potential (IPSP) hyperpolarize the postsynaptic neuron. Inhibitory postsynaptic potential (IPSP) hyperpolarize the postsynaptic neuron. The binding of neurotransmitter to postsynaptic receptors open gated channels that allow K+ to diffuse out of the cell and/or Cl- to diffuse into the cell. The binding of neurotransmitter to postsynaptic receptors open gated channels that allow K+ to diffuse out of the cell and/or Cl- to diffuse into the cell.

28 Summation: graded potentials (EPSPs and IPSPs) are summed to either depolarize or hyperpolarize a postsynaptic neuron. Summation: graded potentials (EPSPs and IPSPs) are summed to either depolarize or hyperpolarize a postsynaptic neuron. Fig

29 Acetylcholine. Acetylcholine. Excitatory to skeletal muscle. Excitatory to skeletal muscle. Inhibitory to cardiac muscle. Inhibitory to cardiac muscle. Secreted by the CNS, PNS, and at vertebrate neuromuscular junctions. Secreted by the CNS, PNS, and at vertebrate neuromuscular junctions. Same neurotransmitter can produce different effects on different types of cells

30 Biogenic Amines. Biogenic Amines. Epinephrine and norepinephrine. Epinephrine and norepinephrine. Can have excitatory or inhibitory effects. Can have excitatory or inhibitory effects. Secreted by the CNS and PNS. Secreted by the CNS and PNS. Secreted by the adrenal glands. Secreted by the adrenal glands.

31 Dopamine Generally excitatory; may be inhibitory at some sites. Generally excitatory; may be inhibitory at some sites. Widespread in the brain. Widespread in the brain. Affects sleep, mood, attention, and learning. Affects sleep, mood, attention, and learning. Secreted by the CNS and PNS. Secreted by the CNS and PNS. A lack of dopamine in the brain is associated with Parkinsons disease. A lack of dopamine in the brain is associated with Parkinsons disease. Excessive dopamine is linked to schizophrenia. Excessive dopamine is linked to schizophrenia.

32 Serotonin Generally inhibitory. Generally inhibitory. Widespread in the brain. Widespread in the brain. Affects sleep, mood, attention, and learning Affects sleep, mood, attention, and learning Secreted by the CNS. Secreted by the CNS.

33 Amino Acids Gamma aminobutyric acid (GABA). Gamma aminobutyric acid (GABA). Inhibitory. Inhibitory. Secreted by the CNS and at invertebrate neuromuscular junctions. Secreted by the CNS and at invertebrate neuromuscular junctions. Glycine. Glycine. Inhibitory. Inhibitory. Secreted by the CNS. Secreted by the CNS.

34 Amino Acids Glutamate. Glutamate. Excitatory. Excitatory. Secreted by the CNS and at invertebrate neuromuscular junctions. Secreted by the CNS and at invertebrate neuromuscular junctions. Aspartate. Aspartate. Excitatory. Excitatory. Secreted by the CNS Secreted by the CNS

35 Neuropeptides Substance P. Substance P. Excitatory. Excitatory. Secreted by the CNS and PNS. Secreted by the CNS and PNS. Met-enkephalin (an endorphin). Met-enkephalin (an endorphin). Generally inhibitory. Generally inhibitory. Secreted by the CNS. Secreted by the CNS.

36 Gasses Gasses that act as local regulators. Gasses that act as local regulators. Nitric oxide. Nitric oxide. Carbon monoxide. Carbon monoxide.

37 Vertebrate nervous systems Central nervous system (CNS). Central nervous system (CNS). Brain and spinal cord. Brain and spinal cord. Both contain fluid-filled spaces which contain cerebrospinal fluid (CSF). Both contain fluid-filled spaces which contain cerebrospinal fluid (CSF). The central canal of the spinal cord is continuous with the ventricles of the brain. The central canal of the spinal cord is continuous with the ventricles of the brain.

38 Vertebrate nervous systems White matter is composed of bundles of myelinated axons White matter is composed of bundles of myelinated axons Gray matter consists of unmyelinated axons, nuclei, and dendrites. Gray matter consists of unmyelinated axons, nuclei, and dendrites. Peripheral nervous system. Peripheral nervous system. Everything outside the CNS. Everything outside the CNS.

39 Divisions of the peripheral nervous system Structural composition of the PNS. Structural composition of the PNS. Paired cranial nerves that originate in the brain and innervate the head and upper body. Paired cranial nerves that originate in the brain and innervate the head and upper body. Paired spinal nerves that originate in the spinal cord and innervate the entire body. Paired spinal nerves that originate in the spinal cord and innervate the entire body. Ganglia associated with the cranial and spinal nerves. Ganglia associated with the cranial and spinal nerves.

40 Functional composition of PNS Fig

41 A closer look at the (often antagonistic) divisions of the autonomic nervous system (ANS). A closer look at the (often antagonistic) divisions of the autonomic nervous system (ANS). Fig

42 Embryonic development of the vertebrate brain reflects its evolution from three anterior bulges of the neural tube Fig

43 Fig

44 The Brainstem. The Brainstem. The lower brain. The lower brain. Consists of the medulla oblongata, pons, and midbrain. Consists of the medulla oblongata, pons, and midbrain. Derived from the embryonic hindbrain and midbrain. Derived from the embryonic hindbrain and midbrain. Functions in homeostasis, coordination of movement, conduction of impulses to higher brain centers. Functions in homeostasis, coordination of movement, conduction of impulses to higher brain centers. Evolutionary older structures of the vertebrate brain regulate essential autonomic and integrative functions

45 The Medulla and Pons. The Medulla and Pons. Medulla oblongata. Medulla oblongata. Contains nuclei that control visceral (autonomic homeostatic) functions. Contains nuclei that control visceral (autonomic homeostatic) functions. Breathing. Breathing. Heart and blood vessel activity. Heart and blood vessel activity. Swallowing. Swallowing. Vomiting. Vomiting. Digestion. Digestion. Relays information to and from higher brain centers. Relays information to and from higher brain centers.

46 Pons. Pons. Contains nuclei involved in the regulation of visceral activities such as breathing. Contains nuclei involved in the regulation of visceral activities such as breathing. Relays information to and from higher brain centers. Relays information to and from higher brain centers.

47 The Midbrain. The Midbrain. Contains nuclei involved in the integration of sensory information. Contains nuclei involved in the integration of sensory information. Superior colliculi are involved in the regulation of visual reflexes. Superior colliculi are involved in the regulation of visual reflexes. Inferior colliculi are involved in the regulation of auditory reflexes. Inferior colliculi are involved in the regulation of auditory reflexes. Relays information to and from higher brain centers. Relays information to and from higher brain centers.

48 The Reticular System, Arousal, and Sleep. The Reticular System, Arousal, and Sleep. The reticular activating system (RAS) of the reticular formation. The reticular activating system (RAS) of the reticular formation. Regulates sleep and arousal. Regulates sleep and arousal. Acts as a sensory filter. Acts as a sensory filter. Fig

49 Sleep and wakefulness produces patterns of electrical activity in the brain that can be recorded as an electroencephalogram (EEG). Sleep and wakefulness produces patterns of electrical activity in the brain that can be recorded as an electroencephalogram (EEG). Most dreaming occurs during REM (rapid eye movement) sleep. Most dreaming occurs during REM (rapid eye movement) sleep. Fig b-d

50 The Cerebellum Develops from part of the metencephalon. Develops from part of the metencephalon. Functions to error-check and coordinate motor activities, and perceptual and cognitive factors. Functions to error-check and coordinate motor activities, and perceptual and cognitive factors. Relays sensory information about joints, muscles, sight, and sound to the cerebrum. Relays sensory information about joints, muscles, sight, and sound to the cerebrum. Coordinates motor commands issued by the cerebrum. Coordinates motor commands issued by the cerebrum.

51 The thalamus and hypothalamus. The thalamus and hypothalamus. The epithalamus, thalamus, and hypothalamus are derived from the embryonic diencephalon. The epithalamus, thalamus, and hypothalamus are derived from the embryonic diencephalon. Epithalamus. Epithalamus. Includes a choroid plexus and the pineal gland. Includes a choroid plexus and the pineal gland.

52 Thalamus. Thalamus. Relays all sensory information to the cerebrum. Relays all sensory information to the cerebrum. Contains one nucleus for each type of sensory information. Contains one nucleus for each type of sensory information. Relays motor information from the cerebrum. Relays motor information from the cerebrum. Receives input from the cerebrum. Receives input from the cerebrum. Receives input from brain centers involved in the regulation of emotion and arousal. Receives input from brain centers involved in the regulation of emotion and arousal.

53 Hypothalamus. Hypothalamus. Regulates autonomic activity. Regulates autonomic activity. Contains nuclei involved in thermoregulation, hunger, thirst, sexual and mating behavior, etc. Contains nuclei involved in thermoregulation, hunger, thirst, sexual and mating behavior, etc. Regulates the pituitary gland. Regulates the pituitary gland.

54 The Hypothalamus and Circadian Rhythms. The Hypothalamus and Circadian Rhythms. The biological clock is the internal timekeeper. The biological clock is the internal timekeeper. The clocks rhythm usually does not exactly match environmental events. The clocks rhythm usually does not exactly match environmental events. Experiments in which humans have been deprived of external cues have shown that biological clock has a period of about 25 hours. Experiments in which humans have been deprived of external cues have shown that biological clock has a period of about 25 hours. In mammals, the hypothalamic suprachiasmatic nuclei (SCN) function as a biological clock. In mammals, the hypothalamic suprachiasmatic nuclei (SCN) function as a biological clock. Produce proteins in response to light/dark cycles. Produce proteins in response to light/dark cycles. This, and other biological clocks, may be responsive to hormonal release, hunger, and various external stimuli. This, and other biological clocks, may be responsive to hormonal release, hunger, and various external stimuli.

55 The cerebrum is derived from the embryonic telencephalon. The cerebrum is derived from the embryonic telencephalon. The cerebrum is the most highly evolved structure of the mammalian brain Fig a

56 The cerebrum is divided into left and right cerebrum hemispheres. The cerebrum is divided into left and right cerebrum hemispheres. The corpus callosum is the major connection between the two hemispheres. The corpus callosum is the major connection between the two hemispheres. The left hemisphere is primarily responsible for the right side of the body. The left hemisphere is primarily responsible for the right side of the body. The right hemisphere is primarily responsible for the left side of the body. The right hemisphere is primarily responsible for the left side of the body. Cerebral cortex: outer covering of gray matter. Cerebral cortex: outer covering of gray matter. Neocortex: region unique to mammals. Neocortex: region unique to mammals. The more convoluted the surface of the neocortex the more surface area the more neurons. The more convoluted the surface of the neocortex the more surface area the more neurons. Basal nuclei: internal clusters of nuclei. Basal nuclei: internal clusters of nuclei.

57 The cerebrum is divided into frontal, temporal, occipital, and parietal lobes. The cerebrum is divided into frontal, temporal, occipital, and parietal lobes. Regions of the cerebrum are specialized for different functions Fig b

58 Frontal lobe. Frontal lobe. Contains the primary motor cortex. Contains the primary motor cortex. Parietal lobe. Parietal lobe. Contains the primary somatosensory cortex. Contains the primary somatosensory cortex.

59 Fig

60 Integrative Function of the Association Areas. Integrative Function of the Association Areas. Much of the cerebrum is given over to association areas. Much of the cerebrum is given over to association areas. Areas where sensory information is integrated and assessed and motor responses are planned. Areas where sensory information is integrated and assessed and motor responses are planned.

61 The brain exhibits plasticity of function. The brain exhibits plasticity of function. For example, infants with intractable epilepsy may have an entire cerebral hemisphere removed. For example, infants with intractable epilepsy may have an entire cerebral hemisphere removed. The remaining hemisphere can provide the function normally provided by both hemispheres. The remaining hemisphere can provide the function normally provided by both hemispheres.

62 Lateralization of Brain Function The left hemisphere. The left hemisphere. Specializes in language, math, logic operations, and the processing of serial sequences of information, and visual and auditory details. Specializes in language, math, logic operations, and the processing of serial sequences of information, and visual and auditory details. Specializes in detailed activities required for motor control. Specializes in detailed activities required for motor control. The right hemisphere. The right hemisphere. Specializes in pattern recognition, spatial relationships, nonverbal ideation, emotional processing, and the parallel processing of information. Specializes in pattern recognition, spatial relationships, nonverbal ideation, emotional processing, and the parallel processing of information.

63 Language and Speech Brocas area. Brocas area. Usually located in the left hemispheres frontal lobe Usually located in the left hemispheres frontal lobe Responsible for speech production. Responsible for speech production. Wernickes area. Wernickes area. Usually located in the right hemispheres temporal lobe Usually located in the right hemispheres temporal lobe Responsible for the comprehension of speech. Responsible for the comprehension of speech. Other speech areas are involved generating verbs to match nouns, grouping together related words, etc. Other speech areas are involved generating verbs to match nouns, grouping together related words, etc.

64 Emotions. Emotions. In mammals, the limbic system is composed of the hippocampus, olfactory cortex, inner portions of the cortexs lobes, and parts of the thalamus and hypothalamus. In mammals, the limbic system is composed of the hippocampus, olfactory cortex, inner portions of the cortexs lobes, and parts of the thalamus and hypothalamus. Mediates basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory Mediates basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory For example, the amygdala is involved in recognizing the emotional content of facial expression. For example, the amygdala is involved in recognizing the emotional content of facial expression. Fig

65 Memory and Learning Short-term memory stored in the frontal lobes. Short-term memory stored in the frontal lobes. The establishment of long-term memory involves the hippocampus. The establishment of long-term memory involves the hippocampus. The transfer of information from short-term to long- term memory. The transfer of information from short-term to long- term memory. Is enhanced by repetition (remember that when you are preparing for an exam). Is enhanced by repetition (remember that when you are preparing for an exam). Influenced by emotional states mediated by the amygdala. Influenced by emotional states mediated by the amygdala. Influenced by association with previously stored information. Influenced by association with previously stored information.

66 Different types of long-term memories are stored in different regions of the brain. Different types of long-term memories are stored in different regions of the brain. Memorization-type memory can be rapid. Memorization-type memory can be rapid. Primarily involves changes in the strength of existing nerve connections. Primarily involves changes in the strength of existing nerve connections. Learning of skills and procedures is slower. Learning of skills and procedures is slower. Appears to involves cellular mechanisms similar to those involved in brain growth and development. Appears to involves cellular mechanisms similar to those involved in brain growth and development.

67 Functional changes in synapses in synapses of the hippocampus and amygdala are related to memory storage and emotional conditioning. Functional changes in synapses in synapses of the hippocampus and amygdala are related to memory storage and emotional conditioning. Long-term depression (LTD) occurs when a postsynaptic neuron displays decreased responsiveness to action potentials. Long-term depression (LTD) occurs when a postsynaptic neuron displays decreased responsiveness to action potentials. Induced by repeated, weak stimulation. Induced by repeated, weak stimulation. Long-term potentiation (LTP) occurs when a postsynaptic neuron displays increased responsiveness to stimuli. Long-term potentiation (LTP) occurs when a postsynaptic neuron displays increased responsiveness to stimuli. Induced by brief, repeated action potentials that strongly depolarize the postsynaptic membrane. Induced by brief, repeated action potentials that strongly depolarize the postsynaptic membrane. May be associated with memory storage and learning. May be associated with memory storage and learning.

68 Human Consciousness Brain imaging can show neural activity associated with: Brain imaging can show neural activity associated with: Conscious perceptual choice Conscious perceptual choice Unconscious processing Unconscious processing Memory retrieval Memory retrieval Working memory. Working memory. Consciousness appears to be a whole-brain phenomenon. Consciousness appears to be a whole-brain phenomenon.

69 The mammalian PNS has the ability to repair itself, the CNS does not. The mammalian PNS has the ability to repair itself, the CNS does not. Research on nerve cell development and neural stem cells may be the future of treatment for damage to the CNS. Research on nerve cell development and neural stem cells may be the future of treatment for damage to the CNS. Research on neuron development and neural stem cells may lead to new approaches for treating CNS injuries and diseases

70 Nerve Cell Development. Nerve Cell Development. Fig

71 Neural Stem Cells The adult human brain does produce new nerve cells. The adult human brain does produce new nerve cells. New nerve cells have been found in the hippocampus. New nerve cells have been found in the hippocampus. Since mature human brain cells cannot undergo cell division the new cells must have arisen from stem cells. Since mature human brain cells cannot undergo cell division the new cells must have arisen from stem cells.


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