Presentation on theme: "Nervous System Objectives: 1.Identify structures of the nervous system. 2.Explain differences in the function of the peripheral nervous system and the."— Presentation transcript:
Nervous System Objectives: 1.Identify structures of the nervous system. 2.Explain differences in the function of the peripheral nervous system and the central nervous system.
D. Nervous Tissue Nervous tissue is: – found in the brain, spinal cord, and nerves. – made up of: 1.Neurons: nerve cells (bundles of axons) 2.Neuroglial cells: helper cells – “glia” = glue – Support and bind components of nervous tissue to each other and to blood vessels – Function similarly to connective tissue in other organ systems
Parts of a Neuron
Nervous System Organs of this system are divided into 2 groups: 1.Central Nervous System (CNS) Brain Spinal cord 2.Peripheral Nervous System (PNS) Composed of the nerves (peripheral nerves) that connect the CNS to other body parts Functions of the nervous system: 1.Sensory 2.Integrative 3.Motor
1. Sensory Function Sensory receptors at the ends of peripheral neurons: – Gather info by detecting changes inside and outside the body. Inside: temperature and oxygen concentration Outside: light and sound intensities – Convert info into nerve impulses (electrochemical changes) which are transmitted along peripheral nerves to the CNS
2. Integrative Function Nerve impulses are integrated (brought together) in the CNS. Allows us to make conscious or subconscious decisions.
3. Motor Function Peripheral nerves carry impulses from the CNS to effectors (responsive structures). Effectors are NOT part of the nervous system, but include muscles and glands.
Motor Function Motor functions can be divided into 2 groups: – Somatic nervous system Consciously controlled (voluntary) Controls skeletal muscle – Autonomic nervous system: Involuntary Includes heart, smooth muscle, and various glands
Nervous System Function Recap 1.Detects changes inside and outside the body, 2.Makes decisions based on the information received, and 3.Stimulates muscles or glands to respond. What is the purpose of this process?????
Neuroglial Cells Functions: – Fill spaces – Provide structural frameworks – Produce myelin – Carry on phagocytosis Vary from CNS to PNS Table: Type of Cell, Location, Function, Other specific info
CNS Neuroglial Cells Greatly outnumber neurons in the CNS (think worker ants vs. Queen ant) 1.Microglial cells – Scattered throughout CNS – Support neurons and phagocytize bacterial cells and cellular debris 2.Oligodendrocytes – Occur in rows along nerve fibers – Provide layers of myelin around axons within brain and spinal cord
CNS Neuroglial Cells, continued…. 3.Astrocytes – Found between neurons and blood vessels – Provide structural support, help regulate nutrients and ions in tissues – Form scar tissue to fill spaces after CNS injuries 4.Ependymal cells – Form epithelial-like membrane in parts of the brain (choroid plexuses) – Form inner linings that enclose ventricles in the brain and central canal in the spinal cord
CNS Neuroglial Cells
PNS Neuroglial cells 1.Schwann cells: form myelin sheath around axons
Neurons Vary in size and structure, but have common features: 1.Cell Body 2.Dendrites 3.Axon Mature neurons do not divide, but neural stem cells can divide and form neurons or neuroglial cells.
1. Cell Body Contains normal cellular structures (golgi apparatus, mitochondria, cytoplasm, cell membrane, etc.) Neurofibrils – fine threads that extend into the axon Nissl bodies (chromatophilic substances) – Membranous sacs in the cytoplasm – Similar to rough ER – Ribosomes on Nissl bodies synthesize ______
2. Dendrites Usually short and highly branched (dendr = ?) The main receptive surfaces for receiving communication from axons of other neurons
3. Axons Arise from a slight elevation of the cell body, called the axonal hillock. Conduct nerve impulses away from the cell body Contains many mitochondria, microtubules, and neurofibrils Originates as a single structure, but may have branches, especially at the end to interact with receptive surfaces of other cells
PNS Axons Enclosed in myelin sheaths composed of many Schwann cells Myelin is a lipoprotein. Neurilemma sheath surrounds the myelin sheath Nodes of Ranvier – narrow gaps in the myelin sheath between the Schwann cells
Classification of Neurons Classification based on Structural differences: Bipolar neurons Unipolar neurons Multipolar neurons Classification based on Functional differences: Sensory neurons (afferent neurons) Interneurons (association or internuncial neurons) Motor neurons (efferent neurons)
Structural Differences Sketch the neurons below. Notes on the next 3 slides:
Structural Differences, cont….. 1.Bipolar: – 2 processes Axon Dendrite – Found in specialized parts of the eyes, nose, and ears
Structural Differences, cont….. 2.Unipolar: – 1 process divides into 2 branches, which function as a single axon 1 branch (peripheral process) associated with dendrites Other branch (central process) enters brain or spinal cord
Structural Differences, cont….. 3.Multipolar: – Many processes arising from cell body: 1 axon Many dendrites – Most neurons whose cell bodies lie in the brain or spinal cord are multipolar. Direction of impulse is ALWAYS from dendrites to axon.
Functional Differences 1.Sensory (afferent) neurons – From peripheral body parts to the brain or spinal cord – Have specialized receptor ends at the tips of their dendrites OR – Dendrites closely associated with receptor cells in the skin or sensory organs. – Most are unipolar, but some are bipolar.
Functional Differences, cont….. 2.Interneurons (association or internuncial neurons) – Lie entirely in the brain or spinal cord – Multipolar and link other neurons – Transmit impulses from one part of the brain or spinal cord to another 3.Motor (efferent) neurons – Multipolar – Carry nerve impulses from brain or spinal cord to effectors – Stimulate muscles or glands
Copy Diagram on Whiteboard 1.Identify the direction of nerve impulse. 2.How can you tell the direction? 3.Label all dendrites, cell bodies, and axons. 4.Label each nerve as either sensory neuron, interneuron, or motor neuron. 5.Color code the CNS and PNS portions of the pathway.
Reflex Arcs Nerve impulse pathways that are responsible for involuntary actions Look like the pathway you drew and labeled: Receptor to Sensory neuron to (optional step) Interneurons in the CNS (a reflex center) to Motor neurons to Effector
Reflexes Automatic subconscious responses to changes within or outside the body: – Maintain homoestasis: blood pressure, heart rate, respirations, digestion, temperature – Automatic actions: swallowing, coughing, sneezing, vomiting
2 Examples of Types of Reflexes (?) 1.Knee-jerk reflex (patellar tendon reflex) – Employs only 2 neurons: sensory neuron communicating directly with a motor neuron 2.Withdrawal reflex: – A response to painful stimuli – Sensory neuron takes impulse to interneurons in the spinal cord reflex center, where it is transmitted to motor neurons. – Other interneurons carry impulses to the brain for processing of the experience and pain.
Meninges Membranes between the bone and soft tissues of the nervous system Function: ? 3 layers: Orange analogy 1.Dura mater 2.Arachnoid mater 3.Pia mater – Meningitis (?)
Dura Mater Outermost layer Contains many blood vessels and nerves Attaches to the inside of the cranial cavity and forms the internal periosteum (???) of the surrounding skull bones Forms partitions between lobes of the brain Continues into vertebral canal Terminates as a blind sac below the end of the spinal cord
Arachnoid Mater Thin, weblike membrane located between dura and pia maters Lacks blood vessels Spreads over brain and spinal cord, but does not dip into grooves and depressions on their surfaces
Pia Mater Cerebrospinal fluid (CSF) – clear, watery fluid that fills space between arachnoid and pia maters Pia mater – very thin and contains many nerves and blood vessels that nourish cells of the brain and spinal cord Hugs surfaces and follows all irregular contours of brain and spinal cord Subdural hematoma (?)
Review List and describe the 3 layers of the meninges.
Spinal Cord Slender nerve column that passes downward from the brain into the vertebral canal Starts at the foramen magnum and ends between first and second lumbar vertebrae
Structure of Spinal Cord 31 segments that each give rise to a pair of spinal nerves
Functions of the Spinal Cord What do you think would be the functions of the spinal cord? 1.Conducting nerve impulses 2.Serving as a center for spinal reflexes Nerve tracts (major nerve pathways) of the spinal cord are made up of axons that provide 2-way communication between brain and body parts: 1.Ascending tracts - sensory information to brain 2.Descending tracts – motor impulses from brain
Brain About 100 billion multipolar neurons 3 major portions: – Cerebrum Largest part Contains nerve centers associated with sensory and motor functions Provides higher mental functions, including memory and reasoning – Cerebellum - includes centers that coordinate voluntary movements – Brain stem – Connects parts of the nervous system (???) Regulates some visceral (???) activities
Cerebrum Cerebral hemispheres: 2 large, mirror-image halves Corpus callosum: deep bridge of nerve fibers that connect the cerebral hemispheres Surface of the cerebrum has: – Ridges: convolutions – Grooves: Shallow grooves: sulci (sulcus, singular) – separates lobes Deep Grooves: fissures – Longitudinal fissure – separates cerebral hemispheres – Transverse fissure - separates cerebrum and cerebellum
Locations and Boundaries of the Lobes of the Cerebral Hemisphere LobeLocationBoundaries Use textbook, pp to complete the table below.
Functional Regions of the Cerebrum 1.Complete graphic organizer. 2.Color-code and label diagram of association areas of the brain to correspond to your graphic organizer.
Hemisphere Dominance Right-Left Brain Test The dominant hemisphere controls the ability to use and understand language. Which hemisphere do you think is dominant in most of the population? Broca’s area (???) in the dominant hemisphere controls the muscles used in speaking.
Hemisphere Functions Dominant HemisphereNon-dominant Hemisphere Language-related activities: reading, writing, speaking Nonverbal functions: 1. Motor tasks requiring orientation of body in space Complex intellectual functions requiring verbal, analytical, and computational skills 2. Recognition and understanding of musical patterns 3. Nonverbal visual experiences
Corpus Callosum (???) and Hemisphere Dominance What is it? Nerve fibers connecting the 2 cerebral hemispheres Functions: – Allows the dominant hemisphere to control the motor cortex of the non-dominant hemisphere. – Transfers info received by the non-dominant hemisphere to the dominant hemisphere for use in decision-making.
Ventricles and CSF Ventricles: – interconnected cavities within the cerebral hemispheres and brain stem – contain CSF Choroid plexuses: tiny, reddish, cauliflower- like masses of specialized capillaries from the pia mater that secrete CSF into the ventricles Infections, tumors, blood clots can block the flow of CSF and increase intracranial pressure.
Ventricles and CSF
Diencephalon Located between the cerebral hemispheres and above the midbrain Contains: – Thalamus – Hypothalamus – Optic tracts and optic chiasma – formed by crossing of optic nerves – Infundibulum – attaches to pituitary gland – Posterior pituitary gland – hangs from floor of hypothalamus – Pineal gland – attached to upper diencephalon
Diencephalon Thalamus – receives all sensory input, EXCEPT smell, and sends them to proper region of cerebral cortex Hypothalamus – maintains homeostasis by regulating: 1.Heart rate 2.Blood pressure 3.Body temperature 4.Water and electrolyte balance 5.Hunger control and body weight 6.Movements and secretions of stomach and intestines 7.Neurosecretory substances that stimulate the pituitary gland 8.Sleep and wakefulness
Brain Stem Connects _______ to _______. Three sections: 1.Midbrain 2.Pons 3.Medulla oblongata 1.Midbrain – Between diencephalon and pons – Contains some visual and auditory reflex centers
Brain Stem 2. Pons – Rounded bulge on the underside of the brain stem, between midbrain and medulla oblongata – Relays impulses from medulla oblongata to cerebrum – Transmits impulses from cerebrum to cerebellum – Relays sensory impulses from peripheral nerves to higher brain centers – Helps regulate breathing
Brain Stem 3. Medulla oblongata – Extends from pons to foramen magnum – All ascending and descending nerve fibers must pass though – Control of visceral activities: 1.Cardiac center – heart rate 2.Vasomotor center – constriction and dilation of blood vessels to control blood pressure 3.Respiratory center – regulates rate, rhythm, and depth of breathing
Cerebellum Located below the occipital lobes of the cerebrum and posterior to the pons and medulla oblongata Like cerebrum, has two hemispheres, connected by a structure called the vermis.
Cerebellum Communicates with other parts of the CNS by 3 nerve tracts (cerebellar peduncles): 1.Inferior peduncles: receives sensory info about position of body parts 2.Middle peduncles: signals from cerebrum to cerebellum about desired position of limbs 3.Superior peduncles: takes correcting info from cerebellum to midbrain
Functions of Cerebellum Based on the previous slide, what do you think are the main functions of the cerebellum? Answer: – Reflex center for integrating sensory info concerning body positioning and coordination – Helps maintain posture What do you think damage to the cerebellum would cause?
Peripheral Nervous System Includes: 1.Cranial nerves 2.Spinal nerves Can also be divided into: 1.Somatic nervous system – controls conscious activities 2.Autonomic nervous system – controls unconscious activities
Cranial Nerves Where would these originate? 12 pairs – 1 st pair originates in the cerebrum – The rest originate from the brain stem
Cranial Nerves, continued….. 1.Olfactory nerves (I) 2.Optic nerves (II) 3.Oculomotor nerves (III) 4.Trochlear nerves (IV) – smallest; takes impulses to a muscle that moves the eye 5.Trigeminal nerves (V) – largest cranial nerves 1.Ophthalmic division – sensory info from eyes 2.Maxillary division – sensory info from upper mouth 3.Mandibular division – sensory info from scalp behind ears and lower mouth
Cranial Nerves, continued….. 6.Abducens nerves (VI) – small; motor impulses to move eye 7.Facial nerves (VII) – 1.Sensory associated with taste receptors 2.Motor impulses to facial muscles and tear glands and salivary glands 8.Vestibulocochlear nerves (VIII) – inner ear 1.Vestibular branch – maintaining balance 2.Cochlear branch - hearing
Cranial Nerves, continued….. 9.Glossopharyngeal nerves (IX) – tongue and pharynx; swallowing 10. Vagus nerves (X) – 1.Larynx muscles associated with speech and swallowing 2.Supplies muscles of the heart and smooth muscles and glands in thorax and abdomen – Vasovagal response
Cranial Nerves, continued… Accessory nerves (XI) – originate in the medulla oblongata AND spinal cord, so has cranial AND spinal branches 1.Cranial branches – join a vagus nerve and carry impulses to muscles of soft palate, pharynx, and larynx 2.Spinal branches – motor impulses to trapezius and sternocleidomastoid muscles 12. Hypoglossal nerves (XII) – motor impulses to tongue
Spinal Nerves Thirty-one pairs providing 2-way communication between spinal cord and parts of upper and lower limbs, neck, and trunk Divided into: 1.Cervical nerves 2.Thoracic nerves 3.Lumbar nerves 4.Sacral nerves 5.Coccygeal nerves – Naming and how many of each????
Autonomic Nervous System Two divisions: – Sympathetic division – prepares body for stressful situations – Parasympathetic division Most active under ordinary conditions Counterbalances sympathetic division
Cranial Nerves Mnemonic Devices Naming: O! O! O! There’s The Abercrombie and Fitch. Very Gorgeous and Very Adorable! Hot! Type of Nerve: Some Say Money Matters, But My Brother Says Big Boobs Matter More.