* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch. 7 - Nervous System
Neuropsychology wikipedia , lookup
Human brain wikipedia , lookup
Cognitive neuroscience wikipedia , lookup
Embodied cognitive science wikipedia , lookup
Biological neuron model wikipedia , lookup
Holonomic brain theory wikipedia , lookup
Single-unit recording wikipedia , lookup
Haemodynamic response wikipedia , lookup
Sensory substitution wikipedia , lookup
Embodied language processing wikipedia , lookup
Neuroplasticity wikipedia , lookup
Metastability in the brain wikipedia , lookup
Caridoid escape reaction wikipedia , lookup
Optogenetics wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Synaptogenesis wikipedia , lookup
Synaptic gating wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Central pattern generator wikipedia , lookup
Neural engineering wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Development of the nervous system wikipedia , lookup
Nervous system network models wikipedia , lookup
Evoked potential wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Microneurography wikipedia , lookup
Neuroregeneration wikipedia , lookup
Circumventricular organs wikipedia , lookup
Chapter 7 The nervous system allows the body to detect, interpret and respond to stimuli. ◦ A stimulus is any change in the external or internal environment. Functions of the Nervous System 1. Sensory input To monitor changes occurring inside and outside the body using sensory receptors 2. Integration To process and interpret sensory input 3. Motor output To produce a response, if needed, that activates muscles or glands (effectors) Organization of the Nervous System • Two main divisions: • Central nervous system (CNS) • Brain • Spinal cord • Peripheral nervous system (PNS) • Nerves outside the brain and spinal cord Organization of the Nervous System • Nervous tissue is made up of neuroglial (supporting ) cells and neurons. • Neuroglial cells outnumber neurons. • Neuroglial cells do not conduct impulses; neurons do. • Neuroglial cells generally support, insulate and protect delicate neurons. • Neuroglial cells are capable of dividing; neurons are not. Supporting Cells Neurons • Neurons = nerve cells • • Specialized to transmit messages (impulses) Major regions of neurons: • Cell body – nucleus and metabolic center of the cell • Processes – fibers that extend from the cell body • Dendrites – carry impulses towards the cell body • Axon – carries impulse away from the cell body Neurons Neurons Myelin sheath – fatty material surrounding axons produced by Schwann cells Insulates axons Speeds up transmission Classification of Neurons Sensory (afferent) neurons Carry impulses from sensory receptors to the CNS Motor (efferent) neurons Carry impulses from the CNS to muscles or glands (effectors) Interneurons (associative neurons) Connect sensory and motor neurons Classification of Neurons The Nerve Impulse The plasma membrane at rest is polarized (resting potential) Fewer positive ions are inside the cell than outside the cell Active transport by the sodium-potassium pump maintains this polarity Starting the Nerve Impulse • A stimulus depolarizes the neuron’s membrane • Sodium ions (Na+) rush inside the membrane • This initiates an impulse (action potential) in the neuron Continuing the Nerve Impulse The impulse continues to move toward the cell body Potassium ions rush out of the neuron which repolarizes the membrane The sodium-potassium pump then establishes the original polarity The Threshold A minimum stimulus (threshold) is needed to start an impulse If the threshold is met, a nerve impulse starts, and continues over the entire axon (all or none response) Impulses travel faster when fibers have a myelin sheath Neuron to Neuron Communication • Neurons do not touch each other because of a gap called the synapse. • Impulses cross the synapse with the help of chemicals called neurotransmitters. • Neurotransmitters released from the axon terminal diffuse across the synapse • The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter • An action potential (impulse) is started Neuron to Neuron Communication The Central Nervous System Brain and spinal cord Regions of the Brain Cerebral hemispheres Diencephalon Brain stem Cerebellum Cerebrum ◦ Voluntary activities (motor initiation), intelligence, learning, judgment, sensory interpretation ◦ Two hemispheres connected by the corpus callosum Right hemisphere controls the left side of the body and visa-versa ◦ Deep folds and grooves increase surface area Gray matter – outer layer of dense nerve cell bodies White matter – inner layer of myelinated nerve fibers Lobes of the Cerebrum Fissures (deep grooves) divide the cerebrum into lobes Surface lobes of the cerebrum Frontal lobe Parietal lobe Occipital lobe Temporal lobe Specialized Areas of the Cerebrum Primary sensory area (postcentral gyrus)– receives impulses from the body’s sensory receptors Primary motor area (precentral gyrus)– sends impulses to skeletal muscles Sensory and Motor Areas of the Cerebral Cortex Specialized Area of the Cerebrum Cerebral areas involved in special senses Broca’s area – speech Gustatory area - taste Visual area - sight Auditory area - hearing Olfactory area – smell Interpretation areas of the cerebrum Speech/language region Language comprehension region General interpretation area Specialized Area of the Cerebrum Two hemispheres with convoluted surfaces Provides involuntary coordination of body movements http://www.youtube.com/watch?feature=player_detailpage&v=F7Yw26zHoEw Sits on top of the brain stem Enclosed by the cerebral hemispheres Made of three parts Thalamus – sensory relay station Hypothalamus – controls hunger, thirst, fatigue, anger, temperature, coordinates with endocrine system Epithalamus – pineal gland and choroid plexus (forms cerebrospinal fluid) • Attaches to the spinal cord • Controls vital functions – blood pressure, heart rate, breathing, swallowing, vomiting • Parts of the brain stem • Midbrain • Pons • Medulla oblongata Scalp and skin Skull and vertebral column Meninges Cerebrospinal fluid (CSF) Blood-brain barrier Skin of scalp Periosteum Bone of skull Superior sagittal sinus Subdural space Subarachnoid space Periosteal Meningeal Dura mater Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) (a) Figure 7.17a Occipital lobe Tentorium cerebelli Cerebellum Arachnoid mater over medulla oblongata Skull Scalp Superior sagittal sinus Dura mater Transverse sinus Temporal bone (b) Figure 7.17b Similar to blood plasma composition Formed by the choroid plexus ◦ Choroid plexuses–capillaries in the ventricles of the brain Forms a watery cushion to protect the brain Circulated in arachnoid space, ventricles, and central canal of the spinal cord Lateral ventricle Anterior horn Septum pellucidum Interventricular foramen Inferior horn Third ventricle Lateral aperture Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view Figure 7.18a Lateral ventricle Anterior horn Posterior horn Interventricular foramen Third ventricle Inferior horn Cerebral aqueduct Median aperture Fourth ventricle Lateral aperture Central canal (b) Left lateral view Figure 7.18b Includes the least permeable capillaries of the body Excludes many potentially harmful substances Useless as a barrier against some substances ◦ ◦ ◦ ◦ ◦ Fats and fat soluble molecules Respiratory gases Alcohol Nicotine Anesthesia Traumatic Brain Injuries (TBI) Concussion Slight or mild brain injury Bleeding & tearing of nerve fibers Recovery likely with some memory loss Contusion A more severe TBI Nervous tissue destruction occurs Nervous tissue does not regenerate Cerebral edema Swelling from the inflammatory response May compress and kill brain tissue Cerebrovascular Accident (CVA) Commonly called a stroke The result of a ruptured blood vessel supplying a region of the brain Brain tissue supplied with oxygen from that blood source dies Loss of some functions or death may result Alzheimer’s Disease Progressive degenerative brain disease Mostly seen in the elderly, but may begin in middle age Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons Victims experience memory loss, irritability, confusion and ultimately, hallucinations and death Twelve pairs of nerves that mostly serve the head and neck Only the pair of vagus nerves extend to thoracic and abdominal cavities Most are mixed nerves, but three are sensory only I Olfactory nerve—sensory for smell II Optic nerve—sensory for vision III Oculomotor nerve—motor fibers to eye muscles IV Trochlear—motor fiber to one eye muscle V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles VI Abducens nerve—motor fibers to eye muscles VII Facial nerve—sensory for taste; motor fibers to the face VIII Vestibulocochlear nerve—sensory for balance and hearing IX Glossopharyngeal nerve—sensory for taste; motor fibers to the pharynx X Vagus nerves—sensory and motor fibers for pharynx, larynx, and viscera XI Accessory nerve—motor fibers to neck and upper back XII Hypoglossal nerve—motor fibers to tongue III Oculomotor IV Trochlear VI Abducens I Olfactory II Optic V Trigeminal V Trigeminal VII Facial Vestibular branch Cochlear branch VIII Vestibulocochlear X Vagus IX Glossopharyngeal XII Hypoglossal XI Accessory Figure 7.24 Oh – Olfactory Oh – Optic Oh – Oculomotor To – Trochlear Touch – Trigeminal And – Abducens Feel – Facial Very – Vestibulocochlear Green – Glossopharyngeal Vegetables – Vagus Ah – Accessory Ha – Hypoglossal • • • • • • • Extension of brain stem Controls reflexes Surrounded by meninges (membranes) Central canal is filled with spinal fluid Protected by vertebrae. Gray matter – mostly cell bodies White matter – myelinated cell fibers Spinal Cord Extends from the medulla oblongata to the region of T12 Below T12 is the cauda equina (a collection of spinal nerves) Enlargements occur in the cervical and lumbar regions Spinal Cord Central canal filled with cerebrospinal fluid The Reflex Arc Reflex – rapid, predictable, and involuntary responses to stimuli Reflex arc – direct route from a sensory neuron, to a spinal cord interneuron, to an effector No brain involvement Peripheral Nervous System Nerves and ganglia outside the central nervous system A nerve consists of neuron fibers bundled by connective tissue There are twelve pairs of cranial nerves and 31 pairs of spinal nerves. Somatic nerves control voluntary functions and autonomic nerves control involuntary functions A nerve has layers of connective tissue. The endoneurium is a delicate connective tissue wrapping around each fiber. The perineurium is a coarser wrapping around a bundle of fibers (fascicle). The epineuriun is a tough connective tissue wrapping around all the fascicles. Nerves may contain just sensory neurons, just motor neurons, or both (mixed). There is a pair of spinal nerves at the level of each vertebrae. Formed by the combination of the ventral and dorsal roots of the spinal cord Named for the region from which they arise Plexus–networks of nerves serving motor and sensory needs of the limbs Form from ventral rami of spinal nerves in the cervical, lumbar, and sacral regions Four plexuses: ◦ ◦ ◦ ◦ Cervical Brachial Lumbar Sacral Cervical nerves Thoracic nerves Lumbar nerves Sacral nerves C1 2 3 4 5 6 7 8 T1 2 3 4 5 6 7 8 9 10 11 Ventral rami form cervical plexus (C1 – C5) Ventral rami form brachial plexus (C5 – C8; T1) No plexus formed (intercostal nerves) (T1 – T12) 12 L1 2 3 4 Ventral rami form lumbar plexus (L1 – L4) 5 (a) S1 2 3 4 Ventral rami form sacral plexus (L4 – L5; S1 – S4) Figure 7.25a Motor subdivision of the PNS ◦ Consists only of motor nerves Also known as the involuntary nervous system ◦ Regulates activities of cardiac and smooth muscles and glands Two subdivisions ◦ Sympathetic division ◦ Parasympathetic division Sympathetic—“fight or flight” ◦ Response to unusual stimulus ◦ Takes over to increase activities ◦ Remember as the “E” division Exercise, excitement, emergency, and embarrassment Parasympathetic—“housekeeping” activites ◦ Conserves energy ◦ Maintains daily necessary body functions ◦ Remember as the “D” division digestion, defecation, and diuresis Anatomy of the Autonomic Nervous System Comparison of Somatic and Autonomic Nervous Systems